When was JP-5 first fielded?
- Thread starter Zipper730
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MIflyer
1st Lieutenant
Don't know about JP-5. A friend who was a maintenance chief at Edwards AFB told me about JP-4.
The original plan was to fly jets on just kerosene. But the oil industry pointed out that was not going to be possible. One barrel of oil typically produces about 17 gal of gasoline but only 8 gallons of kerosene or diesel fuel. Producing many thousands of gallons of kerosene for jets would leave you with twice as much gasoline that you did not have a use for. So they invented JP-4, which is a mixture of kerosene and gasoline, and thus makes better use of the fuels you can get out of a barrel of oil.
Before the internal combustion engine became so popular there was no use for the gasoline and oil was refined just for the kerosene (lamps and cooking), mineral spirits (for paints), and tars. The gasoline was too volatile to use in stoves and kerosene lanterns and usually was just dumped in the nearest river.
The original plan was to fly jets on just kerosene. But the oil industry pointed out that was not going to be possible. One barrel of oil typically produces about 17 gal of gasoline but only 8 gallons of kerosene or diesel fuel. Producing many thousands of gallons of kerosene for jets would leave you with twice as much gasoline that you did not have a use for. So they invented JP-4, which is a mixture of kerosene and gasoline, and thus makes better use of the fuels you can get out of a barrel of oil.
Before the internal combustion engine became so popular there was no use for the gasoline and oil was refined just for the kerosene (lamps and cooking), mineral spirits (for paints), and tars. The gasoline was too volatile to use in stoves and kerosene lanterns and usually was just dumped in the nearest river.
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I was taught in A&P school that the earliest jets burned avgas, which had the bad effects of coating the internals of the engine with toxic baked on fuel additives, notably tetraethyl lead. This negatively affected the aerodynamics of burner cans and turbine blades, as well as heat dissipation. We had a J34 at school that had hung for several years under the wing of a P2V7 Neptune and burned 115/145. The hot section looked like it was made of some brown ceramic material.
So straight run kerosene was experimented with, but it wouldn't atomize properly with the nozzles and burner cans designed for avgas, making for difficult ignition and overtemp starts due to large and heavy droplet size, especially at cold temperatures.
Enter JP4, a mixture of kerosene and plain additive free gasoline. Good atomization, no baked on additives, starts well, good energy density. Only trouble is, it's volatile as all hell and has to be handled even more carefully than straight avgas. For the Air Force and shoreside uses, that was a more or less acceptable solution, but at sea, Shangri-La (the Shitty Shang), Oriskany, (the Skinny O), Forrestal (USS Forest Fire), and other shipboard disasters proved it wasn't.
JP5, which is pretty nearly straight kerosene, suffers from a slight energy density deficit, but is much safer to handle, and the state of the art of nozzle and burner can design has improved to mitigate the atomization and ignition issues. Civilian Jet A is roughly the same thing.
I had a part time off hours job at NAS Boca Chica fueling planes with JP4. When a shipboard plane came ashore, we had to defuel it of its JP5, fill it with JP4, and send it to the engine shop to get its fuel controls recalibrated.
Cheers,
Wes
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- Thread starter
- #4
Like hard-deposits?
Wait, I thought jet-fuel was less volatile than gasoline? As for the Oriskany and Forrestal, I thought they were using JP-5 at that point?
As I stated in my post, the entire hot section looked like it was made of a smooth, hard, brownish tan ceramic material.
Today's Jet A and JP5 are less volatile than avgas, and I've heard that JP4 has reduced its gasoline component over the years as well. But, as with so many choices in aviation, it's a trade-off between performance and safety. Kerosene has less energy density than gasoline, but is also less volatile.
As for the flattop fires of '60s, I wasn't there then, but was taught that they accelerated the changeover to JP5. Even though it had been around since the '50s, JP5 apparently caused serious performance penalties in early jet engines, which needed all the help they could get. Once J57-and-better class engines took over the world, kerosene based fuels became more practical. The "working class" history of the '50s and '60s is rife with tales of JP4 disasters. People who lived through that era would likely be more aware of that than younger folks.
Cheers,
Wes
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- Thread starter
- #6
It had to wait until the early type turbine engines were mostly gone. Their fuel nozzles just couldn't achieve the small droplet, fine mist spray with kerosene that they could with gasoline and JP4. A fuel nozzle has to inject a carefully shaped high velocity fog into the center of the burner can which will support a flame suspended in the middle of the space. If the flame comes in contact with the chamber walls you've got an instant over temp. This is what happens in a hot start. If fuel pressure at the nozzle isn't high enough and/or the air velocity too low, the fuel "fog" doesn't stay in suspension but starts to pool on the floor of the chamber, guaranteeing an over temp start, which can lead to crack$ in the burner can$. $$
$$!Avn-Tech
Airman
In 1984, I went into the USAF as a Fuel System Mechanic (42373). We were using JP-4 on our aircraft (A-10, F-4 & F-111). Sometime around 1987 we began shifting to JP-4, because the Navy would not transport JP-4 for us any longer.
During the switch over, planes that did not leak, began to leak and had to be fixed. Once all the leaks were fixed it was not so bad.
I do not know when the Navy transitioned to JP-5.
During the switch over, planes that did not leak, began to leak and had to be fixed. Once all the leaks were fixed it was not so bad.
I do not know when the Navy transitioned to JP-5.
swampyankee
Chief Master Sergeant
- 3,954
- Jun 25, 2013
When I was one of the test engineers at Lycoming, we almost never used JP-4 (the closest I came was a test involving steam heating Jet-B), with almost all our tests with Jet-A, even with the military engines. Gas turbines are not particularly sensitive to fuel, which was kind of emphasized by the LTC4 (civil version of T55) that was running on peat. JP-4 actually has a lower volumetric energy density as the LHV of JP-4 and JP-5 are within about 0.5% and JP-5 is significantly denser.
MiTasol
2nd Lieutenant
It had to wait until the early type turbine engines were mostly gone. Their fuel nozzles just couldn't achieve the small droplet, fine mist spray with kerosene that they could with gasoline and JP4. A fuel nozzle has to inject a carefully shaped high velocity fog into the center of the burner can which will support a flame suspended in the middle of the space. If the flame comes in contact with the chamber walls you've got an instant over temp. This is what happens in a hot start. If fuel pressure at the nozzle isn't high enough and/or the air velocity too low, the fuel "fog" doesn't stay in suspension but starts to pool on the floor of the chamber, guaranteeing an over temp start, which can lead to crack$ in the burner can$. $$
And those cracks can lead to a catastrophic structural failure inside the engine as exhibited by the British Air Tours B737 G-BGJL at Manchester, UK on August 22, 1985
To summarize from the FAA Lessons Learned website - taking off the left engine experienced an engine failure. A piece of the left engine combustor had penetrated a fuel-tank access panel, causing an uncontrollable fuel spill, the fuel ignited and the airplane was burned severely. Fifty-five passengers perished as a result.
That report says The British Civil Aviation Authority (CAA) determined the cause of the accident (fuel spill/ensuing fire) was an engine failure caused by faulty repairs; fragments from that engine failure penetrating a fuel-tank access door. That is a gross oversimplification of the cause and ignores the "it must fly on schedule" time constraints the maintenance technicians were given to solve what appeared to be a simple fuel control problem, but was in fact a cracked burner can which had caused a miss-aligned fuel nozzle. The reason the fuel tank had a large hole torn in it was that a "small" piece of the combustion can (about a foot square) tore free and with some ten tons of air pressure behind it it had enough energy to rip thru the cowls and thru the fuel access panel.
Most of the victims died from toxic chemicals in the smoke emitted by burning cabin linings, seat coverings and the seat cushions, and because so many wanted to get their carry on baggage from the overhead lockers.
The only good to come from this accident was that all seat coverings and cushions and cabin linings must now be made from materials that do not produce toxic vapours when at elevated temperatures, floor path lighting is now mandated and all preflight briefings now must tell you not to get your crap out of the overhead locker and, except on Qantas, during any emergency cabin crews are trained to initiate a cabin evacuation the moment the aircraft comes to rest and the engines spool down. The aircraft must be empty within 90 seconds. On Qantas the captain must initiate the evac. Who are the people most likely to die in an accident? Yep the cockpit crew who are always the first to arrive at the scene and have the highest mortality rate. In the Bangkok 747 accident where the PA system was disabled the first person evacuated left the aircraft after 14 minutes and the last after 21 minutes. There was a massive fuel leak where #3 pylon had punched itself into the wing. On most airlines pax can open emergency exits and your briefing card says you must make sure it is safe before doing so. This slide was deployed by cabin crew.
Back to the original topic - there were two types of kerosene, power and lighting, with different characteristics. Power kerosene, the one needed for aircraft, was also at that time used in many tractors and stationary engines so was in high demand for non aviation purposes. Many early turbine engines that were running on avtur used torch ignitors where a fine spray of avgas was sprayed near a spark plug which ignited it creating a small hot flame that in turn ignited the avtur when that was introduced to the airflow. More things to go wrong.
An additional fact is that kerosene, like avtur, needs a minimum percentage of oil to lubricate the internals of the fuel control. Surprisingly avgas did not need this added oil.
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