The measure of the efficiency of a jet engine is its Thrust Specific Fuel Consumption or TSFC for short. This is its fuel consumption per unit of thrust and for US jet engines is measured in lbs per hour per pound of thrust.
The TSFC of the F100-PW-229 engine that powers the F-15 and F-16 is 0.726 lb/Hr/lb. The F-15 first flew in 1972. More than 40 years later, the TSFC of the F-135 engine which powers the F-35 is 0.889 lb/Hr/lb.
This is 22% higher than the F-15’s fuel consumption despite all the decades of engine development in between. If the F-35’s engine was as efficient as that of the F-15, the F-35 would be able to fly 22% further on its fuel load.
This is a big deal, so what happened?
It all goes back to the original sin of the F-35 in that it was sold as something that would satisfy the needs of all three of the services that have fighter aircraft. For the Marines, this meant an aircraft that could take off and land vertically – which places a particular constraint on the engine used to achieve that. For normal jet aircraft, once they start rolling down the runway to take off there is a ram effect of air being pushed into the engine, aiding the engine’s efficiency. For vertical take-off and landing aircraft though, with no ram effect, the engine must suck in an enormous amount of air to generate the necessary mass of exhaust.
This requires a wide engine with lots of core mass flow. That big core mass flow in turn requires an equivalent amount of fuel as kerosene-air mixtures will only burn in a narrow range of mixtures near the stoichiometric ratio (the ideal ratio that leaves no unburnt fuel or unused air). This means that all the F-35 variants – the F-35A for the USAF, the F-35B for the Marines and the F-35C for the USN – have a wide, draggy, thirsty engine with a range penalty.
That engine is optimized for the F-35B - 14% of the total planned F-35 fleet of 2,443 aircraft for US services. The remaining 86% suffer a 22% range penalty as a consequence.
The F-35 has so many shortcomings that no list of them is complete. But the most up-to-date list is the Project on Government Oversight’s summary of the DOT&E report on the F-35. As that report says, the price tag is the only thing that is stealthy about the F-35.
The procurement cost of the USAF model, the F-35A, was $119.6 million for FY 2016, and $166.4 million and $185.2 million for the B and C models respectively. Lockheed Martin is saying that the F-35A will cost $85 million each at full rate production. That is a number plucked from thin air and is simply unbelievable. (end of excerpt)
Click here for the full story, on the American Thinker website.