kaitak From Ireland, joined Aug 1999, 12161 posts, RR: 35 Reply 3, posted (1 year 9 months 3 weeks 8 hours ago) and read 24298 times:
I don't know, of course, but I'd be quite surprised if they performed a takeoff from an intersection; in icy conditions and with a high weight (for nonstop to CMB), you'd want every last inch, in case you need to abort (and it looks like they needed it!); I always thought that full takeoff power was a requirement during icy conditions?
GSPSPOT From United States of America, joined Sep 2003, 2838 posts, RR: 2 Reply 8, posted (1 year 9 months 3 weeks 7 hours ago) and read 23765 times:
I remember being on one of KL's old 743 combi a/c out of ORD on a night departure once, and wondering during the takeoff roll if we were going to go off the runway.... Then it climbed shockingly slowly, to the point that I wondered if there was a problem. I have no idea why that particular a/c took off that way. I understand the earlier A340 family a/c regularly perform this way, but it was a shock on a 747!
BA777ER236 From United Kingdom, joined Sep 2006, 278 posts, RR: 8 Reply 10, posted (1 year 9 months 3 weeks 6 hours ago) and read 23551 times:
Quoting skipness1E (Reply 2): I was shocked to see a BMI A319 in a similar position not too long ago, I actually ducked.
In that case, you have NO idea of modern aircraft performance. There is NO way that a BMI captain would have taken an intersection departure without knowing and using the performance figures from that intersection! In any event, the performance would have allowed for an engine failure at V1 and clearing an altitude of 35 feet at the end of the TODA(take off distance available) which would be at the end of the 'clearway'. There is no way that you could be standing in the 'clearway', so the A319 - even on one engine would have been at least 28ft above your head (unless you are over 7ft tall!), so to 'duck' would be somewhat over cautious! None of the 09 departures would have been CLOSE to the scenario I have just described anyway!
Quoting kaitak (Reply 3): I don't know, of course, but I'd be quite surprised if they performed a takeoff from an intersection; in icy conditions and with a high weight (for nonstop to CMB), you'd want every last inch
How icy was it? How could you possibly know? Just because the weather was cold has NO bearing on the runway braking action. The runways at LHR are high friction surfaces and are treated for ice as necessary, but it is VERY rare to have breaking action assessments and reports that are less than medium. If so, then such doubts as to the runway state would have been communicated to the crew and they would have planned accordingly.
All jets taking off at LHR (and other airports with long runways) will use take off performance that will maximise engine life, which means using the lowest amount of thrust (known as 'derated' or 'flex') that will achieve a 'safe' take off. There are several criteria here, but in general terms, the maximum derate permissable is equivalent to 25% of maximum rated thrust. When derating, there must still be sufficient runway remaining to either stop or continue at V1. If the take off is continued, there must be sufficient thrust available from the remaining engine (still at 'derated' thrust) for the aircraft to climb to the 'screen' height of 35ft at the end of the 'clearway' at V2 and then continue the climb to the engine out (EO) accelaration altitude (usually 1000ft above airfield level), accelerate, retract flaps and then climb to the minimum safe altitude (MSA). MSA is usually taken as sector safe altitude (SSA) within 25 nm of the airport. If there is insufficient terrain clearance during this manoeuvre whilst following the Standard Instrument Departure (SID), then there will be a published 'emergency turn' which will ensure terrain clearance and the crew will be obliged to follow it in an engine out scenario.
It is not uncommon for long haul jets to take most of the runway to get airbourne a long way down the runway using the above criteria and a 'derated' take off. For short haul jets it is less common, but not unknown!
skipness1E From United Kingdom, joined Aug 2007, 2810 posts, RR: 1 Reply 17, posted (1 year 9 months 3 weeks 5 hours ago) and read 23007 times:
Quoting BA777ER236 (Reply 10): In that case, you have NO idea of modern aircraft performance. There is NO way that a BMI captain would have taken etc etc
I have every idea actually, I was however shocked as it was VERY unusual to see an A319 as low as that A340 in the picture. I didn't consciously think it was a goner but I recall taking a step back as it was unusually low in comparison with all other departing traffic. In seven years of around and about LHR that was a first.
I was also rather happy to depart on a an A380 off 27L (same runway, opposite direction), from S4 ! I am well aware of the performance characteristics involved thanks, however it's rather human on such an occasion to step back and exclaim "Blimey that's a little out of the ordainary guv'nor!"
fiscal From Australia, joined Oct 2009, 294 posts, RR: 0 Reply 18, posted (1 year 9 months 3 weeks 5 hours ago) and read 22804 times:
I must admit that I was wondering when we would get off the ground when I flew Air Asia X a340 out of Stanstead. It's funny how that after traveling on many flights, you get a sense for what is normal and what is different.
CX Flyboy From Hong Kong, joined Dec 1999, 6447 posts, RR: 56 Reply 19, posted (1 year 9 months 3 weeks 3 hours ago) and read 22486 times:
Seeing how low they are, you really have to wonder whether they could have suffered an engine failure at V1 and still made it. The Air Canada A343 used to depart HKG a bit like this at the peak of summer. Russian cargo flights also seem to depart like this....they must adhere to a completely different set of performance rules as the rest of the world!
SASMD82 From Netherlands, joined Mar 2007, 605 posts, RR: 0 Reply 24, posted (1 year 9 months 2 weeks 6 days 19 hours ago) and read 17435 times:
I must admit that the A340-300 usually needs a lot of runway. Then why does AF operate them on the CDG - SXM - CDG line? KLM make a fuel stop at BON because of the lenght of the runway at SXM.
But why is the A340 the only plane 'accused' of its long take off rolls? Back in the late 90s I loved to stand at the end of the runway at Schiphol to watch the 747-200/-300 departing during summer. Those dramatic take-offs were awesome! (Lifting up at the end of the runway and climbing out very slowly). Last summer we only had those Kallita B747-200s, awesome!