ATCO ordering a rejected take-off?

[Nicholas49]

Hi

I'm not an aviation professional, but I thought this was the best forum to ask this question.

I know that an Air Traffic Controller can order an aircraft to go-around, for example due to loss of separation or contaminated runway. I also know that this is not a rare occurrence.

But can an ATCO order pilots to abort their take-off? If so, can they do this at high speed? Obviously the pilots will not abort above V1, but in any case I imagine the Tower would have no way to tell when V1 is reached? Finally, out of interest, what is the wording used by the ATCO to order this manoeuvre?

Nick

[Crazy Voyager]

For the details I'll let someone who is a profesional reply, but I can answer with respect to the wording.

Standard ICAO phraseology is:
If the aircraft is standing still and has not started rolling
[callsign] Hold position, cancel takeoff (I say again,hold position, cancel takeoff), (reason)
example:
BAW513 hold position, cancel takeoff I say again, hold position cancel takeoff. Traffic departing an intersecting runway.

Or if the aircraft has started rolling
[callsign] stop immediately, (I say again,stop immediately).
Example:
RYR3LV stop immediately, I say again, RYR3LV stop immediately.

Not sure if the callsign needs to be said again but that seems like a minor detail :p
Refrence to DOC9432 section 4-5 (page 4-9)

[HEATHROW DIRECTOR]

If the aircraft has commenced take-off:
"(Callsign) Stop immediately. I say again (Callsign) stop immediately - acknowledge"

If the aircraft has not commenced take-off:
"(Callsign) hold position. Cancel take-off - I say again, cancel take-off - acknowledge".

[vintage ATCO]

If so, can they do this at high speed? Obviously the pilots will not abort above V1, but in any case I imagine the Tower would have no way to tell when V1 is reached?

At Luton we offered guidance at what point (along the runway) it was probably too late but there are so many variables. In the end, the pilot will decide whether to heed the instruction or continue.

[Nicholas49]

Thank you for the answers.

Would it be fair to say, therefore, that on the take-off roll up to V1, the pilots must obey the command to stop, whereas above V1 they are free (and indeed obliged for performance reasons) to ignore it and continue?

[vintage ATCO]

Well, as I said, the pilot will decide if it is safe to comply. In 40 years of controlling I've ordered a few rejected take-offs but it has always been in the initial bit of the take-off roll. I really cannot imagine anything that would be that urgent to command a rejected take-off well into the roll that cannot be sorted out once the aircraft was airborne.

[radarman]

I think the RAF merely give the pilot the necessary information, and let him decide whether it is safer to continue or reject the take-off. (Only applies once the aircraft has commenced its take-off roll). Maybe one of our military colleagues can confirm this.

[aerotech07]

As ATCOs we are told that for jet aircraft, around 80kts is the point at which aborting a takeoff is not an option. As mentioned above, our unit instructions approximate this to a point along the runway. Again subject to a lot of variations etc

We are however reminded that whenever we give an instruction to abort a takeoff once the aircraft has commenced its roll, the pilot may elect to continue the take-off as he deems it safer to do so. The emphasis is to give the rejected take-off instruction, as well as the reason, so the captain has all information to hand to make the call.

[Navigator33]

My take-off briefing states:
Before 80 kts we stop for anything, between 80 and V1 only for engine, failure, fire, aircraft unable or unsafe to fly. After V1 we fly. etc etc.

ATC is not in the 80 to V1 part.

Had a nice discussion over this with an ATCO. It has to be pretty damn urgent if you order us to abort after 80 (and especially around V1).
Yes it is the captain's sole decision to stop the aircraft but in the heat of the moment (between 80 and V1) hearing something like "STOP" can be pretty confusing.
IF the captain aborts after V1 and takes the overrun my bet is that not only said captain will have to explain something (if he/she survives at all)

[Tarq57]

Like a lot of things in Aerodrome control, it's often a judgement call.

The most likely scenario to use the "(c/s) stop immediately.." instruction would be if there is going to be a loss of runway separation should the departure continue.

There are a few different situations that could require that.
-Example 1: the departure has delayed commencing takeoff enough that traffic on final is now too close. This would result in a decision to stop the departure, and send the landing traffic around. This decision has to be made early. If it has gotten to the stage where the departure has passed the thousand foot markers (which is probably close to 80kt), it's been left a bit late, especially considering the arrival will be very short final, at minimum airspeed, and poorly set up for a go around. It's likely to be safer to let it land, loose runway separation, then apologize and file the paperwork (against yourself.)

-Example 2: After the departure has commenced rolling, the controller becomes aware of a runway incursion, happening or imminent. If the departure is still at a (perceived) low speed, the stop instruction (and reason) is made. If at a higher speed, it gets a bit tricky. Technically, the controller should issue the stop instruction (and reason). Practically it is possibly better to provide a lucid and terse informative transmission to the pilot of the departure, and let the pilot decide. The difference is that at higher speed, maybe it's more important to get to the guts of the matter faster, rather than wasting a second saying "blah blah, stop immediately..", so you're offering the reason first.

In either case, it's the perception of the departure's speed that the "grey"area is entered. After a few years on the job, and hopefully a few flight deck famil flights, a controller will have a pretty good idea of where along the runway the critical speeds are happening.

No controller should expect an aircraft to make a high-speed abort if this instruction is issued. Any controller will have a workable "plan B" for the situation. (Any experienced controller will also have a plan C or be able to cobble together a plan D.)

The other type of scenario is where the controller observes an unsafe condition. This could be a flock of geese crossing the runway, a chunk falling from the aircraft or a door opening, a fire observed, or even an earthquake. (Been there, done that. I live on shaky isles.) This sort of thing happens rather rarely.

[DFC]

But can an ATCO order pilots to abort their take-off?


No is the simple answer. ATC can not "order an abort". They can cancel the take-off clearance and as posted above the phraseology is very specific so that there is no doubt about the importance of the transmission.

The pre-80kt and 80kt to V1 is a general sop. There are some differences and some use a slightly lower speed and some use higher.

It must be remembered that when we say "we sill stop for anything up to 80Kt..." We mean anything to do with safety. I don't know anyone who is going to abort at 70Kt because we left our passports behind. By the same token I don't know any ATCO that is going to cancel take-off clearance once rolling simply because he gave the wrong SSR code.

I can't think of any case where ATC would stop us unless safety was an issue. Therefore any call from ATC to stop is taken to be a safety issue and I would stop prior to 80Kt.

[Spitoon]

As ever, the instructions and guidance issued to controllers is a good place to find the answer. In the UK the book says:Cancelling Take-off Clearance

If take-off clearance has to be cancelled before the take-off run has commenced, the pilot shall be instructed to hold position and to acknowledge the instruction.

In certain circumstances the aerodrome controller may consider that it is necessary to cancel take-off clearance after the aircraft has commenced the take-off run. In this event the pilot shall be instructed to stop immediately and to acknowledge the instruction.

The cancellation of a take-off clearance after an aircraft has commenced its take-off roll should only occur when the aircraft will be in serious and imminent danger should it continue. Controllers should be aware of the potential for an aircraft to overrun the end of the runway if the take-off is abandoned at a late stage; this is particularly so with large aircraft or those operating close to their performance limit, such as at maximum take-off weight, in high ambient temperatures or when the runway braking action may be adversely affected. Because of this risk, even if a take-off clearance is cancelled, the commander of the aircraft may consider it safer to continue the takeoff than to attempt to stop the aircraft.

As the aircraft accelerates, the risks associated with abandoning the take-off increase significantly. For modern jet aircraft, at speeds above 80kt flight deck procedures balance the seriousness of a failure with the increased risk associated with rejecting the takeoff. For example, many system warnings and cautions on the flight deck may be inhibited during the take-off roll, and between 80kt and V1 most aircraft operators define a limited number of emergency conditions in which the take-off will be rejected. Consequently, at speeds above 80kt, the take-off clearance should normally only be cancelled if there is a serious risk of collision should the aircraft continue its take-off, or if substantial debris is observed or reported on the runway in a location likely to result in damage to the aircraft. The critical speed will be dependent on the aircraft type and configuration, environmental conditions and a range of other factors but, as a general rule, for modern jet aircraft, it will be in the region of 80kt airspeed. The typical distance at which a jet aircraft reaches 80kt is approximately 300m from the point at which the take-off roll is commenced. The unit MATS Part 2 shall contain further guidance on the likely position on the runway at which those aircraft types commonly using the aerodrome typically reach 80kt.

Controllers should also be aware of the possibility that an aircraft that abandons its take-off may suffer overheated brakes or another abnormal situation and should be prepared to declare the appropriate category of emergency or to provide other suitable assistance.
There used to be lots more useful guidance in an ATSIN but sadly, like lots of other good advice in ATSINs and other short-lived documents, it's no longer available on the CAA website.

[NigelOnDraft]

Question has largely been answered above. Our company did raise this as a "discussion item" at one Sim Session after an ATCO called STOP over the R/T, after the T/O Roll had started, for a slot change :ugh:

Whilst we not offered hard and fast advice, as above, stopping <80K is little hazard. >80K I am more interested in the problem than the phraseology.

My only concern above is the use of the word "STOP" over the R/T. In our outfit, it is the executive word either of us use to the other to initiate an RTO, exceptionally even above V1. The ideal situation would see ATCOs using a different word to us - that said, maybe some airlines use another word than "Stop"? There is potential for one pilot to initiate an RTO thinking it was the other pilot saying "Stop" :{

NoD

[Tarq57]

IIRC, the ATC phrase (at least where I live) used to be "abort", but was changed to "stop" several years ago.
I thought the reason was that the word "abort" should be reserved for use within the flight deck only.

Isn't it ironic?

[Nightrider]

During the years and with several outfits as a contractor I was asked to use:

- Cancel
- Abandon
- Abort
- Reject
- Stop

As a matter of fact, the philosophy of having a silent flightdeck environment makes all of these phrases a valid call.

Until 80 kts any reason may be used to call for the wish to stay on ground. Between 80 and V1 the reason is for a call is the key. It is the captain who decides if the thrust levers go to idle and the brakes needs to be checked.

And it is him who has to fill the paperwork if he (hopefully) is still in the position to do so.

The 300 meters distance as mentioned in the book is a perfect guidance and any controller calling after this amount of runway was used triggers the "stop in case of airplane being unable or unsafe to fly" part of the briefing. And as the book also says, the captain may decide to continue in this case.

[Excelsior100]

Correct...until 80 or thereabouts iwe slam stop (could be a cow where I live,,, and a colleague has real live experience, all caof..."BLOOODY COW ABORT, ABORT NOW!!! (poetic ATC no?) closer into V1 Judgement of pilot flying rules. Other pilot should override/suggest (if F/O) only if s/he has information PF does not her have/cannot process to order cancellation/abort This typically should be something in the external environment not the airframe.


and V1 is V1

[ATCNetwork]

Not an example of the correct phraseology or correct timing but this reconstruction is very on topic to this discussion.

YouTube - Runway Incursion Chicago O'Hare Jul 23rd (http://www.youtube.com/watch?v=u627QT26rCs)

[fujii]

In Australia.

If not moving "(Callsign) Hold position, cancel, I say again cancel takeoff."
Rolling "(Callsign) Stop immediately, (repeat callsign) stop immediately (reason)" The reason is given and the decision left to the captain.