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Topic: RWY Length/Airport Altitude & Engine Performance
Username: A388
Posted 2012-12-02 18:08:03 and read 4263 times.

Hi everyone,

I was wondering if anyone could tell me the relationship between runway length, airport altitude and engine performance. The reason why I ask is for the airports in Bogota and the new airport to be opened at Quito. Cargo aircraft taking off from these airports at full payload need a fuelstop if they fly to Europe but will this still be the case of these airports would extend their runways or does the altitude of these airports still influence the engine performance, no matter how long the runway is? Can cargo airlines soon fly nonstop to Europe from the new airport in Quito when it is opened?

A388

Topic: RE: RWY Length/Airport Altitude & Engine Performance
Username: AR385
Posted 2012-12-02 18:14:46 and read 4247 times.

Another thing to consider is tire-rotation speed limits. At some point, no matter how long the runway, you cannot exceed certain speed for a given amount of time, otherwise they┬┤ll blow.

Topic: RE: RWY Length/Airport Altitude & Engine Performance
Username: prebennorholm
Posted 2012-12-02 18:30:15 and read 4217 times.

BOG is at elevation 8,360 feet. Quito is even higher at 9,200 feet.

At such elevations a heavy plane very fast runs into problems with wheel speed limit. No runway length can solve that problem.

Airports with such elevation will always have severe operational limitations compared to more normal airports. What limitations depends on aircraft type, temperature, wind, runway conditions (wet/dry) etc.

Topic: RE: RWY Length/Airport Altitude & Engine Performance
Username: A388
Posted 2012-12-03 05:14:59 and read 4142 times.

This is great information, please give me more information. Can you tell me more about this wheel rotation speed limit? How does this work, especially for the 747-800F, 747-400F, 777-200LRF, MD11F, A330-200F? Based on the replies I got so far, this speed limit is a problem at high altitude airports? I also remember reading in the past something about the air thickness (correct me if I'm using the wrong wording here) having an influence on engine performance?

Best regards,

A388

Topic: RE: RWY Length/Airport Altitude & Engine Performance
Username: tdscanuck
Posted 2012-12-03 08:08:17 and read 4116 times.

Quoting A388 (Thread starter):
I was wondering if anyone could tell me the relationship between runway length, airport altitude and engine performance.

Higher altitude means less thrust from the engines, which means more runway is required to reach a given speed. Compounding the problem, higher altitude means thinner air, which means you need to go faster to takeoff, so you need to reach even higher speeds using less thrust, which leads to really long runways.

Quoting A388 (Reply 3):
Can you tell me more about this wheel rotation speed limit? How does this work, especially for the 747-800F, 747-400F, 777-200LRF, MD11F, A330-200F?

All tires have a speed limit (they start to come apart if they go too fast). It's typically about 245 mph. If you look at the takeoff charts in the ACAP document for any airplane you'll see the tire speed limit in there.

Quoting A388 (Reply 3):
Based on the replies I got so far, this speed limit is a problem at high altitude airports?

The limit always exists, but you never get there for low altitude airports because you can get enough lift out of the wing, even at max weight, at a speed lower than the tire speed limit. It's only when you're up high that you need to go that fast on the ground just to takeoff.

Tom.

Topic: RE: RWY Length/Airport Altitude & Engine Performance
Username: Pihero
Posted 2012-12-03 10:24:31 and read 4088 times.

In many instances, the first limit to hit an airliner at a high elevation airport is the climb one (on a second segment, generally ), especially for twin-engined ones.
Then on a rather quick succession, the braking energy limit and the tyre speed limit intervene.
The only way to avoid these limitations is the conveyor belt        

Topic: RE: RWY Length/Airport Altitude & Engine Performance
Username: Viscount724
Posted 2012-12-03 14:05:23 and read 4043 times.

Quoting prebennorholm (Reply 2):
BOG is at elevation 8,360 feet. Quito is even higher at 9,200 feet

And LPB is 13,325 ft.

Topic: RE: RWY Length/Airport Altitude & Engine Performance
Username: kl671
Posted 2012-12-03 14:37:06 and read 4038 times.

Quoting A388 (Thread starter):
I was wondering if anyone could tell me the relationship between runway length, airport altitude and engine performance.

Everything you want to know about take off performance is provided on the Boeing and Airbus web sites.

http://www.boeing.com/commercial/airports/plan_manuals.html

http://www.airbus.com/support/mainte...cal-data/aircraft-characteristics/

Topic: RE: RWY Length/Airport Altitude & Engine Performance
Username: rwessel
Posted 2012-12-03 22:21:45 and read 3982 times.

Quoting Pihero (Reply 5):
In many instances, the first limit to hit an airliner at a high elevation airport is the climb one (on a second segment, generally ), especially for twin-engined ones.
Then on a rather quick succession, the braking energy limit and the tyre speed limit intervene.
The only way to avoid these limitations is the conveyor belt

How would the conveyor belt let you avoid the second segment climb limits?   

Topic: RE: RWY Length/Airport Altitude & Engine Performance
Username: Pihero
Posted 2012-12-04 07:41:17 and read 3940 times.

Quoting rwessel (Reply 8):
How would the conveyor belt let you avoid the second segment climb limits?

Wot !?! You don't believe in technical magic ? Shame on you !   

Topic: RE: RWY Length/Airport Altitude & Engine Performance
Username: Fabo
Posted 2012-12-04 10:13:15 and read 3918 times.

Quoting rwessel (Reply 8):
How would the conveyor belt let you avoid the second segment climb limits?   

Suppose it would be used correctly, it could allow the airplane to obtain higher Vr and consequently V2, through virtues of lowering relative speed aircraft/surface, thus enabling higher CAS/IAS to be used regarding maximum tyre speed (at the very extreme, tyre speed could be zero), additional braking for V1 cut (max. brake energy requirement) and possibly also better ground controlability in case of engine failure.

Some sort of catapult assisting device could also help give airframe more energy.

Topic: RE: RWY Length/Airport Altitude & Engine Performance
Username: Dreadnought
Posted 2012-12-05 10:39:31 and read 3801 times.

Quoting Pihero (Reply 5):
In many instances, the first limit to hit an airliner at a high elevation airport is the climb one (on a second segment, generally ), especially for twin-engined ones.

I would have thought 4-engined aircraft have a harder time, as twins tend to be very much overpowered, due to the design need to be able to climb with one engine out.

It might be interesting to watch a loaded A340-300 try to take off from Quito...

Topic: RE: RWY Length/Airport Altitude & Engine Performance
Username: Pihero
Posted 2012-12-05 11:23:15 and read 3788 times.

Quoting Dreadnought (Reply 11):

I would have thought 4-engined aircraft have a harder time, as twins tend to be very much overpowered, due to the design need to be able to climb with one engine out.

That's exactly the point. We do not dispatch before all engine-out possibilities are explored, and as in case of engine failure, the twin has lost half of its thrust and has tghe burden of the big fan drag, the quad still has 75% of its thrust wiuth an added half valuie drag compared to the twin... therefore, the twin loses traffic load a lot more rapidly than the equivalent quad.
Of course, if everything is normal, the twin sparkles - and even more so that it takes off at a lighter wieght than its counterrpart.

Quoting Dreadnought (Reply 11):
It might be interesting to watch a loaded A340-300 try to take off from Quito...

See this :
340 out of Quito

A non event

Topic: RE: RWY Length/Airport Altitude & Engine Performance
Username: Mir
Posted 2012-12-06 00:07:42 and read 3698 times.

Quoting Dreadnought (Reply 11):
I would have thought 4-engined aircraft have a harder time, as twins tend to be very much overpowered, due to the design need to be able to climb with one engine out.

Twins are only overpowered if both engines are running, otherwise they're barely making the required climb gradient. So in an engine-out situation, the quad will outperform the twin almost every time.

-Mir

Topic: RE: RWY Length/Airport Altitude & Engine Performance
Username: tdscanuck
Posted 2012-12-06 06:55:05 and read 3649 times.

Quoting Mir (Reply 13):
Twins are only overpowered if both engines are running, otherwise they're barely making the required climb gradient. So in an engine-out situation, the quad will outperform the twin almost every time.

With an engine-out the quad will only barely make the required climb gradient too...the basic sizing considerations are the same in either case. However, the required gradient is different between quads and twins.

Tom.

Topic: RE: RWY Length/Airport Altitude & Engine Performance
Username: ferpe
Posted 2012-12-06 11:14:42 and read 3603 times.

Quoting tdscanuck (Reply 14):
However, the required gradient is different between quads and twins.

Absolutely, twin 2.4% and quads 3.0%. Now why the difference?

Topic: RE: RWY Length/Airport Altitude & Engine Performance
Username: A388
Posted 2012-12-06 11:31:02 and read 3595 times.

Great thanks for all the information guys.

I'm going through the Boeing material but I can't find the runway length/airport altitude related aircraft performances (tire speed limits etc). Can anyone point me to the document concerned or is there a website that has an overview of the necessary runway lengths due to airport altitudes? For example, which cargo aircraft types can take off at full payload from the new airport in UIO when it opens? What about BOG?

Cheers,

A388

[Edited 2012-12-06 11:49:15]

Topic: RE: RWY Length/Airport Altitude & Engine Performance
Username: A388
Posted 2012-12-06 12:31:41 and read 3585 times.

Quoting tdscanuck (Reply 4):
which leads to really long runways.

What runway length do you consider really long?

A388

Topic: RE: RWY Length/Airport Altitude & Engine Performance
Username: tdscanuck
Posted 2012-12-06 13:28:25 and read 3575 times.

Quoting A388 (Reply 16):
I'm going through the Boeing material but I can't find the runway length/airport altitude related aircraft performances (tire speed limits etc). Can anyone point me to the document concerned or is there a website that has an overview of the necessary runway lengths due to airport altitudes?

What you want is the FAR takeoff chart from the ACAP documents. For example:
http://www.boeing.com/commercial/airports/acaps/777rsec3.pdf

Take a look at p.6 of the PDF: FAR takeoff length requirements for the 777-200LR on a standard day. There are (at least) two ways to use this chart. If you want to know what you can do at a particular airport, start at the runway length and go across until you hit the curve for the airport's altitude, then go down and read off the weight you can takeoff at. If you want to know how much runway you need, start at your desired takeoff weight and go up to the airport altitude curve, then read across to the runway length you need.

The dotted line across the top of the curves is the tire speed limit...you can go faster than that even if you have more runway. The dotted line on the right is the maximum takeoff weight...you can't go heavier than that even if you have more runway. Depending on the aircraft, you may also see another speed limit line (e.g. the 737 has two different speed ratings on the tires) and/or a maximum brake energy line.

ACAP documents are available at:
Boeing: http://www.boeing.com/commercial/airports/plan_manuals.html
Airbus: http://www.airbus.com/support/mainte...cal-data/aircraft-characteristics/
Embraer: http://www.embraercommercialjets.com/#/en/apm
Bombardier: haven't found this one yet...

Quoting A388 (Reply 16):
For example, which cargo aircraft types can take off at full payload from the new airport in UIO when it opens? What about BOG?

To figure that out, you need to go through the ACAP documents one-by-one. However, what matters for takeoff is total weight (OEW+fuel+payload), not just payload, so you need to know what range you want to go before you can answer a question like that.

Quoting A388 (Reply 17):
What runway length do you consider really long?

I'd call anything over about 12,000' "really long" but that's just me. The old SAC bases like Moses Lake (KMWH) or Glasgow MT (07MT) are "really long" at 13,000'+. Denver 16R/34L is really really long at 16,000' (it's longer than Edwards AFB).

Tom.

Topic: RE: RWY Length/Airport Altitude & Engine Performance
Username: Dreadnought
Posted 2012-12-06 17:59:07 and read 3546 times.

Quoting Mir (Reply 13):
Twins are only overpowered if both engines are running, otherwise they're barely making the required climb gradient. So in an engine-out situation, the quad will outperform the twin almost every time.

I was thinking about normal operations - 99.999% of the time all engines are running.

Edit: Just out of interest, I looked up the longest runway in the world. It's in China, at 14,200 feet altitude, and the runway is over 18,000 feet long.

[Edited 2012-12-06 18:02:28]

Topic: RE: RWY Length/Airport Altitude & Engine Performance
Username: Pihero
Posted 2012-12-07 03:22:24 and read 3506 times.

Quoting tdscanuck (Reply 18):
.you can go faster than that even if you have more runway.

Happens to me all the time : You wanted to say : "you CAN'T go faster than that even if you have more runway... "

Quoting Dreadnought (Reply 19):

I was thinking about normal operations - 99.999% of the time all engines are running.

Yes,; but understand that these twins have already been restricted to a lower GW due to the fact that we always consider an engine failure for our take off weight computations, and as Ferpe has written in his # 16+ :

Quoting ferpe (Reply 15):

Absolutely, twin 2.4% and quads 3.0%.

Topic: RE: RWY Length/Airport Altitude & Engine Performance
Username: BE77
Posted 2012-12-07 03:48:46 and read 3506 times.

WS started this a couple of years ago to save fuel, but maybe the same thing could help high altitude airport operations. Lower weight would help the takeoff speeds, and both 1st and 2nd segment climbs.

http://www.westjet.com/guest/en/media-investors/helium.shtml

Otherwise - interesting thread, and while I knew the concepts it's interesting seeing the details. Especially thanks for the links on the real facts!

Topic: RE: RWY Length/Airport Altitude & Engine Performance
Username: starlionblue
Posted 2012-12-07 05:40:41 and read 3500 times.

Quoting Dreadnought (Reply 19):
Edit: Just out of interest, I looked up the longest runway in the world. It's in China, at 14,200 feet altitude, and the runway is over 18,000 feet long.

That's the longest paved runway. The longest runway in the world is at Edwards AFB, 17/35 at 39,907 ft long. There are multiple others at Edwards longer than 20000 feet.

http://en.wikipedia.org/wiki/Edwards_Air_Force_Base#Main_base

Topic: RE: RWY Length/Airport Altitude & Engine Performance
Username: tdscanuck
Posted 2012-12-07 05:55:54 and read 3497 times.

Quoting Pihero (Reply 20):
Happens to me all the time : You wanted to say : "you CAN'T go faster than that even if you have more runway... "

Yes. Yes I did.

Tom.

Topic: RE: RWY Length/Airport Altitude & Engine Performance
Username: BE77
Posted 2012-12-07 06:57:27 and read 3488 times.

Quoting starlionblue (Reply 22):
The longest runway in the world is at Edwards AFB, 17/35 at 39,907 ft long

I knew this before, but seeing it written here made me realise that runway is longer than some flights I've made that begin and end at different airports - including international flights. Not on transport category planes, but in personal GSA and some commercial GA charters as well!


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