CHINOOK ZD576 - THE FATAL ACCIDENT OF JUNE 1994
ANALYSIS PREPARED ON BEHALF OF THE
PARLIAMENTARY MULL OF KINTYRE GROUP
Contents
Executive Summary
Introduction
Statutory Requirements
Standard of Proof required for a finding of negligence
Evidence supporting a finding of gross negligence
Alternative causation factors
Additional evidence not considered by the Board of Inquiry : the CA Release
history
The Airworthiness Chain
Conclusion
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CHINOOK ZD576 - THE FATAL ACCIDENT OF JUNE 1994
ANALYSIS PREPARED ON BEHALF OF THE
PARLIAMENTARY MULL OF KINTYRE GROUP
Executive Summary

On 2nd June 1994 an RAF Chinook ZD576 crashed on the Mull of Kintyre killing
the crew of 4, together with 25 military and civilian passengers. A RAF Board of
Inquiry (BOI) into the causes of the accident followed. Senior officers reviewing
the findings of the initial BOI (the “Reviewing Officers”) were of the opinion that
the crash was caused by gross negligence on the part of Flt. Lt. Tapper and Flt.
Lt. Cook.
1

The BOI ‘despite detailed and in depth analysis’ was unable to determine a
definite cause of the accident. The Air Accidents Investigation Branch (AAIB)
inspector commented that the evidence was remarkably thin. There was no
flight data recorder and no cockpit voice recorder. The BOI did not make a
finding of negligence on the part of the crew.

The Reviewing Officers reached a conclusion of gross negligence based on the
same evidence which had been reviewed by the Board, despite their own doubts,
the doubts expressed by the Board and by the witnesses who gave evidence to it.
ACM Wratten stated:
2
‘Without the irrefutable evidence which is provided by an ADR and a CDR,
there is inevitably a degree of speculation ...’
3

A finding of gross negligence can only be made against deceased aircrew ‘in
cases in which there is absolutely no doubt whatsoever’. This is a deliberately
high standard of proof, approved by the Air Force Board, because deceased
aircrew cannot give evidence and are not represented. In reaching their
conclusion, the Reviewing Officers had been unaware of or had misunderstood
this standard of proof and consequently failed to act in accordance with the
statutory requirements for Boards of Inquiry.
4

This conclusion was found to be mistaken by the Fatal Accident Inquiry , by the
House of Lords Select Committee (HofLSC) and by other experts including
members of the Royal Aeronautical Society (RAS) .
The House of Lords
concluded:
5
6
The Reviewing Officers referred to were Air Vice Marshal (AVM) Sir John Day and Air Chief Marshal (ACM) Sir William
Wratten.
1
2
RAF Proceedings of a Board of Inquiry into aircraft accident assembled 3 June 1994 to inquire into the accident
involving Chinook HC2 ZD576 on 2 June 1994, included in written evidence submitted to the HofLSC on Chinook
ZD576 (“BOI Report”), Part 2, p.16
3
ibid Part 5, p.23
4
Air Publication (AP) 3207, Chapter 8, Annex G
5
Fatal Accident Inquiry, Sheriff Court, Paisley - January 1996
6
Royal Aeronautical Society, Flight Operations Group, Chinook Accident Study Group: RAF Chinook Mark 2 Mull of
Kintyre Accident 2 June 1994; paper prepared for the [Learned] Society Board 12 March 2000
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‘It is not our role to determine the likely cause of this accident, and indeed
on the evidence which we have heard and read it would be impossible to do
so. We are nevertheless satisfied, on the evidence before us and against the
standard of ‘absolutely no doubt whatsoever’, that the Air Marshals were not
justified in finding that negligence on the part of the pilots of ZD576 caused
the crash.’
7

The Ministry of Defence’s (MOD) interpretation of the standard of proof of
‘absolutely no doubt whatsoever’ is legally incorrect and contrary to the spirit
and intention of the Statutory Requirements. The test is capable of practical
application, but the standard can only be reached in cases where there is
positive evidence of negligence, e.g. from witnesses or from a flight data or
cockpit voice recorder. In the case of ZD576 no such evidence was available.
Absence of evidence of a definite alternative cause is insufficient.

There is no factual evidence that the aircrew were negligent; there is factual
evidence to suggest that any of a number of mechanical failures could have
occurred. The Reviewing Officers and subsequently the MOD took the view that
the absence (as they saw it) of hard evidence of aircraft failure equated to hard
evidence that there was in fact no aircraft failure and, that being the case, the
pilots must have been negligent; this was clearly wrong.

There is no evidence that the pilots ever intended to fly over the Mull; there is
evidence that they did not. There is no evidence to conclude that they were not
properly entitled to continue flying under Visual Flight Rules (VFR) and MOD has
acknowledged this. MOD has also conceded that there may have been a latent
control jam preventing the helicopter from turning and that the aircrew might
not have had any indication of it until they tried to instigate a change of course.
8
9

The cause of the accident can never be ascertained but at least six technical
failures have been identified, any of which could have caused the accident and
none of which can be disproved on the basis of the facts. Each is a more
plausible explanation of the crash than gross negligence and casts sufficient
doubt on the cause to render a finding of gross negligence against deceased
aircrew unsound. There is positive evidence for at least two of the scenarios.
10

Subsequently a US Army Chinook suffered a flight control malfunction causing it
to roll over in flight. The crew survived to explain what had happened, but no
cause was ever found and it was finally postulated to have been the result of
contamination of hydraulic fluid. There was contamination of the hydraulic
fluid in ZD576.
11

The Chinook Mark 2 fleet and ZD576 specifically had suffered from a number of
mechanical problems prior to the crash. ZD576 had suffered a significant
mechanical failure three weeks before the crash when the collective balance
spring mounting bracket became detached ; this could have caused a control
12
7
House of Lords Report for the Select Committee on Chinook ZD576, 31 January 2002, p.6
Letter dated 10 November 2005 from Rob Lingham, Assistant Director of the Directorate of Air Staff, MOD to Lord
Jacobs.
8
9
Letter Rob Lingham, Assistant Director, Directorate of Air Staff, MOD to Lord Jacobs dated 8 April 2005
10
AAIB statement to RAF Board of Inquiry and see Annex D
11
Flightfax Army Aviation Risk-Management Information December 1998, Vol. 26 No. 15 p.2
12
Serious Fault Signal HJH/H80/OGH/KQA/H8G DTG 111210MAY94 and see Annex D
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jam capable of causing the crash. A week later, and then again on the morning
of the crash, there was a problem with the power turbine inlet temperature
gauge.
13

Boscombe Down had refused to certify the Mark 2 Chinook as airworthy in
October 1993.
Their advice was overridden and the Mark 2 was put into
operational service. On the day of the accident, Boscombe Down had again
suspended flight trials for the second time, in part because of problems with the
FADEC software.
14
15

The Board of Inquiry was not aware of on-going litigation being conducted by
the MOD against Textron Lycoming in relation to negligent design of the FADEC
software, which was settled in favour of the MOD.
16

The Board of Inquiry did not investigate elements of the airworthiness chain.
They did not consider the quality of the Boeing conversion, the deficiencies in
documentation, such as the Flight Reference Cards, the adequacy of training of
crew and ground staff or the quality of maintenance work.

In the light of the considerable uncertainties about the cause(s) of the crash, a
verdict of gross negligence on the part of the pilots cannot be reached with
‘absolutely no doubt whatsoever’. The reputations of Flt. Lts. Tapper and Cook
have been unjustly tarnished because this standard of proof has not been
properly applied.
Introduction
The purpose of this document is:
To explain how the Board of Inquiry’s Reviewing Officers, and the MOD, have
failed to understand or properly apply the test that must be met before finding
that a pilot, killed in the course of duty whilst flying the aircraft provided to him
by the MOD, can be found negligent.

To set out relevant evidence that should have been considered by the initial
Board of Inquiry or whose appearance since that time justifies its re-opening
and/or the quashing of its conclusions.
When the newly modified Mark 2 Chinook ZD576 crashed on the Mull of Kintyre on
June 2, 1994, it was not possible to ascertain what had caused the crash. The RAF
Board of Inquiry concluded:
‘There were many potential causes of the accident and despite detailed and
in depth analysis, the Board was unable to determine a definite cause.’
17
Maintenance Work Order No 1 ECU PTIT rises to 950 deg C 17 May 1994 which appears at Annex AK to the Board of
Inquiry Report.
13
14
A&AEE Report TM2210 HC Mk2 Interim CA Release October 1993
Letter from Office Commanding Rotary Wing Test Squadron to DPM Chinook, Procurement Directive MOD Ref.
AFW/R/127/04 Re: Current Safety of Continued Chinook HC2 Trials Flying 2 June 1994
15
Claim by MOD against Textron Lycoming under Contract G4314; letter by Mr J. Holmes, Principal Director of
Procurement, British Defence Staff Washington to Mr S. White, Vice President, Military Engine Programs Textron
Lycoming 16 March 1990
16
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The Air Accident Investigation Branch (AAIB) inspector, Mr Cable, reported that he
could not confirm pre-impact serviceability of the aircraft because the evidence was
'remarkably thin'. Not only was there no evidence available from flight data or
cockpit voice recorders, this was a multiple impact crash so it was not possible to
establish the sequence of events and what exactly had occurred pre- and post-impact.
However, he was able to identify six potential technical failures which may have
occurred before impact. Much of the wreckage was damaged by fire.
18
19
In addition, examination of evidence, including some evidence that was not available
to the Board of Inquiry, casts doubt on the airworthiness of Chinook HC Mk2s in
general and on the airworthiness of ZD576 in particular.
RAF Boards of Inquiry are modestly staffed and not normally expected to sit for more
than a few weeks, so that any key officers may return to their primary duties. Hence
it is entirely understandable that subsequent reviewing bodies, such as the Fatal
Accident Inquiry, the HofLSC and the RAS, the Committee on Public Accounts, have
been able to scrutinise the accident in much greater depth, taking into account
evidence not before the Board or not fully considered by the Board. All have
concluded that the opinion of the Senior Reviewing Officers, that the pilots of ZD576
were guilty of gross negligence, is unsound and unjust.
20
The existence of considerable doubt about the cause of the accident was
acknowledged by the initial Board and by the accident investigators, and has been
independently confirmed on several occasions. The standard set by Air Force
Regulations for findings of negligence against deceased aircrews is that: ‘Only in
cases in which there is absolutely no doubt whatsoever should deceased aircrew be
found negligent’ The central argument against the Senior Reviewing Officers’ finding
of negligence is that, on the basis of both new and old evidence, that standard could
not and cannot be met.
21
Nevertheless, two Secretaries of State and two Chiefs of the Air Staff committed
themselves to supporting the opinions of the Reviewing Officers, even though they
were not supported by the Board of Inquiry Report. One Secretary of State (Sir
Malcolm Rifkind) has since concluded that he was misled , as has the Prime Minister
of the day. Yet the MOD has so far declined to revoke the conclusions of the
Reviewing Officers or to subject the additional evidence to examination in accordance
with its own statutory Guidance.
22
23
Despite the fact that this crash occurred over 13 years ago, it is still a live issue, not
only to the families involved, but to serving members of the RAF and to the public
generally. A recent fictional TV programme, Silent Witness, was loosely based on the
Mull of Kintyre crash. There is a widespread belief that the finding of negligence on
the part of the deceased pilots was unjust and, inevitably, this must impact on
morale in the RAF and on confidence in the government.
Report of RAF Board of Inquiry; Written evidence submitted to the Select Committee on Chinook ZD576 Part 2, para
61
17
18
HofLSC on Chinook ZD576 7 November 2001, p.47
19
Annex D
20
See Annexes I, J, K and L
21
AP3207 Chapter 8 Annex G para.9
22
Press article dated 27/11/97
23
Times online article dated May 13, 2004
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Statutory Requirements (See Annex A)
By letter of 27 November 2006 , the Secretary of State for Defence advised Sir
Malcolm Rifkind, his predecessor of 1995, that,
24
‘The Royal Air Force Board of Inquiry procedure is governed by statutory
rules made under Section 135 of the Air Force Act and Chapter 17 of the
Queen’s Regulations…… as at 1994, amplified and explained by Chapter 8 of
Air Publication (AP) 3207…’ (“the Guidance”)
Lawyers acting for the Mull of Kintyre Group has since examined the statutory
requirements (appendix to Annex A) in detail and concluded that the MOD failed in
its statutory obligations with respect to:

the requirement, which pervades the regulations, that aircrew accused of
negligence should have the right to defend themselves. Surviving aircrew have
the right to be present or to be represented, specifically:
-
the right of aircrew ‘whose character or professional reputation may be
affected by the findings’ to attend the Board of Inquiry and be represented
and to ‘give evidence, question witnesses or produce any witness to give
evidence on matters which may affect him’
25
-
the right of aircrew found negligent to ‘read the proceedings and be invited
to make a statement (which is to be attached to the proceedings) giving any
reasons why he should not be held to blame.’ The same procedure applies if
the convening officer or any superior authority attributes negligence to a
person not found negligent by the Board.
26
-

the necessarily different treatment of evidence in the case of deceased
aircrew given the absence of any provision for deceased aircrew to be
represented and the imposition of a different standard of proof.
the requirement that ‘judgment should not be passed upon an officer or airman
who has had no opportunity of giving evidence at the Board of Inquiry or of
making a statement’. This is consistent with the provisions of Annex G, which
gives detailed guidance on the consideration of human failings, and introduces a
higher standard of proof for finding a deceased pilot negligent. Paragraph 9 of
Annex G provides the only direct assistance to a Board of Inquiry in relation to
findings of negligence against deceased aircrew: ‘only in cases in which there is
absolutely no doubt whatsoever should deceased aircrew be found negligent.’
This standard of proof is discussed in more detail in the section below: it is
deliberately a high standard because there is a presumption throughout the
regulations that deceased aircrew should generally not be found negligent
27
Letter 27 November 2006 from Secretary of State for Defence to Rt. Hon. Sir Malcolm Rifkind MP, reference D/S of
S/DB MC06138/2006.
24
25
Board of Inquiry (Air Force) Rules 1956 Rule 11 and Queens Regulations, Chapter 17, Para 1264
26
Queens Regulations, Chapter 17, Para 1269(7)
27
Air Publication (AP) 3207 - the RAF Manual of Flight Safety Chapter 8, Para 141
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
the Board’s duty to base its findings on fact, specifically to be ‘careful to ensure
that its findings are supported by evidence’ and further ‘not express an opinion
unless it is an inference from established fact’
28
29

The MOD has taken issue with the conclusions of the HofLSC and others, and
produced its own interpretation of the guidance in AP3207 . This is addressed
in detail in Annex B, but in our view the MOD’s arguments are significantly
undermined by inter alia the written evidence to the HofLSC given by Group
Captain Derek Hine who in 1982 was appointed Chairman of an RAF Working
Party tasked by the Air Force Board to examine Boards of Inquiry into flying
accidents. In written evidence to the HofLSC he stated:
30
31
‘... items from the wreckage, e.g. altimeters, cockpit voice recorders and inflight data recorders might reveal carelessness by the crew. However,
without this sort of overwhelming positive evidence, BOI’s are very wrong to
fill in the gaps to support the most probable cause.’ (his underlining)

the failure to consider evidence not available to the Board: the Board of Inquiry
may be ordered to be reconvened if ‘it appears from a study of the proceedings
that some evidence available to the Board has been omitted or that some relevant
aspect has not been covered adequately’.
32

the failure to ‘pay due regard to the responsibility borne by personnel filling
supervisory and staff appointments’.
33
Standard of Proof required for a finding of negligence (see Annex B)
The Guidance states:
‘Only in cases where there is absolutely no doubt whatsoever should
deceased aircrew be found negligent’
34
These words were coined by the Hine Working Party in 1982. Hine explained that this
demands a high degree of proof:
‘That was the intention. (his emboldening) Deceased aircrew cannot give
witness; they do not have the luxury of civilian law, nor any form of defence
or appeal. The BOI is not a court of law, it is a tribunal of officers who are
experts in their own field but not in law.’
35
This wording was agreed by the MOD and by the RAF.
28
Queens Regulations, Chapter 17, Para 1270
29
AP3207 Chapter 8, Para 74
See Section 6 at pages 24-26 in the Government’s Response to the Report from the Select Committee on Chinook ZD
576, House of Lords Session 2001-2002 (HL Paper 25 (III) 22 July 2002 (“Government Response of 22 July 2002”).
30
31
Derek Hine Statement to the HofLSC September 2001, p.3
32
AP3207 Chapter 8, Para 153
33
Queens Regulations, Chapter 17, para 1264
34
AP3207 Chapter 8 Annex G para.9
35
Derek Hine Statement to the HofLSC September 2001, p.3
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‘… the Air Force Board cleared the “conditions of negligence” in their
original wording. It was the intention of the Air Force Board et al that this
recommendation should be “set in stone” and incorporated into the Manual
of Flight Safety as a regulation to be followed by all involved in the BOI
process - ie the Board (under its President) and ALL subsequent stages of the
Higher Authority process.’
36
The background to this standard of proof was the findings of the Hine Working Party:
‘We found unanimous opinion throughout the RAF that it was offensive to the
principles and traditions of our Service to pronounce deceased aircrew
Negligent without overwhelming positive evidence to support this. They had
paid the highest price (for our Nation) and were not able to offer their own
defence, be represented or appeal. It is interesting to reflect that, had these
individuals lost their lives “on active service” - for whatever reason - they
might well have been listed as Our Glorious Dead and remembered each
Armistice Day.’
37
Despite the intentions of the Hine Working Party and the Air Force Board, in their
response to the HofLSC, the Government Response stated:
‘The “absolutely no doubt whatsoever” test was intended to be capable of
practical application, and in the view of the Department required a
distinction to be drawn between honest or genuine doubt and implausible
conjecture. Thus it was not permissible to avoid a finding of negligence by
recourse to an hypothesis for which there is no evidence and which is
revealed as wholly implausible when tested against the known facts.’
38
In fact, contrary to MOD’s opinion, this standard is capable of practical application
but is not capable of application in every situation, nor indeed is there any statutory
requirement that it should be capable of universal application.
As described above, Hine clarified the standard in his evidence to the HofLSC.
Referring to evidence from cockpit voice recorders and in-flight data recorders, he
said that :
‘Without this sort of overwhelming positive evidence, BOIs are very wrong to
fill in the gaps to support the most probable cause.’ (his underlining)
39
Thus it is perfectly possible for the standard of proof to be met, but in the case of
ZD576 it could not be. Had the aircrew survived, the standard of proof would of
course have been lower and the Board would have been entitled to draw (rebuttable)
inferences.
There is no requirement for any fanciful hypothesis to be entertained, but the
existence of any doubt which is not fanciful must invalidate a finding of negligence
on the part of deceased pilots.
36
Derek Hine Statement to the HofLSC September 2001, p.3
37
Derek Hine Statement to the HofLSC September 2001, p.2
38
Government Response of 22 July 2002, paragraph 4 on page 24
39
Derek Hine Statement to the HofLSC September 2001, p.3
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It is our view that doubt exists. The Board of Inquiry itself expressed doubts about
the role that human failings played in the accident. The proper determination, based
on the uncertainty and limited nature of the evidence before the Board of Inquiry,
was either ‘Error of Judgement’ or no disciplinary verdict at all in respect of human
failings.
The reason that the existence of doubt rules out a finding of negligence is that the
standard of proof to show negligence on the part of deceased aircrew is, as described
above, deliberately a high one, and has not been met.
Evidence that has subsequently come to light adds further reasonable doubt to the
doubts that already existed. This evidence is reviewed in Annexes F and G.
A number of alternative causation factors, any of which might completely or partially
account for the accident, exist, which are consistent with the scant factual evidence
available. These were considered by the HofLSC, refuted by the Government in its
response and are reviewed in Annex E.
Evidence supporting a Finding of Gross Negligence
The Board of Inquiry was unable to determine the cause of the accident and did no
more than speculate that human failings on the part of Flight Lieutenant Tapper
could have contributed to the accident:
‘... could find no evidence that Flight Lieutenant Tapper had not approached
and prepared for the sortie in anything other than a thorough and
professional manner. The Board was unable to positively determine the
sequence of events leading up to the accident, and therefore concluded that
although it is likely that Flight Lieutenant Tapper made an Error of
Judgement in the conduct of the attempted climb over the Mull of Kintyre, it
would be incorrect to criticise him for human failings based on the available
evidence.’40
Group Captain Crawford, reviewing the Board’s findings, stated that:
‘In assessing human failings, the evidence is insufficient to be specific.
However, there is no indication of a major technical malfunction and Flight
Lieutenant Tapper and his crew were undoubtedly competent to carry out
the mission. In carrying out that mission, Flight Lieutenant Tapper, as
captain of an aircraft in peacetime, had an overriding duty to ensure the
safety of the aircraft, its crew and the passengers. While there may,
arguably, be some mitigating circumstances, I am regrettably drawn to the
conclusion that he failed in that duty.’41
This statement is internally inconsistent and illogical. In his evidence to the HofLSC,
he clarified that he had not made a determination of negligence in relation to either
pilot .
42
40
Board of Inquiry Conclusions, paragraph 67(c)
41
Board of Inquiry : Remarks of the Station Commander, RAF Odiham, paragraph 6
42
House of Lords Select Committee, Minutes of Written Evidence 7 November 2001, paragraphs 902-907.
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It was only the subsequent comments of the Reviewing Officers (see Annex C) that
attributed gross negligence to both pilots. In their remarks neither AVM Day nor ACM
Wratten adduced any evidence to support their conclusion that both pilots were
guilty of gross negligence; they merely substituted one speculative explanation for
others considered by the Board. Not only did they fail to meet the standard of
‘absolutely no doubt whatsoever’ they did not base their opinion on established fact,
as required by the Queens Regulations and the RAF Manual of Flight Safety.
AVM Day stated:
‘It is incomprehensible why two trusted, experienced and skilled pilots
should, as indicated by all the available evidence, have flown a serviceable
aircraft into cloud covered high ground.’
43
It is even more incomprehensible why three highly experienced crew members would
have failed to act correctly .
44
ACM Wratten stated:
‘Without the irrefutable evidence which is provided by an ADR and a CVR,
there is inevitably a degree of speculation ...’
45
In their evidence to the HofLSC, the Reviewing Officers made it clear that they were
basing their finding of negligence on the assumption that the pilots intended to fly
over the Mull. There are a number of reasons why such an assumption is incorrect.
As Group Captain Crawford pointed out to the Board of Inquiry:
‘In looking for alternative causes I have no new evidence to call upon and all
I can do is put a different emphasis on factors already considered by the
Board. By working "forward" from the departure point, I conclude it is highly
probable that rather than electing to climb over the Mull the crew saw the
coast and decided to continue VFR to the west of the Mull Peninsula.’
‘This WP change is crucial in trying to understand what the crew intended to
do. If they had intended to abort at this stage and climb over the Mull
despite the difficulty, which would have been so obvious to them, of clearing
the high ground they would not have selected the Corran WP.’
‘The root cause of this accident is that the crew while operating in poor
weather and close to high ground flew the aircraft into the ground.
However, the reasons for this are, I believe, open to conjecture and, in the
absence of hard evidence, I do not feel there is much to be gained by
speculating on the actions that led to the last few seconds of flight.’
46
43
Board of Inquiry Report, Part 4, Remarks of AOC, paragraph 6.
See the written submissions of helicopter pilots Flt Lt Heald and Flt Lt Scott to the Fatal Accident Inquiry (FAI),
December 1995.
44
45
Board of Inquiry Report, Part 5, Remarks by AOC-in-C, paragraph 1.
46
FAI, p.110
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The Reviewing Officers and MOD suggested to the HofLSC that the negligence had
occurred by the time the pilots made the waypoint change.
‘If they were in cloud then the flight should have been in accordance with
Instrument Flight Rules (IFRs). If not, then they had flouted the basic rules of
airmanship by flying too fast and too close towards the cloud-covered high
ground of the Mull.’
47
The Reviewing Officers made a number of assumptions about the weather at the Mull
at the time of the crash. These are discussed in Annex C. The Royal Aeronautical
Society also reviewed the evidence relating to the weather. The precise weather
conditions at the waypoint change are, and will remain, unknown but evidence to the
FAI and to HofLSC from the yachtsman, Mark Holbrook, suggests that the conditions
were better than believed at the time of the BOI. In his evidence to the HoL Select
Committee he explained that if he had ‘been asked to speculate if the crew could see
from their vantage point the cliffs, beach and lower walls of the lighthouse complex
(he) would again answer “yes”.’ Even on the basis of the evidence given to the BOI, as
cited by Gp Ct Crawford, it was appropriate for the flight to be VFR. MOD has
conceded in a letter to Lord Jacobs that :
48
49
50
‘(c) It is not mandatory to transfer to IFR if the aircraft is flying below cloud
and visibility ahead is good below the cloud. However, a pilot operating
within the UK low flying system (as ZD576 was doing) would need to
maintain a minimum of 500ft vertical separation with the cloud and 1500m
horizontal separation if he wished to continue in VFR.’
51
Note that this requirement only applies where the speed is above 140 kts. The second
Boeing simulation suggested a speed of 130 - 135 kts.
‘(d) If a pilot intends to change direction at a waypoint which will take the
aircraft away from cloud it is not mandatory to transfer to IFR.
(e) It is not mandatory for a pilot to transfer to IFR if they will be flying
below 140 knots in clear visibility but parallel to cloud. Above that speed
they should stay 1nm horizontally away from the cloud.’
52
It is our case that there is no factual evidence to support a conclusion of negligence,
gross or otherwise, by the pilots. The Reviewing Officers failed to comply with the
Regulations with respect to both the standard of proof and the requirement to base
their opinions on fact. Their conclusion is mere conjecture, based on a false
assumption and, in our view, a less likely explanation for the accident than a number
of alternative causation factors.
Alternative Causation Factors
47
HofL Select Committee 16 October 2001, p.15
Royal Aeronautical Society Addendum to 20 April 2000 Report:
accident, 2 September 2000.
48
Notes relating to weather at the time of the
See the Determination and Note by Sheriff Sir Stephen Young reproduced in the minutes of evidence before the
HLSC, at pages 110-111.
49
50
Minutes of evidence taken before the HLSC, 16 October 2001, paragraphs 594-650.
Letter dated 10 November 2005 from Rob Lingham, Assistant Director of the Directorate of Air Staff, MOD to Lord
Jacobs
51
Letter dated 10 November 2005 from Rob Lingham, Assistant Director of the Directorate of Air Staff, MOD to Lord
Jacobs
52
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It is accepted that the cause of the crash cannot be ascertained. However, it is
noteworthy that the AAIB inspector reported that he could not confirm the pre-impact
serviceability of the aircraft and that the few facts available are consistent with a
technical failure having been the cause.
53

Flight control malfunction : Undemanded Flight Control Movement (UFCM)
There are several possible causes of a UFCM, none of which can be eliminated on
the basis of the AAIB findings on the wreckage. Any one could have caused or
contributed to the crash.
The MOD has always maintained that ZD576 was under the full control of the
pilots prior to the crash. They cite the waypoint change as evidence that the
pilots were in control at that point. However, re-setting the waypoint on the Super
TANS navigation system is analogous to putting on the indicator of a car : it
merely denotes the intention to change direction, not the ability to do so. The
waypoint change does nothing to prove the serviceability of the engines, engine
control, flight control or other systems.
54
A UFCM is consistent with the impact attitude of ZD576. In their second
simulation , (not seen by the BOI), Boeing admitted that they were unable to
correlate the impact attitude, particularly in roll and yaw, with the control
positions. They drew attention to the highly unusual position of the left rudder
pedal. This is consistent with a control malfunction. (See p.13, paragraph 3.3, last
sub-para.
55
A UFCM sufficient to be the sole cause of the crash but leaving no trace is not a
fanciful hypothesis. Just such a malfunction occurred in a US Army Chinook
which rolled over through 360° in flight at about 1,100 feet and righted itself at
250 feet.
The US Accident Investigation Board were unable to confirm a
malfunction of any of the systems associated with the flying controls. There was
no suggestion of error or negligence on the part of the pilots - who survived to
describe the incident. After many months of intensive investigation by the US
Board and by Boeing, no definite cause was ever found for the incident but it was
postulated that there could have been contamination of the hydraulic fluid from
chrome-plated aluminium end caps on the servo-cylinders of the upper boost
actuators.
56
Possible causes of a UFCM include:
Upper Boost Actuator blockage : contamination of hydraulic fluid in the flight
control system
Fine slivers of metal were found by the AAIB in one of the servoscreens of the yaw
Integrated Lower Control Actuator. Although the AAIB concluded that they had not
contributed to the accident they had only been able to examine a small sample of
hydraulic fluid, most of which had been lost. There is no evidence that there had
not been contamination of hydraulic fluid in other parts of the system, for
53
Annex D
54
55
56
Flightfax December 1998 = Annex D RAS
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example in the upper boost actuators. Contrary to the Government’s assertions in
their response to the HofL Select Committee, a single upper boost actuator jam
could pose acute problems for the pilots. In his evidence to the HofL Select
Committee the AAIB inspector, Tony Cable, explained:
‘I should make it clear in answer to the Committee’s questions that an upper
boost actuator seizure would render the aircraft uncontrollable, or possibly
effectively disable all four channels of the flight control system. With one of
the actuators seized, a pilot controlled demand in one channel (pitch, roll,
yaw, thrust) would generally result in abnormal reaction of the affected
rotor disc and in most cases a response of the aircraft in other control
channel senses. Such a seizure could be caused by an anomaly in one half of
one of the four dual actuators, as the two halves of each actuator work in
parallel. I understand that a temporary upper boost actuator seizure was
responsible for the loss of control experienced by the United States Army CH47 Chinook mentioned during the Hearing.’
57
A sustained jam of even a few seconds would lead to a catastrophic loss of
control. Chinook crews were not taught to cope with this emergency in the
simulator and there was no advice in the emergencies section of the Flight
Reference Cards for the simple reason that, with a jam of this nature, the aircraft
is in an unrecoverable state.

Control jam : detachment of control panel inserts
Three weeks prior to the accident, Chinook ZD576 had suffered a partial control
jam caused by the detachment of a component in the ‘broom closet’. On this
occasion, the result amounted to no more than an unnatural ‘feel’ to the affected
control run (in this case, collective). The ‘broom closet’ is, however, a relatively
small space and it is entirely possible that the introduction of a loose article into
this critical area could have disastrous consequences. The following incident
illustrates how little of a disturbance is required to affect the flying controls in
this area:
Following a particular incident on a Chinook HC2, crews were advised that
large people should not be accommodated on the jump seat (which is
immediately adjacent to the broom closet) and that anyone on the jump seat
should be advised not to lean to their left (onto the broom closet cover). This
order resulted from some control runs in the broom closet being fouled simply
by pressure being applied to the cover.
It does not require a leap of imagination to consider the degree of fouling which
could result from relatively large, loose object inside this confined space. At best,
such fouling would be noticeable by the pilots and would restrict the rate and/or
the amount of control available to them. At worst, it would render one or more of
the control channels immovable.
57
HofL Select Committee, footnote 2, p. 110
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A year later, another HC2 suffered a similar incident. After the accident, the
method of attachment was described by the AAIB inspector as ‘less positive than
would normally be expected’ by the AAIB expert. He stated: ‘... the possibility that
inserts had detached prior to the accident could not be dismissed.’
58
In the wreckage detached parts were found within a vital unit of the flight control
system. It was not possible to establish whether detachment took place before or
on impact. Had detachment occurred in the air, flight control malfunction is
certain.
The Government Response claimed that in order to create a control jam capable of
causing the crash, it would be necessary to lose control in all axes simultaneously
and, further, that a control jam would have been detected well before the
waypoint change. Neither assertion was correct.
59
As described above, a jam in one particular axis, especially in yaw and roll, can
lead to loss of control in other axes. The Serious Fault Signal entry in the
Airworthiness Register relating to the detached balance-spring mounting bracket
in the collective channel of the flying controls of ZD576 on 10 May 1994, signed
by Group Captain Verdon states :
60
‘Detachment of the bracket within the flying control closet during flight
could present a serious flight safety hazard, with the danger of a detached
bracket fouling adjacent flying controls.’
On an accompanying Priority Action Message Form , Sqn Ldr Brough, the Senior
Engineering Officer of 7 Squadron, stated :
61
‘Emphasise that whilst symptom is stiff collective control the main flt safety
concern is the danger of a loose article within the flying control closet.’
A jam in the manual inputs would not necessarily have been detected prior to the
waypoint change: flying across the Irish Sea it would not have been necessary for
either pilot to have his hands or feet on the controls. A jam in yaw would have
been very unlikely to have been detected prior to the initiation of the turn at the
waypoint change. In a letter dated 8 April 2005 the MOD acknowledged that it
was quite possible for the helicopter to have been carrying a latent fault without it
being apparent to the pilots when they were flying straight and level and only
manifesting itself when they tried to turn:
62
‘(2). If at any point the Chinook had a latent control jam preventing the
helicopter from turning, but the helicopter were continuing on a straight
course, the aircrew may not have had any indication that there was a
problem. The problem would only become apparent when they tried to
instigate a change of course away from dead ahead.’
63
58
AAIB Technical Report (Annex Q to the Board of Inquiry Report) at paragraph 7.4.2.
59
Government Response of 22 July 2002, page 16, paragraph 10.
60
61
62
63
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
Engine malfunctions : FADEC problems
Problems with the FADEC (engine control system) fitted to the Chinook HC2 were
well-documented over a long period. The history is set out in the report of the
Committee on Public Accounts. The RAF’s own test establishment had refused to
certify it (see Interim CA Release below and Annex [ ]). A FADEC-induced engine
malfunction would demand immediate attention. A FADEC-induced run-away up
could most certainly have caused an inadvertent or uncontrolled climb into cloud,
compounding the difficulty of the pilots’ task of regaining control.
64
There is substantial evidence which points to the possibility of an engine
malfunction and none to contradict it. A run-away up or a run-away down would
require immediate attention; it could cause a temporary and partial loss of
control. This scenario is entirely compatible with a forced entry into cloud and
with the delay in initiating the emergency climb.
There is no material evidence available from the wreckage to substantiate or
contradict this scenario. The AAIB report concluded that the engines were working
normally up to the point of impact. However, from Boeing’s second simulation it is
clear that it is impossible to tell what the engines were doing. A software
aberration would not be expected to leave evidence.

Other possible mechanical failures
A number of other mechanical problems were identified by the AAIB inspector,
none of which can be eliminated on the facts. ZD576 had already had several
mechanical failures since its introduction into service less than two months prior
to the crash.
65
66
Irrespective of whether doubts or alternative factors appear more, equally or less
likely than a theory which attributes sole or main causation to human failings, they
must necessarily be completely discounted before a finding can be made with
“absolutely no doubt whatsoever” that a dead pilot was to blame. The standard of
proof for negligence on the part of deceased personnel is very high. The burden of
meeting the high standard of proof is on those who seek to apply or sustain a
negligence finding. It is absurd, and contrary to Air Force guidance for a finding of
negligence against a dead pilot to be deemed fair or reasonable on the basis that the
dead pilot has failed to exonerate himself by providing a more likely explanation for
the accident than his negligence: negligence can only be found if there is “absolutely
no doubt whatsoever”.
64
65
66
Letter Rob Lingham, Assistant Director, Directorate of Air Staff, MOD to Lord Jacobs 8 April 2005 (Annex D)
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Additional evidence not considered by the Board of Inquiry :
problems and the CA Release history
Procurement
These issues are addressed in detail in Annex F.
Certain significant evidence was not available to, or not considered by the Board of
Inquiry or the Reviewing Officers. Had they done so, they could not have reached a
conclusion of gross negligence with absolutely no doubt whatsoever. Much of this
evidence relates to the procurement of the Chinook Mark 2 and the CA Release.
Contemporary documents show that the MOD’s own experts had serious concerns
about the introduction of the Chinook HC Mk2 into service, including concerns that
were manifestly flight safety critical.
The Board of Inquiry plainly did not consider any kind of engine malfunction to have
been a likely cause of the crash, but it equally plainly did not rule it out as a cause .
From its Report, the Board appears to have been aware in broad terms of pre-accident
concerns about engine malfunction on this type of aircraft. The only evidence relied
on however, is the written and oral evidence of the AAIB Accident Investigator Tony
Cable. Neither he, nor the Board relying on his evidence, were aware of the full
extent of the pre-accident concerns about the FADEC. They were unaware of the fact
that A&AEE had suspended flight trials with the Chinook HC Mk2, and were also
unaware that the MOD had engaged in litigation against the manufacturer of the
FADEC because of persistent problems with it .
67
68
It is hard to imagine that the AAIB investigator and the Board of Inquiry would not
have at least entertained the possibility of an engine malfunction rather more
seriously than they appear to have done, had they known of these facts at the time.
The Board saw, and exhibited to its Report, evidence from the A&AEE at Boscombe
Down relating to electromagnetic interference. It even saw and exhibited to its
Report Section R of the CA Release concerning icing restrictions on the Chinook HC
Mk2. In relation to possible engine malfunction however, it either did not see, or
failed adequately to take into account the history of serious concerns expressed by
A&AEE at Boscombe Down, both leading up to, and subsequent to the CA Release for
the aircraft.
The CA Release Recommendations of November 1993 provided essential conditions
to be applied ‘should operational use of the aircraft become necessary ...’ and imposed
a limit on altitude because of icing problems and a weight restriction so that the
aircraft could be flown on one engine. These limitations still applied when ZD576
crashed. A&AEE’s advice was that:
‘9.3 If either engine’s control system automatically changes to Reversionary
control, the aircraft must be landed as soon as possible.
9.4 If either engine exhibits unusual or unexplained behaviour ... the
aircraft must be landed as soon as possible.’
67
Board of Inquiry Report paragraph 35(d)
When examined by the HofLSC in September 2001, Wing Commander Pulford, the President of the Board of Inquiry,
stated that he had not known that the MOD was suing the manufacturer
68
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These requirements alone should have precluded any use of the Chinook HC2 for
long over water flights where the ability to land as soon as possible could not be met
(the aircraft was not cleared for a water landing except in an emergency (Section V)).
The routing to Inverness had to be along the coast and up the Great Glen because of
the icing limitation, i.e. had to be VFR.
On 27 May 1994, a week before the crash, Flt Lt Tapper requested permission to keep
an extra HC1 in Northern Ireland because of the limited operational capabilities of the
HC2 due to its CA Release.
69
The interim CA Release of November 1993 also included the following warning:‘NOTE : Spurious Engine Fail caption warnings Pending manufacturers
investigations and a remedial solution, the “Eng Fail” caption may illuminate
spuriously on the Caution Advisory Panel (CAP), with a corresponding
illumination of the master caution light. The pilot must immediately verify
the status of the engine by a scan of engine instruments. If all indications
are normal the master caution light may be reset. If engine operation is
normal aircrew should expect the “Eng Fail” light to extinguish after a 12
second lapse time.’
Boscombe Down suspended flight trials of the Chinook MK2 for 5 weeks from 7 March
1994 following an engine flame-out caused by something other than a software fault.
On 1 June 1994, the day before the crash, Boscombe Down again suspended flight
trials, which were not resumed until November. The reason for the suspension was
not just the problems with FADEC but was the occurrence of
70
‘... at least 15 engine related incidents in a total of 1258 flying hours ... 4
are considered to have particularly serious implications’
All four of these incidents related to in-service aircraft. One incident was on ZD576
itself two weeks before the accident when the PTIT of the No 1 engine reached 950° C
[cross-reference].
Instead of investigating the fault properly, the detachment
maintenance staff swapped the gauges and the problem appeared to be fixed until it
recurred during the morning sortie on the day of the crash. From entry into service
on 8 April to the crash on 2 June 1994, at least 10 mechanical problems were
documented for ZD576. Clearly this raises serious doubt about the airworthiness of
ZD576. The memo went on to state:
‘Furthermore, we strongly recommend that you make our concerns known to
the RAF in order that they may consider their own position.’
71
On the day of the accident, and before it had occurred, the Officer Commanding
Rotary Wing Squadron at A&AEE wrote to the Chinook Project Manager in the
Procurement Executive :
72
‘6. RWTS has carefully monitored the progress of this trial [of FADEC] and
has put tremendous effort into ensuring that it progresses safely to provide
timely CA Release recommendations. Those recommendations with respect
69
Evidence of Sqdn Ldr Prowse to BOI; Recorded Evidence Statements, p.23
70
71
A&AEE memo 6 June 1994
72
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to FADEC have, to date, been ignored. Until RWTS is provided with a clear,
unequivocal and realistic explanation of the faults ... further Chinook HC2
flying shall not be authorized ...
7. ... A&AEE has always been keenly aware of the risks associated with
operating the Chinook HC2 and has tailored sortie profiles accordingly.
Crews of the RAF have no such luxury and are likely at higher risk than
A&AEE crews. As such, RWTS deem it imperative that, in the strongest
possible terms, the RAF should be provided with a recommendation to cease
Chinook HC2 operations.’
In 1990 the MOD commenced legal action against Boeing and against Textron
Lycoming in respect of an engine overrun caused by a defect in the FADEC system
during testing in January 1989. The claim against Textron Lycoming, as set out in a
letter from the British Defence Staff Washington DC to Textron Lycoming dated 16
March 1990 , was as follows:
73
‘ ... the FADEC system ... failed to provide required overspeed protection and,
as a result, caused one of the aircraft’s FADEC-equipped engines to overrun
during ground tests conducted by Boeing Helicopters on 20 January 1989,
severely damaging the aircraft ...
The losses “were the direct result of ... the failure of Textron ... to use due
care in the design and testing of FADEC.’
In 1995 the case settled at arbitration with damages of $3m being paid to the MOD.
When examined in the House of Commons Defence Committee in March 1998, John
Reid stated:
‘We did not sue them [Boeing and Textron] because of a failure of the FADEC
software. This is one of the misconceptions that has been unfortunately
allowed to flourish. So there was a case, the Board of Inquiry were aware of
the case, but the case was essentially against Boeing and Textron Lycoming
for negligence in their testing procedures, not against the software. I hope
that is a full answer and I hope that clarifies things.’
74
He stated that the litigation was not regarded as highly relevant to the Fatal Accident
Inquiry.
Mr Malcolm Perks was an expert witness for the MOD in the litigation against Textron
Lycoming in 1993-95. He confirmed in written evidence to the HofLSC that:
‘The case put forward during the Arbitration hearing was that Textron
Lycoming had failed to use due care in the design, development and test of
the Chinook FADEC.’
75
Perks commented on John Reid’s evidence:
73
74
75
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‘I found the Minister’s statement a strange one: he was actually using one of
the arguments advanced by Textron Lycoming in their defence against the
MOD’s case - that it was ‘only’ an issue of testing. It was also Textron
Lycoming’s view that Boeing Helicopters were responsible for that test but
since MOD had previously settled with Boeing that issue had already been
taken out of the equation. Had I been an MOD advisor to the Minister, I
would not have recommended defending MOD’s position in this way.
Perhaps the Minister was confused as to which case was being discussed as,
in my opinion, if that really had been the sole case against Textron
Lycoming, it is unlikely the case could have been won.’
The Airworthiness Chain
The Board of Inquiry’s Terms of Reference did not specifically task the Board to look
at whether the Chinook fleet or ZD576 as an individual aircraft were airworthy at the
time of the accident – this despite the fact that the problems of the Chinook HC2 fleet
at that time were well known to supervisors and commanders and there had been a
number of technical problems with ZD576 prior to the crash.
76
The way in which the airworthiness of an aircraft and its systems is determined is
reviewed in Annex H. Some of the issues, including procurement and release to
service, have already been raised but additional issues include the quality of the
Boeing conversion, the maintenance of the aircraft and the documentation such as
the Flight Manual and the Flight Reference Cards (FRC) which were recognised as
being defective. In particular, the FRCs for a number of emergency drills were poorly
laid out and confusing . This, combined with the limited training the crew had had
on the HC2 could have affected the crew’s ability to deal with an emergency. The
Board of Inquiry did not question the officers in the immediate airworthiness chain
even though maintenance activities had taken place on more than one occasion
without proper documentation.
77
78
Overall Conclusion
Many of the arguments in this case have been rehearsed a number of times. Positions
may have in the past become entrenched, and the debate affected by political
partisanship and/or personal rancour. With the passage of time, perhaps it is now
possible to take a new and level-headed look and to consider simply whether or not
the proper procedure was followed and whether, in all the circumstances it is fair for
the findings of gross negligence on the part of the pilots to stand.
It is our belief that, for the reasons set out above, and in the accompanying Annexes,
the finding of gross negligence on the part of the deceased pilots ought not to stand.
We accept that the opinions leading to the findings were given in good faith, but
submit that the findings were fundamentally incorrect. In the best interests of the
Royal Air Force (RAF), in the interests of fairness and justice, as well as in the
interests of the pilots and their families, the findings should be overturned. We see
no reason why this should not be very easily achieved in one of two ways, either:
76
Annex G
77
Witness statement of Squadron Leader D.T. Morgan to BOI
78
Royal Aeronautical Society p.3 and Annex C10 and [other refs]
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(1) by a public statement from the Secretary of State for Defence, confirming the
MOD’s acceptance of the findings of the original Board of Inquiry, but stating that, on
detailed review of the evidence now available, the opinions of the Reviewing Officers
were incorrect and the findings of negligence do not stand; or
(2) by subjecting all of the evidence now available to the statutory processes laid
down for the investigation of aircraft accidents and amending the findings of the
original Board of Inquiry accordingly.
Arnold & Porter (UK) LLP
Michael Powers Q.C.
October 5, 2007
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INDEX TO ANNEXES & APPENDICES
Annex A:
Statutory Requirements
Annex B:
Representations regarding standard of proof in relation to
negligence and Board of Inquiry findings
Annex C:
The Reviewing Officers’ Hypotheses
Annex D:
Findings of the Air Accident Investigation Branch
Annex E:
Alternative Causation Factors :
Upper boost actuator jam
Control jam : detachment of control pallet inserts
Annex F:
The Controller Aircraft (“CA”) Release for the Chinook HC Mk 2
Annex G: ZD576 Defect Signals and Work Orders
Incident Signals for Other HC Mk2
Annex H:
The Airworthiness Chain
OTHER PUBLIC BODIES
Annex I:
The Fatal Accident Inquiry
Annex J:
The Royal Aeronautical Society
Annex K:
The Committee on Public Accounts
Annex L:
The House of Lords Select Committee
Glossary
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