Refinery process studies have indicated that the relaxation of the JP-5 freeze point specification is a viable means of increasing jet fuel availability. The Naval Air Propulsion Center is investigating the impact of higher freeze point fuels on naval aircraft operations. Six fuels, with freeze points ranging from −55°F to +10°F, were tested in two instrumented external fuel tanks. Thirty hours of flight test and one hundred hours of wind tunnel test data have been accumulated. This information is being used in conjunction with laboratory and bench scale test data to support the development of a three dimensional computer code. This code will predict fuel cool down and hold-up (unpumpable frozen fuel) for any fuel tank geometry during a mission. Initial results indicate that the current JP-5 freeze point specification of −51°F is conservative and could be safely relaxed.

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