Tiny New Control Device Improves Lateral Stability Of Airplane | Aero-News Network
Aero-News Network
RSS icon RSS feed
podcast icon MP3 podcast
Subscribe Aero-News e-mail Newsletter Subscribe

Airborne Unlimited -- Recent Daily Episodes

Episode Date

Monday

Tuesday

Wednesday

Thursday

Friday

Airborne On ANN

Oshkosh Day One

Oshkosh Day Two

Oshkosh Day Three

Oshkosh Day Four

Oshkosh Day Five

Airborne Hi-Def On YouTube

Oshkosh Day One

Oshkosh Day Two

Oshkosh Day Three

Oshkosh Day Four

Oshkosh Day Five

Tweet Us The Coolest Things You See @OSH16!
#OSH16Coolest!

It's Alive!: AirVenture 2016 Innovation Preview on Vimeo!

It's Alive!: AirVenture 2016 Innovation Preview on YouTube!

Tue, May 17, 2005

Tiny New Control Device Improves Lateral Stability Of Airplane

"Canted Tabs" Attach To Ailerons

Engineers at Lehigh University say they have designed and successfully flight-tested a new control device that a pilot can use to tailor the lateral stability of aircraft.

Joachim Grenestedt, associate professor of mechanical engineering and mechanics, designed "canted tabs" that are attached to the ailerons.

Grenestedt, an aeronautical enthusiast who owns and flies his own two-seater, said the tabs measure a few inches in length and width. The tabs rotate around an aluminum tube that is inserted into the aileron.

Three tabs were mounted on each aileron for the test flights, which took place at the National Test Pilot School (NTPS) in Mojave, CA. The tabs used in these tests could be adjusted in flight by as much as 30 degrees.

When tested on an Aermacchi AM-3 "Bosbok" observation-reconnaissance plane with 8-foot-long ailerons, the tabs made the laterally unstable aircraft stable, Grenestedt said.

"We took an unstable aircraft, fitted it with the canted tabs and made it stable. When the plane started to side slip, the tabs applied force to the ailerons, causing the plane to bank, or roll, and regain lateral stability."

The Aermacchi does not possess the ability, required of civilian planes, to be rolled upright using the rudder alone.

"Normally, you roll an airplane upright using ailerons," said Grenestedt. "If you lose the primary roll control, then you have to use the rudder." The Aermacchi lacks this back-up feature.

Russ Stewart, a test pilot instructor with NTPS, said the canted tabs enabled him to roll the Aermacchi using rudders only.

"The canted tabs actually made the plane handle properly," said Stewart, who has more than three decades of test-pilot experience. "When they started to deploy to about a third of their range, they turned stick forces to the proper direction."

Stability is the tendency of an airplane to fly straight, level and in an upright position. Positive lateral stability means an airplane has the tendency, if disturbed, to return to its original stable position without corrective action by the pilot. Neutral stability means the restoring forces are absent and the plane neither returns from its disturbed position nor moves further away.

Negative stability means the plane will tend to move further from its original trimmed position, when disturbed.

In the case of the Aermacchi (file photo of type, below), the canted tabs were used to increase lateral stability. However, Grenestedt said the canted tabs could also be used to reduce lateral stability and thus decrease Dutch Roll tendencies and stick forces during cross wind takeoffs and landings. Dutch Roll is an oscillatory motion, combining roll, slip and yaw. These oscillations typically have a short period that can be a challenge for the pilot to overcome. A moderate amount of Dutch Roll, while not fatal, tends to provoke nausea, especially in passengers.

Grenestedt and Lehigh research scientist Bill Maroun modified a set of conventional ailerons for the Aermacchi, and fitted them with the canted tabs.

"We did not know exactly how the Aermacchi would perform," said Grenestedt, who did all the design calculations with pencil and paper. "But the canted tabs showed that they can fix lateral stability deficiencies.

"The largest benefit of the canted tabs may be to serve as a cure for lateral stability deficiencies in existing aircraft, reducing the need for extensive airframe modifications."

Stewart took the modified Aermacchi on two solo flights to verify its safety and flutter resistance. He and Kent Nelson, an NTPS flight test engineer instructor, completed four more flights with instruments to measure linear and angular accelerations, rudder and aileron deflections, stick force, air speed and altitude.

To measure lateral stability, the pilots used various maneuvers, including steady heading side slips, rudder releases, bank-to-bank rolls, and spiral stability flights. In particular, the steady heading side slips showed the effect of the canted tabs. "Deploying half rudder," said Stewart, "the canted tabs changed stick forces from 1 or 2 pounds negative [implying negative lateral stability] to up to 10 pounds positive."

Each test flight lasted about an hour and reached an altitude of 5,000 feet.

Grenestedt said the idea of mounting canted tabs on ailerons was proposed by his friend Sven-Olof Ridder, a fluid dynamics expert in Sweden who is well-known for his airplane and yacht designs.

FMI: www.lehigh.edu

Advertisement

More News

Airborne 07.28.16-Oshkosh Day 4: Mike Huerta Addresses Oshkosh, King Schools

Also: Evolution Aircraft, Sporty’s/Savvy Breakdown Assistance, Comprehensive Jack Pelton Interview, Part 4 FAA administrator Michael Huerta came to town at EAA AirVenture 201>[...]

Dynon Avionics Certifies Outstanding Osh16 Special Event Coverage!!

Leading Edge Sport Avionics Company Pushes The Envelope For Both Sport and General Aviation Markets! Founded in 2000, Dynon Avionics’ mission is to create the best avionics a>[...]

Pilot Training System Teaches Us The Way To Oshkosh 2016 Special Coverage!

Pilot Training System Has A Knack For Educating Aviators... Via Innovative Programs Established in 2011, Pilot Training System’s (PTS) online flight-training solution provide>[...]

Only Sporty's!!! Sporty's Pilot Shop Helps ANN Cover Oshkosh 2016!

Sporty's Pilot Shop Is A Pivotal GA Resource! Sporty’s Pilot Shop was founded over 50 years ago by a flight instructor, and ever since has been for pilots and by pilots. Hal >[...]

Trig Avionics Stacks The Deck To Provide ANN's OSH16 Special Event Coverage

Trig Excels In Affordable Avionics That Fit YOUR Panel! Trig Avionics are experts in the design and manufacture of compact and innovative certified avionics for light aviation. Our>[...]

blog comments powered by Disqus



Advertisement

Advertisement

Podcasts

Advertisement

© 2007 - 2016 Web Development & Design by Pauli Systems, LC