787/A380 takeoff attitude
Thread Starter
Join Date: Jan 2002
Location: ---------->
Posts: 146
Likes: 0
Received 0 Likes
on
0 Posts
787/A380 takeoff attitude
Hi Everyone
I live *very* close to an international airport, and have noticed that the 787 and A380 are considerably quieter than the aircraft they have the potential to replace.
The difference between the 747 and the A380 in particular is really impressive.
I noticed a Virgin 787 go off yesterday, and it may be my imagination, but it seems to fly a much shallower departure very soon after lifting off.
The same goes for the A380; the 747 seems to shoot straight up, engines screaming, whereas the A380 seems to have a more sedate, leisurely sort of lumbering depature. Seems to pass by lower and much quieter.
So I assume the modern engines contribute to the lower noise levels, but are the aircraft designed/powered to the extent that they can fly "shallower" departures and require less thrust? or is it my imagination?
thanks
EGLD
I live *very* close to an international airport, and have noticed that the 787 and A380 are considerably quieter than the aircraft they have the potential to replace.
The difference between the 747 and the A380 in particular is really impressive.
I noticed a Virgin 787 go off yesterday, and it may be my imagination, but it seems to fly a much shallower departure very soon after lifting off.
The same goes for the A380; the 747 seems to shoot straight up, engines screaming, whereas the A380 seems to have a more sedate, leisurely sort of lumbering depature. Seems to pass by lower and much quieter.
So I assume the modern engines contribute to the lower noise levels, but are the aircraft designed/powered to the extent that they can fly "shallower" departures and require less thrust? or is it my imagination?
thanks
EGLD
Join Date: Jan 2004
Location: England
Posts: 762
Likes: 0
Received 0 Likes
on
0 Posts
I agree. Have watched a few 787s depart and they are very quiet compared to their predecessors and seem to have initial shallow climb out then normal climb gradient soon after. Maybe it's to do with combination of de-rated thrust, noise reduction and gradually increasing speed to point when normal climb rate is achieved.
I asked this question a few months ago after watching a couple of A 380s departing LHR , in both cases the SID required a significant turn away from runway heading and I had a reply from an Emirates pilot who said that its initial climb performance is not spectacular but ti soon gets going after a few track miles.
Perhaps this is not surprising considering its heritage where the A340 allegedly only got airborne because the earth is round-ire Airbus do not put more power on the wing than they need. This of course leads to the other point that as it has four engines it doesnt have the excess reserve of power a twin needs to climb away after an engine failure. Watch even a heavy 777W (300) depart and it will still climb impresively even ona long trip.
As to 747s I am not sure they perform much better than the 380, a long haul to say Capetown or Singapore sees them rotate well down the runway and climb out at a steeper deck angle than climb angle for some time.
Like you though I have been interested to watch the 787s , as a twin one would expect an impressive rate of climb but that does not seem to be the case with some very shallow climb outs from LHR and most of these aircraft do not yet operate on the really ultra long routes but their performance appears very modest-again due no doubt to some serious derating.
So it seems both new boys (I know the 380 isnt exactly new) trade climbout performance for either or both fuel economy and noise ina more sophsiticated way than their predecessors.
Now if you like real climb out performance you are too late and the last of the SAS MD80 s has sadly left LHR for good and they can no longer be seen as their tiny wings and sooooo long bodies made the intial climb angle look even more impressive.
PB
Perhaps this is not surprising considering its heritage where the A340 allegedly only got airborne because the earth is round-ire Airbus do not put more power on the wing than they need. This of course leads to the other point that as it has four engines it doesnt have the excess reserve of power a twin needs to climb away after an engine failure. Watch even a heavy 777W (300) depart and it will still climb impresively even ona long trip.
As to 747s I am not sure they perform much better than the 380, a long haul to say Capetown or Singapore sees them rotate well down the runway and climb out at a steeper deck angle than climb angle for some time.
Like you though I have been interested to watch the 787s , as a twin one would expect an impressive rate of climb but that does not seem to be the case with some very shallow climb outs from LHR and most of these aircraft do not yet operate on the really ultra long routes but their performance appears very modest-again due no doubt to some serious derating.
So it seems both new boys (I know the 380 isnt exactly new) trade climbout performance for either or both fuel economy and noise ina more sophsiticated way than their predecessors.
Now if you like real climb out performance you are too late and the last of the SAS MD80 s has sadly left LHR for good and they can no longer be seen as their tiny wings and sooooo long bodies made the intial climb angle look even more impressive.
PB
Problem is there's lots of variability on the day due to payload and/or derate but in general as pax has said you'd expect the big twins to climb steeper than the 4 engined types. Can't speak for the 380 but for the 747,777, and 787 the basic take-off technique is to typically rotate towards a target pitch attitude (13-15 degrees typically for a 777 or 787, can't remember the 747), then holding a fixed speed climb to (usually) 1000 feet and only then flattening the climb and accelerating to en-route climb out speed. Whether the 380 has a more sophisticated technique I do not know, but don't forget(?) there is not just noise to think about, there are also other "little" issues like mandatory minimum climb gradients and obstacle clearance to be considered, so I'm not sure too much scope for finessing of the climb just after liftoff.
I suspect the difference in noise level you are perceiving is almost all down to engine design, the 747 suffers from being relatively long in the tooth in that department.
I suspect the difference in noise level you are perceiving is almost all down to engine design, the 747 suffers from being relatively long in the tooth in that department.
