Minimum height to use VASI/PAPI etc?
Thread Starter
Joined: Apr 2003
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From: the Seven Seas
Minimum height to use VASI/PAPI etc?
Is there a minimum height below which you don't have to follow the guidance from PAPI/VASI and other visual path lights?
If memory serves me right I heard some numbers years ago saying some systems should not be followed all the way down to touchdown?
If memory serves me right I heard some numbers years ago saying some systems should not be followed all the way down to touchdown?
Per Ardua ad Astraeus
Joined: Mar 2000
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From: UK
Joined: Jul 2003
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From: An Island Province
Capt. Haddock for the old style VASI the minimum use ht was 2-300 ft as below that ht the light beam diffused into red/white/pink and was of little value. The effect worsened in rain / fog. Note the confusing terms used worldwide, where some PAPIs are known as PAPI/VASI.
PAPI in theory could be used down to touchdown as each lamp has a sharp transition between red and white; in practice, the pilot’s attention is transferred more towards the runway at altitudes below 200 ft. In some research applications, PAPI has been used to touchdown like a ‘carrier’ landing. The capabilities of the PAPI vary with the installation and equipment quality. i.e. the PAPI should be closely aligned with the instrument glideslope, the accuracy depends on the angular setting between each lamp unit, and the quality depends on the lamp / lens design and manufacture.
I suspect that the hard line 'don’t use below 200 ft' could be a hang over from VASI, however it’s still good advice, but don’t close out any options for using PAPI (use peripheral vision) below 200 ft it may just detect a late sink, windshear, etc.
PAPI in theory could be used down to touchdown as each lamp has a sharp transition between red and white; in practice, the pilot’s attention is transferred more towards the runway at altitudes below 200 ft. In some research applications, PAPI has been used to touchdown like a ‘carrier’ landing. The capabilities of the PAPI vary with the installation and equipment quality. i.e. the PAPI should be closely aligned with the instrument glideslope, the accuracy depends on the angular setting between each lamp unit, and the quality depends on the lamp / lens design and manufacture.
I suspect that the hard line 'don’t use below 200 ft' could be a hang over from VASI, however it’s still good advice, but don’t close out any options for using PAPI (use peripheral vision) below 200 ft it may just detect a late sink, windshear, etc.
