Tech

June 18, 2014

Pumping it up: Airbags take weight in ACTE G-III loads tests

NASA’s G-III flying test bed aircraft rests on three pneumatic lifting devices or “airbags” in preparation for loads testing in NASA Armstrong’s Flight Loads Lab.

 
Technicians at NASA Armstrong Flight Research Center’s Flight Loads Laboratory recently completed structural evaluations on a modified Gulfstream G-III aircraft that will serve as a test bed for the Adaptive Compliant Trailing Edge project.

The loads tests assisted engineers in predicting the levels of structural stress the airplane will likely experience during ACTE research flights. And for the first time, some unusual hardware aided the process: the aircraft was supported by three large inflatable airbags during the tests.

ACTE project researchers have replaced the airplane’s conventional aluminum flaps with advanced, shape-changing assemblies that form continuous conformal surfaces with no visible gaps. Evaluation of the revolutionary new flap system is a joint effort between NASA and the U.S. Air Force Research Laboratory. The advanced flexible trailing-edge wing flaps have the potential to improve aircraft aerodynamic and fuel-use efficiency and reduce airport-area noise generated during takeoff and landing.

FlexSys, Inc., of Ann Arbor, Mich., developed the new experimental flaps for installation on Armstrong’s G-III Aerodynamics Research Test Bed aircraft. Flight testing is expected to begin later this summer.

Principal investigator Bill Lokos, left, and test conductor Larry Hudson review the test checklist prior to initiating the airbag lift of the G-III aircraft.

Before flying the airplane in the ACTE configuration, technicians had to conduct specialized ground tests that involved applying known stresses, or loads, via hydraulic jacks to the aircraft. Scientifically calibrated strain gages provided researchers with highly accurate measurements of the applied stresses, enabling them to predict the structural performance of the aircraft in flight. According to chief test engineer Larry Hudson, “Doing a test of this nature enables us to understand on the ground, by applying certain loads into the airplane, what loads will be experienced in flight under similar conditions.”

Lifting the airplane off the loads lab floor with the three inflatable airbags, the first step in the testing process, helped isolate the airframe from any potential influence of the landing gear on strain-gage data. According to principal investigator Bill Lokos, this method has never been used before in the center’s loads lab.

The airbags were positioned beneath the wings and aft fuselage to keep the main gear tires off the floor so that loading throughout the aircraft’s center wing box structure remained constant. This was necessary, Lokos explained, because increased loading on the wings typically resulted in decreased loads on the gear, which affected the strain-gage measurements and skewed the results of the preliminary equations.

Two of three inflatable bags used to lift NASA’s G-III during loads testing were positioned under the wing root area; the third under the rear fuselage. With an operating pressure of only 3.5 psi, each airbag is capable of supporting 12 tons.

Supporting the G-III with standard aircraft jacks was not an option, he noted, because the effects were even more pronounced than those produced by the gear alone. Alternatively, using a cradle system would have been costly and time consuming. Airbags of the type used to lift aircraft in the field following gear-up landings were already available as proven, off-the-shelf hardware.

Once the G-III was properly positioned, lab technicians applied loads via hydraulic jacks positioned underneath the wings. Structures lead Eric Miller explained that combining known loads values with strain-gage responses in the lab helps researchers develop a database for validating or correcting existing load equations.

“We’ll be able to correlate these data so that we can drive our own load equations and be able to monitor flight loads in real time during ACTE flight tests,” he said.

“This test will either validate those equations,” Lokos added, “or help fix them if we find that they’re off.”

Successful ground testing is key to successful flight-testing. A comprehensive set of data and accurate loads equations will result in more precise flight-test data and enhance safety of flight because researchers will be able to expand the flight-test envelope without exceeding the aircraft’s structural limits.

“It’s important that we have a small error band and that we know what it is, so we won’t cause harm to the airplane while testing the new flap,” Lokos added.

The ACTE effort is part of NASA’s Environmentally Responsible Aviation (ERA) project under the Integrated Systems Research Program of NASA’s Aeronautics Research Mission Directorate. The ERA project explores and documents the feasibility, benefits and technical risk of vehicle concepts and enabling technologies to reduce aviation’s impact on the environment.
 

Armstrong lead engineering tech Aaron Rumsey adjusts a rubber contact pad between the wing of NASA’s G-III and a load cell mounted atop a hydraulic jack.

Click here to see more on YouTube




All of this week's top headlines to your email every Friday.


 
 

 

Headlines January 23, 2015

News: Two Marines identified in deadly California helo crash - Two Marine Corps officers killed when their helicopter crashed during a training exercise in the Southern California desert were remembered Jan. 25 as talented pilots. Greek F-16 crashes in Spain during NATO exercise - Ten people died Jan. 26 after a Greek air force F-16 jet crashed...
 
 

News Briefs January 26, 2015

Navy wants to increase use of sonar-emitting buoys The U.S. Navy is seeking permits to expand sonar and other training exercises off the Pacific Coast, a proposal raising concerns from animal advocates who say that more sonar-emitting buoys would harm whales. The Navy now wants to deploy up to 720 sonobuoys about 12 miles off...
 
 
Air National Guard photograph by SSgt. Annie Edwards

ANG conducts air refueling training with NATO allies in Germany

Air National Guard photograph by SSgt. Annie Edwards A NATO E-3A AWACS aircraft approaches a Utah Air National Guard KC-135R Stratotanker for air refueling during a training flight over Germany on Jan. 13, 2015. Nearly 30 airme...
 

 
Air Force photograph by SrA. Armando A. Schwier-Morales

Ramstein Airmen train with French air force

Air Force photograph by SrA. Armando A. Schwier-Morales Two U.S. Air Force pilots and a French air force navigator discuss the route to the drop zone during a simulated low-level drop Jan. 21, 2015, at Orleans – Bricy Air...
 
 

Marines receive first F-35C Lightning II carrier variant

The first F-35C Lightning II, carrier variant, for the U.S. Marine Corps touched-down on the flight line at Eglin Air Force Base, Fla., Jan. 13, from the Lockheed Martin plant in Fort Worth, Texas, to begin training in support of carrier-based operations. U.S. Marine Lt. Col. J.T. Ryan, Marine Fighter Attack Squadron 501 detachment commander...
 
 

VA announces single regional framework under MyVA initiative

The Department of Veterans Affairs announced Jan. 26 that it is taking the first steps under the MyVA initiative to realign its many organizational maps into one map with five regions to better serve Veterans. The new regions under the MyVA alignment will allow VA to begin the process of integrating disparate organizational boundaries into...
 




0 Comments


Be the first to comment!


Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>