RAF Chinook Helicopter Crash. 1994, Mull Of Kintyre

1
RAF Chinook Helicopter Crash.1994, Mull Of
Kintyre
2
Background

• On June 2 1994 an RAF Chinook helicopter that was
  carrying 25 anti-terrorism experts as well as
  four crew members crashed near the Mull of
  Kintyre in Scotland.
• Accident Investigation led by Department of
  Transports Air Accident Investigation Branch.

3
Background (Continued)

• Investigation concluded that there was no
  evidence of a technical malfunction of the
  helicopters control system.
• Later RAF Inquiry, blamed the crash on the two
  pilots
• However new investigations have since pointed to
  strong evidence that Chinooks FDEC control system
  was faulty.

4
FADEC Control System Development and Testing
History

• Martin Dawson

5
Will Cover

• Overview of FADEC Project Development
• Errors Found During Tests

6
FACEC Development History

• Mark one Chinook to undergo series of
  modifications
• One Improvement was new FADEC Control System
• First Control System to Have Full Authority Over
  Engine
• However When First Conceived, FADEC Was to Have
  Manual Backup Mode

7
The Parties Involved

• Boeing as Main Manufacturer
• Multiple Subcontractors
• Tensions Arouse
• Communication Failures Between Various Parties
• Disagreements Arouse

8
Disagreements Continued..

• Little Concern Given To Lack of FACEC Safety
  Features by MOD
• This Despite Boeing Classifying FADEC System as
  Safety Critical Component
• RAF Also Voiced Concern About FADECs Planned
  Tests
• RAF Thought They Were Too Late in The Project
  Lifecycle

9
Errors Found During Testing

• Chandler Evans Report from 1987
• Lycoming Endurance Tests Reports
• B2 Error
• F3 Error
• E5 Error

10
E5 Error

• Related to Control of N2 Sensors That Monitored
  Rotor Speed
• Run-Down
• E5 Code Had Fatal Flaw
• If Both Sensors Were Knocked Out FADEC Lost
  Control of Engine Speed
• Putting More Fuel In Engine, Causing Over-speed

11
Other Errors

• Aeroplane and Armament Experimental Establishment
  Investigation
• Code Contained a "very large number of errors
• EDS-Scicon
• Found so Many Errors That They Commissioned the
  Report After Investigating Only 20 of the Code

12
1989 Chinook Mk2 Ground Test

• Gary Davies

13
Chinook Mk2 Ground Test

• Took place on 20th January 1989
• It would cost the RAF 5 million
• Circumstances that caused the accident had been
  highlighted 3 year earlier
• Some of the fault codes displayed would also
  appear in the 1994 Mull of Kintyre crash

14
Chinook Mk2 Ground Test

• During the first week of testing E5 fault codes
  kept registering on the DECU (Digital Electronic
  Control Unit)
• So a change to the test plan was decided
• The change would be to disconnect N2b rotor speed
  signal to simulate small arms fire and to
  validate the design of the FADEC

15
Chinook Mk2 Ground Test

• During power up on the morning of January 20th an
  E5 fault code registered on the DECU
• Effectively meaning the FADEC had disconnected a
  N2 signal on power up
• Meaning only one sensor was being read
• So when remaining signal was disconnected no N2
  signals were being received by the FADEC

16
Chinook Mk2 Ground Test

• Due to the design flaw in the FADEC
• When both N2 signals were lost the FADEC thinks
  there is no rotor speed
• So the maximum amount of fuel is sent to the
  engines
• Causing an engine overspeed

17
Chinook Mk2 Ground Test

• When the remaining N2 signal was disconnected
  number of things happened-
• the engine noise increased
• there was an increasing whine from the
  transmission system
• a torque split developed

18
Chinook Mk2 Ground Test

• A torque split is when a mismatch occurs
  between the power supplies to the two engines
• This was significant as a torque mismatch was
  found in the 1994 crash

19
Chinook Mk2 Ground Test

• When the rotor speed reached 142
• Co-pilot pressed the Emergence Engine Fuel Cut
  Off Lever
• Which cuts fuel to engine

20
Chinook Mk2 Ground Test

• The E5 fault code and the torque mismatch errors
  would later be found the 1994 wreckage
• Textron-Lycoming later identified a failure in
  the design of the FADEC system was cause for the
  rotor overspeed accident

21
AAEE Recommendations
22
AAEE Recommendations

• Aeroplane and Armament Experiment Establishment
  (AAEE)
• Where the final testing of the Chinook took place
  
• AAEE have no say whether the Chinook should be
  given a Certificate of Airworthiness

23
AAEE Recommendations

• Final say is with the RAF
• the RAF can release into service an airplane
  with one wing if it believes there is an
  operational need for it (RAF Justice Report,
  p4-4)

24
AAEE Recommendations

• In November 1993 before the AAEE was able to
  give a positive unquestionable recommendation
• The RAF gave permission for the FADEC-equipped
  version of the Chinook the go ahead for
  operational service

25
AAEE Recommendations

• The reasons the RAF gave for their decision were
  -
• US Army had no critical problems during ground
  and flight testing
• The chance that both FADEC systems fitted to the
  two engines would fail was unlikely

26
AAEE Recommendations

• Problems with RAF reasons -
• US Army was using a different FADEC system
• Assumes the FADEC will fail in a predictable way
  which would cause the engines to rundown safely.
  This didnt happen in the 1989 accident
• But the Chinook Mk2 went into service despite
  concerns

27
Crash Investigation
Russell Daniels
28
Will Cover

• Overview of the day the Chinook ZD576 crashed
• Investigation into the Chinook ZD576 and the
  FADEC system aboard this and other MK2 Chinooks

29
Restrictions in place

• On the day of the crash restrictions were still
  in place on the Chinook MK2 ZD576. These were
  still in place partly because the software had
  not been re-written to take into account some of
  the possible problems

30
Overview of the Crash

• On Friday 2nd June 1994 The Chinook MK2 ZD576
  piloted by Jonathon Tapper and Richard Cooke
  crashed into the Mull of Kintyre (Scotland)
• Everything seemed normal up to 18 seconds before
  the crash. The pilots entered a pre-planned
  change of course into the navigation computer

31
Overview of the Crash Continued..

• However, the Chinook did not make this intended
  turn and flew straight on and crashed into the
  Mull
• If nothing else this would have put Tapper at
  risk of breaking the icing restrictions due to
  the cloud cover at the top of the Mull
• Squadron leader Robert Burke knew Tapper. He
  would have not broke the restriction. He was the
  most by the book pilot I knew

32
Overview of the Crash Continued..

• The investigators into the crash concluded that
  there was no technical evidence of a technical
  malfunction capable of causing the crash of the
  MK2 Chinook
• Blame was placed upon the two pilots and they
  were convicted of gross negligence.

33
Other FADEC equipped MK2s

• The AAEE at Boscombe had suspended trails during
  the time of the crash of the MK2 Chinook due to
  the lack of explanations from the FADECs
  contractors over incidents that had frequently
  occurred over a period of a couple of weeks

34
Investigation Into The Crash

• Fault codes were found in the memory of the
  surviving control systems (including E5) but
  the contracts of the FADEC system said that it
  wasnt significant
• The accident inquiry team were NOT told that the
  ministry of defence was currently suing the
  FADECs contractor mainly over defects in the
  design of the FADEC

35
Investigation Continued..

• Many things were left out of the report from the
  AAIB crash investigators such as the problems
  with the PTIT gauges before the day of the crash
  and on the day of the crash which has lead to the
  engine of the ZD576 being changed

36
Investigation Continued..

• The RAF report inquiry did not mention anything
  about the EDS or the AAEE reports on the
  inadequacies in the Chinook MK2 FADEC system
• The torque mismatch two months earlier was also
  left out which was one of the reasons for the
  engine being changed

37
Four Years Later

• Four years later another Chinook MK2 helicopter
  piloted by Bric Lewis went out of control The
  Chinook is falling out of the sky yet the
  displays show no warning lights no evidence of
  technical malfunction Lewis shouted

38
Lewis and a MK2 Chinook

• This Chinook did a 360-degree barrel roll but
  somehow Lewis managed to land it. If he and his
  crew had died then the crew would most likely
  have be found accountable, as this investigation
  also found NO EVIDENCE of technical malfunction
  as with the ZD576

39
Modified FADEC System

• The Dutch were satisfied with the FADEC software,
  but did not acquire the FADEC software until
  years after the crash of the ZD576. In this time
  modifications were made. Textron claims that the
  software was 99 the same as the ZD576. Others
  claim that it is less than 95 the same

40
To Conclude

• To conclude no technical evidence could be found
  in order to blame the FADEC system for the crash.
  This however does not mean that the crash wasnt
  due to the FADEC system onboard