Dan Air Flight 240

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Dan Air Flight 240
G-ASPL HS748 Dan Air BHX 27-05-78 (20357235349) .jpg

The affected machine
Accident summary
Accident type Loss of controllability
place Near Nailstone , Leicestershire , United Kingdom
date June 26, 1981
Fatalities 3
Survivors 0
Aircraft
Aircraft type Hawker Siddeley HS 748-108 Srs. 2A
operator Dan-Air
Mark G-ASPL
Departure airport London Gatwick Airport
Destination airport East Midlands Airport
Passengers 0
crew 3
Lists of aviation accidents

On June 26, 1981, a Hawker Siddeley HS 748 crashed on a mail cargo flight of Dan-Air from London Gatwick Airport to East Midlands Airport near the settlement of Nailstone , Leicestershire , with all three occupants killed.

plane

The aircraft affected was a 17 year old Hawker Siddeley HS 748-108 Srs. 2A with the aircraft registration G-ASPL, which was equipped with two Rolls-Royce Dart 533-2 engines.

course

The aircraft took off from London Gatwick Airport at 17:28 local time. The estimated time of arrival at the destination was 6:25 pm. The aircraft climbed to FL 100, the planned cruising altitude (approx. 10,000 feet or 3,050 m ) under instructions from air traffic control . At 5:59 p.m. the aircraft left FL 100 after the pilots had received clearance to descend to FL 60 (approx. 6,000 feet or 1,830 m). At 6:03 p.m. the voice recorder recorded a conversation between the captain and the flight attendant (the airline had a flight attendant, known as a Postal Assistant or PA , fly with it on postal flights ).

The recorded conversation translated into German accordingly
speaker English German
Flight attendant The indicators on the rear port door are showing red The indicators on the aft port door are red
captain Showing red? Show red?
Flight attendant Yeah, it looks as if the it looks as if the handles (possibly 3 or 4 unintelligible words) on it showing red not normal Yes, it looks like that, it looks like the handles (maybe 3 or 4 unintelligible words) for it are showing red, not normal
captain Passenger door, sorry Passenger door, sorry
Flight attendant Yeah Yes
captain Oh Oh

When the flight attendant reported his observations, the aircraft was still descending at a speed of 210 kn (390 km / h ). Shortly thereafter, the engine power was reduced and the aircraft temporarily went into level flight, while the speed dropped to 140 kn (260 km / h). While this was happening, the copilot made a comment about a “strong updraft”, which the master replied with the words “No, the rear passenger door ....... the port passenger door show unlocked”. The captain's comment and actions at the time indicate that he was very concerned about the safety of the door and the impact on cabin pressure. As a result, he ordered the increase in the speed with which the cabin pressure was already reduced in preparation for landing. He also instructed the flight attendant to stay in the front of the cabin in case the door was thrown open. The master hoped that his actions would reduce the risk of this, but at the same time, as a precaution, he reduced the speed to minimize the impact damage to the horizontal stabilizer should the door come loose. At 6:06 p.m., the aircraft went into level flight according to the clearance at FL 60.

At 18:08, air traffic control instructed the pilots to contact Castle Donington Approach Control (the callsign for East Midlands Airport). After the connection with Castle Donington was established, the pilots were given clearance to descend to 3,000 feet (approx. 915 m). At this time the flight speed was 135 kn (250 km / h). The master reduced the engine power and initiated a descent at a speed of 150 kn (280 km / h). The background noise on the voice recorder changed at 6:09:30 p.m. when the aircraft descended through an altitude of 5,450 feet (approximately 1,660 m). The change was abrupt and characterized by a jerky noise, which is typical of a rapid loss of cabin pressure due to the opening of a door (it was later found that the luggage door - the rear right door - had opened in flight). The background noise gradually increased in a manner consistent with an increase in airspeed. A number of unusual noises were also heard, including strong vibration. The flight data recorder and voice recorder continued for seventy seconds from the time the pressure drop occurred; it is assumed that the end of the recording coincides with the time of the hull hitting the ground. The cabin pressure loss occurred while the aircraft was in the Market Bosworth area.

The captain's remarks indicated that something very violent had happened to the aircraft almost immediately after the pressure drop, and after just eleven seconds he asked the co-pilot to make a Mayday emergency call. He also instructed the flight attendant to buckle up. In his emergency report, the copilot reported to the Castle Donington air traffic controller: “We would like a direct approach. We have, uh, had a huge pressure drop, uh, it looks like we've lost our back door and we have a serious tax problem ”. He was then instructed to descend to 2,000 feet (610 m) and steer a 360 ° course for a two mile (3.7 km) final approach. He confirmed this and asked in an interrupted radio message to provide emergency services. When air traffic control received this emergency report, they alerted the airport rescue workers and the police. The radar controller noticed that the aircraft was moving to the right beyond the assigned course. Despite several inquiries, she received no answer and no radio contact was made. When the aircraft disappeared from the radar screen 8 miles (approx. 15 km) south-southwest of the airfield, the controller asked the crew of another aircraft that was nearby. About three minutes after the radio had been sent, a report from the police of a plane crash reached air traffic control. When this was confirmed, the search for the aircraft was canceled. Many eyewitnesses saw the crash. Their descriptions include e.g. T. were very different.

root cause

The Air Accidents Investigation Branch was investigating this case. The cause of the accident was found to be a failure of the luggage door, which came loose and then got stuck on the leading edge of the right horizontal stabilizer , which changed the aerodynamic properties to such an extent that the aircraft could no longer be controlled. The failure of the luggage door could be attributed to several factors and problems:

  • The lock of the luggage door had a defect, as a result of which the upper and lower claw locks had lost their synchronization (the upper claw locks were not geometrically locked, while the lower ones were locked beyond the dead center position )
  • The system that was supposed to have warned the crew of the failure failed
  • The luggage door could not be closed completely with the outer locking lever, but the luggage door was closed with the outer lever, so the door was not properly locked all the time
  • There was an inspection window on the luggage door, but it was impossible to verify that the door was properly locked

The flight data recorder showed that the aircraft leaned 6 ° -8 ° to the right and slightly upwards during decompression. Ten seconds after decompression the aircraft began to lean further and further to the right, the aircraft nose lowered and the aircraft went into an increasingly steep dive , in the course of which the speed rose to 230 kn (approx. 425 km / h) and through The high loads (abrupt change in pitch) eventually led to structural overloading of the aircraft, which tore off both wings before the impact. At 18:10:39, the plane finally hit. During the investigation, various tests were carried out in the wind tunnel to check the effects of a luggage door hanging on the horizontal stabilizer. First, the scenario of a luggage door hanging on the door frame was examined. There was no change in lift, but an increase in drag and a loss of stability and effectiveness of the horizontal stabilizer. The situation where the luggage door was hanging on the horizontal stabilizer was then investigated. The tests showed the same pattern regardless of where the luggage door hung.

Security Recommendations

Several safety recommendations were made in the report:

  • 1: The review of the BAe 748's door warning and display system to rule out implausible and ambiguous displays, especially with regard to:
  • a) the desire to make the critical components of the locking mechanism visible from the inside
  • b) improving the operation of the mechanical indicators so that they only show a positive indicator when the door is securely locked
  • c) The pressure- and speed-dependent locking mechanisms (if installed) should be less dependent on the exact position of the respective second locks
  • 2. The electrical warning system should be checked to improve the reliability of the warning displays in the cockpit and to help locate open locks.
  • 3. The Civil Aviation Authority and the aircraft manufacturer are reviewing the BAe 748 maintenance manuals to ensure that the failure diagnosis and wear limits are performed for the aircraft's more critical systems, such as B. the door locking system, for maintenance personnel to improve
  • 4. The CAA talks to the operators and manufacturers about the introduction of an effective system to identify recurring defects, to investigate them and to correct them
  • 5. The expansion of the MOR system ( Mandatory Occurrence Reporting ) so that manufacturers of British aircraft have to provide information on incidents involving aircraft registered abroad, as far as they are aware of them.

swell

Coordinates: 52 ° 39 '58 "  N , 1 ° 21' 55"  W.