1、O AIRCRAFT FIRE PROTECTION FOR HELICOPTER GAS TURBINE POWERPLANT AND RELATED SYSTEMS INSTALLATIONS AEROSPACE AIR 1262 Society of Automotive Engineers, Inc. R EP O RT Issued WACE INFORMATION October 1974 (See Preface) Revised 400 COMMONWEALTH DRIVE WARRENOALE. PA 15096 TABLE OF CONTENTS Page PREFACE
2、. 1 PURPOSE . 1 SCOPE 2 INTRODUCTION 2 1. FIRE PROTECTION FOR HELICOPTER GAS TURBINE POWER- PLANT AND RELATED SYSTEMS INSTALLATIONS . 4 1.1 General Discussion and Terms 4 1.2 Prevention of Occurrence of Fire 6 1.3 Prevention of Spread of Fire 15 1.4 Fire Deteqtion . 18 1.5 Fixed Fire Extinguishing S
3、ystems . 21 1.6 Summary . 31 1.7 References 31 PREFACE This document was issued in 1963 by the Powerplant Installation Committee of the Aerospace Industries Association (A. I. A. ) as a design manual for all types of aircraft: “Aircraft Fire Protection for Recip- rocating and Gas Turbine Installatio
4、ns. Aerospace Industries Association. If (Aug. 1, 1949. Revised 1963). Since then the originating Committee was dissolved and the manual became unavailable. In this period, advancements in aircraft fire protection methods have been produced by both governmental and private agencies that are not refl
5、ected in the original manual. Recognizing this, the SAE S-12 Helicop- ter Powerplant Committee has prepared this revision as an AIR (Aerospace Information Report) to bring it up to date and to emphasize helicopter turbine powerplant fire protection, excluding previously in- cluded airframe-related i
6、tems such as brakes, wheels, baggage compartments, cabins, etc. PURPOSE This design manual contains fire-prevention information accumulated on civil and military aircraft. It is presented as a service to all organizations, government agencies, and individuals interested in avia- tion as well as to t
7、he helicopter designer, to whom the information is specifically directed. This ma- terial has been presented in concise indexed form to serve as generalized reference material and to provide background data for the designer. It is not intended that this besconsidered as proposed regula- tory or spec
8、ification material because it borders on maximum rather than minimum required airworthi- ness. Copyrioht 1974 by Society of Automotive Engineers, Inc. Ail rights reserved. Piinteclin U.S.A. . SAEAIR*12b2 74 83573qO 0003757 7 -2- 1 l The AU Manual was first published 1 August 1949. It was previously
9、revised on 15 April 1954 and 1 December 1957 and, in that time, has been used widely as a guide by many government and civil organizations of both do- mestic and foreign countries in the manufacturing, operating, and educational fields of aircraft. This revision incorporates the experience of indivi
10、duals from many helicopter airframe, and engine companies, and from several government agencies. The following government publications were used as a guide to fire protection requirements in preparation of this manual: A. Air Force Systems Command Design Handbook 2-3, PrOpulsion and Power (Ref. 1).
11、B. U. S. Navy Specification SD-24K, “General Specification for Design and Construction of Aircraft Weapon Systems“, Vol. II, Rotary Wing Aircraft (Ref. 2). C. Federal Air Regulations - Part 29 - Airworthiness Standards: Transport Category Rotorcraft (Ref. 3). D. MIL-HDBK-221 (WP) IIMilitary Standard
12、ization Handbook-Fire Protection Design Hand- book for U. S. Navy Aircraft Powered by Turbine Engines“ (Ref. 4). SCOPE This document is reissued for application to helicopters. It is primarily intended to apply to the engine or en- gines, but it shall also apply to fire protection of lines, tanks, c
13、ombustion heaters, and auxiliary powerplants (APU). Post-crash fire protectionis also discussed. INTRODUCTION The work done in the initial stages of design will determine the final degree of fire protection inherent in a new helicopter; therefore, considerable foresight as to the eventual installati
14、on details is necessary. A lack of per- ception as to the relationship between a source of ignition and combustible fluids or materials may resur in a combination which no amount of subsequent detailed design struggling can ever completely remedy. The inevit- able design conflicts which arise on any
15、 new helicopter, and the resultant compromises, should always consider the fire potential in order to obtain a sensible balance. For this reason, emphasis to keep the thought of fire protection prominent in preliminary design work is well worth the effort. The following design points are in- tended
16、to give a number of general rules for the fire protection features of preliminary design. If fire protec- tion is considered in the preliminary design, the work of the detail designer trying to protect any particular section of the helicopter from the hazards of fire can be greatly simplified. Each
17、helicopter is an individual problem and it is realized that many factors will affect the decisions in its design. However, the nearer the design can be to basic safety principles, the less will be the chance of trouble caused by detail design errors, maintenance in the field, or failures of equipmen
18、t. It is strongly felt that the basic safety responsibility for a helicopter lies on the drawing board. Each engineer concerned with the design of a system or component should realize its potential relation to all other affiliated and adjacent items and to the helicopter as a whole. Because the most
19、 important phase of fire protection is the prevention of occurrence of fire, each engineer responsible for the design of a component of a helicopter can contribute most satisfac- torily to the basic safety of the helicopter if he has a thorough knowledge of the aircraft fire protection problem. Ther
20、efore, this AJR is built around a general discussion of fire protection, Mention of specific systems is made only where the general discussion does not apply, or where exceptions to the general discussion must be pointed out. Regardless of the original fire protection design features built into the
21、helicopter, it is necessary to maintain the helicopter properly to avoid increasing fire hazards; various means and procedures for accomplishing this can also be found in this AIR SAE AIR*L262 74 m 83573LO 0003958 O -3- For purposes of discussion, fire protection consists of four basic divisions: Pr
22、evention of Occurrence of Fire Prevention of Spread of Fire Fire Detection Fixed Fire Extinguishing Systems . . I. -. SAE AIR*1262 i4 W 83573qO 0003757 2 -4- 1. FIRE PROTECTION FOR HELICOPTER GAS TURBINE POWERPLANT AND RELATED SYSTEMS INSTALLATIONS 1.1 General Discussion and Terms: In the concept of
23、 the gas turbine helicopter there are several fundamentals peculiar to its operational characteristics that should be set forth. It is emphasized that the concepts in this discussion have stemmed from experience on specific airplane-engine combinations in service and should therefore be carefully we
24、ighed in application to newer units. Operations show, however, definite trends as explained below such that the designer should be aware of their existence. 1.11 1.111 1.112 1.113 Typical Engine Hazards: To facilitate interpretation of the subsequent comments of this report, it is considered advisab
25、le to describe here the general failures and hazards considered basic to gas turbine engines. Turbine: Experience to date has shown two distinct types of turbine failure to exist. One is thermody- namic in basic cause andthe other mechanical. A. Thermodynamic: The gas turbine operates only because o
26、f a large proportion of excess air (above that used for combustion) which dilutes and cools combustion temperatures to values which the turbine materials can tolerate. It is seen, therefore, that any cause factor which richens this ultimately very lean cycle will overheat the turbine. The type of fa
27、ilure resulting from turbine overheat depends upon the magnitude of the temperature rise and the rate of temperature rise. In case of a relatively moderate overtemperature, the blades will begin to melt at the tips and rapidly burn down toward the base, the molten metal being carried away by the exh
28、aust gas. The shortening of the blades results in a rapid loss of thrust and a rapid increase in the quantity and length of the flame. If the temperature rise is sudden and severe, as it would be in case of rapid ice accumulation on inlet screens and inlet guide vanes, for example, the blades may be
29、 severed by the flame, resulting in the outer 2/3 to 3/4 of all blades (red hot) being thrown outward tangential to the turbine and in an area lying within a few degrees of the plane of the turbine wheel. This type of failure may result in complete or partial severance of the tailcone and possible p
30、enetration of helicopter structure, tanks, controls or equipment located near the plane of the wheel. Careful thought should be given to the specific cause factors possible on a given helicopter. Ice, controls which permit either compressor stall or excess fuel, or excess air bleed or leakage can ca
31、use this type of failure. B. Mechanical: Occasionally, one or two blades of a single stage turbine will fracture and/or be Itthroivn“. Normally, these do not penetrate parallel to the turbine plane but are restrained by the housing and penetrate at angles aft of this, if at all. Tail pipe puncture i
32、s usually the worst that happens which creates an emergency overheat condition. The engine usually becomes noticeably rough but operational under reduced power. Failures of forward stages of multi-stage turbines would probably be much more severe and cause fairly violent mech- anical damage if not c
33、omplete strippage of all stages, due to pieces of blade causing inter- ference between stator and rotor blades. In case of such extensive damage, the structural integrity of the turbine housing may become questionable. It is noted that mechanical failures of the wheel itself rarely occur. Compressor
34、: Compressor case penetration by failed blades is very unlikely in high compression ratio engines due to the inherently strong case design. In installations with low compression ratios, however, case penetration should be considered as a possible fire cause factor, and lines and components con- tain
35、ing flammable fluids should be located so as to minimize the hazard of damage by penetrating parts. Tailpipe: On some engines, a high flow of fuel through a maladjusted fuel nozzle will cause burn-through of the tailpipe at a spot downstream of the fuel nozzle. SAE AIR*L262 7V 83573VO 0003960 7 1.11
36、4 1.115 1.12 1.121 1.122 1.123 1.124 1.125 1.126 1.127 1.13 1.131 1.132 1.133 -5- Engine Fires: Burning fluid will occasionally run out through the exhaust pipe. Positive provisions should be made either to let the fluid run free and clear of the airplane to the ground or to trap and drain it overbo
37、ard. Operating procedures, proper fluid drainage and prevention of static oil leakage are best ways to prevent or minimize such fires. Burner-Can Burn-Through: Under certain circumstances, internal engine damage can lead to burner- can burn-through. Because of the inability of standard firewall mate
38、rials to withstand the flame for more than a short time, consideration should be given to other means to protect against such burn- through. Terms and Definitions: Terms which must be defined to clarify their usage herein are the following: Fireproof: A material which will withstand heat as well as
39、or better than steel which will withstand 2000“ F (1093“ C) for 15 minutes and still fulfill its design purpose. When applied to materials and parts used to confine fires within designated fire zones, IlfireprooPl means that the material or part will per- form this function under the most severe con
40、ditions and duration of fire likely to occur in such zones. Example: Transverse engine fire wall, which resists 2000“ F (1093C) flame for 15 minutes. (See Note of 1.122) Fire Resistant: When applied to sheet or structural members, “fire resistant“ describes a material which will withstand heat as we
41、ll as or better than aluminum alloy in dimensions appropriate for the purpose for which it is used. When applied to fluid-carrying lines, other flammable fluid system com- ponents, wiring, air ducts, fittings and power plant controls, this term refers to a line and fitting as- sembly, component, wir
42、ing, duct or controls which will perform the intended functions under the heat and other conditions likely to occur at the particular location. An example: Fire resistant hose which will resist 2000“ F (1093“ C) flame for 5 minutes (See Note). Note: A test procedure to determine the minimum safe lim
43、its is presented in Reference 5. Flame Resistant: Materials which will not support combustion to the point of propagating a flame be- yond safe limits after removal of the ignition source. Flash Resistant: Materials which will not burn violently when ignited. Flammable: Solids, liquids, or gases whi
44、ch will ignite readily or explode. A percent nonflammable method applicable to fluids (aviation gasoline, kerosene, standard hydraulic fluid, lubricating oils, etc. ) that are miscible with hexachlorobutadiene is presented in Reference 6. Compartmentation: The process of isolating components or area
45、s from each other or from other items or environments with which they would be hazardous in combination. Ventilation Stop: An isolating bulkhead which is substantially vapor and liquid tight, for the purpose of controlling ventilation and liquid paths. Where this barrier has also the purpose of prev
46、enting rapid travel of a fire over wide areas of the helicopter, the ventilation stop should be at least fire resistant. Zones and Zone Classification: Combustible Zone: A helicopter compartment containing equipment from which leakage of combustible fluids or vapors is not abnormal. Example: Fuel ce
47、ll bay. Ignition Zone: A helicopter compartment containing equipment, structure or environment, which is normdly an ignition source. Example: Inverter compartment. Possible Fire Zone: A region in which an ignition source, together with combustibles, combustible fluid line leakage, or combustible mix
48、tures, may exist at some time during airplane operation. The possible ignition source or combustibles might be contained within the region, or might enter the region from an external location during an emergency. At least the following sections, areas, or compart- ments should be considered to deter
49、mine their possible hazards: SAE AIR*L262 74 8357340 0003961 O -6- A. Engine Compartments 1. 2. Engine Power Sections: This section includes burner, turbine and tailpipe. Engine Compressor and Accessory Sections: This section includes the engine accessories. It may be the compressor compartment or other compartment such as a bullet-shaped housing in the engine front face. Complete Power Plant Compartments: These are compartments in which no isolation is pro- vided between the engine power section and the accessory section. 3. B. Auxiliary Power Plant Installation Sections. C.
