Accident Report : Caledonian Airways DC-7C, G-ARUD
4th March 1962 Continued from Page 2
Findings and comments
The aircraft, G-ARUD, was making flight CA153/154 a round trip from Luxembourg to Luxembourg via Khartoum - Lourenco-Marques - Douala and Lisbon.
During the flight, Captain Williams (Chief Pilot of Caledonian Airways) was to check Captain Frost for his qualifications to as an Aircraft Commander on this route.
The flight left Luxembourg at 22.12 hours on 1st March 1962 for Khartoum (Sudan), reaching there in 9 hours 28 minutes. The aircraft had an all up weight of 64,023 kgs and a centre of gravity of 30.1%. There were no unusual incidents on the flight, and no defects were reported at Khartoum.
After a stop of 1 hour 8 minutes, G-ARUD left Khartoum on 2nd March 1962 at 09:05 hours for Lourenco-Marques, which it reached in 9 hours 46 minutes. The weight was 62,663 kgs with a centre of gravity of 30.6%.
Following a stop of 36 hours 55 minutes, G-ARUD left Lourenco-Marques on 4th March 1962 at 08:00 hours bound for Douala. It reached Douala in 8 hours 32 minutes. The aircraft weight was 62,055 kgs, the centre of gravity is not known as this load sheet was not submitted to the Inquiry. Though, the information from Lourenco-Marques was that the aircraft took and seemed to climb away normally.
On arrival at Douala for a Technical Stop, refuelling was carried out under the supervision of the Flight Engineers. The refuelling was undertaken in two operations, initially 18,000 litres were loaded, then a further 756 litres were loaded. The reason for the additional fuel was never established, possibly increased fuel required to compensate for weather, or maybe after the tanks were dipped they came up short?). Though, the additional 756 litres of fuel was never added to the load sheet.
A repair to the HF aerial was also made by the crew and apron engineers at Douala. The repair was to the earthing on the fin.
Departure from Doula - 4th March 1962
G-ARUD started its engines at 18:02 hours. It was not possible to determine who was at the controls, though, the Inquiry made the following assumptions.
Due to the take-off conditions, (heavy aircraft, night, high ambient temperature) it was presumed that Captain Williams was in one of the pilots seats, accompanied by Captain Frost in the other. It was assumed that Mr McArthur was in the other due to his greater experience on this type of aircraft.
The air / ground conversations were not recorded at Douala Aerodrome, so it is impossible to know who was on the radio during take off. G-ARUD requested and was given clearance to taxi at 18:05 hours. The aircraft acknowledged receipt of the weather and wind information.
The aircraft taxied to the end of runway 04, leaving runway 12 / 30 clear for the arrival of Air Afrique DC-4 F-BBDK, which landed at 18:13 hours.
G-ARUD lined up on Runway 12, some witnesses heard the opening-up of the engines of the DC-7 while the DC-4 approached the apron. G-ARUD had been idling its engines for 15 minutes since starting, and this was probably designed to de-foul the sparking plugs. After 10 minutes of idling the recommendation was to set a BMEP (Brake Mean Effective Pressure) of 140 PSI for 1 minute or until the engines cylinder heads reached 200oC to de-foul the plugs.
The take-off was made at 18:20 hours. It was watched by the Tower Controller who noticed that the aircraft’s landing lights were not used and that the take-off run seemed very long. The aircraft having lifted off inline with the glide path transmitter, which is some 2,400 metres down the runway.
The take off was followed by a very slow climb, and the anti-collision light was witnessed to function practically to the point of impact. Apart from the shallow climb, no abnormal movements of the aircraft were noticed. Though there was no radio communication between the tower and the aircraft between take-off clearance and the accident.
Rejected Causal Factors
The Inquiry studied and rejected a number of scenarios in the course of the investigation, these are detailed below.
Act of Sabotage
No evidence came to light during the investigation to support this.
Failure of One or More Power Plants
Following the investigation of the power plants and importantly the propeller governors, Engine failure was eliminated by the Inquiry.
Control Surface Flutter
The examination of the control surfaces and their hinged connections, did not reveal any evidence to support this cause.
(Flutter is a self-starting and potentially destructive vibration where aerodynamic forces on an object coupled with a structure's natural mode of vibration to produce rapid periodic motion)
Incorrect Operation of the Undercarriage or Flaps
It was possible to establish that the nose wheel and starboard undercarriage were up and locked. The certainty that the port undercarriage was up and locked is lessened by the missing up-lock-hook, though the Inquiry accepted that it was very probably up and locked too.
Whilst the flap control lever was found in the 10o position, the Inquiry satisfied itself from other evidence that the flaps were raised at the point of impact. Studies on the climb performance with flaps retracted and flaps at 10o, at the speed reached, meant it was not possible to accept that flaps were a direct cause of the accident.
The investigation along the runway and the flight path of G-ARUD gave no reason to assume there was any structural failure of the aircraft.
Failure of the Instrumentation.
There were few instruments recovered from the scene, those that were found were damaged. The Inquiry was unable to confirm instrument failure, it was also not able to eliminate this as a factor either.
Though considered very unlikely from examination of the wreckage, the investigation was unable to total reject this possibility.
Incident in the Cockpit
The sudden illness or incapacity of a crew member could not be ruled out by the Inquiry.
Tables of crew rostering for the preceding 7 days were tabled and also tables of flying hours for the previous 30 days. These were in order, and sufficient intervals and rest days were recorded.
Errors in the Load Sheet
The Inquiry recognised that whilst there was a discrepancy of +1040 kg, the actual aircraft weight of 63,170 kgs was within the permitted take off weight for Douala, though an error in V2 borne from the load error may have been a factor. The correct V2 was 126 knots (V2 at 62,030 kgs was 124.6 knots). The Inquiry deemed that this small difference in speed, considering the speed attained by the time of impact, that the increase in weight could not have been a causal factor.
A number of abnormal circumstances were also examined by the Inquiry
The Inquiry was not able to find a satisfactory reason for why the landing lights would not have been used. It was airline policy that landing lights are to be used in all take off’s, unless they would inhibit the crew, for example in fog.
The aircraft had deviated some 405 metres off of an extended runway centreline when it impacted the first tree. This deviation of flight path from take-off is around 9o. The prevailing wind was calculated to cater for 2o, so 7o was still left unexcplained.
Calculations showed that at a speed of 140 knots and with only a slight bank to port indicated by the initial impact on the tree, the aircraft would have started to deviate from its heading almost immediately after take off. The Inquiry considered that this was probably as a result of the crew focussing on their instruments and trying to correct the problem with the aircraft’s climb rate.
Discrepancy between the Flap position and the Control Lever position.
The flap control lever was found bent over in the 10o notch after the accident, the investigation does not believe that this lever was moved between the initial impact with the tree and the subsequent damage to the cockpit which began as the aircraft passed through the trees.
Expert examination found that the flaps were fully retracted or very near to full retraction at the time of impact. The Inquiry accepted that the aircraft reached 141 knots, the speed at which flaps can be fully retracted and that this operation was carried out normally. Though; immediately afterwards some abnormality in the aircrafts behaviour led the crew to select 10o flaps but there was no time for the flaps to deploy before impact.
The Inquiry noted that Sabena had modified the take off and climb procedure in 1959 for their DC-7C’s and this was applied by the Caledonian Airways staff as trained by Sabena. The procedure was modified to a “speed” based only criteria for raising of the flaps, ie when V2 + 15 knots was reached, in the Douala take off, this was 141 knots.
The original procedure required an altitude of 400 feet to be reached before the flaps could be retracted when taking off at night.
The initial impact took place at a height of 22 metres (72 feet) above the runway’s height at a distance of 4900 metres (16,075 feet) from the beginning of the take off. The flight manual stated that should one engine have failed at V1, the aircraft should have still attained 300 feet above the point of initial impact by the time it had travelled 16,075 feet at its known take-off weight.
The Inquiry, accepting that all engines were operating correctly, determined that G-ARUD did not gain height due to a lack of power, and that the power applied was converted into an increase in speed. The maximum height reached by the aircraft has not been determined so was unable to state whether the impact was in level flight or resulting from a loss of height.
Abnormal take off run
Taking into the account of the Tower Controller and a 2nd witness Monsieur Maurer (duty tower electrician), the Inquiry accepted that though their position in relation to the runway did not allow for accurate estimates of distance, there were able to see that G-ARUD did take an abnormally long time to take-off.
The possible causes
1) Engine failure,
2) Abnormally high aircraft drag (flaps setting to high),
3) Difficulties arising when V2 was reached, causing the crew to deliberately or involuntarily delay in rotating the aircraft.
4) Deliberate holding down of the aircraft on the ground at a speed higher than V2.
The Inquiry found evidence of the engine power and the speed reached in its investigation so causes 1 and 2 were not accepted.
Cause 4, in the case of take-off with a low weight and in order to increase the safety margin in relation to Vmca (minimum controllable airspeed) some techniques promote a higher air speed to gain more control. The Inquiry did not accept this, as the DC-7 was heavily loaded and with 10o of flap, V2 was demonstrably higher than Vmca.
It was the Inquiry’s opinion that cause 3 appeared to offer the most suitable explanation for the abnormally long ground run at Douala.
The investigations did not reveal any incidents, like cockpit fire, smoke, electrical failure or fire indication, which could have resulted in the crew delaying take-off.
Though; testing undertaken in France showed that with one of the spring tabs jammed in the elevator control mechanism, it would have been necessary to exert a force of 40-45 kgs on the control column to rotate the aircraft. The normal force required, based on weight and the centre of gravity is 10-14 kgs, a level of exertion that the crew would not have anticpiated or expected.
The Inquiry published its report on 26th July 1963 in Paris, though despite over a year of expert examination of the wreckage and circumstances surrounding the accident, they were unable to determine with “absolute certainty” what had caused the accident to DC-7C G-ARUD.
They found that there was evidence to support the theory that an elevator spring tab mechanism may have jammed and that this would have resulted in abnormal elevator control forces being required during take-off. Their investigation showed that this would be consistent with a long take off run and the risk of losing height when the flaps were retracted.
They were unable to determine if instrument failure had been a cause or influenced any decisions, as the instruments had either not been recovered or where too damaged.
There were a number of recommendations made by the Inquiry at the end of the investigation.
The modification to the elevator mechanism designed by Douglas in Oct 1962 (7 months after the accident), should be made mandatory as soon as possible.
The Inquiry noted that the Cameroon Authorities had now installed a permanently positioned landing stage and boat at the creek, and also that they had cut vehicle access tracks into the area surrounding the aerodrome to allow faster access to any incidents. Also, additional lighting has been installed at the outer marker to give a visual fix for pilots along the extended runway centre line.
Their final recommendation was that Flight Data Recorders should be urgently installed on all multi-engined transport aircraft, which should give basic data in the event of an incident.
Following the phone call about the accident at 05:00 on March 5th 1962, Adam Thomson flew to Douala to assist with the investigation with Eric Goodyear. They were joined by pathologists and Crash Investigation experts from the UK, that were instrumental in assisting in the recovery and discovery of the causal factor.
Thomson attended the funeral ceremony in Douala as the victims of the accident were laid to rest, including that of his best friend, Capt Arthur “Bill” Williams. He also arranged for the memorial stone and for the maintenance of the graves with a local lawyer at the cemetery in Douala.
Thomson, himself a pilot, wrote of the accident
“When the spring tab evidence came to light and Bill Tench (Accident Investigator) described what had probably happened, I had a vivid mental picture of poor Bill, a pilot of immense experience, grappling frantically with a circumstance he could neither control nor understand. I imagined the nightmare of failing to gain height and the realisation that a crash in the darkness was inevitable.”
One question that I cannot find any reference to being asked or answered in the Official report, did Sabena carry out the elevator spring mechanism check recommended by Douglas after the same thing happend to a KLM DC-7, PH-DSL, in Buenos Aires in April 1961? As a professional company, overseen by the Belgian CAA, I would have thought that this work was undertaken.
The recommendations did help in the introduction of Flight Data Recorders, though it was to be 1965 before a viable FDR was available that could withstand the forces involved in an accident, prior to this the FDR’s were too fragile to survive.
The accident at Douala involving the DC-7C, G-ARUD, was a tragic loss. Being unaware of any of the obstacles at night that were around the aerodrome in the pitch darkness when compared to today's airfields, and facing a problem that was exceptionly rare, the crew were without a shadow of a doubt trying to control the aircraft right up to the end.
The following message was sent from the Queen: "I am deeply distressed by the news of the tragic accident to the DC-7C aircraft near Douala last night. Please convey my heartfelt sympathy to the relatives of those who lost their lives." The message was sent to Caledonian Airways for onward transmission to the relatives, via the Aviation Minister, who asked that his own personal condolences should be added to the message.
March 4th 2009 marks 47 years since this tragic accident, that happened a long way away from home, and a fitting time if there is such a time, to remember them.
Approach into Douala - Runway 30
Below is a piece of modern day video footage of an approach into Douala, using Runway 30. This aircraft is landing over the area that G-ARUD departed over. At 19 seconds into the footage, this aircraft passes directly over the small creek. G-ARUD crashed into the creek, 405 metres to the right of this aircaft's approach. The area is now built up with housing. The 2nd piece of water is another tributary to the Wouri River, and this is near the runway's threshold.