View Full Version : B738 one pack off takeoff N1 diffrentce?
cts52
15th Aug 2010, 11:25
B738 with left pack off takeoff N1 diffrentce?
V1 if biger than the V1 with two packs nornal.
when takeoff with left Pack off ,Reduced thrust assume temp 45`C
fmc caculate N1 L95.3/ R94.0 ?
why left N1 is higher?
how much diffrence N1 is not acceptable for take off ?
Thanks!
RAT 5
16th Aug 2010, 12:17
FMC calculates balanced field speeds. No idea why V1's should be different. Do you use de-rates or only assumed temp's from max thurst; and from what max N1%, 22k, 24k or 26k? If you look at V1 for different derates, this could be an answer.
For difference in N1% the reason is the left N1% is showing Bleeds Off values and thus is higher than the Bleeds On value of right engine. However, the difference on our a/c is only 8%, so your numbers are curious.
B777Heavy
18th Aug 2010, 14:54
It should be the other way around...ie with left pack off, the left N1 should be lower. This is because a slightly higher N1 is required to sustain the airplane and the bleed air/pneumatics etc.
The second part, are you talking about a packs off take off?
N1's - cts is right. Try it next time?