PDA

View Full Version : how much runway do you use?


happydriver
4th Jul 2004, 07:46
I've spoken to alot of guys about how much runway they use when lining up....some guys follow the yellow taxi line and straighten out ahead of the runway numbers and others (especially those on say smaller equipment) like to disregard the yellow line and try and straighten out on the piano keys before the runway numbers...my q is in terms of potential FOD damage and taxiway excursions it must be safer and wiser to follow the yellow lines but in terms of performance calculations that one would find in TL tables do they correct TORA for say a line up allowance for each type of aircraft.....cant seem to find it anywhere in my AOM's....

Cheers:ok:

Empty Cruise
4th Jul 2004, 10:31
Well, JAR-OPS 1 allowance for 90 and 180 deg. line-up (which is what your perf. manual should comply with) does indeed seem to assume you line up behind the taxi line. This problem is worse at some airports than others, some don't seem to have the problem at all.

So the answer would be: yes, turn-around allowance is included in all calcualtions and - on limiting runways - should be the overriding factor in where you do your line-up (physical edge clearance + safety margins for outboard wheel & wingtip still respected, of course).

Brgds,
Empty

Miles Magister
4th Jul 2004, 10:31
HD,

I think the Fod risk is sufficiently low as to not be a problem. Having done a couple of high speed aborts in my career I live by a phrase my 1st QFI taught me very early on in my training.

Runway behind you is as much use as a chocolate fire guard. (And other variations!).

In the commercial world there are often good reasons for not going to the end for take off, and I sometimes do turn on early. But if it is possible I like to use as much runway as possible.

MM

Engineer
4th Jul 2004, 10:53
Surely your decision should be based on your weight. At a MTOW use as much runway as possible. Then factor that decision as weight is reduced.

In terms of performance all TL charts are based on on the brake release point. That can be half way down the runway if you want but maybe not advisable :D

alatriste
5th Jul 2004, 17:27
90º degree taxiway entry.

A/C model TORA/ASDA reduction m. Weight penalty (RLW).

B 737 10.1/24.3 400 lbs

B 747 23.1/47.2 3.000 lbs

B 757 19.4/37.7 1.150 lbs

B 767 22.6/45.4 2.100 lbs

A 320 10.9/23.6

A 330 22.9/48.3

A340 24.4 /50



Weight penalties just for TOW limited by runway length.

I don´t know the complete data for AIRBUS.

safetypee
5th Jul 2004, 17:36
The distance corrections for Airbus aircraft are in the document “Getting to Grips with Performance” and can be downloaded here: Getting to grips with aircraft performance (http://www.nathangb.com/wingfiles.htm) NB 7.88 mb

Old Smokey
8th Jul 2004, 14:48
The yellow line is designed for aircraft LEAVING the runway.

Certification flight testing assumes that the full runway length is used, within the constraints of the individual aircraft's geometry and ground manoeuvering capability. The same tests assume full thrust before brakes release. A great number of FAR 25 certified aircraft assume that the rear-most portion of the undercarriage is JUST inside the runway end (even if you needed a tug to push you back there).

Several FAR 25 aircraft that I've done certification work for operators compliant with JAR-OPS requirements have to make allowance for line-up from the manufacturer supplied AFM data. JAR-OPS supplies a good formula for this, which is usually acceptable to such authorities.

To respond to the original post, my recommendation is -

(1) Leave the yellow line at the runway holding point, manoeuvre so that the outboard gear is just inside the taxiway / runway end, and line up without any wasteage of runway.

(2) If your runway alignment is not quite perfect, don't waste any valuable runway tidying it up, correct the small centre-line / alignment error in the first 200 to 300 metres of the takeoff roll. Whatever amount of runway that you waste here is the distance that you'll overrun the other end of the runway in a performance limited rejected takeoff.

(3) Apply full thrust on the brakes before brakes release.

(4) If your actual Takeoff weight is below maximum, by all means conduct a rolling or roll-on takeoff (which includes gradual application of thrust), provided that correct allowance for rolling / roll-on start is made in accordance with the Flight Manual, or your Company Operations Manual.

If you take a look at the 2 major sets of certification rules, FAR 25 and JAR-OPS, you will see quite generous 'buffers' for the continued takeoff case, but very very little for the rejected takeoff. Accident statistics prove this time and time again.

The Runway behind you, the sky above you, and the fuel that you didn't take are without doubt the 3 most useless things in aviation.