Old Ground
Catazou,
I see that the thread has started once again to go back over old ground.
Can I remind you what the Board actually said about the weather, crew duty time and the lack of an outbrief.
Weather
At para 42 the BoI commented:
42. Weather - The Board considered that the weather information available to the crew at RAF Aldergrove prior to flight was comprehensive and adequate for the task, and the Board was content that the crew had considered the weather relevant to their flight. The Board then considered the suitability of the forecast and actual weather for the VFR flight planned by the crew. The weather documentation faxed to the crew indicated that conditions entirely suitable for helicopter low level VFR flight would prevail over the greater portion of their route, but that over coastal areas there would be an occasional risk of less favourable but acceptable conditions, and an isolated risk of conditions sufficiently poor to preclude VFR flight. These indications were reflected in the associated TAFs and METARs. Along the crews planned route, these occasional and isolated conditions would only have been expected in the area of the Mull of Kintyre, with a specific risk of a 30% probability of weather below VFR limits being forecast for Machrihanish. In the opinion of the Board, a forecast of a 30% probability of en-route weather below VFR limits was not sufficient to preclude an attempt at a VFR flight (my underlining). However, a suitable bad weather contingency plan would have been required. This might have been a VFR diversion around the bad weather, a VFR return to the point of departure, or a pre-planned climb and conversion to IFR flight (my underlining). The possibility of a lightning strike affecting the aircraft was also considered by the Board, but as there were no reports of lightning activity in the area, and no evidence of a lightning strike was found in the technical investigation, it was discounted. Similarly, the Board also considered the part that turbulence may have played in the accident and, as the aftercast indicates that the turbulence in the area was only moderate, the Board concluded that it could have provided no more than a distraction to the crew, particularly when flying in IMC. However, as the actual weather in the area of the crash site at the time of the accident was very poor, with very low cloud bases and low visibilities, the Board concluded that weather was a contributory factor in the accident.
The weather also gets discussed in Stn Cdr Odihams’ alternative view of the accident - part of the BOI, which was:
An Alternative View
2. In looking for alternative causes I have no new evidence to call upon, and all I can do is put a different emphasis on factors already considered by the Board. By working “forward” from the departure point, I conclude it is highly probable that rather than electing to climb over the Mull the crew saw the coast and decided to continue VFR to the west of the Mull Peninsular. The evidence of the yachtsman who saw the aircraft about 2 -3 nm SW of the Mull gives a good idea of the weather and the aircraft’s height and attitude just before the crash. At about 17-30, only 30 minutes before the crash, the yachtsman then about ¾ mile from the Mull reported that the lighthouse and the cloud covering the land behind the lighthouse were clearly visible. Just before the accident the same man, now 2 to 3 miles from the Mull, reported that the aircraft was straight and level at a height of between 2-400 ft well below cloud level. He assessed cloud cover as 80% and the visibility as about 1nm, limited by haze. He also reported the cloud as structured which, in aircrew terminology may mean layered. After the aircraft passed the yachtsman any deductions about what happened become more speculative but I believe that given the reported weather, the crew saw the Mull and it was this sighting that prompted the Waypoint (WP) change at 1.75 km.
3. This WP change is crucial in trying to understand what the crew intended to do. If they had intended to abort at this stage and climb over the Mull despite the difficulty, which would have been so obvious to them, of clearing the high ground they would not have selected the Corran WP. Firstly, it removed from them the only easily interpretable information about the location of the high ground. Secondly, it was of little practical value; the crew would not have been able to climb to SA on track to Corran, in the hope of reverting to low level VFR, because of the forecast level of the 4ºC isotherm. If they intended to climb over the Mull then only sensible option would have been to keep the lighthouse WP on until well clear of it and then to select the chosen diversion airfield. On the other hand, selection of the Corran WP was entirely appropriate if the intention was to follow the western coast of the Mull Peninsular and regain the planned track at the first convenient opportunity. In arriving at this alternative scenario I am now faced with the same problem that faced the Board - how did the aircraft get to around 500 ft, at 150 kts IAS with a ROC of approx 1000ft per minute, which are the computed starting parameters of the final 18 seconds of flight?
4. Whilst tackling this issue the Board were unable to totally discount the following factors:
a. Spatial disorientation or visual illusion.
b. An unregistered technical malfunction.
c. Human factors.
Any of these, or a combination of them, could, in my view, have sufficiently distracted the crew from the task of turning away from the Mull to cause them both to inadvertently enter cloud and then to fail to take the correct procedure for an emergency climb in a timely manner. The Board consider engine control system malfunctions and it is particularly relevant to note that at this stage of the Chinook Mk II's service spurious ENG FAIL captions, lasting on average 7-8 seconds, were an increasingly frequent occurrence. These are now well understood but at the time they were not. Had such an indication occurred it would have caused crew considerable concern particularly as they were over the water with no obvious area for an emergency landing. Such a warning would also have required an urgent and very careful check of engine instruments and FRCs.
I also quoted this last paragraph at thread item 1788 above
Crew Duty Time
The comments of the Station Commander at Aldergrove (and also as SRAFONI responsible for authorising any CDT extension to the maximum allowable) were:
"Crew Duty Considerations- The crew of ZD 576 had flown a task within NI earlier on the 2 Jun. I concur with the Board\'s statement (para 66a), that the decision for the crew to carry out the Inverness sortie "Whilst not ideal, was not unreasonable". It was detachment practise, because of the extended day time in early June at Aldergrove's latitude, to preserve where possible, a "day-on day-off " routine between the 2 crews. Given the routine nature of the day's earlier tasking, it was reasonable, as a one off for a single crew to plan to complete the full day's tasking by extending flying hours within the Crew Duty Time (CDT).
Turning to possible further extensions of CDT, I do not believe that, in the absence of any firm evidence one way or the other, we can usefully speculate on TAPPER's further intentions after arrival at Inverness. At the time of the accident, the crew was operating within CDT extension which had been properly sought and granted (para 30b of the BOI), and fatigue was unlikely to have contributed to the cause of the accident."
Not surprisingly, since it would have been a major criticism of flying supervision at RAF Aldergrove, neither of the Air Marshals disagrees with the Station Commander's statement. In his book “Chinook Crash” the author Steuart Campbell also picked up this point impling that Tapper was acting alone by failing properly to take account of CDT on some sort of renegade mission - in fact nothing would have been further from the truth - both 230 Sqn and Aldergrove Operations would have been aware of the tasking and CDT issues (and if they were not they were failing in their duty) as would the JATOC. If supervisors had been unhappy with Tapper's plans they could have stopped them at any time, even allowing for the fact that Tapper was "self-authorising" - itself a carefully supervised delegation of authority from above.
Outbrief
In his comments on the lack of a formal outbrief the Stn Cdr Aldergrove commented:
I agree with the Board that, although Flt Lt Tapper filed to outbrief iaw the orders that were in force at the time he made best efforts to make details of his planning available. The planning of the sortie was clearly meticulous and indeed this evidence was of great use to the Board. I agree the lack of an outbriefing had no relevance to the accident.
This position was even confirmed by AVM Day who wrote:
….like the Board , I conclude that the crew’s outbriefing procedure at RAF Aldergrove had no relevance to the accident.
As I have said so many times before I believe that there are far more facts supporting an airworthiness or engineering dimension to this accident than there are hypotheses supporting aircrew error. I wish that PPRuNe contributors would look to, and hopefully support, these aspects – for which there is a lot of information now on this thread than going over old ground.