Featured Research

from universities, journals, and other organizations

Tiny New Control Device Improves Lateral Stability Of Airplane

Date:
May 15, 2005
Source:
Lehigh University
Summary:
The tabs, invented by an engineering professor and flying enthusiast at Lehigh University, measure a few inches in length and weight. They rotate around an aluminum tube that is inserted into a plane's ailerons. They also have the potential to decrease Dutch Roll tendencies and stick forces during cross wind takeoffs and landings.

Engineers at Lehigh University 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, the movable control surfaces on the wings that are used to roll an aircraft upright.

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, Calif. 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 position.

In the case of the Aermacchi, 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 is 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.


Story Source:

The above story is based on materials provided by Lehigh University. Note: Materials may be edited for content and length.


Cite This Page:

Lehigh University. "Tiny New Control Device Improves Lateral Stability Of Airplane." ScienceDaily. ScienceDaily, 15 May 2005. <www.sciencedaily.com/releases/2005/05/050513224223.htm>.
Lehigh University. (2005, May 15). Tiny New Control Device Improves Lateral Stability Of Airplane. ScienceDaily. Retrieved September 19, 2014 from www.sciencedaily.com/releases/2005/05/050513224223.htm
Lehigh University. "Tiny New Control Device Improves Lateral Stability Of Airplane." ScienceDaily. www.sciencedaily.com/releases/2005/05/050513224223.htm (accessed September 19, 2014).

Share This



More Matter & Energy News

Friday, September 19, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Virtual Reality Headsets Unveiled at Tokyo Game Show

Virtual Reality Headsets Unveiled at Tokyo Game Show

AFP (Sep. 18, 2014) Several companies unveiled virtual reality headsets at the Tokyo Game Show, Asia's largest digital entertainment exhibition. Duration: 00:48 Video provided by AFP
Powered by NewsLook.com
Apple's iOS8 Includes New 'Killswitch' To Curb Theft

Apple's iOS8 Includes New 'Killswitch' To Curb Theft

Newsy (Sep. 18, 2014) Apple's new operating system, iOS 8, comes with Apple's killswitch feature already activated, unlike all the models before it. Video provided by Newsy
Powered by NewsLook.com
Stocks Hit All-Time High as Fed Holds Steady

Stocks Hit All-Time High as Fed Holds Steady

AP (Sep. 17, 2014) The Federal Reserve signaled Wednesday that it plans to keep a key interest rate at a record low because a broad range of U.S. economic measures remain subpar. Stocks hit an all-time high on the news. (Sept. 17) Video provided by AP
Powered by NewsLook.com
Space Race Pits Bezos Vs Musk

Space Race Pits Bezos Vs Musk

Reuters - Business Video Online (Sep. 16, 2014) Amazon CEO Jeff Bezos' startup will team up with Boeing and Lockheed to develop rocket engines as Elon Musk races to have his rockets certified. Fred Katayama reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins