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 October 24, 2014

News: U.S., South Korea delay transfer of wartime control - The U.S. and South Korea have delayed transferring wartime operational control of allied forces by taking on a “conditions-based approach” and scrapping the previously set deadline of 2015.   Business: Exclusive: Lockheed, Pentagon reach $4 billion deal for more F-35 jets - Lockheed Martin and U.S. defense...
 
 

News Briefs October 24, 2014

French moving troops toward Libyan border A top French military official says the country is moving troops toward the Libyan border within weeks and, along with U.S. intelligence, is monitoring al Qaeda arms shipments to Africa’s Sahel region. A French base will go up within weeks in a desert outpost just a hundred kilometers (60...
 
 
Navy photograph

Navy to commission submarine North Dakota

Navy photograph The PCU North Dakota (SSN 784) during bravo sea trials. The crew performed exceptionally well on both alpha and bravo sea trials. The submarine North Dakota is the 11th ship of the Virginia class, the first U.S....
 

 

Boeing announces SF Airlines order for Boeing converted freighters

Boeing announced Oct. 23 that SF Airlines has placed an order for an undisclosed number of 767-300ER passenger-to-freighter conversions (Boeing Converted Freighters). SF Airlines, a subsidiary of Shenzhen, China-based delivery services company SF Express, will accept its first redelivered 767 in the second half of 2015. “SF Express aims to become China’s most respected and...
 
 
LM-C130

Another Super Herc Little Rock Rollin’

  Lockheed Martin delivered another C-130J Super Hercules to the 61st Airlift Squadron at Little Rock Air Force Base, Ark., Oct. 23. Little Rock AFB’s new C-130J was ferried from the Lockheed Martin Aeronautics facility ...
 
 

United Technologies beats third quarter profit expectations

United Technologies Corp. Oct. 23 reported third-quarter profit of $1.85 billion as sales increased across all its businesses and the aerospace giant reported favorable tax settlements. The Hartford, Conn.,-based company said it had profit of $2.04 per share and earnings, adjusted for non-recurring gains, came to $1.82 per share. The results topped Wall Street expectations,...
 




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>