PAPI usage
 

Hi Folks,

Can anybody direct me as where to find the reference untill what altitude/height we can use the PAPI. Close to touchdown there can be a big difference between a B747 and a C172 on the visual segment just before touchdown.

Thanks!

PAPI usage
 

Makes no active difference. Of course you are right that the system is designed to a mean eye height above the wheels, but if you're still fixated on them for the last hundred or so feet, I'd suggest you need to go back and revise your basic flying skills.

PAPI is an aid to get you from an NPA to the visual segment, after this we use the aiming point (big white markers) for the last bit.

In theory there is no minimum height due to the way that the visual beam is created; it is projected via a focussing lens.

Visual segment is defined by the glare-shield cut-off angle, aircraft attitude, and slant visibility; perhaps this isn’t the term you require.

The important difference, as above, is in the wheel-to-eye height which determines the wheel-height over the threshold. At some major airports, there is a second set of PAPIs installed further into the runway for long body aircraft, following these better optimises the threshold crossing height.

Better question would be not until when, but FROM WHEN can we use them?

It's been discussed before in here somewhere, but makes for ever so interesting reading,:8

hi

I just read this somewhere recently...the reason vasi was abandoned and papi was started.

seems to me that 50' was when papi gives out for practical use

try looking up the US Aeronautical Information Manual online and then looking up airport lighting.

you could also look up PAPI in google

I offer this only from memory, as someone who flys should actually take the time to look it up himself.

some papis have limits placed upon them for specific airports due to terrain near by. I"ve seen one as four miles.


good luck, and learn to find your spot

oh, ok, read about it here and why VASI was done away with

Precision approach path indicator - Wikipedia, the free encyclopedia

Apologies to you Air Engineer, and the other blokes genuinely trying to help you with your post.....

You ask an innocent enough question, and the first reply (#2.....from the Minister in charge of all things aviation...in Vienna) offers no helpful information at all, tells you what you already know, and concludes with an insult regarding your general abilities in an aeroplane.

This, unfortunately, is what you tend to get from PPrune these days.

From the A330 FCOM, Supplementary procedures, Navigation:

Approach on PAPI or TVASI

Eye to wheel height on approach is 32ft and minimum recommended wheel clearance over the
threshold is 20ft. Do not follow Precision Approach Path Indicator (PAPI) or “T”- Visual Approach Slope Indicator (TVASI) guidance below 200ft when PAPI or TVASI Minimum Eye Height over Threshold (MEHT) is less than 52ft.

PAPI is a guide, not a requirement - as such you may use it to guide your actions any time you can see it.

As any guide, you don't use it exclusively - so you don't allow it's errors or limitations to affect your safe landing.

Usually from people who don't know the answer to the question.....

I recall that the DCA Flying Unit in the old days tested the T-VASIS for flyability down to 200 feet. It was assumed that no pilot would want to follow the lights any lower since it was a visual guide not a category 2 or 3 ILS.

For the same reason you should never consider switching from the ILS at Cat 1 height of 200 ft to the PAPI since the electronic glide slope is already there to give guidance.

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!


http://www.tsb.gc.ca/eng/medias-medi...34_photo_5.jpg

Anyone interested, accident report here: Transportation Safety Board of Canada - Aviation Investigation Report A07A0134

Hi Air Engineer, I think it all depends upon what you are flying and at which airfield.

If for instance you are flying a Husky from Doncaster, you have enough room for... A Take-Off,,, Practice EFATO,,, Touch and Go,,, and still have runway left over.
The PAPIs are mostly aligned for CAT landing well into the runway, and most GA aircraft want to be on the ground well before that.

Gliders in particular, practice landing as close to the Threshold Hedge as possible as they are often faced with land-outs in some very small fields. The aiming point is often in the field before the landing field, with the flare occurring just over the hedge.

The geometric PAPI 3 degree glideslope obviously terminates at the PAPI installation. For a CAT airplane the height of the Pilot's eye-line is many feet above his wheels, so the wheels can touch down many metres short of the PAPIs. That is why the PAPIs are several hundred metres up the runway from the threshold.

From flarepilot's wiki link - PAPI to flare (usually 50' ).

VASI designed for use down to 200' (but they worked much lower).

Amazing how often the PAPI's aren't aligned to the glideslope or vice versa... Makes you realise very quickly that they are a reference guide. I was always told not below 200ft in the jet

From the FAA AIM Chapter 2. Aeronautical Lighting and Other Airport Visual Aids

b. Precision Approach Path Indicator (PAPI). The precision approach path indicator (PAPI) uses light units similar to the VASI but are installed in a single row of either two or four light units. These lights are visible from about 5 miles during the day and up to 20 miles at night. The visual glide path of the PAPI typically provides safe obstruction clearance within plus or minus 10 degrees of the extended runway centerline and to 4 SM from the runway threshold.

EDIT: from different source... The VASI only provided guidance down to heights of 60 metres (200 ft) whereas PAPI provides guidance down to flare initiation (typically 15 metres, or 50 ft).

So that looks like it covers both parts of the question, as others stated, down to 50 ft and out to 4nm...

This diagram from a design manual may be helpul as to why there are differences.

http://i43.tinypic.com/2laq3rn.jpg

distances:
http://i40.tinypic.com/dpkaro.jpg

I can't believe a pilot would link to that wikipedia page. I tend to look a long time for more reputable sources before checking wikipedia but even I'm surprised at that entry. I'm guessing the entry was done as a junior high project.

I can't believe that Canada didn't have LLWS alert system

I offered the wiki link as a quick answer to the question, I also indicated that checking the AIM would be a good idea too.

Thanks all for your inputs and thoughts.

PAPI usage
 

Castle don, I don't see any as hominem attacks until you stuck your head up. I say it as I see it, note the word 'suggest' being used.

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.

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. :=

Agree, but only just 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."

"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?

Slide:



You understand the note.

My understanding of "Not coincident" is that the GPI for each is different, not different approach slopes.

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'.

"My understanding of "Not coincident" is that the GPI for each is different, not different approach slopes."

So basically same angle, different TCH?

Not necessarily, just different location for TD point if followed to GRND.
Angle would be as published for each individual item, which can be the same, but doesn't have to be.

"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.

Bloggs:



It means the glidepath angles are different. The GPIs could be the same, or different, as well.

While the concept of superimposing the profile of 2 different aircraft positions and ensuring that the pilot-eye-point (i.e., cockpit window) of each is in essentially the same location can be very enlightening, I think this kind of presentation deserves just a couple of comments …

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.

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.

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.

The real story of Fox River:

http://i521.photobucket.com/albums/w...pscc16427b.gif

The centre of that PAPI beam (ie half way between angle C and angle B) is not parallel with centre of the ILS GS. Angle C is parallel with the GS; that diagram indicates that that PAPI is set at 2.75°. They are neither coincident in angle or GPI.

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.

What would be the point of having different angles? There is obviously a logical reason for different GPIs and the same angle, but I cannot see why you'd want different angles.

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...

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.

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.

And the ILS is 3.1°? Hardly "different".

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.

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.