Planenews Aviation News Portal - Engine may get first flight at base

Air Force researchers hope to make the first flights of an airplane powered by a revolutionary jet engine here, they said Tuesday after demonstrating the airplane on a runway behind the Air Force Museum.

Wright-Patterson became a candidate flight center after disappointing power tests in California prompted the research team to bring the airplane back here — where the engine was developed — for debugging.

Now that it''''s here, the researchers are conducting "acoustic surveys" to find out if the so-called Pulsed Detonation Engine can be flown over the Wright-Patterson airfield without breaking federal noise rules, said Fred Schauer, the Air Force Research Laboratory engineer who led the development effort.

The Air Force-contractor team working on the PDE program demonstrated the novel technology for a crowd of engineers who are in town for a jet-engine symposium sponsored by AFRL.

The engine put out a loud buzz that sounded like cloth being ripped as it pushed a sleek, white airplane a short distance down the runway. Test pilot Michael Melville cut the engine after a few seconds, but the sound continued to echo from surrounding buildings — soon joined by the engineers'''' applause.

"It''''s a very sharp, loud noise" inside the cockpit, said Melville, who gained fame in June for piloting the privately financed SpaceShipOne rocket into space.

Schauer said the sound can carry as far as 8 miles directly behind the engine''''s four exhaust pipes.

Up close, the PDE is an ungainly mass of tubes, wires and belts stuffed into the sleek, white frame of a Long-EZ, a fiberglass airplane designed for amateur aircraft builders. The engine protrudes from the belly of the frame.

The PDE has little in common with conventional jet engines.

A collection of off-the-shelf parts, it uses a Pontiac Quad-4 engine head to valve fuel and air into the pipes, where ordinary spark plugs ignite the mixture.

But once that happens, "We do a few tricks" to turn the ordinary combustion into a high-pressure detonation, Schauer said.

The result is an extremely energetic exhaust thrust. The ripping sound comes from the fact that each pipe is detonating 20 times per second — 80 times per second in all.

Schauer''''s development team tested the first PDE engines at the Propulsion Directorate on base. A local aerospace company, ISSI, built three demonstration engines. Mojave, Calif.-based Scaled Composites LLC — the same company that designed and built SpaceShipOne — integrated the engine into the airplane, which it owns.

Schauer said two engines tested at Wright-Patterson put out 150 pounds of thrust, but this one only produced about 100 pounds in six months of taxi tests at Mojave.

"We brought it back to Dayton to find out why," he said.

This PDE is big, heavy and inefficient, Schauer said, but an "optimized" engine — one not made of car parts — could be very small and simple, yet able to propel aircraft or missiles to speeds of more than four time the speed of sound.

Schauer said local flights are yet to be approved and he declined to say when they might take place.