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Certification of Robinson Helicopters (incl post by Frank Robinson)

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Certification of Robinson Helicopters (incl post by Frank Robinson)

Old 13th Sep 2000, 21:09
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Lu Zuckerman
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Thumbs down Certification of Robinson Helicopters (incl post by Frank Robinson)

If anyone is interested in why the Robinson R22 and R44 should never have been certificated by the FAA please contact me. Please provide your email address and your interest in the subject and I shall send you a copy of a report submitted by me to the NTSB.

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The Cat
 
Old 15th Sep 2000, 14:49
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WhoNeedsRunways
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Lu :

Thanks for your copy of the report.

I have one question. In the "Questions to the FAA/Robinson" bit, you ask of Robinson and the FAA "Why are two bladed rotor systems susceptible to "Zero G" maneuvers".

I see from the document and your mail that you provide substantial references to being in helicopter engineering for a long time. But you can't answer yourself why teetering heads are subject to low-g intolerance.

I learnt about this BEFORE I started to fly R22s, and subsequently on a training course. Every R22 pilot I know of knows to avoid low G. I am curious as to how you got your experience on R22s, and if something as basic as this can be missing from your repertoire, I'll be taking the report with a huge pinch of salt. There are other things in the report I take issue with, but will give deference to your credentials as an experienced engineer, while I've only got 60 rotary hours.

One last thing. Bell 47s, Bell 206s use teetering heads. Robbies are the most numerous training helicopters going, yet still manage an ( acceptably in my opinion, maybe not in others ) low accident rate even when flown by very low time pilots. When it was introduced the major problem was lack of rotor inertia, not mast bumping. Pilot education has reduced that dramatically.

And unless you'll subsidise me, I can't afford to fly much else.

[This message has been edited by WhoNeedsRunways (edited 15 September 2000).]
 
Old 15th Sep 2000, 19:01
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Lu Zuckerman
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Dear WhoNeedsRunways.

Here is the question you mentioned in your posting.

Robinson / FAA Why are two bladed rotor systems susceptible to "Zero G" maneuvers and three or more rotor blade systems are not? Why was a two bladed system selected over a multi-blade system for use on a helicopter that would be operated by pilots who have minimal "stick" time or students learning to fly helicopters?

The first part of the question sets up the second part of the question. Anyone that has learned helicopter theory of flight can answer the first part of the question. My intent was to get them to answer the first part and then explain why they designed a rotor system that that would place pilots in jeapordy.

Regarding your thoughts on the safety of the Robinson design, there have been 32 loss of rotor or fuselage incursion accidents on R22 and R44 helicopter. The most recent was about three weeks ago in California. The Instructor pilot had many hours in the Robinson as well as thousands of hours in other helicopters and fixed wing aircraft. He was also a member of an acrobatic team the flew 22s and a 44. He not only lost control, he lost his main rotor. If we assume that both helicopters have collectively flown 1.000.000 hours we can divide that figure by 32 we get a mean time between rotor loss or fuselage incursions of 31,250 hours. The FARs require that single point failures be designed out of the system and if they can't be, it must be statistically demonstrated that the occurance of an accident involving loss of life should occur no more frequently than 1 10-9 or, 1.000.000.000 hours. In this case, it is the design of the rotor head that sets the up the accident. Regarding low blade inertia, you forgot one other thing and that is, excessive pitch, which can induce rotor stall,not retreating blade stall as that is an entirely different subject that we can get into another time.

The very nature of the rigging procedure and the design of the rotor head can cause the mechanic to rig in too much pitch.

If you wish to demonstrate the design defect of the Robinson rotor head do the following.

Place the blades over the longitudinal axis and move the cyclic from its' rigged neutral position forward and aft. The blades will move. Now, rotate the blades so that the pitch link is directly in line with the same axis. Move the stick in the same manner. The blade won't move.

Now, do the same thing with the blades over the lateral axis and move the cyclic from its' rigged neutral position both left and right. The blades will move. Now, place the pitch link directly over the lateral axis and move the stick left and right. The blades will not move. Now, do the same thing with a Bell. With the blades in the positions described above and the cyclic moved as described above the blades will not move. If they do, it will be very slight due to possible pitch coupling in the rotor system.

Regarding the fact that the rotor system has a design defect you might wonder why the FAA approved the design. It might be that Frank Robinson was the FAA Designated Engineering Reoresentative or, DER. FAA regs state that the DER cannot have a vested interest in the design or a financial interest in the company. This was brought to the attention of the FAA by the NTSB but neither agency took any action to correct the infraction of the regs. If the helicopters had been subject to the regs relative to certification you wouldn't be flying in an R22 or R44. Another point is that the R22 and R44 are the only aircraft that are restricted from flying out of trim or being sideslipped. Yet, the certification requirements state that sideslips of 90 degrees should be demonstrated as well as flying out of trim +/- 10 degrees. If the two helicopters were put up for certification with those restrictions which were mandated by an FAA AD the two helicopters could not be certified.

Low rotor inertia and mast bumping were the reasons , according to Frank Robinson, why the helicopters were lost. That way, they could blame it on the pilot and not on the real culprits, Rotor head design and the rigging procedure.

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The Cat

[This message has been edited by Lu Zuckerman (edited 25 October 2000).]

[This message has been edited by Lu Zuckerman (edited 27 October 2000).]
 
Old 15th Sep 2000, 21:58
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Reg C Elley
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Isn't the correct term 'Mast Bump', as I believe you only get to do it once!!!!
Then you die!!!!!
 
Old 15th Sep 2000, 22:39
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Lu Zuckerman
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If it severe enough then you are correct. But the rotor can contact the mast and if the pilot can correct for the condition the worst thing that could happen is that the mast has a concentrated stress and could let go under entirely different conditions. That way, the mast bumper lives and the mast bumpee dies.

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The Cat
 
Old 15th Sep 2000, 22:40
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Flying Lawyer
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I'm no engineer so can't improve upon the valid comments made by WNR.
I hope I'm not being unfair, but I can't help wondering whether Lu started his research with an open mind, forming a conclusion based upon the facts which he found - or started with his conclusion, and then selected facts to support it. It does make a difference.

Doesn't the accident rate merely reflect that the R22 is the most popular training helicopter worldwide, and is usually flown by PPLs (like myself) rather than professionals?
The R22 isn't easy to fly well, but isn't that a desirable feature in a trainer?
The R44? Although I now prefer flying the JetRanger and the Gazelle, the later R44s (particularly the hydraulic new version) are a pleasure to fly.

Note:
Having suggested that Lu might have some prejudices, it's only fair that I should declare mine: Well done Frank Robinson for opening up the helicopter world to so many of us!
 
Old 15th Sep 2000, 23:04
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Lu Zuckerman
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Dear Flying Lawyer,

I repeat the first paragraph of your post.

I'm no engineer so can't improve upon the valid comments made by WNR.
I hope I'm not being unfair, but I can't help wondering whether Lu started his research with an open mind, forming a conclusion based upon the facts which he found - or started with his conclusion, and then selected facts to support it. It does make a difference.

I started my investigation after three years working for Bell and being made aware of the mast bump, rotor loss phenomenon and having participated in an accident investigation of a rotor separation that occured after the helicoptwer landed and was in process of shutting down. But that is a story in itself. If you read my bio it states that I am concerned with the safety of passengers and crew. My interest in Robinsons and their collective problems when I saw a rotor head that was removed from an R22. For a two bladed helicopter the pitch horns lead the blade by approximately 72 degrees instead of 90 degrees on the bell. I got copies of the POHs for the 22 and the 44 as well as the maintenance manual for the 22. I started reading them and found that the pilots were restricted from side slip and out of trim flight. This I firmly believe was a means of covering up the design deficiencies of the rotor head. The design is such that if you fly out of trim or in a side slip the flapping loads would be so severe that the rotor system could be damaged to the point of failure. If the rotor system cannot be flown now in a side slip or out of trim condition then please explain to me how the helicopters could have been certified because in order to be certified they must demonstrate those flight regimes.

This is my personal opinion about Robinson pilots is you have been brain washed
by the Robinson doctrine. There is going to be a safety course that is being taught in the UK by a Robinson instructor.

If anyone reading this attends please ask the man about the 72 pitch horn lead and the 90 degrees of precession of the blades. Ask him how the pilot compensates for this 18 degree difference between the Robinson and the Bell.

[This message has been edited by helidrvr (edited 07 October 2000).]
 
Old 15th Sep 2000, 23:25
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Lu Zuckerman
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To Flying Lawyer.

One point brought up by you was in response to the accident rate of 45,454 between accidents. First of all this is astatistical mean. and, it reflects accidents that occured in large numbers over a rather short time period. Since the AD that restricts the side slip and out of trim flight was implemented there were no more accidents that is until three weeks ago when an R22 lost its' rotor in California. You state that the Robinson helicopters are the most widly used helicopter for initial training and that many of the are flown by PPLs and not professionals. That is the major problem. If you are restricted from side slipping and flying out of trim how do you think you will react when you move up on the helicopter food chain and find out that every other helicopter can be side slipped and flown out of trim within design limits.

Getting back to the 45,454 hours between accidents what are your thoughts about this.

Let's say there are 1000 Robinsons flying and each one flys 45.45 hours. From a statistical standpoint one Robinson will lose its' rotor or the rotor will hit the tail cone or the cockpit area. Do you want to be the one that is flying when the total flight time hits 45.454 hours. The only safety device you have to protect yourself is the last page of section 4 of the POH

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The Cat
 
Old 17th Sep 2000, 13:42
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WhoNeedsRunways
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Lu :

Some clarification re your last but one post, if poss.

When did you start your investigation ? You say it was after 3 years at Bell, and the date on the report is 1996.

The US military has been aware of this phenomenon since at least the Vietnam war, the video shown by Tim Tucker on my safety course dates to early 1970's.

BTW, Tim did some testing of the entry to and recovery from low g conditions, until he decided it was a bit silly ( English understatement, not sarcasm or irony ).

My copy of the R22 POH doesn't have a sideslip or out-of-trim limitation anywhere in the Limitations section. Nor is out of trim or sideslip mentioned in the safety notices at the back of the POH.

Perhaps it's in the Eng manual - useful for pilots, eh ?

Is there an R22 instructor anywhere in the UK reading this who'd like a gander at the report as well ?

[This message has been edited by WhoNeedsRunways (edited 17 September 2000).]
 
Old 17th Sep 2000, 17:33
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Lu Zuckerman
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I worked for Bell Helicopter International in Iran from 1974 to 1977. It was during that time that I became aware of the mast bumping and resultant rotor loss. The last Bell helicopters that I had anything to do with prior to that time never had the problem because the rotors were restricted in their flapping by Sprague Cables. The reciprocating engines were also restricted in their movement by the same type of cables.

It wasn't until the advent of the 206 that the problem of mast bumping started and continued with the 205. I am not aware of mast bumping occuring on any follow on models. I first became aware of mast bumping
0n the Robinson when I visited Geneva Aviation in Everett,Washington. Geneva specializes in A Star and Twin Star helicopters but they were pulling maintenance on R22s that were owned by the president of Geneva. The lead mechanic told me about the problem and I also saw some unusual wear on a R22 rotor head. Being of an Inquisitive nature I started my investigation. That was around 1990-91.

Prior to publishing my report, I contacted Robinson Helicopters to tell them of my findings. I sent two faxes with no reply. I phoned Robinson and talked to Kurt Robinson, Franks son. he informed me that they weren't interested. It was then that I decided to send the report to the NTSB.

Regarding you not having the referenced page in your POH then the CAA has a major problem.

Regarding the pages in section 4 (Normal Procedures) they are (at least in my copy);

4.1,4.1 (page number repeated but with different info), 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 4.10, 4.10.1, 4.10.2, 4.11
and the last page is un numbered. This page is titled normal procedures section NOTE. This page addresses Main Rotor Stall and mast Bumping and has a section that sets up the restrictions to avoid these conditions and one of the notes reads; Avoid sideslip during flight. Maintain in-trim flight at all times. At the bottom of the page it states: Issued Per FAA Priority Letter AD Dated: 13 Jan 95. I think you should talk to your Robinson dealer and ask why this page is not in you POH. This same page is in my copy of the R44 POH

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The Cat
 
Old 17th Sep 2000, 17:53
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Lu Zuckerman
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To: WhoNeedsRunways,

Dear Who,

Please provide a fax number and I will send the page. This is a one time deal so use it wisely. Also, did you know that the R22 and R44 are the only helicopters that have such a restriction. By placing the restriction on side slip and out of trim flight any major accident involving rotor loss or rotor incursions can be blamed on the pilot having exceeded the stated restriction. The restriction was place to cover up a major design defect of the Robinson rotor head.

Please disregard my penned in notes on the page.

Regards,

Lu Zuckerman
[email protected]

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The Cat
 
Old 17th Sep 2000, 22:51
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WhoNeedsRunways
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Lu :

I found the page, thanks to your numbering. I obviously hadn't looked as hard as I'd thought.
 
Old 19th Sep 2000, 04:07
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Arkroyal
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fish

I've often wondered how these machines were ever certificated.

Is it true that instructors are warned not to give eng fail exercises in the climb without fore-warning the stude, as no-one has fast enough reactions to maintain RRPM otherwise?!!

Flying Lawyer, yes, Frank has put helo flying in to the realms of the paying pilot, but you will admit that it has a pretty poor accident record. As you now fly the Gazelle,a brilliant machine, I think you will agree that the robbo is not the helicopter for the beginner or the hamfisted.

None of my 4000+ helo hours are in the Robbo, as my mum told me never to fly anything which can have a mid-air collision with itself, and it seems to me that the only difference between the 44 and 22 is the potential number of deceased.

To put the most difficult helo to fly in the hands of the least experienced seems akin to starting a PPL in one of your beloved warbirds!

 
Old 19th Sep 2000, 04:19
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Lu Zuckerman
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Dear Ark,

Some of the points you made are contained in my report to the NTSB. If you would like a copy please contact me and I'll send it along.

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The Cat
 
Old 19th Sep 2000, 23:35
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Flying Lawyer
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Ark Royal
Your point about "putting the most difficult helo to fly in the hands of the least experienced" is a fair one.
However, proper instruction on the specific dangers of lack of inertia/mast-bumping should make the Robinson pilot aware of the potential dangers, and how to avoid them etc.
If my posts suddenly stop - I was wrong!!!

Agree with you about the Gazelle - amazing machine. No contest.
(Don't tell anybody, but I prefer heli's to my "beloved warbirds" these days!!)


[This message has been edited by Flying Lawyer (edited 19 September 2000).]
 
Old 23rd Sep 2000, 22:39
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JoePilot
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Does our 'engineer' drive one of those 'dangerous' cars that allow the driver to turn the steering wheel the wrong way and drive off cliffs.

The control is in your hand - you chose what you do with it.

I'd rather fly something which was mechanically sound. The Robinson - sadly for it's detractors does have the most remarkably good mechanical saftey record.

It is really a pilot choice issue if the pilot wants to fly into mountains or bump his mast.



[This message has been edited by helidrvr (edited 23 September 2000).]
 
Old 23rd Sep 2000, 23:48
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Lu Zuckerman
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Dear Mr. Pilot.

Before going off half cocked regarding the magnificent safety record of the Robinson Helicopter fleet I would suggest that you read every one of the above postings.

The operational envelope of the R22 and the R44 is so highly restricted that if you exceed these restrictions you may as well put a gun to your head and pull the trigger as the results will be the same. These helicopters have a really bad safety record.

So far there have been 32 accidents involving the loss of the rotor or the incursion of the rotor into the fuselage and/or tail boom. The last one occurred last month in California and the pilot had very high time. Because of the restrictions placed on both helicopters they don't meet the certification requirements of being able to demonstrate side slip and out of trim flight.

There is another thing you might not be aware of and that is; If Frank Robinson were faced with a massive law suit as a result of the crashes he can just walk away from the factory. I have a lawyer friend in California that won three cases against Robinson Helicopters and his clients were awarded millions of dollars but, they never collected a cent. Frank Robinson does not own one thing in the Robinson plant. Everything is leased and he keeps his money in offshore accounts that are so far legally untouchable. That's what he thinks about his owners and operators.

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The Cat
 
Old 24th Sep 2000, 23:29
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JoePilot
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Strikes me you are sad that you're not going to get the pay out as 'expert witness' in the big case.

Yes I read the thread, and have followed this topic closely over many years.

A friend carefully tried tiny incremental approaching of the limmits at low g some years ago. He very very nearly killed himself and told a friend about it. The friend tried it too and did kill himself.

Also I know of two others who killed themselves experimenting with the envelope in this area.

PILOT CHOICE! (sad though)

Sure disseminate information which will help people understand what is not an appropriate set of manoevers and why in helicopters with this general type of rotor head BUT dont DISTORT the issue with your bias.

You would sound less biased if you acknowledged that both R22 and R44 do have the most REMARKABLY GOOD MECHANICAL RELIABILITY RECORD.

I think it is wrong for you to include PILOT ERROR incidents with MECHANICAL RELIABILITY.

If you want to fly an amazingly SAFE machine then Robinson is it. It is (you surely cant deny) very well designed with superb performance.

I think you are part of the old school (often quite arrogant though not neccessarily in your case)which likes bigger, more complex, more engines, more systems ... will design systems to fix problems rather than design no need for systems etc.

You choose whether you drive your car head-on into the on-comming traffic only you stop yourself turning the wheel in your hands. This is of course the case when you hold a control for anything... so of course you can bump your mast if you want.

Your answer maybe that the narrowness of the acceptable envelope is excessive - but that is just not the case. It is an amazingly big envelope - I REALLY DO know (sorry you'll just have to believe me!)

So calm down - take another look - be real.

Joe
 
Old 25th Sep 2000, 00:52
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Lu Zuckerman
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To: Joe Pilot,

Regarding the big payout as an expert witness, that has never been my intent. But if the $$$$ are good enough I would give it a shot.

You mentioned that a friend almost killed himself and another did kill himself exploring low G flight. However, you did not reveal what type of helicopter they were flying. Then you stated that two other individuals killed themselves in a similar manner and again you did not state the type of helicopter they were flying. I am not trying to get you to say that it was in an R22 or an R44 because Bell helicopters can get just as nasty when you get into a low G situation. If it was in fact they were flying a Robinson helicopter I can almost guarantee that it was ruled pilot error.

Your analogy about driving head on into traffic is in fact correct. It is the drivers’ decision as it is the pilots’ decision to ignore the limitations placed on his aircraft. However, you must ask yourself why the restrictions were placed on the aircraft in the first place. From 1981 to 1995 there were 31 fatal accidents involving rotor loss or rotor incursions. The FAA commissioned Georgia Tech School of Aeronautics to analyze these accidents and come up with a solution to keep it from happening again. First out of the box it was assumed that all accidents were the result of pilot error. They concluded that extremely high flapping loads would be incurred if the helicopters were flown in a sideslip or flown out of trim. They also indicated that the rotor system being of the low inertia type would be subject to stall and/ or would have a serious effect when initiating an autorotation. All of this is true but the report and the subsequent report issued by the NTSB completely overlooked to major points. The design of the rotor head and the rigging procedures.

During the certification, the helicopter had to demonstrate a side slip angle of 90 degrees initiated by a rapid input of maximum left or right pedal input. Also, the helicopter had to demonstrate flying out of trim left or right by 10 degrees. Now, think about this. Since 1995 the helicopters (22 and 44) have been restricted from flying out of trim and from being side slipped and up until last month there were no more accidents as described above. Since the design of the rotor head is the same now as it was when the first ship ran off the production line how did the helicopter get certified then if it can’t do those things now?

If you think I am biased by telling you that Robinson helicopters have a demonstrated bad safety and reliability record think about your own bias in supporting the reputation of Robinson Helicopters when faced with proof that you are wrong.

First of all, you have to understand where I am coming from. I am an engineering consultant specializing in Reliability, Maintainability and Systems Safety and I don’t specialize in just rotary wing aircraft. As an example just look at the tech log section of this forum under problems with Airbus Aircraft. The arguments on that forum are just as heated as they are on this forum. Whether I am addressing Helicopters or, Commercial Aircraft my only interest is in Safety and Reliability.

You might also ask why I don’t take my thoughts to Robinson Helicopters. In 1996 prior to writing my report to the NTSB I contacted Both Frank Robinson and his son Kurt. They completely ignored me. Also for your information, the NTSB has reopened their investigation on the 22 and 44 as a result of the rotor loss accident in California last month.

Why don’t you send me your email address and your fax number and I will send a copy of the report and a diagram that will help you to understand the problems outlined in the report.

One final point; the POH provides instructions on how to get out of a low G situation. The instruction states that the high mounted tail rotor will introduce a right roll and that the pilot should not try to counter the right roll by applying left cyclic. It tells the pilot to gently pull straight back on the cyclic until control is rgained and then apply left cyclic. However, the design of the rotor head is such that if you pull straight back on the cyclic you will in fact introduce a right roll component and lose the helicopter.
 
Old 25th Sep 2000, 13:16
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WhoNeedsRunways
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Lu :

If my recollection is correct, the advice in the POH for recovery from inadvertant ( or otherwise ) low G was determined after TESTING.

I'll say that again, differently. TESTING was undertaken by Tim Tucker, to determine how to recover from low G situations in the R22. When it started getting silly, they stopped, but not before they'd found that gentle aft cyclic ( and a tad of left cyclic as well, but that's not in the book ) would recover as safely as is possible. If it had led to major problems, then Tim wouldn't be booked to do a safety course next month in the UK.

I'm as satisfied as I can be, given the forum, that your credentials as an engineer are impeccable. I'm less than satisfied that you've ever flown in a Robbie, or even that you're a helicopter pilot. There is sometimes a huge gap between theory and practice, and it is this gap I have a niggling thought that exists in your knowledge of the situation.

Are there any more experienced guys out there who have read the document, or can express their thoughts with more practical experience than myself ? Those with preconceptions and not practical experience, i.e. zillions of hours in nothing less than twin turbine machines need not apply.
 

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