No. Of Jets & Slow Down Time

Wed Jan 05, 2000 11:29 am

my question is... can planes with more number of engines or more powerful ones stop more in time? perhaps an A340 or 747 can actually use a shorter runway to slow down than a 330 since their jets are more powerful to generate stronger reverse thrusts?
Das Flugzeug
Posts: 156
Joined: Tue Nov 09, 1999 1:17 pm

I Don't Think So

Wed Jan 05, 2000 11:50 am

One cannot really compare the 747, as it is a much larger and heavier aircraft, and therefore has no twin engined counterpart.

As for the A340/330, no I do not believe the 340 is able to stop shorter. First, I believe it often comes in at a heavier landing weight = more momentum = more energy required to stop. Also, the 340 does not enjoy a thrust advantage, in fact, I believe it has less thrust. The 340's CFM 56 -5Cs each put out 34,000lbs as opposed to the 330's Trent 700 (example) which each put out 75,000 lbs. What it adds up to is a lighter plane (330) coming in with more thrust to reverse.

Also, I believe thrust reversal only accounts for about 15% of braking force, but I could be wrong about that.

Rock on,


RE: No. Of Jets & Slow Down Time

Wed Jan 05, 2000 2:48 pm

Howabout we compare the 747-400 to the 747-300?
the 400s have more powerful engines, they carry about the same capacity as the 300s, are they able to stop shorter? i know maybe all the avionics add to the weight of the 400, but i assume they are not too significant compared to the boost in their engines over the 300s
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Joined: Fri Mar 16, 2007 1:29 pm

RE: No. Of Jets & Slow Down Time

Wed Jan 05, 2000 4:31 pm

I can't give you a specific answer to your specific question, but to assess the effectiveness of reverse thrust, you must compare the thrust to aircraft weight ratio, plus a whole lot of other things. And as Das Flugzeug offered, wheel braking is much more effective at stopping the airplane. Reverse thrust reduces in effect significantly as the aircraft decelerates below 100 knots.

So there is really no answer to your question other than to compare performance charts for each type.

Best Regards,


RE: No. Of Jets & Slow Down Time

Wed Jan 05, 2000 8:10 pm

Ok thanks, well, i was actually wondering if the A340 can stop more quickly than the A330 since it has got an extra pair of muscles to boost the reverse process. thanks again anyhow...