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

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

Old 2nd Aug 2016, 22:45
  #81 (permalink)  
 
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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.
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Old 3rd Aug 2016, 00:30
  #82 (permalink)  
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Originally Posted by gator2 View Post
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.
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Old 3rd Aug 2016, 02:43
  #83 (permalink)  
 
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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!
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Old 3rd Aug 2016, 07:18
  #84 (permalink)  
 
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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
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Old 18th Sep 2016, 11:37
  #85 (permalink)  
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Preliminary NTSB Report

http://www.ntsb.gov/_layouts/ntsb.av...R16FA130&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.
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Old 21st Sep 2016, 12:17
  #86 (permalink)  
 
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Looks like another Mast Bumping accident scene...
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Old 10th Nov 2017, 13:46
  #87 (permalink)  
 
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https://app.ntsb.gov/pdfgenerator/Re...ctual&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..
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Old 11th Nov 2017, 02:00
  #88 (permalink)  
 
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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."
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Old 11th Nov 2017, 16:15
  #89 (permalink)  
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Danger Analysis of the Factual Accident Report

Originally Posted by MitchStick View Post
https://app.ntsb.gov/pdfgenerator/Re...ctual&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/d...412&mkey=93446). However, the satellite track (https://dms.ntsb.gov/pubdms/search/d...412&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). 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.
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Old 11th Nov 2017, 23:08
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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).
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Old 12th Nov 2017, 06:36
  #91 (permalink)  
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Type Rating

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.

Originally Posted by Hot and Hi View Post
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.
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Old 12th Nov 2017, 11:54
  #92 (permalink)  
 
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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.
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Old 13th Nov 2017, 19:19
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...17 gusting 22 KTS...
is considered to be significant turbulences?
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Old 14th Nov 2017, 07:56
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Significant turbulence

Originally Posted by Spunk View Post
...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.
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Old 14th Nov 2017, 11:18
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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.
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Old 14th Nov 2017, 15:27
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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 ridiculous
Assuming 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).

Last edited by megan; 14th Nov 2017 at 15:45.
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Old 16th Nov 2017, 23:13
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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.
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Old 18th Nov 2017, 02:48
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stories of the Bravos nosing over came up during and after the court of enquiry in 1981
I'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.
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Old 20th Nov 2017, 04:08
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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?
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Old 21st Nov 2017, 04:29
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you are not responding to the PM sent, so I ask it here
I'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 enquiry
Where 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).
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