Flight standards authorities in Hong Kong are disputing Swedish investigators' findings that fatigue contributed to a Cathay Pacific Boeing 747's sustaining heavy damage after taxiing into its tow-tractor at Stockholm last year.
The jet had been pushed back from Stockholm Arlanda stand R9 for a service to Dubai but, shortly after the tow-tractor was disconnected from the nose-gear, the pilots started to taxi the aircraft before a ground technician had given an unambiguous all-clear signal.
It struck the tractor with its inboard left-hand Rolls-Royce RB211 engine. The rear of the vehicle penetrated the nacelle by 20-30cm (8-12in), heavily damaging the cowling, pumps, fuel lines and control units, and the engine began leaking fuel.
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Swedish investigation commission SHK found both pilots had been awake for 18-20h and that the time of the collision, 03:33 on 25 June 2007, fell within the low-activity period of the body's circadian cycle. It has concluded that both pilots "were affected by fatigue".
But the Hong Kong Civil Aviation Department's flight standards division says: "It is noted that the crew had been rostered to have adequate rest and there was no evidence in the report that the crew suffered from fatigue."
Although the Schopf 356 tractor had been moved a short distance, it remained out of the pilots' field of vision. SHK says that, while the pilots read the normal checklist after engine start, it "did not contain any point" concerning a "clear signal" - a thumb-up gesture showing an aircraft is clear to taxi.
Only a supplemental note in the carrier's expanded checklist informed pilots that the ground dispatcher would "clearly display" to them the steering pin removed from the nose-gear.
While SHK attributes the collision to "inadequate" checklists regarding confirmation of an all-clear signal, the Hong Kong authority says it has "difficulty in agreeing" with this conclusion, pointing out that the tractor driver and ground dispatcher had not previously performed pushback for a 747.
"We are of the view that the cause or causes should be established with due consideration of all factors and supported by the facts established in the findings," it adds.
The Arlanda tow-tractor driver, who was preparing to move the vehicle clear when he heard the 747's engines powering up, hastily abandoned it and the none of the ground personnel was injured. The accident badly damaged the tractor.
In its report into the event SHK adds that - despite the fuel leak, close to hot exhaust and electrical wiring - emergency services were not summoned for nearly an hour.
Source: Flight International
