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San Diego
Tuesday, May 28, 2024

New Exhaust Nozzle May Be Ticket For Quieter Landings

Parthiv Shah is on a mission that would gladden the hearts of Point Loma, North Park and Carlsbad residents — not to mention people all over the world who live under airport flight paths.

With funding from NASA, Shah and his co-workers at North County-based ATA Engineering Inc. have developed a way to make common aircraft jet engines quieter.

His engine air brake is a jet engine exhaust nozzle that changes shape, and changes the thrust of the jet. ATA calls it “drag on demand” technology.

During an aircraft’s descent, the invention could minimize aircraft noise in several ways.

It could allow the aircraft to fly more slowly. It could create an alternative form of drag (something different from air going around extended landing gear, which creates a whistle). And it could give an aircraft a way to approach the runway at a steeper angle.

NASA has spent between $1.5 million and $2 million on the invention through Small Business Innovation Research grants, also known as SBIRs, according to Joshua Davis, ATA’s director for new technology development.

The project has come to a point where it needs more funding.

Ground Tests

After 10 years, the invention has yet to be tested in flight, though it did go through a series of ground tests in October.

“In aerospace, things don’t go that fast,” Shah said.

Davis said the first flight could come before the decade is over.

The engineers demonstrated the brake at a Michigan facility, attaching it to a small jet engine used on business aircraft. The Williams International FJ44-4A turbofan engine — which measures about 2 feet in diameter — powers the Cessna Aircraft Co. CJ4 aircraft and the Pilatus Aircraft Ltd. PC-24.

Once the invention is optimized, the engineers see the mechanism going on all sizes of jet engines — even the 6-foot-6 behemoths that power the C-17 military transport aircraft.

A Saw Tooth Shape

The new nozzle might be compared with a giant wedding band with 12 openings, each plugged by a doorlike vane. Informally, the engineers call the ring with the 12 spiked pivot mechanisms the “crown of thorns.”

At the pilot’s command, the 12 vanes open on their hinges, changing the shape of the jet blast, giving the blast a swirling motion and creating drag.

When the 12 vanes are stowed away, the engine operates normally.

The project is an outgrowth of Shah’s doctoral studies at the Massachusetts Institute of Technology’s Gas Turbine Lab. Shah received his doctorate in mechanical engineering and fluid mechanics.

ATA basically got the project when it hired Shah in 2007.

There is one patent on the nozzle and a second patent is pending.

Today, the prototype brake sits in a shipping crate, which Davis and Shah opened to show a visitor. Thanks to springs and jet engine physics, the nozzle can recover its perfect round shape in a fraction of a second. Shah demonstrated the mechanism on the prototype. The aluminum gave off a loud slam.

Easy Recovery

Though the invention decreases the thrust of a jet, the turbine speed doesn’t change, allowing the engine to easily return to full blast if the pilot makes a split-second decision to call off a landing. Federal authorities wanted the mechanism to stow itself in less than a half-second. “We did three-tenths of a second,” Shah said.

Deployment takes longer — several seconds — as the invention has to work against the force of the jet engine.

There is plenty of work ahead on the project. Now the engineers have to make the device more durable and reliable.

The engineers investigated the best shapes for the nozzle components using standard aluminum, with no regard for weight. Weight, of course, is a huge concern for aircraft suppliers, so the engineers plan to investigate how they might make the components lighter. Composite materials, 3-D printing and hollow components might all help in those efforts, Shah said.


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