Select Committee on Chinook ZD 576 Supplementary Memoranda


MULL OF KINTYRE

  1.  This paper represents a critical analysis of the various scenarios put forward by the Cook/Tapper families to cast doubt upon the verdict of Gross Negligence.

SITUATION AT WAY POINT CHANGE

  2.  Even our sternest critics agree that the crew would not have made the three button presses on the Super TANS to change to Way Point B if the Chinook had, at that point, been suffering from a major emergency. The key aspect, therefore, is the weather in the vicinity of the Mull of Kintyre at the time of the crash.

WEATHER AT THE MULL OF KINTYRE AT THE TIME OF THE ACCIDENT

  3.  All 10 eyewitnesses on the Mull of Kintyre reported the weather as being generally foggy and very bad. Nine of these eyewitnesses specifically gave evidence to the Board of Inquiry about the weather conditions at the time of the crash. A summary of their evidence to the Board of Inquiry, relating specifically to the weather conditions at the time of the crash, is as follows:

    —  Mr Murchie, lighthouse keeper: "I would estimate the visibility at this stage to be 15 to 20 metres at the most. . . . There were areas of better visibility to the north, in the order of about 4-500 metres although the fog was very patchy".

    —  Mrs Lamont, wife of lighthouse keeper: "As we looked up the hill all we could see through the dense fog was thick dark blue smoke rolling down the hill towards us".

    —  Mr Brocher: "The weather was really bad at this time, there was a lot of mist and fog, visibility was only about 10 to 15 feet . . . I could not see it (the Chinook) for the mist and fog".

    —  Mr Lamont, lighthouse keeper: ". . . the visibility, as I drove over the hill from Campbeltown to the lighthouse, was down to only about 10 metres or less . . . I suddenly heard the sound of a helicopter directly behind me, so close, I thought it was going to hit me, although I never saw it".

    —  Mrs Murchie, wife of lighthouse keeper: ". . . went outside to see the helicopter but because of the dense fog we couldn't see it at all. We could hear that it was very, very close and was flying low". She also added: "I couldn't see anything at all because of the fog, but I could see blue, thick, dark smoke rolling down the hill towards us".

    —  Mr Gresswell: "The weather conditions en route to the Mull of Kintyre were that of very dense fog. At the top of the hill it was drizzling and there was very thick mist . . . it was a lot clearer at the bottom (of the road; ie at the lighthouse). It was still drizzling and there was dense fog. At the bottom visibility was definitely clearer than at the top. However, it was still poor and was still misty".

    —  Mrs Crabtree: "The weather was really bad, we couldn't see the hills on either side of us because of the thick mist. . . . As we were walking I heard a helicopter. . . . I don't know how they saw anything at all".

    —  Mr Crabtree: "I was surprised at first that there was a helicopter up in that weather and it seemed very low. I didn't see it because it was up in the mist".

    —  Mr Ellacott: "I then heard the sound of a propeller going around for about four or five seconds and then I heard an explosion . . . Visibility at this time was only about nine or 10 feet maximum". "It was difficult to say how far I was from the point of the explosion, but I don't think I could have been any more than 100 yards".

  All nine of the above eyewitnesses heard or felt the Chinook crash. It is, therefore, almost certain that their recollections of the weather are specifically linked to the time of the crash. In particular, the lighthouse keeper's evidence (Mr Murchie) is particularly relevant as he would have been used to meteorological observations.

  4.  On the other hand, Mr Holbrook (the yachtsman) gave significantly different weather evidence to the Board of Inquiry and to the Fatal Accident Inquiry. He told the Board of Inquiry that, when, some two nautical miles south west of the lighthouse he had seen the Chinook fly past his yacht, the weather was as follows: "The visibility was about one mile and limited by haze". In spite of this evidence to the Board of Inquiry, he told the Fatal Accident Inquiry, some 19 months after the Chinook crash, that the weather and aircraft speed were significantly different. He told the Fatal Accident Inquiry: "I recall the conditions of visibility at sea level as being fine, perhaps as much as five miles. I think at that point I could even see the Antrim coast so it might have been as much as six or seven miles".

  5.  Of all the witnesses in the vicinity of the Mull of Kintyre at the time of the accident, Mr Holbrook is alone (if his evidence to the Fatal Accident Inquiry is to be believed) in saying that the weather was not foggy. He was of course at sea level whilst the nine eyewitnesses on the Mull of Kintyre were some hundreds of feet up the mountain and thus above the cloud base. It is also significant that, of all the witnesses who reported on the weather conditions, Mr Holbrook is the only one who did not know until much later that the Chinook had crashed. Therefore, his linkage of weather and time will not be as accurate as those who heard the Chinook crash near to them.

  6.  Based on his evidence to the Fatal Accident Inquiry, it is therefore feasible that, at the time of the crash, Mr Holbrook could see the cliffs below the lighthouse and maybe even the lower portion of the lighthouse. It is also perfectly possible that he could at times during the afternoon and early evening have seen the entire lighthouse, as the cloud base was obviously moving up and down during the course of the day. However, it is an indisputable fact that, at the time of the crash, the visibility at the lighthouse was about 15-20 metres as reported in evidence to the Board of Inquiry by Mr Murchie, the lighthouse keeper.

  7.  This means that the pilots of the Chinook could not possibly have seen the top of the lighthouse as they approached from the south, because it was engulfed by thick fog with a visibility of 15-20 metres. It was possible that, a few minutes before or after the crash, the fog may not have been as dense or even that the cloud base may have lifted to above the level of the lighthouse; however, at the time of the Chinook's approach and when it crashed, Mr Murchie's evidence of visibility is indisputable. It is also clear from the other eyewitnesses on the Mull of Kintyre that the cloud (or fog) extended well up the mountain.

VISIBILITY FROM THE CHINOOK COCKPIT

  8.  RAF Visual Flight Rules require the crew to have a minimum visibility of 1 km. We now know that their actual track was to the right of their planned track. With a visibility of only 1 km, they would have therefore seen the cliffs, at the latest, at the point marked on the attached map (Annex A). Giving the crew the benefit of the doubt with regard to groundspeed[2], this means that they flew on for over 500 metres before making the Way Point change to proceed to Corran.

  9.  If they could see the cliffs at a range of 1 km, I am convinced that no reasonable pilot would have then flown straight on towards the rapidly rising high ground before intending to turn left along the line of the cliffs whilst remaining below the cloud base. If this was their intention, they should have started to reduce speed and turn left between sighting the cliffs and making the Way Point change. We know that they did not do this.

  10.  If, on the other hand, they sighted the cliffs at 1 km range and intentionally decided to proceed straight ahead and cruise climb on track over the mountain, the pilots' actions would have amounted to Recklessness, which is a more severe degree of negligence than Gross Negligence.

  11.  It is much more likely that, by the time of the Way Point change, they had already started their cruise climb and were no longer complying with Visual Flight Rules. This more likely scenario is underpinned by the cross-sectional diagram at Annex B; the only other possible scenario being that they could see the cliffs at 1 km range as described in paragraphs 9 and 10 above. This diagram uses exact known facts where they are available and, in other cases, uses well proven approximations, or gives the crew the benefit of the doubt. For example, impact at 810 ft is a known fact. Cruise climb at 1,000 ft/min is a well proven approximation based on both the Boeing simulation of the flare and the fact that a Chinook at that weight and speed (135 kts Indicated Air Speed) can only achieve a maximum rate of climb of 1,100 ft/min. Similarly, the 665 ft height at the beginning of the flare assumes a 145 ft height gain (Boeing Simulation diagrams at Annex X to the Board of Inquiry Proceedings refer). The 21.5 seconds to Impact for the Way Point change assumes that the ground speed was only 160 kts (135 kts Indicated Air Speed plus 25 kts tailwind component), rather than the worst case groundspeed of 175 kts, which would give only 19.6 seconds to Impact.

  12.  This diagram shows that climbing at 1,000 ft/min the Chinook must have been at a height of at least 373 ft, and possibly higher, when the pilots made the Way Point change. Even at the maximum cruise climb rate of 1,100 ft/min, the Chinook must have been at a height of at least 344 ft. This is still approximately 50 ft above the height of the lighthouse, which we know, at the time of the crash, was in fog (ie cloud) from the lighthouse keeper's evidence to the Board of Inquiry. We also know from the evidence of the other witnesses in the area at the time of the crash that the fog (cloud) extended up the mountain to well above the height at which the Chinook crashed.

  13.  The analysis above conclusively shows that, whatever the precise weather conditions at the time when the pilots made the Way Point change, they were grossly negligent at that point in time. Temporary, major aircraft malfunctions after the time of the Way Point change are, therefore, irrelevant to the finding of Gross Negligence.

TEMPORARY CONTROL RESTRICTION

  14.  There is no evidence of a temporary control restriction; however, it has been postulated as occurring coincidentally with the Way Point change and then clearing at some four seconds to impact when the pilot flared the aircraft. It is just not credible that, faced with such a situation and imminent death, the pilots would not have pulled Emergency Power in an attempt to maximise their Rate of Climb and applied as much rudder as they could in an attempt to yaw the aircraft away from the rising ground (which was predominantly on their right). We know that they did not pull Emergency Power as the Emergency Power flags had not been tripped; this would have occurred five seconds after maximum permissible power had been exceeded. We also know that they had not tried to apply the maximum possible amount of left rudder because the aircraft did not crash with any appreciable amount of side slip. The very high Collective position found in the wreckage is entirely consistent with the emergency flare being initiated just before impact. Emergency Power was probably pulled in the flare, but there was less than five seconds to impact so it did not have sufficient time to activate the Emergency Power captions. Similarly, the 77 per cent left rudder found in the wreckage is consistent with either a desperate attempt in the last four seconds to yaw the aircraft or an involuntary rudder pedal movement during the crash.

  15.  It therefore follows that a temporary control restriction could not have contributed to the crash, notwithstanding the fact that the pilot's gross negligence occurred at, or before, the Way Point change.

FADEC INDUCED ENGINE RUNAWAY

  16.  A FADEC induced engine runaway has also been postulated as a possible cause of the accident. As with the suggested temporary control restriction, this hypothetical scenario ignores the fact that the pilots had already placed themselves and their passengers in an unacceptably dangerous situation at the Way Point change, from which safe recovery was virtually impossible without immediate decisive action to carry out an emergency pull up and turn away from the high ground. If an engine runs away up, the other engine automatically runs down to compensate. If the runaway up is not severe, the two engines will remain in an unbalanced state with one at a higher power setting than the other. If the runaway up is severe, the rotor head may accelerate to 115 per cent before the higher powered engine (the one that has runaway up) is automatically "tripped" and decelerates to a low power setting (flight idle). As the rotor RPM reduces to 100 per cent, the other engine (which will have slowed down to compensate for the excessive power being generated by the engine which has runaway up) will accelerate to a high power setting in an attempt to keep the rotor RPM at 100 per cent. Thus, in a situation where an engine had runaway up, the two engines would not have been at matched power settings at impact, as found by the AAIB Inspector during the physical examination of them. It therefore follows from this analysis that an engine runaway could not have contributed to the accident, notwithstanding the fact that the pilots' Gross Negligence occurred at, or before, the Way Point change.

Air Chief Marshal Sir John Day


2   Groundspeed of 160 kts (135 kts Indicated Air Speed plus 25 kts tail wind component), rather than the higher groundspeed of 175 kts which was also a possibility. Back


 
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