Page 9 - Aerotech News and Review 4-1-16

ARMSTRONG, from 8 RQH9HU\ODUJHDLUFUDIWWKDWEDUHO\¿W ¿UVWKDOIRIWKHWKFHQWXU\LQFOXGLQJ
within the current infrastructure we Ludwig Prandtl. Prandtl was a German
NASA photographs by Lauren Hughes have would still want to solve those whose research is considered a foun-
problems the exact same way we are dation of modern aerodynamics. The
'DYLG/HH*ROGD1JX\HQDQG6FRWW*OHDVRQUHFRYHUWKH3UDQGWO'1RDIWHURQHRILWV¿UVWÀLJKWV now.” aircraft’s designs are based on glider
concepts of German brothers Reimar
However, times are changing. and Walter Horten and the conclusions
“There has been a recent trend for of NASA aerodynamics pioneers R.T.
airliners to be smaller than the maxi- Jones and Richard Whitcomb.
mum size. We’re seeing companies
move away from the ultra large ca- Aeronautical engineers labor for
pacity airliners. With that move, the ways to gain a few percentage points
Prandtl-D wing offers a very viable so- RIHI¿FLHQF\DQGWKHLGHDWKDWDGLIIHU-
lution. We think in the long term most HQWVROXWLRQFRXOG\LHOGVXFKHI¿FLHQF\
aircraft will use this solution because of “people can’t conceive it can be true,”
its minimum drag for a given amount Bowers said.
of structure. The same structure with
22 percent longer wing span will result As Bowers and his colleagues con-
in 11 percent less drag on the aircraft.” tinue to build the case for the concepts
Flight data thus far supports the air- proven with the Prandtl-D, the time
FUDIWZLQJGHVLJQVROXWLRQV¿UVWSUR- may be coming for a new paradigm in
posed by aeronautical engineers in the aviation, Bowers concluded.

WKHRYHUODSSLQJRIELUGVLQÀLJKWLVWKH aeronautical thought and is now de- “The Prandtl-D solution contends 7KH3UDQGWO'1RUHVHDUFKDLUFUDIWLVEHLQJUHDGLHGIRUQHZÀLJKWWHVWVWKLV
optimal aerodynamic answer. veloping wider acceptance. that once you pick a certain size of VXPPHU,WKDGLWV¿UVWÀLJKW2FW
aircraft that the purely aerodynamic
The Prandtl-D wing, which is the “No one has criticized the math in answer is no longer sufficient. The
foundation of the experiment, will re- our paper,” Bowers said of peer re- amount of payload the airplane is go-
duce aerodynamic drag by at least 11 viewers. “No one has found any sort ing to carry and the amount of structure
percent, Bowers said. Aircraft that use of defect in the logic. The revolutionary necessary to carry that payload changes
WKH3UDQGWO'FRQ¿JXUDWLRQZLWKRXWD part of this is it allows aircraft design- the answer.”
traditional fuselage and tail could see ers to completely eliminate the tail on
IXHOHI¿FLHQF\JDLQVRIPRUHWKDQWKUHH DQDLUFUDIWDQG\RXHQGXSZLWKDÀ\LQJ The new research does not preclude
times that, or divide gains to obtain in- wing. All of the problems that have tra- traditional methods.
creased speed or range using the same GLWLRQDOO\EHHQDVVRFLDWHGZLWKÀ\LQJ
amount of fuel, Bowers said. wings, and the reason we put tails on “There are still many situations
airplanes, appear to be solved by do- where the old solution is the correct
Thrust at the wingtips is an idea that ing this.” one. If you have a certain constraint on
flies against the winds of traditional wingspan, the old solution is the right

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April 1, 2016 Aerotech News and Review 9

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