View Full Version : Lift-drag ratio? (A320)

26th Mar 2008, 18:01
Hi all,

Wonder if anyone knows the various lift-drag ratios for an A320, (or other aircraft) at various stages of flight, for example cruise, decent, landing and whether each extent of flap contributes to a significant change in ratio?
I'm assuming the figure will decrease as the aircraft nears the runway, as more drag is essential.
Thanks - as you may have seen before, I'm trying to find out the info for my c/w, thanks for everyones help so far, I will certianly be plugging pprune quite a bit in my evaluation!


27th Mar 2008, 02:40
767-200 is 17.9:1 (Boeing manual)

Was told by knowledgeable pilot that the 727 was 17:1.

Based on that I'd assume all modern airliners are very close to 18:1.

That would be at optimum L/D speed, which would be about clean min. manuever speed.

L/D ratio would decrease as flaps are extended. As BA 038 showed, based on the data given by the AAIB(108 KIAS, 1800 FPM sink), the fully configured glide ratio, right above stall, is about 6-7:1.

Mike Strutter
4th Feb 2009, 23:35
a320 cruise clean config

max l/d approx 15.2

6th Feb 2009, 17:09
Title says it all. I'm a Boeing person, medium and the smaller heavies.

Drop me a line. These short squat boxes can't do justice to data.

B777 at M0.84 CL=0.500 L/D = 19.26 @ F330
B767 at M0.80 CL=0.500 L/D = 18.34 @ F330
B737-800 at M0.78 CL=0.500 L/D = 17.26 @ F330
B737-400 at M0.74 CL=0.500 L/D = 15.52 @ F330

But with all the variables that kick in, these spot values on their own are might I suggest, close to meaningless. What they burn, what payload they are carrying under certain conditions and how much you still have to pay in bank loans means a lot more.

But you're welcome.


15th Jun 2009, 15:58
What is F330?

15th Jun 2009, 16:17
Flight level, I would guess...

16th Jun 2009, 09:53
Yes it's FL330 you put it as F330 when you submit a flight plan.

If you're still not sure F330 is the same as 33'000 ft on a pressure setting of 1013mb/29.92hPA

16th Jun 2009, 10:06
What is F330?

It's the way we type in the information on our scratchpad when requesting our oceanic clearance via ACARS. You need to free text on line 1 your next best NAT(i.e 2ND NAT E) or whether you would like to go 1 degree STH or NTH if on a random track and on line 2 you enter your maximum FL in the oceanic segment. You enter this field even if it is the same as your requested oceanic FL entered on page1 of your request (along with facility, entry point mach no and ETA at entry). If you request FL380 at the ocean but you are able to make higher in the ocean you simply type in this max flight level (e.g FL400 max) as MAX F400.

Not too long winded a response I trust :)

8th Jul 2009, 14:09
Hi All,

anybody know what the lift-drag ratio of Boeing 707 is?


8th Jul 2009, 14:20
anybody know what the lift-drag ratio of Boeing 707 is?Google is your friend:

"The aerodynamic efficiency of the 707-320B may be judged by the value of the maximum lift-drag ratio, which is estimated to be in the range from 19 to 19.5."

(ch13-3 (http://www.hq.nasa.gov/pao/History/SP-468/ch13-3.htm))

That seems a little high compared to the values posted in this thread for more modern airliners... on the other hand, the same source goes on to say:

"Aerodynamic efficiency of the 767-200 can be judged by the maximum lift-drag ratio, estimated to be about 18. The larger ratio of wetted area to wing area of the 767-200, as compared with that of the 707-320B, results in a value of (L/D) max somewhat lower than that of the older aircraft. The much larger passenger capacity and more efficient engines, however, make the new aircraft more efficient in terms of cost-per-seat-mile."

(ch13-6 (http://www.hq.nasa.gov/pao/History/SP-468/ch13-6.htm))

Which seems to square well with the number given by misd-agin.

19th Oct 2011, 15:27
If you don't mind can you recall which BOEING manual you can find that info ? FCOM FCTM or AFM ... It would be very helpful to find that info

Thanks in Advance

20th Oct 2011, 14:11
Surge - is the question directed to me? I don't know. Went to the training center and asked the question. The guy dragged out the official Boeing book(I don't know which one) that the company uses to decide what information the pilots do, or don't, get in our AFM(reduced from Boeing manual).

Based on inflight experience, TAS, sink rate, etc, etc. I'd guess the 757 and 737-800 wingletted models get about 19.5, or better, L/D.

mathy stated that the 777 gets 19.26:1.

Attempted dual engine flameout landing from a fixed spot(10,000', 250KTS, 35 n.m.) in the 737-800 W/L, 757-200 W/L, and the 777-200. All appear to have almost the same glide performance as all three a/c made barely made the runway.

Based on the performance observed, and mathy's comment, 19.x seems reasonable.