AIR CARRIER ADVISORY CIRCULAR
Controlled Flight Into Terrain
This Air Carrier Advisory Circular (ACAC) is intended to bring to the attention of air carriers the continuing high rate of controlled flight into terrain (CFIT) accidents.
"While on the Subject ...", Aviation Safety Reflexions, Transportation Safety Board of Canada, Issue 2, June 1993, pages 8 and 9.
Since 1979, the International Civil Aviation Organization (ICAO) has recommended that a GPWS be required in operations involving turbojet aircraft that are over 15,000 kilograms, or authorized to carry 30 or more passengers.
The Ground Proximity Warning System Order (Air Navigation Order, Series II, No. 22) which became effective on February 9, 1989, requires a serviceable GPWS on all commercially registered turbojet aircraft with a maximum certified take-off weight of greater than 15,000 kilograms and a passenger capacity of 10 or more.
Recent accidents have directed international attention towards the ever present risk of an aircraft under control of its pilot flying into terrain.
The Flight Safety Foundation has determined:
When a GPWS warning occurs, pilots should immediately, and without hesitating to evaluate the warning, execute the pull-up action recommended in the company procedure manual;
In the absence of a company procedure, an immediate maximum performance full-power climb should be initiated and continued until the GPWS warning stops and the crew determines that terrain clearance is assured;
This immediate pull-up procedure should be followed except in clear daylight visual meteorological conditions when the flight crew can immediately and unequivocally confirm a false GPWS warning; and
- Air traffic control (ATC) should be notified as soon as possible after a GPWS warning or pull-up.
Between 1956 and 1992, Transportation Safety Board (TSB) of Canada statistics indicate that, in Canada, there were 59 accidents in which fixed wing aircraft flying under instrument flight rules (IFR) collided with terrain without having experienced an in-flight loss of control; 21 (36%) of these accidents involved multi-engine aircraft of which almost half were crewed by two pilots. Also, these CFIT accidents occurred mainly to commercial and more senior licensed pilots qualified for flight in Instrument Meteorological Conditions (IMC). None of the CFIT accident aircraft were equipped with a GPWS.
Since a large number of the accidents involved two pilot crews, the data suggests inadequacies in crew coordination and cockpit procedures for maintaining situational awareness. For GPWS-equipped aircraft, implementation of the FSF GPWS procedures, in all flight operations, is recommended.
For air carriers conducting commercial operations under IFR equipped with GPWS, it is recommended that the FSF GPWS procedures should be reflected in the appropriate company manuals.
Commercial & Business Aviation Advisory Circulars (CBAAC) are intended to provide information and guidance regarding operational matters. A CBAAC may describe an acceptable, but not the only, means of demonstrating compliance with existing regulations. CBAACs in and of themselves do not change, create any additional, authorize changes in, or permit deviations from regulatory requirements.
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