Question for pilots @ LHR

[shhhpotter]

I often have pilots ask me for full length departures, for example from 27L they will use N2W and essentially backtrack to the threshold...this perfectly acceptable in a heavy heavy as I have seen them rotate very close to the end of the rwy.
However, I have had several carriers in "mini" buses ask for full length, subsequently backtrack(as above) and depart...however my problem is that they rotate between S4-S5, this begs the question, why request full length then rotate after such a short distance...this can lose valuable seconds in a departure sequence.

[HEATHROW DIRECTOR]

Long ago there was an instruction issued to airlines that pilots were not to back-track from that turn-on, but to turn directly on to the runway. Looking back to the long-haul DC8s and 707s that really needed every inch of the runway.... they managed OK! Maybe the instruction still exists but has disappeared under the other reams of stuff?

[mr ripley]

I can only think that they have calculated their take off performance/speeds on a full length runway, then get to N2W, realise that they aren't full length and don't have the time to re-calculate.

SB1 is fine for me though.

[alloha]

I often have pilots ask me for full length departures, for example from 27L they will use N2W and essentially backtrack to the threshold...this perfectly acceptable in a heavy heavy as I have seen them rotate very close to the end of the rwy.
However, I have had several carriers in "mini" buses ask for full length, subsequently backtrack(as above) and depart...however my problem is that they rotate between S4-S5, this begs the question, why request full length then rotate after such a short distance...this can lose valuable seconds in a departure sequence.

Just performance reasons.The longest the safest.Every meter may be prooved valuable in case of an aborted TO.

[Seat1APlease]

Without knowing the airline and other details there can be no definite answer, but it may be that their performance manuals don't have N2W figures but only "full length" "Block 85"( or whatever that is called now) etc. etc.

It wouldn't be the first time that this has happened, especially if it is not their home base. Whilst some crews may use their own discretion others are more tightly restricted by their SOP's

If it is the same airline on each occasion then it might be worth contacting their LHR office and enquiring if they have the figures.

One other thought is that sometimes an aircraft will have some piece of equipment not working and the MEL/ADD/DDM book will tell the crew what restrictions are associated with it. These are generally not runway specific, and it may say, for example, that if the Autobrake on reject take off is not working then use the full length, even though in this case it is patently over the top.

[Carnage Matey!]

You could ask if they could accept departure from N2W without backtrack and if the response is negative then advise of a delay until you can fit them into the sequence. Should get them scurrying for the performance manuals.

[Gonzo]

We haven't got time for that, CM. workload on Air Deps has already increased becasue of this single conditional line-up trial! :ugh:

[Sky_Masterson]

Well, theres a saying widespread in the pilot commmunity that says "Runway behind you is Runway useless" Most of the time any GA pilot would use the entire lenght of the runway but in this case, with an airliner and a commuter airplane is unwise to reject a departure from intersection, if the conditions permit for it.

Mainly cause all are fitted with Laptops and Perfomance software in wich is pretty much staright forward to upload the re-calculated take off distance and obtain the new take off data, with the new V figures, quickly and just on the H/p.:)

Thats why theres an entry in the FMC on the departure page called "TO SHIFT".You key the new recalculated lenght on the entry and voila.., all the data re-calculated. Most commuter pilots will accept happily a shift take off.

[Hotel Mode]

All it needs is a NOTAM to remind airlines from the central area to expect N2E/W for line up. BA reminded us that it wasnt the full length a couple of months ago. Frankly the way some crews line up 27L they'll hit their wing on the aircraft at N1 before long.

[52049er]

Perfectly possible to recalculate TO perf at the hold - but is it a good idea?

I see plenty of mistakes done in the figures at the gate with 3 people on the flight deckand no interruptions, and get very nervous when we need to redo it during taxi or when ATC are trying to talk to us at the same time.

I guess its just one of those areas where our needs diverge - ATC want max runway useage, all I want is my a/c operated as safely as possible. Mind you, why anyone would want to recalculate when they already have figures for a shorter take off run is beyond me. When I was on short haul I just did the worst possible case figures and took out the shift if we were full length. If you want full length, asking for it as early as possible seems to work....

[arem]

I remember a story told me by a bmi pilot long ago - holding point 27L, various 747's inc -400's waiting. full of fuel, wings drooping, when along comes a midland DC-9, enters the runway and backtracks to the threshold - out of the ether comes a voice " bit heavy are we? " :) :) :)

[Gonzo]

Hotel Mode,

Frankly the way some crews line up 27L they'll hit their wing on the aircraft at N1 before long.

That's exactly why holding points NB2E and NB2W were withdrawn.