Hush houses keep jet noise contained
By Airman 1st Class Jason J. Brown, 633d Air Base Wing Public Affairs
/ Published April 12, 2010
LANGLEY AIR FORCE BASE, Va. -- The roar of fighter jets is common at Langley, home to one of the oldest and most distinguished fighter wings in the Air Force, the 1st Fighter Wing.
While some may admire the sights and sounds, others may find the booming noise overwhelming and annoying.
Fortunately, the 1st Component Maintenance Squadron's "hush houses" keep the volume to a minimum.
The pair of buildings on the east end of base serves as a testing ground for fighter jet engines undergoing maintenance. The structures are soundproof, allowing maintainers to run the engines at in-flight performance levels, looking for any malfunctions and problems that may arise without disturbing Langley and the surrounding community.
"The hush houses give us a way to get inside the engine as close as possible to see what could happen once it's in the air," said Staff Sgt. Cesar Delgadillo, 1st CMS aerospace propulsion craftsman. "These two hangars are the only area on base where the engines are authorized to operate at maximum throttle."
The hangars facilitate entire jets or removed engines, using a large set of hangar doors and a modular rail and cart system. Once the engine is secured at the end of an exhaust tunnel, the three-Airman team executes a 20-step pre-test safety checklist, ensuring the crew has all necessary tools and personal protection needed to work safely.
Inspecting the hangar for foreign object debris is critical to the safety of the engine and the crew, Sergeant Delgadillo said.
"Once the jet starts running, the air being blown around inside the hangar is intense," he said. "If any debris gets sucked into the engine, it can severely damage the blades inside. We also make sure to secure loose objects that could be blown around and injure us."
The most common problem found in engines is oil and fuel leaks, Sergeant Delgadillo said.
Langley's hush houses contain specially designed pipes, nicknamed "blast tubes," at the entrance to their exhaust tunnels that absorb and deflect sound back into the structure.
"In the past, the noise was loud enough to rattle the homes of local residents, prompting complaints that led to an Air Force investigation," Sergeant Delgadillo said. "The blast pipes further prevent the engine noise from escaping the building."
Two of the maintainers operate the engine remotely from an enclosed "run cab," a mobile trailer outfitted with controls and communications equipment. Another Airman stages in the "ground room," or primary control center, and physically inspects the engine when necessary.
The maintainers use a system of four high-resolution video cameras, strategically positioned around the staging area, to examine the engine for problems and leaks, in order to reduce the necessity of entering the test area during the chaotic test trials.
"It gets extremely loud and windy in here, especially at maximum power testing," said Staff Sgt. Eric Rich, 1st CMS aerospace propulsion craftsman. "Being on the floor during a full-throttle test is an amazing experience."
Even with the screaming noise and blowing wind, the most annoying aspect of the job is the idle time, Sergeant Rich said.
"A lot of time is spent observing readings during testing, which can last hours," he said. "It's boring at times, but it's critical to make sure our jets are ready to fly and fight."
The hangars service an average of eight engines monthly, with test times ranging from 45 minutes to nearly three hours, depending on the nature of the maintenance being performed. In addition to servicing the 1st FW's fleet, the 1st CMS also inspects aircraft engines from other tenant units, including Vermont Air National Guard F-16 Fighting Falcons. The crew serviced 81 uninstalled engines and 49 jets in 2009.