EXACTING COMMUNICATION makes the United States Air Force Thunderbirds one of the best precision flying teams in the world.
A new ground communication trailer built by Nevada Truck & Trailer Repair, Las Vegas, NV, has recently enhanced this communication. It supplies the Thunderbirds with critical air to ground communication as well as providing music and a PA system for the show's commentator. The trailer, which travels with the team to all its shows, is a product of cooperative efforts between Nevada Truck & Trailer Repair, Source Diversified Inc, and the US Government.
Nevada Truck & Trailer designed and built the trailer's frame and main structures. Source Diversified handled design and installation of its elaborate electronics. In addition to meeting the Thunderbirds' needs while the team is in the air, the trailer was designed to pass stringent government codes for airlifting. The trailer is transported between shows on either a C-130 or C-141 cargo plane.
The trailer's primary function is to keep the team's ground crew in constant communication with pilots during air shows--updating them with the latest vitals from ground-level. Deployed near the trailer at shows are sensors for wind speed and direction, air temperature, and altitude.
Basic Design The trailer's diminutive size can be misleading relative to the many tasks it performs. It measures 12 feet long, 80 inches wide, and approximately five feet tall. Mike Abrams, shop supervisor at Nevada Truck & Trailer Repair, designed the all-aluminum trailer from a list of concerns provided by the Air Force and Source Diversified. "We had daily input from the Air Force and Source Diversified during construction," says Abrams.
All doors on the trailer swing open on hinges and then disappear via sliders when the trailer is in use. "This was a major concern from the Air Force," says Abrams. "They didn't want the doors blowing in the wind."
The front of the trailer, where the ground communications and operations officers work, incorporates a two-door design. The top door opens and recesses into the trailer. In the open position, the bottom is used as a workstation during shows.
The front of the trailer is self-supporting with two hydraulically operated landing legs. Legs descend from the front corners of the trailer. Ground crew members are shielded from the sun by an awning that attaches to supports stored inside the trailer.
Abrams designed a retractable hitch, which incorporates a surge brake, into the front of the trailer. The hitch can be released using a positive locking mechanism. Releasing the hitch requires pulling a pin on the right side of the trailer and sliding the unit in or out. Once in place, the spring-loaded pin locks the hitch into its fully retracted or extended position.
The trailer rides on torsion axles and weighs 7,920-lb when fully loaded with all equipment. It is fitted with conventional braking and signal lamps and uses independent flashers as a backup system. Flashers were built into the trailer's electrical system because it doesn't have a dedicated tow vehicle. Most foreign countries use different connectors than the US military, according to Abrams. Flashers provide supplementary lighting for the rear of the trailer when conventional signal lamps can't be used.
Making Music The trailer has can provide sound and a PA system for an area of approximately one square mile. Four Power Amplified Distribution Systems (PADS) enable the ground crew to effectively distribute music and a PA system through 32 speakers, which are stored inside the trailer when not in use. The tripod-supported speakers may be arranged linearly or set up in any configuration suitable for a performance.
All four PADS were designed to fit together on the rearmost section of the trailer, completing its rectangular shape when in transit. Each PAD contains its own generator, fuel tank, and electronics suitable for receiving signals and distributing sound to its designated speakers. The system was designed to allow sound signals to be sent to the PADS in three ways: radio frequency, fiber optic cables, or conventional speaker wires. Using radio frequency, PADS have a two-mile range.
Source Diversified and Abrams worked closely when designing the PADS. "The PADS had to contain so much and still be very compact," says Abrams. "It was a real challenge to get everything to fit and still have the units be relatively small and light." PADS weigh approximately 350 pounds each.
The trailer also encloses four spools containing a total of 1,000 feet of speaker wire and 835 feet of fiber optic cable. Spools have removable handles for rewinding wire and cable using a hand crank.
Power Systems Power is supplied to all of the electronics on the trailer via two seven-kW generators. A 13.6-gallon onboard fuel tank with a gauge allows for eight to nine hours of running time.
"One generator is sufficient to supply power to all of the trailer's systems but another is always online as a backup in case of an emergency," says Abrams.
He designed the two transfer switches that handle primary to secondary switching between generators. In the event that a generator fails, the Air Force does not want pilots to be without ground communications. "The Air Force requires that the switch happen in less than three seconds," says Abrams.
The trailer uses a marine type battery disconnect switch in conjunction with an AC/DC converter-charger for its two onboard gel-cell batteries.
"The trailer was designed with a backup plan for nearly every system," says Abrams. The trailer's variable power sources and various methods of delivering sound prove his point.
The trailer has six radios for ground-to-air communication with the planes as well as communication with air-traffic control. Outfitted with a full soundboard and equalizer, the ground crew can manipulate every aspect of the music it delivers at a show. A mini-disc provides the music and automatically lowers the music volume when the show's commentator speaks. Among the trailer's many electronic components are media panels for output to a television or radio crew.
In total, Nevada Truck & Trailer Repair and Source Diversified took more than one year to complete the trailer.