Originally Posted by Dirtyrat
I can tell you that a hull loss occurred because of precisely this. In the picture below, look at the difference in wheel heights between the 2 bizjets for the same pilot eye heights.
There's more to that Global Express prang than you make out. They were low on the PAPI, slow and going lower. Had they been on slope (even though one of the lenses had "sunk" 0.1°) they would have been OK.
The critical issue with all PAPIs is the published eye height verses your eye-to-wheel height.
I would hazard to say landing a Global on that runway, in those conditions, with 65 hours in command on type and an FO with similar type experience was always going to be an high risk event.
Also, that photo is misleading: it shows the Global with an apparent deck angle of around 8-9° (although the red line isn't aligned with the windows). That was the result of a snatch-pull just before impact, not a steady-state approach. You should have posted the previous pic, which shows how much wheel-height clearance they would have had (enough) if on-slope on the PAPI and on-speed.
There are lessons to be learned from that prang for sure, but unless a PAPI is placed at a very very short distance from the threshold, it will always keep you out of trouble if you stay on it.
Originally Posted by 3bars
Amazing how often the PAPI's aren't aligned to the glideslope or vice versa...
It's not amazing at all. 60-70ft MEHT are commonplace here, so long-bodied pilots get 2 reds and 2 whites when tracking the ILS GS (antenna being lower on the airframe than the eyes). This is on fairly long runways so for smaller aircraft, any difference between the PAPI and the ILS GS is irrelevant in respect of landing performance.
Underfire, that diagram has to be wrong; every PAPI on an ILS runway that I know about has the same angle eg 3°. That diagram clearly shows the PAPI path is much less than the ILS GS.
I've made a spreadsheet that can be used to illustrate the differences between the PAPI and ILS GS by playing around with the different TCHs and MEHTs. If you don't have the MEHT but know where the PAPI is located, you can work backwards.
https://dl.dropboxusercontent.com/u/...une%20MEHT.xls
NOT FOR OPERATIONAL USE.
