Line up technique

[squawkident.]

Hello all,

Am just wondering your thoughts on efficient line up technique.

Assuming a 90 degree line up with take off clearance received, is it better to enter the runway perpendicular to the take off direction and overshoot in the line up. In effect to try and minimise the line up distance used and maximise available runway available?

OR is it better to follow the high speed centreline, stand 'em up and continue a rolling takeoff.

The second option uses much more runway than the first before the application of take off power BUT the aircraft already has forward momentum. Does this forward momentum equate to reducing the runway required over the 90degree line up technique.

[cosmo kramer]

The second option uses much more runway than the first before the application of take off power BUT the aircraft already has forward momentum. Does this forward momentum equate to reducing the runway required over the 90degree line up technique.
The general answer is no. It is more efficient to line the aircraft up properly. Hence, the performance data is based on a proper line up.

However, in your question there are a 1000 variables. SOMETIMES is might be more efficient to make a rolling takeoff. Depending on the turn required etc. Even tough you have momentum, it will be fairly small if lining up through a 90 deg perpendicular taxiway. If lining up at a rapid exit intersection, obviously you can carry more speed onto the runway.

If your performance accounts for sloppy lineup, or the runway length is not a factor, of course you can safely do a rolling takeoff. If the runway length is performance critical, do a proper lineup coming to a complete stop before applying takeoff thrust.

Also, perpendicular taxiways never have rapid-exit taxiway lines. In any case, there is no point in following ANY taxiway exit lines, as they are just that = EXIT lines. Turn the aircraft as sharp as feasible and appropriate for the current taxi speed, disregarding the exit lines.

[+TSRA]

By god cosmo kramer, you make a rolling take-off sound as though it's dangerous and not for the feint of heart!

It is a perfectly acceptable method of taking off that is required on almost every type of runway other than pavement...that almost always requires a less than perfect ("sloppy") lineup.

All performance data I've ever used has given both static and rolling figures and in most cases the difference in distance is negligible considering the runway lengths unless you're operating at the extreme edges of aircraft performance.

So to answer the OP's question from my POV: either is perfectly acceptable given the traffic situation and aircraft performance from the runway you are using.

[cosmo kramer]

No, I was answering the original posters question "what is more efficient", not what is "acceptable" - which depends on a lot of factors. Your post was just bla bla bla.... :{

[Nicholas49]

May I ask a question? I am not a professional pilot. I have noticed as a passenger that when you perform a "rolling take-off", you start to spool up the engines before being fully aligned with the runway. I understand that the engines are spooled to a certain percentage to check that they are spooling up stably, and only after that point is take-off power set. Now my question is: do you apply take-off power only once the aircraft is fully aligned, or is it acceptable to apply take-off power while you are still in the very final stages of lining up the aircraft. Hope that's clear. Thanks, Nick

[Denti]

Our 737 FCOM says the following about rolling take off or not:

A rolling takeoff procedure is recommended for setting takeoff thrust. It expedites takeoff and reduces risk of foreign object damage or engine surge/stall due to a tailwind or crosswind.

Our performance software has as standard an option activated that calculates an increased line up allowance of roughly 100 to 120m.

Take off thrust before being aligned, especially out of a 90° line up can lead to very nasty results. However when lining up out of a rapid exit way it can be possible.

[AerocatS2A]

You probably need to define exactly what you mean by a rolling take-off. In our manuals (BAe146) the difference between a rolling take-off and a static take-off is that the power is set on the brakes in the static take-off and the aircraft is allowed to roll while the power is being set in the rolling take-off. Both take-off techniques assume the same 90º turn on to the runway though.

[galaxy flyer]

Can it possibly be this challenging?

[Piltdown Man]

First thing, do the sums. If I have a performance limited take-off, I'll gently squeeze all I can out of the runway. But I rarely am. I normally have figures worked out for intersections well down the runway. So given the chance, I do a gentle, wide radius line up, a smooth application of power into a rolling take-off. I for one don't what to be the "safe" plonker who shreds a few tyres lining up on a 3,000m runway when 1,400m was all that was required.

And Nicholas49 asked about setting power. I don't "give it the beans" until I'm pointing down the runway. Having an engine failure during a turn on the ground with take-off power set would be very embarrassing. You'd not only upset the tyres but the SLF as well. It might also be a challenge not to go gardening.

[fireflybob]

From a performance point of view it depends what assumptions are specified in the AFM.

I recall on the B737-200 the AFM stated either a rolling take off or 1.4 EPR set prior to brake release and then set take off thrust.

Usual stuff about line up allowance depending on entry taxiway or180 required for backtrack and lineup.

[Amadis of Gaul]

Can it possibly be this challenging?


To people who don't actually fly anything, yes, it can be.

[MD83FO]

somewhere on Airbus it says that 90 deg lineup puts undue stress on the mean gear. I'd like to know why, because when time permits I love using every inch of the runway.

[Piltdown Man]

I'd like to know why

It's because it does. Yanking and heaving a 50 ton plus lump of metal through 90 degrees within 22 metres is best avoided if at all possible. And I'm sure that if you ask nicely, Messrs Airbus will give you an answer as to why.