744 takeoff problem

[Deano777]

Hi everyone
Last November, my wife and I were returning from a month in Australia, we have been 3 times and always flown BA, on this particular occasion we flew from YSSY to WSSS then WSSS to EGLL, it was BA016 on the 29th November (<--- irrelevant, unless the Captain is seeing this :D), Im pretty sure at Singapore we departed from rwy 02L out into the ocean.
Anyway, it was around midnight on the time of departure, we taxied to the hold where I saw a Singapore 744 on short finals, after it landed we failed to 'line up and wait', we just sat there, I thought 'ok theres another plane on finals' but there wasnt, we waited and waited, eventually we lined up, whenever I fly i always seem to go through some checks of my own, including flaps set for takeoff etc (provided Im sat on or behind the wing), anyway the engines spooled up but didnt give the thrust normally felt and the acceleration was not as fierce as normal, i was watching out the window as we went down the runway thinking ok 'rotate' but we never, we were still going down the runway, and still going down the rwy, and still going down the rwy, at this point I thought that we must be nearing the end of the rwy by now, I know 02L is some 13,000ft in length? so pretty long, I then felt the PF pull back pretty hard on the controls, we never really got off the ground, then I felt a further yank we just lifted off when I saw the end of the rwy flicker past us, and we still were not climbing, I had a wave of panic come over me at this point, I did not let the wife see it, the nose then leveled off for a short while, I guess to build some airspeed before re-entering the climb (this looked like about 200ft off the ground in my estimations). we then made a very shallow climbout up to about FL100 when all seemed to be normal.
Basically does anyone know why this takeoff may have occured the way it did? could it have been and what is a de-rated takeoff? is it to save fuel only? is the take-off thrust set by the FMC? what happened just wasnt right and I was wondering if any 744 or any other pilot has any thoughts on it

Thanks in Advance

Dean.

[wing_nut1]

:oh: sounds a bit suspect if you ask me. Can you get in touch with the airline or surf it on the net about take off's for the particualr aircraft? Must be something out there on the net.

If you saw the end of the runway when you only just taking off that to me would seem to close for a regular take off!!!

Maybe the pilot past the point of 'no return' before he realized there was a problem? (im sure there is such thing:confused:).....it doesnt sound like the average take-off anyway!!

[mutt]

Don’t work for BA, but I would say that you were just introduced to the world of Derated Takeoffs.......

Primarily these are done to increase engine life by reducing the stresses on takeoff, the aircraft didn’t need all of the 13,000 feet for takeoff, therefore the excess runway length is traded for a power reduction.

Getting to see the runway end lights is quite normal, perfectly legal and safe :):)

As for hows it done, a takeoff analysis would show the crew how much weight they could takeoff with if:

1: They used a fixed derated engine, 10% or 20% less than the installed engine.
2: The temperature was hotter than it actually was. This hotter temperature is then used, this is called the "assumed temperature" method of reducing thrust.

The crew would input the weight, engine rating and temperature into the FMS, which in turn would provide speeds and power settings. Combining both methods allows us to reduce engine thrust by up to 45% if the conditions are suitable.

Finally remember that your perspective from a passenger window is completely different from that of the crew who know exactly that they have "planned" to do.

Cheers.



Mutt.

[slingsby]

Spot on Mutt

Singapore not alone in being a hot, humid airfield. Nice long runway, heavy aircraft, long flight, why not derate thrust, use available take off length, save fuel, economy climb.

All take off performance calculations have taken into consideration that given temperature, weights, available distance etc that even if an engine failed you would be able to still take off using the same runway distance, albeit a bit closer and lower to the end of the runway. Pefectly normal and completely safe operation, which off track is practiced every 6 months in the sim.

Deano777, had there been a problem, you wouldn't have continued to Heathrow but returned to Singapore. As Mutt stated, seeing the runway lights close after rotation is normal for long haul ops, especially heavy aircraft. Your perspective view is somewhat different to ours, may I suggest a video of long haul ops, this will give a better view of the driving end and what we see and do. I can't think of any offhand but somewhere on the web or library you should be able to purchase one. Alternatively, fly with Emirates, I beleive they still have the nose wheel camera, which is switched on for take off and landing, and is available for all to view on the IFES.

[Deano777]

Hi all
Thanks for your replies, a de-rated takeoff is what I suspected (see original post) but seeing us lift off just before the rwy end lights is a tad unnerving :D I have flown on the 744 loads of times and out of WSSS 6 times and have never had a de-rated takeoff yet, i knew there wouldnt be anything wrong with the aircraft but just the way we were delaying ourselves before takeoff felt like the crew were unsure of the inputs to FMC etc etc and were checking them.
End of the day we got home safely as always with BA and will always fly to Oz with BA/QF.

Anyway that cleared it up for me thanks guys


Dean.

[slim_slag]

The most recent time I flew out of SIN was on an Aeroflot IL-96 :eek: and it appeared that we saw the grass at the end of the runway from the same height as the person who mows it. I just blamed the Russian engines and decided the best thing to do was drain the vodka trolley :D.

[Final 3 Greens]

Deano

we just lifted off when I saw the end of the rwy flicker past us

Bear in mind that you are moving at over 1 miles per 18 seconds at lift off speed in a 744 and a few seconds takes you a relatively long way, so that seeing the REIL pass a few seconds after lift off seems close proximity, but in fact represents quite some distance.

I must admit that I didn't understand what a derated take off felt like until I experienced one from the jumpseat and it was illuminating to have the benefit of knowing what was about to happen.

[Captain Airclues]

Deano777

I have operated the BA016 many times and cannot remember ever having to use full power out of Singapore. The 744 can use derated thrust even at max structural weight.
There could be several reasons for the delay at the holding point but I doubt that the crew being unsure of the FMC inputs was one of them. BA operate a 'late close-out' procedure where the final weights are sent to the aircraft via ACARS during taxi. This information has to come from the operations centre at Hong Kong, and there is sometimes a delay in this. There is a very strict ATC 'slot' system at WSSS as the flight has to fit in with the other Far East flights. It is possible that they either arrived at the hold early (to achieve an on time departure) or that they missed their slot and had to negotiate another one.
I doubt whether the PF 'pulled back pretty hard' on the controls. If he had done so at that weight he would almost certainly have scraped the tail.
I'm sure that if you had expressed your concerns to the crew, one of the off duty crewmembers (a double crew is carried) would have put your mind at rest.

Airclues

[Deano777]

Thanks for your reply guys (and sorry for my late reply)
When we rotated the 744 just stayed with the nose up attitude and did not lift off the ground, (this is when I started to get a tad worried) the hard pull I felt seemed like it was done to lift us off just before the end of the rwy, I have flown 744's several times into WSSS and have never experienced this, but thanks Airclues for clearing things up for me, I will just have to watch and learn on my next visit to Oz next year :D

Happy Flying

Dean.

[PAXboy]

This sounds similar to departures from Johannesburg (JNB). Although more power is needed, due to the elevation (some 5,500 feet above sea level) and the higher temperatures, you are on the runway much longer.

Sometimes the flight deck will advise pax before departure, "Do not be surprised that we appear to be rolling for longer than usual, this is because of the height and temperature in Johannesburg"

From memory, a 744 departing LHR for JNB will roll for about 35/40 seconds before rotating. At JNB the same type will roll for about 50/55 seconds and it is a loooong slow climb out. I have also experienced that realisation that the nose has lifted but the main gear are still on the ground for a moment or two, before she lifts clear.

The only time I was worried, was on a 744 departing Kai Tak and what sounded like a compressor stall on the starboard wing (just outside the window). We had only just rotated and it was a heck of a bang and she gave quite a shake but, of course, pulled on up.

I guess that's the problem for us that have travelled a fair amount and take an interest in these things but do not know as much as we should like.

My late grandmother knew nothing (and knew nothing about everything!) One time she was departing JNB and we watched the machine roll (VC-10) and then the take off was rejected and they went back for another go, departing safely. She responded to my mother's letter of enquiry, "Oh yes we did stop suddenly and go around again - but I thought that they always do that." Good old gran, have another G&T. :zzz:

[Pnooze]

As an Airbus 340 pilot who operates at heavy weights on a routine basis i have to concur with the comments from other pilots on this topic. A take off roll of 50 seconds at Joburg is quick compared to the 70 seconds we usually do!! ;)

[Tyke returned]

Any body know the comparative stats for DEN? I did the BA flight back to LGW last year and there must have been time to serve dinner during the take-off roll.

[slim_slag]

I've been on a flight departing from DEN where one of the pilots came on and said they had to turn the A/C off because they wanted the power for take off. The new airport too, so not long ago.

[Captain Airclues]

Switching off the AC packs on a 744 can give an extra 2000kgs take-off weight, as the packs take bleed air from the engines. Some airlines (eg BA) use APU air to drive the centre pack during take-off and so retaining AC but not affecting the thrust.

Airclues

[Hilico]

A really really stupid question: I've never heard of a 744, so do you all mean a 747-400?

[Globaliser]

Hilico: A really really stupid question: I've never heard of a 744, so do you all mean a 747-400?Not a stupid question at all, just use of familiar (to us) jargon. From the list of IATA codes at www.airlinecodes.co.uk/acrtypes.htm (http://www.airlinecodes.co.uk/acrtypes.htm):-741 Boeing 747-100 pax
742 Boeing 747-200 pax
743 Boeing 747-300 pax
744 Boeing 747-400 pax
747 Boeing 747 all pax models
74C Boeing 747-200 Combi
74D Boeing 747-300 Combi
74E Boeing 747-400 Combi
74F Boeing 747 all Freighter models
74J Boeing 747-400 (Domestic) pax
74L Boeing 747SP
74M Boeing 747 all Combi models
74R Boeing 747SR pax
74T Boeing 747-100 Freighter
74U Boeing 747-300 / 747-200 SUD Freighter
74V Boeing 747SR Freighter
74X Boeing 747-200 Freighter
74Y Boeing 747-400 FreighterPnooze: As an Airbus 340 pilot who operates at heavy weights on a routine basis i have to concur with the comments from other pilots on this topic. A take off roll of 50 seconds at Joburg is quick compared to the 70 seconds we usually do!!I thought that was just because it took that long to fill your lift balloon with hot air from those hairdryers ... <ducks rapidly>

[Hilico]

Globaliser, thank you for making it so clear - I've copied your post to a separate file for future reference.

[Pnooze]

Globaliser,

Actually, the 340 is powered by Flymo lawnmower engines, so get your facts straight!!! Not only a 73 second roll in JNB last week but then 48 mins to reach FL330. It was like watching grass grow:rolleyes: