There's another terrifying scenario. If not fitted properly, one of the tailpipe doors could fly free and knock off the plane's tail, which sits just behind the two engines. If that happened in mid-flight, aviation safety experts say, a crash would be virtually inevitable. Friedman's report on the ABS hush kits also warns of mislabeled parts, incomplete data, miscalibrated equipment, and obsolete parts. Hush kits are installed on airplanes because airplanes make a lot of noise, especially during takeoff and landing.
Federal law requires that engine noise be kept below a certain level.
They are also the only product sold by the company. ABS is the only U.S. company that has received FAA permission to design and sell a Stage 3 hush kit for the DC-9. US Airways, Northwest, and TWA declined comment. Because the company has a monopoly on Stage 3 hush kits for commercial DC-9s, and because the government is requiring all airlines to purchase the kits, they add up to an extremely lucrative business. ABS denies covering up anything.