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Chinook - Still Hitting Back 3 (Merged)

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Chinook - Still Hitting Back 3 (Merged)

Old 10th Apr 2006, 12:29
  #2021 (permalink)  
John Purdey
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CHINOOK

The emphasis in the last few posts on the need for evidence is very interesting in the light of the repeated sugestion that the aircraft suffered a control failure of some kind. If it did, then how come there was clear evidence that in the final couple of seconds or so of flight, the crew tried to pull up and turn left. I only ask because I would like to know. Regards to all courteous contributers. John Purdey.
 
Old 10th Apr 2006, 13:48
  #2022 (permalink)  
 
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Chinook Evidence

John Purdey

I hope I still qualify as a courteous contributor by your standards. I have been trying to stay away from some of the recent contributions on the site - too many of which seem to have lost sight of what it is about. I welcome ShyTorque's contribution since as an operator he confirms what I said might have happened in my engineering report of Oct 2003 - note might - I do not know either.

I was, though, surprised to see your claim that there is "clear evidence that in the final couple of seconds or so of flight, the crew tried to pull up and turn left".

I have not seen this clear evidence anywhere, indeed perhaps I could remind you of Robert Burke's evidence to the HofL - evidence that is also supported by the AAIB investigator. Perhaps you would be kind enough to give us the source of your comment


Evidence of Squadron Leader Robert Burke
107. Squadron Leader Burke had extensive experience in flying helicopters including Chinooks Mks 1 and 2 and was described by his unit commander in April 1993 as having air-testing skills on the Puma and Chinook which were unique. He was able to provide us with useful information about the problems which he had experienced when testing Chinooks. At the outset of the investigation into the accident he was contacted by Mr Cable and had two or three telephone discussions with him in relation to control positions (QQ 658, 662). Thereafter he had nothing further to do with the Board of Inquiry.
108. After Squadron Leader Burke gave evidence, Group Captain Pulford submitted a statement to us (p 68 of HL Paper 25(ii)) in which he sought to explain why Squadron Leader Burke had not been asked to give evidence to the investigating board. He stated that as the Chinook maintenance test pilot "his flying was conducted in accordance with limited and pre-determined flight test schedules and he therefore lacked the operational currency to provide relevant evidence to the inquiry". This reasoning seems to assume that problems which Squadron Leader Burke might have encountered on test would not or could not occur in operational flying - an assumption whose justification we feel to be in doubt.
109. Squadron Leader Burke spoke to having experienced two engine run ups on the ground at the Boeing factory in Philadelphia while flying with an American Army test pilot (Q 655) and similar run ups when testing the overspeed limiter on the ground at Odiham (Q 680). He also spoke to problems with the multi-point connectors which went from the engines into the DECU. These were of bad design and liable to be displaced by vibration which then produced a power interruption. Although there was a back-up system this did not always work and on two or three occasions pilots had lost control of the engine condition lever. As a result squadrons introduced a procedure whereby crewmen every quarter of an hour checked that the connections had not been displaced in flight (QQ 677-9).
110. At the time of the accident DECUs still presented recurring problems. They were removed from the aircraft when something had gone wrong and returned to the makers who on many occasions could find no fault (QQ 698-9).
111. In relation to possible jams Squadron Leader Burke explained that, due to the complexity of the Chinook control system, a jam caused by a loose article such as the balance spring in the broom cupboard in one of the three axes, pitch, yaw or roll, could lead to quite random results in all three axes sometimes and certainly in two of them. He had personal experience while lifting off from the ground of a jam in one axis affecting the other two (Q 935). He also referred to the problems of DASH runaways in Chinooks of both marks causing temporary loss of control of aircraft (Q 929).
112. Finally, Squadron Leader Burke commented on the rudder input of 77 per cent left yaw found in the wreck of ZD 576:
"That is an enormous rudder input. It is unthinkable to put that in at high speed. As I may have explained, particularly in the Chinook but in any helicopter, the helicopter does not use the yaw input for control once you have gone over 20 knots. It puts an enormous strain on the aircraft because you obtain yawing control in the simplest way by tilting the rotors one left, one right. You are spinning the aircraft about its middle. It is quite difficult to do. The rudder is quite heavy on a Chinook. You have to make a real effort to put that amount of control in. The only conceivable reason that I can think of for putting that voluntarily in as a pilot is if you have partially lost control coming out and you are trying to counteract a yaw one way or the other" (Q 719).
113. Mr Cable told us that, though it was possible that this rudder input was applied before impact, it was also possible that it was due to the force of the impact itself (Q 999).


Can I also remind you that there were two entries on the Supplementary Flight Servicing Register that had potential relevance as a cause of, or a contributory factor to, the accident. These were: Serial 2, SI/CHK 57 relating to the security of the DECU connectors and which applied to the HC2 version only, and Serial 4, a special check on the security of the Collective Balance Spring Bracket Mount called for by S Eng O 7 Sqn following an incident [where the bracket became detached as found in the wreckage of ZD 576] on ZD576 on 10 May 1994. Although the Board included the Supplementary Flight Servicing Register in Annex AK “Extracts from ZD576 F700 and MWO”, they did not include the Supplementary Flight Servicing Certificate (which was eventually supplied by MOD in 2001) and they did not question whether these checks had been carried out and whether the people who did them were trained and competent/authorised to do so.

Are you still sure that a loss of engine or flight control functions could not have caused or contributed to this tragic accident? Nobody else who has made full and proper assessment of all of the available evidence is!
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Old 10th Apr 2006, 15:00
  #2023 (permalink)  
John Purdey
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CHINOOK

John.
We really should stop going around the same bouy, but in answer to your post I recall (I do not have the documents in front of me) Cable's evidence was that at impact the aircraft was in a dynamic maneouvre; it had less than 10 degrees yaw, was banked 5 to 10 degrees to port and pitched up 30 degrees. The Boeing simulation broadly agreed with that. Are you suggesting that it was in a routine steady climb?
And just by the way, you very well know my view about the whole flight path, which is that in those weather conditions, marginal at best, the aircraft should not have been where it was, ie at low level, at speed, heading for hills covered or parially covered in cloud, technical fault or no technical fault. With all good wishes, JP
 
Old 10th Apr 2006, 16:09
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Brian,

Apologies, I have been out all day as my Wife wanted to go to the Artists Emporium at Brive La Gaillarde.

I do not know the answer to your question off the top of my head, but I will make a couple of phone calls and will PM you as soon as I can. Life is hard here. We have reached the time of year when the wines all change price as a new years vintage is added at the lower end of the price range. Trouble is that the new vintage is 2003 which was a totally disastrous year for winegrowers.

A decent bottle of Cahors is now about £3 a bottle.SCANDALOUS!!
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Old 10th Apr 2006, 16:52
  #2025 (permalink)  

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I would like to make a few things clear at this point because I believe one or two people posting here, with little or no helicopter experience and no real idea of the implications of certain engine emergencies, don't seem to have grasped some highly relevant points.

Firstly, helicopters do not follow the same aerodynamic laws as fixed wing. Because of the complexities of control and stability (lack of natural stability, cross-coupling etc), a small movement of any flight control can result in a very large aircraft flight path change. Similarly, to keep a helicopter on a steady flight path, depending on the regime of flight, a surprisingly large flying control input (or small one) may be required when compared to a fixed wing aircraft.

The term "rudder" is misleading because helicopters do not have a rudder. The correct term for the flying controls affecting yaw is "yaw pedals". The way they cause yaw is NOT the same as FW rudder pedal input, especially on the Chinook.

A helicopter with a mechanical flying control problem / failure may be affected in all axes, not just the one axis that might be expected by trying to relate to the fixed wing scenario of elevator/aileron/rudder. In this situation it may appear that the helicopter had responded to a pilot input in a conventional ("fixed wing") fashion, but it may not have done at all. The pilot may have operated one flying control in a particular way but the aircraft may have responded in an unexpected way. Alternatively, the aircraft may have "done its own thing" in one or more, or all axes, when it may have appeared that the pilot was flying the aircraft under control.

Captain Nick Lappos can undoubtedly talk at great length about this. For example on the S-76, in certain situations how yaw / collective interaction can cause the collective to rise and fall significantly when yaw pedal is applied. A pilot input on the yaw pedals can drive the collective up or down, resulting in the aircraft climbing or descending. An input of collective may drive the yaw pedals, resulting in a large yawing action. Use of one control may jam the other. There is a procedure for this in the Emergencies Checklist.

This is by no means unique in the helicopter world. There is currently an ongoing investigation into a fatal accident involving an S-76 where the aircraft may (or may not) have responded incorrectly to pilot inputs and spiralled rapidly downwards into the sea. Not a usual flight regime. A mystery, even with a CVR.

John Purdey, regarding your last paragraph; like it or not, flying in marginal VMC is how SH often gets the job done, especially if there is no IFR contingency, as in this case. To go over old ground yet again; Mr. Holbrook, the yachtsman who was an eye-witness to the aircraft, gave evidence that the helicopter was flying slowly enough over the sea for him to initially think it was carrying out a search in his vicinity. This indicates that the handling pilot had slowed the aircraft down in marginal weather conditions. This is completely normal - that is how the SH job gets done.

Gp Capt. Peter Crawford, like many of us, could not, at the the time of giving his evidence, understand how the aircraft had rapidly accelerated and climbed until it hit the hillside. However, an engine runaway up would require immediate rapid pilot intervention to contain the Rotor(s) RPM (usually known as NR). The only way to do this is to apply a large amount of collective pitch. This WOULD result in a climb and/or a rapid acceleration of the aircraft, no doubt about that. RAF helicopter pilots are trained, in the event of engine malfunctions (notice I didn't say failures) to concentrate on NR and contain it. Only then can the crew diagnose the problem and take the necessary further actions to control or shut down the faulty engine (handling pilot flies, non-handling pilot operates engine controls, having consulted the emergency checklist and confirmed his actions in advance with the handling pilot). In a twin engined helicopter it is critical to carry out these actions correctly and in the correct order to safeguard the NR, the transmission system and the integrity of the airframe.

IF an engine runaway up occurred in this particular case, (I'm not saying it did, but it was possible) at this critical time, causing the aircraft to enter IMC, coupled with the crew not being able to speak across the cockpit efficiently, because of a faulty intercom, a few seconds of miscommunication could easily have resulted in the accident.

Last edited by ShyTorque; 10th Apr 2006 at 22:02.
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Old 10th Apr 2006, 20:42
  #2026 (permalink)  
 
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Brian Dixon

Could you please empty your PM box.
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Old 10th Apr 2006, 21:01
  #2027 (permalink)  
 
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John Purdey and John Blakeley
JP, you wrote:
<< …how come there was clear evidence that in the final couple of seconds or so of flight, the crew tried to pull up and turn left.>>
More correctly, (in addition to pull up and turn) tried to slew hard left to present broadside which is a recognized way of rapidly slowing down a large twin rotor a/c like a Chinook as described sometime by Sqn Ldr Robert Burke, if I recall correctly, in response to someone saying that it was an unsuitable manoeuvre. That is to say, the final control positions were indeed compatible with an urgent evasive manoeuvre, say, on realization of proximity to the ground and so should not be only regarded as evidence of a prior control problem.
I cannot find the quote (and its context) just now but will dig it out when I have time.
This is notwithstanding the statements quoting Sqn Ldr Burke that John Blakeley has posted.
I am surprised that others have not mentioned this manoeuvre or at least Sqn Ldr Burke’s alternative comments.
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Old 10th Apr 2006, 21:15
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Final manoeuvre


Oh! Here’s another reference to the manoeuvre to be going on with:

From
Select Committee on Chinook ZD 576
Supplementary memoranda following October Hearings

Question 590
Captain Hadlow said that he considered that the position in which the rudder was found by the Air Accidents Investigation Branch (a 77 degree left pedal 1.7 inches forward) was a last ditch effort to turn the aircraft.
Small yaw pedal inputs are used with cyclic to maintain balanced flight when performing a turn at low speeds but at higher forward speeds little or no yaw input is required to turn the aircraft. But large yaw pedal inputs are made, with cyclic and collective, during "hover" turns and when also performing "fast stops". This technique uses all the flying control inputs to turn the aircraft into a sideways position whilst in forward flight, in order to use its large surface area to act as an air brake and assist in the rapid reduction of speed.
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Old 10th Apr 2006, 21:23
  #2029 (permalink)  
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Cazatou,
my apologies. Please try again.

Thank you.
Brian
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Old 10th Apr 2006, 22:07
  #2030 (permalink)  

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"Question 590
Captain Hadlow said that he considered that the position in which the rudder was found by the Air Accidents Investigation Branch (a 77 degree left pedal 1.7 inches forward) was a last ditch effort to turn the aircraft."

Can someone please remind me who Captain Hadlow is - and is he a helicopter pilot? What "rudder" was he referring to? The Chinook, in common with every other helicopter in common use, does not have a rudder.
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Old 10th Apr 2006, 22:14
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Shy,
he was one of the authors of the Three Fellows (of the RAeS) Report.

The report says that he is a retired airline captain and Armed Forces Helicopter pilot.

Hope that helps.

Brian

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Old 11th Apr 2006, 13:35
  #2032 (permalink)  
John Purdey
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CHINOOK

ShyTorque
Very interesting, many thanks. As to the yachtsman, he thought he was looking at a small helicopter at low speed as I recall. So was it in fact a small helicopter, fairly close in and at slow speed, or a large helicopter rather further away and at high speed? If he was looking at the Chinook, then surely the second case fits the bill? Regards JP
 
Old 11th Apr 2006, 17:41
  #2033 (permalink)  
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Hi Mr Purdey,
I regret to point out that your recollection of Mr Holbrook's recollection is inaccurate. What he actually said, (in respect to your claim), was this:

Seven years have now passed since the accident however, and therefore in order to refresh my memory I have had to now review the papers sent to me by Mr Makower, and in that review I have been surprised and distressed to understand from the evidence to this inquiry from Air Chief Marshal Sir William Wratten that the nub of the issue as far as the finding of Gross Negligence on the part of the two pilots turns on the flight rule regime that the aircraft was in at the time that I, as the last eyewitness, saw it.

The reason I am surprised, my Lord Chairman, is that throughout the last seven years I have always felt that my evidence was nothing other than corrobatory - confirming what had already been gleaned from other witnesses and events. It now seems to me however, if I have understood Sir William's evidence correctly, that the direction, altitude, attitude, speed and visibility that the aircraft was experiencing at the time of the last sighting is central to a determination if the crew had an option available to them to continue under visual flight rules or alternatively had to make a transition to instrument flight rules.

Against that yardstick of relevance to the finding of Gross Negligence on the part of the aircrew, my Lord Chairman, I have to tell you and your Committee that I feel my evidence was not collected with either the diligence or professionalism that the aircrew or their families have a right, from my perspective as a layman, to expect.

There are a number of issues that I have with the way that I have been debriefed which, my Lord Chairman, you may wish to question me about, however the chief amongst these is that my sighting of the aircraft was limited to a five-second view since I was involved in a difficult situation on my boat at the time. I am by training however a research worker, I have been trained to observe a situation which in itself may very well be outwith my ken.

I had, at the time, a vivid mental picture of the aircraft which if I had been debriefed fully would surely have yielded more information about those fateful last minutes than you have in front of you today. To this day, My Lord, despite having asked repeatedly, I have never seen photographs of the aircraft at different heights and ranger, never mind had the opportunity of seeing one of the aircraft flying at differing speeds or climbing.

As you will appreciate, when I saw the aircraft it subtended a particular angle, it occupied a portion of my field of view, if you will, and my interpretation of range and height is therefore totally reliant on my knowledge - or lack of it- of the size of the aircraft itself.


So, as you see, Mr Holbrook, himself is unclear as he feels he was never properly debriefed. He made comment that the helicopter was, by his estimation (and he stressed that it was just that - an estimation), of between 200-400 feet. He gave an estimated speed of 60-80 knots, butpointedout that it would have been useful to have had the opportunity to observe an aircraft flying at those speeds. He further commented:

The aircraft was travelling sufficiently slowly that I remarked to my crewman that "here's an aircraft come down here to have a look at us" and we had thought it may have been involved in a search and rescue operation, it was travelling that slowly, and in fact I asked my crewman to go and listen to the radio to pick up signals about there being any activity of that type.

I hope that clears up to all, what Mr Holbrook said in his evidence to the HoL Select Committee.

My best, as always.
Brian

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Old 11th Apr 2006, 19:46
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Brian. Not sure what your point is. The yachtsman says that he thought the helicopter was flying at 60-80kts. Please read again the two possible interpretations of what he saw, ie slow/near/small or large/distant/fast. Reagards as always JP
 
Old 11th Apr 2006, 19:53
  #2035 (permalink)  
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JP

Doesn't that leave just a little doubt??

Best wishes

XM147
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Old 11th Apr 2006, 20:26
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John Purdey
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XM147
No. Because we know it was large, therefore it must have been distant and fast. Check you logic! All good wishes. JP
 
Old 11th Apr 2006, 20:59
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Having read what Mr Holbrook said it does appear to me to be a rather damning indictment of the way in which the members of the BOI collected, and presented, the evidence given to them by members of the Public.
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Old 11th Apr 2006, 21:26
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A tradition that has been maintained through to the F15 enquiry too, it seems.
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Old 11th Apr 2006, 21:39
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JP

Mr Holbrook: The aircraft was travelling sufficiently slowly that I remarked to my crewman that "here's an aircraft come down here to have a look at us" and we had thought it may have been involved in a search and rescue operation, it was travelling that slowly, and in fact I asked my crewman to go and listen to the radio to pick up signals about there being any activity of that type.

This does not and never will, to me, suggest 'distant and fast'. In fact quite the reverse.

My doubt remains!

Best wishes, XM147
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Old 11th Apr 2006, 23:15
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JP

At the risk of this debate getting reminiscent of an episode from Father Ted; I can understand small/near as opposed to distant/large. I fail to understand near/slow as opposed to distant/fast unless it's over distances at which an a/c would hardly be recognisable as a helicopter.
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