On Mon, 13 Feb 2006 07:10:06 GMT, Jack wrote:

Andreas Maurer wrote:

Any current airliner features an L/D better than 20:1 with engines
off.

Cite?


For a gerneral overview, look here at a phantastic NASA report:
http://www.hq.nasa.gov/office/pao/Hi...468/ch12-2.htm


--- Start quote ---

Abut the B-47 (of 1948!) it says:
The thin, high-aspect-ratio swept wing of the B-47 coupled with its
long high-fineness-ratio fuselage contributed to the high aerodynamic
efficiency of the aircraft. The maximum lift-drag ratio of about 20 is
the highest of any aircraft yet considered in this book, and the
zero-lift drag coefficient was a low 0.0148

707:
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.


747:
The aerodynamic configuration of the 747 is very similar to that of
the 707. The 747 wing has slightly more sweepback than that of the 707
and is of about the same aspect ratio. An improved airfoil design is
also incorporated in the wing of the 747. The maximum lift-drag ratio
of the aircraft, (L/D)max, is estimated to be about 18, as compared
with a value somewhat over 19 for the 707, The lower value of
(L/D)max, results from a higher value of ratio of wetted area to wing
area on the 747 than on the 707.

DC-10/Tristar:
The aerodynamic design of both of the three-engine jet transports is
conventional. The wings of both aircraft have about 35° of sweepback
with aspect ratios in the range of 7.0 to 7.5 and feature transonic
airfoils of advanced design. The wings have double-slotted trailing
edge flaps and leading-edge slats. Lateral control is provided by a
combination of ailerons and spoilers. The spoilers are also used to
control lift and drag when deployed symmetrically. Longitudinal
control of the L-1011 is provided by a variable incidence stabilizer
to which the elevator is mechanically linked. The DC-10 employs
separately actuated elevators and stabilizers. Neither aircraft
employs longitudinal trim tabs. The maximum lift-drag ratio of the two
aircraft is estimated to lie in the range between 17.0 and 17.5.

--- End quote ---



With a little searching it should be simple to fnd the numbers of
current airliners which feature significantly higher aspect ratio,
resulting in an increase of L/D over the older airliners mentioned
here.
I haven't seen any official numbers yet, but for the Airbus 340 max
L/Ds between 16 and 24 can be found on a quick search on the net - I
tend to believe that it's provavly a little over 20 due to the high
aspect ratio of the 340.







Bye
Andreas