Can aircraft fuel be mix?can jp8 mix with jp4?? any things to take note if it is allowable?

Answer 1

Ok the manufactures of the Engines will tell you NO. The FAA will tell you NO. In Regular Service the answer is NO.

BUT
Turbines will Burn just about any fuels from Kerosene to Diesal to Commerical Grade Car Gas. This can and DOES shorten the life of the Engine. I would NOT recommend this except under the most DIRE of circumstances. FOR EXAMPLE WAR TIME WITH A REGUALR SUPPLY OF FUEL NOT AVALIABLE.
By the Way the same JP8 that goes in USAF Planes also goes into the Diesal Engines of the Vehicles. It just gets Filtered more for the planes.

Answer 2

I like Cody C's answer best. I have mixed Jet A, Jet B and Jet 50 before. A lot depends on your situation. I would't want to put in Jet A if I were in -40 temps. But if you work with the lowest factor (the weakest link so to speak) there should be no problem.

Answer 3

Provided that the engines are certified for it, the fuels can be readily mixed. The fueling ports or SPPR, (single point pressure refueling) panel will tell the lineman what fuels are acceptable for use in the aircraft.

One that comes to mind is the Canadair Challenger 604, which is placcarded to operate on Jet A, Jet A-1, Jet B, JP-4, JP-5 and JP-8. The airplane doesn't care how much of one type of fuel is in the tanks before another of it's certificated fuels is added.

The Pilot's Operating Handbook, (POH,) will further state the fuels that will provide acceptable performance for the engines in an emergency. The list will limit the amount of time the engines can be operated on a substitute fuel before they require overhaul.

As noted before, turbine engines will run on virtually anything that will burn, (many former aviation engines that now are used to produce electrical power, run on natural gas and propane.) Typical listings for acceptable emergency fuels include, in order of preference; home heating oil, kerosene, diesel fuel, aviation gasoline, (avgas,) automotive gasoline (mogas,) and white gasoline, (truly and emergency, camping fuel.)

Noteworthy to operating on emergency fuels is that altitude, and power settings, will be limited to prevent parafins from settling out of heavier fuels and due to the unregulated vapor pressure of automotive and camping fuels.

All flight turbine engine fuels sold today are a kerosene based fuel. The difference between Jet A and Jet A-1 is the temperature at which the fuel will gel in the tanks. Jet A is the standard for domestic travel as the aircraft won't be at altitudes where the fuel can gel for long enough for it to gel and Jet A-1 is the standard for international flights where the aircraft will be at altitudes where the temperature is low enough, for long enough, to make the fuel turning into a gel in the tanks a problem.

Jet B is called, by the refineries, a "wide cut" kerosene, which is about 30% aviation kerosene and 70% avgas. For ground ops when I was at school, we "blended" our own "jet b" from diesel fuel and 93 octane unleaded, all from the same truckstop, to run our old J-34 engine.

JP-5, roughly the equivalent of Jet A or Jet A-1, was originally a Navy fuel used because required a higher temperature to provide enough vapor to reach it's LFL, (lower flamability limit,) and it's LEL, (lower explosion limit,) than JP-4. JP-5, like many other things aviation adopts from the military, became more or less standard.

So, yes, provided the aircraft is placcarded to operate suitably on the fuel, they can be mixed and substituted interchangeably without any concern from a flight aspect.

A maintenance concern can arise from the use of anti-icing additive that's required by some aircraft such as the 20 series and 35 model Learjets, Cessna 500 series, Pilatus and TBM 700. Commonly referred to as "Prist," and carrying an ASTM/DERD number I don't remember, the chemical is added to jet fuels to prevent the water that's dissolved in the fuel from freezing and clogging the fuel filters, thereby causing fuel starvation to the engines of jet aircraft without a fuel heating system.

Prist, which several oil companies only offer preblended, will over years, cause a chemical sludge to occur in storage and aircraft fuel tanks that's referred to in the field as "Apple Jelly", requiring more frequent fuel tank and system maintenance. BP and AvFuels offer only preblended fuel, Chevron and Exxon come to mind as refusing to offer preblended fuel to prevent Apple Jelly.

And the other notable thing I can think of is that an aircraft certified to operate on Jet A, JP-5 or JP-8 is likely to notice a higher EGT, (exhaust gas temperature,) for the power setting if operating on Jet B or JP-3. This is because jets meter fuel by weight/time as opposed to gallons/time. Gasolines run six pounds per gallon, and the standard calculation for jet fuels is between 6.7 to 6.9 pounds/gal. A jet is going to pour more of the wide cut fuel, or emergency fuel lighter than true kerosene fuels at a greater number of volume/time, resulting in higher EGT's, shortened leg length and shorter times between hot section inspections if this is a regulr practice.