CS 25J1093 Air intake system icing protection

(See AMC 25J1093)

(a)Each non-essential APU air intake system, including any screen if used, which does not comply with CS 25J1093(b) will be restricted to use in non-icing conditions, unless it can be shown that the APU complete with air intake system, if subjected to the icing conditions, defined in Appendices C, O and P will not affect the safe operation of the aeroplane. b) For essential APUs: Each essential APU, with all icing protection systems operating, and screen if used, must:

(1)operate throughout its flight power range in the icing conditions defined in Appendices C, O and P, and in falling and blowing snow within the limitations established for the aeroplane for such operation, without the accumulation of ice on the APU, air intake system components or airframe components that would do any of the following:

(i)Adversely affect installed APU operation or cause a sustained loss of power; or an unacceptable increase in gas path operating temperature; or an airframe/APU incompatibility; or

(ii)Result in unacceptable temporary power loss or APU damage; or

(iii)Cause a stall, surge, or flameout or loss of APU controllability (for example, rollback).

(2)operate for a minimum of 30 minutes on the ground in the icing conditions shown in Table 1 of CS 25.1093(b)(2), unless replaced by similar test conditions that are more critical. These conditions must be demonstrated with the available icing protection (if applicable) at its critical condition, without adverse effect. The applicant must document the APU minimum ambient temperature demonstrated, if any, and establish the aeroplane operating limitations. (See AMC 25J1093(b))

[Amdt 25/1]

[Amdt 25/16]

[Amdt 25/18]