Accident Report : Caledonian Airways DC-7C, G-ARUD
4th March 1962 Continued from Page 1
Douala Aerodrome - 1962
The aerodrome is located at 9o42’ East, 4o01’ North
The aerodrome has two runways, and the runway used was 12 (124 o), with a length of 2,850 metres and a width of 45 metres.
It had a very slight descending slope, a negligible 0.21% along its length and was capable of supporting 150 tons on its concrete construction. It was lit and had high and low intensity lighting.
The official elevation of the runway was 36 feet, though the elevation at the threshold of runway 12 was 18 feet, and at runway 30 the elevation was 38 feet.
The documents published by ASECNA (Agency for the Safety of Aerial Navigation in Africa) and the Jeppesen chart used by the Crew on G-ARUD did not show any obstacles around the aerodrome, save for an unlit Radio Beacon Aerial that was some 6 kilometres from the aerodrome, along an extended runway centre line.
Only charts used by Air France at the time showed the presence of tall trees around the end of the runway.
The alert was given within 1 minute of the accident to the aerodrome fire services with its four crash vehicles.
Also, civil and military emergency services were scrambled almost immediately; these were based at the aerodrome too at that time. Hospital Doctors went out with the first rescue teams.
The rescue services attempted to reach the accident site by driving out along the service road that extends from the runway centre line (used to service lighting). This road stopped 500 metres short of the point of the crash site.
The first team came up against the creek at high tide and lost their bearings in the total darkness, reporting this to the aerodrome, a military aircraft then overflew the site switching on its lights when it overflew the crash site.
At 01:30 hours, the rescue team succeeded in approaching the wreckage by swimming across the creek, in spite of some burning fuel. A second rescue team managed to make it to the wreckage by following the gap in the jungle made by the descending aircraft.
At 02:30 hours all hope of finding any survivors was abandoned and the rescue teams withdrew leaving a guard in place.
06:30 hours on the morning of the 5th March 1962, the rescue parties arrived at the wreckage via the creek. Being low tide it was possible to search for and recover the victims of the accident.
The investigation looked into the operation of this sector of the flight to ensure that the load sheet and centre of gravity calculations were correct.
There were discrepancies within the load sheet of the DC-7 when it took off from Douala, and these were found to total 1,140 kilograms.
The Inquiry found that no account had been taken of oil in the nacelles, 762kg. Some 765 litres of fuel had been omitted, 530kg, and the passenger weight had been underestimated by 37kgs. Though the weight of spares had been over-estimated by 10 kgs, and no account was made for fuel burned while idling / taxiing, estimated at 179 Kgs.
The Inquiry drew the attention of Caledonian Airways to this error and to ensure that correct load sheets were completed with no omissions in future.
Centre of Gravity
The recommended centre of gravity from Douglas for a take off at Douala is 32.5%, the Inquiry accepted that the 29.5% as re-calculated by the Air Registration Board was correct.
Examination of the Wreckage
The wreckage was in a particularly awkward location and not all of the wreckage could be recovered. This was due to the permanent immersion of some parts within the creek and its banks. These banks were inundated with mangrove roots, and it was impossible to get mechanical handling equipment to the site. The recovery was made in stages as different scenarios were investigated by the Inquiry.
The first tree encountered by G-ARUD was an isolated tree some 2040 metres from the threshold of Runway 30, and 2,500 metres from the point of take off. The tree was located 405 metres to the left on an extended centre line from the runway.
The tree was 20cm in diameter, and was cut through at a height 22 metres above the threshold of Runway 30. It was not possible to locate this point of impact on the aircraft
72 metres further on, the aircraft hit two further trees at about the same height, though the plan shows the impact as “noticeably lower”. I surmise that the aircraft would have rolled over to port after the initial impact, possibly explaining the lower impact on the 2nd tree.
Around the trees were found parts of the port wing and nose wheel steering accumulator door, indicating that the left hand side of the aircraft bore the impact.
The aircraft continued on a heading of 110o, going down progressively onto the port wing in a dive. Large parts of the airframe started to come away from the aircraft, including the radome, propeller No 2, sections of the fuselage and parts of the tail plane.
The aircraft arrived over the creek, pitched forward in a 20o dive and banked to port 25o. At the time of impact with the water there was a large opening in the front of the cockpit and to the front left-hand side of the fuselage. The port wing was heavily damaged, but must have been still attached, as it was detached in the creek. The starboard wing sustained less damage than the port wing and was still attached. The aircraft disintegrated on impact with the water.
The Inquiry found that the aircraft did not turn over, items from the port side were found to the left of the wreckage trail, and starboard items on the right hand side of the trail.
Below is a map of the area (as it is in 2008), with the points marked to tie in with the description above.
Searches were made along the runway and the path the aircraft took through the trees, and examination of the wreckage gave no indications of structural failure. The aircraft broke up on impact, and no traces of fire were found on the submerged parts. Thus the aircraft did not appear to have suffered from a fire onboard whilst in flight.
Though photos of the accident clearly show that an explosion took place, though as there is no trace of fire within the submerged parts of the cabin, no trace of fire on the oil and fuel pipes, it was assumed that hydro-dynamic pressure within the cabin caused the explosion.
The aircraft had large holes in the forward part of the fuselage, and impacting the water at high speed pushed the water into the fuselage, compressing the air within the passenger cabin caused the cabin to explode open.
All of the engines were located, and none showed any sign of in-flight fire or any trace of mechanical failure aside from damage from the crash.
Propellers 1, 3 and 4 were found in the creek, whilst propeller 2 was found in the trees after the impact with the 2nd tree. None showed any signs of defect prior to the damage sustained in the accident.
Some propeller blades were found along the wreckage trail, though not all of the blade fragments were recovered.
The nose well was found in the creek and had become detached from the structure, though the indication was hat the nose wheel was locked up at the time of the crash.
The starboard main undercarriage was still attached too the structure, and was also in the up position as indicated by the Up-lock-hook found in the Up and locked position.
The port main undercarriage was found attached to the port win, though the whole section had detached from the aircraft on impact and was resting at the bottom of the creek. The Up-lock-hook was not found, though there was no reason to think it was not in the up position as with the other undercarriage.
There were signs of burning on some of the tyres, though this was only on sections of the tyres that broke the surface of the water, and was caused by the fuel that was on fire on the waters’ surface.
The flaps were badly damaged in the crash and all had become separated from both wings, and were found ahead of the aircraft, indicating they broke free at the point of impact.
Studies undertaken in France show that the flaps were fully retracted at the point of impact, this was determined from the bending of the hinged connections at the point they broke. Though the flap control lever was found in the 10o setting in the cockpit, the assumption was that the crew had just selected 10o of flap, though there was no time left for them to move.
The rudder was badly damaged by fire, though this is thought to have happened after the crash. Parts of the rudder were found near the tree line as the aircraft exited the jungle.
The elevators were badly damaged by the crash of the aircraft, though studies undertaken in France showed that the starboard elevator had a jammed part. The spring mechanism of the starboard spring tab was found to be jammed in such a manner as to prevent the movement of the spring tab in the nose up direction.
One of the meal fingers of part No. 4335688 of mechanism part no. 3-320252-501, has passed behind a fixed stop position, jamming the movement of the elevator.
The Inquiry noted that on April 7th 1961, a KLM DC-7C (PH-DSL) had aborted take off from Buenos Aires with a similar jamming of the starboard elevator. Following this incident Douglas issued a Technical Report suggesting, but not requiring, that the mechanism was checked.
Tests were commissioned as part of the Inquiry to test out the effect of this jamming to the starboard elevator.
The drawing below shows the position of the starboard elevator
The principal components of the electrical system were all recovered, and helped to eliminate the possibility that electrical failure or fire was the cause of the accident.
The tests showed that the electrical insulation on the wiring was intact, with no sign of burning or arcing in the cockpit. Also the report from the Tower Controller that the red anti-collision light functioned right up to the end, lead the Inquiry to believe that the electrical system was not the cause of the accident.
Very few of the instruments were recovered, the majority were lost in the creek bed and the remainder too heavily damaged to gain any meaningful information. Three items were of used by the investigation, the Pitot Tube, the Pilot’s Airspeed Indicator and the Pilot’s artificial horizon.
The Pitot tube was blocked with bark, from the passage of the aircraft through the trees, the other pitot tube did not reveal any evidence.
The airspeed indicator was too heavily damaged to be certain of what speed was indicated and the artificial horizon was damaged by the shock of the impact, and was also damaged by the ingress of sand from the creek, again impossible to test its function.
Similarly the control panels were heavily damaged, and were thought to have been moved during the recovery, such that no information was useful from them.
All of the main tanks of fire extinguishing agent were empty, though this was deemed as a result of the valves and pipes being damaged in the accident. A portable extinguisher was found intact and had not been discharged. Though, the Inquiry could not establish if the crew had used the fire fighting equipment before to the impact.
The Inquiry investigated the fuel from the tank used at Douala Aerodrome, and also the sample jars used for draining after refuelling.
The investigation was not able to perform many tests on the samples, due to the small amount of fuel available, also the fuel had not been stored well and had evaporated from the storage jars.
Though the Inquiry was satisfied that the evidence obtained from the engines, and the settings of the propeller domes, indicated that there was no drop in power caused by a fuel related problem.