Commonwealth legislation

AD/B747/122 - Ice and Rain Protection - Pitot Static and Temperature Probe Icing

In ForceCTH

Jurisdiction

Commonwealth

Collection

legislative instrument

Plain English Summary

3/10 complexity

This airworthiness directive requires all Boeing 747‑400 operators to implement the actions in Boeing Alert Service Bulletin 747‑30A2069 (15 July 1993) so pitot/static and total air temperature probe heat remain effective if the aircraft unintentionally enters a “ground mode” while airborne. Compliance must be completed prior to 1 December 1993 and a Flight Manual Amendment will be issued under Approval Number A/QF747-4/27.

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Current sections

Direct links to the current provisions in AD/B747/122 - Ice and Rain Protection - Pitot Static and Temperature Probe Icing.

AD/B747/122 - Ice and Rain Protection - Pitot Static and Temperature Probe Icing

COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY

SCHEDULE OF AIRWORTHINESS DIRECTIVES

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Boeing 747 Series Aeroplanes

AD/B747/122 Ice and Rain Protection - Pitot Static

and Temperature Probe Icing

Applicability: All model 747-400 series airplanes.

11/93

Requirement: Action in accordance with Boeing Alert Service Bulletin 747-30A2069 dated 15 July 1993.

Note: FAA AD 93-14-21 Amendment 39-8646 refers.

Compliance: Prior to 1 December 1993.

Background: Operators have reported cases of aircraft entering the ground operating mode whilst still flying, due to depressurisation of the number four hydraulic system.

The Federal Aviation Administration (FAA) has determined that when there is a loss of pressure in hydraulic system number four, the wing gear trucks may relax sufficiently to exceed the tilted position indication, when this occurs on the sensing systems for both the left and right wing gear trucks, the aircraft will enter the “ground mode”. Additionally, if hydraulic system number one is depressurised and the body gear trucks relax sufficiently, the aircraft will enter the “ground mode” when the gear is extended for landing. FAA analysis indicates that various electrical and avionics systems, including the pitot and total air temperature heat systems, will be affected by this type of failure.

Compliance with this Directive will reduce the effect on aircraft systems by ensuring that full pitot and total air temperature heat in the event of an aircraft entering “ground mode” of operation.

A Flight Manual Amendment is required and will be issued under Approval Number A/QF747-4/27.

Source text

Sourced from the Federal Register of Legislation (legislation.gov.au), CC BY 4.0.

1 AD/B747/122 - Ice and Rain Protection - Pitot Static and Temperature Probe Icing