Advisory Circular (AC) No. 500-015 Issue 1 - Appendix B

REQUIREMENT: 25.955 - Fuel Flow

(a) Each fuel system must provide at least 100 percent of the fuel flow required under each intended operating condition and manoeuvre. Compliance must be shown as follows:
 

(1) Fuel must be delivered to each engine at a pressure within the limits specified in the engine type certificate;
 

(2) The quantity of fuel in the tank may not exceed the amount established as the unusable fuel supply for that tank under the requirements of Sec. 25.959 plus that necessary to show compliance with this section;
 

(3) Each main pump must be used that is necessary for each operating condition and attitude for which compliance with this section is shown, and the appropriate emergency pump must be substituted for each main pump so used; and
 

(4) If there is a fuel flow meter, it must be blocked and the fuel must flow through the meter or its bypass.
 

(b) If an engine can be supplied with fuel from more than one tank, the fuel system must:
 

(1) For each reciprocating engine, supply the full fuel pressure to that engine in not more than 20 seconds after switching to any other fuel tank containing usable fuel when engine malfunctioning becomes apparent due to the depletion of the fuel supply in any tank from which the engine can be fed; and
 

(2) For each turbine engine, in addition to having appropriate manual switching capability, be designed to prevent interruption of fuel flow to that engine, without attention by the flight crew, when any tank supplying fuel to that engine is depleted of usable fuel during normal operation, and any other tank, that normally supplies fuel to that engine alone, contains usable fuel.

MEANS OF COMPLIANCE:

(a) Rig test; and
 

(b) Flight test.

METHOD OF COMPLIANCE:

(a) Engine requires 30 litres/min @ 15 P.S.I. minimum. See Installation Manual.
 

(b) Critical fuel to be used in Rig test is JP4 @ -40 degrees C.
 

(c) Minimum fuel to be tested was established at 36 litres. See FAR 25.959 report #6.
 

(d) Critical attitude for fuel flow nose up 23.5 degrees. See attitude analysis contained in Report #17.
 

(e) Rig test (Test Plan #13) to demonstrate flow rate for main and emergency pumps. Rig test will consist of a mock up of fuel system. See attached sketch all fittings, tube runs match production fuel system except: length of tube @ location x has no effect. See attached calculation/analysis.
 

(f) Flight test to demonstrate fuel tank switching from tank 1 to 2. Engine @ cruise setting, altitude 25,000 feet. See test sequence (Test Plan #14).

 

COMPLIANCE DOCUMENTS, DATA AND TESTING WITH SCHEDULE:

(a) Report 6A (due Day Month Year)
 

(b) Test Plan #13 (due Day Month Year)
 

(c) Test (due Day Month Year)
 

(d) Report 6B (due Day Month Year)
 

(e) Test Plan #14 (due Day Month Year)
 

(f) Flight Test (due Day Month Year)
 

(g) Report 6C (due Day Month Year)

LEVEL OF DELEGATION:

Level of Delegation: Finding of compliance to FAR 25.955(a) delegated.

LEVEL OF INVOLVEMENT:

Level of Involvement Matrix: