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Overhead Kinglake at 5,500 ft on approach into Melbourne the crew received a terrain proximity alarm and applied emergency climb power, climbing to 7,000 ft. This is one of a large number of spurious warnings occurring to the world fleet of Boeing 747-400 aircraft. In broad terms, the problem is in the logic of the ground proximity warning system (GPWS) which allows a warning to be registered when the landing gear is retracted and the number 1 radio altimeter registers an altitude of 2,500 ft (ie 2,500 ft above terrain). The aircraft manufacturer has devised a modification to the antenna and the number 1 radio altimeter that has since been incorporated into the operator's fleet and these spurious warnings no longer occur.

Download Final Report
[ Download PDF: 11KB]
General details
Date: 03 July 1993 Investigation status: Completed 
Time: 13:35 EST  
 Investigation type: Occurrence Investigation 
 Occurrence type: E/GPWS warning 
Release date: 05 April 1994 Occurrence class: Operational 
Report status: Final Occurrence category: Incident 
Aircraft details
Aircraft manufacturer: The Boeing Company 
Aircraft model: 747-438 
Aircraft registration: VH-OJD 
Sector: Jet 
Damage to aircraft: Nil 
Departure point:Sydney NSW
Destination:Melbourne VIC
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Last update 23 July 2015