R66 crash in Wikieup, Arizona, U.S.A., kills 2

[Hot and Hi]

Helicopter crash in Wikieup kills 2 | 12NEWS.com (http://www.12news.com/news/local/arizona/helicopter-crash-in-wikieup-kills-2/255202109)

Police release believed identities of helicopter crash victims | 12NEWS.com (http://www.12news.com/news/local/arizona/police-release-believed-identities-of-helicopter-crash-victims/259652882)

The Robinson R66 helicopter crashed Thursday afternoon (23 June 2016) while flying from Prescott to Riverside, California. Search crews found the wreckage of the helicopter early Friday morning. Authorities said the helicopter burned after crashing.

Here is a picture of the crash site; it looks like the Mohave Desert:

2 dead after helicopter crash near Wikieup - azfamily.com 3TV | Phoenix Breaking News, Weather, Sport (http://www.azfamily.com/story/32300772/2-dead-after-helicopter-crash-near-wikieup)

Time of crash is reported "afternoon". The flight was reported overdue on Friday 12:22 am only. It is not clear whether it crashed during legal daylight still, or at night.

[nocarsgo]

https://m.facebook.com/story.php?story_fbid=1725761437640652&substory_index=0&id=1694600284090101

Looks like some of the upper guys at Guidance. Sad to see this.

[givdrvr]

Very tragic RIP . Unsubstantiated chatter on another internet forum indicated early thoughts were of mast bumping. In any case, from the NTSB preliminary report:

The helicopter came to rest in hilly desert terrain. The debris field was about 750 yards long and 150 yards wide. One of the first pieces identified was the outboard 5 feet of a main rotor blade afterbody that had separated from the leading edge spar. The left side of the helicopter was more fragmented than the right, and left side cabin pieces and instruments were distributed throughout the early part of the debris field. The tail boom was about midway into the debris field. The left side/nose cabin was in the same approximate part of the debris field with a straight separation line across one side. The cabin came to rest inverted about 600 yards into the debris field, and was destroyed by a postcrash fire. The engine remained attached to the cabin. The remaining piece of main rotor blade was about the same distance into the debris field, but 85 yards left of the debris path centerline. The transmission, mast, and second main rotor blade separated as a unit, and were about 100 yards past the cabin area in the direction of the centerline of the debris field.

[Gordy]

Word on the street is to watch for a change of VNE.

[henra]

Very tragic RIP . Unsubstantiated chatter on another internet forum indicated early thoughts were of mast bumping. In any case, from the NTSB preliminary report:

Well, after that sobering description of the wreckage path/distribution there is realistically very little doubt that it is another tragic case of Mast Bumping.

[[email protected]]

But Robinson won't move away from their MR head design, despite how susceptible it is to this phenomenon.:ugh:

[vaqueroaero]

How does one gather mast bumping from that? It seems that another possibility would be a blade failure. It wouldn't be the first time that's happened in a Robinson product.

Tim Brown was a highly experienced pilot, a master of the utility world. He spent many hours sock pulling in the wire environment. That he died in straight and level flight is a cruel end to a highly accomplished career.

[Luther Sebastian]

Crab, Bell haven't moved from their 206 head design either.

[Reely340]

Crab, Bell haven't moved from their 206 head design either.
True. That design is why another one died recently on IOM, apparently from turbulence induced mast bumping. And that design will contiue to kill people in the 505.

They may be a lot to be said in favour of twin bladed tethering Bells, from space savings in the hangar, over cool blade sound till great Bell customer service. But tethering rotor heads are stupid, dangerous, early ages designs. It should not be possible to get a new aircraft design certified using them.

[Hot and Hi]

That he died in straight and level flight is a cruel end to a highly accomplished career.
I agree. However straight and level at VNE can turn in a blink into exceedance of VNE. What do we actually know? Does anybody know the time of departure, estimated time of accident, t/o weight, and weather en-route?

[claudia]

Very tragic indeed and sad that people are still buying and flying these things.
Reely, agree with your theory on teetering heads but no one in authority is
listening. For some, price seems more important than safety.

[Bell_ringer]

A great many hours have been flown safely on semi-rigid rotor systems.
Recently, people seem to hit problems at speed in turbulent conditions. This would appear to be more of a problem with education than the architecture of the machine.

[claudia]

Yea Yea, Robinson offer this rather pathetic explanation / excuse also, but please
remember these were two very experienced guys. If it could happen to them it could happen
to most of us. --very very tragic indeed.
Surely a major re- design to that head and blade system is badly overdue. Please somebody
in authority take action before further unnecessary loss of life.

[AnFI]

claudia
i think that applies to twin engine given how dangerous they are
you can strike your boom in anything if you try hard enough

[Lala Steady]

claudia
i think that applies to twin engine given how dangerous they are
you can strike your boom in anything if you try hard enough More trolling irrelevance AnFi?

Which other manufacturer has to run safety courses for its products because they kill so many unsuspecting pilots??

[krypton_john]

All helicopters kill their unsuspecting pilots if the unsuspecting pilots don't follow their training.

[FLY 7]

But some seem to catch out even the very best pilots.

[krypton_john]

Some or most?

[[email protected]]

Some or most? Just the one seems to have the monopoly sadly. A design that can catch out the unwary newcomer is one thing but one that consistently takes out very experienced pilots as well is just a poor design.

Whilst all teetering head helos can be susceptible to mast bumping - few can get it badly enough to cut off the tail boom or skids with the frequency of that particular manufacturer.

[Lonewolf_50]

Whilst all teetering head helos can be susceptible to mast bumping - few can get it badly enough to cut off the tail boom or skids with the frequency of that particular manufacturer. Crab, I've never flown a Robinson. Would a vigorous "push over" (using substantial /rapid forward cyclic) be enough to unload the head and cause the kind of problem you are referring to there?

[GoodGrief]

... few can get it badly enough to cut off the tail boom or skids with the frequency of that particular manufacturer.Oh, well.

https://sites.google.com/site/mthompsondc/star-telegramseries

[[email protected]]

Goodgrief - experiencing mast bumping due to aggressive handling when NOE (which was the main problem in the US military) is not the same as just encountering turbulence or slightly exceeding VNE in a robbie.

Lonewolf - you don't need a vigorous push over to experience it - any unloading of the G, even an entry to auto without aft cyclic to load the disc - can cause it.

As G is reduced, the only thing producing thrust relative to the airframe is the TR which produces yaw and roll that, if there is any untoward movement of the cyclic, will usually cause the MR to chop off the tail. In extreme cases the strain can demolish the pitch change arms as well resulting in even more extreme rotor strikes (like the front of the skids in one fairly recent crash)

[Lonewolf_50]

@GoodGrief: in the 32 years since the article you cited came out, the semi rigid, underslung, teetering rotorhead on the Jet Ranger has not caused a rash of deaths due to mast bumping. (That design is similar to that of the Huey). The Navy's still flying them at Whiting field (though there have seen better days).

Plenty of two bladed Hueys and Cobras were operated safely and effectively for the 30+ years since the falling firmament articles linked. Heck, they are still being flown, the Air Force with a TH version, even though the Marines are replacing them nowadays with the newer, 4-bladed UH-1Y (Venom) and AH-1Z (Viper) that use bearing-less rotors.

I realize that this thread is about Robinsons, but just thought that I'd report to you that the sky hasn't fallen even though some helicopters now and again fall out of the sky. (Not to mention all of the 212's that have been successfully operating the world over ... )


Some flying basics usually help us operate our aircraft within limits:
You don't pull nine G's in a Cessna
You don't unload the head on a Huey.

[henra]

@GoodGrief: in the 32 years since the article you cited came out, the semi rigid, underslung, teetering rotorhead on the Jet Ranger has not caused a rash of deaths due to mast bumping. (That design is similar to that of the Huey). The Navy's still flying them at Whiting field (though there have seen better days).



I guess it has got a lot to do with sensitivity of the controls, Rotor inertia and margins.
All these seem to be much more benign in the Bells than in the Robbies. Flying into light/moderate turbulence at 80% vne probably won't let you arrive vertically and nose down without the big fan on top in the Bells. In the Robbies I wouldn't bet my Life on that.

[lelebebbel]

I'm not a test pilot or anything, but I have a decent amount of time in 206s and R44s. I only flew an R66 once, two on board full fuel. It immediately occurred to me that it felt very very light, as if the disc was barely loaded, and I made a comment to the owner (who was the passenger) about it.

It reminded me of a lightly loaded R44 with one on board, quarter tanks. And I had gotten into a low G event, with the whole 90 degree right roll and everything, a few years prior in one of those. I had flown it into a mountain wake in Tasmania after dropping some hikers off in the hills.
The difference is of course that the R66 has another 15 or 20kts on such an R44, which makes it scarier to me. A Jet Ranger, at least going by feel, is nothing like it at all.

Just my 2 cents.

[Lonewolf_50]

And I had gotten into a low G event, with the whole 90 degree right roll and everything, a few years prior in one of those. I had flown it into a mountain wake in Tasmania after dropping some hikers off in the hills. In an event like that, is the correct response to load the head using collective before using cyclic to maneuver/roll? Never flown a Robinson, so I have no idea.

[[email protected]]

Yes, until you get the rotor pulling the fuselage with positive G, you have little or no control power and are therefore unable to alter the fuselage attitude - so moving the cyclic first will often make things worse.

[AnFI]

WARNING CRAB

10 hours of flying one before you crashed it and now you don't like it.

and now you are giving advice and the benefit of your suspect PoF on it

you are becoming a danger

[[email protected]]

AnFI - 13 hours actually:ok: I was taught to fly it by a very experienced mil instructor with thousands of hours R22 as well - all the safety issues were well known and discussed at length.

A year or so after I last flew a robbie (early 1990s), the most experienced R22 instructor in the UK (circa 8000 hrs on type IIRC) was killed in one due to a low G event and a MR strike on the tail - surmised to have been caused by a FW pilot entering auto by dumping the lever and pushing the nose forward!

Has anything I have said been untrue with regard to the PoF for mastbumping/ rotor strikes on the R22?

No - avoidance of mast bumping is what is taught on the Robinson safety course - so in trying to question my knowledge, you are encouraging less well-informed pilots to ignore the very real dangers of low G in Robinson helicopters.

[gulliBell]

Regarding post #27. This comes as a surprise to me. I thought a low G recovery technique initial action would be application of aft cyclic. Not that I have ever experienced low G in a 206 or 212, but if I did I suspect my reaction would be aft cyclic.

[Soave_Pilot]

the most experienced R22 instructor in the UK (circa 8000 hrs on type IIRC) was killed in one due to a low G event and a MR strike on the tail - surmised to have been caused by a FW pilot entering auto by dumping the lever and pushing the nose forward!


Are you sure about this? is it on the report?

From my understanding you cannot get into a low g situation (fuselage roll) entering autorotations.

[Lonewolf_50]

Don't want to cause a bun fight. As I see the issue being discussed, the head can be unloaded (or at least partially unloaded) by two distinctly different stimuli:
control movements
external stimuli in the forms of turbulent air / down drafts / (up drafts?).

My question might warrant a two part answer, one for each way that the head got unloaded in the first place, though my initial question was about the turbulence kind.

[LRP]

don't know a thing about R-22's, but in all of the Bell semi-rigid systems the appropriate reaction to a low-G event is aft cyclic.

[[email protected]]

OK, low G is a bit of a variable term ranging from 0.99 G to zero G and the answer to recovery depends on the severity (ie the closer to zero) you are.

At zero G in a teetering head helicopter, you have no control power (ie how much you have to move the cyclic to affect the attitude of the fuselage). You can wave the cyclic around as much as you like but it won't affect the attitude of the fuselage.

At zero G you have no cyclic control power so therefore aft cyclic won't be effective and can make things worse (ie chopping off the tail) - the only thing that will save you is to restore positive G and that would have to be with the collective.

At 0.99 G you have a very small reduction (probably imperceptible) in control power so aft cyclic will immediately (if you have any forward speed) restore normal operation.

There is a big sliding scale between those bookends of performance - the lower the G, the lower the control power and somewhere (I don't know exactly) there will come a point where the control power is sufficiently low to render aft cyclic ineffective in restoring G (and therefore control power).

You don't have a G meter in the cockpit so you can only use seat of the pants to assess any apparent reduction in G. You can feel quite clearly a change from 1.0 to 0.5 G and zero is very floaty indeed.

It seems that Bells cope better with reduced G than Robinsons - it may have a lot to do with rotor inertia, or the extra stability provided by the additional features of the rotor head that aren't on the robbies.

Whatever the reason, any reduction in positive G should be avoided (whether through turbulence, exceeding VNE, poor entry to auto) in a Robbie and zero G should be avoided at all costs in any teetering head helicopter.

Soave pilot - I would have to do a search on the AAIB but that is what I remember (it was about 20 years ago) if you lower the lever quickly and push forward with the cyclic (the sort of reaction a FW pilot converting to RW might have to a stall - I have seen this with FW friends) - you will get a reduction in G - how much depends on the rate of application and displacement of the controls.

If you pull up and then put in the same control inputs, you can easily get to zero G ask any military pilot who has bunted a helo in order to scare the troops in the back.

Lonewolf - if you hit a big updraft in the cruise, the natural reaction is to lower the lever to maintain height - if that updraft has caused the nose to pitch up slightly you may well inadvertently push forward on the cyclic as well.

[krypton_john]

Sorry if this has been posted before...

UH1 and AH1 specific, mainly focused on push-overs as the source of mast bumping.

https://www.youtube.com/watch?v=nm8iV_uiBsI

Couple of interesting points in the context of our discussion - 0.5G as the number to stay above, and recovery is gentle aft cyclic followed by left cyclic once disc is loaded. No mention of collective whatsoever.

IIRC the Robinson standard recovery procedure is the same - immediate but gentle aft cyclic followed by left cyclic once the disc has loaded.

[ascj]

'The transmission, mast, and second main rotor blade separated as a unit'

Your arguing the wrong point. If it was mast bumping the blades would no longer be attached to the transmission, i'd put money on it being a blade failure at the same place we saw on the 44s last year.

[Arrrj]

At the risk of getting involved in yet another Robbie bashing exercise, I make the following comments - as these may help someone.

I flew the first 66 in Australia, within a week of it being in Aus. Obtained one of the first endorsements for it. 5 years ago ? I have flown 3 machines on / off since then.

First thing I noticed, like others, is that when 2 up & low fuel it it feels very light. Rule number one, keep the disk loaded (thanks to many high hour pilots that told me this 10 or so years ago when I started flying helis - about ALL machines).

Second thing, the 66 is really powerful (3/4 fuel, 5 up, confined area, 30 degrees, up, up and away) and fast. 60% torque, 130 knot cruise.

One of my good mates has around 1,000 hours on one now, and we both AGREE - never fly the 66 "light". Fill it up with fuel, people, golf sticks, beer, or whatever else you can find.

Keep that disk loaded, and do not fly it at 130 knots, by yourself, in the mountains.

The 44 is quite different, after all it has that big lump of metal (the motor) in it all the time !

I hope that helps.

Arrrj

PS _ as someone else said, 2 blade helis have flown a "few" hours over the last 40 years or so !

[krypton_john]

Arrrj: "Fill it up with fuel, people, golf sticks, beer, or whatever else you can find."

Women. If you can afford the heli you can afford them too.

[Jelico]

Quote:
In an event like that, is the correct response to load the head using collective before using cyclic to maneuver/roll? Never flown a Robinson, so I have no idea.

Incorrect. That reaction could kill you in a 2 blade system, especially the Robinson products. It seems a lot of people forget that the low G is not what kills you in this situation, its the fuselage rolling independently, underneath an unloaded rotor disc. In my opinion prevention is far better than the cure - i.e. slow down in turb, and or try not to fly too light in bumpy weather. But should you encounter a low G roll, pulling on the collective to load the disc will only make the roll and ensuing mast bump happen quicker and more violently. There are a lot of schools of thought on the best recovery method, but lowering the collective and REDUCING TORQUE which is causing the tail rotor to flip you is generally thought of as part of the correct recovery. In my opinion, loading the disc with aft cyclic and lowering the collective along with a bit of right pedal (think quick stop) is the best recovery technique as it does everything you can do to fix the issues at hand, and also slows you down to a safer airspeed.

In saying all that, I have experienced a roll in an R22 once (out of approx 400+ hrs Robinson time, mostly 44 but sprinkled with 22 and 66 time). It happened so quick that i was at 50-60 degrees before I could think about responding. Luckily my hand stayed still and did not correct the roll and we sort of swung out of it. From that point I decided that I probably dont have quick enough reactions to fix the problem after the roll, so decided that I would just slow down and/or not fly on really windy days in the Robbies.

[AnFI]

Crab this is an absolute disgrace

"Has anything I have said been untrue with regard to the PoF for mastbumping/ rotor strikes on the R22?

No - avoidance of mast bumping is what is taught on the Robinson safety course - so in trying to question my knowledge, you are encouraging less well-informed pilots to ignore the very real dangers of low G in Robinson helicopters. "

You ask the question. The answer is actually YES YOU ARE WRONG
So your own answer of "NO" and the susequent acusation you make is unacceptable. You are a disgrace.

The fact that you have 13hrs on type before crashing it and not 10hrs still does not instill one with much confidence in your advice. The fact that you were taught by an ex mil pilot on it also does not seem to have helped you. That is either a reflection of your teacher or your ability to understand, most likely the latter judging from your inability to understand weather for the VMC pilot, dissymetry of lift and many other basic PoF and other priciples. Perhaps you could join the regulator and really make a (totally useless) difference?

No I am not going to correct you.
Stop your dangerous rambling insulting b****cks and do some research and sort it out for yourself.

[SuperF]

aft cyclic then worry about getting upright.

Crab, be careful telling anyone to play with the collective before the cyclic, you will get them killed.

But yes, prevention is better than the cure, and the best prevention is again aft cyclic, as that will make you slow down...

[Arrrj]

Krypton,

:D

[[email protected]]

aft cyclic then worry about getting upright.

Crab, be careful telling anyone to play with the collective before the cyclic, you will get them killed. As I said, it depends on how little G you have - at zero G aft cyclic will not have an effect other than to move the disc nearer to the tail boom - that will get people killed.

If you have some G (less than 1 but more than zero then aft cyclic may have a beneficial effect)

Please explain how using the collective will get people killed??

AnFI - You ask the question. The answer is actually YES YOU ARE WRONG as ever, a pointless rant - you claim such superiority but never actually explain your point of view - please do correct me if you can = with facts not ranting.

Do you understand the term control power?

[[email protected]]

JellicoeThat reaction could kill you in a 2 blade system, especially the Robinson products. It seems a lot of people forget that the low G is not what kills you in this situation, its the fuselage rolling independently, underneath an unloaded rotor disc. In my opinion prevention is far better than the cure - i.e. slow down in turb, and or try not to fly too light in bumpy weather. But should you encounter a low G roll, pulling on the collective to load the disc will only make the roll and ensuing mast bump happen quicker and more violently. You get the roll because the cyclic is ineffective and the only thing creating thrust relative to the fuselage is the TR. The roll occurs as a secondary function of left yaw (you have power pedal applied in the cruise) - putting in right pedal is effectively the same as applying collective without adding left pedal - it causes right yaw which will tend to oppose the roll.

As you discovered In saying all that, I have experienced a roll in an R22 once (out of approx 400+ hrs Robinson time, mostly 44 but sprinkled with 22 and 66 time). It happened so quick that i was at 50-60 degrees before I could think about responding. Luckily my hand stayed still and did not correct the roll and we sort of swung out of it. From that point I decided that I probably dont have quick enough reactions to fix the problem after the roll, so decided that I would just slow down and/or not fly on really windy days in the Robbies. it happens quickly and if you had added aft cyclic (instead of holding the controls steady) you would very likely have chopped off the tail.

Just how many accident reports of this phenomenon do people have to read before they understand it?

[[email protected]]

https://assets.publishing.service.gov.uk/media/5422f79b40f0b613460006e1/Robinson_R22_Beta__G-PUDD_10-94.pdf
here is the one I referred to earlier

[John Eacott]

There's nothing new: Design flaw mars Bell military helicopters (https://sites.google.com/site/mthompsondc/star-telegramseries)

And only today I was being regaled with war stories of NoE flying in Kiowas :hmm:

[Jelico]

Hi Crab, I try not to post on these forums, especially to give advise but there seems to be some misinformation. My concern was the unnerving posts about people loading the disc with collective, which is undoubtably the wrong thing to do. Increasing the torque that is flipping you will just kill you quicker.

I think you are right in that in a completely unloaded disk i.e. zero G, then you have no control power. Any right, left or aft cyclic wont do anything at that point but I think if you get to that position the horse has pretty much bolted and you are just along for the ride.

[[email protected]]

From Robinson http://www.robinsonheli.com/service_library/safety_notices/rhc_sn29.pdf

and http://www.robinsonheli.com/service_library/safety_notices/rhc_sn11.pdf read this one carefully as first of all it warns against aft cyclic and then says do it very gently - even the manufacturers can't give consistent advice.

If your automatic/trained reaction is to pull aft cyclic, you might well chop off your own tail - straight from the horses mouth - good enough for you AnFi?

[chopjock]

crab,
I can't see anything in those links about adding collective either?

[[email protected]]

Chopjock - no it doesn't but if you can't load the disc with cyclic, what else are you going to use to get the rotor pulling the airframe around again rather than waiting to see if it sorts itself out?

Clearly the worst thing you can do is try to oppose the roll with left cyclic but that will be an automatic reaction for most pilots to an undemanded roll to the right.

The only problem with adding collective is if the Nr has decayed due to the reduction in G (negative flare effect) where more power might further reduce the Nr briefly until normal G is restored.

Which would you rather have - slightly low Nr or a chopped off tail?

As has been said before the answer is prevention since the cures carry their own risks and the Robinson safety notices emphasise keeping well below Vne, especially in turbulence - but how many pilots follow that advice or even think about it before they encounter the updraught?

[chopjock]

no it doesn't but if you can't load the disc with cyclic, what else are you going to use to get the rotor pulling the airframe around again rather than waiting to see if it sorts itself out?

I think we all agree a "little" aft cyclic is required to load the disc. Perhaps a little less pedal too if ac is rolling?

[LRP]

this phenomena was quite pronounced when the AH-1G was fielded in the late 60's due to the maneuvering and high angle/high speed weapons delivery that was used at the time, in fact low-g roll and recovery was a demo maneuver at Cobra Hall until someone discovered how dangerous it was. The corrective action is aft cyclic followed by rolling level. The following is from the AH-1S Operator's Manual (-10)

654

[[email protected]]

Chopjock - unless the nose is pitching down - the SN specifically says ' If the helicopter is still pitching forward when the pilot applies aft cyclic to reload the rotor, the rotor disc may tilt aft relative to the fuselage before it is reloaded.'

As I said earlier, unless you are zero G, you will have some cyclic control but at the lower end of the scale it will seem less effective so judging 'gentle' or 'a little' aft cyclic might be very difficult.

If there is no nose down pitch then gentle aft cyclic should work.

The rapid entry to autorotation is a problem if you push the nose forward - as in the accident I linked to and the other SN - in that case aft cyclic would be disastrous.

Jellicoe - the SN says that aft cyclic would combine MR torque reaction with the TR thrust - the TR thrust is producing left yaw and any application of lever would produce right yaw. It is the reduction in MR Torque caused by flare effect (moving the cyclic aft) that aggravates the yaw and thereby the right rolling motion highlighted in the SN.

[[email protected]]

LRP - whilst all teetering head helos are susceptible to mast bumping, do the Bells exhibit the rather nasty rapid right roll which is the problem with the Robinsons?

[Bell_ringer]

At the risk of getting a bad case of crabs :eek:,
Unless I'm misreading the report, the comments about entering auto-rotation (with student fixed-wing pilots) are specifically about stalling the blades that already have low Nr.
In this instance forward cyclic and pulling collective would prove fatal.
In the context of the report this isn't proven but rather referred to as being similar to another low Nr-related tail strike.

[[email protected]]

Bell ringer - the rotor stall would only occur following a real loss of power, not for a practice autorotation.

FW pilots tend to react to a stall by pushing both hands forward (stick forward and full throttle) which translates to lever down and forward cyclic in a helo - if you do that for a practice autorotation and are even remotely ham-fisted, you can quickly get to a low G, mast bumping scenario.

You can get tail strikes from both low Nr (rotor stall) and low G with associated mast bumping and undemanded roll. FW responses to emergency (or practice emergency) situations can be fatal in both scenarios.

[Hughesy]

Robinsons are like Islam, should be banned!!


regardless of all the banter and sh*t slinging going on. EVERY pilot should have in his or her mind what they will do in a low G situation.
Personally, I always self briefed Aft cyclic. And always had that in my mind. Hold the cyclic still, then gently aft.
how the hell are you supposed to know if your 0.0 deg low g or .99 low G I will never know.
Plan for it guys, same as places to land if the donk stops. Have a plan of what the recovery is.
Plan. That will save your ass.


An addition to this. Neg G will not cause mast bumping. It's the incorrect pilot actions that causes it. Correct actions can and will stop it from happening.
During low G, there is no main rotor thrust occurring. But the tail rotor still produces thrust. The TRT causes the 2 bladed heli to roll to the right which put the flapping of the blades at maximum. The incorrect but natural reaction of the pilot is to correct the right roll with left cyclic. As the flapping is already at maximum it is then exceeded which causes the blade drop stop to contact the mast. In a very lucky situation the mast may only be bent but somehow holding on. More often then not, the mast is damaged enough the main rotor departs.
To reload the disk, aft cyclic. The pilot must be mindful that low g, you will have a light feeling in the seat of your pants. Then the roll. Aft cyclic (although at that point unnatural) is the best way to reload the disk.
Regardless of different procedures. Robinson state ( well the last time I watched that video) was aft cyclic.

Also, just slow the hang down. What's a 10kt reduction in airspeed?


Condolences to the crew.

[LRP]

LRP - whilst all teetering head helos are susceptible to mast bumping, do the Bells exhibit the rather nasty rapid right roll which is the problem with the Robinsons?
Yes it does, the onset is quite rapid and dramatic (with respect to the AH-1 series).

[FLY 7]

The AAIB Report, following the crash of this B206 at last year's Isle of Man TT, makes interesting and sobering reading:

https://assets.publishing.service.gov.uk/media/5739950ee5274a1523000002/Bell_206B_Jet_Ranger_II_G-RAMY_06-16.pdf

A combination of inexperience, strong winds and teetering rotorhead.

[[email protected]]

Hughesy - I think that Hold the cyclic still, then gently aft. and Also, just slow the hang down. What's a 10kt reduction in airspeed? is pretty much the best advice for Robinson drivers.

The second one should help prevent the event in the first place and the second, especially the pause before gently loading the disc is the best 'one-size fits all' recovery strategy.

i didn't want to create a cyclic vs collective argument - simply highlight what is going on in the low G environment so pilots can make their own educated decisions.

Obviously the best decision is not to get in a Robbie in the first place (I have promised my wife not to ever do so again):)

[SuperF]

obviously a little bit lost in translation. When i talk about any control movements, im talking small movements.

so aft cyclic, means a very small check backwards, not pulling full aft as hard as you can. Thats why these conversations are best done face to face, rather than over the interweb.

other than that, i think i could almost agree with whats said here...

[[email protected]]

What would be interesting is to know exactly why the flick roll to the right occurs.

Normally a yaw to the left would produce a roll to the left as a secondary effect.

The only explanation I can offer is that the TR is above the vertical centre of gravity in a robbie - most of the weight (engine, fuel, pax) is below the line of the tail boom/TR.

So, when the TR is pushing to the right (to create left yaw) it is pushing the fuselage in a roll to the right about the vertical C of G. With no cyclic control (very low G) to oppose that movement, the fuselage can only go one way.

This may be worse in the cruise since the TR is even higher due to the nose down and lack of horizontal stabiliser.

Thoughts?

[GeorgeMandes]

Anyone have a link to a US crash, and related FAA/NTSB reports, of a Jet Ranger or Long Ranger, where the cause was thought to be mast bumping?

[Vzlet]

GeorgeM: Perhaps not exactly what you're looking for, but the NTSB special report available at http://www.rotorshop.com/sir9603.pdf (page 12) classifies two of 121 B206 fatal accidents as "LOC" by this definition:

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 preexisting 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.

[gator2]

Crab, I also would like to understand the physics behind the uncommanded snaproll right. They quit teaching 0-g recoveries by the time I got my PPL, and my instructors are vague on the whole subject. Also, if the snaproll right is caused by left pedal that should be neutralized when the MR torque drops to rotational drag only, then why not a neutralized pedal recovery, leave the stick and the lever alone, and wait for gravity to take over? And yes, I fly Robbies out of necessity, not choice, so the answer to these questions is of more than academic interest.

[Vertical Freedom]

over 3,800hrs in a JetBox, (err that has a 2 bladed teetering-head) more than half of those hours in high altitude Mountains, with seriously eXtreme turbulence, very high winds, landing up to 16,200' & never had a negative G or mast bumping issue, never ever :ooh: :D not even close :8 but I wouldn't wanna be up there in a Robo thingy :=

Happy Happy :cool:

[LRP]

as I said before, I don't know squat about the Robinson design. My experience with this phenomena is with the AH-1 series aircraft. The right roll is the result of T/R thrust, and yes, if you unload the tail rotor as you push over you can minimize the roll. The problem with that technique (which was explained to my 20 yr old brain by an aviator who had more time flying than I had alive) is that you are way outside the envelope and potentially millimeters away from main rotor separation (mast bump)as you try to match thrust.

[topradio]

Has anybody survived mast bumping?


When I was training, about 20 years ago, there was a story about a chap who managed to land a 22 after a mast bump and survived. I don't know how true this was.

[SuperF]

crab, you are correct, roll to the right is from the high TR position. now think UH1's it is even worse than a robbie.... but we have a little more weight to start with.

this is another reason for slight aft cyclic BEFORE you start bouncing through those hills. as you slow down, you end up with less nose down, therefore the TR also comes down, compared to MR level, and can produce less of a turning moment on the fuselage when you start to get bounced, if the bounce even produces a loss of G, or because you already have the disk well loaded you may just get a bounce.

worst combination is 1 up, low on gas, returning to base at VNE, in the lee of some big hills on a windy day, and how many of us have done that? luckily the ol JR doesn't really want to get to VNE straight and Level...

[whoknows idont]

Has anybody survived mast bumping?


When I was training, about 20 years ago, there was a story about a chap who managed to land a 22 after a mast bump and survived. I don't know how true this was.

From the link (https://sites.google.com/site/mthompsondc/star-telegramseries) GoodGrief posted:

Bell and many military officials have insisted that mast bumping will never occur unless a critical part fails or the pilot flies beyond the limits set for the helicopter. But the only person to survive a catastrophic mast bumping disputes their contention.

Col. Larry B. Higgins has told his superiors — and the Star-Telegram — that he was flying a Cobra helicopter within its operating limits last August when a rotor blade sliced through the cockpit, killing his co-pilot instantly. Higgins was able to parachute to safety only because the blade cut off the front of the cockpit, giving him an instant escape route.
Some occupants are not killed instantly, however.

A Marine Corps major was aboard a helicopter at the test pilot school in 1980 when a mast bumping and separation killed his pilot but left him alive. Equipped with a parachute, he pulled his door handle in an effort to bail out, but was unable to open the door. Finally, he broke the handle.

But by the time he was outside the helicopter and had pulled his ripcord, he had hit the ground. An instant later, the helicopter fell on him, according to the Navy investigation.

In a 1981 Australian crash for which Bell is being sued, the Australian military tried to determine why a helicopter crew chief was unable to parachute to safety.

Investigators suggested that he may still have been shaken because of a troubling flight in the same helicopter the week before. He may have frozen in shock when -- after the mast bumping occurred -- the rotor blade came through the cockpit and decapitated the pilot sitting in front of him.

"In this accident, the visual scenes confronting him would have been horrific," the investigators said, noting the crew chief had up to 12 seconds to escape. "This, coupled with (his) already high state of anxiety, may well have been sufficient to freeze him in a state of immobile terror."
:(
This was the first time I read about helicopter air crew being equipped with parachutes btw. Maybe not the worst idea when one has to fly a robinson...

[Jelico]

Has anybody survived mast bumping?

I know of two cases in NZ. In both cases the mast was bumped but not detached completely. I think there may be a Vector (local CAA magazine) article on the second instance which happened last year - will see if i can find and post it. Both mishaps were in R22's. I saw the machine after the second incident and it gave me shivers. Both blades were almost touching the ground as the droop stops were mangled. One blade also creased. Luckily the pilot went with the roll and actually fully barrel rolled the 22 at about 3-400' AGL from memory before getting it under control and landing. Very lucky to be alive, and the only guy I know of to do inverted aeros in a robbie!

[Hot and Hi]

over 3,800hrs in a JetBox, (err that has a 2 bladed teetering-head) more than half of those hours in high altitude Mountains, with seriously eXtreme turbulence, very high winds, landing up to 16,200' & never had a negative G or mast bumping issue, never ever :ooh: :D not even close :8 but I wouldn't wanna be up there in a Robo thingy :=

Happy Happy :cool:
And then there seem to be even 6-bladed helicopters that are very susceptible to tail boom strikes under low G conditions...

[Paul Cantrell]

Sorry, haven't been reading in a couple weeks so I had a bit of catching up to do. I hope you'll bear with this long posting. Having been a CFI before/during/after the entire SFAR 73 debacle I think I have a few good things to add to the discussion.

[email protected]: What would be interesting is to know exactly why the flick roll to the right occurs.
The only explanation I can offer is that the TR is above the vertical centre of gravity in a robbie - most of the weight (engine, fuel, pax) is below the line of the tail boom/TR.

This is correct. When I first did the safety course in the mid 80-s Frank still taught some of it himself. He mentioned that R22 TR thrust could produce roll rates in excess of 100° per second, quote "faster than an F16 can roll".

Lonewolf_50 asked: In an event like that, is the correct response to load the head using collective before using cyclic to maneuver/roll? Never flown a Robinson, so I have no idea.

Robinson (and the Army's training video that was included as part of the SFAR-73 training) recommend gentle aft cyclic to regain gee forces, and then once gee forces are restored you can roll level. They have never advocated addition of collective pitch and I've never tried that - I've always used aft cyclic as recommended. It's worked so far.

[email protected] says: At zero G in a teetering head helicopter, you have no control power (ie how much you have to move the cyclic to affect the attitude of the fuselage). You can wave the cyclic around as much as you like but it won't affect the attitude of the fuselage.

At zero G you have no cyclic control power so therefore aft cyclic won't be effective and can make things worse (ie chopping off the tail) - the only thing that will save you is to restore positive G and that would have to be with the collective.

At 0.99 G you have a very small reduction (probably imperceptible) in control power so aft cyclic will immediately (if you have any forward speed) restore normal operation.

There is a big sliding scale between those bookends of performance - the lower the G, the lower the control power and somewhere (I don't know exactly) there will come a point where the control power is sufficiently low to render aft cyclic ineffective in restoring G (and therefore control power).

I'm not 100% certain, but I think this is likely incorrect. I don't disagree that at very low gee the fuselage will not respond because of the low thrust, but you are still in command of the rotor. Aft cyclic will load the rotor, and as it loads back up gee force will increase and you'll be back in command of the fuselage once again. My experience as an instructor teaching low gee right rolls for almost a decade before the FAA finally put a stop to it is that in a normal demonstration of a cyclic pushover resulting in a right roll, we would push until we would get a right rolling motion and then we would command aft cyclic. I never remember there being any delay, i.e. the aircraft would respond immediately to aft cyclic with gee force increasing. I suspect we were not very low gee but I have no way of knowing what percent of gee we would get the roll at.

I did have an experience with a student in an R22 where at the entry of autorotation he pushed the cyclic to the forward stop as hard as he could, i.e. it was a very quick application of full forward cyclic, along with the normal lowering of collective and application of right pedal. We ended up pretty close to 90° nose low (I know because we were above the end of the runway and the numbers of the runway were straight ahead in the windshield). Again, no way to know how low gee we actually achieved, but my guess would be pretty darn close to 0 gee.

I applied gentle aft cyclic and after what seemed like an extended time, the gee forces built up and the nose finally came up. The thing is, I'm not really sure that it was an extended time, it's very possible that the adrenaline and time dilation just made it seem like a long time. Certainly it worked fast enough that from 500 feet and 90° nose low, we avoided hitting the earth!

After we landed I spent some time thinking about why we were not dead and it occurred to me that it was because we pushed right pedal as we lowered the collective, i.e. there was no TR thrust to roll us (and indeed, there was no roll, just a violent nose pitch down). This is a long way of saying that even at extremely low gee the cyclic will in fact be effective. Whether the collective would work as you mention, I simply don't know.

Arrrj says: Second thing, the 66 is really powerful (3/4 fuel, 5 up, confined area, 30 degrees, up, up and away) and fast. 60% torque, 130 knot cruise.


This is an important point I believe. If you think about the arc you need to fly in order to reach 0.5 gee, it's dependent on speed. In an R22 it takes a pretty good push before you get the right roll, but R22s cruise at 85-90 knots. In an R44 doing 110 knots it takes a gentle application of forward stick to start feeling yourself get light in the seat. In an R66 at 130 knots, it would be even less of a push. So, the faster the aircraft you are flying, the easier it is to push enough forward cyclic to get low gee rolls. It's something I worry about soloing an R44 student versus an R22 student. In turbulence it pays to fly a little slow.

[email protected] says: As I said, it depends on how little G you have - at zero G aft cyclic will not have an effect other than to move the disc nearer to the tail boom - that will get people killed.

Please explain how using the collective will get people killed??


Again, I don't agree with you that at zero gee aft cyclic won't work. Perhaps it will take a little longer to work than at 0.5 gee, I'm not sure. As to whether collective would help or hurt, I don't know but my concern would be that adding power and adding pedal will just increase TR thrust and probably keep things at least as bad as they are, and that adding power and not adding pedal would put you out of trim and the resulting tuck probably isn't going to be helping the head->mast clearance situation. I'll be curious to have one of the test pilots comment on that.

[email protected] says: As has been said before the answer is prevention...

This I very much agree with. I always train people that the first time you find yourself in a low gee right roll, you are very likely going to do the instinctive thing and push the cyclic to the left. Better is to associate the light feeling in the seat of your pants with the need to move the stick aft, i.e. load the rotor back up long before you get to a gee factor low enough to allow the right roll to develop. And also what everybody says: slow down.

Hughesy says: An addition to this. Neg G will not cause mast bumping. It's the incorrect pilot actions that causes it.

I don't think this is correct. I think that the TR alone will cause the mast to be bumped, pushing left cyclic probably just makes it happen more quickly. If Frank is right that the TR can cause roll rates of 100° per second, it won't take long to roll past the 12° of flapping clearance in the robby.

topradio asks: Has anybody survived mast bumping?

When I was training, about 20 years ago, there was a story about a chap who managed to land a 22 after a mast bump and survived. I don't know how true this was.

I seem to remember that a couple guys were out in an R22 Mariner (fixed float) when they did a practice autorotation at VNE and did a complete 360° tail-over-nose flip, i.e. Red Bull kinda move and that they bumped the mast but landed okay (and the VNE was then reduced to 95 knots).

Sorry for the long post, but obviously an interesting discussion for many of us. And, as to the design of the rotor... I've wondered for a long time why someone doesn't make a hingeless 2 bladed system? I like the idea of no low-gee restrictions but still being able to tuck a bunch of aircraft in a hanger skid-to-skid... (and I feel like the slow response of the fuselage in a 2 bladed system like the Robby or Bell makes it more difficult to teach hovering to a new student compared to an articulated system with some hinge offset).

[[email protected]]

Paul - a very informed and interesting post - you have clearly been there, seen that and got the T shirt as far as Robbie flying is concerned:ok:

The quoted rate of roll from the TR thrust is rather sobering - and that was from the bloke who designed it - wonder if he ever thought there was a better way?

I still believe that at zero G in a teetering head helo, you can wave the cyclic as much as you like but, whilst you are changing the disc attitude, the rotor has no effect on the fuselage attitude until some positive G is restored - in the case of your 90 nose down, the fact that you started to accelerate towards the ground restored the G which allowed your aft cyclic to take effect.

The rotor head has to pull the fuselage around the sky on a teetering head helo which requires the weight of the fuselage to be pulling down on the rotor - this can't happen at zero G.

I may be wrong about my suggestion to use collective but it makes sense from the physics.

[Paul Cantrell]

[email protected]: I still believe that at zero G in a teetering head helo, you can wave the cyclic as much as you like but, whilst you are changing the disc attitude, the rotor has no effect on the fuselage attitude until some positive G is restored

Nope, nope, we're in violent agreement on this point, I agree with this totally. :-)

[Lonewolf_50]

I may be wrong about my suggestion to use collective but it makes sense from the physics.
I make the assumption that anytime one adds collective one adds left pedal, (almost as a conditioned response).
Might that tend to mitigate the right roll associated with this hazard? Interesting theoretical point ... but ... it looks as though the less complicated approach is the gentle aft cyclic to load the head. Getting the control of the aircraft back probably benefits from KISS principle, per the experienced Robbie flyers (and thanks Paul for sharing your experiences as CFI)


The other point to take away "in turbulent air, slow down" is good advice.

[LRP]

I make the assumption that anytime one adds collective one adds left pedal, (almost as a conditioned response).
Might that tend to mitigate the right roll associated with this hazard? Interesting theoretical point ... but ... it looks as though the less complicated approach is the gentle aft cyclic to load the head. Getting the control of the aircraft back probably benefits from KISS principle, per the experienced Robbie flyers (and thanks Paul for sharing your experiences as CFI)


The other point to take away "in turbulent air, slow down" is good advice.
Left pedal will accelerate the right roll. It is T/R thrust that is causing the roll.

[Lonewolf_50]

Left pedal will accelerate the right roll. It is T/R thrust that is causing the roll. Hmm, got out my little model, TR above cg ... yeah, got it.

[gator2]

Thank you Paul for the comments based on experience. I had a conversation with my FAA flight examiner on this topic last week. His assertion was that low G from turbulence was an entirely different animal compared to low G from a pushover. This due to relative wind past rotor in pushover vs relative wind up through rotor in turbulence. I'm not buying his explanation, but he's got 10,000 hrs flying Robbie's in the mountains here so I am not going to argue with him. Do you agree with him?


Also, I can not figure out why the correct and quicker response to the right roll is not right pedal along with the collective easy back? Your experience with the R22 student who pushed over with pedals neutral would seem to support that neutralizing the pedals did away with the roll.

[LRP]

Thank you Paul for the comments based on experience. I had a conversation with my FAA flight examiner on this topic last week. His assertion was that low G from turbulence was an entirely different animal compared to low G from a pushover. This due to relative wind past rotor in pushover vs relative wind up through rotor in turbulence. I'm not buying his explanation, but he's got 10,000 hrs flying Robbie's in the mountains here so I am not going to argue with him. Do you agree with him?


Also, I can not figure out why the correct and quicker response to the right roll is not right pedal along with the collective easy back? Your experience with the R22 student who pushed over with pedals neutral would seem to support that neutralizing the pedals did away with the roll.
Jamming right pedal will unload the T/R, no doubt, but you need to be right the first time. How much do you put in? Trial and error isn't an option, and practice could be dangerous.

Aft cyclic is the safest/most practical and proven recovery technique.

[gator2]

Didn't suggest "jamming" right pedal. Didn't suggest right pedal in lieu of easy back on cyclic.


Still want to know: Why not right pedal (to about where it goes when I enter auto, I've got a lot of practice at that) as I go easy back on cyclic?


Also, if I was way out of trim right and pushed over, would the machine snap roll left?


Also, I don't buy the CG thing causing the roll. I think center of pressure of drag on body when crabbed to relative air is far below center of thrust from TR and this is what causes roll. For CG to be a factor, there must be acceleration. Not much of that if you push over while slowing at the top of a climb, and yet she'll snap if you do that.

[LRP]

Didn't suggest "jamming" right pedal. Didn't suggest right pedal in lieu of easy back on cyclic.


Still want to know: Why not right pedal (to about where it goes when I enter auto, I've got a lot of practice at that) as I go easy back on cyclic?


Also, if I was way out of trim right and pushed over, would the machine snap roll left?


Also, I don't buy the CG thing causing the roll. I think center of pressure of drag on body when crabbed to relative air is far below center of thrust from TR and this is what causes roll. For CG to be a factor, there must be acceleration. Not much of that if you push over while slowing at the top of a climb, and yet she'll snap if you do that.
Poor choice of words, "jamming" was mine not yours.

I have some experience with this phenomena in Bell semi-rigid systems, aft cyclic while minimizing all other control inputs proved to have the highest survival rate. From the M/R separations that I am familiar it appears that there is very little time to react.

That's my two-cents, PM me if you want to talk about the aerodynamics, otherwise stay safe.

[krypton_john]

So once a roll starts it's too late?

The reaction time is when you are feeling light... but I have no idea how long that lasts before the roll starts and I don't want to find out!

[[email protected]]

For CG to be a factor, there must be acceleration. Not much of that if you push over while slowing at the top of a climb, and yet she'll snap if you do that. Gator - the acceleration is provided by the thrust from the TR acting about the vertical C of G of the fuselage.

The mechanism causing the lack of positive G might be different between a pushover and an updraught (turbulence) but the result is exactly the same.

We keep coming back to the fact that prevention is far better than cure so don't fly fast in turbulence and don't do pushovers:ok:

[Hot and Hi]

http://www.ntsb.gov/_layouts/ntsb.aviation/GeneratePDF.aspx?id=WPR16FA130&rpt=p
On June 23, 2016, about 1420 mountain standard time, a Robinson R66, N117TW, collided with terrain
under unknown circumstances near Wikieup, Arizona. Guidance Aviation was operating the helicopter
under the provisions of Title 14 Code of Federal Regulations (CFR) Part 91. The commercial pilot and
the commercial pilot rated passenger sustained fatal injuries. The helicopter was destroyed during the
accident sequence, and the cabin area was consumed by a post impact fire. The cross-country
positioning flight departed Prescott, Arizona, about 1340 with a planned destination of Riverside,
California. Visual meteorological conditions prevailed, and no flight plan had been filed.

The pilot was going to Riverside to take a Part 135 chief pilot check ride with an inspector from the
Federal Aviation Administration (FAA) Flight Standards District Office located there. The pilot rated
passenger was the operator's Part 141 Chief Pilot.

[...]

The helicopter came to rest in hilly desert terrain. The debris field was about 750 yards long and 150 yards wide.
One of the first pieces identified was the outboard 5 feet of a main rotor blade afterbody that had
separated from the leading edge spar. The left side of the helicopter was more fragmented than the
right, and left side cabin pieces and instruments were distributed throughout the early part of the
debris field. The tail boom was about midway into the debris field. The left side/nose cabin was in
the same approximate part of the debris field with a straight separation line across one side. The
cabin came to rest inverted about 600 yards into the debris field, and was destroyed by a postcrash
fire. The engine remained attached to the cabin. The remaining piece of main rotor blade was about the
same distance into the debris field, but 85 yards left of the debris path centerline. The
transmission, mast, and second main rotor blade separated as a unit, and were about 100 yards past the
cabin area in the direction of the centerline of the debris field. The main rotor driveshaft was bent
approximately 15 degrees at the swashplate.

[Soave_Pilot]

Looks like another Mast Bumping accident scene...:{

[MitchStick]

https://app.ntsb.gov/pdfgenerator/ReportGeneratorFile.ashx?EventID=20160624X83720&AKey=1&RType=Factual&IType=FA

A "factual report" was published in October that, even if not final, seems to confirm Mast Bumping as cause.

Personally I'm somehow "relieved" for the fact that was a sadly well known cause and not some new design flaw that caused the crash..

[Ascend Charlie]

Just read back a few pages and found this bit:
In a 1981 Australian crash for which Bell is being sued, the Australian military tried to determine why a helicopter crew chief was unable to parachute to safety.

Investigators suggested that he may still have been shaken because of a troubling flight in the same helicopter the week before. He may have frozen in shock when -- after the mast bumping occurred -- the rotor blade came through the cockpit and decapitated the pilot sitting in front of him.

"In this accident, the visual scenes confronting him would have been horrific," the investigators said, noting the crew chief had up to 12 seconds to escape. "This, coupled with (his) already high state of anxiety, may well have been sufficient to freeze him in a state of immobile terror."

First I have heard of this finding, and it was an incident I was intimately involved with - it was my UH-1B, but a qualified test pilot was flying it, to try to find why it had nosed over in flight a week before, when the other pilot was flying it. All on board wearing parachutes for the test. The aircraft had been through 2 major servicings after the incident but no cause was found.

On this tragic day, though, a control cable for the T/R, (which in the B model is routed beside the drive shaft) came off its pulley and contacted the drive shaft, and got caught up and wrapped around it. T/R taken to an extreme pitch setting, made contact with the small loop on the vertical fin, and chopped about 4" off the end of the blade. The whole T/R gearbox was now greatly unbalanced, and tore itself out of the fin.

Losing T/R thrust, and 30kg from 30' back, caused a big yaw and a sharp nose down, the mast had two big bumps and the rotor separated, blade came through left cockpit, killing test pilot, cutting out left side of cabin, and removing tailboom before the lot free-fell and tumbled from 1200', landing inverted.

Other pilot still strapped in right seat, undid seatbelt but floated in zero g over the back of his seat, the crewman on a monkeybelt was also unable to move in the conditions, and had finally adopted the crash position. Both were found on top of the other in the wreckage.

The idea that he had 12 seconds to escape in a freefall from 1200' is ridiculous, and the cabin was twisting and in zero-g, making it difficult to think which way is up.

I had flown that aircraft on its previous flight and was unable to find any fault with it, which is why the test pilot was called in - and it was an unrelated problem that got them. No time to do anything, it all happened in less than 2 seconds. The weird thing was, all the old-timer B-model pilots who later popped up to say, "Oh yeah, those Bravos used to nose over quite often, we never worked out why."

[Hot and Hi]

https://app.ntsb.gov/pdfgenerator/ReportGeneratorFile.ashx?EventID=20160624X83720&AKey=1&RType=Factual&IType=FA

A "factual report" was published in October that, even if not final, seems to confirm Mast Bumping as cause.

Personally I'm somehow "relieved" for the fact that was a sadly well known cause and not some new design flaw that caused the crash..
Thanks Mitch for posting the accident report.


SPEED:

The factual report doesn't state the speed the R66 was flying last the time of accident. The iPad that was on board was found undamaged but couldn't be accessed as the device was password protected (https://dms.ntsb.gov/pubdms/search/document.cfm?docID=457855&docketID=60412&mkey=93446). However, the satellite track (https://dms.ntsb.gov/pubdms/search/document.cfm?docID=457860&docketID=60412&mkey=93446) as recorded by a SPOT device is included in the "Investigation Docket" referenced at the end of the Factual Report and invites for some analysis.

From the Factual Report:
A SPOT device, which is a handheld GPS tracking device that uses a satellite network enabling text messaging and GPS tracking services, was present on the helicopter. Records provided by the operator listed 19 location fixes beginning at Prescott at 1338 and proceeding on a southwesterly heading. The last data point at 1425 was in the vicinity of the accident site.

If you do the math, you find that the SPOT tracker was sending positions every 2.5 min (which is indeed one of the available SPOT settings: 2.5 min, 5min, or 10 min). As per the recorded track, the R66 was flying more or less straight, and constant average speed (the position points are on a straight line, and equidistant). If you average the speed over the 10 position reports before the accident (Position 4 to Position 14), you come the following result:

- Straight line distance 48 NM
- 25 min
- Avg ground speed therefore 115 KT
- Track approximately 250° true
- Magnetic variation in Arizona approximately 10° East, therefore magnetic track approximately 240°

The Factual Report gives the wind (apart from significant turbulence that was reported by a R44 pilot operating on the area around the same time) as 190°, 17 gusting 22 KTS, as reported by a ground station 43 NM to the west of the accident scene. Not sure if wind direction is given in magnetic, or true? But it is fair to say that the mishap aircraft faced a certain headwind component, which means that the average true airspeed was slightly higher than the computed average ground speed of 115 KTS.

SPOT doesn't give altitude information.


WEIGHT:

Again, you have to look into the docket to find the a/c weight at the time of accident (https://dms.ntsb.gov/pubdms/search/document.cfm?docID=457858&docketID=60412&mkey=93446 (https://dms.ntsb.gov/pubdms/search/document.cfm?)docID=457858&docketID=60412&mkey=93446)). It is stated by the Operator of the flight (Guidance Air Service LLC) as 2,221 lbs. So that is not particularly light (consistent with 2 crew plus almost full fuel).


EXPERIENCE ON TYPE:

Both crew members were commercially rates pilots with thousands of hours. The Factual Report says that type-rated passenger (the operator's Part 141 chief pilot) was a helicopter-only pilot with over 5,000 HRS TTRW, but only 101 HRS on type. And nil R66 HRS during the last 30 days before the accident.

Now, the PIC was a 8,000 HRS fix-wing ATP (single/multi engine). He was the operator's Part 135 chief pilot. While apparently rated on the R66, neither his TTRW nor his time on type is filled in the operator's accident report (!).

These, in my opinion, critical numbers are also not stated in the Factual Report, nor is the unavailability of this information discussed. However, it was declared that the PIC only did 10 HRS in helicopters over the past 90 days, thereof only 3 HRS in the past month (all in R66). He also was IF and instructor rated on helicopters.

I hope that the final accident report will dig deeper into what appears to be a "seasoned fix-wing pilot with comparatively low helicopter time flying a R66 in significant turbulence at high speed" scenario.

[n5296s]

Curious what's meant by "type rated" or "rated on the R66". In the US, a CPL-H (or PPL-H) is valid for any helicopter under 12,500 lbs. There's a sort of quasi-type-rating for the R22 and R44, called SFAR 73, but oddly the FAA didn't decide to make this required for the R66 too. Maybe they are still waiting to see if the accident rate is as bad as it was for the R22 in the early days. So if you have a helicopter license, you are good to go in the R66, at least as far as the FAA is concerned. (Insurers may see it differently).

[Hot and Hi]

N5296S

Thanks for pointing out that in the U.S.A. no specific type ratings are needed for a rated helicopter pilot to fly any helicopter below 12,500 lbs MTOW.

While apparently rated on the R66, neither his TTRW nor his time on type is filled in in the operator's accident report (!).
Then I was mistaken to assume that in the U.S.A. there was the requirement to have a R66 type rating before acting as PIC in this type), like there is in other parts of the world. As the Factual Report didn't mention the lack of the PIC being type-rated, I mistakenly concluded that the PIC "apparently" was type-rated.

In conclusion, the Factual Report only informs that the PIC was a fix-wing ATP with over 8,000 HRS total time, and that he had 10 HRS in the R66 over the past 90 days, 3 HRS thereof during the last 30d.

The Factual Report is silent about the PIC's

- total time on rotor-wing
- total turbine helicopter time
- total time on type R66
- any specific instruction he may have received on the R66
- date of his PPL-H and CPL-H ratings
- prior accidents or incidents, if any

I am confident that the Final Report will focus on exactly these questions.

[MitchStick]

Some unconfirmed sources say that both pilots were ex military so while a lot of rotary time not a lot in semi-rigid and even less in Robinson, together they had less then 60 hrs (again unconfirmed source)

I fly a 66 (that's why I'm interested in the report) and personally if I smell turbulence I slow that b*@#h down, 80 70 knots, I have one life and I intend to keep it.

[Spunk]

...17 gusting 22 KTS... is considered to be significant turbulences?

[Hot and Hi]

...17 gusting 22 KTS... is considered to be significant turbulences?
Spunk, no not at all. This is the wind reported by a ground weather station in the area. This information was used to estimate the air speed vs the ground speed taken from the Sat tracker.

"Significant" turbulence is a term used by Robinson Helicopters, and it is operationally defined. It is not directly related to the terms mild/moderate/severe turbulence. Robinson says they deliberately avoid the reference to absolute measures of turbulence (those "moderate/severe" terms, which are not very well defined themselves) but refer to "significant" as in relation to the skills and experience of the pilot. They (rightly, in my opinion) say that what is easy to handle for an experienced pilot, may be significant to a low time pilot. (Sorry, I can't find my source for this right now.) And then they go on in saying that when encountering significant turbulence you should slow down to 60-70 KTS.

Robinson further restricts (however, only after this accident discussed here) VNE to 110KTS IAS "except in smooth air".

The notion of "significant turbulence" came in here via the report from another chopper pilot, which is included in the Factual Report:

... the pilot of an R44 who was performing aerial survey work (the day of the accident) immediately north of the accident site ... stated that beginning at 1130 the winds became stronger and gustier. Over the next couple of hours, he observed numerous dust devils, and experienced a significant updraft in excess of 1,000 ft per minute. About 1515 (local time), he decided to discontinue operations and encountered a significant wind shift while returning to his base.

That certainly was "significant" to the R44 pilot. The accident happened at 1425 local time.

[MitchStick]

And lets not forget the R66 is lighter and has more power than the R44 so worst in turbulence..

The wind speed doesn't really mean much, if you're flying in a mountainous area even 15 knots can create significant up and downdrafts and if you don't slow down could be dangerous.

[megan]

The weird thing was, all the old-timer B-model pilots who later popped up to say, "Oh yeah, those Bravos used to nose over quite often, we never worked out why."Quite a lot of time in the B and neither heard of, nor experienced the tendency. Urban myth or beer talking?The idea that he had 12 seconds to escape in a freefall from 1200' is ridiculousAssuming they were in level flight and subject to zero "g" (actually accelerating under the influence of one "g") following rotor separation it would take a fraction under eleven seconds to reach the ground from 1,200 feet (8.6 seconds if one assumes no drag).

[Ascend Charlie]

Megan, the stories of the Bravos nosing over came up during and after the court of enquiry in 1981, with the Vietnam pilots talking of things that happened in the 60s. Actual experience, not urban myth or "beer talking".

For the freefall, there is no allowance for the time taken for the brain to function. Yes, the time taken for the whole episode might be 11 seconds, if he was ready to go, the door was open, and all things working for him.

However, the first few seconds of the massive yaw and nose-down pitch were of the "WTF is going on???" variety, then the sound and impact of flying glass through the cockpit as the blade cut through the front window, then the left-seat test pilot, then the left side of the aircraft, and the tail boom, and the nose-down spiralling plummet towards the ground. Windspeed through the front window increasing with glass, blood and guts, and the total shock of what is beside him.

He did have the presence of mind to then try to escape, but undoing his seatbelt in zero g just made him float up out of his seat. Maybe had 4 or 5 seconds to try to get out, and even if he escaped he would have been too low for the parachute to save him.

[megan]

stories of the Bravos nosing over came up during and after the court of enquiry in 1981I'd be interested to see the evidence offered AC, until then I'm calling it out. Things get said, even at official enquiries, for all sorts of reasons, protecting reputations being just one. Not that I suggest that here of course. You need to remember that there was no official investigation into the loss of Buckshot 18 with its crew, and the possible reasons why.

[Ascend Charlie]

Megan, you are not responding to the PM sent, so I ask it here:

"Calling it out"???
You reckon I am telling lies about what was said in the court of enquiry? Do you say that the old heads I spoke to after the crash hadn't actually experienced the uncommanded nose-overs?

And why wasn't there a C of I into the CFIT of Buckshot 18?

[megan]

you are not responding to the PM sent, so I ask it hereI'm soooo sorry that I haven't responded with the alacrity you seemingly demand.You reckon I am telling lies about what was said in the court of enquiryWhere in Gods name do you get that notion from? It may have been said in the enquiry, but I'd like to see the evidence offered to the enquiry that the "B" had a propensity in this area. You did say, ""Oh yeah, those Bravos used to nose over quite often, we never worked out why." Whoever made that statement is talking rot IMHO. If the aircraft had a propensity for such Bell/US Army would have rung the bell loud and clear. The RAAF crews making the claim did report the fact through the airworthiness/safety channels as required one presumes? I'll talk to some RAAF Vietnam era pilots to see if there is anything to back the claim that it was an idea they held.And why wasn't there a C of I into the CFIT of Buckshot 18?For the answer to that question you'll have to ask the RAAF, we too would like to know, speaking as some one who knew the pilot when he was but a school boy. A reading of "The Thirteenth Night" by Jan McNess will give info. Too much egg on too many senior officers faces for errors in oversight could be one plausible reason (and certain politicians).

[megan]

AC, talked to some of my Vietnam era RAAF Huey instructors and the only thing we can come up with regard to the nose over is the note in the flight manual.Should the engine malfunction during a left bank maneuver, right cyclic input to level the aircraft must be made simultaneously with collective pitch adjustment. If the collective pitch is decreased without a corresponding right cyclic input, the helicopter will pitch down and the roll rate will increase rapidly, resulting in a significant loss of altitude.

[Hot and Hi]

AC, talked to some of my Vietnam era RAAF Huey instructors and the only thing we can come up with regard to the nose over is the note in the flight manual.
That makes sense for any CCW turning helicopter. And one would intuitively do this, I reckon.

[Hot and Hi]

Apparently the final NSTB report is out. Maybe somebody has to link?

This article (https://www.modbee.com/news/business/article87950162.html) from (I suppose) a local newspaper makes reference to the investigation and reports that a lawsuit against RHC has been filed by the families of the two deceased.

The article mentions that the two pilots were "experienced". As previously discussed (https://www.pprune.org/showthread.php?p=9954427) in this thread their experience may however least have been on the accident type and if I remember correctly mostly on fix-wing aircraft. I am keen to find out what the final report makes of this.

[Bell_ringer]

https://www.ntsb.gov/_layouts/ntsb.aviation/brief2.aspx?ev_id=20160624X83720&ntsbno=WPR16FA130&akey=1

[MitchStick]

https://app.ntsb.gov/pdfgenerator/ReportGeneratorFile.ashx?EventID=20160624X83720&AKey=1&RType=Final&IType=FA

[212man]

It's quite some debris field: https://dms.ntsb.gov/public/60000-60499/60412/609531.pdf I assume it must have been quite low level to have spread itself over 750 yards. By contrast, the Norwegian EC225 hit the ground with no forward speed after the head came off at 2000 ft.

[Hot and Hi]

That’s the one. https://app.ntsb.gov/pdfgenerator/ReportGeneratorFile.ashx?EventID=20160624X83720&AKey=1&RType=Final&IType=FA
And I thought we only had useless accident investigations in our part of the world.

[SASless]

Consider the situation.

Middle of no where Arizona, no radar trace, no data recording, no ELT installed, no witnesses, no survivors.

Add in post crash fire.

As to the length of the debris field....lots of light weight parts being shed....strong winds....not all that amazing it would be as long as it is.

The 225 crash had two main parts....Rotor Head and associated bits...and the airframe.

One thing is certain...the Rotor Blades hit the airframe and the aircraft disintegrated into lots of pieces.

The Investigators worked with what they had.

[Airmotive]

That’s the one.
And I thought we only had useless accident investigations in our part of the world.
You can go to the end of the report and click on the link to the docket.
Or click this one:
https://dms.ntsb.gov/pubdms/search/hitlist.cfm?docketID=60412