(a)  Counsel for the Ministry of Defence submitted that the accident was caused by a selection of an inappropriate rate of climb over the Mull of Kintyre which was insufficient to secure adequate terrain clearance on the track being flown by ZD576. The arguments in support of this submission were based upon certain essential facts which it was said had been established, and to which I shall return, and thereafter on the evidence of H, and it may assist towards an understanding of the issues to rehearse those parts of his evidence where he dealt with them (and, as already noted and for reasons which I hope will become apparent, I should emphasise that it has not been established to my satisfaction that the opinions as to the cause of the accident expressed by H in what follows in this subsection (a) are well-founded).

  H was asked first about the route which the crew of ZD576 were proposing to follow after reaching waypoint A. He replied: "It is my opinion, looking at that line on that route, they would be aiming to pick up the visual reference of the Mull of Kintyre and then turn left leaving the ground, if you like the coast to their right, and follow the general track of the Mull of Kintyre to the north". He was then asked why the crew might have selected a rate of climb of 1,000 feet per minute as the aircraft approached the land mass of the Mull of Kintyre, and he replied: "In my opinion that would suggest they had changed their plan and were no longer attempting to remain visual . . . Q.—Please elaborate on that for me because it is important? A.—The waypoint change at the position that it occurred is in my opinion significant and you must then analyse, in my opinion why they changed that waypoint. We have already discussed that the logical thing would have been they had seen the lighthouse or seen the Mull of Kintyre. In my opinion if that wasn't the case and in the weather conditions which I believe were extant at that time, I would have expected to see the aircraft slow down or certainly be at a reasonably low speed to be at a low height. We then go into it, if it happened you were climbing at that stage, then they obviously in my opinion had changed their plan . . . Q.—Do you mean by that they hadn't actually seen the lighthouse? A.—I believe, it is my opinion they had not visually sighted either the lighthouse or the Mull of Kintyre. Q.—Why in that event would there have been a change to waypoint B on the SuperTANS? A.—I believe that at that stage they had decided to climb into IFR and that in order to provide themselves with steering information for initially the next stage of their route they had changed the waypoint to the next one on their route. Q.—If that is correct, if they were planning to change to Instrument Flight Rules, presumably they were doing so for a reason; is that right? A.—Correct. Q.—There is no reason to suppose it would be just a change for some whim, there must presumably have been a reason? A.—Yes. Q.—It may be obvious, but what would one conjecture to be the reason that they may have made such a change? A.—I believe there are various options. They may have decided that the weather conditions were no longer suitable to continue VFR in the circumstances and decided to climb. They may have inadvertently entered cloud and were forced to climb into IFR conditions. Q.—Obviously on that approach to the problem, taking the latter of these possibilities, that they may have inadvertently entered cloud, I presume from that that must have occurred before they select this climb rate. It follows logically I take it? A.—Indeed. Q.—That means they inadvertently were entering cloud a relatively small, but some distance from the land mass of the Mull of Kintyre peninsula; is that right? A.—Correct. Q.—The only other alternative, as I understand it, is that they just realised that perhaps the weather ahead of them is not suitable; is that right? A.—Correct. Q.—Presumably not suitable because of visibility; is that the most obvious? A.—The cloud base, a combination of both. Q.—Again with the benefit of hindsight that we have as to the actual forecast in that area; is that right? A.—Correct. Q.—If that is right, if that is correct, one of course would expect them to select a rate of climb sufficient for them to clear any known high ground or obstacle in the immediate area; is that right? A.—That is right. Q.—Which tragically as we know they did not do? A.—Correct. Q.—Is there in your opinion, your expert opinion, any available evidence in explanation for that? A.—If I can take you back perhaps to the two options that we have, as to why they may have decided or may have found themselves in cloud, in my opinion if they had inadvertently entered cloud at that time prior to the waypoint change their proximity to the Mull of Kintyre would have been readily evident and they would have . . . Q.—Can I stop you there? What do you mean by "readily evident"? A.—Because it is most likely they would have still have had the TAC A steering information on the 252. Q.—I am sorry to interrupt you. Would you go on with what you were saying? A.—At that stage they would have carried out—I don't want to use the word "emergency"—but effectively they would have carried out actions to turn away and climb in a manner that would be expected of a crew inadvertently entering cloud that close to high ground. It is my opinion that that did not occur, which then leads on from the argument as to why they were suddenly in cloud and not climbing."

  H was then referred to Annexe AQ to the Board of Inquiry's report which was a copy of a 1:10,000 Ordnance Survey map of the area around the Mull of Kintyre lighthouse on which various positions had been marked by H and one of his colleagues on the Board. These positions corresponded, inter alia, to the position of the initial impact (point A), the position of the aircraft when the change of waypoint was made (point K), the true position of the lighthouse (point H), the position of the lighthouse which had been programmed into the SuperTANS (point G) and the most likely position at which the crew believed themselves to have been when the change of waypoint was made (point L). Point K was approximately 0.28 nautical miles (or 1,680 feet) south-west of the nearest land at Rubha na Lice. The distance from point K to point A was 0.95 nautical miles on a bearing of 022ºT (Taken from the Racal report) and the track KA was assessed as being the most likely track followed by the aircraft between the moment when the change of waypoint was made and the initial impact. Point L was shown as being 0.95 nautical miles from the true position of the lighthouse, again on a bearing of 022ºT. The track LH was said to be the possible closing track to the lighthouse assumed by the crew of the aircraft. It passed over the lighthouse and lay approximately 0.22 nautical miles (1,320 feet) to the west of, and parallel to, the track KA.

  In the course of considering my determination it appeared to me that point L on Annexe AQ had been plotted in the wrong place and that it should have been at a point (which I have called R on Annexe AQ) rather closer both to the lighthouse and to Rubha na Lice. I issued a Note to this effect on 17 February 1996[6] inviting parties to indicate whether on the one hand they were prepared to accept the accuracy of my calculations, or whether on the other hand they wished the inquiry reconvened to comment upon them. In short, the Crown, the Ministry of Defence and the representatives of the Tapper and Cook families responded that they were prepared to accept that an error had been made in the plotting of point L on Annexe AQ along the lines indicated in my Note. The representatives of the remaining families adopted what was in effect a neutral position on the matter. The response of the representatives of Boeing Helicopters was not entirely clear and their letter to the sheriff clerk ended with the observation that, if more was to be said about the implications of the proposed correction, then it appeared to them that it would be necessary to reconvene the inquiry to lead evidence on the issue. Given that the data upon the basis of which I was able to calculate where point L ought to have been plotted had been spoken to in the course of the inquiry, it was not clear to me what further evidence it was envisaged would have to be led on the matter. But since I was reluctant to reconvene the inquiry in these circumstances, and since it seemed to me that the apparent error in the plotting of point L would make next to no difference to my eventual decision, I decided to leave the issue to one side upon the basis that, wherever point L should have been, the crew must have known that the aircraft was heading on a track which would take it to the south and east of the lighthouse.

  H was asked about Annexe AQ as follows: "Q.—Looking over to where you indicate you believe it was most likely the crew believed themselves to be, . . . at point L, what consequences if any does that have in relation to the rate of climb and other decisions taken by the aircraft? Can you help me with that? Does it have any consequences? A.—It, of course, reduces the distance available before coasting, ie if you look at the distance between Kilo and the coast and Lima and the coast you will see these lines are different by about one kilometre in range . . . Q.—. . . That is one difference: is there any other difference or not that makes to the decision that one might take? A.—It is my belief—and again I must go back to my beliefs and where they have come from—I believe there is a possibility that that displacement to the east (sic—I think this should be west) of the actual position, albeit a small displacement, coupled with the general orientation of the Mull of Kintyre may have led to a mindset with the crew that the Mull of Kintyre was to their right and not directly in front of them." At that stage H was shown two maps (Figures 1 and 2) appended to the AAIB Report[7] and asked: "Q.—In essentially Figure 1 first of all one sees conveniently the whole situation showing the Mull of Kintyre and the crash site point and then in the close up (ie Figure 2) one sees the terrain in the vicinity of the accident site. Now, what is it you mean about mindset? It may be obvious but can you elaborate on that? A.—If you like, it is the angle of the approach that the aircraft was taking in terms of track over the water with the general orientation of the Mull of Kintyre. Q.—That might be misleading in some way? A.—I believe it is possible that you could get mindset which in your thought processes are to your right and not directly in front of you. Q.—And as you say, partly as a consequence of these relatively small navigational differences, is that right? A.—That is correct. Well, I believe that the mindset is there regardless because of that acute approach angle with the general orientation of the Mull of Kintyre, that the error to the right merely compounds that fact. Q.—I understand. Where then, if I can ask you this, does the mindset begin? Is it right at the planning stage? A.—Yes, I believe it is. Q.—You believe it is right at the planning stage. When one brings these maps out you have the feeling you are going up the west side of the Mull of Kintyre and it is essentially to your right? A.—That is correct. Q.—What happens when you actually fly with this error is that the Mull is in fact not as in that mindset but is directly ahead of you? A.—Yes, that is correct, but I must stress that I believe that offsetting error, the error there, is very small. It merely compounds what may already have been in the mind . . . I must state that this is a 1:10,000 map. Errors both in their mind plot or their acceptance of the accuracy of their plot plus the errors in the computer systems, both the Doppler and the GPS, are extremely small and therefore the parallel offset which I think is some 400 metres when I measured it is small. Q.—But it is compounding? A.—It is in the right sense, ie it is placing them closer to the Mull of Kintyre than would have been the case if they had been on track. Q.—And if they had the mindset that you have described . . . what consequences do you believe it would have in relation to the flying of the aircraft in the circumstances that you have envisaged as one approaches the Mull? A.—I believe it may have led to the crew believing that their ability to overfly, to climb safely and overfly the Mull, that they were being perhaps too optimistic, ie they had perhaps failed to appreciate the immediacy of the Mull. Q.—Now, is that simply a reference to the kilometre's distance you are talking about or is it more to do with the feeling that they are in fact in the mindset that it is going to go west of the Mull? A.—It is a factor in their thought processes which I think is a possibility. Q.—If that were the case, would it explain why a rate of climb was not selected to overfly the Mull? A.—I don't believe that it is the major factor in the selection of the rate of climb if one accepts as I believe, that they did decide to climb under IFR. It is a contributory factor in their thought processes during that period".

  In their report the Board of Inquiry concluded at the end of the day that there were three scenarios which could have caused the accident. H was asked about these: "Q.—. . . There were considered by the Board, I appreciate, different scenarios. Paragraph A was considering the possibility that a suitable rate of climb was determined but not flown, is that right? A.—That is correct. Q.—Would you read the Board's Report first of all in that regard . . .? A.—"Suitable rate of climb determined but not flown. In considering the case where the crew had decided upon a suitable rate of climb but did not achieve it, the Board felt that the time interval between the waypoint change and the final flare, although short, afforded the crew the opportunity to make some attempt to avoid ground impact earlier than they did. Although plausible reasons exist for their failure or inability to do so, it is the opinion of the Board that this scenario is less likely than the other two". Q.—Now, I wonder if I could just follow that through. Was there really anything to indicate that there was any reason why the aircraft should not have achieved a rate of climb that had been chosen? Is there really anything to support that proposition? A.—I believe not. Q.—Thank you. Next was considered the idea of "No decision" is the way it is put and can you read that? A.—"No decision. The possibility that the crew had arrived at no positive decision by the time of the final flare appeared to be contradicted by the existence of a rate of climb prior to it, and the Board therefore concluded that this possibility was less likely than the scenario where the crew selected an inappropriate rate of climb for the circumstances". Q.—Again, and I should emphasise this, this approaches it on the basis that there had been a rate of climb prior to the final flare, is that right? A.—That is right . . . Q.—And the last alternative which we were discussing, perhaps you can read the report in that regard . . .? A.—"Having considered the three alternative scenarios, the Board concluded that the selection of an inappropriate rate of climb for the circumstances was the most probable cause of the accident". Q.—And in that do I take it that is your personal view? A.—That is correct."

  On the question of how the crew could have come to select an inappropriate rate of climb H had this to say: "Q.—What puzzles me is even if they didn't see the Mull, how could they not have known firstly by the SuperTANS and secondly by the fact they had been flying for 10 minutes across the North Channel that they were within close proximity to the Mull? A.—I believe they knew that they were in close proximity to it. We discussed one of the aspects this morning, this idea in their minds as to where it was. I think my own personal belief is that they were seduced by their high groundspeed on an aircraft which was flying some 20 to 25 knots faster than they would have been accustomed to. Coupled with that high airspeed would be a high power requirement, leaving a reduced margin between that cruise power and climb power for the flight".

  H was asked about this again the following day with particular reference to the captain of the aircraft: "Q.—Well . . . he has got a SuperTANS, which tells him precisely where he is at any moment along that track between Belfast and the Mull of Kintyre lighthouse? A.—Correct. Q.—And specifically, at the moment he alters the SuperTANS to display waypoint B rather than waypoint A he knows the distance and the bearing to the lighthouse, doesn't he? A—Correct. But of course it is not to the lighthouse; it is to a point to the east of the lighthouse. Q—It is a point 200 yards to the east of the lighthouse? A.—Which he thinks is the lighthouse. Q.—Which he thinks is the lighthouse. He then decides he wants to climb, and he still knows the speed at which he is going over the ground, he knows the speed at which he is going through the air, and he has got an instrument which tells him the rate of climb. That is all correct, isn't it? A.—That is all correct, yes. Q.—And he has got a horizontal situation indicator which tells him the direction he is going in? A.—Correct. Q.—And he has got a map which tells him there is a hill 1,465 feet ahead of him? A.—Correct. Q.—As a layman, it seems to me it must have been obvious to him at the moment he switched to waypoint B that he was going to go into the hill. Am I wrong? A.—I believe he did not appreciate that because he had failed to appreciate his very small gradient of climb with the high airspeed and tailwind component, plus the limited power available during that climb. It is the failure to carry out that particular computation we have just gone through that I believe led to the accident. Q.—I find it difficult at the moment to understand how he could have made that failure, partly because of all his experience as an airman—I am talking about the navigator now—and one would have thought that with all his experience in flying these things, plus the instrument which is telling him how fast he is climbing, that would have alerted him to the fact he was not going to get anywhere near high enough? A.—I agree. Q.—The difficulty I have with all that is that it seems to me to fly in the face of all we have heard about—again I am talking about the pilot, who seems to have been one of the most experienced and able pilots that you had in the RAF. Is there any way of reconciling the two? A.—I have lived with your concern, my Lord, for the last 18 months, and I go through the same process you are going through. All I can say is that if you take all the other possible options, it is my opinion that there are even less likely; and unfortunately, on your later point, if experience and capability prevented accidents, we would have less accidents".

  H was asked finally about these matters on the sixteenth day of the inquiry as follows: "Q.—So if we go back to the cyclic flare and we proceed on the hypothesis that you have suggested, that this indicated a sudden appreciation of their proximity to land which they had not had before that cyclic flare, can you just explain to us, and I think particularly to the court who have to consider this matter, how that could have arisen? I appreciate this relates to the point you were talking about earlier but I think we need some clarification about the mindset they had? A.—Right. It is my belief that having changed the waypoint and having lost that immediacy of information with regard to the waypoint, accepting they knew it was there, and having decided at that stage to change their plan and to climb, they had then failed to appreciate—this is the significant factor—they had failed to appreciate at their significant rate of travel over the ground, their significant groundspeed, and with the high power setting required, that with that airspeed the available power to normal significant maximum provided them with a rate of climb which was insufficient to provide a gradient of climb sufficient to overfly the Mull of Kintyre. Q.—I think it had been suggested there were instruments there which gave you an indication of what their rate of climb was? A.—Absolutely, and it is significant what those instruments were telling them is where their error was made. Yes, they had a vertical speed indicator . . . but what they had failed to appreciate is the significance of that relatively low rate of climb, ie in the region of 1,000 feet per minute, which normally would be of no significance, but coupled with a rate of closure to the Mull of Kintyre of three miles per minute provided a gradient of climb which fails to fly the aircraft over the Mull. Couple that with—of course, it is only a minor mindset, but the idea that the angle of approach to the Mull of Kintyre combined with these small errors to the right of the track as to where they thought they were may have led them to think the Mull of Kintyre was further to the right and further away from them than was actually the case".

  (b)  In light of the opinions expressed by H in the foregoing passages, it seems to me that five questions require to be considered:

(i)  Were the weather conditions encountered by ZD576 at the Mull of Kintyre such as to persuade the crew that they could no longer fly along their planned track to Corran at low level under VFR conditions?

  The rules for flying under VFR conditions differ according to whether an aircraft is being flown above or below 140 knots airspeed. Above 140 knots the requirements are that there should be a minimum cloud base of 500 feet, five kilometres visibility and 1,500 and 1,000 metres respectively horizontally and vertically clear of cloud. Below 140 knots the rules are that an aircraft should remain clear of cloud and in sight of land or sea and further that there should be a minimum cloud base of 250 feet and visibility of 1,000 metres. In light of these rules H was of the opinion that the weather encountered by ZD576 at the Mull of Kintyre would have prevented VFR flight in excess of 140 knots and possibly below 140 knots as well. As he put it, "the ability of the crew to maintain VFR below 140 knots would be marginal". He based his assessment of the weather, albeit in the context of whether or not the crew would have been in visual contact with the Mull of Kintyre when the change of waypoint was made, on a number of sources. Among these was the evidence of Mr Murchie and Mr Holbrook, and I have already considered what they had to say. He also had access to a video taken by some holiday-makers. This was not shown during the inquiry and so can be ignored for present purposes with the exception of photograph 14 in the inventory of photographs for the Cook family which appears to be a still taken from the video. In addition, H referred to having obtained information from various unnamed witnesses who were up on the hill or on the road to the lighthouse at the time of the accident, but he did not suggest that any of these had been able to see out to sea any more than Mr Murchie had. He mentioned having spoken to some Search and Rescue helicopter crews, but they did not give evidence to the inquiry either. And finally he had the Meteorological Office aftercast which recorded the visibility and cloud as follows:—"Visibility in hill fog and drizzle 10 to 100 metres; below main cloud base 100 to 2,000 metres (2,000 metres to 10 kilometres at sea level). The stratus cloud base would have been variable and diffuse, between 200 and 800 feet AMSL. Tops of stratus perhaps 1,500 to 2,000 feet. Layers of stratocumulus 6,000 to 10,000 feet in places and some altocumulus above 14,000 feet". In photograph 14 (which appears to have been taken near the base of the lighthouse) a small island can be seen offshore, which may be the island which can be seen off South Point on the 1:10,000 Ordnance Survey map. If that is correct, it would be approximately 500 metres from the position of the photographer which would correspond with the evidence of Mr Lamont as to this distance. It is not clear from the photograph how much further (if at all) it would have been possible at the time to see beyond the small island. The fact that ZD576 did not continue to fly at low level over the sea to the west of the Mull of Kintyre is certainly consistent with the view that the crew judged the weather there to be unsuitable for further VFR flight. But the evidence as a whole, and in particular that of Mr Holbrook taken in conjunction with the fact that the base of the lighthouse was 250 feet above sea level, in my opinion does not exclude the possibility that they may have considered the weather suitable for this purpose, at least at airspeeds below 140 knots. In other words, it cannot be said on the evidence that on reaching the Mull of Kintyre they had no option but to climb and proceed under IFR conditions if they wished to continue the sortie to Corran and Inverness.

(ii)  On reaching the Mull of Kintyre would the crew have been satisfied in light of the aircraft's icing clearance that an ascent to the required safety altitude of 2,800 feet was feasible?

  It was the opinion of the Board of Inquiry, which H confirmed in his evidence, that an IMC pull-up from low level flight to safety altitude over the Mull of Kintyre was possible in the weather conditions which prevailed at the time of the accident. Indeed, without going into detail, it is clear from the weather forecasts which were available to the crew, and to which reference has already been made, that they would have been entitled on the basis of those forecasts to expect that the aircraft could ascend to the safety altitude without infringing the icing clearance (namely +4ºC). Equally, it is clear from the aftercast that the aircraft would in fact have been able to ascend to safety altitude since the temperatures for heights above sea level were:

  It was on the basis of this information that H was able to agree when it was put to him: "Q.—So the fact of the matter is that the conditions prevailing at the time would have permitted an IMC pull-up; and not only that, but the crew had a reasonable expectation that that would be the case, on the basis of the forecast information? A.—That is correct".

  The aftercast indicates that the temperature and dewpoint "at and above" the crash site were both 9ºC. It is nowhere explicitly stated what the temperature at sea level was at the time. However, according to the AAIB Report the reported sea level ambient temperature was 9ºC. It appears that Mr Cable obtained this information from some source other than the Board of Inquiry. But it is not clear what that source was. When he read out this figure of 9ºC in examination in chief and when he referred again to the sea level temperature in cross-examination it was not suggested that the temperature might have been anything other than 9ºC. Moreover, H appears to have accepted that that was the temperature at sea level, and in all the circumstances it seems to me to be reasonable to proceed on the basis that that was indeed the case.

  The crew of ZD576 of course did not have the advantage of seeing the aftercast. And they would no doubt have been aware that meteorological experts are not always correct in their forecasts as indeed H was prepared to accept. On the other hand, the crew did have in the aircraft an outside air temperature (OAT) gauge and they would have known of the rule of thumb (which was not disputed) to the effect that the air temperature drops 2ºC for every 1,000 feet climbed. In the course of examination in chief K, who had previously been shown the aftercast, was asked about the application of this rule of thumb in practice: "Q.—So are you saying that the crew then have to simply rely on the 2ºC drop every 1,000 feet to establish, say, their icing clearance? A.—Yes, that is correct. Q.—And where would they take their temperature reading from? A.—It has to come from the only source available to them which is the outside air temperature gauge in the cockpit. Q.—So if one if flying in a safe manner which assumes I think the worst scenario, what would one assume or plan one's icing clearance to be with a surface temperature at apparently 9ºC? A.—If this was planning information which was available to them, which obviously it was not because it is an aftercast, then they would be limited to 2,500 feet because that is where they would believe the +4º isotherm to lie. Q.—But given this is an aftercast and presumably shows the information, the true information, that the aircraft would have noted at the time, is that the information that they have to work on, the 9ºC indicated? A.—At the time of planning they would be able to work on the forecasts which we have already seen were available to them in the planning room which I believed show a surface temperature of +12 so in that instance they would be able to plan on that accordingly and work out what height they could actually climb to for any given area. That all really does not matter in the final instance because the only thing that matters when it comes to deciding whether you have an IFR option is what you can actually see on the temperature gauge. If in planning I had for instance a 4,000 feet safety altitude because forecast temperature was +12 and subsequently got to that area and found the temperature to be +9 on the surface then obviously you have to work on what the aircraft gauge says rather than some Met man in Leuchars saying what the temperature might be in that area. Q.—So at the time of actually making the decision to go to a safe altitude you would take into account the actual temperature recorded at the height that one was and establish what a safe altitude would be? A.—That is correct . . ." K was asked again about this in cross-examination: "Q.—. . . If you are flying along at 500 feet and the indication of the temperature is 9º, surely that implies that the 4º isotherm would be up to 3,000 feet, adopting your rule of thumb? A.—No, it would be 2,500 feet. If it was 9º at sea level you would expect is to be 7º at 1,000 feet, you would expect it to be 5º at 2,000 feet and you would expect it to be 4º at 2,500 feet. Q.—Can I suggest that if you are in fact flying at 500 feet and it is 9º you might expect it to be 10º at sea level and 8º at 1,000 feet? A.—Possibly. Q.—And if it was 8º at 1,000 feet it would be 6º at 2,000 feet and 4º at 3,000 feet? A.—True." I then asked K: "Q.—In reality would you actually sail as close as that to the wind? A.—No. When flying at low level you would accept whatever temperature was showing on your OAT gauge as being the surface temperature, simply to save you from descending to your minimum authorised height simply to find out what the temperature was". The cross-examination continued: "Q.—So your position—and it may be different from other people's—is that if flying at 500 feet your indicated air temperature was 9º and you knew your safety altitude was 2,800 feet you would not have aborted IMC? A.—Perhaps 500 feet was a poor choice of height to try and illustrate this scenario. If we take the height the yachtsman is reported to have seen the aircraft at somewhere between 200 and 400, yes, I would take whatever temperature was showing on the OAT gauge as being the surface temperature, for the purpose of a rough rule of thumb, 2,000 feet . . . Q.—I am sorry to interrupt you, but I asked you whether at that level you would or would not have aborted IFR? A.—I would not".

  For my part, it seems to me that it would have been entirely reasonable in light of what K said that, as the aircraft approached the Mull of Kintyre at a height of between 200 and 400 feet above sea level as observed by Mr Holbrook, the crew should have assumed that the temperature at sea level would be the same as that shown on the aircraft's outside air temperature gauge. In this context too it should be borne in mind that Flt Lt Tapper would have been particularly conscious of the significance for himself personally of breaking the aircraft's icing clearance. Clearly the fact that the aircraft was climbing in the 20 seconds or so before the initial impact is consistent with the proposition that the crew had decided that the aircraft could be flown to safety altitude without infringing the icing clearance. But if that factor is left out of account I think that it would be reasonable to conclude that the crew would not have considered it feasible to climb to safety altitude in light of the information then available to them—especially if, as J indicated (and as appeared to be confirmed by a suggestion put by counsel for the Ministry of Defence to the Air Traffic Control Officer at Belfast), they would in fact have had to climb to a minimum of 3,000 feet to comply with the rules for IFR flight.

(iii)  Is it likely that the crew would have had the mindset attributed to them by H to the effect that the Mull of Kintyre was to their right and not directly in front of them and hence have underestimated the imminence of their landfall?

  I have already rehearsed the evidence which H gave in seeking to support his opinion that the crew did indeed have this mindset. As I understood this evidence, and the submissions based upon it of counsel for the Ministry of Defence, there were essentially five considerations which were supposed to have led the crew to this mindset. In the first place, it had apparently been their original intention upon reaching the lighthouse to pass it on its seaward side. In the second place, the position of the lighthouse had been programmed into the SuperTANS approximately 280 metres to the south-east of its true position with the result that any assessment by the crew of the position of the aircraft would have led them to believe that they were further to the west than they actually were. Thirdly, the fact that the aircraft was at point K on Annexe AQ at the change of waypoint whereas the crew believed they were at point L meant that the aircraft coasted in one kilometre sooner than they expected. Fourthly, there was the general orientation of the Mull of Kintyre and finally there was the aircraft's angle of approach to the land mass.

  It is in my opinion important in considering this question to bear in mind that the maps which were put to H to enable him to explain his opinion were not the same as those which the crew would have had with them in the aircraft on the sortie to Inverness. Figures 1 and 2 annexed to the AAIB Report were respectively a large-scale map of part of the West of Scotland and Northern Ireland and a smaller scale map of the southern tip of the Mull of Kintyre. Their scales are not given, but so far as I can judge they are 1:625,000 and 1:50,000 respectively. The larger map has almost no topographical details on it and on the smaller map the different heights above sea level are depicted by varying shades of grey. In addition of course, there was Annexe AQ itself which was a copy of a 1:10,000 Ordnance Survey map. The maps which the crew would have had with them were on a scale of 1:500,000 and 1:250,000. A 1:500,000 map was on display on a notice board in court during the inquiry and copies of the three sections of the 1:500,000 map which Flt Lt Tapper left with the operations clerk at RAF Aldergrove before departure of the flight for Inverness formed Exhibits 2, 3 and 4 to the Board of Inquiry's report. Another copy of a 1:500,000 map was lodged by counsel for Boeing Helicopters on the afternoon of the fourteenth day of the inquiry. A further 1:500,000 map, and also a 1:250,000 map, were lodged by the Crown on the ninth morning of the inquiry following a request by myself to see these. For the sake of completeness, I should also mention that in the course of his submissions counsel for the Ministry of Defence also referred to two coloured photographs which form Figures 3.1 and 3.2 annexed to the AAIB Report. Figure 3.1 shows an aerial view of the land mass of the Mull of Kintyre taken from the south-west roughly in line with the aircraft's angle of approach to the initial impact point. Figure 3.2 shows a general view, again taken from the air, of the land mass looking north. Clearly, there are a number of difficulties in the way of relying on these photographs. In the first place, they were evidently taken on a clear, sunny day while H's hypothesis pre-supposed that the aircraft flew towards the initial impact point in cloud and without ever having been in visual contact with the land mass. Secondly, there was no evidence that the crew of the aircraft had copies of these photographs with them on the flight, or indeed had ever seen them. And thirdly, in my experience photographs of landscapes, roads, buildings and the like commonly give entirely misleading impressions of distances, proportions, angles and other measurements and so have to be viewed with particular care.

  On the question whether or not the crew might have been misled by the general orientation of the southern part of the Mull of Kintyre into believing the land mass was to their right, there can in my opinion be only one answer. It is plain from the 1:500000 and 1:250000 maps that the coast of the Mull of Kintyre runs in a broadly northerly direction from Rubha na Lice for a distance of about 5nm deviating only about ½nm to the east as it does so. The lighthouse is situated at the southern end of this stretch of coast only a short distance from Rubha na Lice. The aircraft's track from Belfast to the lighthouse was approximately 020ºT and its track from the point where the waypoint was changed to the initial impact point was approximately 022ºT. So notwithstanding that their original plan may have been to leave the land mass to their right, there cannot in my opinion have been any doubt in the minds of the crew that the land mass of the Mull of Kintyre lay ahead of them so long as their course from Belfast remained unchanged or deviated to the east. It is true that it can be seen on the 1:500000 map (Figure 2) that the coast deviates a little to the east of north for about 1nm north of the lighthouse. But, even if the crew were able to detect this on the map they had with them, they cannot have supposed that they would be making a landfall over this stretch since before the waypoint change they would have known from the SuperTANS that the bearing to the lighthouse was the equivalent of 018ºT and they would also have known from the horizontal situation indicators that the aircraft was heading on a track which was the equivalent of 022ºT, that is to the south and east of the lighthouse

  On examining the 1:500000 map, and even more so the 1:250000 map, the crew would have observed not only the general orientation of the Mull of Kintyre in the region of the lighthouse but also the fact that there are several contour lines closely ranged beside each other near to the coast and that the contour lines delineating the highest ground are much more widely spaced. That would have indicated to them that the land rose steeply from the sea before levelling out around the summits of the principal hills overlooking that particular stretch of coast. They would also have observed that the summits of the two highest of these, Beinn na Lice and Cnoc Moy, are each only about 1nm from the coast. In theory it is no doubt true, and I dare say that the crew would have been aware of this, that if an aircraft approaches a line of high ground from a given point at a given groundspeed and at an acute angle it will have more time to attain the required height to overfly the high ground than if it approaches the same high ground from the same point and at the same speed but at a right angle. Indeed, with pencil and paper the exact difference in times could be worked out, but before this calculation could be done a number of factors would have to be known. One of these would be the precise position of the starting point, and clearly the closer that starting point was to the line of high ground the less the time difference would be between the two angles of approach.

  In the present case the Board of Inquiry in preparing Annexe AQ calculated that when the waypoint was changed the crew would have believed that they were at point L. For the reasons which I have indicated I think that, if they had thought about this question at all, they would have believed themselves to be at point R. But since this has not been accepted by all the parties, I am content for present purposes to leave this issue to one side. Plainly, if the crew knew precisely where they were and the precise configuration of the line of high ground ahead of them they would have been able to work out how much time they would have, and hence what speed and rate of climb would be required, to overfly that high ground. But there are in my view a number of weaknesses in this whole approach. In the first place, there was no evidence to suggest that the crew had any maps with them on a smaller scale than 1:250000, and certainly not a 1:10000 Ordnance Survey map. Accordingly, while they would have known that when the waypoint was changed the lighthouse was 0.81nm away on a bearing equivalent of 018ºT, it is most unlikely in practice (if for no other reason than that it cannot be easy, even with a very sharp pencil, to carry out precise geometrical calculations on a 1:250000 map folded on one's knees in the cockpit of a Chinook helicopter) that they either could or would have actually applied their minds to a calculation of their exact position at that point in time with a view to estimating the imminence of their landfall and the time available to them before they reached the line of high ground ahead. Secondly, since they did not have with them a convenient selection of photographs and small scale maps, they could only have had a very general idea in their minds along the lines which I have already indicated of the topography of the line of ground ahead of them so that, even if they knew exactly where they were at any given point in time, they would not know exactly how far they had to travel before they reached high ground. And thirdly, they would have known that they should treat the information that they were 0.81nm from the lighthouse on a bearing of 018ºT with a degree of circumspection for two reasons. In the first place, it would have been obvious that the precise position of the lighthouse had not been entered into the SuperTANS since the latitude selected was only to the nearest half minute and the longitude only to the nearest minute (in contrast to the co-ordinates for waypoints C and D). This the crew would have had to take into account in determining the extent to which they could rely on the SuperTANS to give them accurate details of their position in relation to the position of the lighthouse. And in the second pace it is plain from the evidence of both J and K that Flt Lt Tapper in particular had doubts about the reliability of the SuperTANS. Since he had shared these doubts with J and K it is very likely he would also have shared them with the members of his own crew even if they were not already aware of this matter. Moreover, these doubts appear to be amply justified by the terms of Section 0 of the CA Release for the Chinook MkII since in paragraph 2.1 it warns that the Doppler is subject to "degraded performance overwater" (which is confirmed by paragraph 2.4.3.3 of the Racal report) and in paragraph 2.2 that the accuracy of the GPS is "not guaranteed to any level" and that "for this reason SPS GPS should not be used as the sole navigation aid". It is known now of course that both the CPS and Doppler inputs were functioning with a remarkable degree of accuracy during the last flight of ZD576. It appears that the aircraft's TACAN, VOR and ADR were unlikely to have been relied upon by the crew at the time of the accident. The IFF/Transponder was found in mode 1 with the numbers 0000 selected and in mode 3A with the numbers 7760. So apart from the SuperTANS the only other methods of navigation available to the crew were maintaining visual references so far as possible and dead reckoning. H's hypothesis assumes that the crew had no visual contact with the lighthouse or the land mass close to it, and it is self-evident that dead reckoning could not be relied upon to tell the crew exactly where they were as they approached the Mull after crossing the North Channel. The crew were not to know at the time how very accurately the SuperTANS was working and at best they could cross-check its determination of their position by reference to their dead reckoning calculations. So while they would have had to assume that they were at least as close to the lighthouse and the land to their right as point L is, they would have had to allow for the fact that they might be even closer than point L to either or both of the lighthouse and the land mass when the waypoint was changed. In all these circumstances it seems to me that it is highly unlikely that the crew would have thought that they could safely assume that the land mass was more to their right than it was and/or that their land fall was not as imminent as in fact it was.

(iv)  Is it likely that the crew would have considered it appropriate to overfly the Mull of Kintyre at cruising speed?

  In considering this question it is perhaps helpful to consider first of all what height the aircraft had to reach as it flew towards and over the high ground on that particular section of the Mull of Kintyre. Plainly the ultimate aim was to reach safety altitude which at that particular point in the route was 2,800 feet. It certainly appeared from some of the evidence that that altitude would have had to have been reached before the aircraft coasted in. Thus C was asked by counsel for the Ministry of Defence: "Q.—Can I just go on to the question of procedures that you have been asked about for pull-up into cloud. I think (it was) suggested to you there may be circumstances in which you would not need to climb at maximum power? A.—Yes. Q.—Can I just be clear what knowledge you would have to have before you could safely adopt that procedure. First of all, you would need to know where you were? A.—That is correct. Q.—Secondly, if you are proceeding towards a land mass you would need to know the height of that land mass ahead of you? A.—That is correct. Q.—And, thirdly, if you intended to continue to proceed towards that land mass you would have to select a rate of climb that ensured that you got to the safety altitude before you got to that land mass (my emphasis)? A.—That again is correct. Q.—And if you are not in a position to know each of these three things what should you do? A.—You should adopt the maximum rate of climb possible to ensure that you get to the safety altitude. Q.—You are assuming then that if you are satisfied in your own mind that the maximum rate of climb would take you to the safety altitude before you got to the land mass (my emphasis) that would be appropriate course of action? A.—Yes." Likewise, H was asked by counsel for the remaining families: "Q.—Reverting to just a few basics that I want you to help me with: Instrument Flight Rules would require a safe altitude to be reached before the aircraft overflew the Mull? A.—Correct. Q.—I think we know from the map that the calculated safe altitude for that area of ground is 2,800 feet? A.—Indeed... Q.—as the crew approached the Mull the flight crew had a number of options open to them? A.—Correct. Q.—One was to slow down and turn away from the high ground; am I right? A.—Correct. Q.—If that was done it may have been possible for the flight to continue on Visual Flight Rules on a different course? A.—Correct. Q.—Would another option have been to slow down and proceed with caution ensuring that visual contact with the sea or land was maintained with sufficient visibility ahead? A.—Correct. Q.—In both these options slowing down is an obvious minimum precaution I would suggest? A.—Indeed. Q.—Alternatively I think you have told us that another option would have been to climb to a safe altitude before the Mull was reached (my emphasis)? A.—Indeed. A.—And then proceed on Instrument Flight Rules? A.—Correct. Q.—Plainly, the essence of this manoeuvre would be to achieve it before the high ground was reached (my emphasis). A.—Indeed. Q.—If that could not be done, or if there was any doubt about the matter, would it be your view that the aircraft should have slowed down and turned away from the high ground? A.—Correct. Q.—If however, there was any doubt as to which way to turn the only other option, am I right, was to slow down and gain height at the best possible climbing angle? A.—Yes." But this evidence was later apparently qualified to an extent by evidence which H gave in answer to counsel for Boeing Helicopters. He was asked: "Q.— . . . can we envisage a low level flight over the land at say 250 feet with a safety altitude of say 5,000 feet during which it is decided to alter the plan to climb through cloud to safety altitude to a safety height. Is that something that happens from time to time . . . Is the general picture of that something that may be done operationally? A.—Yes, from time to time. Q.—If in the area the safety altitude is 5,000 feet, and if an aircraft pulling up goes into IMC at 600 feet then technically at that moment it is flying IMC and it is on VFR and it is not at its safety altitude? A.—Correct. Q.—Of course, it is perfectly acceptable then the transition period can exist in order to allow the safety altitude to be gained. A.—Correct. Q.—Is it therefore acceptable that during that transition period the aircraft will be passing in IMC conditions and overland but not overland at safety altitude? A.—Correct. Q.—Looking at the flight of this aircraft, do I take it then from the moment when the aircraft began to climb from about 400 feet or whatever somewhere south of the Mull of Kintyre it was from that point of view in the transitional stage? A.—Correct. Q.—And that would be transitional up to the safety height, whatever that was? A.—Correct. Q.—And at any point during that transition then it would be as a clear matter of fact and logic not at its safety height? A.—Correct."

  It was on the basis of this evidence that counsel for Boeing Helicopters submitted that it was acceptable for an aircraft to be in IMC passing over land or sea during the transition stage but below its safety altitude, and it was said that as ZD576 climbed from about 468 feet somewhere south of the Mull of Kintyre it was in this transitional stage. For my part, I am prepared to accept that it was not necessary for the aircraft to have reached safety altitude before it coasted in over the Mull of Kintyre. But it does not follow that it would have been acceptable for the aircraft to have, for example, climbed at a leisurely rate and in the process skimmed by a narrow margin over the western shoulder of Beinn na Lice so long as it reached safety altitude by the time it reached the area of Cnoc Moy (which I have to say is what counsel for the Ministry of Defence seemed to come close to suggesting at one point in his submissions). Thus H was asked by the advocate depute: "Q.—In your opinion from what you know, would it have been possible to select an appropriate rate to overfly the Mull from the point that they seemed to have made the decision? A.—I believe it would certainly have been possible to have safely overflown, ie not to have hit the Mull. The question of whether or not they would have been able to achieve 1,000 feet above the Mull of Kintyre, which of course they were required to do within their rules and regulations, is perhaps more questionable." And then he was asked by me: "Q.—Can you perhaps tell me this; if the position be that they thought they were at point L on this map AQ, do you see that? A.—Yes, point L. Q.—I think you called it Lima and they were on a course which then took them to point H which is the Mull of Kintyre lighthouse, if they had carried on in that course and climbing at the rate that they were climbing, would they still have hit the Mull or do you not know? A.—I believe....that they would not have hit the Mull. Q.—But they might have just missed it? I mean, it might have been a very narrow miss, would it not? A.—They would certainly not have been 1,000 feet above the Mull when they coasted in, that is correct". And the following day H was asked by counsel for Boeing Helicopters: "Q.—What they clearly did intend to do from your evidence is to climb above, overfly the Mull of Kintyre? A.—That is my opinion. Q.—Without looking for a moment at the details of what they did, as an option that was a perfectly acceptable option, isn't it? A.—To climb was a perfectly acceptable option had they ensured that in the climb they had a margin of 1,000 feet above the ground." Shortly afterwards he was asked: "Q.—Now, you were asked yesterday what would have been the result of the climb ....if it had been commenced at point Lima on Annexe AQ. Do you remember that question? A.—Yes, I do. Q.—I think you said you were not quite sure, but you thought the aircraft would have probably cleared the land, although you hadn't done the calculation? A.—Well, yes, I think we had done it at some stage. It may have cleared the land, but whether or not it would have cleared it by 1,000 feet is another matter". It appears to me that it is clear from this evidence that, even before ZD756 reached safety altitude, and while it was still in the transitional stage, the crew should have sought so far as possible to ensure that there would be a margin of at least 1,000 feet between the aircraft and any intervening ground over which it had to pass on the way to reaching safety altitude. And indeed it seems to me to be no more than a matter of elementary common sense that a pilot who is flying an aircraft from a low level at whatever angle of approach towards an area of rising ground which he cannot see because it is shrouded in cloud would want to leave a wide margin for error above ground level, and that a margin of 1,000 feet would be none too much for this purpose.

  Whether or not I am correct in this conclusion, it is I think important to bear in mind that any decision by the crew of ZD576 to overfly the Mull of Kintyre is most unlikely to have been made on the spur of the moment at or about the time when the waypoint was changed. On the contrary, it would have been the culmination of a process which began the evening before the flight when Flt Lt Tapper discussed the plan for the sortie with B and C. Even at that stage he was aware of the weather forecast for the following day, and at the crew briefing on the morning of the sortie attended by A the general weather situation was discussed. Later in the day up-to-date weather forecasts and TAFS were obtained by the crew. It is plain that at that stage they would have had to have been thinking about the high ground and other obstacles that lay ahead of them on their planned route and about what they would do in the event of encountering IMC. After setting off they flew over Northern Ireland and when the aircraft coasted out they would have been able to see that the Mull of Kintyre was shrouded in mist. As they flew across the North Channel they would have been able to observe the conditions ahead of them and would no doubt have been discussing as a crew how they would proceed in the event that further flight under VFR conditions proved impossible when they reached the Mull. The aircraft appears not to have begun to climb until the moment when the waypoint change was made or shortly before it. By that stage, according to H, the crew's "proximity to the Mull of Kintyre would have been readily evident" to them. Indeed they must have known that the land was not more than 1nm ahead of them (and could be a good deal closer), and bearing in mind that they were approaching at an acute angle they must have known too that the land would be even closer on their right than it was ahead of them. They also knew that the safety altitude required to overfly the Mull was 2,800 feet. I have already rehearsed in section IV(3) the evidence as to what the crew would have been expected to do in these circumstances to overfly the land mass in IMC, and in my opinion it is plain that, whether or not the aircraft's entry into IMC was planned, it would have been entirely contrary to the crew's training and experience to have elected to overfly the Mull at cruising speed starting from a point so close to the land and at a height of between 400 and 500 feet above sea level. As K put it, speaking of the navigator of the aircraft: "Certainly in high terrain like that in the vicinity he would not even think of employing a cruise climb technique". And even if, for example, Flt Lt Tapper had proposed such a course of action, I am quite sure in light of the evidence which has been rehearsed about the relationships among the crew that one or other or all of Flt Lt Cook, MALM Forbes and Sgt Hardie would have appreciated the obvious dangers of the proposal and would not have hesitated to point them out forcefully to Flt Lt Tapper.

(v)  On the assumption that the crew did decide to climb at cruising speed over the Mull of Kintyre how likely is it that they would have selected an inappropriate rate of climb to do so?

  In considering this question a number of factors require in my opinion to be taken into account. In the first place, the crew would have known that the aircraft was likely to be at least as close to the land mass as point L, and quite possibly closer, and heading towards it on a track which was approximately two degrees to the right of the planned track from RAF Aldergrove to the Mull, and this at a time when (as they must have expected from their pre-flight planning) the display on the SuperTANS was telling them to turn between 10 and 15 degrees to the left and indeed Flt Lt Tapper had apparently altered the course selector on his horizontal situation indicator with a view to the aircraft making a turn to the left. From their maps the crew would have gained an impression of the topography of the high ground ahead of them along the lines already indicated, and they would have known of the safety altitude that the aircraft would have to attain in order to overfly that high ground. They would have known too that they had chosen to embark upon a course of action which was entirely contrary to their training and experience. For these reasons alone they would I am sure all, individually and collectively, have been acutely aware of the importance of ensuring that a sufficient rate of climb had been selected and carried into effect.

  Moreover, as experienced operators the crew would have been aware that in a standard IMC pull-up the purpose of pulling the aircraft back to minimum power speed was to make maximum power available from the engines so as to achieve the greatest rate of climb compared with any other speed, and correspondingly that, the more the aircraft's airspeed exceeded minimum power speed, the less the power that would be available to enable it to climb. They would have known that for any given rate of climb the higher the aircraft's groundspeed the less would be its angle or gradient of climb. They had in the cockpit of the aircraft a variety of instruments which they would have been expected to have been monitoring and which would have told them the aircraft's groundspeed and airspeed, its rate of climb, its heading, its height above sea level and above ground level and the performance and power output of its engines. In particular, they would have known that they should check the vertical speed indicator to ascertain the aircraft's rate of climb. It is true that the aircraft's radar altimeters would have been operating in the narrow 200 to 500 feet range until a very late stage in the flight and that there would have been no warning from either instrument until it was too late to take effective evasive action since the low level warning cursors had been set at 850 and 69 feet respectively. It is possible too that these altimeters might have locked briefly as the aircraft closed with the ground. On the other hand the barometric altimeters would have given the crew an idea of the aircraft's rate of climb. And they would also have been able to determine from it their height above sea level at any given point in time. Since they knew the height of the ground ahead of them and the aircraft's speed over the ground and its rate of climb, it is hard to understand how they could possibly have thought that they would be anywhere near high enough to clear it by a safe margin.

  It is true that H pointed out the difficulty of establishing the aircraft's angle of ascent when he was asked: "Q.—I would have thought once you had been piloting these things for as many hours as they have, these pilots, they would know that when they were going at 150 knots and climbing at 1,000 feet per minute they would know very quickly that was a particular angle of ascent. That is not the experience you get? A.—Surprisingly not. The gradient changes with groundspeed and airspeed. It is such a dynamic equation". But while it may not have been possible for the crew accurately to establish the angle of ascent, they must in my opinion have known in general terms how slowly the aircraft would have been climbing. J was asked about this on three occasions, (1): "Q.—You mentioned the general procedure or manoeuvre in a situation for entering, changing from Visual Flight Rules into Instrument Flight Rules. Is there any reason why that procedure might be modified so that for example a steady and low rate of climb at cruising speed is initiated? A.—None whatsoever, particularly with quite a heavy Chinook. If you can't see ahead of you a heavy weight Chinook cruising speed scarcely climbs at all so you would certainly need to take another form of abort and when you had chosen to abort you would climb at low speed with a high rate of climb"; (2): "Q.—When you talk about a heavy Chinook at cruise speed are you referring to a Chinook weighing 18,000 kilograms or a higher weight at which it can now operate? A.—With 18,000 kilograms or above you would have quite a slow rate of climb at cruise speed. Q.—At cruise speed was the context you were talking about? A.—Certainly;" and (3): "Q.—In any event, you maintain that any concerns about the timing of the flight in relation to crew duty hours or anything of that sort should not have been sufficient to have diverted the crew from normal practice in the event of them losing Visual Flight Rules contact? A.—Certainly not. Q.—It would not have justified continuing at cruising speed? A.—No. Q.—Is that right? A.—If they could safely initiate the climb on coasting out from Northern Ireland they could probably climb at cruising speed but I don't believe they would attempt that with a flight profile with close obstruction because there is no way that aircraft could climb, initiate a climb, as late as it did at cruise speed. Q.—Just on that point, there is no doubt it was a, if not fully laden, pretty nearly fully laden aircraft, is that right? A.—It was within the 18 tonne constraint rather than the 22,700 I believe, yes. Q.—I take it that the crew would have been aware of the limited rate of climb that could be obtained by such an aircraft at cruising speed? A.—Yes, very much so". It is clear too that Flt Lt Tapper in particular was concerned about the aircraft's overall weight on the sortie to Inverness which is why he wanted the passengers to be weighed before boarding. K was asked about this under reference to the situation where an aircraft was travelling at a ground speed of 120 knots and at a rate of climb of 1,000 feet per minute. "Q.—Is there any room for the navigator to have been mistaken about the rate of climb in that situation do you think? A.—No. Even if the vertical speed indicator was stuck, jammed, showing the wrong rate of climb on the instrument, for whatever reason, he would still have an idea of his rate of climb from his groundspeed and the power setting of the aircraft, even if it was not particularly accurate. He would still know that a very high airspeed would not allow him a very high rate of climb, which is the reason why people do not cruise climb at 150 knots, they bring themselves back to 120 knots and cruise climb". It will be recalled in this context that immediately before the final cyclic flare the aircraft was travelling, for some unexplained reason, at an airspeed of approximately 150 knots which was significantly faster than the average airspeed for the whole of the leg between RAF Aldergrove and the Mull of Kintyre.

  H maintained that, after the change of waypoint, the aircraft would have been flying some 20 to 25 knots faster than the crew would have been accustomed to. Even if it be assumed that in general the difference in cruising speeds between the MkI and MkII Chinook helicopters was indeed as great as that, it is not clear to me upon what factual basis H felt able to make this particular comment. In the first place, it is known that some MkI Chinooks were capable of being flown at very high speeds without any marked vibration and H did not exclude the possibility that either Flt Lt Tapper or Flt Lt Cook might have flown in one of these aircraft. And secondly, and more to the point, it is clear that Flt Lt Cook at least must have had some experience in flying MkII Chinooks between the completion of his MkII conversion course on 18 March 1994 and 31 May 1994 since he was not out of currency when ZD576 was delivered to RAF Aldergrove by D and his colleagues, and indeed D was able to confirm that C had flown MkII Chinooks within the previous month. Flt Lt Tapper on the other hand was by then out of currency and it is not clear whether he had flown a MkII Chinook since completing his conversion course on 25 February 1994. But again the possibility cannot be excluded. At all events, in light of all the foregoing considerations it appears to me that it would have been very unlikely that the crew of ZD576 would have failed to select an appropriate rate of climb to overfly the Mull

  (c)  I have so far assumed that H was correct in concluding that the crew of ZD576 were not in visual contact with either the lighthouse or the land mass of the Mull at least until the moment before the control inputs were made to bring about the aircraft's final cyclic flare. Indeed it does not seem to me to matter very much whether this was so or not since, for reasons which I have already explained, the crew must have known that the aircraft was very close to the land mass even if they could not see it. So in my view their subsequent actions would have been the same whether they saw the land or not. H's reasons for concluding that the crew were not in visual contact with the Mull were based on his understanding of the weather conditions in light of the evidence of the aftercast and the various witnesses to whom I have referred in considering question (i) above, and also on his belief that, if the crew had been in visual contact with the Mull, the aircraft would have slowed down and descended to a lower height than that at which it was when the waypoint was changed. For my part, I doubt whether the evidence of any of the witnesses who were on the land can be relied upon to indicate what the visibility over the sea was like as the aircraft approached the coast. I have already considered Mr Holbrook's evidence and at the very least it appears from what he said that there would have been visibility at sea level of 2nm coupled with a higher cloud base there than over the land. The aftercast spoke of visibility of 100 to 2,000 metres below the main cloud base extending to 2,000 metres to 10 kilometres at sea level with, significantly, the cloud base being "variable and diffuse, between 200 and 800 feet AMSL". Annexe AQ demonstrates that at the time the waypoint was changed at point K the aircraft would have been a little over 0.8nm south of the lighthouse and about 0.28nm from Rubha na Lice. Thus, whatever the visibility and cloud base may have been at the lighthouse, it is perfectly possible that at point K the visibility might have been better, and the cloud base higher, so that the crew would have been able to see the coast in the vicinity of Rubha na Lice even if they could not see the lighthouse itself and even if the aircraft at that stage was as high as 400 to 500 feet above sea level. Indeed, even from the ground just to the south of the lighthouse building the visibility to the south was at least 500 metres as can be seen from photograph 14. It is true that upon seeing the coast and in the prevailing weather conditions the aircraft might have been expected to slow down and descend. But equally the reason that it did not apparently do so could be that the crew had seen the land ahead and to the right and, as I pointed out, at a height of 200 to 300 feet a speed of 155 knots would have been perfectly acceptable. J's view was that the change of waypoint indicated that the non-handling pilot had seen the waypoint and that certainly would have been consistent with the normal procedure whereby a change to a new waypoint would be made only when the first waypoint had been identified. In itself this is not perhaps a very strong point in favour of the conclusion that the crew had seen at least the coastline of the Mull. Of much greater significance in my opinion is that it appears extraordinary that an aircraft travelling at low level at a groundspeed in excess of 150 knots (or 2.5nm a minute) in the general direction of a land mass, which the crew knew to rise steeply from the coast to a height in excess of 1,400 feet within 1nm of the coast, should have got so close to it without the crew having seen it. As K put it: "I would not expect a crew at 0.8 of a nautical mile from a land mass at that altitude to be anything other than visual with the land mass. It is tantamount to suicide to be in that position and not be able to see the land mass". In the circumstances I consider that, while they may well not have seen any part of the lighthouse buildings, the crew probably did see the coastline at least around Rubha na Lice.

  (d)  Counsel for the Ministry of Defence, the remaining families and Boeing Helicopters all reminded me of H's comment to the effect that, if experience and capability prevented accidents, there would be less accidents. In very general terms I dare say that that may be true, and it would clearly be quite wrong to proceed on the basis that an aircraft accident can never be caused by pilot error. But equally it would be wrong to assume that any particular aircraft accident has been caused by pilot error especially when it is seen, as in the present case, how unlikely it is that there would have been such an error and, moreover, that any error that was made would have been one in which, by reason of their training and experience as Special Forces aircrew, the whole crew and not just the navigator would have been implicated. Counsel for the Ministry of Defence suggested that, if a person appeared before the court charged with reckless (sic) driving, the court would not entertain a defence to the effect that the accused was a competent and experienced driver and therefore could not have been driving recklessly. At the time this suggestion was made I commented that the difference between that scenario and the present case would be that there the accused would be able to explain himself whereas in the present case Flt Lt Tapper and Flt Lt Cook were not. In light of what was said by counsel for the remaining families, I recognise that the inability of the two pilots in this case to explain what happened during the last seconds of the aircraft's flight is not a factor that I am entitled to take into account. I recognise too that it would not be a defence to a charge of dangerous or careless driving to say that the accused had hitherto always been a competent and careful driver. On the other hand, if the accused were a middle-aged minister of the Kirk who was also a member of the Institute of Advanced Motorists with a clean driving licence and a record of no claims on his motor insurance policy extending back over 20 years, it would plainly be legitimate to take into account evidence to that effect in determining whether upon the whole of the evidence before the court the accused's guilt had been proved beyond reasonable doubt. That is why, if an accused person has no criminal record, it is common practice for that fact to be brought out in the course of the evidence. So too in the present case evidence which tends to show how unlikely an error on the part of the crew of ZD576 would have been can in my opinion be taken into account in determining whether, in light of all the evidence which has been led in the course of this inquiry, the cause of the accident was indeed that stated by H and the Board of Inquiry.

  (e)  The essential facts upon which was based the submission for the Ministry of Defence as to the cause of the accident may be shortly stated. When the aircraft was about 0.81nm from the lighthouse at the Mull of Kintyre on a bearing of 018ºT the waypoint in the SuperTANS was changed from waypoint A (the lighthouse) to waypoint B (Corran). That happened when the aircraft was between 400 and 500 feet or thereby above sea level. After the change of waypoint the aircraft flew towards the initial impact point on an ascending track of 022ºT. At a point some 15 to 18 seconds before the initial impact the aircraft was at a height of 468 plus or minus 50 feet above sea level. At a point in time about 2.9 seconds before the initial impact the aircraft was climbing at a rate of approximately 1,000 feet per minute and at an airspeed of approximately 150 knots. To that there fell to be added a tailwind component of approximately 24 knots which resulted in a groundspeed of approximately 174 knots. At that point in time large aft and left cyclic and collective control inputs were made in the aircraft which resulted in a final cyclic flare before the initial impact. During this final flare the aircraft travelled approximately 812 feet over the ground, increased its rate of climb to approximately 4,670 feet per minute and climbed approximately 128 feet. In addition the flight path angle increased to 20º above the horizontal and the nose of the aircraft was pitched up to about 31º above the horizontal.

  It was submitted that the obvious and natural inference to be drawn from these essential facts was that the crew of the aircraft had decided to carry out an IMC pull-up with a view to overflying the Mull of Kintyre at safety altitude and for that purpose had selected an inappropriate rate of climb with the result that they had been unaware of the proximity of the ground until 2.9 seconds before the initial impact when their attention had been drawn to it either visually or else by a warning being given by the low level cursor on the right hand pilot's radar altimeter (which it will be recalled had been set at 69 feet). It was then said that the crew, having been alerted to the proximity of the ground, had made large pitch and collective control inputs in the aircraft in a last desperate attempt to avoid contact with the ground resulting in the aircraft's final flare, but sadly to no avail. It was submitted that H had correctly identified the reasons for the crew's failure to select an appropriate rate of climb in the passages from his evidence which have already been quoted. It was pointed out in short that the inquiry had heard a great deal of positive evidence which excluded other possible causes of the accident apart from that postulated by H and the Board of Inquiry and it was submitted that I would require compelling reasons to discount H's conclusions given his experience, the fact that he and his colleagues had spent many months pursuing the most detailed investigations into the accident and the fact that he had himself clearly given the whole matter a great deal of anxious consideration before coming to the conclusion which he had.

  Leaving aside H's explanation of the reasons why the crew might have selected an inappropriate rate of climb, I accept that there is very considerable force in these submissions bearing in mind in particular the fact that the aircraft was climbing after the change of waypoint and the fact of the final cyclic flare having occurred only seconds before the initial impact. But the central question remains: How, if it be so, did it come about that such an experienced crew, fortified by a battery of instruments and gauges in the aircraft's cockpit, select an inappropriate rate of climb to overfly the Mull of Kintyre and, in so doing, remain unaware of the proximity of the ground below until it was too late to take successful evasive action? H's answer in short was that the crew failed to appreciate that the aircraft's high groundspeed coupled with the high power setting required to achieve this speed would provide an insufficient gradient of climb to overfly the Mull of Kintyre, and that it was this together with the crew's mindset that the land mass of the Mull was more to their right than it actually was which were responsible for the selection of an inappropriate rate of climb. I accept that this is a perfectly intelligible explanation and, coming as it does from H, it clearly deserves a great deal of respect. But at the end of the day the question has to be asked: Where is the evidence to support this particular interpretation of events? The truth of the matter in my view is that there is none apart from the essential facts which I have summarised above. And it seems to me to involve a distinctly speculative leap to proceed directly from those essential facts to the interpretation which H has sought to draw from them—and in fairness to H, I think he would probably have agreed with this assessment at least in relation to the supposed mindset of the crew. Moreover, the fact that many other possible causes of the accident have been excluded on the evidence and that all the other possible inferences that might be drawn from the essential facts appear, in H's words, "even less likely" does not mean H's conclusion must be taken to be correct. And since, as I have sought to explain, it appears from other evidence that there are compelling reasons, especially in subsections (b) (iii), (iv) and (v) above, for believing that this conclusion and the scenario upon which it is based are most unlikely to be correct, then I think that it may be understood why I have found myself unable to accept the conclusion reached by H and his colleagues on the Board of Inquiry. In short, it has not been established to my satisfaction, and on a balance of probabilities, that the cause of the accident was the decision by the crew of ZD576 to overfly the Mull of Kintyre at cruising speed and their selection for that purpose of an inappropriate rate of climb.

  It may be asked what was the cause of the accident. For my part, I can only say that I do not know. The Board of Inquiry investigated and excluded, or at least considered unlikely, a whole range of possibilities other than those already mentioned, including electro-magnetic interference, crew distraction and submarine activity. Against that background, and in the absence of any evidence from eye witnesses aboard the aircraft or of information that might have been recovered from a Cockpit Voice Recorder or an Accident Data Recorder, I do not think that any useful purpose would be served by my speculating further on the matter.

7   Printed in HL Paper 25 (i), pp. 70-71. Back