ramblingafter.substack.com/p/the-killer-threat-of-ais-that-over
1 correction found
the aircraft was not equipped with either a radio altimeter nor a ground proximity warning system, forcing the pilot to navigate instead by GPS coordinates.
This overstates what those missing systems do. A radio altimeter and GPWS are terrain/height warning aids, not primary navigation systems, and the crash report says the aircraft was otherwise properly instrument-equipped.
Full reasoning
The Transportation Safety Board of Canada report does not say the pilot was forced to navigate by GPS because the aircraft lacked a radio altimeter and GPWS.
Instead, the report says:
- the aircraft was "certified, equipped and maintained" and "had the instrumentation required for instrument flight";
- it was equipped with a GPS;
- it was not equipped with a radio altimeter or GPWS;
- those missing devices could have warned the pilot that the aircraft was dangerously close to terrain.
That matters because a radio altimeter measures height above the terrain beneath the aircraft, and GPWS/TAWS provides terrain warnings. They are safety/alerting systems, not the thing that normally replaces all other navigation.
The TSB’s causal discussion is narrower: the pilot evidently used the GPS, and the waypoint for the crater was entered incorrectly by 2.5 nautical miles, which may have contributed to loss of situational awareness in poor visibility. But that is different from saying the lack of GPWS or a radio altimeter forced GPS navigation.
So the article incorrectly describes the function of those systems and overstates their relationship to the pilot’s use of GPS.
3 sources
- Aviation Investigation Report A96Q0076 - Transportation Safety Board of Canada
The aircraft was certified, equipped and maintained in accordance with existing regulations... had the instrumentation required for instrument flight... was not equipped with a radio altimeter or ground proximity warning system (GPWS)... These devices could have warned the pilot that the aircraft was dangerously close to the terrain.
- FAA-H-8083-15B, Instrument Flying Handbook
A radio altimeter... [shows] height above the terrain directly beneath the aircraft... GPWS uses the radio altimeter, speed, navigation and air data... [to provide] aural and visual warning.
- AC 23-18 - Installation of Terrain Awareness and Warning System Approved on Part 23 Airplanes
Terrain Awareness and Warning System (TAWS): A system that provides the flightcrew with sufficient information and alerting to detect a potentially hazardous terrain situation and so the flightcrew may take effective action to prevent a CFIT event.