A320 Required Runway Length

[reverserunlocked]

Obviously runway length is dependent upon OAT, winds, height above sea level etc.. but could somebody give me some absolute minimum ball park runway lengths for an A320, lowish GW, sea level airfield, no wind, say OAT of +10...what would you have a go at before chickening out?

[SLT]

I can't answer you exactly as I don't have the facility to hand, but most of our takeoff performance is geared to the weight at which you are getting airborne. You are quite correct in saying that OAT, QNH and field elevation are some of the factors affecting performance, but there are others such as surface condition (wet, slippery, contaminated etc.), engine bleed extraction (are we running the packs off the engines or using anti-icing?) and aircraft C of G.

We tend to enter the performance chart at our take off weight and that will give us the speeds and flex temperature applicable to our weight. These charts are runway specific and include the runway length as one of their factors.

Looking in FCOM 2 at the Quick-Reference charts, just to give you an idea, the figures are given for a 2000ft airfield with a dry runway. You can get airborne with full power at a weight of 60 tonnes at an OAT of +16 on a 1500m runway in still air. Rather shorter that we are all used to, but equivalent to some of the smaller Greek islands. Skiathos springs to mind.

As regards what would be the minimum runway length I would take off from - as long as we have the performance - I'll do it. Don't forget - take off performance isn't just about getting airborne within the length - it's about being able to stop from V1 if it all goes wrong without going off the end!!

I've just re-read this answer and realised it reads like a performance lecture - it's not meant to!!!! But I hope it goes some way to answering your question.
:)

[husqvarna]

Just a quick question on some of the terms used as I am not a pilot. I can not figure out terms such as V1, OAT, and QNH. Any help?
One more question I have always had, but slightly off topic. When I was flying in a 744 and a 777-? , our pilot used the term "UA815 heavy". What does the addition of the word "heavy" signify?

[russelldav]

husqvarna...

not a pilot myself, but from experience with flight sims;

'Heavy' just means that the aircraft is large, and heavy, which the controller uses to plan spacings, and note different speeds/altitude requirements??? (might be wrong there).

Larger aircraft disrupt the air around them, so a smaller aircraft following would get a rough ride. By telling ATC you're heavy they can leave a larger gap between you and the next plane.

And V1 is a stage you go through on the runway during takeoff if I'm correct. I think its to do with speed, but again, lack of real-life experience means I don't know. lets hope a pro replies

:rolleyes:

[Final 3 Greens]

Husqvarna

OAT = outside air temperature

QNH = altimeter setting to achieve altitude (above seal level), QFE = altimer setting to achieve height above an airfield

'Heavy' refers to a wake turbulence category and controllers must allow minimum separation between aircraft depending on the combination of wake turbulence categories involved.

V1 is a decision speed for an airliner during the take off roll.

A problem before the speed is reached may result in a rejected take off (stopping) depending on the severity.

After V1 the aircraft will take off and the crew will deal with the problem in the air. The decision speed is required, in simple terms, to ensure that an aircraft does not try to stop and run off the end of the runway because it is going too fast.

PS, I'm not a pro, but a private pilot with multi engine experience :D

[reverserunlocked]

Thanks for all your replies so far, much obliged...

Let me put it another way, going back to our A320, lowish GW, all other factors being favourable, what's a ballpark minimum length you could stop it in? Reversers on coming over the fence, max braking, wing and prayer, that sort of thing....!

I've flown a full-size 737 sim where we tried to land at Barton!!! I got it in - I'm not too sure how you'd get it out again though...

[SLT]

According to a non-updated QRH I have - a CFM powered A320 at 50 tonnes (empty plus a bit of fuel) could stop in around 740m, using autobrake Medium on landing and full reverse. I stress that there is NO margin included in these figures - that is purely theoretical.

[GlueBall]

I've never heard of certificated stopping distances that are predicated on the inclusion of reverse thrust, at least not in the USA.

[SLT]

You are quite correct Gluey, it's the same in the UK - for planning purposes, all performance is predicated on no reverse. All I did in this case was apply the appropriate correction for the use of both reversers (between 2 and 4% dependant on MSN) as if we were airborne - this is permitted.

Cheers!!

[Rabbit]

SLT... be careful when using QRH distances. They are actual demonstrated distances achieved by professional test pilots who are not very gentle with the airframe. I have tried in the sim and have checked others in the sim in trying to achieve these figures. Noone has managed to get close. In fact most are barely on the ground within the distance specified.

Have a nice day

[SLT]

Yes I understand that, and that's why if was going to be using this for real I would a) use a properly updated QRH and b) apply the increased margins as per normal operating procedure. I was merely answering this chap's theoretical question with a theoretical answer - I thought I made that clear in a previous post:

"I stress that there is NO margin included in these figures - that is purely theoretical."

Cheers

[john_tullamarine]

The typical unfactored distances (with various system abnormalities) found in QRH data are intended for emergency use.

To use such data without appropriate consideration of available options etc., would be to invite censure at the enquiry ....

[reverserunlocked]

Yes I think we're clear on how, when, what and why to be wary of the 'demonstrated' figures and I thank the chap above for answering my 'theoretical' question with a strictly 'theoretical' answer.

In sim practice, do you chaps have a bit of a lark after all the serious procedural stuff and try to land a 777 in Jersey or similar?
Anyone suceeded?

[northwing]

The numbers in the book allow for crossing the fence at 50ft, flareing to touchdown, and stopping using full brakes without reverse thrust. The sum of of the above is multiplied by 1.67 to allow for variations in technique, touchdown point, runway friction and all the other uncertainties of life. Attempt to land in less than that and you are out of warranty, insurance cover and probably your job. The unfactored distance will have been demonstrated by a test pilot, but he will have been trying hard and flying the landing exactly according to the book, getting the brakes on sharpish etc. There has been a lot of argument about the 1.67 factor, but it can be substantiated - sort of - in terms of the sort of performance people generally put in. So it is worth respecting.