SAE AIR 4096-1989 Helicopter Engine Foreign Object Damage.pdf
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1、SAE AIR*40b A7 m 8357340 0047229 A m K33-o9 AEROSPACE INFORMATION TheEngilk?e7-ngsociety Ih =For Advancing hfobiliiy -Laand Sea Air and Space INTERNATIONAL 400 Commonwealth Drive, Warrendale, PA 15096-0001 R E PORT Submitted for recognition as an American National Standard s, foliage (grasses, leave
2、s, During operation in icing conditions, ice that accumulates on the airframe can shed if aerodynamic and/or vibratory forces overcome the adhesive strength between the ice and the airframe structures. ice may then fall away from the aircraft or, on occasion, impact and damage the aircraft or be ing
3、ested and damage the engine. A slab or chunk of SAE AIRm4096 89 m 8357340 OULI9233 b m Page 3 .set, AIR4096 5.1 (Continued) : During flight operations outside of landing zones, the helicopter engine is subject to the same sources of FOD as fixed-wing power plants. These sources include birds, rain,
4、hai 1, snow, and ice. 5.2 Installati-onc: The engine inlet duct system and areas in front of and over the airframe inlet can be a potential source of FOD. The resulting damage from such items may be referred to as “Bi11 of Materials Object Damage.“ Mechanical fasteners within the inlet duct flowpath
5、 or on doors and access panels in front of or over the inlet can work themselves loose as a result of vibratory forces or improper installation and migrate into the engine, In the case of inlet ducts made of composite materials, pieces of the duct itself may delaminate and be drawn into the engine.
6、Low areas within the inlet duct flow path can trap water which, when subjected to freezing conditions, will convert to the solid phase. Upon engine start-up or under warming conditions, chunks of ice may become dislodged and be ingested. 5.3 Maintenance: Aircraft mechanics and other service personne
7、l, while performing their normal duties, may inadvertently leave hand tools such as screwdrivers, wrenches, sockets, inspection mirrors, etc. in the inlet ducting. Fastening hardware (nuts, bolts, cotter pins, safety wire, etc.) removed during service may accidently be left in the inlet or engine or
8、 may fall into areas that are not easily visible only to be later discovered lodged between rows of damaged compressor rotor blades and stator vanes. Parts bags, tags, rags, maintenance instruction sheets, plastic and metal caps and plugs are all examples of debris that have been left behind followi
9、ng service action only to become potential sources of foreign object damage to varying degrees. People working around aircraft invariably have pockets containing loose personal items (pens, pencils, pocket reference books, six inch scales, notebooks, magnets, flashlights, inirrors, etc.) that can un
10、knowingly fall out and into the inlet duct or engine, Rings, bracelets, necklaces, earrings, watches, and other types of personal jewelry and accessories can all cause extensive damage if allowed to enter the engine. Ground debris can be picked up by footwear and be deposited in the inlet system. 6.
11、 EFFECT OF FOD ON OPERATIONS: The most common effect of foreign object ingestion is damage to the compressor section of the gas turbine engine. The effects may be so minor that the operator cannot detect any change in the engines operating characteristics or be so extreme that the engine becomes ino
12、perable. Therefore, there are forms of FOD that may be considered to be “tolerable“ and those that are entirely “intolerable.“ SAE AIR*4Ob 87 W 8357340 004Z32 8 W 6AE AIR4096 -I Page 4 6.1 6.2 -I.-_.-. Tolerable FOD: _- Tolerable FOD can, in a general sense, be classified as damage which does not de
13、grade engine performance beyond the operating limits established by the engine manufacturer. compressor blade tips or actual loss of small pieces of the blade (tip leading edge) or minor local damage can be tolerated, but may reduce the life of the engine. reduced, ultimately yielding an engine that
14、 runs hotter to produce the same output power as before the ingestion of foreign objects. or overhaul manuals define the extent of damage that is acceptable and actions that can be taken to recover some of the lost performance and to reduce the potential for further damage due to crack propagation f
15、rom FOD i iiduced stress concentrations. The comparatively minor bending of The compressor pumping capacity and efficiency may be Engine maintenance Although the ingestion of “soft“ foreign objects such as paper, plastic bags, leaves, grasses, etc. does not generally cause physical damage to the com
16、pressor, these items can become lodged in front of inlet guide vanes and support struts creating airflow blockages and distorted airflow profiles. Inlet blockage causes an inlet pressure loss and reduces engine output power. The distorted airflow caused by the blockage can, in the extreme, drive the
17、 compressor into surge which, depending upon the condition of the engine and severity of the surge, may cause physical damage to the engine. In all but those cases where the hardware is deformed, engine performance should be recoverable by removing the foreign objects causing the blockage. The term
18、“tolerable“ as used in this section relates to the effect of the ingestion of foreign objects on engine performance. In economic terms, the effects of FOD may not be acceptable when consideration is given to the costs associated with the resulting increased fuel usage, reduced engine life, unschedul
19、ed tnaintenance and repairs, etc. &to.erabl.e FOD (Enqine Failure: Thi s refers to an engine shutdown resulting from physical damage to a mechanical or structural part or component of the engine. before the engine can be used again. the engine to be unable to perform within specification or service
20、manual limits or to be unable to sustain stable operation is essentially an FOD induced fai 1 ure. Mechani cal Pai 1 ures of the engine are defini tely within this classification which has here been expanded to include either blockage or damage short of complete failure that causes the engine to ope
21、rate in an unstable manner or at a speed, temperature, or torque limit while producing unacceptable output power. The damaged hardware must be replaced or repaired Foreign object ingestion that causes 7. FOD PREVENTION TECHNIQIJIS: The reduction and prevention of gas turbine engine damage due to the
22、 ingestion of foreign objects is the responsibility of the engine and airframe designers, the operators and the maintenance personnel . SAE AIR*409b 89 M 357340 0049233 T M AIR4096 I 7.1 7.2 - Engine/Airframe Desiun: must confront FOD as one of many factors affecting the engine design. order to be t
23、olerant of foreign objects, the number of parts projecting into the airflow path should be minimized (e,g., inlet temperature and pressure probes, mechanical fasteners, etc. 1. The use of capti ve bolts, retained nuts and washers, self-locking fasteners (versus lockwire) and other devices which limi
24、t the number of free small parts will enhance an FOD resistant design philosophy. The engine designer may wish to consider use of wide chord compressor blades having comparatively blunt leading edges that can more readily survive the abuse of impacting foreign objects. Similarly, variable inlet guid
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