CS 25J1041 General

ED Decision 2005/006/R

(See AMC 25J1041.)

The APU cooling provisions must be able to maintain the temperatures of APU components and fluids within the temperature limits established for these components and fluids, under critical ground and flight operating conditions, and after normal APU shutdown.

 [Amdt 25/1]

AMC 25J1041 General

ED Decision 2005/006/R

The need for additional tests, if any, in hot climatic conditions should take account of any tests made by the APU constructor to establish APU performance and functioning characteristics and of satisfactory operating experience of similar power units installed in other types of aeroplane.

The maximum climatic conditions for which compliance will be established should be declared and this should not be less severe than the ICAO Intercontinental Maximum Standard Climate (37·8°C (100oF) at sea-level). If the tests are conducted under conditions which deviate from the maximum declared ambient temperature, the maximum temperature deviation should not normally exceed 13·9°C (25°F).

[Amdt 25/1]

CS 25J1043 Cooling tests

ED Decision 2005/006/R

(a) General. Compliance with CS 25J1041 must be shown by tests, under critical conditions. For these tests, the following apply:

 (1) If the tests are conducted under conditions deviating from the maximum ambient atmospheric temperature, the recorded APU temperatures must be corrected under sub-paragraph (c) of this paragraph.

 (2) No corrected temperatures determined under sub-paragraph (a)(1) of this paragraph may exceed established limits.

(b) Maximum ambient atmospheric temperature. A maximum ambient atmospheric temperature corresponding to sea level conditions must be established. The temperature lapse rate is 2.0°C per 300 metres of altitude above sea level until a temperature of -56.5°C is reached, above which altitude, the temperature is considered constant at -56.5°C.

(c) Correction factor. Unless a more rational correction applies, temperatures of APU fluids and components for which temperature limits are established, must be corrected by adding to them the difference between the maximum ambient atmospheric temperature and the temperature of the ambient air at the time of the first occurrence of the maximum component or fluid temperature recorded during the cooling test.

[Amdt 25/1]

CS 25J1045 Cooling test procedures

ED Decision 2005/006/R

(a) Compliance with CS 25J1041 must be shown for the critical conditions that correspond to the applicable performance requirements. The cooling tests must be conducted with the aeroplane in the configuration, and operating under the conditions that are critical relative to cooling. For the cooling tests, a temperature is 'stabilised' when its rate of change is less than 1°C per minute.

(b) Temperatures must be stabilised prior to entry into each critical condition being investigated, unless the entry condition normally is not one during which component and APU fluid temperatures would stabilise (in which case, operation through the full entry condition must be conducted before entry into the critical condition being investigated in order to allow temperatures to reach their natural levels at the time of entry).

(c) Cooling tests for each critical condition must be continued until:

 (1)  The component and APU fluid temperatures stabilise;

 (2)  The stage of flight is completed; or

 (3)  An operating limitation is reached.

[Amdt 25/1]