CHINOOK ZD 576|
31 January 2002
By the Select Committee appointed to consider the
justification for the finding of those reviewing the conclusions
of the RAF Board of Inquiry that both pilots of the Chinook helicopter
ZD 576 which crashed on the Mull of Kintyre on 2 June 1994 were
PART 1: SUMMARY
1. On 2 June 1994, an RAF Chinook Mark 2 helicopter, ZD 576,
crashed on the Mull of Kintyre. All those on board the aircraft
were killed in the crash and the aircraft sustained catastrophic
2. RAF rules in force at the time provided that
deceased aircrew could be found negligent only where there was
absolutely no doubt whatsoever. The RAF investigating board concluded
that the most probable cause of the accident was that the crew
had selected an inappropriate rate of climb to overfly the Mull.
However the investigating board made no finding of negligence
on the part of the pilots; nor did the two station commanders
who reviewed their findings. Nevertheless the two Air Marshals
to whom the investigating board's report was submitted in turn
concluded that the pilots were negligent in that they failed to
take appropriate action when approaching deteriorating weather
near the Mull. If they intended and were able to maintain visual
flight they should have slowed down, turned away or turned back.
If on the other hand they were forced by the presence of cloud
to change from visual to instrument flight, they should have climbed
to safety altitude at maximum power while turning away. It appeared
to both the investigating board and the Air Marshals that the
aircraft had flown straight towards the Mull without altering
course for some 20 or more seconds before the crash.
3. The House of Lords appointed us, in July 2001,
to consider whether this finding of negligence was justified.
In preparing this report we have not only considered the evidence
which was before the investigating board and hence the reviewing
Air Marshals, but also additional evidence both oral and written.
This additional evidence related among other things to the weather
in the area at the time of the crash, to various mechanical problems
which had affected Chinook Mk 2 helicopters since their introduction
into RAF service, and to what reliance could be placed upon the
results of a mathematical simulation carried out by the aircraft
manufacturers, Boeing, to determine the movements of the aircraft
during its last few seconds of flight.
4. Information extracted from the navigation
equipment showed that, when the aircraft was 0.95 nm from the
point of impact on a given bearing, a "way point change"
was made to the navigation equipment to show the course and distance
to Corran in Argyll, the next staging point on the intended route.
There was no information as to the time this change was made,
or the course and speed of the aircraft. The same equipment also
produced an approximate height for the aircraft at an approximate
number of seconds before impact, but neither position nor speed.
A cockpit instrument showed a certain speed at impact. These results
were much relied upon by the investigating board and the Air Marshals
as demonstrating the final movements and speed of the aircraft.
5. From this information, and from certain other
information as to the position of the aircraft and some of its
components at impact, Boeing concluded that the aircraft had made
a final "flare"
upwards some 4 seconds before impact, and that for an unspecified
time before this the aircraft was climbing at a rate of 1000 ft
per minute at an airspeed of 150 knots, which with a tail wind
of 25 knots gave a groundspeed of 175 knots or thereabouts.
6. For reasons set out in our report, we consider
that Boeing's conclusions cannot be relied upon as accurate. Since
these conclusions are the basis for the conclusions of the investigating
board and the Air Marshals that the aircraft was under control
at the time of the final flare, it follows that there is insufficient
evidence to the required standard of proof that this was the case.
7. The additional evidence which we heard as
to the weather came from a yachtsman who was sailing near the
Mull at the time. He considered that when he saw the aircraft
some 300 yards away the crew would have been able to see the land
mass of the Mull. There was evidence before us from experienced
helicopter pilots that, when a way point change is made to the
navigation equipment, it is usual for pilots to change course
towards the next way point at that time or shortly afterwards.
In these circumstances we concluded that there could not be said
to be absolutely no doubt whatsoever that the pilots intended
to overfly the cloud-covered Mull; indeed the opposite is a distinct
possibility if not more likely.
8. We heard a good deal of evidence about mechanical
problems suffered by Chinook Mk 2s. Some of these problems were
intermittent, leaving no trace, and others were readily detectable.
Although no trace of any mechanical fault, other than a defective
radar altimeter, was found by the Air Accidents Investigation
Branch inspector, he was unable to dismiss the possibility of
an undemanded flight control movement, an engine run up or a control
jam having occurred. Any of these events could have had a serious
effect upon the crew's ability to control the aircraft. Once again
we consider that it could not be said that there was absolutely
no doubt whatsoever that some mechanical failure had not caused
a loss of control of the aircraft.
9. It is not our role to determine the likely
cause of this accident, and indeed on the evidence which we have
heard and read it would be impossible to do so. We are nevertheless
satisfied, on the evidence before us and against the standard
of "absolutely no doubt whatsoever", that the Air Marshals
were not justified in finding that negligence on the part of the
pilots of ZD 576 caused the crash.
1 A rapid change in pitch angle of the aircraft, either
to slow down or to climb quickly. Back