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Device for stopping SEI (Sustained Engine Imbalance) / windmilling for jet engines (main engines & APU) of airplanes

IP.com Disclosure Number: IPCOM000219003D
Publication Date: 2012-Jun-15
Document File: 7 page(s) / 460K

Publishing Venue

The IP.com Prior Art Database

Abstract

A stop device is provided for stopping Sustained Engine Imbalance (SEI). Within an engine cowling there is disposed a KEVLAR® fan containment chamber. The containment chamber is filled with oil and provided with an oil pump operable to increase the oil pressure. The SEI stop device is disposed within the containment chamber and is deformable such that it increases in size in response to an increase in oil pressure. As the SEI stop device increases in size, it projects radially inwardly so as to reduce the gap between the fan blades and the fan cowling, such that the fan is clamped and prevented from windmilling. Accordingly, engine rotation is stopped. The principle is similar to a peripheral hand brake.

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Title/

Device for stopping SEI (Sustained Engine Imbalance) / windmilling for jet engines (main engines & APU) of airplanes and

Devices for stopping the rotation of an engine

Abstract/

A stop device is provided for stopping Sustained Engine Imbalance (SEI).  Within an engine cowling there is disposed a KEVLAR® fan containment chamber.  The containment chamber is filled with oil and provided with an oil pump operable to increase the oil pressure.  The SEI stop device is disposed within the containment chamber and is deformable such that it increases in size in response to an increase in oil pressure.  As the SEI stop device increases in size, it projects radially inwardly so as to reduce the gap between the fan blades and the fan cowling, such that the fan is clamped and prevented from windmilling.  Accordingly, engine rotation is stopped.  The principle is similar to a peripheral hand brake.

Disclosure/

The following requirements are presently provided for aircraft engines:

§ 25.901(c) of the CS 25 (Certification Specifications for Large Aeroplanes CS-25) requires that no single failure or malfunction or probable combination of failures in the power plant installation will jeopardize the safe operation of the airplane. In addition, § 25.903(c) requires means of stopping the rotation of an engine where continued rotation could jeopardize the safety of the airplane, and § 25.903(d) requires that design precautions be taken to minimize the hazards to the airplane in the event of an engine rotor failure.

The failure of a fan blade and the subsequent damage to other rotating parts of the fan and engine may induce significant structural loads and vibration throughout the airframe that may damage the nacelles, critical equipment, engine mounts, and the primary airframe structure. Also, the effect of flight deck vibration on displays and equipment is of significance to the crew’s ability to make critical decisions regarding the shutdown of a damaged engine and its ability to carry out other operations during the remainder of the flight.

The vibratory loads resulting from the failure of a fan blade have traditionally been regarded as insignificant relative to other portions of the design load spectrum for the airplane. However, the progression to larger fan diameters and fewer blades with larger chords has changed the significance of engine structural failures that result in an imbalanced rotating assembly. This condition is further exacerbated by the fact that fans will continue to windmill in the imbalance condition following engine shut down. Current rules require provisions to stop the windmilling rotor where continued rotation could jeopardize the safety of the airplane. However, large high bypass ratio fans are practically impossible to stop in flight with current technology.

The windmilling condition results after the engine is spooled down but continues to rotate under aerodynamic forces. The windmilling imbalance condition results...