Aircraft Engine Fuel Pump Cavitation Endurance Test
This SAE Aerospace Recommended Practice (ARP) defines procedures for testing aircraft engine fuel pumps for the purpose of determining their resistance to deterioration, during steady state endurance test, while receiving MIL-T-5624 Grade JP-4 fuel as a homogenous mixture of gas and liquid expressed as a ratio of vapor volume to liquid volume (V/L).<p>If any of the above conditions do not apply, refer to Section 2.<p>The procedure recommended herein is based on experience gathered by a number of laboratories conducting component qualification tests to MIL-E-5009, currently MIL-E-5007. It is intended to produce a uniform reproducible steady state test condition for fuel pump cavitation testing as required by various military engine specifications.<p>This test is not intended to establish altitude or climb rate, starting, or other transient performance of the article tested.
Rationale: ASTM D1655 Jet A, Jet A-1 and worldwide equivalents have been the principal jet fuels used by the commercial aerospace industry for many decades now. More recently, the use of Russian TS-1, RT fuels and Chinese No 3 fuel by worldwide – airlines has increased significantly.
Engine and airframe manufacturers depend on knowledge of many fuel properties outside the normal specification properties for design issues. These properties are commonly referred to as the ‘fit-for-purpose’ properties. One such property is the air solubility coefficient, which is used in the determination of two-phase flow conditions in fuel system components under suction conditions.
SAE Aerospace Recommended Practice ARP492 is the industry standard for the aircraft engine fuel pump cavitation endurance test. This ARP is also used to undertake two-phase suction performance tests of engine-mounted fuel boost pumps. The suction performance of a turboshaft engine boost pump is frequently a key characteristic as many modern helicopters rely solely on suction lift operation to transfer the fuel from the fuel tank to the engine fuel pump inlet. The pump has to perform as advertised; there is no back-up.
ARP492 provides two means of determining a two-phase flow condition, by the use of an in-line meter or via a calculation method. The calculation method is based on the - MIL-DTL-5624 Grade JP-4 fuel, a fuel which is being phased out. In SAE Aerospace Information Report AIR1326 it states ‘The solubility coefficient “k” for fuels can be calculated by the formula in ARP492A, Appendix 1, A4.1. Additional research however, has shown that the formula is not accurate for kerosene type fuels’. Where a wide-cut fuel has been approved by an engine manufacturer, for example Jet B, its maximum operating temperature has sometimes been restricted to cold weather operation. As such, suction performance testing on the unrestricted kerosene fuels is necessary. Thus the current equation in ARP492 is insufficient for aerospace design engineers to apply to the most popular jet fuels such as Jet A, Jet A-1, or JP-8.