What do departure times actually mean?
 

Anyone here who works in despatch who can help me with a question?

When airlines quote departure and arrival times, to what to they actually refer? Is departure the time the gate closes, the time the aircraft is pushed back or the time the wheels leave the runway? Is arrival the time the aircraft touches down or when it arrives at the gate?

The reason I ask is that I'm of on my honeymoon in a few weeks and we're doing a total of 11 flights, 7 of which are with United Airlines, and I've been watching the flights over the past few weeks to see how reliable they are.

Take UA 931 from London to San Francisco, the quoted departure time being 14:45. On average, the plane leaves at about 15:20 and united's web site tells you how early or late it is and they say it's about 8 minutes late leaving, putting United's opinion of the target departure time at 15:12. Can anyone explain this disparity? Do airlines work to a slightly different internal timetable to the one published?

Rob.

From what I gather (as a wet-behind-the-ears SLF), the advertised time of departure is the target push-back time. However, if an aircraft pushes back within 15 minutes of the advertised time, it's deemed to be on schedule.

Therefore, if an a/c pushes back at T+14 then sits on the tarmac for 20 minutes, it's still regarded as a punctual departure.

I hear certain British railway companies are trialling a similar scheme... :rolleyes:

The times quoted in timetables, tickets etc. are "block" times. That is basically "chocks off" to "chocks on". Taxy times are incorporated (and adjusted for peak periods) as are prevailing winds for the route. Flying from airports such as JFK you can depart the gate on time, take-off an hour later and still arrive at your destination half an hour early! These days airlines allow plenty of elasticity in their schedules in order to mask delays.

The departure time is when the aircraft pushes back, or leaves the gate. The arrival time is when the aircraft arrives at the gate.
The times are recorded, and transmitted to the company automatically via our ACARS datalink. The 'off' time is sent when the park brake is released after all doors are closed. The 'on' time is recorded when the park brake is set after arrival at the gate. It is not sent until the first door is opened, but the actual time recorded is the 'park brake' time.
We have no control over this, as it is done automatically, so we cannot 'cheat' and give an on schedule time when we are late.

Airclues

Well noe Captain Airclues, thanks for the technical description of a depaeture time. I realise that as the Number One of the craft you have to deal with so many different variables to depart on time so please let this PAX give his definition of "What a departure time actually means".

In my experience, it means anything between actually taking off, i.e. in the air at the time we are due to be in the air, ( yes lucky me, and the rest of the passengers) and 29 hours late via Virgin Atlantic, LGW-BOS with no apology, no food, no drink and 14 Hours on the M-25 motorway between LGW and Stanstead and back, arrival at Newark, with no luggage, and about 3 hours sleep, 200+ annoyed and bitter Americans! An Indian family, emigrating to the USA, under an armed police guard, because they apparently had no visa for the UK! Oh and yes, no compensation. A better take off experience was on Sudan Airways from Port Sudan to Jeddah! 18 hours late arrival at Jeddah via a ferry across the Red Sea!

Hey! you cannot blame the airline for the fact that they had no aircraft available!

Errr whats that last posting got to do with anything? FYI I very much doubt any passenger knows 'What time were due to be in the air' as you have no knowledge of expected taxy times or slot times. Most crew aim to leave the departure gate at the scheduled time of departure or earlier. If ATC wont let us go because of a slot delay or airfield congestion then there's not much we can do about it really. Anyway, in my experience 90% of delays departure delays are caused by SLF getting lost in the duty free shop!

wWll Mr. Hand Solo, methinks you are living up to your login name! :D :p

Departure time is that time when the aircraft has its doors closed and the request for pushback and/or start clearance from ATC is being initiated.

Perhaps this is so in your company slasher but in the USA at least it's when the aircraft physically begins to move off the gate.

Do belive that most carriers in Europe operate with "off-block / on-block" times and that is what is printed in their timetables.

With the company I work for anything above 5 minutes is deemed a delay, and anything more than 15 minutes must have the appropriate delay code accompanied by a note explaining what happened in our daily report.

Our aircraft are not ACARS equipped leaving room for a bit of "creativity" with the times. It should also be noted that ACARS transmitted times can be altered if you wish so. Airlines have been known to do this to some degree, in an effort to come out on the top of the list of on-time performers. http://www.flightcrew.dk/grafik/jni.jpg

Departure time is when the aircraft pushes back. If it pushes back on time, it may then go to a remote stand and await a departure slot for an hour and still be deemed to have departed on time. To be fair it did in fact depart on time and further delays are down to air traffic restrictions.

I know a certain airline at a certain Middle Eastern airport who fiddle the block times transmitted back to their home base via ACARS all the time....

And, what's to stop the Capt. releasing brakes and holding the a/c against the tug?

<AAAAArrrgh - flood control>

BRUpax same thing. Door closed, ramp retract, ATC pushback request and actual pushback are supposed to be all done in 60 secs. Thats the theory. Of course it never works in practice.

ACARS can be cheated by releasing the brakes before main door closure. Closing the doors with brakes not parked will give an ACARS time off blocks (ACARS time is doors or brakes, whichever occurs later). But this means talking to the ground engineer first.