On Sunday, in an article about the F-35, Luke Air Force base reported that the 56th Logistics Readiness Squadron recently painted an old fuel truck “to reduce the temperature of fuel being delivered to the F-35 Lightning II joint strike fighter.”
The article noted that the “F-35 has a fuel temperature threshold and may not function properly if the fuel temperature is too high. “ As a result of the change, “the 56th LRS hopes for no delay in aircraft take-offs, all while maintaining mission sorties and ensuring pilots meet training requirements.”
Chief Master Sgt. Ralph Resch, the 56th LRS fuels manager said that in order for the F-35 to meet its sortie requirements, “We are taking proactive measures to mitigate any possible aircraft shutdowns due to high fuel temperatures in the future.”
Aside from the fact that the F-35A’s wing is not optimized for many USAF missions, and the fact that the Air Force does not possess a combat bullet for the F-35, and the fact that the ALIS system will make forward operations difficult, the Sortie Generation Rate (SGR) is very high; in excess of 3 per day for F-35A. In other words, if jet doesn’t break, it should be able to get turned pretty fast, according to pilots.
However because the SGR is so high, the issues with thermal cooling are serious concerns.
According to experts:
What matters for SGR is that when an aircraft lands, it is hot and hot all over. The gun system and the bullets are designed as a heat sink. General Dynamics has fully tested the gun system and PGU-23 TP in that environment, but not the planned combat round (PGU-20 DU).
As a result, when the jet lands on a hot day, the aircraft is hot. Putting fuel into it will immediately cool it off. However, no one knows what will happen on the 2nd sortie of the day. Is the aircraft able to cool off back to the point it was when it started its systems up at the beginning of the day?
Airflow through the aircraft does not cool the aircraft so when electronic systems generate heat, the thermal management system has to find a way to remove that heat so as not to melt the internal components. The main method for doing this on the F-22 and F-35 is using PAO (Polyalphaolefin), a flammable liquid.
PAO lines runs throughout the systems and absorbs heat from the electrical components. The PAO lines then run through the fuel cells and release heat into the fuel. For the aircrafts’ engines this increases their performance by preheating the fuel while fixing the cooling issue for the aircraft. What becomes an issue is when it is hot outside and the engine is running at low power (before takeoff). It is also a problem when running the engine at high power because the engine becomes a heat generator at that point. To solve this problem, the aircraft profile for the F-35 is to climb to 30,000′, cool the aircraft down for a while, then execute the mission profile.
Once the plane gets extremely hot in the air, the only solution is to turn off components like the radar. If the aircraft will have serious problems most likely if it is at low altitude for a long period of time in high power settings.
At $98 million apiece, the taxpayer expects more for their money. While they admire the creativity of ground crews searching for a solution to the F-35’s problems, taxpayers question the need.
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