Jet fuel

[53' Stude]

Good Morning. As most of you folks know; my stepfather is a retired U.S. NAVY aviator and USAIR pilot. Taught me tons about aviation. We are watching some videos on the U-2 and SR-71 aircraft and others. I find it interesting that SHELL Oil developed JP-7 fuel.

enjoy

JP-7 - Wikipedia

en.wikipedia.org

 

[WyrTwister]

My understanding is the SR-71 uses a high flash point fuel . I am guessing the U-2 uses " standard " jet fuel ?

 

[tom slick]

My understanding is the SR-71 uses a high flash point fuel . I am guessing the U-2 uses " standard " jet fuel ?

The U-2 uses a variant of the GE F-118 engine used in the B-2, which a variant of the F-110 engine used in multiple fighters. They all run on JP-8, which is regular military jet fuel.

 

[tom slick]

Interesting fact about the SR-71: the fuel uses TEB to ignite. The maximum mission time was limited by the number of refuelings because they had a limited amount of TEB to reignite the afterburners after fueling.

 

[53' Stude]

The U-2 uses a variant of the GE F-118 engine used in the B-2, which a variant of the F-110 engine used in multiple fighters. They all run on JP-8, which is regular military jet fuel.

Tom: thanks for the info. Wikipedia on the U-2 initially said U-2 used JP-7. I’m confused. I believe you, as you have a wealth of knowledge

 

[tom slick]

Tom: thanks for the info. Wikipedia on the U-2 initially said U-2 used JP-7. I’m confused. I believe you, as you have a wealth of knowledge

As far as I know JP-7 was only used in the J-58 engine. The U-2 never used that engine, it would rip its wings off. Also, the SR-71 operated in extreme heat creating the need for special fuel. The U-2 is slow and operates at very low temperatures. All are extreme engineering marvels developed by brilliant engineers.

 

[53' Stude]

Thank You Tom for the clarification

 

[Astro14]

By the way, TEB is tri-ethyl-borane. It’s hypergolic, meaning it spontaneously combusts on exposure to air. Pretty risky stuff to handle, but regular igniters wouldn’t light off the JP-7. So, a shot of TEB for start. And a shot of TEB for each AB light. The counter in the cockpit kept track of each TEB use and the limit, I believe, was 20.

 

[53' Stude]

Astro14: Thank You for the info.

 

[97prizm]

The SR-71 only had 12 shots of TEB according to a pilot I met who lives in Colorado Springs

 

[Astro14]

That may be true - never flew the airplane, so couldn't tell you exactly. It might also be that 12 was the SOP (Standard Operating Procedure) limit, even if the reservoir held more. Often, operating standards were kept well short of actual systems limits for reliability in mission execution.

According to the flight manual, the 600cc TEB tanks were good for "at least 16 metered TEB injections"...

SR-71 Online - SR-71 Flight Manual: Section 1, Page 1-22

SR-71 Flight Manual: Section 1, Page 1-22

www.sr-71.org

 

[Dodgetracker]

J58 The Powerplant for the Blackbirds

The Pratt & Whitney J58 (company designation JT11D-20) was a jet engine that powered the Lockheed A-12, and subsequently the YF-12 and the SR-71...

www.thesr71blackbird.com

copied from above
The engine's high operating speeds and temperatures required a new jet fuel, JP-7. Its reluctance to be ignited required triethylborane (TEB) to be injected into the engine to ignite it and the afterburner. Above -5 °C, TEB spontaneously ignites in contact with air. Each engine carried a nitrogen-pressurized sealed tank with 600 cm3 (20.7 ounces) of TEB, sufficient for at least 16 starts, restarts, or afterburner lights; this number was one of the limiting factors of SR-71 endurance, as after each air refueling the afterburners had to be reignited. When the pilot moved the throttle from cut-off to idle position, fuel flowed into the engine, and shortly afterwards an approx. 50 cm3 (1.7 ounce) shot of TEB was injected into the combustion chamber, where it spontaneously ignited and lit the fuel with a green flash. In some conditions, however, the TEB flow was obstructed by coking deposits on the injector nozzle, hindering restart attempts. Refilling the TEB tank was a perilous task; the maintenance crew wore silver fire suits.[21] Conversely, the JP-7 fueling was so safe that some aircraft maintenance was permitted during filling. The chemical ignition was chosen instead of a conventional igniter for reliability reasons, and to reduce mechanical complexity. The TEB tank is cooled with fuel flowing around it, and contains a disk that ruptures in case of overpressure, allowing TEB and nitrogen to discharge into the afterburner.

The fuel flowing into the engine is used as a coolant to cool the engine, hydraulic fluid, oil, TEB tank, afterburner nozzle actuator control lines, air conditioning systems, and the parts of the airframe subjected to aerodynamic heating.

 

[tom slick]

This test cell video shows the green flashes from TEB ignition. A boom out the back of any other engine would indicate a problem.

 

[wpod]

Read the book https://www.amazon.com/Skunk-Works-Personal-Memoir-Lockheed/dp/0316743003

 

[Astro14]

Read the book https://www.amazon.com/Skunk-Works-Personal-Memoir-Lockheed/dp/0316743003

A favorite of mine. Great book!

 

[y_p_w]

The U-2 uses a variant of the GE F-118 engine used in the B-2, which a variant of the F-110 engine used in multiple fighters. They all run on JP-8, which is regular military jet fuel.

It's my understanding that a lot of fuels are more or less interchangeable even if not military spec. At least the ones that are fairly similar to Jet-A. The US Air Force claims that they've converted to commercial Jet-A with certain additives. It makes the supply chain a lot easier to deal with. When US military aircraft refuel at commercial airports, all they get is straight up commercial Jet-A anyways.

Air Force completes historic fuel conversion

The Air Force took an important step in fiscal responsibility and supply chain efficiency as it converted its final stateside installation from Jet Propellant 8 (JP-8) fuel to the more common and

www.af.mil

WASHINGTON (AFNS) -- The Air Force officials took an important step in fiscal responsibility and supply chain efficiency with the conversion of the final stateside installation from Jet Propellant 8 (JP-8) fuel to the more common and commercially available Jet A fuel, Oct. 29 at Wright Patterson Air Force Base, Ohio.

The transition to Jet A completed a process where the Air Force, in partnership with the Defense Logistics Agency, converted 130 stateside Air Force fuels locations in less than five years, approximately 18 months ahead of the estimated 2016 conversion completion date.

The US Navy still uses JP-5. I've taken a few tours of US Navy ships. On one destroyer I asked what the fuel smell was, I was told it was JP-5 used to power the turbines (which are basically just jet engines powering a shaft) and I guess some to fuel their helicopters. However, they could probably use different fuels in a pinch. I'm pretty sure that US Navy aircraft refueling at other facilities aren't getting JP-5.