Wing Morphing and Fuel-Efficient Planes
The allure of wing morphing has been around since man first noticed how birds fly.
Drastically change the shape of a wing in flight
and you get something that can potentially fly fast as well as be
agile when slowly coasting. But the U.S.’s first real stab at producing
a variable wing was on the F-111, a swing-wing aircraft
that was not known for being maneuverable.
Things got better with the
Navy’s F-14 Tomcat. The highspeed
interceptor was fast enough
to go toe-to-toe with Migs but
could extend its wings to turn
sharply, dogfight, and make lowspeed
carrier landings.
Fast forward to today. Darpa’s
Morphing Aircraft Structures program
has generated designs such
as folding wings that vary their
wingspan length, aspect ratio,
sweep angle, and other qualities.
Researchers have tried other
morphing concepts such as partially
inflatable wings as a means
of controlling roll.
But what is billed as the first
“cost-effective and practical
morphing wing” is part of an
unmanned aircraft called V-Star,
for VTOL Swift Tactical
Aerial Resource.
Frontline Aerospace
Inc. calls the
UAV a Humvee of the
air because it can
theoretically work in
several roles besides
its main job of hauling
gear to frontline
troops.
Frontline says the
weight, complexity, and reliability
penalties associated with morphing
a wing have so far been
problematic. To keep things simple,
it came up with a set of folding
extensions that flip out to let
the plane loiter at 275 knots and retract for dashes at 400 knots.
The V-Star’s boxplane-type
design tends to promote fuel
efficiency because of its inherent
minimum induced drag for
a given lift and span. But the
plane also sports a special kind
of recuperator to further promote
economical operation. The
recuperator, a heat exchanger,
extracts heat from the engine
exhaust and transfers it to the
compressed engine air before
combustion. Frontline claims
this can double the engine’s
thermal efficiency. The patentpending
design also manages
to keep down weight by using
hypodermic-needle material for
heat transfer. Company officials
claim the device can improve fuel
consumption by as much as 40%
and weighs less than 40 lb.
It will be awhile before V-Stars
are ferrying gear to troops. Frontline
is working on a 50% scale
version for wind-tunnel testing
and hopes to complete those
tests next year.
Frontline Aerospace
Inc.
Broomfield, Colo.,
frontlineaerospace.com
Wired Magazine blog entry
on Frontline’s plane: tinyurl.com/52n64k
Machine Design blog entry on
Frontline’s announcement: tinyurl.com/497lul
V-Star uses belts and multiple
driveshafts, so either of its Rolls
Royce Model 250
turboshaft engines
can power both the
lift and pusher fans. |