Pressure loss ‘like an explosion’

Press, 27 February 1989, Page 1

Pressure loss ‘like an explosion’

By

LES BLOXHAM,

travel editor

Within seconds of the hole being ripped through the fuselage of the United Airlines Boeing on Saturday, a tonne of pressurised air would have rushed explosionlike out of the cabin, ripping seats from their floor mountings and blasting them into the freezing night. Twenty minutes after take-off from the warmth of sea level at Honolulu, the jumbo had climbed to 28,000 ft. At that altitude the outside temperature would have been at least minus 35deg. The sudden depressurisation would have sucked cabin bags and any other loose articles close by through the hole. As this was in front of the leading edge of the starboard wing, some debris was probably ingested by the two engines on that side. The captain reported a loss of power in both starboard engines moments after the hole appeared, forcing him to nurse the crippled jumbo back to Honolulu on its two port-side engines. Many passengers would have experienced varying degrees of ear discomfort as the airliner dived at least 18,000 ft to the less rarified atmosphere closer to sea level.

Modern airliners have to be pressurised before they can cruise at high altitutes — usually 40,000 ft for a Boeing 747 and 60,000 ft for Concorde. As an aircraft climbs, both the atmos-

pheric pressure and the temperature fall..

At sea level, the pressure is about 15lb a square inch but this falls to about 4lb a square inch at 40,000 ft and to 11b at 60,000 ft. Inside an aircraft, the cabin is adjusted slowly for passenger comfort to the equivalent of an altitude of 8000 ft — about 121 b a square inch — and maintained at that level by pressurising the fuselage. Air under full pressurisation in a 8747 adds about a tonne to its weight.

Saturday’s incident is the sixteenth problem involving Boeing aircraft over the last 12 months. In brief, they are:

• February 1988: 8747 bound for Washington forced to return to Heathrow after losing piece of metal on take-off. No-one hurt.

• April 1988: Fatigue causes mid-air collapse of part of the fuselage of an Aloha Airlines 8737. One killed during depressurisation, followed by successful landing. • May 1988: Fuel system defects cause two engines to fail and problems with a third on a Tokyo-bound 8747. Landed safely. • May 1988: Undercarriage door falls off an Icelandic 8727. Safe landing at Heathrow. • September 1988: Tests ordered on older 8747 s after a wing flap fails to retract on a British Airways jumbo after landing at Heathrow.

• December 1988: Pan Am 8747 en route from London to New York explodes over Lockerbie. Bomb responsible; 270 killed: • January 1989: Near-new British Midlands 8737-400 crashes after engines fail near East Midlands Airport; 45 killed. • January 1989: Five 8757 s are reported with crossed wires in fire extinguisher systems. • January 1989: A 2m section of a landing gear door on a TWA 8747 falls on to a building shortly before the aircraft landed safely at Los Angeles. • January 1989: Passengers and crew evacuated from a Canadian Airlines 8737 at Vancouver after auxiliary engine catches fire. • January 1989: Engine falls from a 8737-200 three minutes after take-off from Chicago. Returned for safe landing.

• January 1989: Engine fairing measuring three square metres falls off an Eastern Airlines 8757 on route to Los Angeles. Safe landing at Atlanta. • January 1989: 8757 lands safely at Heathrow with power from only one of its two engines. • February 1989: Qantas 8767 returns for safe emergency landing at Auckland with power from only one of its two engines. • February 1989: Flying Tigers 8747 freighter crashes into mountain on approach to Kuala Lumpur. Five killed. • February 25: Hole blasted in side of United Airlines 8747 on climb-out from Honolulu on route to Auckland. Nine killed.