EDWARDS AIR FORCE BASE, California --
The skies above the Aerospace Valley has seen some of the most iconic aircraft in aviation history. However before they etch their place history books, these aircraft undergo weeks of ground tests.
These ground tests are conducted in numerous locations in or near the flight line at Edwards Air Force Base, California. Ground tests provide engineers with vital information from a number specialized facilities. One such facility on Edwards is the Installed Engine Test Facility Horizontal Thrust Stand.
“It's the only known free-world thrust stand of its nature,” said Gary Peddecord, Lead Electronics Technician with JT4 for the 812th Aircraft Instrumentation Test Squadron. “It is a roll-on roll-off facility, we only deal with thrust numbers we do not deal with aircraft data parameters. We can have an aircraft on here in the morning, and it can depart station that afternoon or evening when we’re done testing.”
Initial construction on the thrust stand was completed in 1955, the same year as Disneyland opened, noted Peddecord, who has been working at the facility since 1997. Peddecord and other engineers observe the test operations from an underground control room roughly 100 feet away from the aircraft. There, behind concrete walls a foot thick and a metal, vault-like door, they are able to work relatively quietly and communicate and away from loud, roaring jet engines.
“We're pretty safe down here, we have all the instrumentation needed to translate the load cell energy into raw pounds of data, which is raw pounds of thrust,” he explained.
Test personnel in the control room are able communicate with personnel on the aircraft via VHF/UHF channels. The data from the thrust stand is fed to computers in the control room where computer software converts values from electric figures into pounds of thrust. Throughout its history, the thrust stand has hosted aircraft such as the T-38 Talon, F-16 Fighting Falcon, and F-22 Raptor among others, possibly more exotic aircraft, pictures of which adorn the control room’s walls.
Besides fighters, the facility can also test tankers, bombers, transport and cargo aircraft, ranging in size from “Cessna to C-5,” Peddecord added.
Aircraft on the stand are held in place by specialized chocks. Peddecord explained that the stand is able to accommodate any jet aircraft with a “tri-cycle” style landing gear configuration. The chocks are, of course, painted the ubiquitous “test orange.”
“We call those ‘boot chocks,’ because they are kind of like boots on your feet,” he explained. “Boots on the main landing gear of an aircraft; the aircraft's not going anywhere. Those were built as part of an F/A-18 program for us many years ago. Any fighter type aircraft…we've pretty much tested them all using these orange aircraft boot chocks.”
During a recent thrust test operation, Peddecord and his team provided their expertise to Air Force Test Pilot School students with a T-38 as a part of their test management project. A small team of students utilized the facility with one student in the control room and two on the aircraft.
“This is kicking off our testing that we're going to be doing. We're out here with the T 38 on the engine run pad getting some ground data,” said Capt. Cameron Clites, TPS Class 20-B student. “Today is just kind of a calibration day for our team to get some good ground test data at 1 G, zero ground speed, and see if we're going to have a good path forward over the next two weeks.”
The T-38 pilot progressed through different levels of thrust while noting throttle position while thrust readings in the control room were annotated. The data collected at ground facilities is essential for engineers and test pilots alike. It provides them with information much more accurately than simulated computer modeling.
“It's given us raw thrust data that we could not collect otherwise,” Clites said. “To actually come out and be able to gather empirical data…it's critical. We definitely couldn't do this part of the test plan without a facility like this.”
Besides the valuable test data it provides, the history and importance of the thrust stand is not lost on Clites, who recognizes the role it has played in shaping Edwards AFB’s legacy.
“It's very cool, I think you could say that about nearly almost any building here on Edwards,” he said. “A lot of history, a lot of flight test history; just the names that you hear of people that have been walking these streets and walking the hallways.”
“It really is humbling…it's crazy to think that it's been around since the 50s, we're still using it today. And the aircraft's been around just as long, but here we are in 2021 testing something new, something exciting for us at least, and getting to use something that I'm sure people's grandfathers have been using, is pretty cool, pretty unique.”
Since entering into service for the test enterprise in the late 50s, the horizontal thrust stand has seen hundreds of engineers, test pilots and airframes. Supporting the thrust stand operations and “getting the job done providing customers with the data they need in a timely fashion,” is still as rewarding as ever, Peddecord said. More importantly however, he is also ensuring the thrust stand’s legacy continues with a new generation of engineers.
“This is not only an active data collection run that we're doing right now, it's also a training session,” Peddecord said. “Today, a rewarding aspect is training other people to carry on for me.”