Go Back  PPRuNe Forums > Aircrew Forums > Rotorheads
Reload this Page >

Certification of Robinson Helicopters (incl post by Frank Robinson)

Rotorheads A haven for helicopter professionals to discuss the things that affect them

Certification of Robinson Helicopters (incl post by Frank Robinson)

Old 25th Sep 2000, 15:36
  #21 (permalink)  
Outside Loop
Guest
 
Posts: n/a
Post

I personally have around about 6-7000hrs on R22's(not sure on precise figure cause I couldn't be bothered adding them up)most of which mustering cattle in Oz.
They are a very popular mustering tool as they are light,manoeuvrable,reliable and cheap on gas.
There are literally 100's of them mustering around Oz on a daily basis,clocking up many 1000's of hours/year.(can't quote actual figures)
I have experimented with the low/zero g situation as have probably very many pilots who have done the Robinson safety course.I found that recovery from the roll is almost instantanious with a little bit of aft cyclic ie. once the rotor system is placed back under load.Whilst I certainly do not recommend placing the A/c in a zero or negative g attitude, it is recoverable provided you are aware of it.
Incidently deliberatly placing any helo in this situation is fool hardy unless you think you can fly with half a tail boom!There are always ecceptions of course.
With regard to flying out of balance I can honestly say that during mustering op's, the A/c is very rarely flown in balance.Flying a little bit sideways increases the visability and allows quick stops at low altitude,whilst minimising the risk of a tail rotor strike.
I have never come into dificulties,I have never spoken to any one whom has had dificulties,nor have I ever heard of an R22 coming to grief whilst flying out of balance.
Helimustering in Oz was primarily conducted in Bell 47s and Hughes 300s before the advent of the R22s.Whilst I have 0 experience in the latter,I have around about 4000hrs mustering in the 47.
There is absolutely no doubt that the R22 is the easier and more forgiving to fly.This is because the low inertia rotor system allows quick recovery from an over pitch or low rpm situation.It spools up rapidly and is very quick through translation.
This of course leads to it's only down fall that I can think off...When the **** hits the fan!! Obviously emergence situations require a little more finese as there is little margin for error.
As for the incorrect rigging bit I can't comment. I only break them not fix em !
It is true that there are a lot of accidents involving R22s .This is largely due to the type of operation they mostly engage in ie.mustering and training. They are also cheap to fly and hence are very popular amongst the low Hr inexperienced fraternity.
I am confident that if you were to approach CASA Aust and ask for statistics on R22 accidents in Oz, you would find the vast majoraty to be pilot error.
 
Old 25th Sep 2000, 19:11
  #22 (permalink)  
Lu Zuckerman
Guest
 
Posts: n/a
Thumbs down

To: WhoNeedsRunways

You have just proved my main point regarding the design of the rotor head and you have proved an unstated point about how Robinson relates to their operators.

In my report I state that the pitch links on the Robinson helicopters lead the blades by approximately 72 degrees and that when you want to fly forward you have to offset the cyclic by approximately 18 degrees to the right. The opposite would be true if you wanted to fly backwards only this time you would offset the cyclic approximately 18 degrees to the left. In your statement you indicated that Tim Tucker in his testing for recovery from Zero G would pull the cyclic straight back with a TAD of left cyclic. How much is a tad relative to the degrees in the compass? Could it be approximately 18 degrees? In his testing, he undoubtedly found that to pull straight back on the cyclic would introduce a right roll component, which the POH tells you to avoid at any cost.

Here is the unstated point. If Tim Tucker did discover this fact then, why-oh-
why didn’t he provide this instruction to the operators of Robinson Helicopters? The instructions in the un numbered last page of section 4 of the POH were in fact created to cover the collective asses of the FAA and Robinson. If it is proved that a pilot violated these instructions then it could be easily proved in court that it was pilot error. If the pilot follows the instructions for recovery from Zero G he can exacerbate the right roll created by the high mounted tail rotor and in the process kill himself. Robinson in my opinion will not include in the instructions to apply a tad left cyclic because they would have to explain why which would lead to them telling you and the others that they have a design problem in their rotorhead.

If you or anyone reading this post are attending the Tim Tucker training program please ask him about the points I have raised in this forum. Remember one thing, this man is a pilot and not a God and he represents the thinking of Robinson Helicopters. You as Pilots and mechanics have every right in this world to challenge him. If one of you is planning on attending and you don’t have a copy of the report please send me an email and I will send it to you. Also include your fax number and I will send a diagram that fully explains the problems with the Robinson rotorhead. If you request both and there is more than one request I will send the report to all but the faxed diagram will go to the first person requesting it.

Regarding the differences between theory and practice, the THEORY regarding gyroscopic precession and its’ relationship with rotor head design is not theory but has been reduced to engineering practice ever since the VS 300 took flight. In two blade rotor systems like Bell the pitch link leads the blade by 90 degrees. On some other helicopters the swash plate command leads the desired reaction by 45 degrees and the pitch link leads by 45 degrees which totals 90 degrees which is the phase angle of the blades. On the Robinson the blade phase angle is 90 degrees but the pitch link leads the blades by approximately 72 degrees and, the swash plate movement leads by 90 degrees which requires the pilot to adjust his cyclic by just a tad to compensate for the 18 degree difference.


To: Outside Loop:

First of all I have already had a request for the report by a member of ATSB. The ATSB like the NTSB in the States can do little even if they know a design to be defective. They can only wait for an accident to occur. The NTSB has had the report since 1996 and they could do little. However, last month there was an accident involving a highly experienced pilot with a lot of hours in a lot of helicopters including. flying in a Robinson Aerobatics team and conducting flight instruction in an R22. This man lost his main rotor while conducting flight instruction with a zero hour pilot. It is not known who was flying. In any case, the NTSB was instructed by the Chairman of the NTSB to reopen the investigation as a result of the accident, which occurred in California.

Regarding how the Robinson helicopters are employed in Australia I have seen examples on Canadian and US television. In every case, I hold my breath waiting for the helicopter to come falling out of the sky. It appears that you and your comrades are violating every instruction in the POH that restricts you from flying under the stated conditions. When something happens as a result of your collective actions Robinson can easily claim that it was pilot error even though the accident would have been caused by the design of the rotorhead.

According to NTSB records there were two R22 rotor loss accidents in New Zealand and two R22 rotor loss accidents in Australia. The report did not address the R44. I would assume that the causes for the accidents were listed as pilot error. For sure, Robinson would not state that the design of the rotorhead and the confusing rigging procedure were a contributing factor.


------------------
The Cat
 
Old 26th Sep 2000, 03:29
  #23 (permalink)  
JoePilot
Guest
 
Posts: n/a
Red face

Lu: I agree with WNR - you just can't be a helicopter pilot..

OutsideLoop: Yup .. spot on, agree with most everything you say there! Same here 'uncountable' experience (25yrs+) .. some VERY extreme flight regimes (60kts+ side and back .. no bump yet but don't want to try any harder than I have (have taken paint but not undercoat off tail boom with blade) .. sustained 90kt+ cliff turbulence survived) still massive respect tho (you only die once).
But don't you agree that the Robbie machines rarely break by themselves - much more reliable than any other helicopter I can think of. (how often does an S76 fly without something not working? How much pain does a Bell 206 owner have to go through before he saves himself $400,000 dollars and flys more reliably and faster in an R44 (and the guys in the back get to join in too))

ArkRoyal: Should know better... really!

Lu: Pilots are amazingly sophiticated feedback processing units which many engineers have a hard time to understand. You just can't fly one of these machines by moving the controls in the theoretically required direction - it just does not work like that.

(you'd probably feel tempted to design a 'system' which sat in between pilot and machine to make fore and aft stick movement command an exactly fore and aft response to eliminate the (many) effects which make this 'not necessarily the case' in all sorts of machines)

Even if you were right about 72deg being wrong which you are NOT (see explanation below) 18deg mismatch is child's play - part of the process of learning is to calibrate and 'map' control input with response.

WHY 90 DEGREES PHASE ADVANCE IS WRONG:

In a gyroscope situation if you take the 'vector cross product' of an angular momentum vector and a couple perpendicular to the angular momentum vector you'll get a result which is perpendicular to both vectors. ie 90 DEGREES to where you thought you were pushing it. People think this is very strange and so they have great respect for this mystical gyroscopic effect - inventing all sorts of jargon (Gyroscopic Precession (90deg) or talk of 90deg 'phase lag' etc.)

The reality is that it is not at all strange nothing is 'lagging' anything and anyone can UNDERSTAND this, I think. Picture if you can (ie if my prose is capable of conveying it clearly enough) a bicycle wheel on a short axle arranged horizontally in front of you, spinning very fast (anti-clockwise(when viewed from above(never did understand what clockwise meant without specifying viewer position))) - no gravity so just 'hanging' in space. You take one finger and push the top axle stub away and another finger and pull the bottom axle stub towards you simultaneously - same magnitude of force. The rotating wheel does not change its plane of rotation in the direction which one might on casual inspection think intuitive (ie top axle stub away from you) but it moves with top axle stub going left. THIS IS THE POINT at which you must not run and hide behind a 'jargon term'. It makes sense like this: picture a point mass on the end of a spoke (part of the wheel) - think about how your axle pushing is affecting it as it rotates - when it is on the extreme left your action is neither pushing it up nor down - only when it is in the half closest to you are you pushing it up - when it gets to the extreme right then you are again not pushing it up any more - during the half cycle when it furthest from you, you are pushing it down. So during the WHOLE of the half cycle which is closest to you you are pushing it such that it will be higher than it was - since this is true for the whole of this half then it will be at its highest point at the extreme right (ie where you have finally stopped pushing it higher) So it LOOKS like it has moved 90 degrees after you thought it should have done if you had not actually thought about what you were doing! Well ... instead of saying all that, people just feel more comfortable saying "yea .. that's gyroscopic precession"

Well I hope that was clear because you kinda need it for this bit:

A helicopter is a bit like that... hence the '90 degree error' which Bell and Lu made.

FOR A HELICOPTER (EGGS GRANNYS SUCK TEACH ....SORRY etc):
The blades (spokes) go round and round and flap up and down however they want to - which results in the plane of rotation being almost exactly whatever it wants to be (regardless of rotor-masts and tail booms).

So we have to look at where blades WANT to flap to in order to work out what the plane of rotation is going to be. If you increase the Pitch on the half closest to you (same layout as the bicycle wheel) blades when in that half(ISH)will want to flap up to the equilibrium position for that degree of pitch - how fast they try and get their will depend on their difference between actual flapped position and equilibrium flapped position. (still with me anybody?)HERE'S THE KEY BIT. The problem is that near (BUT BEFORE) the end of this near half the blade will have reached an actual flapped position which is equal to the equilibrium flapped position ... so it won't really want to go up any more. ie. It will have got as high as it is going to go some number of degrees BEFORE it gets to the extreme right hand side. If you actually do want to have the blade be at its highest point at the extreme right hand side you are going to have to delay (by a number of DEGREES (... SAY 18! for a robbie)) where in the cycle the blade experiences extra pitch. THAT'S WHY 90 DEGREES IS WRONG!

Lu: The subtlety of a further aspect of this - which you entirely miss the point on is progress which Frank has made in the Robbie.

Lu writes:
Regarding the differences between theory and practice, the THEORY regarding gyroscopic precession and its’ relationship with rotor head design is not theory but has been reduced to engineering practice ever since the VS 300 took flight. In two blade rotor systems like Bell the pitch link leads the blade by 90 degrees [JOE: does not really matter that they have made this error]. On some other helicopters the swash plate command leads the desired reaction by 45 degrees and the pitch link leads by 45 degrees [JOE: now this is a positively BAD thing to do] which totals 90 degrees which is the phase angle of the blades. On the Robinson the blade phase angle is 90 degrees but the pitch link leads the blades by approximately 72 degrees and, the swash plate movement leads by 90 degrees which requires the pilot to adjust his cyclic by just a tad to compensate for the 18 degree difference.

JOE: This is a tragedy of missing the point.
The swashplate changes attitude with the (pendulous) helicopter, so, sure, you have to have the swash plate rigged 90deg phase 'advance' so that changes in aircraft attitude have the same directional effect as stick inputs (which would not happen with the 45 + 45 deg option) Since 90deg is not the phase advance you want for pitch inputs to the blades you MUST arrange for the correct advance angle to be above the swash plate - to do that you must arrange your pitch horn at the required angle back from 90 degrees. (having the disc respond to a/c attitude changes is important for stability/responsiveness - which you can influence by changing the length of arms to change the amount that the blade's pitch is changed for an amount of a/c attitude change)

So if you think Frank has not responded to you because you are 'getting close' think again ... He gets thousands of well intentioned sincere inputs like yours. He is not heartless at all - it is an awful burden and great personal sadness when someone dies in one of his helicopters - he would and does do anything he can to stop it happening - including building the most reliable helicopter and instilling in everyone he can a fear of screwing around with his 'envelope' - hence the flight manual warnings at the very least. If you go looking for the edge - don't be surprised if you find it!

(and as for the money thing - you really think that's what it's about for him? - He leads the most amazingly modest life you can believe ... under the circumstances)

Sorry to bore everyone
JOE
 
Old 26th Sep 2000, 04:27
  #24 (permalink)  
Lu Zuckerman
Guest
 
Posts: n/a
Thumbs down

Dear Joe Pilot,

I am very sorry to admit that I couldn't follow your explanation about the bicycle wheel although I know what you are talking about as I have demonstrated the same thing.

It is difficult to convey my opinions on why the Robinson helicopters should not have been certified when I am talking to an ardent supporter of the Robinson design. I can talk all day about phase angles and gyroscopic precession but if you disagree with me then It forces me to defend my position which can be difficult when I have to counter different opinions. Suffice it to say, the Robinson design should never have been certified because it does not comply with the FARs and Advisory Circular 27-1 (Certification of Normal Catagory Rotorcraft). It's all in my report and all you have to do to get it is send me your email address and if you have a fax I'll send you a diagram that explains the difference between a Bell Rotor system (which is right) and the Robinson Rotor system (which is wrong). One other point is that you mentioned a device that indicates the exact movement of the cyclic stick. Funny you should mention that. AC 27-1 paragraph 27.175.b.(1)(i) requires that a stick plotting board be used to demonstrate that the helicopter flies in the same sense as the cyclic displacement. They allow a small deviation between cyclic movement and aircraft flight direction but this is due to slight pitch coupling but not 18 degrees difference. It is this 18 degree difference that if not compensated for can introduce extremely high flapping which over time can fatigue the rotor shaft or possibly cause rotor incursions if the flapping loads are sever enough

------------------
The Cat
 
Old 26th Sep 2000, 04:44
  #25 (permalink)  
Lu Zuckerman
Guest
 
Posts: n/a
Thumbs down

Dear Joe,

Your illustration of input on the wheel shaft and the resultant movement of the wheel is the same as moving a cyclic stick in a leftward direction. The input is 90 degrees ahead of the result. If you wanted to move a Bell to the left the swash plate would tip to the left. At that time the blade over the nose is at the lowest pitch angle and the blade over the tail is at the highest pitch angle. The end result is that the disc tilts to the left and you end up flying left. I don't want to go into the pitch input and the resultant movement on the Robinson as it becomes too complicated. It's in the diagram. You may end up with Carpel Tunnel Syndrome trying to counter my inputs. Just ask for the report and diagram and then we can go from there as we will be playing on a level field.

------------------
The Cat
 
Old 26th Sep 2000, 06:19
  #26 (permalink)  
JoePilot
Guest
 
Posts: n/a
Post

Oh alright send the report then .... I hope it's good tho' [email protected]

And sorry you just think I am the one 'stuck in my view'

BUT

You keep ignoring:
1.Robbies remarkable MECHANICAL reliability.
2.Are you a 'helo' pilot.
3.The FATIGUE failures you now mention don't happen.
4.I (we) are pretty experienced with these machines in extreme conditions - and I assure you that you really must have to try damn hard to cause this class of accident (which you must stop insisting are mechanical failures)
5.Please acknowledge that a significant number (3 out of the 4 which I do personally know about) were people choosing this path through private investigation of the phenomena at low-g (the other was from stalling the rotor through low RRPM - clear pilot error on a fully mechanically sound helicopter).
6.Robbie performance/efficiency - remarkable.
7.Why make helicopters with un-aerodynamic pointed noses (marketing)
8.But aren't you ignoring me? You can easily 'demonstrate compliance' - it's easy because it does it and way more. Put any limmitations in the book if it will increase respect for the machine.?

Please answer these points....
JOE

(Re Carpel Tunnel Syndrome CTS
Is surgery always necessary?
No. the hand surgeon will first examine your hands and review your symptoms. If you have something other than carpal tunnel syndrome, the doctor will suggest the appropriate treatment. If CTS is suspected, he will first prescribe non-operative treatment with splinting and anti-inflammatory drugs. A test conducted on the nerve will positively determine whether or not it is pinched and if you have carpal tunnel syndrome. ) - I think I must need surgery!
 
Old 26th Sep 2000, 06:27
  #27 (permalink)  
JoePilot
Guest
 
Posts: n/a
Post

....and the point about the bicycle wheel (and the point mass on a spoke behaviour) is that's how you can understand what the 90degree deal is all about - and by the same token it is the key to realising that that is not the same thing as is happening with a rotor.

(It's a good thing they got the B206 certified before you had to have the stick go the same way as the disc then ... eh?)

JOE
 
Old 26th Sep 2000, 07:52
  #28 (permalink)  
Outside Loop
Guest
 
Posts: n/a
Post

Lu
Please don't hold your breath to long because these type of accidents just aren't happening.Robinsons may well have a design imperfection as you have pointed out but this does not make them unsafe to fly.
On the other hand if I were observing a Robinson doing aerobatics and holding my breath till it crashed, I would feel quite safe.
It would be interesting to know what the A/c was doing and what attitude it was in when it failed/crashed.If you are able to find this out please let us know.
I can well understand Frank Robinsons actions in covering his arse.In this day and age people are sueing for millions just because they find a tiny cockroach in their burger.When an A/c crashes and somebody is killed a scapegoat must be found. Somebody must alway's take the blame. If all the i's aren't dotted the t's crossed and boxes not ticked conservatively,then Franky baby would probably have a permanent appointment with his defence lawyer.The law is an ass and clever lawyers are skilled at finding loop holes.
I only know of 1 accident involving rotor loss in an R22 in Aust. I can not dispute that another may have occured.
In this particular case in northern WA it was a failure of a main rotor blade.It is well known, and investigators proved by researching job invoices that the owner/operater was not logging correct flight time.In fact some who knew him suggested as much as 50%.This put the total time in service somewhere around the 4000hr mark.(TBO 2200)
If you can enlighten us on the other incidences please do. I would love to know.
 
Old 26th Sep 2000, 08:15
  #29 (permalink)  
Lu Zuckerman
Guest
 
Posts: n/a
Thumbs down

Dear Joe,

here is my response to your 8 questions or should I say statements.

1) Robinson reliability. I have to admit that the flight control system is a picture of simplicity. The only problems I am aware of were some failures in the cyclic control system which may have resulted in the loss of several aircraft. It was traced to insufficient design strength. The parts were modified and no problems since. Although the system is simple the rigging procedure is not. Because of the rigging procedure the mechanic can inadvertently rig in too much pitch which could result in rotor stall (not to be confused with retreating blade stall). The rigging procedure can also set up binding of the swash plate and mechanical contact between control rods and fixed structure. The rigging procedure for the main and tail rotors are completely different from any other helicopter. Talk to the mechanics that service your aircraft.

2) No I am not. When I was in service many years ago I was a helicopter mechanic. The philosophy of the US Coast Guard at that time was if you fix it you must fly in it. The pilots on occasion would allow me to fly the helicopter. (HO4-S/ S-55, HO5-S/S-52, HO3-S/ S-51 and a Bell HTL-1. I could maintain course and altitude pretty well but I couldn't hover to save my ass.

3) Regarding fatigue failures what do you think causes the rotor mast to fracture. Whether the fatigue builds up over a long time or in an instant the fracture is still caused by fatigue. Fatigue played a part in the failure of the cyclic controls as mentioned above.

4) loss of rotor or rotor incursions on the airframe can be explained away by saying they were caused by pilot error. It could be that the pilots operated the helicopter outside of the restricted limits. The restricted limits relative to siseslip and out of trim were incorpoated in order to eliminate the extremely high flapping loads which resulted from the design of the rotor head.

5)I'm sorry for the loss of the pilots that experimented with low G recovery however, you haven't said what type of helicopter they were flying at the time. Regarding low rotor RPM I believe in a previous post it was stated that the rotor had a high rate of spool up due to the power available and the low inertia of the rotor system. Could it be that the rotor was placed in a stall condition due to too much pitch which increased the drag on the blades which prevented rapid spool up?

6)Regarding the Performance and efficiency that may have been true when the aircraft was first built but if you fly it according to the POH then the helicopter is like taking a Ferrari and replacing the engine with a Chevy (Holden) straight six. Sure you can still drive the Ferrari but how does its' performance compare to the original with the Ferrari engine installed.

7) Have you ever seen what the original 206 looked like when it was proposed to the US Army as a light observation helicopter. That helicopter lost in the competition to a Hughes 369 (H-500). Bell knew it had potential so they turned the design over to one of the top US industrial design firms and the rest is history.

8)Regarding compliance, the FARs and the AC 27-1 both require that the helicopter demonstrate Side slip at 90 degrees induced by hard input on the pedals both right and left. These documents also require demonstration of out of trim by 10 degrees left and right. Since the POH restricts the pilot from doing those things just Imagine if Frank Robinson went to the FAA and told them that he had just designed the R22 but they could not be side slipped or flown out of trim. The FAA would tell him to piss off.

Another point is that the FAA has a requirement that states any new and/or unusual design must be proved by dynamic testing as well as through an analytical process. The R22 rotor head met this criteria but the testing was never accomplished in accordance with the FAA procedure. Yet , the rotorhead was accepted. Could it be that Frank Robinson who was the FAA Designated Engineering Representative (DER) signed off the design. The fact that he was the DER violated the FAA regs which required that the DER not have a vested interest in the design or a financial relationship with the company producing the design.

Regarding fatigue and I'll add in wear please do the following: The next time you are in the repair shop and the mechanics have the rotorhead off the mast, have the mechanics check the mast for signs of wear or elongation of the holes that the teeter bolt fits into. Also, have them make the same check on the rotor head where the teeter bolt passes through. I saw two rotor heads that exhibited this wear and I attributed it to the tendency of the blades to lead and lag when they flap in relation to the rotor head. In order for this kind of wear to occur, the mast has to react the applied loads. This means that each blade leads and lags at the frequency of rotor RPM.

If the wear is evident on the holes in the mast and/or the rotor head the mast is under a cyclical fatigue that causes the mast to twist plus and minus at twice the speed of rotor RPM. Have them perform the check because if you and your buds fly the R22 the way you indicated there is a good chance that you are being set up for a fatigue failure. Another thing that the mechanics can do if you are allowed by your operating regs is to coat the mast with a product called stress coat. That will provide a visual check of the twisting of the mast.

------------------
The Cat
 
Old 26th Sep 2000, 18:48
  #30 (permalink)  
212man
Guest
 
Posts: n/a
Talking

I tend to agree with Joepilot, some of he arguments are spurious i believe. For instance, the sideslip issue. Just because the a/c has demonstrated a certain flight conditions, does not mean that that it should be approved for normal operations. If that were the case why would we have sideways flight limits?.

Reference is made to the combination of teetering head and flapping hinges; that's not new, the 214ST has them too.

Te report asks why the tail rotor pre-coning; surely for the same reason that the Bell use it on their main rotors? to reduce hub stress under load. It might help avoid boom strikes at extreme flapping limits too. Maybe the 407 could have done with it!

What evidence is there to suggest fatigue failures are a problem? The 212 recently had an a/d which grounded several of our fleet because the masts needed inspecting for wear from a split ring used in the damper assembly. Several 212s have lost masts recently. I don't hear any protests about that, yet you'd think after 40 years that would be impossible.

I may be cynical, but I believe this is a biased argument, albeit well stated. It is a fact that Robinsons crash when mishandled, but so do most types. Colleagues who were there tell me that more than a few 205s were lost in Vietnam due to mast bumping in extreme manouvres.

The R22 is highly 'chuckable' and great fun. It also instills great respect for it's low inertia head, which can only be of help on larger types. If it is as bad as is claimed the accident rate would be a lot higher.

------------------
Another day in paradise
 
Old 26th Sep 2000, 21:39
  #31 (permalink)  
Lu Zuckerman
Guest
 
Posts: n/a
Thumbs down

This in response to Outside Loop:

The Robinson helicopters do have a design defect and this makes them unsafe to fly. It is the restrictions placed on them by the FAA directive that in fact makes them safe to fly "now" as long as the aircraft is operated within those restrictions. I will concede that Bell rotor systems are subject to loss of control in a low G situation. in addressing the recovery from a loss of control in low G on a Robinson if the pilot follows the POH instructions the design defect in the rotor head can result in loss of the aircraft. Reading several postings above another writer stated that the Robinson test pilot explained to him that when you pull aft cyclic to correct for loss of control you add in a “Tad” of left cyclic. It appears to me that he is aware of the design defect, and by pulling a tad of left cyclic, he is compensating for the design defect. I ask again, if he is aware of the problem then why isn’t the instruction to use a “Tad” of left cyclic in the emergency operating procedures?

Regarding Frank and his lawyers, I had previously mentioned that I have a lawyer friend in California that tried three cases against Robinson and he was awarded millions of dollars for his clients, but was unable to collect a cent. Because, Frank Robinson keeps his money in offshore accounts and he leases everything in his plant including the building. On paper, Frank Robinson appears to be as poor as a church mouse.

Regarding the crashes in Australia this is all I have.

1) Julia Creek, Australia Ferry flight VH-HBK Mast Separation 06-15-92

2) Brighton Downs Station, Australia Business Flight Tail boom and cockpit strike 07-17-95

The FAA advisory was added to the POH on or about 13-January-1995.

The loss of the rotor blade you mentioned was not in the NTSB report.

This is for 212 Man:

The reason that sideslip and out of trim flight are restricted on the Robinson Helicopters is because of the rotorhead problem. If you perform those elements of the restricted flight envelope the flapping loads will be so sever that it could cause rotor failure or, mast separation. The questions in my report that were addressed to the FAA and Robinson were couched in such a way that they would have to give a full explanation of how the helicopters were certified and what tests were run to verify that the helicopter was in fact certifiable. It is my contention that Frank Robinson as the DER for the FAA signed off on the testing knowing that the rotor system was in fact defective by FAA definition. Also I asked questions of the FAA and Robinson relative to the rigging procedure to find out how the FAA approved the design of the flight control system when it was in violation of FAA design guide lines.

At my last count (as of 1976) there were over fifty Bell Helicopters that lost their rotor due to Low G flight and subsequent mast bumping.

Regarding the flapping capability of the 214 ST rotor head that is not true. The 214 ST has the same type of rotor head used on the 214 and similar to that used on AH1-J. The 412 uses similar technology but it has four blades. The rotor has the capability to flex due to coning action and in response to flight loads but the blades do not flap as they do on the Robinson rotor system.

Getting back to your first statement about having limits on sideward flight. The certification requirements require the demonstration of sideward flight but they do not specify an upper limit. The demonstration is in fact a means of determining and specifying the limiting speeds of sideward flight. The same is true for rearward flight. These limits are then published in the POH for each helicopter. The Robinson is restricted from sideward flight and out of trim flight yet the FAA design regs stipulate that both flight parameters be demonstrated in order to gain certification. If the Robinson can’t do it now, how did they demonstrate this capability during certification?


------------------
The Cat
 
Old 27th Sep 2000, 00:08
  #32 (permalink)  
JoePilot
Guest
 
Posts: n/a
Post

I'm pissed off! I just wrote a huge answer to each point ... loaded another web page in the mean time and closed my browser - been fishing around in caches and history can't find it.
AND then I finally read that report and realised that it would appear Lu does not really understand these topics (though he has spotted some ammature mistakes in other people's reports ... which always makes us feel important)

So briefly:

Re Point 3: No!
"A Simple Definition of Fatigue
Fatigue can be defined, in engineering terms, as a mode of failure that involves the nucleation and growth of a crack in a structural component undergoing loads that vary with time and whose maximum amplitudes induce stresses that are equal or lower than the expected yield strength of the material used. From a more "scientific" point of view, fatigue is the characteristic behavior of a material undergoing variable loads, from both the deformation and fracture points of view, and includes the study of topics such as: cyclic plasticity, localization of deformation, dislocation structures, crack nucleation, crack propagation, and any other phenomena produced by variable loads.
The key point is that loads must change with time in order to have "fatigue" as described above. This makes fatigue a widespread phenomenon in today's technological society, where countless artifacts and devices, from the space shuttle to many children's toys, are subjected to loads whose amplitudes and forms change with time."

KEY PHRASE: "....lower than the expected yield strength of the material used."

So this key final mast event is just not fatigue! - OK !? (Lu:"...what do you think causes the rotor mast to fracture.[?]" - NOT FATIGUE !!
(control system - ONCE ever... maybe, but no evidence ... you know the ONE ... still sad though)


Point 4.
We do! It doesn't. Not theory ... actual practice. - acknowledge ! (?)


Point 1. Ask the engineers:
I have now talked to them (I think they maintain more than anyone else) - they say it is possible over time to keep winding on excess pitch on adjustment - it'll fly 'normally' but will have reduced auto revs. I test fly them for that - never remotely had a problem. Now AUGUSTA rotor heads CAN be catastrophically incorrectly assembled ! And so can many things if you don't know how to do it. Apparently after you've done the first one on a Robbie its easy and simple thereafter. There IS NO EVIDENCE that this is a problem, and there would be in the wrecks - there is not! this is a RED HERRING!

Point 2. Not a Pilot:
Well I won't be cruel here - at least you've touched a stick. But A LITTLE KNOWLEDGE IS A DANGEROUS THING - (or know your limmitations) humility in the face of ignorance would win more respect for your views. Learn to fly one - it'll teach you alot (R22 will teach you to be pretty sharp - very responsive (this is a good thing if you can and a bad thing if you can't!)).


Point 5. What 'spools up' must 'spool down':
Well if you were a pilot you would know that RRPM is the most important thing in the world. The lower it is the more angle of attack is required. When the angle of attack is TOO big the blades stall and it is unrecoverable in any helicopter even with full power (except in unusual circumstances). To slow the rotor you have to be demanding more (energy) from the rotor than you are putting in to it (energy input could be engine, height or speed). If the energy you consume is RRPM then it had better be a fairly short term policy, or you had better be very near the ground, or you will probably die ... SIMPLE CONCEPT (not much different than remembering which way to turn the steering wheel of a car when the road bends to the left). I like the fact that it reminds you quickly before much energy is lost and then it hardly needs any energy to get it back again. (SOME PEOPLE like to sit in their flying armchair and contemplate what they are going to do about the steadily falling RRPM - fine but by the time they decide to DO SOMETHING they are going to have to 'rob a bank' to find the energy they need to replace the missing RRPM - and then there had better not be anything pressing because they're going to have to wait.....I prefer LOW INERTIA!)

Point 6. Well I'm not a flash bloke needing a Ferrari. The (r44) performance IS great - faster than B206 for HALF the fuel burn. Big margin between power allowed and what the engine can do (and it doesn't go 'POP' if you have to go there - ROBUST). Low revving - compared with other apps of same engine. (enough? - no? try hover at MAUW in B206 next to R44 .. look at margin).

Point 7. H369 changed from sensible shape to marketing nose job - never could understand that - Sadly I am a member of the 30% of people who thing functional elegance is beautiful. Boy the R44 is SLIPPERY ! (Any helicopter more so? Why are they all such illogical shapes?).

Point 8.
We all KNOW it can do this. - engendering fear of the edge in people is just fine... but don't USE that to beat them with

This new stuff about fatigue and wear in the mast and head - OH COME ON! Sure bearings wear - they get replaced! Mast are NOT failing through fatigue! - even though you wish they were - they DO NOT .. ARE NOT (I AM FATIGUED THOUGH!)

Incidentally - if you were fundamentally wrong ... could you admit it? .. I think I could but I think it would be harder for you... Anyhow I don't think I'll have to - and I doubt if you can... (now after so many years invested in this half baked 'anti theory'.)

I think you seem to half understand the subject - but not enough - to much 'black art' in your stuff - not enough understanding. I think you are clearly sincere in your belief. I wouldn't try and start designing helicopters though !!

Keep up the good work ... always good to stir a little thought in people..

Relax
C Ya
JOE
Robbies:
1.There are no misrigging accidents! (you can tell this by examining the wrecks)
2.You can fly it normally (perhaps a little sportily) - no problem.
3.You can massivly exceed cert. criterea (to prove certifiability of course) with no detrimental effect.
4.Fatigue problems are not a significant issue (you can tell this by examining the wrecks)
Chill..



[This message has been edited by JoePilot (edited 26 September 2000).]
 
Old 27th Sep 2000, 00:14
  #33 (permalink)  
JoePilot
Guest
 
Posts: n/a
Post

Burn the whiches! - Let science prevail!
 
Old 27th Sep 2000, 00:35
  #34 (permalink)  
hannes
Guest
 
Posts: n/a
Exclamation

good job JoePilot!!!
 
Old 27th Sep 2000, 04:20
  #35 (permalink)  
Lu Zuckerman
Guest
 
Posts: n/a
Thumbs down

To Joe Pilot:

It has occurred to me that you obviously love Robinson Helicopters and you will defend them to your death. That is an admirable characteristic but it seems that you are carrying it to extremes.

I know what you are thinking, “Look who’s talking”. The only point of my writing the report was to bring to the attention of the NTSB that they had not considered all of the factors in their final report. That report in case you are interested is titled SPECIAL INVESTIGATION REPORT:
ROBINSON HELICOPTER COMPANY R22 LOSS OF MAIN ROTOR CONTROL ACCIDENTS. The number of the report is PB96-917003 NTSB/SIR-96/03. In the report they overlooked the problems involved in the certification and the testing in order to gain certification. They did not look into the rotor head design and they did not look into the rigging procedure. It seems to me that the NTSB has seen the light although you haven’t as they are going to reopen their investigation on the basis of the report.

Your comment 3) It is also obvious that you have access to a very good engineering library as it seems you copied a textbook for the definition of fatigue. My point was that the mast and rotor system could develop fractures and or excessive wear due to the high flapping loads and /or the tendency for the blades to lead and lag. These loads are reacted by the through bolt (Teeter Bolt) and the rotor and the mast. The mast is subject to a cyclical twisting at twice the frequency of main rotor rotation and the holes that the teeter bolt passes through are subject to elongation due to the high frequency twisting loads. The mast fractures when the applied load exceeds the yield strength of the mast or, if the long-standing cyclic twisting loads and the high flapping loads cause a weakening of the metallic matrix of the mast.

Your comment 4) I would strongly suggest you keep your insurance up to date. As they say, Fate is the hunter. Another point made by you or one of the other contributors about lawyers being asses. They may seem that way to you but not to the families if you or any one else eats it in a crash. Lawyers like pilots and engineers have their place in society.

Your comment 1) Ask your engineers if they can make a comparison between the Robinson rigging procedure and say a bell or a Sikorsky. If they can’t give you a satisfactory answer, ask them if they have ever worked on a Bell or Sikorsky. There is a saying in computers called WYSISWYG or, What You See Is What You Get. This is not so on the rigging procedure for the Robinson. Rigging for low pitch and for cyclic pitch requires that the blades be oriented as if you were rigging a Bell helicopter. Over the nose and tail or, over the lateral axis. When the pitch setting is made the blade may be over the longitudinal or lateral axis but the pitch link is not.

When the pitch is set in the blades by adjusting the pitch links or the PP tubes the blade will increase in pitch or decrease in pitch when the pitch link is over the longitudinal or lateral axis. This is because of the 18 degree offset. That is what I meant by saying that you could rig too much pitch. Another point regarding rigging that you have overlooked and that is, if the cyclic is placed in the neutral position fore and aft how do you explain that the pitch angles are different when you move the stick to the forward stop and when you move the cyclic against the rear stop.

They should be the same, but the Robbo rigging procedure states that they must be different and if they are the same the mechanic must adjust PP tubes to get the desired reading. Please tell me why the Robbo is different from any other helicopter

Your comment 5) Regarding spool up I was only referring to a previous statement made by another individual.

Your comment 6) The Ferrari analogy had nothing to do with power. My point was that if you put the Holden engine in a Ferrari you would seriously effect its’ overall performance. By placing the restrictions on the Robbo you seriously effected its’ performance. It seems however that you don’t let the restrictions get in your way as you are flying the R22 outside of the FAA mandated restrictions regarding sideslip and out of trim. Like you said on several occasions, it is up to the pilot as to how he wants to fly or, if he wants to fly his machine into a mountain.

It seems that no matter how hard I try, I will never win this argument. So, just keep loving the Robbos’ and for your families’ sake, keep up your insurance.


------------------
The Cat
 
Old 28th Sep 2000, 02:55
  #36 (permalink)  
Skycop
Guest
 
Posts: n/a
Exclamation

Joe Pilot,

You are obviously an expert on the Robinson.

Just for the record, what else have you flown?
 
Old 28th Sep 2000, 11:43
  #37 (permalink)  
HeliFlight
Guest
 
Posts: n/a
Post

As an unbiased observer with no prejudice towards either side, I think it is obvious which side of the argument has presented the best case. I have flown the R-22 and personally do not have any interest in flying one ever again. Having read all the postings thoroughly with great interest curious to see if this silly little helicopter should have its certification removed, I think the clear answer is -- NO.

Both sides have done an excellent job in defining and defending their points of view, but Joe Pilot has shown a greater degree of first hand knowledge, and more accurate analysis of the accident statistics.

Congratulations to both sides on an excellent job in presenting your case. The discussion has gotten down to a re-hash of counter and counter-counter points that are now becoming a little repetitious, but I can understand that each side has worked hard to present their side, and neither wants to let up. It may be time to put this one to rest for now. By all means you should certainly carry on if you feel the need, but the fellow readers Iíve spoken with all share the opinion that youíve each accomplished what you intended to. Thanks again to both of you and to all others that contributed.


[This message has been edited by HeliFlight (edited 28 September 2000).]
 
Old 28th Sep 2000, 19:02
  #38 (permalink)  
JoePilot
Guest
 
Posts: n/a
Angel

Thanks for your support guys...

I was feeling pretty shy about speaking 'in public'. PPrune is FAB people's true viwes protected by anonimity.

Ageed .. yup boring now. Enough!

Flown properly most small ones (from Brantly to AS350). Learnt in H300,H500,Allouette.

Been a spare dick in S76,Dauphin,Puma,Augusta,Mil2and8,Kamov(luvly)etc.

Been 'around' a bit also....

Strong science background...

Just about managed to get a license for aeroplanes (but much harder than helis) and done a bit of that, though not very well...

And type arguments are mostly daft.... All helicopters are the best at some basket of criteria. (eg. B206 is a better 5 seater than an R44, and you can burn some pretty exotic fuels if you have to - could be vital)

It just gets difficult when someone decides they don't like something but they haven't got their reasons right yet.

I hate it when you can't say something you know (factually) to be the case because its not the 'official line'.

Pleased to be here..
JOE

 
Old 28th Sep 2000, 20:11
  #39 (permalink)  
Lu Zuckerman
Guest
 
Posts: n/a
Post

To: Joe pilot and the others. I sent this news article to a lawyer friend that tried three cases against Robinson and won all three. However as I stated previously he and his clients didn't collect a cent because Frank Robinson hides his money in offshore accounts. I know Joe that you are basking in the glory of having been published as I too felt the same way when I first saw my name in print.

Deat tim,

Here is the accident report from Heli-News.

In Flight Separation Caused Showcopters
Accident
September 5, 2000

(WATSONVILLE, CALIFORNIA - HELI-NEWS) - An in-flight
separation of a main rotor assembly caused last month's
Robinson R-22 accident that claimed the lives of a veteran
pilot and a student, according to a preliminary report from
the National Transportation Safety Board.

N8313Z went into an uncontrolable decent, crashed into a
field, and burned, the report says.

Killed were 57-year-old Kent Reinhard, an airline
transport-rated pilot with thousands of hours of flight
experience and a member of the Showcopters aerobatic
team, and 46-year-old student pilot Gary Sefton. It was
Sefton's first helicopter lesson, according to local news
reports.

The NTSB said wreckage from the helicopter was scattered
for hundreds of feet around the crash site. "Plexiglas, and
headphone fragments [were found] about 470 feet north of
the main wreckage," the report said. "Sunglasses and a
headphone's ear cup were found about 330 feet north of the
wreckage."

Showcopters performs aerial stunts with a Robinson R-44
Newscopter and a pair of Robinson R-22s. At a recent show
at the San Carlos Airport near San Francisco, Showcopters
director and lead pilot Jim Cheatham described Reinhard as
a 20,000-plus-hour agricultural pilot. Cheatham and
Reinhard had been flying aerobatics together since 1996,
according to the company.

The Showcopters website contained a simple news item
regarding the crash. "Our grief is indescribable. A
celebration of Kent's life will be held at Watsonville Airport
on September 23."

Copyright 2000 HELI-NEWS. All rights reserved.

The airshow team in some cases flew their helicopters backwards while
spewing white smoke. I am going to send a picture of one of them in this
situation. Note the direction of the smoke. Although the air currents
around the helicopter may account for the direction of the smoke but most
likely he was flying out of trim and in a rearward side slip both of which
are forbidden by the POH and the FAA AD .

Best regards,

Lu Zuckerman
[email protected]

PS I sent my report to Jim Hall at NTSB and in closing the cover letter I
told him I had also sent it to Dateline NBC. Yesterday (Labor Day) I
received an email from Mr. Hall telling me that he had assigned four
engineers and they were reopening the investigation.

Maybe, Justice will be served, but a bit late for the pilots and passengers
in the 32 Robinson Helicopters that lost their rotors or had a rotor
incursion.

20,000 hours doesn't help if you cross the line or if repeated overstress finally lead to the mast fracture. Only time will tell.

To Joe Pilot and the others I will try transfer the above referenced photo but, I don't think I can.



------------------
The Cat
 
Old 29th Sep 2000, 00:52
  #40 (permalink)  
4Rvibes
Guest
 
Posts: n/a
Post

The thing is, Lu's report in engineering terms proves or at least puts a very strong case forward for the non-certification of R22's/44's.
Joe on the other hand has a valid point in that he has flown the machine and is still alive to tell the tale.
As an independant and unbigoted witness I will always take the the side of someone who looks at the past AND the future and can consolidate a reasonable point of view from both as opposed to all of the Robbie ex-trainees I spoke to who merely reiterated their instructors retoric.
For info, one of the guys I spoke to, now a twin turbine IFR Captain who learned on the Robbie, said that he, "was demonstrated and taught low G, out of trim and sideslip manouevers" as part of his basic training.
If this doesn't count as disreputable behaviour (ie. conradicting the flight manual) I don't know what does.
 

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell or Share My Personal Information

Copyright © 2023 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.