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On a recent trip through Australia I did a number of intra-oz flights. In at least three of the cases we performed intersection takeoffs, a couple at MEL/YMML and one at BNE/YBBN. I have at least a thousand domestic flights within the USA, and although I wouldn't bet my life on it, I can't remember ever doing an intersection takeoff there.

The MEL/BNE runways are quite long - even with the intersection takeoff the available runway was over 8,000 feet in each case.

Am I wrong that this is super rare in the USA? Are there airports where intersection takeoffs are commonly used, and maybe I just never fly through those? The advantages are obvious, it saves taxi time and fuel, and a 737-800 on a 75 minute stage can't be anywhere near gross weight anyway. In the USA, airports like HOU/MDW have runways that are shorter than our takeoff roll, which strongly suggests there's no outright safety issue... and these airports handle hundreds of 737-800s a day identical to the QF/VA ones I was on here. What other things am I missing here? Are the aussies just more time/fuel conscious than us yanks? ;-)

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  • $\begingroup$ And as SOON as I write this up, we did an intersection takeoff at ORD yesterday... $\endgroup$ – ljwobker Mar 16 at 16:46
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US airlines are extremely fuel conscious. They have software that calculates the exact throttle and flap settings required for the exact length of runway available so that they don't burn any more fuel than necessary, and that is all typically computed before they even push back from the gate.

If the pilots know in advance (e g. from the ATIS) that intersection departures are in use, they'll calculate for that. However, if they're already taxiing out to the end and ATC asks if they can accept an intersection departure instead, they'll need time to rerun "the numbers" and reconfigure the aircraft. US ATC has learned from experience that this delay often negates whatever trick they were trying to pull off, so they usually don't bother asking unless there's a really good reason.

Also, unlike light planes, for safety reasons airliners are required to have enough runway available to accelerate to V1 (nearly rotation speed) and then brake to a stop again before the end if they need to abort. This means they'll rarely use more than about half the runway available. This is factored into "the numbers", of course, and is another reason why they need to be checked before accepting an intersection.

As to why intersections seem more common in Australia, perhaps there is some difference in how their airports are designed, or perhaps their ATC is just more willing to do it, or perhaps Qantas pilots are faster at running "the numbers" or have a habit of running all likely options instead of just the expected one.

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    $\begingroup$ While I agree with all the points you make, I don't think there are any differences between the US and the rest of the world in what you describe. OP is asking specifically about differences between the US and the rest of the world $\endgroup$ – J. Hougaard Mar 15 at 9:14
  • $\begingroup$ @Bianfable Yes, V1 rather than Vr. Fixed that. But IIRC light twins don't have the balanced field requirements; it's Part 23 vs Part 25. $\endgroup$ – StephenS Mar 15 at 15:18
  • $\begingroup$ @StephenS Thanks for the update. You're right, light twins actually don't, but AFAIK it's not just airliners. $\endgroup$ – Bianfable Mar 15 at 16:08
  • $\begingroup$ So this is somewhat helpful, but when you’re looking at a 10 or 11 thousand foot runway on a short 737, the runway length is not an issue- you only need half of it (see comparison to MDW/HOU). Perhaps it’s just “easier” although more expensive to just run everyone out to the end regardless of whether they could use a shorter run or not. $\endgroup$ – ljwobker Mar 15 at 17:25
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    $\begingroup$ @ljwobker A longer runway means using less thrust; they still have to run the numbers for whatever length they have, and if ATC changes the length, they're still required to rerun them even if it's "obvious" they have enough. $\endgroup$ – StephenS Mar 15 at 19:16
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I fly them with a fair bit of regularity, then again I fly a PA-28 out of various Class D and C airports so my takeoff requirements are usually well under the available runway. Sometimes if you are in line behind a jet waiting for their IFR release the tower may give you a VFR departure in front of them from an intersection.

They say pilots are foolish for leaving fuel on the ground and leaving useable runway behind them.

The FAA has a fair bit of regulations to allow an intersection departure particularly at night:

f. An aircraft may be authorized to line up and wait at an intersection between sunset and sunrise under the following conditions:

  • The procedure must be approved by the appropriate Service Area Director of Air Traffic Operations.

  • The procedure must be contained in a facility directive.

  • The runway must be used as a departure-only runway.

  • Only one aircraft at a time is permitted to line up and wait on the same runway.

  • Document on FAA Form 7230-4, Daily Record of Facility Operation, the following: “LUAW at INT of RWY (number) and TWY (name) IN EFFECT” when using runway as a departure-only runway. “LUAW at INT of RWY (number) and TWY (name) SUSPENDED” when runway is not used as a departure-only runway.

g. Do not authorize an aircraft to line up and wait at anytime when the intersection is not visible from the tower.

Airline operational requirements may also require a full length departure.

All these things considered it can be simpler to just grant everyone a full length departure.

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  • $\begingroup$ The departure-only part is relevant here... in AU we were most certainly using those runways for both departure and arrivals - both MEL and BNE are (functionally) single runway airports. $\endgroup$ – ljwobker Mar 15 at 17:27
  • $\begingroup$ @ljwobker, not true: in AU (and specifically YMML and YMEN), it is very common to use one (of the intersecting runways) for departure, and another for arrival concurrently. It is also common to just use both; some of the aircraft (e.g. A380) may only be permitted on one of them. $\endgroup$ – Zeus Mar 16 at 4:09

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