R22 & R44 blade delamination [Archive]

imabell

20th Apr 2006, 22:46

slow rotor, the doubler has delaminated it is not a crack it is a delamination.

i have all the facts, i have all the proper information, this is not hearsay i have seen the blade.

bushbandit, i don't know how much load you guys put on blades and machines but i have seen film of some obviously heavy loads slingshotted of mountains and carried out by some mountain pilots in new zealand.

i would have to be reasonably sure that testing of the loads to breaking point of any helicopter rotor blade would be at least to double the weight of the machine. i am reasonably sure that any manufacturer would not manufacture blades that are rated to within a couple of kilos over max gross. the margin for safety has to be large or you would not have the confidence to fly. i am sure even in the new zealand alps your robbies cannot lift enough to break a blade. (i have flown there).

there are repair allowances for the doublers on 47's and jet rangers by cutting the doubler back beyond the debonded section and feathered back to the blade skin. this is what robinson is now looking at trying (experimenting).

twinhueyman, i'm with you, if the engineer says it's ok, just keep an eye on it i'll go flying. the problem here is nobody is saying anything and the engineers are grounding helicopters.

bellfest

21st Apr 2006, 01:40

imabell
Anyone who has had anything to do with R22's in a working environment (which I'm sure you have) knows what disc loading they are capable of.
If there is some type of fault with the glue or the bonding process at manufacture a flying school would be the perfect place to test it out. Doing autos all the time the machine would be subject to the most demanding aspect in that area (High coning angle/low RRPM).
There is overspeed limits, MTOW limits but there is no coning angle limit at the bottom of an auto. I would guess that it is assumed that if you exceed the coning angle limit your attention would be more focused on the bent skids and wrinkled firewall.
As far as lifting too much goes I would tend to think that is a load of crap. An R22 won't get off the ground if its AUW is causing excessive coning. They would be subject to such things anyway in the form of G loading in certain manouvers.
Though other aircraft do debond/delaminate/come unstuck/unglue/f*%$#n break in that area they appear to have a bit more reliance when it comes to the integrity of the blade. ie B47.
I am sure that you would agree that the R22 is a sensational machine but these things do turn up on them from time to time and I would be more enclined to think that this is some type of manufacturing anomally. I hope for your sake Frank sees it that way.

imabell

21st Apr 2006, 02:17

yes bellfest to all of those things.

having a blade delaminate and talking about it is one thing but the repercussions involved with multiple occurrences is our major worry. we operate three robbies, one with a delamination, and three bells, but you have to imagine the plight of the single and multiple robbie operator whoe suffers this problem, the time frame to fix it, right at the begginning of the mustering season.

there are abot 200 machines used in mustering and every one of the owners has their collective fingers crossed that this does not escalate.

i have since learnt of another blade that has come unstuck in australia that makes six.

i also have heard a rumour that there have been instances at the factory before delivery but i cannot substantiate this.

topendtorque

21st Apr 2006, 04:43

407
That looks like only half the pic, what did the drag brace area look like?
Heard of an incident many moons ago from a company in east OZ. They had a fruit loop (aren’t we all?) driving a 12E in mustering mode. Hero hits a tree and did more damage than your pic and decided to hack saw the offending bent areas off, about nine inches or so. The story of course does not stop there, our hero turned engineer all of sudden and reckons that he needs to balance the system so cuts the same amount off of the other but so far unblemished blade and flies around for another fifty or so hours until the next 100. Rumour has it that our hero left his place of employ on foot, at a very fast clip, without even picking up his check when confronted by the boss.

Twin huey
I am with you too, if your gut feeling is nogo, then I don’t go, contracts don’t pay for expensive holes in the ground.

Acsj
You’re onto it, but the price of fuel gees every drop saved counts, or maybe you could suggest to Frank he could use a scaled model of one of those two mentioned types of blades on the R22. Hmmmm an 269 series blade onto the R22 series, given the history of why-for the R22, that would stir a real ruckus in Torrance HQ!!

Slowrotor
From the MM sect 9.130 h) 1. “Blades must be tap tested using a 1965 (or later US quarter in good condition.” (Really, yep a bloody 1965 quater! I read that a few times to make sure. Did HAA hang that one on him and did one qrtr each get sent with all of the exported models?)

Allowable; “no single void larger than .10 square inch.” I read that as 1 inch long a tenth of an inch deep. That is not much. I could easily stand to be corrected!
Section 9.130 is called up by section 2.410 Item 13. (Part of the 100 hourly)

Make sure that no-one does a tap test until referring to the diagrams or they are well briefed as to where the bonded areas are. If they tap outside a bonded area they’re liable to U.S. the blade. BE CAREFUL THEY ARE FRAGILE.

So far I am hearing that they are all early production blades but that is being checked.

No doubt Torrance HQ is working around the clock on this, after all the viability of 4,000 helicopters hangs on a viable operational outcome quite soon.

Not to mention that a multitude of operators in North Australia who have been delayed on their mustering season start because of so much cyclonic activity and the entire north Australian cattle industry who also depend on these helicopters.

If these defects have been known for a while one might have thought that there could/should be a daily inspection both visual and tap test required by now by Robinson and or CASA, FAA and NZ CAA. That is assuming all authorities received Defect reports!

There is of course already a requirement in the POH to visually check the blades for cracks; however a special purpose AD or SB would be a good idea at least to clarify –is it or isn’t it OK- do you know????

How many people really check for cracks when doing a daily, or even venture up toward the head? There are only three things in a daily that will kill you if you miss them no matter how big or small the aircraft.

They are the three C’s. 1. CRACK, 2. CHAFING, 3 CORROSION and the little S, for Security.

Re cost, the MM states also that; “Voids or debonds are NOT field repairable.”

This means return to factory, it should mean return to approved service centre for approved repair. The time and cost to ship blades across a continent and then the Pacific Ocean and back again all without being damaged would be monumental. If necessary it would be much better and cheaper to have a Robinson senior technician attend and supervise these repairs at some of the major service centres.

IMABELL paints a horrible financial picture if the blade security is not attended to quickly. Fair enough!

bellfest

21st Apr 2006, 07:45

It does have the potential to disrupt a big industry particularly considering that all the Sidney Kidmans' are on their heals and ready to race after what has been a pleasant reprieve after the last 8 years or so. A wet season like this will be beneficial not only this year but for a few to come also.
Considering the repurcussions of a "grounding" I don't think that will happen. It would be more likely that a SB will be issued stating additional attention to the blade roots during daily inspections with diagrams and measurements etc. followed up by an AD from CASA somewhere in the second round!
It could turn to **** for a few that actually find a delam.
Robinson really need to sort their blade issues out.
You might have to ferry a few of those 47's north and get in amongst it old school if the worst were to happen.

topendtorque
If that 12E story is true than old mate is the stupidest and most precise man with a hacksaw I have ever heard of. Not to mention fit, with f$#@en good blades.

topendtorque

21st Apr 2006, 11:56

Bellfest
he was one strange character, history doesn't say how many hack saw blades. I have had a go at 47 blades and gave up up in favor of an electric driven power hacksaw. where the gent is now I don't know, at other times he had a penchant for flying around the outback with a 44 gallon drum on one litter half full of rocks and geiger counters and on the other, one half full of fuel, the cabin had his gear, several drums of oil and him -- usually giggling!!
True story. A happy chappy. and people ask on these threads about mustering jobs!!!

Let's face it the 12E was built like the proverbial, i've only a few hours in them but you're right the paddles should have sailed off into the blue for sure. ask mr Imabell about him, i reckon he would have known him-- and his previous employers.

mr selfish
Yes you are spot on, we should not talk about one of their AD's on the same machine last episode should we. However insurance rules the roost and sooner rather than later those turkeys as well had better start playing the game.

3 ROMEO MIKE

21st Apr 2006, 18:22

Someone could become very wealthy if they designed an articulating rotor
head and composite blades to retrofit the R22. Lord knows Frank and his
clan cannot.

robsrich

21st Apr 2006, 21:59

I help run one of the Robbie safety courses in Oz and NZ. One thing I have noticed over the past 13 years (1,500 studnets) is that we are all reluctant to report defects.

Being out in the bush, or away from our friendly man with the spanners in the workshop. Maybe we don't know how to?

Sometimes a class will tell us all about a series of problems, unknown away from their hangar floor. If CASA, CAA NZ, ATSB, Robinson, etc are not told about bugs that appear from time to time, then we tend to find out in a fatal.

The saga of the R22 blade failures was known well in advance, it took some fatals to bring it into focus. No one talked to each other, and the vital clues slipped away as simply a "one off" fault.

Half the Oz fleet are Robinsons. Mustering drivers fly more hours than anyone else. Beef prices have never been better, according to some, so we cannot afford to have our fleet grounded just as the mustering seasons starts, being delayed by the four cyclones.

I congratule imabell for bringing this to our attention. If any one else is finding a recurring problem, just PM me and I will try and pass it onto to someone who may be able to help.

We must work together, there are too many jobs at risk - let alone lives. Apart from my these problems, the Robbies are very safe if flown to their limits - and no more!

Maybe whacking a 360 cubic inch (180HP) into the airframe to relace the 320 (160HP) rubber band without beefing up the airframe has caused these problems?

It is even more importnat than ever to not overload the hard working and reliable machine.

Thanks again to imabell.

bellfest

21st Apr 2006, 23:38

The blades should be designed to take anything that aircraft weight can throw at them to be able to cope with aerodynamic loads.
Would it be fair to say that if an engine was to cause delamination due to too much torque it would be a very impressive machine performance wise? They are pretty good but not that good.
With the R22 teetering and flappimg head this would be reduced even more so.
You could suspect spindell damage as operational but not delam. It is a very sterile procedure and it wouldn't take a lot to have in inferior batch
Now, flapping in the breeze while shutdown could be a contributor. The stress in that particular area may be more so without any centrifugal force. Much more likely than overpitching I would think.

robsrich

22nd Apr 2006, 00:13

You are spot on.

Since the R22 HP model took the power to 160 HP from 150 HP the weight was kept at 1300 lbs. Aim was to get better high altitude performance, not to overboost or go out too heavy.

As there was a need to carry a bit more, the Alpha went to 1370 lbs. Limit was still 124 HP.

The limit since the Beta was introduced has always been 131 HP for takeoff - limit five minutes.

Then max cruise using 124 HP.

The bigger 180 HP engine was to provide even better high altitude performance. The power falls away as you climb up to a mountain top.

It is a derated engine by RPM and MAP. The placard says it all!

I was watching that now famous NZ video on the R22 and noted the powere settings recorded by the camera. Bit scary I thought.

All we have to do is keep within the limits.

The old farts who say "if it can hover" it is OK. Do they really understand that metal has memory?

One industry icon recently told me that he gets going by turning off the governor, overspeeding the rotor, overboosting MAP as it struggles through TL, then governor back on.

When asked how heavy he was - with two big guys, full fuel, a rifle, ammo, seats full, etc.

His answer said it all: "Dunno"

bellfest

26th Apr 2006, 23:52

imabell
Could you keep me posted on the outcome of this? I would be very interested in what type of support you get from Robinson over this.
Cheers

imabell

27th Apr 2006, 00:24

have no fear, we are waiting for an answer from anyone and we will let you know.

discobeast

27th Apr 2006, 07:41

imabell,

was the blade in the pic you posted a dash2 or dash4 blade?

cheers!

topendtorque

27th Apr 2006, 07:47

Dash four!!

canterbury crusader

27th Apr 2006, 08:36

If a heavy aircraft puts undue stress on the blades, what happens when the pilot does a steep turn - 2g, or even more. I am yet to see a flight manual (that I can remember) having a positive g limit for helicopters. 50 kg overloaded is nothing compared to a 1450 kg jetranger pulling 2.5g - 3625 kg and more.

mark_

27th Apr 2006, 16:51

Can someone please point me in the right direction of the infamous video to which Robsrich is referring in his above post?

regards,
Mark

George Semel

27th Apr 2006, 21:36

[QUOTE=TwinHueyMan]We get "delamination" at the roots of the blades on our Blackhawks fairly frequently (right at the very inside of the blade, where the root meets the blade for the first time) -- the prop and rotor guys put a bit of pro-seal and spray-paint on it and call it fixed until it shows up again.

Gee's I didn't know that Pro Seal could be used to fix rotor blades. Sort of like the hot glue gun fix an old employer use to do on his run out rotor blades. I myself would be real reluctant to fly any machine so repaired. Band aid fixes will kill you if you give ithem a chance to. What are the Tech rep's saying is the problem and the fix?

I don't have anytime in the R-22 to speak of, it seems to me that this has been an on going problem for the Robinson. Seems to me that its an very expensive helicotper for what you really get.

topendtorque

27th Apr 2006, 22:48

you'll find the video here www.videosouth.com it is titled 'the robinson R22.'

I have no pecuniary interest in the outfit. you will find the vis is excellent.

The aurals are also 'very' interesting, like -'its got 180 horsepower!!'

George S
Yes there was a major problem with the original blades;
-1's- low inertia and a quality control prob which snuffed out a swedish guy that trained with me at Air-Log;

-2's had better inertia- well they did to any of us that had flown -1's where it was reef at the bottom and whoosh became whhhhoooooshhh in a about three revs. -2's also had a creeping corrosion prob interrelated with a structure prob but really most of the failures they had would not have happened if the players had stuck to the rules;

-3's never hit the stands;

-4's that we now have are showing a debonding at the outboard end of the doubler. as per imabell's original post

so far our info is that there are 4 in OZ, 2 in US (one from canada) and a suggestion of 2 from NZ. serial #s as far as we know in the 1000 to 1100 and age from 330 to 780hrs and yes, it may end up costing several arms and legs.

cows'n'fish

28th Apr 2006, 18:57

As a former mustering pilot with a few hours in 22's I was quite sad to hear the "rumour" that Frank is not going to make the 22 any more. Apparently he is going to concentrate on the 44's and the elusive R66 (turbine). Has anyone else heard this? I know someone who is going to Torrance soon and says he will find out, i'll let you know what they say....

Heli-kiwi

28th Apr 2006, 22:26

Yes I did a Robbie saftey course with Tim Tucker (R22 test pilot) and he said that the factory has an Airframe that they are testing but are not happy with the powerplant, So Frank has given Allison/Rolls Royce a lot of money to come up with a hybrid C20/C30 engine (C25?)to power the beasty, He is also in negotiations with Mercedes Benz about designing a diesel specifically for the R66 as an option.
By the way that saftey course was the best $600 i've spent on flying, But if you do it make sure it is taken by a factory test pilot like Tim - I learnt so much about the designs of other types as well :ok:

imabell

28th Apr 2006, 22:40

casa has looked at one of the blades now and tells us that not only has it delaminated on the bottom doubler but on the top as well even though we could not see it.

there has been only one defect report submitted to casa even though there are several instances of similar delamination. i have no idea why this is not reported by the relevant engineers even though the blades have been sent back to the factory for replacement.

casa is going to write to all operatotrs and explain the situation and get everyone to inspect their blades. we don't know if it will become an ad.

maybe it was one batch, maybe, just maybe. do they make batches?????

robsrich

28th Apr 2006, 23:12

imabell is spot on here!

As per my post of 22 Apr - you must make sure the "system" is advised.

Then the regulators and the makers can see what is actually happening in the fleet.

Better paperwork now, than a funeral later!

Help the system to help you.

ascj

28th Apr 2006, 23:37

Who would buy an r66 when after twenty somthing years and 4000 r22's they still can't get the blades right.:eek:

RotorSwede

13th May 2006, 19:31

Just thought I'd bring this topic up again, see if there is anything new on this important issue ... any more cases, has RHC or any national CAA made any statements ?

robsrich

13th May 2006, 21:25

RotorSwede,

I was in NZ a few days ago, doing a Robbie course. Had a chance to listen to an engineer give an hour going over both the R22 and R44.

He was a great teacher, as he had many years of experience with Robbies.

When asked about the delaminations, the NZ industry has not seen any major problems, it seem the R44 has had a couple.

It may not be a serious problem, but unless the world Robinson community reports them to Frank and his team, and your local regulator, we will never know.

So please put pen to paper.....

The previous blade problems were showing up long before "the system" became aware. Again, the need to do the right thing and tell the right people.

As an aside, the new blades seemed to be well excepted, but the thinner skin was easily damaged, and bush pilots were now keeping well away from anthing that could fly up into the rotor.

The engineer showed us blade sections of old and new. Tapping with a small coin, it is very obvious the new blades are really "soft" and easily dented.

But despite these minor problems, the Robbies are very safe when you spend hours on international data. The older types have a much greater loss and fatal rate, according to ATSB stuff from OZ.

If anyone wants a copy of the data, just PM me. It is interesting reading.

Fly with a smile ........

imabell

17th May 2006, 05:54

here we go again,

one blade delamination in the territory and two more in western australia in the last three weeks.

all of these blades are in the 300 to 400 hours in service.

trying to get more photos and more specific details.

RotorSwede

17th May 2006, 07:58

To the ppl that have been long in the industry:
When would be the time for RHC to make some sort of official comment concearning this issue? If one would look back at the previous blade-issues with the RHC.
Is it still to many unknown parameters, or is it "strange" that there is no info either on their website or to customers or to national CAA.
Or is it not big enough?
Just concearned, I know one should read the statistics and so on, but this is starting to take the fun out of flying the R22. If you check the blades 100% visually before you take off and not fly for more than 2h in a row, can one be more sure that this **** won't happen during the time airborn? I would say the answer is "no", or ? How is one supposed to train for CPL with this in the back of ones head.
*sigh*
RS

robsrich

17th May 2006, 09:40

Imabell

Please keep these reports coming.

Hope the operators have told someone who can chase up the investigation stuff.

Thanks

tangovictor

17th May 2006, 10:44

please don't shoot the messenger, I read on a site once, which I will attempt to find, that the delamination problem is mainly located in Australia, the reason stated, was, due to hobbs being disconnected, services being forged, 1000 of hours being flown, by "ghost" pilots, all this in the severe environment, of scorching heat / dust etc, while mustering. Be interesting to see the delamination stats per country.

robsrich

17th May 2006, 21:43

Agree.

More research needed.

NZ being colder? May not have the alleged problem. But Oz heat, flies and more UV, seems to be getting a problem.

Reminder again - if you see problem tell the regulator via their whatever system to keep tabs.

Then we will al know the answer sooner.

imabell goodonya for chasing this up

headsethair

17th May 2006, 22:04

I find it amazing that light helicopters, where your life depends on correct data logging, have nothing more accurate than a Hobbs meter. And it's plainly obvious that this is easily corrupted.

Yet again, the age old problem of certification is probably causing loss of life. For sure, there are low cost electronic telemetry systems out there which can log the data accurately with no risk of corruption. But you're not allowed to fit them.

The temps in the outback of Oz are no different to the surface temps in some other locations on the planet. So, let's get real. This is a problem unique to the "operating environment" of Australia - and we need more data to ascertain if limits are being exceeded, hours ignored and paperwork forged or lacking.

RHC should insist that CASA force bush operators to fit telemetry for a trial period.

And then let's have it for the rest of the world. Because we'd all love to know what our hirers, instructors and students have been doing.......

tangovictor

17th May 2006, 23:39

Eventually I found the link, great read, from someone who obviously knows whats gone on ?
http://brumbyhelicopters.com.au/auspage1.htm

ascj

18th May 2006, 01:10

Tango Victor the older model blade problems probably had somthing to do with under recording of hours but these new blades haven't been around long enough for that to be the problem. It seems to be occuring at 300 to 400 hours of age.:uhoh:

that chinese fella

18th May 2006, 03:50

Having not long ago returned from RHC maintenance course it was highlighted that the -4 blades skins (stainless) are now only a third the thickness of earlier (aluminium) blades. (.008 -v- .025 thou).
This reduction in skin thickness is very evident in the markedly differing (less tolerant) damage limits with the new blades. A bit of 'Hangar rash' is now enough to render a blade scrap. Be careful and treat them with respect. RHC reported they are doing good trade in MR blade sales due to carelessness. :{

imabell

18th May 2006, 05:51

here are a few photos of the latest blades.

there seems to be an indentation near the doubler on the first pic as well as the crack, hasn't been ascertained what the cause is.

the severe ripples on the 63" station of both blades is also a mystery as there is no impact damage evident at all anywhere on the blades.

the delamination is hard to see in the photograph.on the orange upper section but is easy to see in real life.

these blades are outside the batch numbers of the original problem blades so the base is widening.

they are just over 300 hours in service so please this problem has nothing to do with high temperatures or over running times or flies. or misuse.

the fact is that contrary to some writers opinions mustering machines flown by experienced pilots (most are) do not pull heaps of power all day long playing silly buggers in the trees. most pilots use minimal power at slower speeds and get the optimum performance at low power settings. (i fly with these pilots regularly). no-one is in a hurry.:= := :ugh:

http://www.bluetonguehelicopters.com.au/pprune/del1.jpg

http://www.bluetonguehelicopters.com.au/pprune/del3.jpg

http://www.bluetonguehelicopters.com.au/pprune/del4.jpg

bladewashout

18th May 2006, 13:29

Really hard to see in the 1st and last pictures! If you get any that show it clearer, please put them up.

The ripples look downright wierd!

Anything that helps point to what we should be checking for every day is appreciated!

BW

AK22

18th May 2006, 13:56

Functional Description of a General Aviation Flight Event Recorder – Flight Minder.
A requirement / opportunity has been identified for improving safety and correctly allocating costs associated with operation of light aircraft and helicopters in the field of General Aviation.
Introduction
Without some form of basic "flight event" monitoring and recording mechanism, it is the responsibility of the pilot, to recognise and record all the events associated with a flight, some of which can affect the safety of the aircraft or the cost of the flight.
Such events may include the following, along with the time and location at which they occur :-
Engine start and stop
Taxiing start and stop
Take off / Landing
Very heavy landing
Engine over-speed (rotorcraft)
Rotor over-speed (rotorcraft)
An instrument has been developed specifically to identify and record such events. During development this instrument is has been referred to as “Flight Minder”.
Description of the Airborne Equipment
The airborne equipment comprises a small (140 x 90 x 40mm) rectangular module which houses a microprocessor based event recorder along with the associated sensors and interfaces. The module includes a non-volatile memory for storage of events, along with a “Smart” (memory) card reader / writer and an integral GPS receiver. An external “patch” antenna is required for the GPS receiver.
To simplify installation in the aircraft, electrical connections to the aircraft have been kept to a minimum. Installation in a fixed wing aircraft requires only a DC power connection via an approved circuit breaker and aircraft main switch. The airborne module will operate from 7 to 36 volts DC, and consumes an average of 100 milliamps at 12 volts.
Flight Events
Engine Start / Stop
The “engine running” condition is detected acoustically
Stationary /Taxiing / In Flight
Events related to aircraft speed, i.e. stationary, taxiing or “in flight”, are determined by an integral GPS module. Software routines within the microprocessor require that the aircraft speeds remains above or below the set thresholds for a given period of time, before recording a change of condition. GPS “Speed over the Ground” is used throughout, with no correction for wind speed being made.
Heavy Landing
Heavy landings are detected by an integral two axis accelerometer. The use of two axes allows the instrument to be mounted on either a horizontal or vertical surface. At “switch-on” the microprocessor determines which axis of the accelerometer is aligned vertically, and this axis is then used for measurement until the instrument is switched off. A “running average” of vertical acceleration is taken over several seconds. This average, plus a preset level, are used as a threshold against which to compare any sudden, large, transient changes in vertical acceleration. The level is chosen to represent a value which if exceeded would indicate that structural damage to the airframe may have occurred. For the accelerometer to provide reliable results, the Flight Minder must be securely attached to the aircraft.
Rotary Over Speeds
When installed within a helicopter, if the potentially dangerous conditions of engine or rotor over-speed are to be detected, then external, non contacting sensors are required to provide electrical impulses at a rate proportional to engine and rotor speed. Connection to these sensors is made via pins on the same connector as the power supply. A current limited supply of 12 volts DC for the sensors is also available on the same connector.
Data Recording
When any flight event is detected, the nature of the event, along with the time, date and location at which it occurred is stored as a record in an internal memory. The aircraft registration, Flight Minder ID, and if available pilot details are also appended to the record. The internal memory can store over 500 events, and will retain data after power has been removed from the instrument.
If a suitable “Smart” (memory) card has been inserted into the instrument, then events stored in the internal memory are also copied to the removable memory card as soon as possible.
The primary function of the removable memory card is as a medium by which recorded data relating to the flight can be transferred from the airborne instrument to ground based equipment for recording and further processing as required. A secondary function of the card is to provide details to the airborne instrument, relating to the flight. Such details may include the name of the pilot, the type of flight (dual / solo / instruction etc.) The removable memory card can also store over 500 events. It is envisaged that data would be transferred from the card to the ground based equipment at the end of each flight, or if more appropriate, at the end of each day. Records are not deleted from the internal memory, until they have been secured on the ground based equipment.
Depending on individual requirements, a single card can be used for the transfer of all records from the aircraft, or a separate card could be issued to each pilot. The latter method is preferred as this allows pilot details to be assigned to flight event records.
Ground Based Equipment
A suite of software has been developed to read and manipulate flight event records from the Smart Cards. This software is designed around the Microsoft Access database format.
Alan Kitching Electro-Technik
+44 1642 724932 [email protected]

slowrotor

18th May 2006, 14:56

Dave_Jackson

18th May 2006, 17:22

Speculation.

As slowrotor say, the two outside hinges of the tri-hinge hub should relieve a portion of the out-of-plane blade flexing and thereby allow for lighter/weaker blades.

I understand that the desire of a 2-blade rotor to flex in-plane is absorbed by the long mast. At certain RRPMs, could a resonance come about between the low inertia rotor and the engine that would increase the in-plane stresses?

Again, just speculation.

flimflam

18th May 2006, 20:19

The blade problems occur in just a few hundred hours leading me to suggest the problem is design. I think operation in turbulence is a problem.
Because the R-22 does not have lead/lag blade hinges. Normally a teetering head doesnt have lead/lag hinges, instead it is built heavy to absorb the lead/lag. The very lightly built R-22 has coning (flapping) hinges to relieve coning bending but nothing to relieve lead/lag stress resulting from the independent flapping in sharp turbulence.
Just my opinion on this rumor network. Until someone explains how the lead/lead hinges are not needed, that is what I think.
slowrotor
Lead/Lag hinges are not required because the two bladed design uses an underslung head. It is not 'built heavy' to absorb lead/lag. The coning hinges are not '(flapping hinges)'. A two bladed system with an underslung head Flaps about the teetering hinge and cones about the coning hinges. Lead/lag is compensated for by the underslung nature of the head.

ascj

18th May 2006, 22:54

AK22 the flight recorder sounds interesting, how expensive to puchase and install? Oh and what was that about a circuit breaker.

slowrotor

18th May 2006, 23:26

flimflam,
In a normal two blade teetering system like a Bell 47 or Hiller the blades are forced to flap as a unit. The hinges on a R-22 allow individual blades to flap alone when hitting a sharp gust. It has been known since Cierva invented the flapping hinge that a lead/lag hinge would be needed as well.(after he found his free to flap blades failed in lead/lag)
A hinge is a hinge no matter what it is called.
What prevents the R-22 "coning hinge" from working as a flapping hinge?

slowrotor

Big Foot

19th May 2006, 00:59

Has anybody heard what robinson is saying on these delaminations. I have been told they are saying that it is paint cracks and not debonding ,am unsure of how accurate this information is. I have seen in person the same as the pictures of the cracks at the doubler. I fly a lot of 22 hours this time of year. :ugh:

imabell

19th May 2006, 01:16

these photo's are of the blade off a raven 2 in new zealand. about 910 hours in service.
the chalk hatched lines show the extent of the delamination under the doubler.

http://www.bluetonguehelicopters.com.au/pprune/nz01.jpg

http://www.bluetonguehelicopters.com.au/pprune/nz02.jpg

flimflam, the robbie head may look like it is underslung but it does not have the ability to rock like a true underslung head that has a gymbal and a yoke.

the gymbal allows the head to flap and the yoke, attached to the gymbal by pillow blocks, allows the blades to rock, relieving all of the hunting stresses on the grips. an effective design feature for two bladed systems.

the robbie head does not have this feature.

to me it looks like the lead and lag, (hunting), stresses are still taken up by the blades and maybe the root cause of the problem.

bellfest

19th May 2006, 03:20

It could have something to do with the adhesion to the stainless as opposed to aluminium. I am sure if you got the microscope out there would be a lot less to grab a hold of.
Maybe these new paperweight blades can't be tied down with any tension.
I would bet my left nut that this is not operational:ooh:

topendtorque

19th May 2006, 12:00

on the money, finger tight will do!

BTW Imabell's last is an R44 blade.

CYHeli

20th May 2006, 06:31

I thought that until now the R22 had the prob and R44's were immune, I'll do a much closer daily now.:eek:

Does the R22 have the same AD for a daily tap test as the R44?

Are we smashing our blades to comply with an AD? :ugh:

Not that we should be tapping on the doubler, but along the leading edge bonding...

topendtorque

20th May 2006, 14:22

Tap test.

No - re the daily, it is required at the 100 only on the R22, section 2.410 para 13 [refers 9.130 (h)] , yes – re the bond joints and very much yes re the extreme care - with the coin, - according to the genuine maintenance manual a 1965 US quarter- no less, please don’t tell the insurance company!

R44’s - still very prone to the trailing edge debond prob, I hear, – there was a god awful bit of jungle talk recently about a dude who – a) found one – b) got up it with the metal set – c) flew it for a few days – d) upon his return to base his chiefy told him to stick it, (and all) when he was asked to pretty it up!

BTW – shouldn’t the nose bump be the international dit-dah-dit, not dah-dit-dit? Not trying to be the bastard – like!

Flyingpoodle

22nd May 2006, 02:19

I am flying a r44 raven 2 just comin on 2000hrs..... both blades are starting to delaminate at the doubler position the same spot as shown in pictures by imabell....... I have been told that it is still safe to fly and that i should keep an eye on it and that the delamination is "within limits",....... until when??????......
Does anyone know any other r44s that have come across this recently? And are they still flying or grounded.????

topendtorque

22nd May 2006, 06:07

Suggest that may a bit of an unfair question.

What about get out your red biro and generously wave it around the M/R while you ask the engineer to show you EXACTLY the limit as defined in the MM.

If it helps we interpret total area as that over any dimensions.

muffin

2nd Jun 2006, 13:16

A Service Letter has just appeared on the Robinson web site regarding this. I was talking to a UK maintenance outfit this morning who told me they are now getting several instances of -4 blade problems.
There is also one for the R44 blades as well.

Service Letter here http://www.robinsonheli.com/servelib.htm

slowrotor

2nd Jun 2006, 14:43

The service letter allows 2 inches of disbond. But no mention of repair ideas.
I would consider using thin CA super glue (cyanoacrylate), as it can penetrate into the crack. It wicks in. Could prevent more disbond.
Better check with Robinson first.

13snoopy

2nd Jun 2006, 15:35

belly tank

2nd Jun 2006, 15:46

Ive heard the R66 MR Blade will be of different design:D.........requiring only a tap test with only a $100 dollar note!.:ugh:

bellfest

2nd Jun 2006, 22:58

Almost correct bellytank. They will actually be the thickness of a $100 note and cost approximatley that each time they are tapped. The Gladwrap company will be looking on with interest at the possibility of scoring a sweet contract to supply...:E

bvgs

3rd Jun 2006, 06:16

bellfest

3rd Jun 2006, 08:15

It has been mentioned several times here that there is a tap test for the R44. I have checked on the Robinson website but can find nothing re the 44. Can anyone advise and point me in the right direction?
Thanks

Preflight section of the POH. "Tap your forehead with a 1965 US Quarter ( if you have one left after replacing the blades), if you get a hollow sound, go flying":ok:

topendtorque

6th Jun 2006, 10:06

Thank God I have been absent for awhile as the debate has grown some in intellect - especially as the colloquial ozzie ‘brick’ – aka $100 note – once brought into service will remind the Burbank Boffins to beef up the 66 somewhat.

For Bellfest, most who fly rotary already ‘have’ a vacant space between the earlobes, so the use of the ‘brick’ as per your POH notes will be best for that hollow sound – that is if you have one left - err confusion – err Frank never gave us a quarter – I don’t think?
And, it has to go down in history as the first time we ever got an inch or two out of the ornery old bastard!!

The diagram on the Robinson letter reminds me of another oz outback icon, that of the – “Whistlecock” – if those flaps bend down whilst still in service – man we’re gonna sound like the last of the banshees.

Seriously, it’s good to see that Frank is not worried about the doubler adhesion so much, I’m kinda glad that ‘it’ lets go before ‘it’ sets up a serious bending moment at ‘that’ station.

imabell

18th Mar 2007, 22:42

the aircraft was in a practice auto at about 200 feet when a severe vibration started. by the time they got on the ground with full power applied the rrpm was at 80 percent.
http://www.bluetonguehelicopters.com.au/pprune/cairns.jpg

IntheTin

18th Mar 2007, 23:11

WOW!!!:yuk:

InducedDrag

19th Mar 2007, 01:35

It looks like there is no paint left on the blades. I know you feather it back as it erodes, but that is the most "feathering" I have ever seen. Looking at the end cap, it looks like the paint is 1/2 off the blade. :eek: I have never seen this much paint removed before...... Not sure if there is a connection?

Johe02

19th Mar 2007, 07:39

Jeez . . whoever is maintaining/flying that needs their arse kicking.

Paint not allowed to go back farther than the lamination point! :ugh:

Is this sort of thing the cause of all these de-lamination stories?

Cant blame Frank for this one. .

scooter boy

19th Mar 2007, 08:25

"Paint not allowed to go back farther than the lamination point! ":ugh:

Is this a Robinson dictat?

Is that true for the 44 as well as the 22?

What is the remedy if it does? - new blades?

How 'bout the tail rotor, they start to lose paint pretty quickly on the leading edge/tip surface, how much is tolerable here?

Seems to me that flying in precip really accelerates paint loss (and therefore blade wear?) - in the UK this in inevitable - what kind of hours' usage are people getting before they need new blades? Is anyone getting the 2200 hrs? - I doubt it.

SB

somepitch

19th Mar 2007, 16:22

i would hope that the paint isn't the crucial structural material preventing delamination on robbie blades...:}

MLH

19th Mar 2007, 17:43

Two observations:

1) It appears that the first row of honey comb nearest the leading did not bond like the rest.

2) The leading edge of the skin at the D-spar interface looks like it did not bond with the substrate (darker green areas) as consistantly as in other areas (lighter green/white areas).

It may be that the paint acted as a filler in the area of the D-spar/skin interface preventing lifting of the skin. Lack of sealing in this area may also have allowed moisture entry or other contamination to become a factor.

Twiddle

19th Mar 2007, 21:43

There's probably a very good reason for it not being that way (hopefully apart from manufacturing cost), but it seems crazy that there's no lip on the skin that fits in behind the leading edge, with pins on the leading edge to retain it in situ as well as the bonding?

ericferret

19th Mar 2007, 23:30

Lack of paint should not give a delam such as this. Lack of surface finish including sealing which lead to water ingress followed by corrosion would.
Looks like a straight delam to me.

Avi8tor

20th Mar 2007, 05:39

Yeah, I would say the bostik let go. How many hrs had it done? Saw a R44 throw about a metre out of the centre of the blade in South Africa about a yr ago. The chopper only had 100hrsTT , guy was lucky to get out with only serious broken bones.

Twiddle

20th Mar 2007, 08:39

Robinson have issued a service letter regarding checking the paint on the bond line.

13snoopy

20th Mar 2007, 08:59

Johe02
Over 150 posts! About time I clicked here and ordered a Personal Title.

Join Date: Oct 2002
Location: England
Posts: 188 Jeez . . whoever is maintaining/flying that needs their arse kicking.

Paint not allowed to go back farther than the lamination point!

Is this sort of thing the cause of all these de-lamination stories?

Cant blame Frank for this one. .

Please sir, surely you are attempting humor here.
I think all this does is solidify the theme running over most of the helicopter-planet, and that is that Frank needs someone else (i.e. another more-qualified company) to make his blades. His folks certainly aren't getting it done.
Very sad.

MLH

20th Mar 2007, 17:47

Searching the NTSB accident records for R22 & R44 does not show any issues relative to blade delamination.

Any idea of the total number of occurances worldwide?

Johe02

20th Mar 2007, 20:36

Hey Snoopy

Join Date: 11th November 2003
PostsTotal Posts: 79 (0.06 posts per day)

Whats your point??

You think its ok to run a Robinson with no paint on the blades??

If the paint comes off they need re-painting.

If you feather the paint early, they last longer.

T'aint rocket science. . :8

bladewashout

20th Mar 2007, 22:04

Anyone got a comparative picture of a blade with the paint still attached?

BW

paco

21st Mar 2007, 00:58

Was that machine used on cattle mustering, where positioning flights are not routinely put into the tech log? That blade may well have done way over its time.

Phil

topendtorque

21st Mar 2007, 12:46

I think all this does is solidify the theme running over most of the helicopter-planet, and that is that Frank needs someone else (i.e. another more-qualified company) to make his blades. His folks certainly aren't getting it done.
Very sad

Yep.

Easy to note that there are as yet no comments form the antipodes. Mainly because every one is
A_B_S_O_L_U_T_E_L_Y S_T_U_N_N_E_D.

It matters not where it started to delaminate from. I have heard two opinions.

It was also purely co-incidental that sometime on the last flight that the blade gob smacked a bug or beetle of some sort, 3 and 11/16’” on your picture inboard from the tip of the blade proper.

You will notice that the witness mark is not only on the underside exterior bottom edge of the leading edge, but also on the spar material and the underside of the skin. In other words the skin at that time was flexing open just a tad enough to allow that juice to flow in between the skin and spar.

Is Frank the only person on this helicopter planet that believes that bonding stainless steel can be done to perfection without acidic or laser etching, or is this just a routine type (without putting too plain a point on it) of quality control gone missing?

The photograph portrays a very large percentage of material that was never bonded.

We also assume that the honeycomb was supposed to be all the way to the leading edge as well? Perhaps the missing bits allowed flexing of the skin which caused the glue to crack progressively.

There is no sign of prior damage to the leading edge, to initiate this damage.

I think what we see is what we have got, a failure. Why?

That blade may well have done way over its time.

No I do not believe that it has done anywhere near it’s time; it was only fitted in November ’05.

For those who comment that there is excessive paint abrasion, yes that certainly appears to be the case for six hundred hours. However, paint abrasion always occurs from the outside in, bonding failures occur from the inside out.

I and many others here would have experienced leading edge erosion to the point that the skin became so thin that it started to break up, but was still firmly bonded to the underlaying spar.
Still Stunned

flyagain

22nd Mar 2007, 04:24

There's too much money involved for anyone to do anything about it. CASA and the ATSB don't want to know about it.

Just found a closed thread from April - May last year, through the course of the thread there are no fewer than 10 Robinson blade delaminations mentioned. All dash four and all with well under 1000 hours on them.

Helicopspeeder

22nd Mar 2007, 11:10

I think there is a very important point being missed here. There have been numerous accidents and incidents involving R22s and R44s. We have all heard other pilots relating "robbie blade delamination accident" stories. Up until now we had no definitive proof that these blades were in fact coming apart. The delamination was always conveniently explained away as a result of the accident rather than the cause of the accident. Now, due to this pilot's uncommon skill and a healthy helping of luck we have a machine parked on its skids with a 600 hr blade peeled apart like a filleted fish. CASA don't want to know about it. Has the FAA been notified? I wonder what their reaction would be when faced with grounding a significant portion of the revenue producing machines in the U.S.
Hey Frank, your machines are flying apart in flight. I know pilots who would rather risk losing their jobs than fly robbies. What is it going to take. These are not overflown mustering machines, they are always hangared, well maintained training and tourism machines. Next time it might be one of the low-time, wealthy private owners that CASA is scared of offending, then we'll see some action.
I'm not just having a whinge, let me know what I can do to help prevent another delamination accident. But let's do it now.

Wilf

23rd Mar 2007, 00:36

Do you have any more photos you can post?

bladepitch

23rd Mar 2007, 01:07

i fly a 44 and have not encountered this yet. i say yet! how ever checking the blades every morning as is needed may not be sufficient. the paint on our blades is more eroaded on one than the other. still not back to the seem yet. they seem in top condition. and we fly over water on take off and landing.

i know flying in precip is not good on frankys blades especially in a salt enviroment. we wash our chopper every day for obvious reasons and im sure im going to encounter this at some stage.

sorry to crap on but here is my question

we operate an astro and delams seem to be happening on later models?
yes ?

correct me if im wrong.
does this indicate that frank has changed design and contruction methods that greatly that saftey is no some what comprimised.

BP

John Eacott

23rd Mar 2007, 03:03

http://www.helicopterservice.com.au/photos/pprune/R22%20delam.jpg

I'd be interested to know why there appears to be no signs of bonding in the highlighted areas.

I'd guess that the honeycomb in the blade has been distorted by the airflow on the way down (there is ample evidence that it was bonded, from the bonding marks left on the inside of the skin), but the blade spar and the skin both seem to show signs that the bonding has been failing for a while.

ericferret

23rd Mar 2007, 16:10

The bonding appears to be inconsistent.
In some places the adhesive has separated from either the skin or the structure cleanly. Looks as if it didn't take properly.
However if you look at the area just inboard of the tip it appears that the bonding held but the surface of the composite tore off. That looks like a solid bond to me with the joint destroyed by the force of the skin being peeled in the airflow.

belly tank

23rd Mar 2007, 22:25

Found this on RHC Website

http://www.robinsonheli.com/srvclib/r22r44sa_blade_debonding_31607.pdf

bigruss

23rd Mar 2007, 23:59

The operating enviroment and conditions, flying techniques have not changed.
Only the blades have changed. Obviously the old blades 40 thou skins were rigid enough to hold their shape even if not bonded correctly. The new blades have an 8 thou skin. Robinson's rushed production run to manufacture dash 4 blades probably came at a quality control sacrifice. Operators in erosive enviroments are going to have keep their blades painted (all eviroments), perhaps an outboard end repaint every 300 hours.
bigruss

ericferret

24th Mar 2007, 11:10

I dont have access to Robinson service info so could someone tell me if Robinson call for any type of debonding checks prior to the blade surface finish being restored?

Thanks
ericferret

Helicopspeeder

25th Mar 2007, 10:44

I'm going to have to call Bullsh*t.
Now that we have definitive proof that these blades are delaminating and the delamination can't be blamed on an accident rather than being the cause it seems that Robinson is going to have a crack at the operator for not keeping blades painted. So let me get this straight, the blades are held together by the paint? Makes you want to go out and become a robbie owner doesn't it? What if I'm 200 miles from home and its raining? Do I land every five minutes to check that the paint holding my $400,000 aircraft together is still there. We keep hearing about all the broken helicopter sales records. What happens to all those $$$$$s, obviously not enough being spent on R & D. Get real Frank, enough excuses, don't make another bloody helicopter before you get the first ones right.
I can stuff up my duty times by .5 and get hammered by CASA yet they don't want to know about helis flying apart in flight????????????????????????????????

topendtorque

25th Mar 2007, 12:00

ericferrit
if you have access to the link provided by 'bellytank' you'll also be able to access the other SL mentioned from the RHC site. There does not appear to be much variation in those notes from the MM. Merely tap test the bonded areas of the skin and do the old ten power trick up and down the bond lines.

Helicopspeeder
we sure as hell share your frustations and the more heat the better I feel.

With regard to "John eacott's" notes I would say that there is ample evidence that the honeycomb was short by a substantial amount on the leading edge row.

This must have meant that the skin was allowed to flex ad-infinitum at that point thus setting up a fatigue cracking action upon the bonded section. I don't think it would have mattered whether it was properly bonded onto the spar or not.

The lack of honeycomb support meant that the bond was going to come away sooner or later. There was plenty of time for the later bit as the blade has 1600 hours remaining!

Maybe the repainting will push the pressure and vibratory characteristics of the prevailing relative wind further forward, until it wears down yet again.

If, that retards the cracking action and protects the skin, then it is a good investment. but to be relying on such a flimsy safegard is as you say a moumental indictment of sloppy engineering and safety principles.

1) the quality control should have ensured that the honeycomb was ALL the way to the leading edge, a very simple task one might say, and

2) the stainless steel is gong to have to be treated so that it will bond 100% of the intended areas, no less.

Grounding, or attempting to ground the A/C is sure as hell gonna kick up a stink.

ericferret

25th Mar 2007, 14:29

Thanks for the info on the tap test and visual inspection.
I was mentally comparing the problem to the issue involving debonding of MD 500 tail rotor blade leading edge strips. It was found that the tap test did not give sufficient warning of a debond. Hence the requirement to use dye pen around the skin/strip bond line. Any minor debond would hold the dye and it would show under developer.
It works as I found out to some embarrasment when I failed to do it properly and another engineer found the debond using this technique.
My point is that a "tap test" is in my opinion inadequate as it relies on hearing
and accuracy of the tapping, in other words operator skill. Given that unlike the 500 edge strips where the bond lines are "out of wind" the skins on the Robinson blades are "into wind" therefore the situation is far more critical.
I believe that the tap test might not show a debond prior to the blade being refinished. It would then continue to debond till it fails.

bladewashout

25th Mar 2007, 18:45

Helicopspeeder Wrote: Get real Frank, enough excuses, don't make another bloody helicopter before you get the first ones right.
I find this anger hard to understand. The picture clearly shows a level of paint erosion way beyond what most of us see even after 2000 hours on a blade. The safety notice from Robinson doesn't (to me) seem that unreasonable: paint over the laminate will preclude airflow into the gap, so if you live in an erosive environment, keep them painted. There are an awful lot of blades out there that are not delaminating. If there's paint cover, a crack is going to be visible immediately.
Yes, I have no doubt that for $100,000 per blade we could have something that could manage differently, but we want to fly at reasonable cost, so we have to live within the parameters that permits. In this case, it means painted blades.
I haven't heard anyone claiming that blades which have retained paint cover are also failing: if they were, we would be in the same position as past recalls and Frank would, I have no doubt, produce a fix, or new blades and there would be a recall, some level of help which would satisfy some people and antagonise others. There would be an interim safety check for us all and if it's very serious the FAA and CAA etc. will ground them.
If you fly a Robinson, you fly the best that can be achieved in a cost effective heli, and that comes with caveats. No, they should never fall out of the sky, but if there are limits to what cost-effective engineering produces, then we, the customers, may have to bear some of the cost burden of sorting it out when things are not perfect, both in time, lost flying hours and money.
If you don't want that kind of flying, don't buy any aircraft built to a budget. You only have to read the Robinson 'return-to-base' warranty to understand its limitations. That's not because Frank doesn't give a sh*t, it's because he has made a helicopter that is affordable to the masses.
I completely understand the concern over resolving the problem, and (as a 22 owner), I'll be checking my blades very carefully. But the way you state that Frank hasn't built the helicopter 'right' suggests that you shouldn't be flying anything which isn't at the pinnacle of engineering excellence regardless of cost. Many of us can't afford that and Robinson represents the best opportunity of safe and cost effective flying in the industry.
If you want to go and spend your life creating a company that builds helicopters 'right' in this market, then go right ahead and if you can do better than Robinson at the same price with less problems, you are going to be a very rich man indeed!
BW

IntheTin

25th Mar 2007, 18:51

Great post Bladewashout. :ok:

topendtorque

25th Mar 2007, 21:06

ef
The RHC MM specifically warns against using penetrant material anywhere near any bonding line.

I understand how you could miss seeing a witness dye pen indication. I know of another from some time ago where the check was done, because the penetrant showed up in the forensic examination.

I now think it could have been (in that case) that when using the technique in an enclosed area and onto a threaded area that the grooves of the thread could cast a shadow for the spray can application, or if the spray was held too close then all of the surface material may have been washed away.

bladewashout.
I appreciate your post for sure.

However if you imagine that the firmness of the supporting honeycomb could act as a redunancy measure for a not well bonded skin, then how much money will it cost for someone to peruse tha honeycomb before the skin is applied. If the honeycomb was there it would have melted into the bond material at least when it all got cooked.

also how little extra would it cost to just etch the bonded aears of skin? not much i suspect.

Friendly Black Dog

25th Mar 2007, 23:57

No chance that these blades have been regularly wiped with WD40 (or similar)?:rolleyes: When this post first came up I think it made mention of the machine being used in coastal Qld for instructing but now I can't find that post. I don't care which school, but it would be interesting to know if they have a policy of getting the students to WD the blades? A light rub on the leading edge is one thing, but a soaking (by an un-supervised/over exhuberant student) would be another.

Cheers FBD

Pandalet

26th Mar 2007, 09:06

Something I'm curious about, since seeing that photo:

It seems like the leading edge metal is underneath the lower skin, so that as the blade rotates, the airflow is 'pushing the lower skin away' from the leading edge. Wouldn't it make more sense to have the leading edge overlap the lower (and presumably upper) skin, so that the integrity of the blade isn't just dependant on the bonding? Or is there a reason this isn't done?

Helicopspeeder

26th Mar 2007, 11:09

Hey Bladewashout,
Great post, well put and some very good points. My anger comes for a number of reasons. Chiefly the excuses that have been used and the blame game reulting from previous accidents which we all are pretty confident have been caused by blade delaminations. Also, without divulging too much info, I have a very close relationship with someone who has trusted this machine with their life. This machine was extensively checked by the ATO, a competent engineer and, no-doubt, the student. What more could be done? This problem has existed for a long time now but no-one with the authority has chosen to be pro-active about a remedy. How often have you been frustrated by big companies who know about a safety issue but do nothing until someone is killed or maimed and then put on a big show of compassion and remedial action? All of this when acting on the obvious problem prior to an accident rather than making excuses or blaming others could have saved lives.
I don't fly them and never have, many of my friends, family and colleagues do, however. Your point about many other blades out there not delaminating may or may not be a little premature. Maybe we should wait and see after all the operators out there have checked their machines. I personally know of two more (R44s) which have been grounded due to signs of early stage delamination. In the meantime I shall try and take a leaf out of your book, your point was well made without anger or blame and I applaud you for it.
Helicopspeeder

topendtorque

26th Mar 2007, 12:45

Pandalet
excellent question. i was trying to find a picture of the blade profile on the RHC site for you look at, to no avail. and i am no artist.

If you can track down the the R22 Maintenance Manual Section 9 page 22A. all will be revealed.

The bit you see in front is the spar, leading etc , one piece.
At the trailing edge of that, for a distance of .5 inch top and bottom, there is a recess for the blade skin to sit snugly into and presumably just inside the exterior dimensions of the leading edge spar.

Within the skin of course is the honeycomb as witnessed above.

The problem, (to me anyrate) is that if the honeycomb is MIA then the skin will not be 'formed' as it should be and liable to buckle inwards whenever the resultant airflow presents itself as a pressure force, as in autos or~ dare I say it ~ the dreaded quick stop maneuvre.

I think the real answer to your question is that total weight was a limiting factor, and corners had to be cut (literally) where they could.

However I would very much like to hear someone from RHC answer your question.

While you are on the RHC site go to - customer support - publications - Safety Alert 4th Jan 2007 (I.E. before our oz incident) - then Service Letter 56. (dated March).

I wonder how many other "reports" referred to in the service letter, of others that there were????????? Another question for RHC.

FBG

That is an excellent point, one worth pursuing and perhaps a practice worth curtailing. As far as penetrants go they don't come much better than that old mosquito repellant stuff as such. I at least shall try to enquire as to whether it is also considered as hazardous to the glue that is used.
tet

ericferret

26th Mar 2007, 14:07

I have been trying to think if any other helicopter I've worked on in the last 30 years has suffered from this type of failure. That is skin opening into the airflow in a sudden failure.

I can't recollect this happening. So if all the other manufacturers can keep there blades together with or without paint then I am sure that Robinson should be able to do the same.

I seem to think that Enstroms used to do something similar on the leading edge but this was always the result of corrosion pushing the skin up.

Wilf

27th Mar 2007, 00:29

To build on Pandalet's excellent question - wouldn't mechanical fasteners augment the adhesive and potentially solve the problem?

IFMU

27th Mar 2007, 01:10

To build on Pandalet's excellent question - wouldn't mechanical fasteners augment the adhesive and potentially solve the problem?
Wilf,

I'm not sure this is a good idea. Usually when you sink threads or holes into a rotor blade spar, it's bad for fatigue. Maybe it would be a lot less at the tip.

Properly bonded materials tend to stay bonded. I've heard it said before that if it stays together, it was bonded. If it came apart, it was glued.

The enstrom has a similar, but simpler rotor section. A big honking extrusion, with a top and bottom skin bonded on, and the skins bond together at the trailing edge. The skins do not wrap all the way around the leading edge. The Hughes/Schweizer blades have a skin that wraps from tail all the way around the leading edge and back to the tail again. Still all bonded metal. They seem to stay together.

As several others have mentioned in this thread, it is suspicious that the HC doesn't look bonded to the skin. I think it was glued.

-- IFMU

B47

27th Mar 2007, 09:37

I would appreciate opinions on the WD40 or not issue.

I am a former B47 owner, where it was accepted that spraying or wiping every potential corrosion source with WD is good owner 'maintenance' (If you own a 47 and ain't buying WD in bulk, you're neglecting it..).

Now I'm the owner of an Astro I hear conflicting opinions on whether I should wipe the baldes with WD40. Of course WD40 should be kept well away from all rubber and elastomeric bearings on a Robbie and I never go near the head or T/R hub with it. But I'll tell you why I think it's a good idea: My Astro lives in a well ventilated (unheated) hanger and after a nightime temperature/humidity change, you can see regularly a line of condensation droplets hanging beneath the main blades. Guess where these droplets sit? Yes, bang on the bond line between the leading edge and lower skin. I've considered leaving the machine parked with a bit of pitch on, that will force these droplets back a bit. So this bond line, even in an ideal situation, is wet a lot of the time (add a bit of coastal salt to this and the result is obvious).

If the paint cover on the bond line is complete it probably doesn't matter, but I have recently adopted the routine of wiping the leading edge and lower surface with a sponge soaked in WD40. This reduces the condensation substantially and keeps the leading edge cleaner of flies in summer.

The whole problem with Robinsons, in my humble view, is not the machine, Frank, or the design, it's that they need a little more TLC in commercial and training environments than more (sensibly) over-engineered types. When is the last time you saw a training school with a routine for students cleaning blades? I'm also often horrified by the condition of some privately owned machines. If you adopt a 'kick the tyres and go' approach and leave everything to your engineers every 50hrs, it'll cost you in the long run.

The 44 is a very clever piece of engineering, built to a price and is one of the safest types flying - but it can't be abused like an old 206. The retreating paint edge must be flatted down gently every 100 hours or so - if you don't, the proud paint edge will be lost much faster and it can also cost you over 5kts. The outers of the blades obviously need painting when the retreating edge gets anywhere near the bond line. Only a fool would let it get that far. Unless you're flying regularly in rain or airborne sand, this is probably only necessary once between the 2200hr/12yr overhaul.

Lastly, I think my good old B47's unfinished stainless leading edge would be an improvement for R44 blades, but obviously Frank has his reasons for not doing that. The bond line where the paint starts is never disturbed because the paint edge is never eroding towards it. The 44's painted leading edge means you have to maintain the retreating paint line - if you don't, you're neglecting your machine.

So, WD40 or not?:(

ericferret

27th Mar 2007, 10:05

WD 40 fell out of favour as it was found that after a certain period of time it abscorbed water. Spraying the internals of military aircraft with it was a common task in the seventies. I believe that the 40 stood for 40 day protection.

I have read that ACF 50 which does the same job and is aircraft approved does not abscorb water, but you would have to look into that.

ericferret

27th Mar 2007, 10:22

Thanks for that IFMU, you also reminded me about the other standard Enstrom problem, debonding trailing edges usually fixed by rivetting but also usually the writing on the wall for the blade as the split was usually followed by corrosion due to water ingress.

Your comment on the Hughes blades is a good point. Constructed from "front to back" you can't get them debonding into the airflow. Mind you the errosion of the unprotected aluminium leading edges used to be a problem on the older aircraft.Come to think about it I never saw a debonded trailing edge on either a 300 or a 500.

I would say that if you build a blade in the Robinson style (which is not unusual) the bonding has to be top class.

I still find it hard to accept that a layer of paint is the difference between flying and crashing. Modern aircraft design is supposed to be fail safe or at least fail in slow inspectable way. This failure was sudden and potentially catastrophic.

I wonder if blade tape might be a temporary answer to this.

Unhinged

2nd Apr 2007, 06:45

From CASA today:

AWB 62-004 Issue 2 - Robinson Helicopter Main Rotor Blade Disbonding
http://www.casa.gov.au/airworth/awb/62/004.pdf

flyagain

2nd Apr 2007, 09:57

"Preflight inspection of this area should allow early detection of a disbond before it progresses."

The helicopter at the center of this thread was inspected by not only the ATO but also an engineer the morning of the flight. If they can't pick it up who can?

This comes with news of a R44 with less than 50 hrs TT grounded because it failed tap tests on both blades.

topendtorque

2nd Apr 2007, 13:31

My goodness a speech from CASA.

Their background notes seem to paraphrase what I have heard as the general thoughts on the subject, except to add that the eroded away bond line gap, between skin and spar, which may be up to a millimetre in width may have allowed a circular erosion especially in dusty conditions upon the leading edge of the already very thin skin, thus reducing its thickness.

From there I guess there would have to be further eroding of the bond material into the gap in front of the leading edge of the skin, extending to under the skin, to allow a wind gap and a now flimsy knife edge skin to be pushed into the airflow.

Far fetched? maybe. Seeable upon preflight? it should be.

Problem is there is 3000 sets of blades out there built the same way.

There is also a small number of cowboys out there who think that these blades are stronger and better and therefore will last longer than dash 2 blades.
Yep, we may read about them.:{

I believe that a mod has been done to 'tighten' the gap between the skin and spar and to allow for the leading edge of the skin to be pressed down further into a groove in the spar.

There was an inspection done 'by order' from ATSB before these blades left the country. I believe that ATSB have communicated, as one might expect, with NTSB, FAA and RHC. Stand by for another AD or SB.

WD40? cannot find anyone to support that idea, come to think of it why did we do it way back when, other than it being a 'practice' of tradition.
Just a soap and water wash down should have been sufficient each day.

Blade tape has been suggested, that is certainly my preference after re-painting, if required. I would favor a two piece kit such as we used to run on the 47's.

Of course no solvents allowed for cleaning gum off after the blade tape removal. I hear that eucalyptus oil will do the trick.

Also there has been some suggestion of using a harder two part marine primer.

STL206

3rd Apr 2007, 04:34

"No tape, nor WD-40 is allowed - they'll tell you that in the factory."

Agreed on the WD-40. It contains solvents, which you want to keep away from bonded surfaces. Also it becomes sticky as it drys and attracts dirt.

RVDT

3rd Apr 2007, 06:41

Application of blade tape - unless this procedure is documented within the maintenance manual or someone raises an STC or mod for it, keep in mind that it is an ILLEGAL modification!

ericferret

3rd Apr 2007, 08:10

Obviously any fitting of blade tape would have to be approved.

Blade tape affects autorotative RPM and blade performance.

It can bring problems of it's own i.e asymetric loss of tape.

On a light blade it might affect the fatigue characteristics.

All these issues would have to be addressed before blade tape was approved.

topendtorque

3rd Apr 2007, 10:57

Agreed, we'll see what comes out of it re blade tape.

By co-incidence this story about WD40 came across my emails this afternoon. Now we should know all there is to know about the stuff. I've left it as is, a bit of a long story.

INTERESTING INFO

Water Displacement #40. The product began from a search for a rust preventative solvent and de greaser to protect missile parts. WD- 40 was created in 1953 by three technicians at the San Diego Rocket Chemical Company. Its name comes from the project that was to find a "water displacement" compound. They were successful with the fortieth formulation, thus WD-40. The Corvair Company bought it in bulk to protect their atlas missile parts.

The workers were so pleased with the product, they began smuggling (also known as "shrinkage" or "stealing") it out to use at home. The executives decided there might be a consumer market for it and put it in aerosol cans. The rest, as they say, is history.

It is a carefully guarded recipe known only to four people. Only one of them is the "brew master." There are about 2.5 million gallons of the stuff manufactured each year. It gets its distinctive smell from a fragrance that is added to the brew.< /SPAN>

Ken East (one of the original founders) says there is nothing in WD-40 that would hurt you.

When you read the "shower door" part, try it. It's the first thing that has ever cleaned that spotty shower door. If yours is plastic, it works just as well as glass. It's a miracle!

Then try it on your stovetop... Viola! It's now shinier than it's ever been. You' all be amazed.

Here are some of the uses:

Protects silver from tarnishing.

Cleans and lubricates guitar strings.

Gives floors that 'just-waxed' sheen without making it slippery.

Keeps flies off cows.

Restores and cleans chalkboards.

Removes lipstick stains.

Loosens stubborn zippers.

Untangles jewellery chains.

Removes stains from stainless steel sinks.

Removes dirt and grime from the barbecue grill.

Keeps ceramic/terra cotta garden pots from oxidizing.

Removes tomato stains from clothing.

Keeps glass shower doors free of water spots.

Camouflages scratches in ceramic and marble floors.

Keeps scissors working smoothly.

Lubricates noisy door hinges on vehicles and doors in homes.

Gives a children's play gym slide a shine for a super fast slide.

Lubricates gear shift and mower deck lever for ease of handling on riding mowers.

Rids kids rocking chairs and swings of squeaky noises.

Lubricates tracks in sticking home windows and makes them easier to open.

Spraying an umbrella stem makes it easier to open and close.

Restores and cleans padded leather dashboards in vehicles, as well as vinyl bumpers.

Restores and cleans roof racks on vehicles.

Lubricates and stops squeaks in electric fans.

Lubricates wheel sprockets on tricycles, wagons, and bicycles for easy handling.

Lubricates fan belts on washers and dryers and keeps them running smoothly.

Keeps rust from forming on saws and saw blades, and other tools.

Removes splattered grease on stove.

Keeps bathroom mirror from fogging.

Lubricates prosthetic limbs.

Keeps pigeons off the balcony (they hate the smell).

Removes all traces of duct tape.

Folks even spray it on their arms, hands, and knees to relieve arthritis pain.

Florida's favourite use is: "cleans and removes love bugs from grills and bumpers."

The favourite use in the state of New York--WD-40 protects the Statue of Liberty from the elements.

WD-40 attracts fish. Spray a LITTLE on live bait or lures and you will be catching the big one in no time. Also, it's a lot cheaper than the chemical attractants that are made for just that purpose. I eep in mind though, using some chemical laced baits or lures for fishing are not allowed in some states.

Use it for fire ant bites. It takes the sting away immediately and stops the itch.

WD-40 is great for removing crayon from walls. Spray on the mark and wipe with a clean rag.

Also, if you've discovered that your teenage daughter has washed and dried a tube of lipstick with a load of laundry, saturate the lipstick spots with WD-40 and re-wash. Presto! Lipstick is gone!

If you sprayed WD-40 on the distributor cap, it would displace the mo issuer and allow the car to start.

It removes black scuff marks from the kitchen floor!

Use WD-40 for those nasty tar and scuff marks on flooring. It doesn't seem to harm the finish and you won't have to scrub nearly as hard to get them off. Just remember to open some windows if you have a lot of marks.

Bug guts will eat away the finish on your car if not removed quickly! Use WD-40!

UP. S. The basic ingredient is FISH OIL

ericferret

3rd Apr 2007, 15:24

If it keeps off cows why would you need it to remove lipstick marks!!!!!!!!!

Sorry misread that, it keeps flies off cows..........................

flyagain

10th Apr 2007, 07:22

Have we heard the end of this whole thing or will the ATSB issue a report? Hopefully they won't wait for too long.

I know a lot of nervous pilots (and their families) waiting for some well deserved answers.

I'm afraid the "lick of paint" reaction don't cut it.

Practice Auto 3,2,1

10th Apr 2007, 17:00

http://www.robinsonheli.com/srvclib/r22sb96.pdf

http://www.robinsonheli.com/srvclib/r44sb61.pdf

moosp

12th Apr 2007, 04:25

Just received SB-96 with details of the compliance procedure. I'm fine with the x10 inspection but the tap test is a challenge.

"Tap test all exposed skin-to-spar bonded areas with a 1965 or later U.S. quarter-dollar coin."

Now where am I going to find one of those on a cattle station in Queensland??? :hmm:

flyagain

12th Apr 2007, 09:26

So let me get this straight, this is a once of inspection required? Then what? What about the blades that had less than 50 hrs and both were coming delaminated in North Queensland three weeks ago. Robinson has a bigger responsibility than just issuing this SB.

I would be loathed to fly one of these pieces of *$#^ after I've seen what has happened. Every time a Robbie goes down with even the slightest hint of loss of control I won't be the only one wondering.

Money talks right...

One more thing, how does "excessive erosion" occur after less than 50 hours?

John Eacott

13th Jun 2007, 08:25

Yet another missive from Robinson, here. (http://www.robinsonheli.com/srvclib/mr_blade_skin__debonding_appendum.pdf)

ADDITIONAL INFORMATION REGARDING MAIN ROTOR BLADE SKIN DEBONDING
To: All R22 and R44 Owners, Operators, and Service Centers

RHC has recently issued Safety Alerts and Service Bulletins to address debonding at the outboard end of the main rotor blade lower skin. Although there have been several reports of blade skins beginning to debond, the problem has not been random or widespread. It has been limited to blades subject to excessive erosion and/or corrosion.

On one blade, a large area of corrosion between the lower skin and bonded-in cap at the tip of the blade caused the outboard few inches of skin to peel up. All other debonded blade skins examined by RHC were the result of excessive erosion at the skin-to-spar bond line. The bond joint is exposed when all finish (paint and primer) has been eroded at the bond line. An exposed joint can allow rain and dust particles to damage the adhesive bond at the skin’s leading edge. Operators flying low in dusty environments should be particularly alert to the condition of their blades.

Pilots should look at the lower outboard surface of the blades at each preflight (at least once per refueling). It is easy to check for excessive erosion. (Erosion is always worse on the lower surface due to the angle of attack of the blade in flight.) The bond line is approximately one inch aft of the blade leading edge and is visible as a straight line when exposed. Blades with bare metal up to, or aft of, the bond line must be refinished per R22 SL-56/R44 SL-32 before further flight to prevent bond joint damage. As long as finish covers the bond line, bond damage due to erosion should not occur. If the bond line is not exposed, pilots should check that no visible crack in the paint exists along the bond line. Mechanics must check for corrosion between the skin and tip cap by performing a tap test during 100-hour inspections.

Recently manufactured blades have had production tolerances tightened to minimize the width of the bond line and reduce susceptibility to erosion damage. However, these improvements are not a substitute for appropriate maintenance and preflight inspections.

that chinese fella

13th Jun 2007, 09:05

I have emailed RHC this afternoon after receiving the letter that John posted.

With all the RHC products flying in remote areas simply to say keep repainting the blades is often not a viable solution. I feel they have an obligation to do better.

rotors88

13th Jun 2007, 09:38

The Robinson helicopter is the dodgiest bucket of puss or should I say death trap machine ever built. Its the helicopter that has killed more pilots than any other machine on the planet, some blades delaminate even in the box prior to installation, sad & very scary. Many young (time wise) pilots blindly worship them as if they were the best thing since a trusty ole' Jetbox, sadly though the wrecks of machines & wrecked families lives paint a different story. Ask on honest L.A.M.E. who has worked on a variety of machines for a few years for their appraisal of a Robinson. If we all got together boycotted flying these rickety hazardous contraptions, maybe, just maybe Mr Robinson may build something descant.

DONKEY73

13th Jun 2007, 10:51

I'm not here looking for an argument with anyone just expressing my view.

I do find this forum extremely informative and a valuable piece of information.

I am a low hours PPL and now fly both the R22 and R44. I have little experience of other aircraft and i hope to progress when my hours / experience allows.

I understand the problems with Robinsons and the high casualty rates. I do understand why many pilots dont hold robbos in high regard.

I expect there is a distinct correlation between the high number of 22's out there and the relative inexperiance of the pilots flying them ( myself included ) and this relationship probably contributes to a great deal of incidents each year.

Without the 22 i would probably not have started flying. The 22 makes the learning and hour building process marginally affordable.

I would also imagine there are quite a few commercial pilots that wouldnt be in employment now without robinson helicopters. As an instructor valuable hours are gained in these aircraft to enable a commercial pilot to move on to bigger and better things.

Donkey73

scooter boy

13th Jun 2007, 11:42

Well said Donkey.:D

The massive numbers of cumulative hours flown in Robinsons (by many low time pilots and private owners around the world) accounts for the number of accidents recorded.
With the 22 it was carb ice and rotor stall.
Now we have some delamination issues with 22 and 44.

Am I going to sell my 44 and buy (for the same money an old) Jet Ranger, EC120 or Hughes500? - Hell no! I love my 44 - I've had it from new, been the only pilot and tucked it up in its little hangar every night safe and sound away from the elements.

Good preventative maintenance coupled with careful flying in half decent conditions seems the right combination to minimise the risk of sudden death in any aircraft.

Dodgy bucket of puss? I don't think so, especially when you consider the overwhelming chasm of cost between the Robinson products and the alternatives. At the end of the day mechanical failure remains low down on the list of causes of helicopter accidents. Doing something dumb remains firmly at the top and we should remember this.

SB

topendtorque

13th Jun 2007, 13:19

I also congratulate donkey boy.

It seems amazing that everyone buckets the R22 for all the training accidents for instance, but completely misses the point that by and large it is the only training machine around at this point in time.

Just imagine if all the training was done in squirrells, hydraulic problems?? down time with engine problems while the component is returned to Frrrannnsss? etc. etc.

However the chinese fella has hit a chord, the problems with securing the paint to do the called up mod and the time taken for the paint to dry just don't add up to commercial sense.

C'mon you Robinson factory guys give us a break mate, we need a quick dry, readily available hard paint to use that can be easily bought in other countries.

It's not too hard is it, just a tim of paint and a US quarter and Bob's your uncle, we'll be happy?

TiPwEiGhT

13th Jun 2007, 14:43

Just read in a previous post about WD-40. Out of interest it stands for "Water Despersant - 40", the "40" was the chaps 40th attempt to make it work... and it did. Handy stuff.

TiP

scooter boy

13th Jun 2007, 15:20

TIPWEIGHT "the "40" was the chaps 40th attempt to make it work... and it did. Handy stuff."

Just like it took Dr Christian Barnard 42 tries (42 on table and postop deaths) before he and his team succeeded in performing the first successful heart transplant - can you imagine that kind of thing being allowed in this day and age?

Try try try again!

SB

that chinese fella

13th Jun 2007, 23:32

Pat Cox from RHC replied to me and advised that their engineers are working on a better solution to the problem.

IMHO part of the field issues with Robinson is that people are so used to working on 206 and other more robust machines, that they tend to gloss over the often very specific called up maintenance actions/inspections.

RHC know their machines well and this is obvious in the very detailed inspection criteria in certain areas. What could be passed off as ok in a 206 (Blade erosion for instance) is obviously not ok in a RHC product.

The point I raised with RHC was that it is a bit unrealistic to expect remote area operators to have access to painting facilties/equipment/expertise.

Senior Pilot

24th Nov 2007, 04:06

Airwolf Aerospace STC Prevents Delamination of Robinson Helicopter Rotor Blades

Airwolf Aerospace LLC, a division of Airwolf Filter Corp, a world leader in firewall-forward accessories for aero-engines, has been awarded FAA STC# SR02491CH to prevent permanently the leading-edge skin delamination occurring on Robinson R22 and R44 helicopter main rotor blades.

The factory Service Bulletin notes that main rotor blade skins begin to debond (separate) at the skin-to-spar bond line on the lower surface near the blade tip. Debonding can occur when the bond line is exposed due to excessive erosion of the blade finish, or when corrosion occurs on the internal aluminum tip cap.

Robinson Helicopter Company has issued Service Bulletins to inspect and address the problem using repeat-as-necessary paint applied to the affected areas, while Airwolf’s STC comprises a permanent, one-time application of Airwolf Rotor Blade Protective Tape (RBPT) to the outer section of the main rotorblades.

There are over 8,000 Robinson R22s and R44s on North American and international registers. Airwolf’s one-time solution eliminates the need for blade repainting.

Jonny Quest, Airwolf technical director, said this STC solves a recurring problem. “The factory ‘solution’ is really a band-aid, while ours is simple and permanent,” he said. “It comprises the application of a specially-formulated adhesive polymer tape which has been time-tested by the military in both the Gulf War and the Iraq war.

“Water, dust, sand and other contaminates can’t penetrate the tape, while the factory ‘paint solution’ requires repetitive inspections and continual repainting throughout the blade life,” he added. “However, the risk of a blade delamination is still great and the replacement cost very expensive if this occurs. The Airwolf RBPT is inexpensive insurance to prevent this from happening.”

Link here. (http://www.airwolfaerospace.com/)

JimBall

24th Nov 2007, 09:23

Please note that the STC referred to above is not approved by RHC. As has been stated previously on this thread, blade tape is not approved by RHC for a variety of reasons.

Until the factory come up with a treatment, the only way to deal with this is thorough Check As every day. (In the UK that is mandatory for every helicopter) You don't need a ladder - you just need to look up to the bond line and maybe use a bright light to look ALONG the bond line.

What are talking here - 30 secs a blade ?

Isn't that what you were taught ?

Senior Pilot

4th Jan 2008, 08:55

FAA calls for comments on AD for blade debonding on Robinson R22 and R44

FAA issues AD for blade debonding on Robinson R22 and R44
AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

SUMMARY: This amendment adopts a new airworthiness directive (AD) for the specified Robinson Helicopter Company (Robinson) helicopters. This action requires a one-time visual inspection for skin separation along the leading edge of blade skin aft of the skin-to-spar bond line on the lower surface of each blade and in the tip cap area. This action also requires a "tap test'' for detecting a separation or void in both bonded areas. This action also requires repainting any exposed area of the blades. If any separation or void is detected, replacing the blade before further flight is required. Thereafter, before each flight, this AD also requires checking for any exposed (bare metal) along the skin-to-spar bond line on the lower surface of each blade near the tip. If any bare metal is found, a mechanic must inspect the area. This amendment is prompted by 11 reports of blade debond, some occurring in flight causing the pilot to feel excessive vibrations and land, and some found during routine maintenance. The actions specified in this AD are intended to detect blade skin debond and to prevent blade failure and subsequent loss of control of the helicopter.

DATES: Effective January 18, 2008.
The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of January 18, 2008.
Comments for inclusion in the Rules Docket must be received on or before March 3, 2008.

ADDRESSES: Use one of the following addresses to submit comments on this AD:

Government-wide rulemaking Web site: Go to http://www.regulations.gov and follow the instructions for sending your comments electronically;
Mail: U.S. Department of Transportation, Docket Operations, M-30, West Building, Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590;

Hand Delivery: Deliver to the "Mail'' address between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays; or

Fax: (202) 493-2251.

You may get the service information identified in this AD from Robinson Helicopter Company, 2901 Airport Drive, Torrance, CA 90505, telephone (310) 539-0508, fax (310) 539-5198.

Ken Wells

6th Jan 2008, 19:51

Robo has also published a warning re flying R44's regularly out of balance; as the tail rotors have been known to delaminate following misuse by Radio Station Traffic ‘copters and Law enforcement choppers in the USA. New models have been upgraded.:8

lelebebbel

7th Jan 2008, 02:08

Do you mean this?
http://www.robinsonheli.com/srvclib/r44sa_avoid_out_of_trim_0607.pdf

this doesn't have anything to do with debonding. It's about T/R blades developing cracks from excessive stress due to flying out of TRIM.

Ken Wells

7th Jan 2008, 16:25

Yes that’s it.

You are right, “I stand corrected”, as the man said in orthopaedic shoes!

Ken:ugh:

EN48

10th Jan 2008, 17:51

From an email this AM:

In case you aren't aware, FAA issued an AD on all Robinson helicopters requiring an initial inspection of the main rotor blades for delamination effective 1/18/08 - subsequent to this inspection & prior to EVERY flight a rated pilot must make a maintenance log entry that the blade inspection was performed. Aside from satisfying Robinson's lawyers and making everyone's life miserable (pilots, FAA inspectors, etc.) - this AD has severe impact on student pilots (they aren't rated as outline in the AD) and legally will not be able to fly solo after 1/18!

Peter-RB

10th Jan 2008, 18:21

EN48,

Whilst I think it is good to have such info passed on, I think that Student pilots will still be able to fly solo, its just that the test must be carried out by a fully qualified Pilot, who in the most cases I could think of would be the Flight Training Establishments Fi or Cfi who would be a qualified and experienced pilot.

One thing also should be kept in mind and that is the preservatiion of ones own safety, many people who want to fly know a little about what could mechanically go wrong, but equally there are many who would not know how to conduct the " Knock or Tap test" to hear the subtle change of tone that could indicate any form of delam.
For I think the FAA have taken a bold step in putting out this AD, the thing is how will the RHC react to it will they be brave and make it world wide or will they as they seem to now and as in the past keep quiet and say Nowt,... except to blame the Pilot!!:ugh:

Peter R-B
Vfrpilotpb

EN48

10th Jan 2008, 18:33

Peter-RB,

The quote I posted above was from an email written by a high time Robinson ATP/CFII who I believe to be well informed. I have relatively little Robbie experience/knowledge, so cannot comment further.

ericferret

10th Jan 2008, 19:08

The initial inspection is carried out by an engineer.

The repetitive visual inspection is carried out by a rated pilot.

If it fails that inspection then an engineer is required to carry out the tap test.

I suggest that everyone should read the AD on the FAA's web site before signing anything.

The pilot certification called for in the AD is probably not valid in the UK, but a statement quoting the AD number and the sub paragraphs probably is.

I am sure EASA will clarify the situation!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!

ericferret

11th Jan 2008, 16:17

Given that UK non commercial (private )aircraft do not have a tech log and your aircraft log books might well be held by your maintenance provider where are you going to sign anyway?

500e

24th Jan 2008, 11:20

FAA Awards Airwolf Aerospace AMOC to AD 2007-26-12 on Robinson Rotor Blades
Wednesday, January 23, 2008 / Airwolf Aerospace

http://www.verticalmag.com/control/news/articlefiles/6510-logo_airwolf.gifAirwolf Aerospace has been granted an Alternative Method of Compliance (AMOC) by the Federal Aviation Administration for Airworthiness Directive 2007-26-12. The AD was issued for delamination of Robinson R22 and R44 helicopters’ main rotor blades. Installation of Airwolf’s Rotor Blade Protective Tape system is found by the FAA to provide a permanent and acceptable level of safety.
The AMOC permits all R22 and R44 operators to use Airwolf’s Rotor Blade Protective Tape which , eliminates the need for preflight inspections and entries into the aircraft’s permanent maintenance record, which would otherwise be mandatory under the requirements of the AD. The AMOC also legally eliminates the restriction on the installation of “blade tapes (anti-erosion tapes)”, which was recently added by Robinson to its Maintenance Manuals.
Airwolf’s solution STC-SR02491CH is a one-time application, using a unique adhesive polymer tape to prevent permanently the leading-edge skin debonding, which occurs when the bond line is exposed due to excessive erosion of the blade’s painted finish
“As of today, our Protective Rotor Blade Solution is the only permanent product on the market that is AD 2007-26-12 compliant”, says Jonny Quest, Airwolf’s technical director. “Now operators don’t have to go through daily blade inspections and can rely on an inexpensive and one-time application solution to a problem, which affects more than 2290 helicopters in the US alone.”
Robinson operators, mechanics and maintenance departments can order the Airwolf RBPT factory-direct at http://www.airwolfaerospace.com/ or at 800-326-1534, 440-632-5136s.

rotorcraig

26th Jan 2008, 12:59

The flying school that I SFH from are arranging briefing sessions with a qualified engineer for all of their PPLs.

They have a new sheet in the Tech Log to be signed before every flight confirming that a compliant check has been made.

They clarified this morning that I could fly locally if an instructor had checked the blades and signed them off, but I couldn't land away as I hadn't been briefed yet thus couldn't yet check for the return flight [under their local implementation of the AD].

Good point raised above regarding solo students. Expect solo circuits and solo nav are not a problem if an instructor checks before departure. But for solo land away (including QXC) does an instructor or engineer need to be on standby at each site to sign off every leg?

RC

generalspecific

2nd Apr 2008, 10:24

Its happened to our R44. Less than 200 hours total on the blades and we have to throw one away. Lives near the sea but always hangared and has a relatively quiet life. US$20,000 for a blade plus reattachment of our old spindle.

I know this has been brought up before but has anyone managed to get any warranty or contribution from Uncle Frank??

Also I saw a thread a while back on this airwolf tape.. is this preventative and repair?? anyone had any experience of using it??

g-mady

2nd Apr 2008, 10:34

So they dont cover you at 200hrs? How long is the warrenty, or are the blades not included at all?

MADY

TwinHueyMan

2nd Apr 2008, 17:54

Hey guys,

One of the choppers I fly had the blade paint slowly eating away, and during the 100 hour the mechanic cleaned it up nicely and painted it. Lasted for one flight, then wore off again. Painted it again, wore off again. We were unable to fly the thing half of the time due to this, until the mechanic apparently found something in the AD that says it is the mechanic's responsibility to monitor the blades, so thus put an update in the POH and required no pre-flight inspection. Met with an R44 operator in another state that had the same thing.

Anyone know the details on this little path?

Mike

Runway101

2nd May 2008, 04:27

Also I saw a thread a while back on this airwolf tape.. is this preventative and repair?? anyone had any experience of using it??

According to a couple of reports of users there is a downside of the tape, which is a performance decrease. The maker however, claims that there is no decrease in performance. RHC doesn't comment on the tape, but react more or less negative (I've spoken to Pat Cox at the factory, and some other Robinson fella at Heli Expo in Houston). This negative reaction might not be intentional but if Frank doesn't approve it it ain't good is their policy. They say you don't need the tape.

If you think about it, if you don't clean your blades, you have decreased performance. So if you apply the tape, you might end up with less performance too. The question is just how significant that is. In my opinion, good inspection and if needed repainting the blade does the trick. That's also what RHC effectively says.

Also, the new blades starting from a certain serial number are excluded from that new AD for blade inspection. According to Pat Cox at RHC, they make them differently and they use different materials.

firebird_uk

2nd May 2008, 09:42

Also, the new blades starting from a certain serial number are excluded from that new AD for blade inspection. According to Pat Cox at RHC, they make them differently and they use different materials.

I can confirm that. My R44 arrived late last year and the S/N is outside that covered by the AD and so the blades only need the standard pre-flight inspection. Let's hope they stay that way!

500e

23rd Jun 2008, 21:31

Have a read and the a think as to how to comply.
Robinson say you have to refinish blades if the paint is eroded Before the bond line is scoured, so if you re paint as required,then bond line cracks that the NTSB suggest you look out for are being covered with new paint, in some cases at very regular intervals.
A case damned if you do & damned if you don't.:{

http://www.verticalmag.com/control/news/templates/?a=7891&z=6

generalspecific

24th Jun 2008, 01:11

This is really becoming quite concerning. I had seen pictures of the peeled back skin of the Aussie 22 but I had no idea there had been in flight break ups. There goes my "worst case i'll get it back on the ground with a lot of vibration in time for a change of trousers" theory...

The statement that there were "obvious areas where skin debonded from the adhesive bond joint between the skin and spar were found on 10 main rotor blades on RHC helicopters" is interesting. Define obvious. Our 44 blades went back to Robbo recently and were deemed unfit and 20,000 USD later we now have a new set. TT for those blades just over 200 hours, but no waranty ?!?!

The NTSB goes on to say "bond joints are likely to degrade with time when subjected to harsh environments, such as the high humidity and high temperatures typically found at or near the sea".. so thats us screwed then as we sit in 40 degrees next to the sea...

Surely something has to change here above and beyond the development of a new super tap test (or whatever they come up with). Our ship is hangered and well looked after. Its a syndicate machine with a good bunch of pilots so its life isn't that hard.

Some may say who knows what happens unless you fly every hour your self but if the blades can only make 200 hours, then sea and heat and occasional rough handling or not there has to an issue with the manuacturing process.

I know there have been other threads on this but it would be intersting to see how many others have had to do blade changes (a lot I suspect) and how many had to pay (also a lot I suspect).

In my humble the R44 is the best value for money out there and does much of what the kerosene burners can do for a price that privates and mere mortals can justify. But the blade issue is taking some of the shine off....

500e

24th Jun 2008, 10:24

Is it that cheap with no real warranty! the factory appears to say it is the owners fault whatever (blades, starters, ring gear, corrosion, etc.) look at the threads.
I am not saying that any of the other manufacturers are better, but at least they don't sell on the premiss that they are cheap to run.
Time that owners got stuck in and called a halt, if you sell a helicopter to HK. it should be fit for purpose same as any where else.
Perhaps if they were stuck with the cost same a a recall on vehicles + loan machine:D

Runway101

24th Jun 2008, 11:53

Our 44 blades went back to Robbo recently and were deemed unfit and 20,000 USD later we now have a new set. TT for those blades just over 200 hours, but no waranty ?!?!

That is interesting. Where your blades the 'third set' in the following quoted paragraph from the article?

Two of the three blades had accumulated approximately 1,280 hours TIS and were not among the 10 blades found to have debonded between July 2006 and January 2007. Details of the third blade were not known at the time this safety recommendation letter was prepared. RHC had not reported new cases of a blade that was associated with debond between the skin and spar after January 2007.

If they are indeed yours, then strangely enough RHC couldn't recall that they had a TIS of less than 200 hours.

The article also doesn't explain why from a certain serial number the blades are deemed to be safe. No mention of a changed manufacturing process. If anybody can shed some light on this, I am lost with all the info available.

topendtorque

24th Jun 2008, 12:37

generalspecific

I suggest that this quote is rubbish

so thats us screwed then as we sit in 40 degrees next to the sea...

Re the trousers full, yes there were two in oz that we know that qualify, on the R22.

There was one on an R44 which was worse, blade delammed, and on the way down (the machine was on a power line inspection job I think) the machine hit one of the wires just enough to right the A/C before impact. If my hazy memory is correct they all got out. very lucky.

The story first put around was that the product was rubbish and we're all on a death wish etc.

but not so says the chinaman, it appears that investigation has revealed that the blade had been being over zealously polished with a power drill attachment, thus heating the skin edges too much for the glue integrity.

May i suggest that within your group that you check that none of your keen enthusiasts are using a power drill with a lapidary attachment (kid leather or some such) to polish the blades.

Just might be a clue, if not check for any other heating agent. I am positive that old 'sol' cannot be blamed.
tet

Runway101

24th Jun 2008, 17:03

it appears that investigation has revealed that the blade had been being over zealously polished with a power drill attachment, thus heating the skin edges too much for the glue integrity.

Do you have the NTSB (or other) number for this investigation? To my best knowledge, and no offense to you as experienced person, the only source of information about not using power tools on the blades is the RHC safety course. If MY hazy memory is correct, not because of an incident or accident, but because _after_ the blade SB was out, some people started to use power tools instead of sand paper before applying new paint to the blades and RHC put an end to it.

Again, no offense, and I am not trying to protect RHC, generalspecific or HKAC. I just heard that story from another source (Pilots Safety Course) in another version.

that chinese fella

25th Jun 2008, 02:43

Hey Runway,

The R44 Maintenance Manual, Chapter 9.130 CAUTION note says do not use power tools or chemical paint strippers etc etc.....

Runway101

25th Jun 2008, 08:00

Thanks, found it. Any idea on that accident with the power line inspection, that was apparently caused by using power tools on the blades?

All this attention that the RHC blades get is starting to worry me.

generalspecific

25th Jun 2008, 09:25

nope no one has been doing any funky polishing of the blades. I should clarify.. Engineer found evidence of debonding on the tap test sent it back to Robinson and they said new blade time.

Out of interest TOT why is my comment on the heat and the proximity to the sea rubbish?

My reference was in respect of the NTSB's suggestion that this was a set of conditions that was likely to lead to more early life blade failures and the fact that we are ..um.. near the sea and in 40 degree heat ;)

JimBall

25th Jun 2008, 10:53

This is all getting a bit cross-wired.

Yes - RHC have constantly told people not to use power tools for prepping blade surfaces. In any case, any qualified engineer would understand that the immense local heat caused by a power tool on any surface can cause heat damage. Let alone the effect on bonding.

Generalspecific's problem might be related to location. How often does the helicopter get left in extremely strong sunlight with no cooling breezes ? The surface temp of black metal can rocket in those circumstances, causing heat sink back into adjoined components and materials.

I would suggest that a full disclosure of the circumstances to both your RHC distributor and RHC would get their attention. Blades are covered by warranty - so there must be a reason why they feel yours don't get that cover.

topendtorque

25th Jun 2008, 11:40

Out of interest TOT why is my comment on the heat and the proximity to the sea rubbish?

My reference was in respect of the NTSB's suggestion that this was a set of conditions that was likely to lead to more early life blade failures and the fact that we are ..um.. near the sea and in 40 degree heat ;)

I am sure that what you are saying is quite true, but if a factory agent said that is why you have a problem with debonding then I say, he is talking rubbish.

If NTSB is saying that then it confirms what many of us already know. That is that many of their operatives would be out of place in a wheelbarrow repair station, let alone a modern helicopter's textbook.

Regularly helicopters in this neck of the woods during November sit in the bright sunshine all day at up to 50 degrees C free air temp, crank up and fly away with no problems.

If NTSB think that Robinson didn't take those temps into consideration when they were designing blades then they're not on this planet. Plenty of places in America where R44's might be operating where those temps would look like a walk in the park i guess.

I would think that there was a factory problem if you are operating at a cool forty degrees and the blades are debonding and there are no extraneous circumstances.

Salt air? forget about that, the blades are supposed to be sealed up with paint are they not, heavy gravelly dust or sand would be extremely more abrasive than a bit of salt. I guess with your ownership structure that the blades were regularly washed anyway.

I deliberately threw a line about the power tool to see if you may have had a underlying problem that you needed to take care of. No harm meant.

There have been some (R44 blades I mean) not far from here that were returned, I don't know how many were replaced FOC, however they first indicated the problem with an out of track problem that could not be rectified. I believe tha the tap tests were a bit inconclusive on some.

As Jim Ball says cover you claim with a stat dec if necessary, and certainly a defect report correctly set out and all signed up before they are packed off to the factory. Make sure that you separate the engineer who does the defect from the engineer who may represent Robinson.

A bit like selling cattle, work out first who is working for you the vendor and not the buyer.
all the best
tet

that chinese fella

25th Jun 2008, 11:47

I think that R44 MM reference I noted specifically mentions a temperature limit of 175 degrees Farenheit, but it was 10 hrs ago I read it so it kind of went into semi auto-dump in my mind........

[email protected]

25th Jun 2008, 19:06

TeT - it is the combination of high temperatures and high humidity that damages composite materials and their bonding agents. The comment about hot and wet is valid.

topendtorque

27th Jun 2008, 12:41

it is the combination of high temperatures and high humidity that damages composite materials and their bonding agents. The comment about hot and wet is valid.

I don't have any problem at all agreeing with that, as far as bonding agents go:

But, you tell me how the "wet" is supposed to get into where the "bonding agents" live short of faulty workmanship and I will then start agreeing with the wheelbarrow technician that Robinson blades aren't fit for the tropics.

I did have an idea that they are certified for all over the world operations.

ding ding, ding ding.

Gypsy_Air

27th Jun 2008, 14:02

Any ideas what the melting point is for the bonding material on the blades? It seems ludicrous that it would be low enough to be reached in the sunlight on a hot day. That would be a case of very bad design...

VfrpilotPB/2

28th Jun 2008, 08:23

Gypsy, its called "built in continuous profit maker for Uncle Frank" because of the power situation the blades need to be as light as a feather, but in doing this the inards are made of kitchen foil to resemble the home of a Bee, then they put some thicker kitchen foil over the top and stick it down with some strong glue stuff, when it gets hot and/or wet as well thats when chemistry starts to work on it and heyfranko there ya go again another customer damaged blade, ... that'll be £20k thank you.

solution heavy gauge Blades, so that needs more power from the mil, that needs stronger gearbox and bigger elastic bands, that needs a stronger airframe, that needs bigger petrol tank, that needs a bigger wallet !!

where do you stop this sort of problem, ... best go for a different make... but take your bigger wallet!

VfrpilotPb
Peter R-B:D

Gypsy_Air

29th Jun 2008, 19:45

That's either cynical or a scary thought... I know fridges have built-in expiry, but I don't like the idea of it when I'm 800 feet up in the air!
They've probably done about the best they can within the weight limits. That's the whole point and beauty of the Robbies.

topendtorque

30th Jun 2008, 12:28

I guess the cynical bit we'll all work out when we see a tube of vaseline supplied with the brand new helicopter.

Mind you, thinking of profit margins????

For Instance, none of the thousands of international customers have as yet seen from the grand gentleman - as part of their new machine kit - a US one quarter, or a definition of such to help them with their internationally approved Maintenance Manual which describes the mandatory tap test in detail.

Every other damm thing has to have a release note and a definition. - fuel - bolts - seat belts - etc.

Perhaps, we , yes, perhaps we will just have to supply our own lard.

I have heard that indeed there are to be new blades, which will descend to the other types from the goat stable, and surprise surprise, they will have the same alloy skins as from before the advent of the stainless steel blades

rotormatic

5th Jul 2008, 02:52

http://www.ntsb.gov/Recs/letters/2008/A08_25_29.pdf

Runway101

5th Jul 2008, 07:17

For Instance, none of the thousands of international customers have as yet seen from the grand gentleman - as part of their new machine kit - a US one quarter, or a definition of such to help them with their internationally approved Maintenance Manual which describes the mandatory tap test in detail.

The NTSB 6/2008 blade report: Papa Frank's US one quarter tap tests are useless.

topendtorque

5th Jul 2008, 20:17

thanks rotormatic for bringing that report to our attention.

very sobering, printed off after two reads .......??

all i can say at this stage is that the paint industry looks like doing well.

CYHeli

6th Jul 2008, 10:14

I am led to believe that the idea of the bond is to stick the two surfaces together and also to seal it. The paint also seals the surface and bond line.
So why is it so important to wash the blades prior to storage?
I can understand a chemical reaction (salt/sand/etc) leading to a degredation of the actual metal surface, but how does that lead to de-bonding?

topendtorque

6th Jul 2008, 12:48

You're onto it CY, there is a major problem with the underlying logic of the paper.

It seems to me that what they are trying to say is that there could be a breakdown in the integrity of the bonding within the blade structure, which causes a crack to appear on the outside, from the inside out.

Therefore there is need to establish an NDI test to detect the breakdown before either there is a crack visible or more seriously, a void occurs during flight which leads to cracking and catastrophic failure.

That I have no problem with, other than operating the product. although I must say the eyes get a bit tired checking the whizzing blade for cracks every time it goes by.

However, There is also a sweeping statement about "warm moist" environments, as if to indicate that is which causes a breakdown of the blade structure. As you suggest how can this happen through a sealed surface?

More particularly how can a moist environment lead to cracking which might happen with a structure that has become more brittle, due to say, drying?

Indeed what is the moisture content of the sealed bonding inside the product (blade) as it leaves the factory and as the hours tick down? Has there been a scientific measurement of that?

Now to digress, I think we all recognise that Al Gore is laughing all the way to the bank with his sweeping statements about climate change, but he and this "warm moist" statement have something in common.

It is that sweeping statements such as that should always be substantiated with scientific examination that had well documented replication and peer review, and they should never be made without them.

I look forward to a new ultra sound test procedure, the rest I think we can discard as rubbish. I have no problems with the suggested 10x visual inspections, although I've noticed that most junior pilots these days don't even know what a ten power is.

I worked out that the US quarter, is very similar is size and weight to our ten cent piece. Under the circumstances i'm not really into some tired joke about that worthless weight, especially after flying two of these blades all day.
tet

topendtorque

9th Jul 2008, 12:51

I'm a bit surprised that all of our operators, technocrats and voyeurs of robinson blades have let this NTSB bulletin go through to the keeper without even a decibel.
why, not even Nigelh has submitted a yawn!:{

ascj

9th Jul 2008, 14:02

after reading the report it makes me wish i were somewhere else in another type of machine. it does worry me however that perhaps the failure is started internally then the first failure on a blade with the new tape will be blamed on the tape and the problem remain unresolved. speculation i know but i am unconvinced that the paint maketh the machine..
and if it does then we are in trouble as were yet to find a paint that lasts 200 hrs!!

blakmax

6th Aug 2008, 10:00

Despite the derision shown on the pprune pages directed at the NTSB for Recommendations A08-25-29, the main cause of Robinson’s (and other manufacturer’s) bond failures actually is a combination of the manufacturing processes, high service temperatures and humidity. The problem is not related to degradation or brittleness of the adhesive itself. If weakening of the adhesive material or fatigue occurred, the failure would occur through the carrier cloth which is incorporated into the adhesive film by the adhesive manufacturer to enable the material to be handled without splitting. In a properly manufactured bond, this is the weakest plane in the bond, and if stress caused a failure, it should propagate thorough that plane. In many cases, bond failures have occurred at the interface between the adhesive and the metal. This means that the interface between the metal and the adhesive has degraded to a level where it is weaker than the plane of the carrier cloth.

Adhesive bonding relies on the formation of chemical bonds at the interface at the time of manufacture, between the adhesive and (usually) oxides and hydroxides on the metal surface. With even moderate levels of processing, it is possible to develop bonds which are sufficiently strong in the short term to pass testing. However the performance of those bonds over time depends on the resistance of those chemical bonds to degradation in service, and the most common form of degradation occurs when the oxides hydrate. For the metal to form a hydrated oxide the chemical bonds between the adhesive and the metal dissociate, leading to degradation of the interface. Chemical treatment is required at the time of manufacture of the bond to prevent hydration in service. This type of failure is characterised by an absence of adhesive on one of the bonding surfaces.

Now in some cases, there is what is termed a mixed-mode failure, where some of the adhesive fractures and some of the interface fails. This is typical of a bond that has gone part of the way down the path of degradation and the blade experiences some stress that exceeds the strength of the remaining bond. The longer the time since manufacture, the more that hydration occurs and the weaker the bond becomes.

Moisture is absorbed by ALL epoxy materials by diffusion, and paint simply slows down that diffusion process. It is that absorbed moisture which attacks the interface, causing hydration. High temperatures and high humidity accelerate the absorption process, and so they accelerate the degradation process. Hence, the NTSB findings are correct. The real solution to the problem is contained in the other NTSB recommendations where they suggest amendment of the Advisory Circulars to require all manufacturers (not just RHC) to demonstrate bond durability as part of the certification basis for the aircraft.

To satisfy Topendtorque's stated criteria, I am a scientist, this material has been published and has been subject to peer review.

RotorSwede

7th Aug 2008, 12:14

I'm worried.

So the R44 has blades with sub-standard quality and no certain method of detecting the faults ?

Shouldn't the entire fleet be grounded until a method of discovering the faults has been implemented ?

It's just a question, looking forward to the inputs from more experienced pilots and mechanics.

RS

topendtorque

7th Aug 2008, 13:20

Thanks Blakmax for that illuminating info.
I had thought that an ultra sound test might be developed as it had been for other serious issues at short notice, such as the '47 M/R grip for example.

Then I read "rotor swedes" post and thought, hey, if the common acoustic based tap test doesn't work, then how would any sort of sound frequency work?

It is amazing what can be seen inside one's stomach for sure but when you try the same stunt on a cow and encounter surface hair, even lacquered well down with gel, or inside open spaces then it is very difficult.

Maybe that would be the case with all of the little space pockets inside the bonded area?

It is still a tough call to suggest that an approval on a blade structure for a certain life is suggested now to be suss, perhaps well before its time.
Are you absolutely positive that such blade failures, or suggestions of impending ones, are not prone to a faulty manufacturing creep.

one thing I have noticed and that is the original issue paint on many Robinsons seems to be much more durable than any alternative. why is this so? it seems a bit like the factory fitted tyres on your new motor-car that always last heaps longer than any replacement.

I guess that you are saying that the hydration only occurs after the moisture penetrates in a plasma like fashion at the fluctuating and perhaps quite high hydraulic pressures that must occur out toward the fast tips. albeit on the higher pressure underside of the blade.

I would have thought that there would be a permanent gas insulation within the blade caused by diffusion which might have worked as a preservative and a barrier to the hydration, had the water been kept out, so to speak.

I always think of diffusion that causes that grey fog, just before daylight that seems to preclude ones ability to easily find the master switch. although it seems to be dissipating with age, maybe there is less grey matter for the alcohol molecules to randomly collide with or maybe the habits are more entrenched.?
tet

cockney steve

8th Aug 2008, 10:51

Slightly off-topic and in reply to the last poster (E.T. ,-#185)

eVEN MORE DISTURBING WAS THE SAGA OF THE "MINI 500" Fortunately for UK pilots, this was never approved, but in the US, it was allowed to be sold with reckless impunity into a totally unmonitored and unregulated environment :eek:

Darwin had a field-day with that thing! (It has to be said, that with development, it could possibly have become acceptably reliable and safe.-an unused kit recently appeared on Fleabay-listed as being in Germany.

Rotorway has also had it's problems,but i'm still baffled by the huge wedges of cash that people are prepared to pay to be test-pilots in marginal machines.

That said, the Robinsons would appear to offer the optimum "bang for the buck" in rotary-wing flying. Each pilot assesses his own risk-acceptability-level.

Would I take a ride in a Robbie?- probably!
Would I ride REGULARLY in one?- NO!...the odds would shorten to much for me!

Runway101

9th Aug 2008, 02:12

Would I take a ride in a Robbie?- probably!
Would I ride REGULARLY in one?- NO!...the odds would shorten to much for me!

What would you say if being in a Robbie would be the only way to be in the air for you? Say all your money is only enough for a Robbie or a Rotorway or something like this?

deeper

12th Dec 2008, 03:06

this machine is privately owned and has done only 400+ hours in two years.

http://www.bluetonguehelicopters.com.au/pprune/0001.jpg

http://www.bluetonguehelicopters.com.au/pprune/0002.jpg

http://www.bluetonguehelicopters.com.au/pprune/0003.jpg

Hughesy

12th Dec 2008, 23:24

After a recent fatal R22 accident here in NZ, one of the theorys is blade failure at the hub. Been a few of these world wide. Now being NZ it will take at least 8 months or more for the report to come out, so it is just a theory, but a sound one.

Whats an easy way of getting a R22? Buy a peice of land and one will eventually turn up. :ugh:

topendtorque

13th Dec 2008, 11:56

A revealing photograph, in more ways than one. Going for warranty is it?

http://www.bluetonguehelicopters.com.au/pprune/0001.jpg

500e

13th Dec 2008, 13:41

Looks like the paint was lifting along the whole end of the lower surface, how far has the paint erosion gone is it just the colour or the primer, looks like colour only.
Was it a tap test or did the Paint lifting give it away? would have thought the lifting paint should have been noticed before it got so far???.
But still with only 400 hours not good would be real :mad: if it was mine

generalspecific

2nd Sep 2010, 03:38

Ok now we are starting to get a bit sick of this... We have just had our 4th blade delam!

2 R44's one with about 1,600 hours, now one with about 300 hours and 2 R22's one with around 1,200 hours and one with only 320 hours.

Anyone got any thoughts on how to get Robbo to start dealing with this. Hot and humid is clearly killing the baldes. One was a training macine and one was imported from the US so you could make the hard life argument possibly. But one of the low hours 22 and 44 were private machines flown by a limited number of cautious pilots ans the paint was well within the bond line limits with no refinishing ever done etc...

Any one with any posiitive experience from Robinson over warranty?

Ian Corrigible

2nd Sep 2010, 04:14

Stark conclusion from the investigation into last November's R44 crash in Israel (http://www.pprune.org/rotorheads/397287-israel-helicopter-crash-post5349235.html).

Main rotor blade failure caused R44 crash
Flight International (http://www.flightglobal.com/articles/2010/08/11/346036/main-rotor-blade-failure-caused-r44-crash.html) 11/08/10

The fatal crash of a Robinson R44 helicopter (4X-BDM) in Israel in November 2009 was the result of the failure of one of the main rotor blades, according to the report of the Israeli air accident investigator.

Yitzhak Raz, the chief accidents investigator in the Israeli ministry of transport, says the failure was caused by a combination of erosion where the outer skin of the blade is connected to the blade's main spar, and separation of the skin from the "honeycomb" filling.

Raz says: "This combination caused the sudden separation of most of the blade's skin from its spar." The loose blade then cut through the tail assembly of the R44, separating it from the fuselage.

The report suggests: "There is real probability that some of the similar accidents in recent years that involved that type of helicopter were caused by a similar failure process."

The R22 and R44 have suffered multiple accidents, especially in their early days, involving the main rotor damaging the tail boom, but this was often attributed to the intolerance of the design to rapid movement of the cyclical control, which tended to destabilise the rotor blades of these very lightweight types.

Such events were often linked to the use of the types for training, or by entry-level owner/pilots who did not make allowances for this vulnerability.

All on board the helicopter were killed when it crashed into the Mediterranean.

I/C

delta3

2nd Sep 2010, 19:43

Talked to a "pitting corrosion" expert recently and without knowing the specifics of the R44 inox blades his first gut reactions were:

-> bonding agents + moisture = turns acid

-> acid for many forms of inox = etches the iron away and creates pitting corrosion

-> pitting corrosion compromises the bond

So he needed no big research study to conclude that the inox choice was perhaps not the best choice...

At least I conclude that we have to keep water away from the bonds, which is off course easier said then done in some regions/seasons.

d3

delta3

2nd Sep 2010, 20:00

I/C (some thread creep..)

Why does the "expert" has to bring up "populist messages" like

"The R22 and R44 have suffered multiple accidents, especially in their early days, involving the main rotor damaging the tail boom, but this was often attributed to the intolerance of the design to rapid movement of the cyclical control, which tended to destabilise the rotor blades of these very lightweight types."

I thought people finally understood what theethering rotor and low center of gravity meant. The R22/R44 are not the only theethering ones, cfr the passionate discussions with Lu. Rotor blades are as I extensively showed not destabilized at all, it is just the dynamic interaction between a very stable rotor disk, and less stable trailing body that has to be understood.

d3

helisphere

16th Dec 2010, 21:59

So I read through most of the posts on this thread but I didn't see a clear answer to this question: Is this delam/debond problem only a problem on the steel skin blades? Did the older aluminum skin blades have this problem??

topendtorque

17th Dec 2010, 09:33

Did the older aluminum skin blades have this problem??

not that i recall.

Keepitup

17th Dec 2010, 11:52

You could always try the new -7 blades for the R44 and see how that works, I know it doesn't help with the expense of the other blades, but they might help?

http://www.robinsonheli.com/srvclib/r44sl37.pdf

Keepitup

Shawn Coyle

17th Dec 2010, 14:29

61 Lafite

17th Dec 2010, 21:54

I've heard a rumour (since this is a rumour forum...) of a solution using specially shaped tape that eliminates the performance penalty normally associated with blade tape.
When I know more, I'll post something.
There are many solutions to different problems or perceived deficiencies on Robinsons, and after understanding Frank's philosophy with the aircraft, and his focus on simplicity, I keep coming back to the same thought:

...if it was straightforward to fix, or necessary to change the aircraft so it will safely operate within the published envelope, wouldn't Robinson have done something already? They seem to have done where it matters, with ADs - fuel pipes, fixes to things that might breaklike collectives etc wherever a fundamental flaw is found. The blade solution is there: paint them if they erode, replace them if they go too far or fail a tap test.

But we also get solutions not authorised by the manufacturer, potentially authorised by aviation authorities, which sell in relatively small numbers, and where the risk cannot have been as well assessed as if they were sold by the factory.

It seems to me that the risks of putting these unauthorised (by the manufacturer) modifications on to the aircraft far outweighs any benefit. Yes, even though it's $50k for a set of blades! Helicopters cost a bundle, and as soon as you start looking for where to cut corners on parts, safety is compromised: nothing compares with all new parts purchased direct from a Robinson source, fully QA'd coming out of the factory. Use it till it wears out or needs replacement and buy another new one from the factory.

If the factory tells you what to buy (e.g. oil type, 100LL) then buy exactly that. If the factory doesn't say to stick it on their helicopter, then don't!

Why do so may people - many of whom will never use the aircraft for anything remotely challenging like utility work, long line etc which might require specialist configuration - think they know better than the factory what should and shouldn't be on the aircraft?

... heading for the bunker now....it's radical (and expensive!) to think this way....

Lafite

blakmax

17th Dec 2010, 22:01

Helisphere

I have examined a number of blades and at least one steel blade exhibited interfacial failure (separation of the bond at the surface of the metal, rather than a fracture through the adhesive layer) with separation at the surface of the spar, as well as the skin. Hence, it would not matter what the skin was made of if the failure is occuring at the opposite side of the adhesive layer to the skin material.

I am greatly concerned by the use of tapes to address this issue. While I have observed some limited evidence of undercutting at the blade tip due to erosion, I disagree that this is the cause of the bond failures. The erosion may exacerbate the problem and accelerate the process, it is highly improbable that such failures would occur at the interface unless the interface was already degraded and the bond was weaker than the strength at original manufacture. Placing a tape over the area will not prevent interfacial degradation and worse yet, will prevent visual inspection of the blade for disbonds. It is a bit like applying another layer of paint without first removing the corrosion.

The interfacial separation I have observed also occurred at a number of sites well away from the blade tip, so covering that area with tape would not influence erosion greatly but would severely inhibit visual inspection.

There is more information on this type of bond degradation issue at Publications - Max Davis - Adhesion Associates (http://www.adhesionassociates.com/publications.html) The paper is Assessing Adhesive Bond Failures: Mixed-Mode Bond Failures Explained (http://www.adhesionassociates.com/papers/56%20Assessing%20Adhesive%20Bond%20Failures%20-%20Mixed-Mode%20Bond%20Failures%20Explained.pdf)

Regards

Blakmax

lelebebbel

17th Dec 2010, 22:30

The blade solution is there: paint them if they erode, replace them if they go too far or fail a tap test.

Surely you can't be serious. Have you had a look at the pictures a few posts above yours? 400hrs, paint well within limits - unservicable. How can that possibly be called a solution?

61 Lafite

18th Dec 2010, 13:43

Surely you can't be serious. Have you had a look at the pictures a few posts above yours? 400hrs, paint well within limits - unservicable. How can that possibly be called a solution?

I can absolutely be serious, and look at the paint that you say is 'well within limits' - it's all flaking off the end of the blade - how can you possibly call that 'paint well within limits'?

There is no way that just happened in one flight before the problem was noticed.

The SB/AD info from Robinson is very clear: if there's a problem with the paint, it needs to be sorted out, otherwise delamination may happen.

Here you see a problem with the paint, and delamination has occurred.

When you buy your aircraft, you get 2 years warranty. After that, all you know is that a lot of research and development has gone into making the machine as durable as possible, but while many, in fact most, parts on all the aircraft will go all the way to TBO, some won't. It happens on engines, pumps and, under some circumstances yes, paint and even blades. Check the statistics - not much normally goes wrong. If Robinson had it their way, they'd be using a better primer, but legislation won't allow them.

Go to the safety course, and the unofficial advice? if your blade has paint problems, for god's sake don't buy primer from us - use the old stuff we're not allowed to use!

If you want a machine with a 12 year warranty on all parts irrespective of operating environment, then not only shouldn't you buy a Robinson, I'm not sure there's any aircraft out there you should buy. Yes, it sucks, but hey - these are aircraft and ownership can suck big time. Ditto boats, and (if you remember the rhyme) women :}!

I'm not unsympathetic to the costs, and neither are Robinson, as I believe some assistance does sometimes appear to people who get these problems at low hours. Virtually everyting manufactured on the planet has a small percentage of issues. People need to learn to live with that uncertainty, and manage it with the manufacturer's assistance as best they can.

Lafite.

topendtorque

18th Dec 2010, 13:48

these are aircraft and ownership can suck big time. Ditto boats, and (if you remember the rhyme) women http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/badteeth.gif!

we're all ears there, :ok: Lafite ol' son

Sam Rutherford

18th Dec 2010, 14:40

"performance penalty normally associated with blade tape."

Tell me more about this - I thought the negative effects were minimum to the point of undetectable in flight.

We're looking at the pros/cons of blade tape for our desert operations.

Thanks, Sam.

Nubian

18th Dec 2010, 15:27

Sam,

Our technicians used a bladetape from 3M, which worked wonders reducing leading-edge-erosion on our blades.
Now, operating in the desert of Libya, you should be prepared to change it within 25 hours or so, but the clue is to not use one long tape, rather cut it into 1 meter bits or so, and change the appropriate bit as it starts to bubble/loosen. Easily detected when preflighting/walkarounds between flights, and you might hear it during flight.
It will save you a lot of hassle/work and lots of $$$ in less wear on your blades.

As for performance, I think that must be practical next to nothing when(in the practical world), but I'm sure in the theoretical one will give you slightly less performance. Haven't ever seen any difference at least.

Good luck with the planning and trip!

cheers

500e

18th Dec 2010, 21:37

3M tapes
Erosion Protection (http://solutions.3m.com/wps/portal/3M/en_US/Aerospace/Aircraft/Prod_Info/Prod_Catalog/?PC_7_RJH9U5230GE3E02LECIE20Shttp://lOG5_nid=61XB41ZN6Jbe90657JDCX3gl)

HONTEK appear to make a product that is the last word in erosion protection!
read the blurb, then try and get product:(:(:(, ( have been trying for 18 months) was told no way to do in field, send blades to Karmen Helicopters it is not a field product, yet they are saying repair re treat blades as required.
HONTEK CORPORATION - Sand and Erosion Protection - Welcome (http://rain-sand-erosion.com/index_2.html)

HONTEK CORPORATION - Publications Downloads (http://rain-sand-erosion.com/pd.html)

helisphere

20th Dec 2010, 05:21

So when an aircraft goes down from a delamination/debonding blade, can this be difficult to tell whether the delamination was actually the cause? I just wonder about some of these accidents that are caused by a divergent main rotor for no apparent reason. Is it at all likely that a delamination could be the cause of the divergent main rotor in these accidents?

Arnie Madsen

20th Dec 2010, 06:11

Can anyone name another manufacturer of bonded metal blades that has a similar history of ongoing problems .? I am not aware of another. Thanks.

blakmax

20th Dec 2010, 10:17

can this be difficult to tell whether the delamination was actually the cause?

Helisphere

Thank you for taking the time to read the paper.

It is possible by visual inspection to determine the type of bond failures present, and there are essentially two types: Cohesion, where the adhesive is fractured and residue remains on both surfaces, and adhesion, where the adhesive separates from one surface. Most structural film adhesives contain a "carrier cloth" which is a supporting cloth added during initial adhesive manufacture to aid handling. Cohesion failures usually fail through the plane of the carrier cloth because this is the weakest plane in the bond, provided the interface is strong. Cohesion failures require higher loads than adhesion failures, and in extreme cases adhesion failures can occur with very low loads.

Adhesion failure is caused by time-dependent degradation of the chemical bonds at the interface between the adhesive and the substrate (in this case the metal). The bond may start off with a high strength but over time the strength decreases, and usually the mechanism is that the surface of the metal forms a hydrated oxide and in the process the chemical bonds between the metal and the adhesive layer dissociate to enable hydration to occur and disbonding results. Failure naturally occurs at the weak interface, so all the adhesive remains on one surface and none on the other.

There is a third possibility; that failure occurs before the interface is fully hydrated, and this results in a mixture of cohesion failure and adhesiuon failure, commonly termed "mixed-mode" failure. The proportion of adhesion failure will increase with time as the interface hydrates, so if the structure is highly loaded at an early stage, the failure load will be higher and the proportion of cohesion failure will be higher. The converse is also true, such that the longer the bond is in service, the weaker it becomes, so failure will occur at a lower load and there will be a higher proportion of adhesion failure, and the locus of failure will migrate from the plane of the carrier cloth towards the interface.

The rate of strength loss depends upon a number of factors, the most important of which is the process used to prepare the surface during the factory bonding process. If the process produces chemical bonds which resist hydration. then the bond will last a long time. If not, then a shorter life will result. Other factors include higher operating temperatures and humidites, both of which will accelerate the hydration process and hence shorten the service life of the component.

Now, of all the tip disbonding examples I have seen there is a high percentage of adhesion failure. Erosion by itself can not cause adhesion or mixed mode failure in otherwise sound adhesive bonds. Hence, the entire discussion about which tape to apply is meaningless unless the bond failures are confirmed as pure cohesion failures.

I have also observed adhesion failure on one crashed blade at a number of locations well inboard from the tip where erosion is not evident at all. (Release of the report from a certain Pacific country is being delayed internally.)

The real problem is that it is remarkably difficult to categorically point to a disbond and say that this was without doubt the absolute primary cause of the accident. This is because even though the bonds exhibit failure modes which are characteristic of low bond strength, the loads which caused that specific bond to fail may well have been associated with an event which occurred as a consequence of another causal event, but equally they may be the causal event. There is rarely any marker such as fatigue striations to give a definitive identification. Occasionally, there is discolouration of the adhesive due to the presence of liquid water, and this would positively indicate a pre-crash defect.

Hence, it is necessary to eliminate or ameliorate all other probable causes and to look for circumstantial evidence to support the hypothesis that bond failure caused the crash. For example, if the pilot had thousands of hours with that type, had a perfect medical record and post-mortem assessment confirmed the absence of alcohol or drugs, then it is reasonable to suggest that the probability of inappropriate pilot control input is extremely low.

Naturally, weather conditions would be taken into account, as would mission profile. If the aircraft was flying level on a set and commonly used transit route on a bright sunny day with no cloud and low winds, then it is reasonable to infer that weather and flight mission were not a factor.

Extraneous causes such as bird impact or impact with items departing the aircraft would also need to be eliminated.

Next you would examine other causes which may result in a loss of blade tracking. Most of these leave tell-tale evidence, so if that evidence is absent, then it is possible to suggest that the probability of those causes is low.

Next you would examine all bond failure surfaces. All cohesion failures can usually be discarded because the bond would have exhibited an adequate strength. Adhesion failures are important because they often indicate a defect which existed before the crash event. For mixed-mode failures, the proportion of adhesion failure AND the proximity of the failure surface to the interface are both strong indicators of weak bonds. (Often safety investigators use a scanning electron microscope to find the presence of ANY adhesive and incorrectly identify that as a cohesion failure.)

Next, you would look for any history of bond failures in the specific component, and in the case of R22/R44 there are a number of examples where aircraft have landed or crew have survived crashes with tip disbonds. If then, the component in question exhibits characteristics of bond degradation and hence a loss of bond strength, then the probability of bond failure causing the event increases. If the extent and distribution of bond degradation is high, then so is the probability that bond failure was the cause of the event.

Then it comes down to a balance of probability that bond failure was the cause and not the result.

Regards

Blakmax

61 Lafite

20th Dec 2010, 11:02

A very interesting summary, blakmax.

The FAA notice on the blade AD in 2008 quoted on about page 8 of this thread notes:

This amendment is prompted by 11 reports of blade debond, some occurring in flight causing the pilot to feel excessive vibrations and land, and some found during routine maintenance.

I didn't see anything in it stating that there was any evidence of it being a factor in any fatal (or non-fatal) accidents. The Israeli report stated

There is real probability that some of the similar accidents in recent years that involved that type of helicopter were caused by a similar failure process.

(I note also that it mentions erosion as evident on the disbonded blade). I find it hard to reconcile these two: I have no doubt the Israeli investigators have done a thorough job, as have the US investigators on all the Robinson accidents in the US.

However if there really were a 'real probability' that similar disbonding had caused fatal accidents, why has it not been recorded as a possible factor far more frequently than we have been hearing about? A 'real possibility' maybe, but one missed by all other accident investigators.
For me, this is very pertinent to Blakmax's last sentence:

Then it comes down to a balance of probability that bond failure was the cause and not the result

Can any significant number of other accident investigators all have been mistaken in not even quoting this as a possible factor, and if we assume thay all did the highly professional job we know they all do, I find it hard to accept the 'real probability' the Israeli report suggests.

Lafite

Shawn Coyle

20th Dec 2010, 11:33

There was an accident in the Caribbean that was most definitely blade debonding - only the spar remainded on one blade.

As for debonding not being mentioned in other reports - accident investigators are human, and sometimes go off on tangents and miss the real cause of the accident.

Hughes500

20th Dec 2010, 17:03

Blades tape does make a difference to performance. In an OH6 the manual states that if blade tape is fitted ( doesnt say how much) that is equivent to an extra 70lbs on auw !
On my 500's if you polish the blades having cleaned them really well the machine will go about 5 to 6 kts faster. If you dont believe ask a glider pilot about unpolished wings or dirty wings on a glider ! was scepticle about it til I tried it !

500e

20th Dec 2010, 17:16

Hi BM Another interesting read.
I do not think the tape enquiry was really to do with the dis-bond, rather that Frank keeps saying dis-bonding is due to paint erosion on leading edge joint, this would at least reduce this argument from the factory & make it harder for them to reject warranty support.
If the Hontek product works as advertised, it would be a cheap cure rather than paint every X hours & low blade life.
Hi H500how are the Xmass lights

blakmax

20th Dec 2010, 19:12

why has it not been recorded as a possible factor far more frequently than we have been hearing about?

There are a number of reasons why this type of failure has not been reported in other events. Firstly, many safety investigators are ex-pilots and tend to focus on what they are familiar with.

Next, most investigators would not encounter a sufficient number of bond failure causal events to establish an adequate level of expertise in identifying the specific characteristic of a bond failure.

Thirdly, to my knowledge there is no formal training available in adhesive bond failure forensics, and much of the knowledge base is grandfathered within the investigative organisations and that embeds and propagates false knowledge (which is why some investigators use SEM to find the minutest trace of adhesive and then classify the failure as cohesion).

Fourthly as I have said in other postings, there is a deficiency in the FARs and JARs in that there is no mandatory requirement to demonstrate that an adhesive bonding process produces hydration resistance, and what guidance there is in AC 20-107 is weak and only came into existence a few years ago. Hence, there is no regulatory and minimal advisory guidance to the investigator to assist in focussing on that type of bond failure.

These comments are not intended to reflect on the integrity of safety investigators. They simply have not had training and exposure to bond forensics. I am sure that a similar lack of knowledge will come to light when we start to see failure of fibre-composite structures.

Regards

Blakmax

delta3

20th Dec 2010, 20:00

Blakmax

is there a "easy" explanation why hydration weakens the mechanical bond? Is it for instance the mechanical strength of Al2O3 versus AL(OH)3 or is it changes in the bonding bridges?

d3

Hughes500

20th Dec 2010, 21:02

500e

Mrs 500 wants to know why I want to purchase 200 m of Xmas lights, the expression " dont even think about putting them on the house" was the polite reply !!!!!!!:eek:

500e

20th Dec 2010, 21:22

Flashing perhaps :E
Don't suppose I will be welcomed for tea & toast again

blakmax

20th Dec 2010, 21:41

Delta 3

The mechanism for aluminium materials is that Al2O3 has an affinity to form bohemite Al2O3.2H2O. It takes less chemical energy to form that hydrated oxide than it does to maintain the chemical bonds to the adhesive, so hydration wins. In the case of the R22/R44 blades, the materials are stainless steels, so naturally the reactions will involve hydration of ferrous/ferric oxides.

I sympathise with 500e. My place is used as a visual beacon because of the christmas lights. I want to start the movement to stuff the Easter Bunny down Santa's throat and fix two problems at the same time!

topendtorque

20th Dec 2010, 22:05

accident investigators are human, and sometimes go off on tangents and miss the real cause of the accident.

one will go a long way to better this clinically correct statement, at least here in oz anyrate.

such demeanours are acceptable, IF the system has within it a fool proof device of peer review, as they can usually be overcome.

here we notice that when a mistake is made by ATSB they defend , it , at , great , length .

in the process of consequental actions there are then often, affected family members, workmates and personal and company budgets that are severely disjointed and who come away from the process feeling utterly devastated and with the feeling that ATSB couldn't give a f''k.

like hospitals, they specialise in burying their mistakes.

as for this,

Can anyone name another manufacturer of bonded metal blades that has a similar history of ongoing problems .? I am not aware of another. Thanks.

i think there is one example, indeed that I have seen on these pages here, but in defense of the topic, so far I only hear the periodic creaking of the rocker, not the tapping of the keys.:) it may have been back in the days of fabric, so not as close to the money.

helisphere

21st Dec 2010, 03:05

Blakmax
Thanks for all the info, yes, I finally read the paper.

So I wanted to clarify a couple things and just make sure I have this right.

1. We are basically talking about adhesion and mixed failures if the bond is the problem? Because if we are talking about cohesion failures then the bond remained strong and the disbond failure was most likely a result of something else loading the blade beyond the design limit?

2. If the blade passed some kind of initial structural or NDI test out of the factory then it is assumed that for a non-cohesive failure, the bond degraded over time due to hydration?

The rate of strength loss depends upon a number of factors, the most important of which is the process used to prepare the surface during the factory bonding process. If the process produces chemical bonds which resist hydration. then the bond will last a long time. If not, then a shorter life will result. Other factors include higher operating temperatures and humidites, both of which will accelerate the hydration process and hence shorten the service life of the component.

Now, of all the tip disbonding examples I have seen there is a high percentage of adhesion failure. Erosion by itself can not cause adhesion or mixed mode failure in otherwise sound adhesive bonds. Hence, the entire discussion about which tape to apply is meaningless unless the bond failures are confirmed as pure cohesion failures.

3. Hydration can be slowed down but not eliminated and you are saying that the most important way to slow this down is proper surface prep? But you are saying that the paint covering the bond line does very little to prevent hydration? And are you also saying that an exposed bond line will not appreciably accelerate hydration of a well prepared and executed bond?

Please make sure that I am thinking of all this correctly.

blakmax

21st Dec 2010, 06:11

Helisphere

Cohesion failures are not usually a problem because the bond should have passed initial certification and the nature of cohesion failures is that they would have achieved the required strength. The exception is if the bond has micro-voids as I suspect occurred in the AW139 failure at Doha, discussed eleswhere.

The problem with QA testing is that it is undertaken before the bond has had time to hydrate, so a good result usually always occurs. NDI will only detect voids in the bond. It can not interrogate the condition of the interface, so it does not provide assurance of a good bond, it only tells you if you have a bad bond. Worse yet, all of the inspection criteria for in-service disbonds are set on the basis of tests with artificial defects embedded in an otherwise good bond. The surrounding adhesive has not had time to hydrate before the test, whereas if you get the same size disbond in service, the surrounding bond may be hydrated and may be weaker than that tested during certification.

Hydration can be eliminated by use of surface preparation methods which have been validated using specific tests to demonstrate resistance to hydration. Such processes eliminate hydration and hence eliminate adhesion and mixed mode failures.

An exposed bondline will absorb moisture faster than if it is painted. However, paints and sealants only slow down, not prevent moisture diffusion. We are not talking about free liquid water, it is the microscopic moisture which is absorbed by most polar molecular structures (such as epoxies). This eventually reaches the interface and causes hydration.

Regards

Blakmax

topendtorque

21st Dec 2010, 11:36

very interesting, certainly the surface erosion behind the bond line will be averted to a great degree by the paint that we talk about. even the blade tape, but you have convinced me that blade tape would only be a last stop defence in a very erosive environment, however;

what would be the cost to go one step further with the R44 blades (say) and fill them with an inert gas?

or would the natural egress through the paint etc by the water vapor not warrant it?

i would assume that the usual incursion of water vapor is from the open end of the blade when they are static and then some interesting hydraulics when they are in motion?

500e

21st Dec 2010, 22:15

BM
Is there any mileage in some form of electro-osmosis, such as in some damp courses.
Keeping gas in would be a problem due to temp variations I would think, & blade flex could make it a :mad: to seal
OK got my coat all ready & preparing to leave.

blakmax

22nd Dec 2010, 00:10

Guys, adding an inert gas would be futile because it would almost certainly leak out.

The solution is not to attempt to keep the moisture out, it is to treat the surface chemically during manufacture so that it does not hydrate in service. There are a number of processes which achieve this.

Now that doesn't help much if the process used to make your blades was not hydration resistant. (I can't comment on RHC's specific processes because I don't know what they are.) The only option is to rigorously follow the ADs and service bulletins, in particular with regard to tap-testing and visual inspection. I personally place more weight on the visual inspection, and I would prefer to see another more reliable inspection method such as acoustics or thermography used rather than tap testing. I would treat ANY disbond with suspicion, even if it is within limits.

Regards

Blakmax

fdr

3rd Jan 2011, 04:15

Hi.

The US-Army indeed did a study on the effects of blade tape application on the OH-6 Cayuse in the early 70's which had interesting results. The values of degradation were in the order of 4%, for tape.

The reason for the performance loss may not be fully explained in 2D studies but is rather evident when evaluated in 3D experimentation.

(IMHO):

A simple experiment can be conducted by just reviewing the wind down time of modified v unmodified blades. From normal Nr, close the throttle and time the decay period to reach a given Nr. Note that the application of blad tape increases total inertia by a small amount, (as is also increases radial shear, flapping and feathering inertial moments). Notwithstanding that "increase in inertia" from adding tape, the time interval, tau, will be shorter for the blade with a normal blade tape added. This test is moderately sensitive to environmental conditions, and control position, so ensure you maintain a repeatable position of the controls.

Take away point: If your response time was short before in the event of a power loss to achieve autorotative conditions, it has just been eroded further by conventional blade tape.

performance shifts of L/D will affect the following issues:

Tau, response time in the event of power loss
Nr recovery in flare
Nr decay rate post flare
torque demand through the power train
TR authority
ROD in autorotation

Does erosion protection improve the life of R22/44 blades? Open question, and the discussion on this forum has covered the issues quite well. Erosion of the PPS will allow moisture ingress if the structure was not well manufactured... and that remains the basic issue that the applicable AD refers to.

Coning Angles: The R22/44 blade bending loads are not significantly altered by coning angles per se, the hinge relieves bending loads. The greatest contributor of bending loads are associate with span wise non uniform random excitation, occurring in high speed forward flight primarily and during high rate manoeuvring, or through BVI and similar unsteady effects. (not the case for the B-206 and similar configurations... where low Nr will result in high bending loads at the root that are not relieved).

I think Shawn may be referring to my work re blade tape....

I have been conducting flight tests for over a year of a blade tape system that does improve the L/D of the blade, significantly so. It results in lower torque requirement for a given performance, and improves TR control authority, autorotation. The tape is protective of the leading edge, and is clear, allowing visual inspection of the blade surface. Erosion protection is moderate in sand and good in rain. certified performance values of the helicopter will not be changed, but the operator will note a change in power demand. It is the intent to add safety margin, not utility, and to reduce maintenance costs associated with erosion. The modification is complete in experimentation phase and is now in certification phase.

For any party that needs convincing that lift and drag performance can be improved through simple mechanisms, feel free to PM me for a reading list of numerical and experimental studies on the matter.

The question of demand for a solution to the R22/44 and other helicopter erosion issues is rather open, and given the industry's experience with tape performance that is not surprising. Any parties that may be interested in protection of their fleet MR & TR's as discussed are welcome to PM.

Specifically for the R22, one configuration trialled resulted in low Nr blade stall at 68%Nr v 83% nominal, and 80% control. The configuration for certification is not quite that radical, it does reduce blade stall Nr though slightly, to around 76%Nr. Torque requirement is also reduced by approximately 9% for a given condition, and autorotation ROD is reduced by a similar margin. Operationally, the only notable change is that in the autorotation flare the Nr recovery/g is greater, and collective needs to be used to maintain Nr within upper limits. This makes the flare/landing somewhat more comfortable than baseline. The time constant for engine failure is still short, but does appear to be slightly kinder than the baseline. It is still not a fun activity, and all of Frank's safety notices about response to low Nr are applicable as they are in any rotary aircraft.

Costing is proposed to be low-moderate for the STC, and the tape is expected to be field replaceable for the outer section at least. Payback period for the STC will be in the order of no more than 1.5 maintenance visits for blade protection costs alone.

cheers FDR

Reference:

F.Y.M Wan Flapping Response of Lifting Rotor Blades to Spanwise nonuniform Random Excitation Journal of Engineering Mathematics 1980 vol. 14 (4) pp. 1-21

T Lee, D Matteescu experimental and numerical investigation of 2D backward facing step flow, Canada Journal of Fluids and Structures 1998 vol. 12 pp. 703-716

Technical Bulletin, Rotor Blade Erosion Protection Dept of the Army 31 Dec 1991 TB-1-1615-351-23

L Pfledderer, M Pepi, "Sand Erosion Test Method for DOD Unique Environments", Army Research Laboratory Aberdeen, MD. ARL-RP-229 September 2008 (reprint from the Proceedings of the 2007 Tri-Service Corrosion Conference, paper 1783, Denver, CO, 3–6 December 2007).