Hubbard Aviation Technologies has made a major commitment to its Stage III-certified QS3 hush-kit program for the Gulfstream II/II-SP/IIB/III. The program was originally launched by Stage III Technologies, which received an FAA supplemental type certificate (STC) in December 2003 for the modification but went out of business in February 2008. Hubbard Aviation founder Stanley Hubbard owns the first Gulfstream II modified with the QS3 hush kit and bought the assets of Stage III Technologies.

Stage III contracted with 10 vendors to manufacture all the components for the hush kit, but now Hubbard Aviation is working with a single vendor, Aeroshear Aviation Services, a Van Nuys, Calif. manufacturing company and FAA-approved repair station. Hubbard Aviation has contracted for Aeroshear to build components for six hush kits and order materials for an additional six kits. Aeroshear will do the first few installations at its Van Nuys maintenance facility, then Hubbard will authorize other installation centers. The kit is expected to sell for $1.5 million, and installation should take about four weeks and around 1,000 labor hours, mainly because there isn’t room in the back of a Gulfstream for many people to work at the same time.

Installation involves removing systems, shelves and brackets from the Gulfstream’s “hell hole” and adding some structural elements, including a stainless steel I-beam that transfers loads to the fuselage. The three major components in the hush kit are an alternating-lobe exhaust nozzle, fuselage-mounted ejector with noise-absorbing acoustic lining and cascade-style thrust reverser.

QS3-modified Gulfstreams meet Stage III noise limits without any operational restrictions, according to the company, including the ability to depart at maximum takeoff weight with normal flap settings and no reduction in engine pressure ratio. The hush kit doesn’t affect the operation of the engine and doesn’t cause any changes in performance. The cascade-style thrust reverser system is lighter than the original clamshell system and uses only 82 percent power instead of the 94 percent for the clamshell system, thus reducing engine wear.

With used GIIs selling for as little as $500,000, does it make sense to offer a retrofit that will cost more than $2 million? QSC president and COO Bernard Weiss believes that there is a market for the QS3 hush kit. Gulfstream IVs sell for three to four times the price of a GIII, and as the economy recovers from the recession, charter hours have increased and used airplane prices should firm up. As the GIV and GIV-SP near the $10 million mark, a used and hush-kitted GII or GIII, he said, “looks like a more reasonable decision.” Hubbard Aviation also plans to seek an STC from EASA so that European GII and GIII buyers can take advantage of the hush kit.

Hubbard Aviation recently conducted flight tests of a QTA-equipped GII-SP and Hubbard’s QS3-modified GII-SP. While both met the Stage III noise certification standards, according to Hubbard’s testing, the QS3 Gulfstream was quieter than the QTA jet in flyover (by 3.8 dB), lateral (by 4.1 dB) and approach (by 6.1 dB). The last time this testing was done was for the STC issued in 2003.