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Air Safety Week, Oct 3, 2005

Note particularly the emergency airworthiness directive of Aug. 29 and the request for comment on the security initiative of

Sept. 21.

Flight control safety: Emergency airworthiness directive ? Boeing B777- 200, -300 and -300ER

Aug. 29, AD 2005-18-51

Requires installing previous air data inertial reference unit (ADIRU) software pending resolution of a final fix to prevent anomalies in the fly-by- wire primary flight control, which can result in deviation from intended flight path, high pilot workload and possible loss of control of the airplane.

From the Australian Transport Safety Bureau (ATSB) report of investigation, released Sept. 16:

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"The pilot in command (PIC) disconnected the autopilot and lowered the nose of the aircraft. The autothrottle commanded an increase in thrust, which the PIC countered by manually moving the thrust levers to the idle position. The aircraft pitched up again and climbed 2,000 ft. The PIC notified air traffic control (ATC) that they could not maintain altitude and requested a descent and radar assistance. The crew was able to verify with ATC the aircraft speed and altitude."

Faulty software caused a Malaysian Airlines B777-200 to pitch up about 32 minutes after takeoff from Perth, Australia, on a flight to Kuala Lumpur on Aug. 1. The pilot in command disconnected the autopilot, but the airplane climbed to 41,000 feet as speed degraded to 158 knots. Both stall warning and stickshaker activated.

Flying the airplane manually, the pilot returned to Perth for a landing. For details see the ATSB report) at www.atsb.gov.au/aviation/occurs/occurs_detail.cfm?ID=767.

The ADIRU failure caused the minimum maneuver and overspeed margins on the speed tape to converge; the indicated airspeed was rock steady, but when the minimum speed indication rose up the speed tape, it caused the autothrottle to think the aircraft was flying too slowly ? and constantly tried to increase power. The problem was with the indications, not the actual speeds; it is a case where you cannot always believe what you see.

Minimum equipment lists (MELS) have recently been altered to reflect this situation. Specifically, the SAARU (secondary attitude/air data reference unit) is no longer an "allowable" inoperative discrepancy.

A Boeing message, sent to all B777 operators on Aug. 9, before the FAA action, said, in part: "The flight crew should disconnect the autopilot and manually fly the airplane. Although initial manual control forces may be high, the affects of the ADIRU anomaly on manual control forces are expected to diminish within 10 seconds and should be back to near nominal within 2 minutes. ? Boeing and Honeywell (ADIRU supplier) are supporting the ATSB investigation and are addressing the issues raised by this event with the highest priority."

Action mandated by the Federal Aviation Administration (FAA) basically overrules AD 2005-10-03, which was supposed to correct the ADIRU software deficiencies but in fact made them worse (see ASW, May 30, May 11 entry).

This is arguably the most significant software-related flight control anomaly yet experienced on a fly-by-wire aircraft in revenue service.

Fuel system safety: Final rule ? Airbus A318, A319, A320 and A321

Sept. 21, FR Doc 05-18518; Docket No. FAA-2005-21189; AD 2005-19-14

Requires modification of electrical bonding of all structures and systems inside the center fuel tank to prevent electrical arcing and consequent explosion of the fuel tank. Airworthiness directive (AD) effective Oct. 26.

Relates to fuel system safety reviews ordered by the FAA and actions under SFAR 88 to reduce ignition sources in fuel tanks. This was one of a number of actions expected to come out in the Federal Register (see ASW, July 11).

Cost estimated between $3,100 to $4,500 per airplane. Affects 506 airplanes in U.S. registry.

Fuel system safety: Final rule ? Airbus A320-111 and A320-200

Sept. 21, FR Doc 05-18520; Docket No. FAA-2005-21861; AD 2005-19-16

Requires installation of a bonding strip between each of the two scavenge pumps of the center fuel tank to prevent an ignition source that could ignite flammable vapors and consequent explosion of the fuel tank. AD effective Oct. 26.

Cost about $65 per airplane. Affects 371 airplanes in U.S. registry.

Navigation safety: Final rule ? Boeing models B737-300 through -900

Sept. 21, FR Doc 05-18523; Docket No. FAA-2005-20347; AD 2005-19-19

Requires installing upgraded software to flight management computer (FMC) to prevent map shifts, which could result in a navigation error and a near miss or possible collision with terrain or other aircraft. AD effective Oct. 26.

Prompted by operator reports of FMC map shifts on several B737-400s.

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Significant Regulatory Activity

Air Safety Week, Oct 3, 2005

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