PAPI usage
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.
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...
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.
Last edited by Capn Bloggs; 4th Dec 2013 at 12:52.
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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.
From the report :"At this point, the aircraft dipped below the APAPI glide path, which if followed would have resulted in a main wheel TCH (threshold crossing height) of approximately 8 feet"
That wasn't the point I was trying to make though. I had drifted the thread a little to show how little knowledge of EWH and PAPIs, together can conspire against us Swiss cheese style. Just an example that I thought was quite interesting and (almost) on topic.
Other points from the report:
"Although consideration had been given to the aircraft's larger size in regards to ground manoeuvring, no consideration had been given to the Global 5000 greater eye-to-wheel height (EWH) and the implications of the larger aircraft flying the accustomed flight profile at CFH4"
"The profile flown on the occurrence day would have provided enough height for a CL604 to cross the threshold and land in the first 500 feet of runway"
"The crew members were also not aware that the APAPI was only suitable for aircraft with an EWH of less than 10 feet."
And finally:
"Knowledge of aircraft EWH (eye to wheel height) is necessary to assess whether a visual glide slope indicator (VGSI) system is appropriate for the aircraft type being flown. However, it was determined that this is an area that is not well addressed during pilot training and is therefore generally not well understood by pilots."
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"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."
Do every PAPI and ILS angle match? I know of at least 5 Jepp charts off the top of my head with a notation "VGSI and ILS glidepath not coincident", wouldn't that mean they're not the same or am I misunderstanding the note?
Do every PAPI and ILS angle match? I know of at least 5 Jepp charts off the top of my head with a notation "VGSI and ILS glidepath not coincident", wouldn't that mean they're not the same or am I misunderstanding the note?
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Slide:
You understand the note.
Do every PAPI and ILS angle match? I know of at least 5 Jepp charts off the top of my head with a notation "VGSI and ILS glidepath not coincident", wouldn't that mean they're not the same or am I misunderstanding the note?
You understand the note.
Do every PAPI and ILS angle match? I know of at least 5 Jepp charts off the top of my head with a notation "VGSI and ILS glidepath not coincident", wouldn't that mean they're not the same or am I misunderstanding the note?
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In VASI days, at airports with a a mix of medium & heavy, there would often be 3 bar VASI's. The big boys flew the far 2 and the little'ns the front 2. I was told by a local XAA man, when discussing the local major airport settings of PAPI's, that the airport management could set them to the requirement for the most common type or the most critical type etc. As there were many B747's there it was the norm for B737's to fly the ILS G/S with 2R 2W down to about 500' and then end up with 3R 1W. It was clear that if you rose up at 300' to 2R 2W you landed long in B737. Thus some used to accept 3R 1W in lower levels, but personally I chose the ILS G/S all the way as reference with the F/O's shouting " 3 reds". This caused much debate with F/O's and even the training dept didn't come out with definitive guidance. It was further confused by the base training TRE's saying you must fly the PAPI's 2R 2W down to 100'.
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So basically same angle, different TCH?
Angle would be as published for each individual item, which can be the same, but doesn't have to be.
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"Angle would be as published for each individual item, which can be the same, but doesn't have to be."
Some more research seems to point at (at least in ICAO world) Annex 14 being a controlling document and it seems to indicate that for precision approaches they are, for non-precision they don't have to be?
Looking at the ones with the notation on the Jepp charts about non-coincidence that I've quickly gone through the PAPI and ILS glideslopes have been the same, just different TCH - but that sample isn't by any means exhaustive.
Some more research seems to point at (at least in ICAO world) Annex 14 being a controlling document and it seems to indicate that for precision approaches they are, for non-precision they don't have to be?
Looking at the ones with the notation on the Jepp charts about non-coincidence that I've quickly gone through the PAPI and ILS glideslopes have been the same, just different TCH - but that sample isn't by any means exhaustive.
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Bloggs:
It means the glidepath angles are different. The GPIs could be the same, or different, as well.
My understanding of "Not coincident" is that the GPI for each is different, not different approach slopes. My understanding of "Not coincident" is that the GPI for each is different, not different approach slopes.
It means the glidepath angles are different. The GPIs could be the same, or different, as well.
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Originally Posted by dirtyrat
OP is quite right to ask in my opinion.
I can't answer your question with any wisdom but 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.
My company operate jet charters to main intl airports as standard, but also occasionally to small airfields where PAPIs have been setup for smaller aircraft. The example below is always brought up during our recurrents.
Go easy on me please!
I can't answer your question with any wisdom but 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.
My company operate jet charters to main intl airports as standard, but also occasionally to small airfields where PAPIs have been setup for smaller aircraft. The example below is always brought up during our recurrents.
Go easy on me please!
Of course, anyone should recognize that the position of the airplane is of paramount importance when approaching to land – it is also true that the relative positions of the various aircraft sections (i.e., nose, tail, fuselage, wings, wing tips, landing gear, etc.) are every bit as important. In the two aircraft positions presented in dirtyrat’s post, it is fairly easy to see that the cockpit windows of each of the superimposed aircraft are in essentially the same location – fore-aft and up-down … I’m not at all sure if they are the same with respect to left-right, in that the aircraft in the “low” tail position, appears to be a lot closer to the camera lens than the aircraft in the “higher” tail position ... however ...
Everyone should be aware of what the correct landing attitude should be – that attitude is the “level flight attitude” for the existing weight and airplane configuration at the Vref airspeed. Clearly, the airplane in the “tail low” position is not in the proper attitude for landing – regardless of what the VASI or PAPI lights are indicating. That is the likely place to start a critique for the pilot who was at the controls of this particular airplane – either that pilot had some distraction or awareness difficulty that should have dictated a go around long before getting to this depicted point OR that pilot has no idea of what he/she is flying – and likely knows little, if anything, about landing an airplane.
Also, we should recognize that pilot eye height is a pilot seat position within the respective cockpit (again – fore-aft, up-down, and whatever left-right adjustment may be available) and it is to help ensure that adequate visual references will be available when getting to the point that the pilot will be flying with respect to strictly visual cues. Of course that will be heavily dependent on the pilot having the airplane itself in the proper attitude – otherwise, without being in the proper attitude, where ever the pilot’s eye is positioned in the cockpit will have little relevance to what is happening on the outside of the airplane. We have adjustable seats so that pilots are able to achieve the proper eye position, regardless of his/her own physiology, designated for that airplane. That means, a pilot should not only use the alignment indicators, but should also check the other references he/she is accustomed to using – vision over the control wheel or control wheel hub … visual capability (or lack thereof) down the top of the glare shield, the amount of windshield frame that is visible, the amount of airplane nose that is visible (if any), etc., etc. Even if the pilot of the airplane in the accompanying superimposed picture with the tail low had his/her own eye position “nailed” at the correct position within the cockpit – there is no way that pilot would be able to see the outside environment anywhere near what should have been visible. With such a nose high attitude it is very likely that the pilot would have had difficulty in being able to see the departure end of the runway … let alone the landing area of the runway on which he/she was preparing to land. Not being able to see where it is on the runway you are going to land should be a dead give-away (pun intended!) that something isn’t right. In this particular case, someone, should have recognized this developing scenario long before the airplane reached the position depicted in this photograph.
I wouldn't put too much credence in the fact that VASI or PAPI lights can miss-lead a pilot to the degree that he/she could correctly use those visual aids and still wind up in the position indicated by the aircraft with the tail low in this photo. This pilot obviously had other, rather distinct areas where his/her attention, recognition, and/or piloting response was severely lacking! Aviation is not everything in one basket - just like its not just airspeed or not just altitude or not just power setting ... there are a multitude of factors that all have to be taken into consideration - all have to be managed - and they all have to be monitored and corrected when, where, and HOW ... as it becomes necessary to do so.
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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.
The optimum is 3°, but it is often higher/lower depending on obstacles and intended use. Frequently, there is a difference in the GPA, because of the obstacle clearance surfaces and the respective procedure.
In the US, I actually find the non-coincident comment very often, the recent events at SFO have brought this to the forefront.
Originally Posted by Air Rabbit
I wouldn't put too much credence in the fact that VASI or PAPI lights can miss-lead a pilot to the degree that he/she could correctly use those visual aids and still wind up in the position indicated by the aircraft with the tail low in this photo. This pilot obviously had other, rather distinct areas where his/her attention, recognition, and/or piloting response was severely lacking! Aviation is not everything in one basket - just like its not just airspeed or not just altitude or not just power setting ... there are a multitude of factors that all have to be taken into consideration - all have to be managed - and they all have to be monitored and corrected when, where, and HOW ... as it becomes necessary to do so.
Originally Posted by Underfire
The diagram is coincident, both the ILS and PAPI are set at 3°. The diagram shows where the points meet, when and how they diverge.
All this talk of changing visual slope indications on short final depending on what type one is in is ironic; we had a T-VASI, where one could accurately fly a constant picture, 3° slope to the runway to a GPI of your choice. 747 could fly 2 light high to match the pilots eyes with the ILS GS, a bugsmasher could fly 2 lights low and land on the piano keys. Alas, it fell out of favour for the cheaper (and nastier) 4-box PAPI.
Originally Posted by Aterpster
It means the glidepath angles are different. The GPIs could be the same, or different, as well.
I had a look at SFO 28L on Airnav: both the ILS and the VASI are 2.85°, and the note says they are not co-incident. Why? because the MEHT is...64ft vs the ILS TCH of 53ft, around 200ft different on the ground.
I'm ready for a look at an airport that has PAPIs set to a different angle to the ILS...
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I think Albury was the only PAPI that I have flown in to, or toyed with on an approach.
the papi is off to the left of the strip and I found that at a point near the initiation of the flare the papi indicators vanished out of my left side field of view.
In the discussions I've read here there seems to be the thought that the papi is available as a reference all the way to touchdown.
surely this isnt the case.
surely the positioning of the lights means that for all pilots they vanish from view at about the point where you'd flare for touchdown.
they are after all only a guide as to approach angle.
the papi is off to the left of the strip and I found that at a point near the initiation of the flare the papi indicators vanished out of my left side field of view.
In the discussions I've read here there seems to be the thought that the papi is available as a reference all the way to touchdown.
surely this isnt the case.
surely the positioning of the lights means that for all pilots they vanish from view at about the point where you'd flare for touchdown.
they are after all only a guide as to approach angle.
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Using a papi to touchdown would need a strong landing gear and very forgiving passengers as an ILS would if followed to touch down. You are right of course, you would never use either after 50 ft. Once over the runway at 50 ft neither one is of any use.
Originally Posted by OK465
Visual slope indicator: 4-light PAPI on left (3.06 degrees glide path)
Glad to oblige.
Glad to oblige.
How about 2.85° vs 3°, or something meaningful in the terms of this discussion?
Note 34L is also "not co-incident" but both PAPI and GS have same slope, 3.54°, but different GPIs.
Next?
On the 320, our procedure is to follow the Glide slope where there is one available in precedence to the PAPI/VASIS because they often do not coincide. Within our network this is easy enough as there are no glide slopes that have a TCH less than 50 feet.
In relation to a VASIS (albeit quite different to a PAPI) our wheel crossing height is 25 feet for a full flap landing with an eye height of 50 feet.
There are some VASIS' in our network that would have our wheels crossing at less than this 20 feet minimum, which, understandably, the company is not happy with. Therefore with said VASIS we will fly with one dot fly down or one dot high, indication and brief accordingly.
Due to the inaccuracies of visual approach path indicators we are instructed that their use below 200 feet is not recommended
What I have found to be a more useful in the late stages of approach, assuming reasonably flat ground on the approach to touchdown. I listen for "One hundred" (RA callout) and look where you're subsequently positioned, you'll start to get a good sense of when the "fifty feet" is going to be called out early or late. Ideally you'll hear it precisely as you passover the piano keys whether you can see them or not, you will know where they are.
In relation to a VASIS (albeit quite different to a PAPI) our wheel crossing height is 25 feet for a full flap landing with an eye height of 50 feet.
There are some VASIS' in our network that would have our wheels crossing at less than this 20 feet minimum, which, understandably, the company is not happy with. Therefore with said VASIS we will fly with one dot fly down or one dot high, indication and brief accordingly.
Due to the inaccuracies of visual approach path indicators we are instructed that their use below 200 feet is not recommended
What I have found to be a more useful in the late stages of approach, assuming reasonably flat ground on the approach to touchdown. I listen for "One hundred" (RA callout) and look where you're subsequently positioned, you'll start to get a good sense of when the "fifty feet" is going to be called out early or late. Ideally you'll hear it precisely as you passover the piano keys whether you can see them or not, you will know where they are.
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I flew an MD80 FAA technical engineer standing during a no flare landing to a Calif. hospital airport when he broke his ankle with the impact. The FAA pilot did the landing on a max GW landing test and exceded the descent rate slightly at Palmdale and we flew him from Fox field to SNA. Unfortunately he left his shoe in the Citation Jet so had to deliver it to him the next day. I think that landing broke the fuselage behind the wing and almost fell off back in the 70's.