Making jet aircraft acceptably quiet can be a dirty job. Owners don’t want to spend the money, engine makers don’t want to compromise their products’ efficiencies and airport neighbors are rarely happy with the results.

Maintenance and modification shops, however, don’t mind the trouble. Business Jet Technology got into the hush-kit business by investing in a program three years ago with Quiet Technology Aerospace (QTA) to develop and certify a silencing system for the Spey-powered Gulfstream II and III. Founded in 1984, Quiet Technology lays claim to being the world’s oldest hush-kit designer and manufacturer. It holds eight separate STCs for large commercial and military transports and corporate jets.

“We came to the market at the worst possible time,” admitted Business Jet partner Kevin Jordan. “When we started developing the hush kit [in 2000], a decent GII was selling for about $6.5 million and a GIII for $12- to $14 million. Now they’re half that, and most owners are reluctant to invest in the hush kit unless they can see an increase in the value of the airplane, and we do not have enough market experience yet to see to what degree that will be the case.”

Martin Gardner, QTA director of engineering and certification, adapted his credo from the company’s advertising campaign: “We don’t sell hush kits. We sell the freedom to fly anywhere, anytime.” And that is essentially what quiet aircraft are about. He cited the experiences of one GIII customer who lived during the week in Atlanta and flew to his second home in Naples, Fla., on weekends. Since his aircraft couldn’t qualify for landing privileges at Naples, he had to regularly divert to the Fort Myers Airport and drive.

Gardner explained that the Gulfstream hush kit is similar to QTA’s Stage 3 application for Rolls-Royce Spey engines developed for the BAC 1-11. It has been engineered to be lightweight and structurally simple.

“A translating ejector forces exhaust gases through a special nozzle and into an ejector shroud,” he said, “thereby decreasing exhaust velocity and noise. And the system retains the original Gulfstream thrust reverser.” The hush kit is purely mechanical. It has few parts, needs no structural reinforcement, forgoes any additional actuation controls and there are no systems changes. It’s a strictly bolt-on proposition with the exception of trimming a little sheet metal on the engine pylon, and it can be finished in 10 days.

The weight of the entire kit is just 234 pounds–the equivalent of 35 gallons of jet-A–and the c.g. envelope is unchanged. While a slight degradation in performance was expected, so far QTA is hard-pressed to see any significant numbers. “Some of our early customers who use their GII mostly on long flights reported no change from a standard airplane,” Gardner said. “Another customer who flies short legs thinks maybe they’ve lost 1 to 1.5 percent.” Certification was granted January 27, and by September this year 10 kits had been installed.

“Sales have been disappointing this year,” Jordan said. However, he has a merchandiser’s mindset worthy of Penney, Woolworth or Walton and the other noted retailers of history–a hook to get prospects to commit to the modification they must have to get into an increasing number of the world’s airports.

“Order a QTA Stage 3 hush kit for your Gulfstream II or III at its regular price of $1.35 million and schedule a time for installation, and Business Jet Technologies [an affiliate of Business Jet Center in Dallas] will give you our $175,000 RVSM modification free,” he said. Since it’s necessary for the customer airplane to be down for three weeks for this combo offer, the company will even make arrangements for a loaner airplane during that time.

Business Jet Technologies has teamed with Shadin and AeroMech to produce an RVSM solution that is plug and play and uses existing wiring for direct replacement of any ADC installation.

Having a “two-fer” STC sale is a little unusual, but the day it was announced two GIII hush kits were sold to one operator and another order came from Mexico the next day.