SAE The                                                                          AEROSPACE

The Engineering                                                         Information          AIR 1539         

Resource for                                                                                                                                               1ssued 1-30-81

Advancing Mobility                                                                       REPORT               revised*                 

 

400 COMMONWEALTH DRIVE. WARRENDALE. PA. 15096

 

 

ENVIRONMENTAL CONTROL SYSTEM CONTAMINATION

 

1.0 PURPOSE

 

The purpose of this Aerospace Information Report (AIR) is to categorize sources of Environmental Control System contaminants, define the effects of these contaminants on occupants and equipment, and outline design features that can be used to control contamination in aircraft systems.

 

2.0 SCOPE

 

This publication will be limited to a discussion of liquid and particulate contaminants which enter the aircraft through the environmental control system (ECS). Gaseous contaminants such as ozone. fuel vapors, sulphates. etc., are not covered in this AIR. It will cover all contamination sources which interface with ECS, and the effects of this contamination on equipment. Methods of control will be limited to the equipment and interfacing ducting which normally falls within the responsibility of the ECS designer.

 

3.0  TYPES AND SOURCES OF CONTAMINATION

Three types of contamination are of concern to ECS design. The first of these is gaseous or vapor contamination. This may be generated within aircraft components or be present in the operating environment. This material can be introduced into the cabin through the ECS.

 

The second type is liquid contamination which can enter the ECS through an APU or an engine. These liquids usually occur as a result of leaking systems or careless servicing of systems.

                                                                                            

 

The third type and of most concern to the designer is particulate contamination.

This consists or sand and dust. metal and carbonaceous material which may be introduced

into engines, APU's or ground carts as airborne particles or may be vacuumed off runways and ramps during takeoff and landing.

 

3.1  SOURCES OF VAPOROUS CONTAMINATION

     

 

Engine Lube Oil

 

          

Engine compressor bearings upstream of the bleed ports are the most likely sources of lube oil entry in the engine air system and thence into the bleed system contaminating the cabin/cockpit air conditioning systems. Although precautions are taken in the design of the bearings to preclude oil leakage into the compressor air passage, failure conditions can result in the introduction of oil into the airstream. At temperatures above 320C this oil breaks down into irritating and toxic compounds.

                                  

Accessories

 

Accessories located in the engine inlet air stream and driven by the main engine shaft have resulted in the leakage of various fluids into the airstream entering the compressor.