Select Committee on Chinook ZD 576 Report


CHINOOK ZD 576

PART 4: ANALYSIS OF FINDINGS AND CONCLUSIONS OF THE BOARD OF INQUIRY

Evidence to the Board

62.  The Board heard the evidence of 22 witnesses and also had before it a considerable number of statements from witnesses taken by the Strathclyde Police and the Royal Ulster Constabulary. Most of the former related to weather conditions and events in the vicinity of the points of impact while the latter described the coasting out of the aircraft from Northern Ireland.

Weather

63.  The state of the weather was crucial to the conclusions of the investigating board and of the two Air Marshals. Two witnesses gave oral evidence to the Board as to weather. First Mr Murchie, a keeper at the lighthouse, spoke of visibility there being some 15-20 metres, but 400-500 metres to the north. The Board asked him no further questions about weather. The second was Mr Holbrook, the yachtsman, whose initial statement to the Strathclyde Police contained an expression of opinion "that the helicopter pilot would have been in a position to clearly see the local land mass". In his statement to the Board Mr Holbrook said that the aircraft was well below cloud level and visibility was about a mile limited by haze. At the time he was about two nautical miles south west of the lighthouse. He was asked three questions by the Board of which one was relevant to weather, namely whether he could see the physical features of the cliff on the Mull. To this he replied "no".

64.  When he gave evidence at the FAI Mr Holbrook expressed the opinion that the pilot could have seen "the location of the Mull lighthouse" and described the low cloud as "hugging the Mull" (Sheriff's determination, p 110 of HL Paper 25(ii)). He was criticised by the Ministry of Defence for having given different versions of his account to the Board and the FAI. In these circumstances we invited him to give evidence, an invitation which he willingly accepted.

65.  Mr Holbrook's evidence to us began with a statement which he had asked leave to make (Q 594). He explained that the low cloud clung to the contours of the high ground so that the location of the Mull massif itself was not in doubt from sea level. He considered that the crew of the aircraft when he saw it could determine without ambiguity where the Mull was and could see the cliffs, beach and lower perimeter walls of the lighthouse complex.

66.  Mr Holbrook reaffirmed that when he saw the aircraft he could not see the physical features of the Mull but he went on to explain that he was able to see the location of the lighthouse complex because the buildings and the white perimeter wall showed up as a colour change against the background of the land mass (QQ 594, 602). The top of the lighthouse was in cloud as the cloud level moved up and down (Q 606). Mr Holbrook went on to explain that the cloud was following the contours of the land and was very localised (Q 615). He also remarked, as he had done before the Board, that the helicopter was in sunlight as it passed (Q 619). At that time the aircraft was about two miles to the south west of the lighthouse. He expressed the opinion that the aircraft was flying at a height of between 200 and 400 ft and that the crew would have been better able to see the position of the lighthouse than he was at sea level with a certain amount of spray (QQ 610-13). He estimated the speed of the aircraft to be 60-80 knots but did not feel confident enough to be dogmatic as he had not previously seen a Chinook in flight. However, it was his impression that the aircraft was travelling sufficiently slowly to be involved in a search and rescue operation (Q 639).

67.  We do not consider that Mr Holbrook changed his evidence between his appearances before the Board and the FAI, rather that when he was subjected to professional examination and cross-examination at the FAI and to our questioning he was able to expand upon the rather brief evidence which he had given to the Board. We had no hesitation in accepting him as a reliable and convincing witness.

68.  In his statement to the police and in his evidence to us Mr Holbrook referred to the fact that the trawlers round which he was manoeuvring appeared to be Scottish as one of them had St Andrew's cross painted on the superstructure (Q 630). When Wing Commander (now Group Captain) Pulford gave evidence to us he was asked whether the Board sought evidence from any of the fishing vessels referred to by Mr Holbrook. He replied that they had tracked down the fishing vessels to Northern Ireland and the RUC could neither find anybody who had seen the aircraft nor trace some of the boats (Q 11).

69.  It is perhaps surprising in view of Mr Holbrook's statement to the Strathclyde Police about the trawler with St Andrew's cross on the superstructure that that force were not asked to pursue the matter. It is perhaps even more surprising that the Board asked Mr Holbrook only one question in relation to weather and used the answer as a component in the construction of a theory as to the probable course adopted by the pilots.

70.  Mr Holbrook explained to us that he had repeatedly but unsuccessfully asked to see photographs of a Chinook at different heights and ranges, in order the better to estimate the height and speed of the aircraft when he saw it. He clearly felt that he would have been in a better position to assist the Board had he been furnished with such information. We do not know why the Board did not accede to his request or afford him the opportunity of seeing a Chinook in flight.

71.  The statements taken by Strathclyde Police which dealt with weather were all from persons on the Mull at or above the height of the lighthouse and did not therefore throw light on the extent to which the land mass could be seen from an aircraft approaching from seaward. These persons all spoke of being enveloped in cloud to a greater or lesser degree.

Technical malfunctions

72.  The investigating board referred to "unforeseen malfunctions" experienced by Chinook Mk 2s in RAF service, "mainly associated with the engine control system, including undemanded engine shut down, engine run up, spurious engine failure captions, and misleading and confusing cockpit indications". They found no evidence that any of these malfunctions had occurred on the aircraft's last flight. Their report however continued, "Nevertheless, an unforeseen technical malfunction of the type being experienced on the Chinook HC 2, which would not necessarily have left any physical evidence, remained a possibility, and could not be discounted" (para 35(d)). They went on to state that while technical failure was unlikely to have been the direct cause of the accident such a malfunction "could have provided a distraction to the crew". In our view a serious control jam or UFCM could provide the crew with a rather bigger problem than a mere distraction.

73.  The board expressed the view that pre-impact detachment of an attachment bracket from the control pallets was "highly unlikely". They gave no reasons for thus going further than the conclusions of the AAIB (see above, para 57; and Mr Cable Q 1022).

74.  The board's reference to the unforeseen malfunctions experienced by Chinook Mk 2s (see above) simply repeated the second half of an answer given by Squadron Leader Morgan to the following question by the board: "What unforeseen malfunctions have occurred on the Chinook HC2 since its introduction to service?" The first half of the answer was in the following terms: "The unforeseen malfunctions on the Chinook HC2 of a flight critical nature have mainly been associated with the engine control system FADEC." This answer was not followed up and indeed appears to be the only evidence relevant to previous malfunctions given by any of the witnesses before the board. Group Captain Pulford and Squadron Leader Cole, the engineering member of the investigating board, were no doubt aware of the more general problems arising in Chinook Mk 2s at the time (QQ 64-5).

75.  The board again referred to the fact that "the HC2 has experienced a number of unforeseen technical occurrences since its introduction into service", and said that the possibility of the crew being distracted by a technical fault, major or minor, which left no trace "could not be dismissed" and "could have been a contributory factor in the accident" (para 46(c)). However they rejected this as a probable cause.

Conclusion of the investigating board

76.  After arriving at three scenarios unconnected with technical malfunctions, which could have been the cause of the accident, the investigating board concluded that the most probable was "the selection of an inappropriate rate of climb to overfly the Mull of Kintyre safely" (paras 59-60). In reaching this conclusion the board placed much reliance on the results of the Boeing simulation as to the final cyclic flare during the 4 seconds preceding the initial impact and the airspeed of 150 knots with a ROC of 1000 feet per minute prior thereto - a speed and ROC which have been shown to us to be incompatible (see below, paras 126-8). The board also considered that it was "most unlikely" that when the way point was changed the crew had seen the lighthouse or the Mull close to it (para 51).

77.  In considering the position of the crew the board said, "although it is likely that Flight Lieutenant Tapper made an Error of Judgment 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" (para 67(c)). The board concluded that "there were no human failings with respect to Flight Lieutenant Cook".

78.  The board found no evidence that either MALM Forbes or Sergeant Hardie would have been in a position to affect the conduct of the flight as it approached the Mull (para 66). The board did not comment on the very close relationship which existed between each member of a Special Forces crew; the Sheriff went into this issue in some detail.[26] Nor did the board comment on the fact that MALM Forbes's body had been found in the forward fuselage section (AAIB statement para 5.11) - a position which suggests that he had been in the forward part of the cabin, probably by the right hand front door, where he would in all probability have been checking the navigation and therefore aware of the aircraft's course and proximity to land.

79.  In view of the considerable number of problems which had beset Chinook Mk 2s since their entry into service - problems of which the investigating board appear to have been aware - it is perhaps surprising that they were able to dismiss so readily any such problems as having a significant effect in the accident.

Remarks of senior officers on the investigating board's findings

80.  In his brief remarks the Station Commander at RAF Aldergrove, Group Captain R E Wedge, stated among other things,

81.  The Station Commander at RAF Odiham, Group Captain (now Air Commodore, retired) Peter Crawford, rejected the investigating board's conclusion that the most probable cause of the accident was selection of an inappropriate rate of climb. He explained that when approaching high ground in bad weather the appropriate action was ingrained in helicopter crews. They should (1) slow down and if necessary stop, (2) turn away from high ground and if necessary turn back, and (3) if a climb was required do so on a safe heading at full power at the maximum rate of climb to at least safety altitude.

82.  He went on to express the belief that the crew had seen the Mull, which prompted them to make the way point change, and had intended to follow the western coast of the Mull. His cogent argument for that belief was stated in these terms:

    "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. Firstly, it removed from them the only easily interpretable information about the location of the high ground. Secondly, it was of little practical value; the crew would not have been able to climb to SA on track to Corran, in the hope of reverting to low level VFR, because of the forecast level of the 4°C isotherm. If they intended to climb over the Mull the only sensible option would have been to keep the lighthouse WP on until well clear of it and then to select the chosen diversion airfield. On the other hand, selection of the Corran WP was entirely appropriate if the intention was to follow the western coast of the Mull Peninsula and regain the planned track at the first convenient opportunity. In arriving at this alternative scenario I am now faced with the same problem that faced the Board - how did the aircraft get to around 500 ft, at 150 kts IAS with a ROC of approximately 1,000 ft per minute, which are the computed starting parameters of the final 18 seconds of flight?"

83.  The Group Captain later in his remarks referred to the fact that at the time of the accident spurious engine fail captions lasting an average of 7-8 seconds were an increasingly frequent occurrence and were not well understood. In his conclusions he stated that the reason why the crew flew the aircraft into the ground was "open to conjecture" and that in the absence of firm evidence there was not much to be gained by "speculating on the actions that led to the last few seconds of flight", although he expressed the opinion that the aircraft was under control when it was flared shortly before impact - an opinion based apparently on the Boeing simulation. He stated that "there is sufficient evidence to conclude that … there was no major technical failure that would have an implication for the Chinook fleet". In evidence before us he accepted that this was a matter of judgment on his part (Q 884). He expressed the view that, while there might arguably be some mitigating circumstances, Flight Lieutenant Tapper as captain of the aircraft had failed in "his overriding duty to ensure the safety of the aircraft". This did not amount to a finding of negligence (Q 902).

84.  The Air Officer Commanding No.1 Group, Air Vice Marshal J R Day (now Air Chief Marshal Sir John Day), remarked that "when the aircraft crashed, it was flying at high speed, well below Safety Altitude in cloud (in Instrument Meteorological Conditions) in direct contravention of the rules for flight under either Visual Flight Rules [VFR] or Instrument Flight Rules [IFR]". He further stated,

    "On approaching the deteriorating weather near the Mull, they had two choices. If they intended and were able to maintain flight under Visual Flight Rules, they should have slowed down, turned away or turned back. If they planned to continue their flight under Instrument Flight Rules, they should have climbed to above Safety Altitude well before they approached the Mull. If they were forced to transition to Instrument Flight Rules because they inadvertently entered cloud when close to the Mull, they should have made a rapid climb to at least Safety Altitude at maximum power and best climbing speed, while also turning away from the Mull."

85.  The Air Vice Marshal concluded that both pilots were "negligent to a gross degree". He commented that it was "incomprehensible why two trusted, experienced and skilled pilots should … have flown a serviceable aircraft into cloud covered high ground".

86.  The Air Officer Commanding in Chief Strike Command, Air Chief Marshal Sir William Wratten, remarked,

    "Lamentably, all the evidence points towards them having ignored one of the most basic tenets of airmanship, which is never to attempt to fly visually below safety altitude unless the weather conditions are unambiguously suitable for operating under Visual Flight Rules."

87.  Therefore he agreed with the summary and verdict of the Air Vice Marshal. Neither of the Air Marshals referred to the change of way point shortly before the accident, nor commented on Group Captain Crawford's reasoning in relation to it. Both Air Marshals at this stage appear to have proceeded on the basis that

    (a)  the pilots never saw the Mull,

    (b)  no technical failure or malfunction occurred which deprived the pilots of control up to the point of impact, and

    (c)  the Boeing simulation provided a reasonably accurate demonstration of the aircraft's movements for a period prior to impact.


26  
Determination pp 102-5 of HL Paper 25(ii). Back


 
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