‘Pilot Intervention Difficult Problem’

Press, Volume CIV, Issue 30810, 23 July 1965, Page 1

‘Pilot Intervention Difficult Problem’

(New Zealand Press Association) WELLINGTON, July 22. “When two airline captains of equal experience are flying together, the tendency must inevitably be for a degree of hesitancy before intervention, particularly when a number of exercises have already been successfully accomplished,” says the Chief Inspector of Air Accidents, Wing Commander O. J. O’Brien.

His report on the crash of an Air New Zealand Electra at Whenuapai on March 27 was released tonight. Wing Commander O’Brien says the point of intervention is a difficult and recurring problem.

“The reduction in the time factor referred to could be significant when related to the time taken for the pilot to scan his instruments.” A competent authority assessed this at 2.23 seconds, Wing Commander O’Brien says. The crash was, in his opinion, caused by a heavy landing on one main gear at a rate of descent which imposed a landing load in excess of that capable of absorption by one undercarriage structure. But he says it is considered the inquiry should be left open until the report of the Chemistry Division of the Department of Scienific and Industrial Research is available. Wing Commander O’Brien says the documentation of the aircraft was in orde- the crew was properly licensed, there was no failure of the airframe or engines prior to the accident. Quick Descent The aircraft was sinking at a high rate of descent when it touched down on one gear in the landing attitude. The sink was induced by flare technique and the number of aggravating factors (which in isolation would not have been significant) combined in the approach to create the circumstances which made the accident possible. Wing Commander O’Brien says at 6 a.m. the aircraft was airborne on a routine training exercise under the command of Captain W. P. N. Clarke, training captain, who occupied the right-hand seat. He was supervising a 180day check of Captain C. J. Le Couteur who was at the controls in the left-hand seat. “With overcast and dawn light conditions, the first exer-

cise was a twin locator instrument approach and overshoot. This was followed by a threeengine landing, an aborted take-off, a simulated engine failure on take-off, a twoengine landing, a bad weather circuit and a touch-and-go landing. “All these exercises were performed in a competent manner and the aircraft functioned normally in every respect. Idle Approach “On the down-wind leg of the circuit following the touch-and-go landing, the training captain nominated a flight idle approach on to runway 22. “Captain Le Couteur ran through the specific routine for the exercise and the training captain then intimated that he would like the approach to be started from 700 ft, a ‘more realistic’ height in that it was the normal minimum altitude for a twin locator approach on to runway 22. “Captain Clarke stated that he, himself, would nominate the point at which the descent was to start.

“During the line-up on finals at 700 ft and indicated air speed of 140 knots, the training captain suggested that the pilot should apply full flap before reducing power because, in his opinion, this technique gave better airspeed control. “At a signal from the training captain, the pilot applied full flap, retarded power to flight idle and rotated the aircraft into the steep approach altitude, using appropriate trim to relieve stick forces. “Five knots of airspeed were lost in the transition to the steep approach altitude, which the pilot attempted to regain by steepening the angle of approach. As a result, he noticed that his airspeed had improved to 137 knots. “After the flare had been initiated, the aircraft continued to sink at a high rate of descent. At this juncture the training captain called “check exclamation” indicating that he required the flare to be increased. Sank Heavily “Simultaneously, the pilot continued to move the control column back and also applied power. The aircraft, however, sank heavily on to the runway in the landing attitude with the control column fully back. “In Captain Le Couteur’s view the landing was the heaviest he had experienced in an Electra aircraft. In Captain Clarke’s it was a hard landing but not exceptionally so,” Wing Commander O’Brien says. On wheel marks left by the aircraft, he says the first impression on the runway was made by the port outer tyre at a point 640 ft from the threshold. The mark of the port inner tyre appeared at 641 ft. The marks started with the characteristic taper associated with contact by a non revolving wheel. Within six feet the taper widened to eight inches indicating contact at a high rate of descent. Tyre marks then ran perfectly straight for 18ft 6in then skipped, touching the runway at 10ft intervals over 56ft. “The absence of clearly identifiable imprints of the starboard wheel and nosewheel tyres indicates that these wheels were not sub‘ected to heavy landing ,oads.” Dealing with the port undercarriage, Wing Commander O’Brien says inspec-

tion revealed the lower cap of the landing gear support at station 167 fractured in upload approximately 20in each side of the starboard trunnion block. This up-load was transmitted through the rib internal trusses to the upper cap which deformed upwards and fractured the upper surface of the mainplane. The upper cap itself fractured approximately mid-way between the truss and the front spar. The rib internal trusses were deformed in compression and all the internal brace fractured. Deformation of the components in the vicinity of fractures indicated no prior defect. The port main gear support rib at station 209 was severely deformed, the internal braces fractured and the trusses collapsed in compression. But the upper surface of the mainplane was not fractured at this station.

“The entire main gear assembly had been carried rearward. In consequence, the upper drag link had torn away a portion of the front spar and the retract strut punctured the rear spar. “Viewed in elevation, the port and starboard trunnion bearings were out of alignment as a result of the entire gear assembly being rotated some 10 degrees to port. This was reflected in the malalignment of the upper and lower drag links. “This distortion, however, could have been caused or accentuated by the subsequent dragging of the port mainplane along the runway and also by a degree of subsidence when subjected to intense heat. Tyres Damaged “Both tyres were severely damaged by fire but there is no reliable evidence they were inflated when the port mainplane came to rest. Two indentations were present on the outer rim flange of the port outer wheel. No corresponding indentation was found on the runway.” Wing Commander O’Brien says examination of the starboard main gear structure revealed no deformation or damage. A span-wise wrinkle was apparent on the lower wing skin between the trunnion blocks. No deformation of the upper wing skin occurred in this area and both tyres were inflated. After dealing with propellers, the break-up of the aircraft and the fire which followed, Wing Commander O’Brien says the presence on the runway of heavy port wheel marks and the structural deformation and failure of -the port mainplane at station 67 indicate that the factor which made the accident inevitable was landing on one main gear at a rate of descent which imposed an asymmetric ground load in excess of that capable of being absorbed by a single undercarriage structure. He says that during the course of investigation it had not been thought necessary to call up any special inspections on Electra aircraft and the circumstances of the accident did not reflect on the integrity of the Electra as a type.