While three companies are competing to market FAR Part 36 Stage 3 hush kits for the Gulfstream II, IIB and III, two–Really Quiet and Stage III Technologies–have been developing their respective systems much longer than either originally planned. Really Quiet could very well be the first to receive FAA certification, which is expected this month. The company had expected to receive certification just before the NBAA Convention and was hoping to make a big announcement there. Not only was the convention canceled in the aftermath of the September 11 terrorist attacks in New York City and Washington, but the STC project was put on hold when the FAA went on high-security alert in the wake of the attacks.

Regarding aircraft performance penalty, Really Quiet director of sales Dave Hewitt said, “We have a slight performance penalty [described as an up to 5-percent loss in range] that we will rectify with a product improvement mod after certification.” In late August Hewitt said the company was doing “fine tuning” and load checks of the ejector and the thrust reverser. The results and other paperwork were to be given to the FAA by the end of August for the final steps in the certification process.

Hewitt said there are “close to” 50 orders for the hush kit. The first half-dozen installations will be done by Really Quiet at its facilities at Mojave Airport in California. “That’s just to satisfy FAA requirements to ensure that tooling is correct and other details,” explained Hewitt.

After the initial installations, customers will be able to choose their own installation facility, as long as it meets the approval of Really Quiet. The company is expected to appoint several well known service facilities as approved hush-kit installation centers. Once the installation process gets up to speed, Hewitt estimates three to four weeks of installation downtime. The installed price remains $1.8 million, which includes re-painting, Hewitt emphasized.

The kit provides a “cumulative noise level six to seven decibels below Stage 3,” according to Hewitt, who also claims that the sound reduction is evident enough that the difference between the hush-kitted Gulfstream vs a non-kitted Gulfstream can clearly be heard, both in the sky and on the ground.

Meanwhile, Stage III Technologies of Van Nuys, Calif., has again had to push back its certification schedule because of serious vendor delays and manufacturing problems in providing necessary parts. “We have had trouble fabricating the ejector,” said chairman Todd Stimmel. “We expected to finish the ejector sets and flight test them late last month. Our fabricator ran into some problems, then they went on strike. It was just a disaster.”

Tyler Jet has provided Stage III Technologies with a GII dedicated to the hush-kit development, said Stimmel, replacing an aircraft provided by Hubbard Broadcasting earlier in the development program. “If we pass the acoustic test with the FAA, we are done,” declared Stimmel. Done, except for the hush kit. Although completely designed, it too has suffered delays. “It wasn’t made to spec the first time, that’s why it won’t be ready when the hush kit is certified,” Stimmel said.

“Our thinking is that we will try to sell the hush kit without a thrust reverser. We will package it with a reverser when we get [the certification] done. We recognize that there’s going to be just a limited number of GII/GIII operators that are going to buy the kit without reversers,” conceded Stimmel. “But I also think there will be a market for some people who do want to buy it without reversers.”

The reverser has already been fully designed, claimed Stimmel. But because of the tooling lead times required, building a reverser is going to take several months. To save some time, “we don’t plan on making a prototype of the reverser,” explained Stimmel. “We’re just going to go into production with them. We are convinced they will work.”

Stage III Technologies plans a cascade-type reverser to replace the clamshell type now on the GII/GIII. Stimmel said his company’s design is “basically the same technology that’s on the NASA Gulfstream. It’s really the state-of-the-art [titanium] and it’s not going to add any weight.”

The company hasn’t yet decided on how to handle pricing. “We are going to sit down as soon as we pass the acoustic test and decide what we want to do,” he said. “My initial belief is that we’re likely to sell the hush kit without the reverser for $1.5 million and $300,000 to get the reversers installed when we have them in six to eight months.” Dallas Airmotive has marketing responsibilities for the hush kit and will provide installation technical data to appointed facilities. Downtime will be about three weeks.

Another company joined the Gulfstream hush-kit race in May. Although Quiet Technology Gulfstream (QTG) of Opa Locka, Fla., joined the fray late, its hush kit for the GII/III is based on the system it certified last year for the Spey-powered BAC 1-11. QTG’s system consists of a translating ejector (optimized for Mach 0.80 cruise) installed on “bolt on” sliding rails that requires no changes to the airplane’s existing thrust reverser.

According to director of engineering and certification Martin Gardner, “We have completed the design and all the manufacturing drawings and we are now in the process of selecting a vendor for producing the parts.” A backer of the program has lent its GII (which incorporates a Service Bulletin that increases the gross weight to that of a GIII) to QTG as the dedicated test airplane. Data acquisition systems are currently being installed in the airplane. The company expects to start the baseline part of certification flight testing this month.

Gardner said the company has a goal of achieving Stage 3 limits in the GII/III without tradeoffs in any of the three measuring parameters (approach, sideline and takeoff), but he noted that a tradeoff was necessary on the larger and heavier BAC 1-11. He said Stage 3 will definitely be achieved, with or without any tradeoffs.

One thing QTG is doing differently from either Really Quiet or Stage III Technologies is that “we are putting some acoustic attenuation into the engine inlet nose cowl,” Gardner said. “That gives us a benefit in all three noise measurement points.” This also provides QTG with some “trade margin,” if required. Another change being incorporated by QTG is to the existing mixer nozzle. The original five-lobe mixer nozzle on the GII/III will be replaced by a 12-lobe mixer for increased efficiency.
Total installed weight of the QTG hush kit is approximately 110 lb per side. Gardner predicts a 2- to 3-percent range penalty.

At $1.35 million installed (for orders received prior to obtaining the STC), the kit is priced $450,000 less than the systems being developed by Really Quiet and Stage III Technologies. QTG claims it has orders for 17 of its hush kit sets “without any real sales or marketing effort.” QTG expects to complete certification flight testing in the first quarter of next year and obtain certification in the second quarter. The company originally set certification for the first quarter.