U.S.: FAA order on "older jetliner engines" that lose power

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Headline: FAA to order removal, repair of many older jetliner engines; Concerns arise over loss of power

Source: Wall Street Journal, 12 July 2001

URL: http://www.msnbc.com/news/599309.asp?cp1=1

Federal regulators, concerned that widely used jet engines may lose power during takeoffs, are expected to mandate the removal and refurbishment of certain older engines made by the Pratt & Whitney unit of United Technologies Corp., industry officials said.

The anticipated tighter safety are partly a reaction to the near-crash of an Airbus A300 jetliner in Saudi Arabia four months ago, when both of its Pratt engines lost thrust during or immediately after takeoff.

The move will affect at least hundreds of the roughly 2,000 longer-range Pratt engines in service on Delta Air Lines, UAL Corp.’s United Airlines, Northwest Airlines and dozens of other carriers world-wide. Older engines that haven’t been recently inspected may have to be removed under the tougher requirements.

The Federal Aviation Administration’s action is expected to disrupt maintenance schedules and, according to these officials, could result in the temporary grounding of a limited number of jetliners waiting for replacement parts or engines. Pratt’s PW4000 family of engines will have to undergo rigorous tests and maintenance after fewer than every 3,000 takeoffs, and the FAA is drafting tougher requirements for later this year

The directive, expected in the next few days, also indicates that despite years of stepped-up inspection, maintenance and engine-replacement initiatives, regulators have concluded that additional safeguards are necessary to resolve one of the most nagging and potentially most hazardous engine-safety problems confronting the industry.

“Are the fixes that have already been identified really working? Obviously, they are probably not,” said Ken Hylander, Northwest’s vice president for quality, reliability and engineering. Northwest has the engines on 14 of its 747 aircraft but doesn’t expect schedule disruptions.

A Pratt spokesman said the backfires and loss of thrust are “certainly” an issue, but “we have reduced the incidence” of such problems and are working to “minimize any risk ... and disruption to our customers.” Permanent fixes are slated for installation by 2003.

An FAA spokesman said the agency is “reviewing data received from Pratt & Whitney and is considering appropriate airworthiness action.” The new rules will cover Pratt engines powering Boeing Co.’s 747, 767 and MD-11 aircraft, as well as A300 and A310 models manufactured by Airbus Industrie.

The FAA became concerned after a twin-engine Air Sudan A300-600, leaving Jedda, Saudi Arabia, in March, experienced compressor surges on both engines during takeoff. Following emergency procedures, the cockpit crew throttled back both engines to idle. An official report of the incident indicates that for about 50 seconds the engines didn’t produce any thrust, and the jet came within 67 feet of crashing into the Red Sea before the pilot was able to regain power. Pratt said it has documented an earlier incident involving simultaneous loss of thrust on two engines.

The FAA wants to ensure that at least one engine on each aircraft has passed the most rigorous maintenance tests. It will be the second time this month that the agency has mandated immediate action on Pratt engines. Several airlines were forced to ground a handful of their Boeing 757s while they scrambled to find replacement parts for another family of Pratt engines.

A spokesman for United said the company might have to move some engines from plane to plane or put some into the shop. A spokesman for Delta, Atlanta, said the airline would have no comment on the FAA’s order until it is issued.

-- Andre Weltman (aweltman@state.pa.us), July 12, 2001

Answers

To prevent compressor surge these engines are equipped with variable inlet guide vanes and variable stator vanes in the first stages. Also the engine manufacturer will bleed air from the compressor to prevent surge. The compressor vanes are basically an airfoil which can stall so it is important to have the proper pitch for varying compressor loads. The bleed and variable vanes are controlled by the engine fuel control (or computer) which is located on the side of the engine.

-- David Williams (DAVIDWILL@prodigy.net), July 13, 2001.

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