PAPI guidance below 300 ft
During flight calibration testing of visual approach slope systems, the relevant technical manual used by technical staff when these systems first were introduced, stated that these systems were not intended for use below 200 ft. The reason given was the aircraft should have been stabilised on a visual approach well before reaching 300 feet and that it was not possible to ensure the light signals gave accurate readings below that height. This was due to siting of the light boxes to one side of the runway giving rise to a lateral error.
It is common to see pilots using these systems for guidance well below 200 feet. Not only that, but pilots but still calling if the signals show below or above on slope when below 200 ft resulting in superfluous "support" calls that are both annoying and distracting.
There must be a cut-off height on short final where visual signals become invalid. Can anyone quote that height from an official document?
Further to that. Most international runways (in Australia, anyway) served by PAPI, have a published mean eye height over the threshold (MEHT) eye height over the threshold for long bodied aircraft types. Typically 74 feet. This invariably means a smaller type (737, A320 et al) using the ILS electronic glide slope indication will see three or sometimes four reds on a PAPI that is calibrated for long body types (B777 and similar length). If a smaller type is now using PAPI guidance solely, (ILS inoperative or not installed) does this mean that using the normal two reds and two whites will of necessity place that type higher over the threshold than desirable?
If that statement is true, then what combination of red/white visual signals should be tracked in order to produce the normal 50 feet wheel height over the threshold for (say) 737/A320 types. Appreciate quotes from relevant official documents.
Last edited by A37575; 15th Jun 2015 at 13:02.