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I listen to the Dr Karl podcast where in a recent one he stated the longest take off run was by a C-130 (Hercules) plane in Greenland a long while back (I gather it was some unusual condition and not a commercial flight).

I'm wondering which commercial flight has the longest take-off run? Presumably a bigger plane, with a large fuel load for a long-haul flight, chock-full of passengers.

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closed as off topic by Marcel C., uncovery, RoflcoptrException, Karlson, Kate Gregory Apr 3 '13 at 20:26

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Passenger or doesn't matter? –  Karlson Mar 31 '13 at 18:54
    
Do you know the length of the Greenland one? –  DarkLightA Mar 31 '13 at 19:27
2  
Very high altitude airports also require longer take-off runs. –  uncovery Mar 31 '13 at 23:15
1  
Take-off run varies with weight, altitude, weather, plane type and arguably pilot skill. There isn't going to be a single scheduled flight for which there is a longest run. Plus there are almost certainly occasional cases where the take-off run is longer than intended or calculated, and wasn't reported by the pilots (especially if it was due to a weight miscalculation). –  DJClayworth Apr 1 '13 at 1:51
    
@RussellMcMahon I merely linked to Dr Karl so people would know the source - but it's the one from March 20th. I didn't quote it as it was literally a throwaway comment about the fact that such a takeoff occurred. A quick google search seems to indicate that he's mentioned it before in earlier podcasts as others have hunted for an answer as well. Sounds like some scientists were having trouble taking off and even had to ditch stuff out the back of the plane. –  Mark Mayo Apr 1 '13 at 16:16
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1 Answer 1

up vote 9 down vote accepted

Short:

I don't know the real world answer, but, based on the assumptions listed below, on a standard 10,000 foot international runway a fully laden A380 will begin to be in trouble at much over 1 minute and in deep trouble at about 70 seconds (eg removing the pieces of perimeter fence from the landing gear may be problematic).

The 45 seconds or so that I've experienced in a 747 felt "much too long".

If you wanted to do the longest possible run "just for fun" a craft with a very low takeoff velocity on a 12,000 foot runway could toddle into the air after more than 2 minutes of takeoff run, with room to spare.


I have experienced somewhere in the range of 60 to 100 airline takeoffs in the last 5 years (trips blur, I should make a record).
I roughly note the time taken for most but not all takeoffs.
I do not record the results but my impression is that they are typically longer on average now than they were 5 years ago. I'm told (no reference) that longer takeoff runs use less fuel. In my experience mid 20 second runs happen, high 20's to low 30s' are more usual. I have had one run which was well over 40 seconds - I was getting mildly concerned :-). I asked the pilot about it afterwards and he said it was not exceptional with a heavy load.

International runways are typically 10,000 feet long. Some are around 12,000 feet - but the added length is usually aimed at allowing very heavily loaded freight planes to land.

Assume

  • A 12,000 foot runway

  • Liftoff speed of 120 mph = 176 fps = 192 kph = 53 m/s
    (which is about 66% of an A380's nominal takeoff speed of 78 m/s).

  • All runway used

  • Constant acceleration from rest.

Mean velocity = Vtakeoff/2 = 176/2 = 88 fps.

Liftoff time is Length / Vmean = 12000 / 88 = 136 seconds = 2 minutes 16 seconds.

The same calculation with an A380 with liftoff at 78 m/s = 256 fps.
Mean V is now 128 fps.
Liftoff time is 12000/128 = 94 seconds.

Now try a 10,000 foot runway A380 etc.
10,000/128 = 78 seconds.

Allow a 10% "safety margin" (you crash slightly slower :-( ) and you get
9000/128 = 70 seconds.


Related:

14 CFR 23.59 - Takeoff distance and takeoff run.

FAA PART 23--AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES

Wikipedia - runway length

FAA definition{s} of takeoff distance

Wikipedia - Lonnnnnnnnnnnngest runways - at least 4000m / 13.123 feet !!!

  • Qamdo Bamda - 18,045 feet !!!
    Q: Why???
    A: Altitude = 14,219 feet.
    Oh!

  • Ramsnskoye - 17,723 feet
    Q: Why?
    A: Altitude 404 feet.
    Q; Why ???
    A: Once used for testing Buran Spaceplane.
    Oh!

TORA, ASDA, TODA, LDA, SWY, CWY, D, ...

Image below is from link above -

enter image description here


Unrelated :-) - encountered along the way

VTOL blast platform design
Zero seconds liftoff run!

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pretty well put. Takeoff is never calculated in time anyway, but distance. And pilots will be sweating blood if they're so heavy they need more than about 2/3 of the runway (though it happens at times) because that leaves them no safety margin for a late abort. Very long runways are more often needed of course in very high and/or hot areas where air pressure is lower, reducing lift and thus increasing takeoff distance (as a result aircraft in those areas also tend to be unable to take off with a full load). –  jwenting Apr 2 '13 at 6:51
    
@jwenting - I recall a report of a Himalayan emergency recovery operation where a helicopter could fly but not take off so had to hover at all times during loading. In the fabulous "Chickenhawk" Vietnam war copter book he at one stage cleared a low wall when the craft would not otherwise lift and was over a suspect minefield by rotating to add extra lift. Ground affect is a killer (literally) in marginal fixed wing situations where you can get airborne on the GE cushion but when you lift out of it you stall and cannot recover the GE buffer. Various inexperienced pilots have died as a result. –  Russell McMahon Apr 2 '13 at 18:11
    
That chopper pilot was extremely lucky the downwash didn't set off some pressure sensitive mines... Ground effect can be a killer, but also a life saver. It's prevented or ameliorated quite a few crashes by giving just a few more seconds to get a plane under control :) –  jwenting Apr 3 '13 at 6:08
    
It wasn't as short by far as some but for sheer "fun" there was Kai Tak. In my youth wanted to see this in real life - alas it closed before I first visited HK. Concord at Kai Tak - 1996 !!! –  Russell McMahon Apr 4 '13 at 1:16
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