HOLLOMAN AIR FORCE BASE, N.M.-- The 846th Test Squadron, a unit of Arnold Engineering Development Complex, has deployed a new design for the birdchaser sleds used at the Holloman High Speed Test Track, or HHSTT, on Holloman Air Force Base, New Mexico.
The birdchaser sleds, used to mitigate bird and animal strikes during HHSTT test missions, are one of the two main methods of mitigating animal strikes. Orchard cannons and small birdchaser sleds are fired in the range of 10 to 40 seconds before the mission sleds.
“For all missions with portions over Mach 1, we will use one, or often both, of these methods,” said Laura Ahrens, a mechanical engineer with the 846 TS.
Ahrens added that birdchaser sleds are more effective and are the preferred method when possible.
“They are especially used for sensitive payloads where an animal strike could cause a mission failure,” she said.
The new design for the birdchaser sleds have replaceable parts, making it a more convenient and cost beneficial option as well.
“Previously, the sleds consisted of a bent, wrap-around style slipper that was welded to the rest of the sled structure,” Ahrens said. “This slipper design meant that the sled had to be loaded at one end of the rail and then towed into place using a truck.
“The new design has two main feature improvements: replaceable slipper inserts and split slippers.”
The slipper inserts are flat pieces of metal that are bolted to the inside of the slippers, which ride along the rail. Split slippers are slippers that can be split apart so that they can be installed on the rail at any location, not just the end.
“After several sled tests, the friction on the rail will cause wear to the material of the slipper where it contacts,” Ahrens said. “The new design confines the wear to easily manufactured and replaceable slipper insert components, as opposed to more complicated components that cannot be replaced.”
With the original design, when too much wear had occurred, the sled would be retired and a new one built.
The new sled was designed with limited different components that are used in several different locations on the sled. For example, the slipper base and bolt-on slipper sides are the same in the front and back of the sled. This has reduced machining set-up time, resulting in less manufacturing cost.
According to Ahrens, the sled was also designed to have a bolt-on front end, which can be changed from a flat plate to a cone to change aerodynamic drag characteristics of the sled and tailor the birdchaser run distance for the mission.
“This allows a single sled to be configured and used for a variety of missions, rather than requiring multiple styles of birdchaser sleds to be built,” she said.
Other improvements include that the sled is compatible with three different motor types and the aft of the slipper uses a pass-through type motor mount instead of a bolted clamp, which was part of the previous design.
“Being able to load the sled anywhere on the rail saves time and cost in test setup, and also is a safer operation than towing the munitions,” Ahrens said.