Strange SOP on how to land a 737
 

I never fail to wonder how different operators have widely varying SOP for a simple manuever.

No names of course but a SE Asian operator has a published SOP that on becoming visual on an ILS, the electronic glide slope must be abandoned and the PAPI lights followed. The fact the PAPI siting is often different to the glide slope ground transmitter due to various technical reasons, means a pilot could be flying a perfectly stable coupled approach then on seeing the PAPI he has to now to follow the PAPI which could have a siting variance. The stated theory is that the ILS glide slope is not accurate below a Cat 1 DH while the PAPI is purportedly accurate to the flare.

Flight calibration testing of a Cat 1 ILS normally continues below 200 feet to 50 feet to confirm the electronic glide slope is stable below 200 feet. If there is significant stability below 200 ft it would be subject to NOTAM. Any thoughts?

It's not just un-named 737 operators Centaurus, there are plenty of others who also mandate this idiocy, having said that, not all ILS's place you on the centreline on a nice 3 degree slope nicely in the slot to touch down in the first 1000 feet, RWY 31 in the Seychelles springs immediately to mind.

Considering most PAPI at A380 capable airports now is vastly different to the glideslope the (Australian) T-VASIS looks like a much better alternative. That is all aircraft following a PAPI will theoretically touch down at different points depending on eye position, threshold crossing height will vary depending on type. With a T-VASIS you can use dots up or down to fly a constant flight path angle for the same touch down point or TCH. For example a 737 may fly no light deviation for a TCH of 50ft and the A380 would fly 2 lights high and achieve the same approach angle and same TCH. But having a visual approach system that is compatible with the ILS system is just silly isn't it, its better to just make pilots destabilise their approach at 200 ft or less to change flight path to suit the PAPI.

Quigte honestly ANY attempt to follow a proper glidepath would be welcome, based on what I have seen over the years, be it ILS or Papi/Vasi.

Transferring to 'visual' has much merit and any difference in touchdown point will be irrelevant. will NOT seriously affect the landing PLUS it means you can fly by looking out of the window instead of at the dashboard. PLUS, of course, it is 'universal' wherever visual guidance is in place and works better on an NPA!

BOAC lets assume you are doing an ILS cat 1 approach at an A380 capable airport or other NPA with higher minima. If you were perfectly on the IFR slope at night with limited cues other than the VASIS when you become visual the PAPI would tell you you are low in most aircraft other than large aircraft. This than requires a change in power and attitude to achieve the new visual landing point. Imagine you were flying a light jet with virtually no difference between eye position and gear track as opposed to an A380. Should you fly level at 100-200 ft to achieve the correct PAPI indication or continue to land below visual slope indication. If you fly a correct approach path and speed, TCH and touchdown point should be natural. What TCH will you achieve if you fly the PAPI for an A380 in a 737? What affect does that have on your landing distance given your TCH is now way higher, do jets now have landing figures for the increased TCH?

BOAC, ILS TCH 50ft. Some PAPIs MEHT 71ft. That's a fair bit of bitumen. However, these "big jet" PAPIs are normally on long, long runways where LDA isn't an issue in a "small" jet like a 737.

Changing aimpoints at 200ft is silly idea, though, IMO. On the GS, take a snapshot at 200ft and hold it, if not ease forward a tad to counter the fright factor. :ok:

43inches of T-VASIS: way to go! Unfortunately, the beancounters think otherwise.

What is worse when a 737 crew sees a PAPI indicating low on a non A380 airstrip do you need to fly up to be safe? or is it indicating for a an A380? how do you know?

Woha guys and girls - no-one is suggesting that you should not just 'fly' a 'real' visual approach, but the OP question was about flying the ILS glideslope to TCH.

As to all the questions about A380 airports, 43/Bloggs - do you not have a landing briefing which covers PAPI appearance or do you just bowl on in and think - Hmm - more reds than I expected on the PAPIs but, hey ho.............?

In any case, no sensible pilot will 'suddenly' adjust the visual picture on transferring - there is no need. Providing the picture is 'right' you 'point' the ship at where you want to land and that is it, is it not?

It is, however, a moot point - I have lost count of the number of times I have sat and watched both 4 whites and an ILS GP pointer on the cockpit floor as we sail happily past everything, still airborne and a frantic little hand clutching for the reverser levers - aggghhhh!. Not sure what is being 'followed'. Better to concentrate on just getting the lady down at the right place than following x,y or z.

BOAC do you understand the difference between what a T-VASIS tells you and a PAPI? One is angle of decent, the other is decent path to varying TCH based on cockpit eye position. Flying 2 reds 2 whites on a PAPI maintains a descent angle to the PAPI, good luck calculating TCH. Flying any other combination leads you to the same point at a different angle. Flying different lights on the T-Vasis maintains the same glide slope angle but adjusts the TCH, a very easy calculation. You just have to adjust for eye-position or cockpit level something manufacturers can do easily. Wouldn't it be great to come out the bottom of an ILS and say 1 dot low thats what i expected rather than its all red lets fly up to the PAPI.

Yes, but I did not mention a T-Vasi!!:confused: The discussion is about PAPI.

BOAC but what is the point of systems that don't tell the truth, T-VASIS tells a pilot what they need to know, PAPI is a waste of time for accuracy. If you want to land at the best point and use the least runway T-VASIS does it for every aircraft, PAPI only tells you a point on the runway for eye position, for varying cockpit heights where the wheels will touch is the most important.

- lovely! What if there is only a PAPI? Do you have shares in T-VASI Inc?:)

The reality is that T-VASIS is only at a very few airports and reducing, PAPI is the new reality. But if you are a true aviator you would recognise that great things are often forgoten in favour of cheap things.

Have guys forgotten how to land on a runway after a 3 degree approach WITHOUT any glidepath guidance? It is after all a visual approach following he transition. Whatever happened to maintaining the correct perspective. There were, perhaps still are, many rwys without fancy lights. A B737 can get into some very tiny and interesting places. Perhaps the XAA's wouldn't licence them for commercial jet operations with no christmas lights, but then again Mk.1 eyeball should be a pilot's near and dear friend.

Thanks RAT.

Mk I eyeball below 300 feet.

I don't even look at the PAPI.

If there aint T-PAPI,I aint going:E

If there aint T-PAPI,I aint going

You must be a mama's boy.

Good!!! :D

That's was the OP's point...

Is this 'SOP' maybe in response to the recent finding on false glide slope captures from the Dutch CAA?

With a very slight change in your description of their procedure that would be a great SOP. Qantas for example, when following the ILS the crew are under instrument or low vis procedures meaning that one guy is heads up and the other must be heads down and monitoring. When visual and the handling pilot calls for 'visual procedures' both pilots are head free the implication being that the ILS guidance is now of secondary importance. This I quite like because it makes it clear by what means the approach is judged and how the responsibilities between the pilots is clearly defined.

If that is how this SE Asia operators procedures pan out then makes sense to me.