R22 Accident Analysis 1979-1994

[t'aint natural]

R22 accident figures

From Pilot magazine, January 2002:

The claim that the Robinson R22 helicopter is less safe than other models is put into perspective in a new accident analysis from aviation consultants PLH Associates.
A 'level playing field' comparison of accidents against numbers of hours flown over a five-year period shows that the R22’s fatal accident rate is markedly lower than that of the Schweizer 300/Hughes 269 or the Bell 206. The perception that the R22 suffers more accidents seems to arise from the fact that almost half of all single-engine helicopter hours in the UK are now flown on the machine.
PLH arrived at their conclusions after analysing 15 years of CAA data following a request from a client who wanted to know whether the R22 was less safe than other machines. “The answer is no,” says PLH director Neil Lunam. “The R22 is guilty of having driven an enormous growth in the number of helicopter hours flown, but not of causing an inconsistent growth in accident rates.”
The statistics come with the usual health warning. While accident figures are fairly accurate, the number of hours flown (put at 99,393 in 1995 and 197,576 in 2000) has been extrapolated from C of A maintenance records returned to the CAA. Furthermore, apart from the R22, R44, 300/269, 206 and AS350, few types flew enough hours to make their inclusion meaningful.
The number of fatal accidents is small – 15 over the five years – making one fatal accident equivalent to 6.7 per cent of the total and rendering it especially difficult to use percentages meaningfully for that parameter. But certainly at the high-hours end, the PLH figures are a useful indicator.
They show that 46.5 percent of the total hours flown by all single-engined helicopters in the UK were on the R22. The R22 was involved in about one third (35.66 percent) of all reportable accidents, and one fifth (20 percent) of fatal accidents (three in total). The R22 had one reportable accident for every 7,515 hours’ flying, and one fatal accident for every 115,213 hours.
The other main ab initio trainer, the Schweizer 300/Hughes 269, flew fewer than one tenth as many hours as the R22 (4.2 percent of the total) but was involved in ten per cent of reportable accidents, and 6.7 percent of fatal accidents (one). It suffered one reportable accident for every 2,380 hours’ flying, and one fatal accident for 30,939 hours – about three times worse than the R22 on both counts.
The figures for the Bell 206 show that while the machine had fewer reportable accidents, the chances of an accident being fatal were higher – perhaps indicating that greater weight and speed counterbalances docile handling and peerless autorotational behaviour. Apart from the R22, the 206 is the only helicopter with a big slice of the total hours, at 26.4 percent. It recorded one in ten (10.9 percent) of the accidents, but one in three (33.3 percent) of the fatal accidents (accidents, not persons killed). It had one reportable accident for every 14,047 hours’ flying – twice as good as the R22 – but one fatal accident every 39,903 hours – three times worse than the R22.
The AS350 Single Squirrel flew 8.4 percent of the total hours, had 3.1 percent of the reportable accidents and one fatal accident. This runs out at one accident for every 15,685 hours, and one fatal accident for 62,741 hours. The R44, which only began coming onto the UK market in appreciable numbers at the beginning of this reporting period, flew five percent of the total hours, had 3.9 percent of reportable accidents and 20 percent of fatal accidents. Its reportable accident rate, at one for every 7,488 hours is almost identical to that of the R22, but its fatal accident rate, at one for every 12,480 hours, is ten times worse.
Of the other machines only the MD500 series topped two percent of total hours, and then only just at 2.01 percent. The Enstrom 28, 280 and 480 series, the Bell 47, and the Gazelle all recorded around one percent, while the Brantly and the late-coming EC120 failed to make the scoresheet. The homebuilt RotorWay Exec stands out as having flown 0.55 percent of total hours while having had one fatal accident – a rate of one fatal accident for 4,068 hours airborne.
On these figures it’s impossible to conclude that any helicopter has a 'worse' accident record than any other, but it is clear that the R22 is a safer machine than is generally thought, and undeserving of the rap is so frequently takes. Pat Malone

[Lu Zuckerman]

To: T'aint natural

I won't argue with your statistics however, there is one important statistic that might be buried in the raft of numbers that made up the quoted statistics. That number is rotor loss or rotor incursion accidents. Your statistics may well have included the fatalities that resulted from these types of accidents but they do not attribute the deaths to any specific type of accident. It is my understanding that there were several rotor loss / rotor incursions in the UK in the last year or so and there were two in the USA and one in Scandinavia. The total number since service entry of the R-22 is in excess of thirty with the above accidents occurring within the last year and a half.

I know that you can say that these accidents occur mainly with low time pilots at the controls and that the primary use of the helicopter is as a trainer. Yet when questioned about the high death rate in R-22s and R-44s Frank Robinson stated that he did not intend the R-22 to be used as a trainer. I guess he visualized that some high time Bell pilot would buy one for his personal use or some similar scenario. One of the rotor loss / rotor incursion accidents in the USA had a pilot with 20,000+ hours and a first flight student and this was fifteen minutes after takeoff.

To prevent the rotor loss problem Robinson has placed in the POHs for the 22 and the 44 a suggestion that out of trim flight be avoided as well as side slipping as it can cause high flapping loads and result in mast bumping or rotor incursion. The only other thing that could cause this problem is the incorrect recovery from zero G. The Robinson is the only helicopter that has passed certification that is restricted from two areas that had to be demonstrated during certification.

[t'aint natural]

I thought you'd be out of the woodwork pretty quick.
Leave this one, Lu. Let the facts speak for themselves. Go ride your hobby horse some place else.

[helmet fire]

Lu,
your arguement revolves around the following premise:

>>Yet when questioned about the high death rate in R-22s....<<

What high death rate? Did we read the same facts above?
Bye bye your arguement.

[Lu Zuckerman]

To: t'aint natural

If you are interested in self protective statistics this was taken from a site that is sponsored by a Robinson distributor in the USA. Hopefully Danny doesn't take it off as it consumes a lot of memory. Because of formatting problems some of the statistical text and numbers may be jumbled.

Regarding my coming out of the woodwork, I am spring loaded to the response position whenever somebody out of product loyalty tries to tell how safe the R-22 is and leaves out the deplorable accident rate that ends up killing pilots and passengers. Those accidents revolve around the loss of rotors or the incursion of the rotor into the fuselage and for gods' sake don't talk about rotor loss on Bells as a comparison. If you want to compare the two look at the accident rate (rotor loss) on Bells since the introduction of the R-22

Robinson R-22 Accident Analysis 1979-1994
In this detailed analysis, it can be seen that most accidents are a result of pilot error (92% vs. 7%), and that the majority occur during flight training. The Robinson R-22 Helicopter as been the most popular training helicopter in the world since the early 1980's and, like the Cessna 152 and Piper 140, is exposed to training accidents.
The R-22 was introduced at a time when the helicopter industry reached a peak (1979), and hundreds of pilots were attracted to the industry. The relatively low-cost training and reduced insurance requirements allowed a new generation of non-military pilots to fulfill their dream of flying a helicopter. Prior to this time, the vast majority of helicopter pilots in the U.S., as well as most other countries, were ex-military.
The high cost of helicopter training and limited job opportunities kept most potential helicopter pilots away, and flight schools depend primarily on the G.I. Bill for students. High operating costs and poor mechanical reliability kept the personal/business flying to a minimum in the piston engine market, and the light single-engine turbines were just beginning to become popular by the late 1970's. The helicopter training industry was changed almost overnight as Bell 47's, Hughes 300's, and Enstrom F-28's were replaced with the sleek new Robinson R-22.
The world had never seen as much helicopter training outside of the military and this did not come without some problems. The first few years proved to be the most difficult as the new aircraft was "field tested" by flight instructors and pilots. A few mechanical problems occurred as the aircraft built up flight hours. Components were re-engineered and retested before being retro-fitted to aircraft in the field. One by one these problems were resolved.
Fortunately, the aircraft was introduced with the Lycoming O-320 engine, which is considered to be "bulletproof" by most pilots. The industry finally had a helicopter that would make it to TBO with very few problems. A "state-of-the-art" piston engine helicopter had achieved a record for reliability unmatched in the industry.
Even the NTSB has taken note of the R-22's extremely low accident rate due to mechanical problems. Will this American success story survive? Robinson Helicopter Co. recently announced that it has laid off 71 employees as a direct result of negative worldwide publicity. Further layoffs will probably occur in the near future unless the operators and pilots provide their input to the FAA and express their opinions on how best to prevent future accidents in the R-22.
Conversations with R-22 pilots from many countries reveal that many of them feel that the U.S. suffers from severe lack of flying discipline. There are fewer regulations in the U.S. than in most other countries.
The U.S. is still the world leader in the aviation industry, and more regulations will not solve the problem. The only solution is "self-regulation". Flight instructors must demonstrate through their own actions that safety is an attitude that must be applied to flying helicopters.
It is interesting to note that in some countries in- flight breakups have not been a problem. One United Kingdom flight instructor informed me that England has had only two similar accidents in 13 years, although over 250 Robinson R-22's operate there. Japan has not had a single fatal accident as a result of a rotor stall or mast bumping incident. Dozens of R-22 Helicopters are used for tuna-spotting in the Pacific without a single case of in-flight breakup, although these aircraft fly an average of 110 hours per month in often severe weather conditions. Australia, which uses the R-22 extensively for cattle mustering, has had few problems with this type of accident, but does not have the same intensive flight training activity found in the U.S.
A review of NTSB accident briefs clearly demonstrates that wire strikes are the primary cause of fatal accidents, followed by blade stall due to low RPM and continued flight into IMC. These are by far the most preventable fatal accidents and require intensive training in avoidance and prevention techniques as well as pilot judgement training.
An analysis of R-22 accidents by operator and geographical area indicates that a small percentage of operators have an unusually high percentage of accidents in a calendar year. Other operators with approximately the same amount of flight activity have very few accidents and will generally average one accident every 4 to 6 years.
The FAA, in its February 15, 1995 "Flight Standardization Report", has suggested several changes to the R-22 Helicopter. A few of these involve expensive modifications to the cyclic and collective controls. One of the suggestions involves an improved rotor speed governor system, although the present governor system proved to be very expensive to maintain and is not used by most pilots, especially in a flight training environment. Most experienced R-22 flight instructors agree that low RPM problems are a result of rapid overpitching of the collective, causing an RPM droop. This is similar to any powered helicopter RPM droop but, unlike a turbine, the throttle in the R-22 will respond immediately if the pilot is properly taught how to coordinate the throttle/collective without relying on the correlator or the governor.
Another suggested change is a redesign of the cyclic control system to allow increased accessibility to the controls by each pilot. A modified R-22 cyclic was developed several years ago. It has not found any acceptance with any R-22 operators. Apparently the operators do not feel that this system is a cost effective improvement over the T-Bar arrangement that RHC offers. I have personally flown with this new system and although it did have a heavier feel than the R-22 cyclic and is more representative of a conventional cyclic, I feel that there are several drawbacks to the design. The cyclic is heavier than the present system in an already weight sensitive aircraft. The design is extremely bulky and would be prone to control interference if an object was dropped between the lateral support tube and the pilot's seat during a critical flight condition.
Most operators are convinced that the problem is not in cyclic design and that a new design at this stage will create other unforseen problems. If a retro-fit were required, the change may cause problems for low time pilots due to negative habit transfer. A strong plus in favor of the RHC system is that it is easy for a flight instructor to gain unrestricted control of the aircraft in an emergency by simply pulling down his/her cyclic thereby lifting the other cyclic up and out of the hands of the student. A few simple training techniques that some R-22 flight instructors have been teaching for years will prevent most training mishaps.
Flight instructors in all helicopters are usually taught to divide their attention between the outside and inside of the cockpit when dealing with students. Most will develop their own scan technique but very rarely are told what to look for. Instructors should be advised to maintain constant vigilance of cyclic movements by directing their attention across the cockpit and not forward. Peripheral vision will allow the instructor an outside view of pitch/roll changes , but it also allows the instructor to monitor aircraft instruments and, most importantly, the students control movements. Instructors, for the most part, are taught to react to changes in physical sensations and pitch/roll changes (attitude changes) but are rarely taught that it is much more important to watch the students control movements.
Attitude changes will not occur instantly, as a result of rotor damping effect and aircraft inertia. The instructor can be taught to make corrections before a change occurs simply by watching the cyclic movements that the student is making. Even sudden, large control movements can be corrected immediately, before the aircraft can respond. The location of the cyclic on the R-22 actually makes this easier to observe as the instructor is not forced to direct his vision downward to observe these actions. This teaching technique also allows the student to recognize that he is in full control of the helicopter and that the instructor is not "hugging" the cyclic control. When a critical situation does develop, as when the cyclic is pushed forward and out of the instructor's reach, the instructor must be taught to grab the center post or hinge to gain authority.
R-22 Accident Review (NTSB Data)
YEAR TOTAL MECHANICAL PILOT UNDETER-
FAILURE ERROR MINED

PROBABLE CAUSE/NO. OF ACCIDENTS


1979 0 0 0 0
1980 6 2 4 0

A(2),B(1),C(1),D(2)

1981 20 4 16 0
A(4),B(4),C(8),D(3),G(1)

1982 22 1 21 0
A(1),B(7),C(4),D(2),E(1),F(2),G(3),J(2)

1983 19 3 15 1
A(3),B(6),C(2),D(1),E(1),F(1),G(1),J(2),K(1),L(1)

1984 14 0 14 0
B(4),C(1),D(1),E(1),G(1),I(2),J(1),Q(2),R(1)

1985 17 0 17 0
B(5),C(4),D(3),E(1),G(1),Q(2),R(1)

1986 20 1 18 1
B(2),C(2),D(3),E(2),G(3),H(1),J(2),L(1),M(1),Q(2),K(1)

1987 17 3 13 1
A(3),B(2),C(1),D(4),E(1),G(3),J(2),K(1)]

1988 15 0 15 0
B(6),E(3),I(1),J(4),Q(1)

1989 18 1 17 0
A(1),B(3),C(3),D(1),E(1),G(2),H(1),I(1),J(1),Q(4)

1990 35 2 33 0
A(2),B(9),C(6),D(6),E(1),F(1),H(1),I(1),L(1),M(1),Q(1),R(1), U(4)

1991 39 2 37 0
A(2),B(11),C(9),D(6),E(4),F(1),G(1),H(2),J(2),M(1)

1992 34 0 33 1
B(3),C(11),E(3),F(3),G(6),H(1),I(1),J(5),L(1)

1993 31 0 31 0
B(6),C(3),D(8),E(3),F(1),G(6),U(1),N(1),O(1),P(1)

1994 27 5 22 0
A(5),B(9),C(3),D(2),E(3),G(1),H(1),J(1),Q(2)


Totals 334 24* 306** 4


* Percentage of accidents caused by mechanical/engine failure (7%).
** Percentage of accidents caused by pilot error (92%).
Notes
1. The number of Robinson R-22 helicopters has grown steadily from approximately 35 in 1980 to 745 in 1994 in the U.S.
2. All information was obtained from the NTSB. A few non-injury accidents go unreported (i.e. ground damage due to severe weather, etc.) Most of these are usually not insured by the owner/operator.
3. Most of these accidents are caused by several related factors and probable causes may tend to be misleading (i.e. a roll-over may be caused by loss of tail rotor effectiveness, excessive slope or unsuitable terrain, etc.).
4. Mechanical failures are often caused by improper maintenance procedures or exceeding limitations (overspeeds, etc.). Approximately one-half of these appear to be attributed to this. In many cases, the pilot misinterpreted or reacted improperly to a minor problem in flight.
5. Most of the survivable accidents were attributed to pilots getting behind the power curve as a result of high density altitude conditions, downwind approaches, etc. whenever low RPM is a factor.
6. Approximately 30% of accidents due to autorotative landings appear to be caused by carb. ice. In many cases the pilot reported an engine failure during power recovery on a practice autorotation or reported a rough engine followed by failure when power was reduced for a landing. The NTSB notes that carb. ice conditions were favorable in many of these and a post-accident engine run up found no mechanical problems.
ALL OF THESE ACCIDENTS WERE AVOIDABLE!

PROBABLE CAUSES NUMBER OF ACCIDENTS

A. MECHANICAL/ENGINE FAILURE......................24
B. ROLLOVER.......................................78
C. HARD LANDING (AUTOROTATION)....................58
D. HARD LANDING (OTHER)...........................42
E. WIRE STRIKE....................................25
F. LOW 'G' MAST BUMPING............................9
G. LOW RPM (FAILURE TO MAINTAIN RPM)..............29
H. CARB. ICE.......................................7
I. FUEL EXHAUSTION.................................6
J. WEATHER........................................27
K. UNSUITABLE TERRAIN (LANDING)....................2
L. UNDETERMINED....................................4
M. CONTROL INTERFERENCE............................3
N. MID-AIR COLLISION...............................1
O. OBJECT STRIKING AIRCRAFT........................1
P. COLLISION WITH AIRBORNE OBJECT..................1
Q. COLLISION WITH GROUND OBJECT...................14
R. PERSON ON GROUND WALKING INTO TAIL ROTOR........3

Total..........................................334

THE PILOT ERROR RATE WAS SHOWN TO BE 92%. PLEASE KEEP THIS FACT IN MIND, EITHER FRANK ROBINSON OR ONE OF HIS DESIGNEES WERE ON THE ACCIDENT INVESTIGATION TEAM. I HAVE A NEWS PAPER ARTICLE TITLED: CONFLICT OF INTEREST ALLEDGED IN FAA CRASH INVESTIGATIONS. THE ARTICLE WENT ON TO SAY THAT FRANK ROBINSON OR HIS DESIGNEE EXERTED UNDUE INFLUENCE IN THE INVESTIGATION WHERE HIS/THEIR POSITION WAS ONLY AS A TECHNICAL ADVISOR.

[ 12 December 2001: Message edited by: Lu Zuckerman ]

[ 12 December 2001: Message edited by: Lu Zuckerman ]

[Lu Zuckerman]

To: All

Since the first post was supportive of the Robinson design and it was taken from Pilot magazine I will provide and excerpt from an article by Maria Malikoff a staff writer for the Santa Cruz, California Sentinel. She wrote a whole series of articles about the Robinson safety record and especially about a rotor loss accident that occurred in Watsonville, California a neighboring city to Santa Cruz. She won a lot of awards for her series on this problem. Here is the excerpt of the article and it is the first three paragraphs of the story:

Of the dozens of R-22 accident investigations involving main rotor loss reviewed by the Sentinel
, the NTSB frequently listed the probable cause as “Undetermined” or, pilot error—findings that do not surprise Palo Alto Lawyer Michael Danko.

Because pilots and victims’ families are excluded from the investigation process, fault often is placed with the pilot, he said.

“Unfortunately, when there is a crash such as this and the NTSB wants to examine whether the aircraft is defective…they call on all the manufacturers,” said Danko, who is also a pilot. “They’ll
ask Robinson if it is defective. To me, that is like asking the fox to find out what happened to the chickens.”

Danko, whose firm is investigating a fatal August 1999 R-22 crash in Ireland nearly identical to the Watsonville crash in August, said the NTSB will “essentially staple their technical report to the technical report from Robinson, which will always point to pilot error.

The article goes on in very much detail all of which supports the first three paragraphs.

[B Sousa]

For all of you high time Robbie drivers out there, maybe you should take the stats only of the low RPM accidents or rotor loss accidents and compare those to the other aircraft mentioned. I believe thats where Robbie has gained its notoriety. See how that fares. Im sure all the other training related accidents will be similar in numbers.
It would be interesting....
Times change, Ive been flying Bell products for 30 some years. Got into an A-star not long ago and may not go back to Bell...

[Nick Lappos]

What is the penalty for hi-jacking a thread on this web site? Did Lu take enough lines to (un)make his point?

The stats speak for themselves, as do the sales figures. Leave it, Lu.

[Lu Zuckerman]

To: Nick Lappos

I added the large post above to point out that Robinson dealers will provide the accident analysis above to bolster the safety record of the R-22. It is totally self-serving and it does not go into detail about the causes of the loss of the rotor or mast bumping.

I do not know how long you have been following my various posts about the Robinson design but one thing you would have derived is that I have never attacked the reliability of the design. To my knowledge the Robinson R-22 has suffered only one crash due to a part failure. I’m not addressing the engine. In this case the helicopter crashed due to a faulty weld and excessive feed back that caused the weld to fail.

From maintainability point of view Frank Robinson designed a maintainable helicopter. However if you examine the rigging procedure you will find that it totally sucks as does the design of the flight control system. The Certification for normal rotorcraft requires that the system have controllable stops. This allows the mechanic to set the blade angles and to adjust the stops to limit further travel. This is true in almost every helicopter but not on the Robinson. It has a control stop plate that limits the control ranges and the blade angles are adjusted to the stops. The neutral blade angles are set with the cyclic in the rigged neutral position, which means that forward and aft cyclic have the same range. However if you move the cyclic to the forward stop and set the pitch angle and then you move the stick to the aft stop and set the pitch angle the two angles are not the same even though the travel from center is the same. If the mechanic can’t get the proper range then he must adjust the pitch link and eventually the control rods to the swashplate. In making this (these) adjustment(s) the mechanic will have changed the previous setting. He is told to check the previous setting which will have changed but he is not told what to do. I could go on and on describing the problems for the mechanic and how they can effect the flight quality and controllability of the helicopter.

Before you go off on another bash Lu Zuckerman attack I would suggest you familiarize yourself with the helicopter, the design of the rotorhead and how the down stops contribute to rotor loss and especially the rigging procedure. How many helicopters that you are familiar with that have flapping capability have a fixed down stop. The Sikorsky designs that I am familiar with have centrifugal (centripetal) operated stops that permit flapping above and below the radial position. The Robinson does not have this capability. Check it out.

[ 13 December 2001: Message edited by: Lu Zuckerman ]

[helmet fire]

Let me see if I can "unjumble" a bit of that stuff for you Lu.

1. The Sentinel says: >>Of the dozens of R-22 accident investigations involving main rotor loss reviewed by the Sentinel...<<
But the NTSB says : >>F. LOW 'G' MAST BUMPING............................9 (out of 334) <<
Verdict: Sentinel are basing story on misquoted figures/unprovable facts and therefore should be ignored.

2. Old mate said: >>[The] "state-of-the-art" piston engine helicopter had achieved a record for reliability unmatched in the industry. Even the NTSB has taken note of the R-22's extremely low accident rate due to mechanical problems.<<
The NTSB says: >>A. MECHANICAL/ENGINE FAILURE......................24.
Verdict: Mechanical failures are almost THREE times more likely to cause an accident than mast bump. Where is your systems reliability analysis of that? Roll Over is almost NINE times more likley. Should we rediesign it with extremely wide skids?

You have quoted more proof of the lack of statistical evidence to support your allegations. You continue to make the Robby look good.

[Nick Lappos]

Lu rides his hobby horse and rides and rides, closed mind, closed eyes.

It is sometimes not at all amusing how little he knows, and how much he posts.

[sling load]

Lu, I think your obsession with the R22 is that you don't understand it. The problem is, the more you dig in your position, the less likely you are to accept facts and continue your rhetoric. Be very careful using statistics to support your view. Statistics can turn against you very quickly. Two different Actuaries will use the same statistics to provide a different outcome.

[Vfrpilotpb]

Hey Lu,

I suppose its an age thing, but I tend to listen/read and absorb most of what people say and write, I then seem to follow my own instinct, but with a mind to what others have said.
Now then if you are ever able to drop off at Mnachester (UK), I'll come and pick you up and give you a couple of hours flying around the gently rolling hills of Lancashire, in a nearly new R22, I am by no means classed as a high timer, but I am very safety aware, I think in a normal flight you would be pleasantly supprised to see that unless you actually do something silly, the little R22 is quiet a good little bird, sure it has had accidents, but so have far more sophisticated birds, my attitude is that accident's will happen, it is down to the pilot of the craft to fly in the most correct way possible to mitigate any possibility's of an accident occurring to his flight, obviously you cannot know when mechanical failure is going to happen, but if you do all your pre-flights and checks, and observe the weather and where you are going to fly I feel that you have a more than fair chance of returning to whence you left, in a completly controlled manner.
I enjoy reading the posts from the members of Pprune and find that a lot of information written on these various threads in Rotorheads is first class and works in real life, but I feel that you may not have actually flown in the R22, so hence my offer, please feel free to E me if you do not want to make open comments to my offer it won't cost you a cent I'll pay! All you need to do is get here!

My Regards

PeterB

[thjakits]

HI GUYS,

do we have Lu up and roaring again?

Well I don´t know what you call hightime Robbie driver. Does about 3800 in Robbies count?

Lu, "correct me" if I am wrong:

If I remember right, Robinson uses an old Army-video in their (excellent!) Safetycourse. This video is about mastbumbing and loss of the rotor as a result, on Hueys... of all the big iron!! According to this report people did not really know what was going on, until further research showed, that pilots were not aware of the dangers of low g, as saveing ones butt was more important, and therefor they pushed the aircraft right over the hills to stay low, resulting...sometimes... in mastbumbing.

Now I do not have the insight in the very details of every helicopterdesign, but common sense I am able to use....sometimes...
About the droopstops Lu is complaining on the Robbie. Well they are fixed, so what, so are the ones on any other helicopter once the machine is running. I understand that most models use moveable stops (personally I know only the systems on B-47 and 206) to limit movement on the stopped or very slow rotor on runup or shutdown. Maybe it slipped Lu that the Robbies use FRICTION in their heads and quite a bit (AND it works beautifully!!), so when the rotor is slow or stopped the blades hardly flapp at all. Once very slow or stopped they seat on stops to avoid to much droop in the CONINGHINGES. So you would have to move the rotor by hand to move the head all the way to the flapp stops.

I was lucky to get a low g recovery demonstrated by the very Testpilot who did all the prototyp testing for the R-22. The gentleman not only likes the R-22 but to level things, has several 1000 hours in Hueys,Jet Rangers, CoastGuard Dolphines. Actually he is a Checkpilot for that CG-Equipment. So if someone would be biased to heavy iron, he should be.
Well to the low g: All it takes is proper training and flying with some brains. You will probably never encounter low g if you do not provoke it by pushing over to hard.
Besides the low or zero g is not the problem anyway - IT IS THE WRONG REACTION OF THE POORLY TRAINED PILOT - but of course we can always blame it on the design.
It seems in the US people have sometimes trouble to adapt to lightweight designs: I remember there was a big campaign by some ignorant "Specialists" to kill the Suzuki Samurai 4x4, because, supposedly, it flipped over to easy. Well if some braindead jerk thinks he can defy gravity and highschool physics, of course a light design will start to fly as it is at its max rather quick. However no one thinks about that it is built tot be light, and still people whant to carry the same stuff they just took out of thei Suburban!
How come however that the Zuki still maintains a side angle equal or better than other 4x4 offroad vehicles? (I drive a Toyota HiLux by the way...)

It seems to be the same problem with the R-22:

Well it is a small package and for that, limited in some areas - like the rotormass - but you can work around it, mainly with using the brain when flying. It is a very responsive machine and if you can work with it, size does not matter or better said it does matter: where I go with a R-22 no one else will go!!!

I learned to fly on Franklin powered B-47s. So I have an idea what you talk about pistonpowered reputation.
The Robbies do not fit that cliche at all.
Lu you still need to find a turbine chopper that has a faster reacting governor than either Robbie!!
Pleeeeease do not come back with carb icing problems they had in the beginning - that´s solved. ....so are the cracks in the tailrotor driveshaft couplings - and then they only had trouble with that when cattle herding in the outback - if you ever saw a R-22 in action like that, you´ll understand

-well maybe not.......

2 more points:

Of my total of about 5800 hrs I have only about 400 in turbine. The two times I got in non selfinduced trouble was in turbines (One time the first stage of the compressor in a 206 failed on me about 30 ft in the air on final with max gross weight. It took out the whole axial part of the Allison-compressor - we made it allright - long live high rotor inertia!!!
The other was a leaking fuel line in a EC120 - no sweat.. but could have been, with gallons of fuel departing the aircraft from the enginedeck drain......)

Never anything like that in Robbies I flew....

The other was a crashed R-44 (Student froze on the controls and what I can tell from the site and the reports of the instructor and student, the ship went upside down on takeoff and wound itself around a tree after chopping of a one foot branche of another tree - well at some time rotorblades give up and depart -
What I found in the wreckage was amazing: Parts that should be broken merly deformed extremely, but would not let go, least the rotorhead or mast. After seeing what this helicopter can take before giving up I will always choose a Robinson over any other helicopter if it is capable to do the job on hand - and it can do a lot of them a 206 can´t!!.....tested

Anyway Lu, why don´t you get a couple of hours in a R-22 some time, but watch out!

.......You migh like it!!


3top

[Flight Safety]

Try these stats, from an NTSB report dated 1996 regarding R22 loss of rotor control accidents. While the chart focuses on "LOC" accidents, it also provides overall accident rates for various types in the years covered.

The report is located at the following link, and the table was taken from page 12 (pdf page 20) of the report.
www.ntsb.gov/Publictn/1996/SIR9603.pdf

Table 1-U.S. Loss of control 1 (LOC), non-loss of control (non-LOC), and all fatal
helicopter accidents, flight hours, and corresponding accident rates for the years
1981-1994. by helicopter model.

Fatal Accidents -------------------------- Fatal Accidents per 100,000 flight hours
Helicopter Model a LOC non-LOC All --- Total Flight hours b LOC non-LOC All

Bell 206 - 2 119 121 --- 13,369,702 - 0.015 0.890 0.905
Hughes 369 - 2 38 40 --- 3,00,236(sic) - 0.067 1.267 1.333
Hiller UH12 - 1 13 14 --- 987,796 - 0.101 1.316 1.417
Enstrom F28 - 1 16 17 --- 845,032 - 0.118 1.893 2.012
MBB BO 105 - 1 12 13 --- 806,750 - 0.124 1.487 1.611
Bell 212 - 1 3 4 --- 497,129 - 0.201 0.603 0.805
Hughes 269 - 5 28 33 --- 1,992,301 - 0.251 1.405 1.656
Bell 47 - 6 44 50 --- 2,343,215 - 0.256 1.878 2.134
Bell 204 - 1 2 3 --- 227,683 - 0.439 0.878 1.318
Robinson R22 - 23 39 62 --- 1,524,483 - 1.509 2.558 4.067

Fatal Accident Totals 43 314 357

1 LOSS of control (LOC) accidents, involved an in flight: loss of main rotor control; structural failure of the main rotor blade that did not involve pre-existing fatigue of rotor blade materials; or, loss of aircraft control or collision with terrain for unknown reasons, in the absence of structural failure, encounter with instrument meteorological conditions, or pilot impairment due to drugs or alcohol. a Accidents involving Fairchild Hiller FH1100 (two fatal LOC accidents) and Brantly B2 (one fatal LOC accident) helicopters were excluded because reliable utilization data were not available. b General Aviation Activity and Avionics Survey, Federal Aviation Administration: Washington, D.C. 1980-1992. Nine missing data values were imputed by linear interpolation. General Aviation and Air Taxi Activity and Avionics Survey, Federal Aviation Administration: Washington, D.C., 1993. Preliminary 1994 data from Federal Aviation Administration, Washington, D.C.

Note: The total flight hours for the Hughes 369 cannot be right, even though what is shown is as the report reads.

(Edited to clean up the table's appearance)

[ 15 December 2001: Message edited by: Flight Safety ]

[Lu Zuckerman]

To: 3top

“ About the droop stops Lu is complaining on the Robbie. Well they are fixed, so what, so are the ones on any other helicopter once the machine is running. I understand that most models use moveable stops (personally I know only the systems on B-47 and 206) to limit movement on the stopped or very slow rotor on run-up or shutdown. Maybe it slipped Lu that the Robbies use FRICTION in their heads and quite a bit (AND it works beautifully!), so when the rotor is slow or stopped the blades hardly flap at all. Once very slow or stopped they seat on stops to avoid too much droop in the CONING HINGES. So you would have to move the rotor by hand to move the head all the way to the flap stops”.

What you say about the Bell and Robinson droop stops is correct with one exception. The last two words in your paragraph above should read "teeter stops" as opposed to "flap stops". The point I was making was that with the fixed droop stops on the Robinson the blades could contact the stops during high flapping excursions. And, in doing so, the kinetic energy will turn the rotor system into a first class lever with the fulcrum at the teeter hinge and force the entire head down making contact with the mast. This flapping is very intense and occurs at a high frequency, which literally beats the head into the mast at a high rate causing mast separation. This in effect would turn that part of the Robinson head into one half of a Bell blade and head.

On other helicopters that are equipped with flapping capability they employ centrifugally operated or other devices such as used on the Hughes design that maintains the static droop angle but permits the blades to flap lower than the static angle during flight. Many of these helicopters also have limiting stops, which limit the maximum up and down flap of the blades. When the blades hit either of these stops during maneuvering the pilot will feel a heavy beat and then he will limit his cyclic input. The Robinson can not flap below the static droop limit of the blade.

Regarding the strength of the components on the crashed R-44 as demonstrated by what bent and what broke as the result of the crash the loads are distributed in a different manner in a crash. In the case of a mast separation the loads are repetitive and they are applied in a very concentrated area. Although the mast and head were not visibly or overly damaged as a result of the crash mast bumping would have been a different story.

[ 15 December 2001: Message edited by: Lu Zuckerman ]

[rotorfossil]

Seeing all the posts on R22's prompts me to add my experiences. The commercial school that I was involved with established the principle that simulated engine failures would be demonstrated and regularly practiced to EOl's from all stages of flight. That is, hover, low transition up to 30kt, full power climb at 60kt/200ft, final approach to hover/200ft and level flight 50ft/60 - 70kt. Also demos and practices of low 'G' recoveries wre done until Robinson's ban on this demo.

Low transition - level the skids, pause, raise the lever as per hover. Once initiating the climb, then you can lower the lever, level the skids and cushion the touchdown.

In the climb 60kt/full power - SLAM THE LEVER DOWN (you cannot do it too quickly) and don't try to change the attitude while you are doing it. Unless you are very quick indeed (about half a second), the RRPM will decay below 90%. Even from 200 ft, full autorotation will not be established and a full flare only reduces the speed, not the R of D. Better to accept a gentle flare and run on. If on entry , the speed has decayed below 45kt, don't try to increase it, just accept the constant attitude technique.

On the approach, speed below 60kt, again GET THE LEVER DOWN. The RRPM decay is less marked due to the lower lever position. Again, a full flare to a low speed touchdown doesn't work, Gentle flare if above 50 kt, constant attitude if less.

In both the above, the lever has to be used in one quick application, as the RRPM is unlikely to have recovered to the normal figure.

In the 50ft/ high speed case (like when practising quickstops), you must start the flare first AND THEN LOWER THE LEVER. Vary the flare to maintain a descent and again accept a run-on EOL. This is the one occasion when lowering the lever first is the wrong move. You cannot get rid of the descent before the ground comes up.

Re 'Low G' situations. These were practised from a slightly nose high situation. It didn't take much of a pushover, and by the time the nose was just below the horizon, the roll to the right started and positive rearward cyclic was needed to counter it as per Pobinson POH advice. The situation that bothered me, was early students practising "effects of controls" and lowering the nose too quickly, which many did. Hence an early demo of why this wasn't a good idea!

Incidentally, after seeing the problem on the R22, I found that the same situation could be demonstrated on the Bell 47 and the Bell 206, it just happens slower.

I firmly believe that more attention should be given in training to getting into auto rotation quickly, rather than the EOL. Unless skill is maintained in EOL's by constant practice, the chances of pulling off a successful one in real situations is low. However, if you get into autorotation and don't do anything else, the chances of walking away from the wreck are pretty good.

It is my experience of doing checkrides in R22's, that in spite of being carefully briefed that at sometime in the sortie, the throttle would be closed without warning, few lowered the lever quickly enough and some not at all, even in the cruise. This is all about mindset unfortunately: "It is never going to happen to me". Unless you have the thought in your mind that if it all goes a bit quiet, what do I do first, then any problem such as carb icing, (which I don't think has been completely solved by the carb heat assist), or partial or complete engine failure is likely to result in the "low RRPM, rotor blowback, chop tail off scenario.

To finish off this ramble, perhaps I should mention that I have been involved in three real helicopter engine failures (not Robinsons) with qualified pilots flying them, and none of them lowered the lever until prompted - forcefully.

[Vfrpilotpb]

Rotorfossil,
Good morning, would be kind enough to just expand a little on the full power climb situation, this is the one area that I have most wanted to try out, but my Cfi says that it is not allowed because of the possibility of bending metal, I practise Autos about every 4/6 weeks and feel very happy about what to do, but its that area of initial climb out at full power that seems to elude my experiance, are you saying that the RRPM will decrease to 90% in less than .5 secs at the onset of failure or, that you must in this instance get he lever down in less than .5sec's, and then level up, to skids level, or to stay at the inclined attitude and level gradually as you steady yourself for the run on?
My regards

[rotorfossil]

Vfrpilotpb from rotorfossil

Hi.

When it all goes quiet, or the nasty guy in the other seat closes the throttle, you have about half a second to get the lever down. the RRPM will normally drop to 90%. any hesitation at all and they will go lower. THIS IS MOT GOOD NEWS although 87% is recoverable but definitely not recommended.

The reason for not trying to change the attitude during the entry is that the 'G' is very low for a short while until auto is established. The possibility of mast bumping exists therefore if large control inputs were made. If after you have succesfully got into auto and the IAS has reduced below 50 kt, trying to get the speed back from a 200ft entry just results in a higher rate of descent with no attendant benefit. I can understand your CFI's reluctance to demonstrate if he has not been introduced to the techniques, the potential for error is considerable, and for training purposes, entries should not be contemplated below 200ft. If you haven't been shown a simulated engine failure from a full power climb/60kt at a safe height(say 1500ft), this might be a suggestion to him. Watch and remember the rapid RRPM decay.

[Dave Jackson]

It appears that Frank Robinson may have borrowed his rotor head concept, of twin hinges and delta-3, from the Weir W-6.

To keep Lu motivated , the attached web page is provocatively submitted. http://www.UniCopter.com/temporary/weir.html

Trivia:

The test pilot of this craft, Mr Raymond Pullin, was the first Englishman to have his pilot's license endorsed for helicopter flying.

[ 16 December 2001: Message edited by: Dave Jackson ]