Need PPruners help

[De Regulator]

An extract from an operations manual for a private category tri-jet operation regularly using London City: 'The general notes on arrival as published by Jeppesen, advise that aircraft should at no time 'be lower than the approach path that would have been followed when using the ILS glidepath', i.e. 5.5 degrees. In practice, when visual and below the Decision Altitude, it is acceptable to 'duck' slightly under the glideslope in order to touchdown as close to the threshold of the runway as is practical and safe. A PAPI indication of three reds and one white can be aimed for initially and four reds is acceptable just before touchdown.'
Could you please comment as to legality of this practice and the good piloting sense of it. Think this needs changing. Your help appreciated.

[G-SPOTs Lost]

Seem to remember something about this, NJE used to use a similar procdeure to allow greater landing weights on on of the fleets. PAPI's are configured to a certain eye height, and smaller aircraft close in and 2 whites/2 reds are in effect where a 146 should be.

It cost a small fortune to certify and it may be that the other operator is piggybacking on the process. Of course if thats not the case and its a non legit 3red 1 white approach then it comes down to pilot ability which is difficult to quantify its not necessarily unsafe.

Remember the Iberia A340 that went of the end of a 10k foot runway after "going for the numbers" in south america somewhere.

[CJ Driver]

Keep it steep

You need to be very clear about what technique they are suggesting. The runway at LCY is short. The only reason it is adequate is that, in general for the types approved for LCY ops, if you arrive steeper, the landing roll is shorter. Your "normal" landing distances are based on a 3 degree arrival. If you look at the same aircraft landing distances for a 5.5 degree arrival you will find that you need less runway (although you land with more of a crunch!). Thus it is a big no-no at LCY to try to "correct" the sight picture by dropping below the 5.5 degree glideslope and turning it into a 3 degree arrival on final, because you will use more runway that way - possibly more than there is available to you.

On the other hand, if you are worried about landing too long, then on very short final (already established at 5.5 degrees) you can aim for the piano keys which will involve a brief INCREASE to the approach angle to 6 degrees or more - and you will then probably see 4 reds. You will also probably pull off a rotten landing, and wonder why you tried so hard - after all, the certification numbers were all done for the glideslope that exists, and they do work if followed carefully.

[merlinxx]

The folks at Dassault have the vids from the certification procs, suggest you ctc them to see if you can obtain and shufty PAPI on those approaches.

[Miles Magister]

PAPI

De Reg

There are no legal issues at all about going into 3 or 4 reds. It is up to the pilot to cross the threshold at a safe height.

As CJ so very well explained if you end up coming in at an angle less than 5.5 you will increase your landing roll. The ideal would be to come over the threshold exactly at the threshold crossing height specified in the AFM steep approach supplement performance section at 5.5 deg and exactly on speed. The PAPIs are only a guide, all be it a good one.

There are no legal reasons to prevent you coming in below 2 reds in normal ops and if you look in the CAP 168 there is a fairly simple diagram which shows your clearances when on the PAPI path. Indeed if you are on the PAPIs you will quite probably come over the threshold at a height higher than your AFM specifies (usually 50 or 55ft for part 25 a/c on a 3 deg app) which will result in a LDR longer than your AFM performance figures.

I often drop below 2 reds on normal operation on shorter runways once visual, stable and after having briefed that I am bringing the touchdown point closer and the Co has acknowledged as happy. Remember the EGPWS modes.

Landing high and fast has become fashionable, in my person opinion only, after CRM lessons showed 90 odd % of CFIT accidents in the late 80s and early 90s were within a couple of miles of the threshold. So people come in high and fast thinking it is safer, now most accidents are people going off the other end.

The best way is to cross the threshold at the height specified in your AFM at Vat. Be accurate and stable. Some app charts show the threshold crossing height when on the ILS or PAPIs. Please check your Jepp legend for details.

What ever you do make sure your crews are trained for it and practice it.

Train as you operate and operate as you train.

I was lucky in that Auntie Liz taught me to touch down on the piano keys every time. So I am comfortable and it is safe if you know what you are doing and maintain practice. However I have not done this for a long time. I try and make sure I am on speed at the correct threshold crossing height.

MM

[De Regulator]

Thanks to you all for taking the time and effort to reply. There is an FDM programme in use that bears this out (landing long), but the 'one's in authority' have rubbished it to the point of discrediting the work of the analyst preferring to do it their way.

Are the noise abatement procedures mandatory at London City; they do imply that you should maintain a glideslope at all times, which is another avenue to attack this with?

Keep the comments coming, there are bigger brains than mine out there!

[Kent BeTrue]

Hi, could somebody explain to my poor tired brain why a touch down at, for example, 120 kts after a 3 degree glideslope would require more landing distance than a touchdown at 120 kts after a 5.5 degree glideslope.
I would have thought it was all about brake energy after touchdown.
Or am I just missing the point?

Thanks
Kent

[Sepp]

If you're aiming to cross the threshold at the same height in each case - say the EU-OPS 50 ft for perf A a/c* - and assuming you follow the slope all the way to the surface:

with a 3 deg gs you'll touch down 50/tan(3deg) ft down the rwy; i.e. aprx 950ft.

with a 5.5 deg gs you'll touch down 50/tan(5.5deg) ft down the strip; i.e. around 520 ft.

Thereafter, your rollout ought to be the same, for a given set of conditions.

Steep approaches iaw EU-OPS can also be certified with screen heights less than 50ft**, gaining you even more in those cases.

*OPS 1.515, for those that are interested.
** App 1 to OPS 1.515(a)(3)

I recognize that the original poster mentioned a positioning flight, so it doesn't require to adhere to the EU-OPS criteria.

[Taxi2parking]

G-SPOTs lost

I think you may be misinformed about NJE at city - or are you thinking of SLOs at other places?

[Kent BeTrue]

Thanks for that Sepp.... I was focusing on roll out based upon the idea of dipping below the glidepath on short final, not sticking with the gp all the way to touchdown.

[Sepp]

I suppose that I ought to add a caveat to the effect that that the slope arithmetic I describe above is horribly simplified, and ignores several factors that are present in the real world. The general principle holds, however, even if the resulting distances aren't quite right.

[Zorst]

But, if the objective is to be conservative, ie; a slightly lower TCH at a slightly shallower angle at slightly earlier touchdown point, then (within the scope of good airmanship and normal judgement) this can only be a good thing.

No. Stick to the SOPs.

If you do the above, your rollout will be longer, your 'touchdown scatter' increased beyond the manufacturer's criteria, your landing performance invalidated, and your chances of an overrun increased. Oh, and you have also invalidated your insurance by deviating from the flight manual.

If your pilots (or you) are not trained enough, able enough, or indeed man enough, to do LCY properly and by the book, they shouldn't be doing it at all...

[tommoutrie]

Chaps

There's a bit of physics missing here. The arrival from a 5.5 degree glideslope does not give you a shorter landing roll. The factors that affect the landing roll are how hard you stand on the brakes, the coefficient of friction between the tyres and the tarmac, whether it's contaminated, what the headwind is, and a few others but none of them are how steep the approach is. The reason you get a shorter landing distance if you make an approach at 5.5 degrees is that the landing distance is from a screen height and the bit in the air is shorter if your approach is steeper. The idea that you "scrub off" energy by crunching it in is one that a former training captain at my company tried to promulgate and it is absolute rubbish. If you land heavily enough to have dissipated a significant amount of energy through the landing gear you will need to have the aeroplane checked for a heavy landing and you'll probably be getting the DLR home. If you are making approaches into London City, or indeed any other short runway, it it perfectly acceptable to land at the threshold rather than where the glideslope intercepts the runway. Stable approach, accurate speed control (I work on up to +3kts of Vref(s) unless its really gusty), normal flare (albeit you rotate the aircraft more because you are approaching from a steeper angle), normal touchdown attitude, normal braking. If you are fast at 50' throw it away. People screw up at City because they are too fast. This has worked for 47 approaches into City for me, has worked for everyone I cleared into City, so it should work for you.

[xsbank]

I am new to London City and have so far only arrived in the (Level D) simulator. The stable, speed-controlled approach 'usually' results in landing somewhat longer than desired because the steep-approach 'picture' is different than 99% of the places that we usually land. Therefore the tendency is to hold it off with a more aggressive flare and prolong the flare rather than plant it and so the useful runway rapidly disappears under you and you land long. The 'technique' that seems to allow more consistent arrivals (not equipped with a "legal" AOA gauge) is to do as described above, slightly duck under the glide slope and using the PAPI, land on the leetle triangles. So far, this 'technique' has resulted in more consistent arrivals and more closely approximates how I used to do STOL landings in a Dash7 (which was designed for London City - or was London City designed for the Dash?). The caveat is that an even steeper approach requires an even more determined flare (increased kinetic energy to dissipate) and therefore a higher opportunity to pooch it and alarm the passengers.

Anyway, ducking under is a technique, not a procedure and it is up to you to determine if your operation permits such things and whether or not it is even legal. Maybe you need to decide if you should even be there in your mega-jet?

If manufacturers would just add a useful AOA gauge when they certify for higher approaches (or just buy the HUD - go ahead, you know you need it) then that would make for better consistent steep approaches.

Edited to add - if in doubt, there is always ".....Go around check thrust flaps 20 positive rate gear up....."