Differences between PAPI's
Differences between PAPI's
PAPIs are just a bunch of lights pointing up an approach slop designated by the terrain clearance in the area. Some have different slope requirements, but as they are a point source aid I would doubt that they are set for aircraft type. Imagine the politics between Boeing & Airbus for a start! 
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PAPI's. The PAPI's were probably set up to allow a large a/c to maintain a constant glidepath to the touchdown point, giving adequate ground clearance over the threshold. In a large a/c, the aeroplane is considerably behind and below the pilot (on approach), so if you flew theses papis in a light a/c, you would touch down in front of where you should.
Draw a picture ....
Draw a picture ....
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If you are in a light aircraft, do not follow PAPIs: ever: light aircraft glidepaths are steeper.
Most PAPIs are set up for standard 3 or 3.5 degree glidepaths and set up to be seen correctly from a single-deck aircraft, hence 747s often needing to look high on the glideslope with 3 whites due to the higher deck.
[This message has been edited by Lucifer (edited 28 May 2001).]
Most PAPIs are set up for standard 3 or 3.5 degree glidepaths and set up to be seen correctly from a single-deck aircraft, hence 747s often needing to look high on the glideslope with 3 whites due to the higher deck.
[This message has been edited by Lucifer (edited 28 May 2001).]
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sorry guys - but PAPI's are nearly always set to give the correct glidepath to the touchdown point on the runway, REGARDLESS of aircraft type.The only time this may not be the case is when test flying is taking place for a specific aircraft type, it is then the responsibility of the aerodrome authority and the ATCO to ensure that you are told to disregard PAPI indications.
If you encounter deviations from the correct glide path angle because of mis aligned PAPIs, tell someone immediately - you could save the next guy's neck!
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sb,
Have to agree with you on that one. I was under the impression that the PAPI's are set at a standard glideslope - 3 deg for civvy airfields, 2.5 deg for mil airfields (or at some other required glideslope). As the aircraft approaches the threshold, there is a disparity between what you would see from a 747 and a smaller a/c. However, you cannot account for this - the PAPI's themselves are set to give an accurate appproach path earlier in the approach sequence, and not at touchdown!
Regards,
Cuban_8
Have to agree with you on that one. I was under the impression that the PAPI's are set at a standard glideslope - 3 deg for civvy airfields, 2.5 deg for mil airfields (or at some other required glideslope). As the aircraft approaches the threshold, there is a disparity between what you would see from a 747 and a smaller a/c. However, you cannot account for this - the PAPI's themselves are set to give an accurate appproach path earlier in the approach sequence, and not at touchdown!
Regards,
Cuban_8
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Agree that PAPIs are set to 3 or 2.5 degrees but pilot eye height varies for different aircraft. eg L1011 30´ higher on a 74. The picture you see on the glide is not 2 red 2white but 2white 1 pink and one red.
Your eyes are a bit high but the gear is on the 3degree slope.
Your eyes are a bit high but the gear is on the 3degree slope.
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Ah! with you now - alongside the published slope angle for a PAPI, you will see the letters MEHT - Minimum Eye Height Above Threshold.
This is the lowest height at which the pilot can expect to see/receive an accurate ' on - slope' indication.
Take your point about indications at touchdown Cuban, it is the MEHT that counts.
Hope this clears the muddy waters a wee bit.
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This is the lowest height at which the pilot can expect to see/receive an accurate ' on - slope' indication.
Take your point about indications at touchdown Cuban, it is the MEHT that counts.
Hope this clears the muddy waters a wee bit.
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PAPIs are in most cases set to co-incide with the ILS GP. If the GP is 2.9 degrees, so the PAPIs be as well. The only exception to this that I can think of is some fast jet stations where the local aircraft has a flatter approach. An example of this is most RAF Tornado stations where the approach for the locals is 2,5 degrees. The ILS will invariably be 3 degrees (or close), but there is another precision approach available - the PAR (Precision Approach Radar, no longer available at civilian airfields) where the fast jets will get a 2.5 degree talkdown.
