winglets on its Dassault Falcon 50 test-bed aircraft on
AeroShell Square at AirVenture 2010
For the general public, winglets-those
smaller vertical surfaces rising from the wingtips of airliners-have
become a familiar sight. But they were slow to catch on and find a home
in modern aircraft.
The idea was first promulgated by famed
NASA aerodynamicist Richard Whitcomb, partly in response to the fuel
crisis of 1973.
NASA didn't start testing prototype winglets (on a KC-135, the military
tanker version of the Boeing 707) until 1979. Not everyone, however, was
A young engineer named Burt Rutan read
the NASA report and made winglets an integral part of his VariEze, which
wowed crowds and changed the whole course of the homebuilt movement,
right here at Oshkosh-35 years ago, in 1975.
The purpose of winglets is to control the
circulation of air around a wingtip, from the higher pressure below to
the lower pressure above; when properly designed and configured, they
can actually recover a significant amount of energy from this wingtip
vortex-while at the same time making the vortex itself somewhat less of
a threat to other following aircraft.
Burt Rutan has always been known for
making the most efficient use possible of every element in his designs,
so in the Ezes, as well as his later designs like the Defiant and the
Beech Starship, the winglets serve the additional function of vertical
Beyond mainstream to the infinite wing The Seattle, Washington, firm Aviation Partners Inc. pioneered and
patented the ideal of "blended" winglets, in which the winglet
flows smoothly up as a curved extension of the aircraft wing, rather
than being attached at right angles.
Its winglets appeared initially on
business jets, but they were soon adopted by airliner builders, most
notably Boeing; in an era of ever-increasing prices for jet fuel, a
savings of just a few percent in operating cost might mean the
difference between an airline's financial success and failure.
This year, API is developing "spiroid
winglets," an attempt to approach the Platonic ideal of an
"infinite wing"-one with no energy-robbing wingtips at all.
To accomplish this, it's invented a
winglet that curves up from the wingtip, then wraps inboard and around
to reattach to the wing some distance inboard of the tip.
Recycled, refined, and perfected Entire "wraparound" wings have actually been built and
flown (as long ago as 1904, with the Bleriot Model III), but they aren't
practical for high-speed aircraft.
API hopes that its new design can realize
a significant improvement in performance and fuel economy over current
winglet technology. At present it's in the flight-test stage, with the
initial application planned for "one of the bigger bizjets."
If nothing else, the new winglets-with
their delicately curved and beautifully polished surfaces-can rank as
examples of the finest aviation sculpture.
You can see API's spiroid winglets on its
Dassault Falcon 50 test-bed aircraft at the southeast corner of
AeroShell Square. Just look for the big three-engine business jet with
the strange-looking wingtips.
DATES: 2014: July 28-Aug. 3;
2015: July 20-26; 2016: July 25-31; 2017: July 24-30