Use of PAPI

[cloudhigh]

Hey guys and gals,

The other week I flew dual and the instructor insisted on flying with those 2 whites and 2 reds all the way done however I was flying a C210 so in my mind why would I be worrying about those PAPI lights?

Having flown cubs to the baron I personally I only use them when I am on an instrument approach. Flying visually around I use judgement on my approach path. I know a few flying schools teach students to use the lights for the approach but its the old question of going into a strip that doesn't have them what will this poor student do???

Unless its an instrument approach I don't bother...
What do you do?

[ReverseFlight]

Come on, it's all about good airmanship and using all the available aids for safe flight.

It's not about being a pussy. If I were the instructor sitting next to you, how the hell am I supposed to read your mind ?

[AerobaticArcher]

Instrument or Visual approach, day or night, fly it the same way everytime, why mix it up?

[Arm out the window]

Well, for one thing, I'd prefer a steeper approach angle than the old 3 degree bum drag for engine failure considerations in a single.

[ForkTailedDrKiller]

Instrument or Visual approach, day or night, fly it the same way everytime, why mix it up? Yup! Whether flying the ILS into a 3000 m runway or going into a 300 m one-way strip out the back of Bourke, you should aim to do it the "same way everytime"!

Why mix it up? :E

Dr :8

[cloudhigh]

Not about being a pussy? So the bush pilots who don't use PAPI's are pussies?
Use all the aids you can for safe flight? So not using the PAPI's is unsafe?

Thank goodness 'Arm Out The Window' is able to put a reason behind the statement and that was exactly the mindset that I have been taught by.

Why drag your butt in when you don't need to?
I certainly wasn't questioning anyone on why they don't fly it like I would but am curious to see what advantages there are to flying a 3 degree approach all the time.

[waren9]

You do power off approaches as a matter of course then?

Its a useful tool that if you're not going to use, a quick remark to that effect to the guy next to you might be worth considering, especially if you are not PIC.

[cloudhigh]

No to the power off approaches. Still had 15-18" manifold during the approach.

You are correct in saying you should state that you are flying a higher profile which I did and he said no dramas.

[waren9]

Personally I would still take its guidance, flying 3 whites or less flap to reduce the power reqd are valid options too.

[mushroom69]

I may be wrong, but I seem to remember that there is actually a regulation that says that if a PAPI or other visual approach indicator installed, that you must follow it. Precisely because they are not all 3 degrees!

I know of at least two airports, where not following the visual approach indicator can have you greeting hi tension wires in one case, and dangerously close to the tops of trees on an island in a river just off the threshold. Pilots focus on the landing zone and "forget" about the bits sticking up....

Above and steeper is fine of course.....

Oh.......a third airport comes to mind, where the PAPI (and displaced threshold) keep you away from being too close to the elevated commuter train station. Breaking the modern stabilised approach philosophy, I follow the PAPI on that one too until past the airport fence, then increase my rate of descent, decrease power, flare adding a bit of power, and land just past the threshold.

Ono

[compressor stall]

The issue at hand was being above the 3ish degree slope. I've yet to hit a mast, a tree or even a train station being above slope...:cool:

I'd personally be deliberately above slope on a PAPI or ILS in a piston single on a nice day and descending to it or well below depending on my desired taxiway.

If your instructor was setting the exercise on a single approach to test your aircraft handling then fine. If not then I think he has a case of shiny jet envy and is trying to fly a Cessna in the way of a Boeing as that's where he wants to be. He's doing himself and his student a disservice.

As ab aside the PAPIs are in many places set up fir A380 eye height. So if you are flying them to the ground (even in a A320) you'll land a looong way down the runway.

[Capt Fathom]

Breaking the modern stabilised approach philosophy, I follow the PAPI on that one too until past the airport fence, then increase my rate of descent, decrease power, flare adding a bit of power, and land just past the threshold.

Well there's the ingredients for a heavy landing if every I saw one! :E

[Plow King]

Breaking the modern stabilised approach philosophy, I follow the PAPI on that one too until past the airport fence, then increase my rate of descent, decrease power, flare adding a bit of power, and land just past the threshold.


Wot, no Jacobsen Flare? :=

[L0u0k0e]

Flying day VFR, they're lucky if they get a second glance from me, have never really felt the need or urge to use them.

[Aussie Bob]

Sadly after holding a CPL for over 25 years I had to google PAPI to find out what the acronym was. i thought it was TVASI :ouch:

Whatever, I go with LOuO, never felt the urge ...

[das Uber Soldat]

What a bizarre thread.

[Aussie Bob]

Don't you know das uber: pilots area bizaare lot!

[scotbill]

As an ex-RAF/Private/airline IRE TRE/ driver it does seem to me bizarre if instructors are teaching students to rely on powered approaches with PAPIs - other than in practising instrument approaches.
Would it not be more useful to be teaching the differing visual cues from wide/narrow or upslope/downslope runways? How do they handle the engine failure case into an unknown field?

[fixtor]

Most likely the instructor is a low timer and was taught to follow the PAPI. I have seen instructor's that cannot land on 5000'. From 16k+ I can tell you the most dangerous time not to follow PAPI is in rain with good vis. Next time say "Visually above the PAPI" or "Visually below".

Yes, those of us who do not fly an automated bus do configure ourselves to land where ever we choose. From asphalt to Eskers.....

[Centaurus]

VASIS was mandated in Australia following several Boeing 727 approach accidents in USA after the 727 first flew. In those days, seniority reigned supreme in US airlines and so older captains who had flown DC6 and similar were automatically in line for the first of the 727 commands.

Accidents soon happened due to difference in propeller aircraft (instant power available if undershooting) and the slow spool up time of early jet engines. Hence the stabilised approach criteria came into being which included engines being spooled up in a jet to the appropriate thrust to ensure acceptable rate of descent on final. Although rudimentary VASIS had been available before advent of jets, it wasn't until Australian DCA experts perfected the T-VASIS did visual approach slope guidance get really accurate. The former red/white VASIS had serious limitations and T-VASIS was designed to overcome those.

Both T-VASIS and PAPI were designed to aid jet transport aircraft on visual glide path which used to be 2.5 degrees in the early Sixties but were later increased to three degrees in Australia would you believe for noise abatement at Sydney for runway 07. There is a long story about that but sufficient to say there were political issues involved with noise complaints under the Sydney 07 ILS. ILS glide slopes were jacked up to three degrees which gave a less noise footprint and for standardisation T-VASIS were jacked up also. I had some practical involvement with DCA in the flight calibration of the jacked up ILS and T-VASIS in 1970.

VASIS was never designed with light aircraft in mind and since these aircraft have a normal landing approach of around five to six degrees, it is obvious that three degrees is far too flat and requires significant power. About the only advantage for light aircraft using visual approach slope guidance is if the aircraft gets ridiculously low (undershooting) and the VASIS/PAPI goes all red. That happens at an angle of around 1.9 degrees which is real flat.

I believe a Thai International Boeing 777 tried that trick recently while attempting to land at night on Melbourne 34. That was enough to give any pilot the shivers.

VASIS/PAPI are not installed purely for glide slope guidance after breaking out visually from a Cat One ILS. They are nothing to do with instrument approaches. Australian regs require jet transports to have glide slope guidance whether electronic (ILS) or a lighting system. Instructors on light aircraft should certainly explain to students how to fly the VASIS/PAPI but only to point out the advantages of these visual aids for high performance aircraft that need a three degree slope as part of stabilised approach criteria.

[mcgrath50]

Also I believe the approach path of the ILS can be slightly different to the approach indicated by the visual system, ie; they can each have different touch down points, so you can be dead on the PAPIs for example, but slightly off the ILS?

[NZScion]

PAPIs can have varied threshold crossing heights (and glide slope angles) to compensate for different aircraft, as if a B747 follows the lights down with a threshold crossing height of 50ft, the gear may touch things it's not supposed to ;)

The indications from the PAPI may also be "received" a lot higher (pilots eye) than the ILS signal. This is another reason why the Threshold Crossing Height for a particular runway is varied, as PAPIs are usually configured to allow for the largest aircraft expected to normally use the field.

The issue arises when a crew in a smaller aircraft is looking at both ILS GP and PAPI indications. Each system may have different touchdown points, or it could be the difference in Threshold Crossing Heights. As previous posters have alluded to, it doesn't actually matter - as long as the pilot is aware of the potential issues and understands what information (s)he is receiving and should be looking at, there shouldn't be an issue. Large aircraft which may run into difficulties should have clear crew instructions as to what indications should be followed under what circumstances.

P.S. @Centaurus - A pilot should see 4 reds on a PAPI at an angle of 2.5° (assuming a 3.0° glideslope).

[Arm out the window]

Some good gen coming out here; thanks, you knowledgeable people.

One thing which I believe can be an issue in poor vis (ironically just when you want them to be helping you most) is refraction in misty/foggy conditions making what you see from the lights unreliable.

[compressor stall]

PAPIs can have varied threshold crossing heights (and glide slope angles) to compensate for different aircraft, as if a B747 follows the lights down with a threshold crossing height of 50ft, the gear may touch things it's not supposed to

Which is why you should know your aircraft eye height... By my reckoning if you follow the PAPI to the runway all other things equal you'll end up landing around 7 metres long per foot the PAPI eye height is above yours. ie if your aircraft eye height is 45 feet and the PAPI is 64 feet eye height you'll land ~130 metres long...