The F-35: Even the engine is compromised

 

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 U.S. jet engines is measured in pounds 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 were as efficient as that of the F-15, the F-35 would be able to fly 22% farther 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 of 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 burn in only a narrow range of mixtures near the stoichiometric ratio (the ideal ratio that leaves no unburned 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 U.S. 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 the F-35A will cost $85 million each at full rate production.  That is a number plucked from thin air and is simply unbelievable. 

If there is one country that appreciates value in its military hardware, it is Israel, the continued existence of which depends on making the right choices in equipment.  Israel is taking a couple of squadrons of F-35s but only because they are being effectively gifted to the Israelis by the United States.  The Israelis are tricking up their F-35s with their own modifications.  But what Israel wants from here is more F-15s

What the Israelis are likely to be very aware of is the F-35's low availability and reliability.  From page 83 of the Director, Operational Test and Evaluation's annual report released in December 2016: "Aircraft fleet-wide availability averaged 52 percent for 12 months ending October 2016, compared to the modest goal of 60 percent. It is important to note that the expected combat sortie rates will require significantly greater availability than 60 percent; therefore, if the F-35 is to replace legacy aircraft for combat taskings, availability will likely need to improve to near 80 percent."

Also from page 83, "reliability metrics related to critical failures have decreased over the past year. This decrease in reliability correlates with the simultaneously observed decline in the Fully Mission Capable (FMC) rate for all variants, which measures the percentage of aircraft not in depot status that are able to fly all defined F-35 missions. The fleet-wide FMC rate peaked in December 2014 at 62 percent and has fallen steadily since then to 21 percent in October 2016."  So reliability has gone backward, and only one in five F-35s at a time might be able to fly a combat mission.  This is ten years after the first plane came off the production line.

There is no shame in making a lemon as long as it is abandoned before it does too much harm.  The Europeans tried to make their own versions of the Apache and Blackhawk helicopters, in the form of the Tiger and NH-90, respectively.  After at least ten years of service for each type, the readiness rate of the Tiger helicopter is only 21 percent and that of the NH-90 helicopter 40 percent.  Users are giving up on the European copies and prefer the American originals.  The situation is reversed in fighter aircraft – the Eurocanards work, while the F-35 is a hangar queen.

David Archibald is the author of American Gripen: The Solution to the F-35 Nightmare.

 

 

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 U.S. jet engines is measured in pounds 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 were as efficient as that of the F-15, the F-35 would be able to fly 22% farther 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 of 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 burn in only a narrow range of mixtures near the stoichiometric ratio (the ideal ratio that leaves no unburned 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 U.S. 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 the F-35A will cost $85 million each at full rate production.  That is a number plucked from thin air and is simply unbelievable. 

If there is one country that appreciates value in its military hardware, it is Israel, the continued existence of which depends on making the right choices in equipment.  Israel is taking a couple of squadrons of F-35s but only because they are being effectively gifted to the Israelis by the United States.  The Israelis are tricking up their F-35s with their own modifications.  But what Israel wants from here is more F-15s

What the Israelis are likely to be very aware of is the F-35's low availability and reliability.  From page 83 of the Director, Operational Test and Evaluation's annual report released in December 2016: "Aircraft fleet-wide availability averaged 52 percent for 12 months ending October 2016, compared to the modest goal of 60 percent. It is important to note that the expected combat sortie rates will require significantly greater availability than 60 percent; therefore, if the F-35 is to replace legacy aircraft for combat taskings, availability will likely need to improve to near 80 percent."

Also from page 83, "reliability metrics related to critical failures have decreased over the past year. This decrease in reliability correlates with the simultaneously observed decline in the Fully Mission Capable (FMC) rate for all variants, which measures the percentage of aircraft not in depot status that are able to fly all defined F-35 missions. The fleet-wide FMC rate peaked in December 2014 at 62 percent and has fallen steadily since then to 21 percent in October 2016."  So reliability has gone backward, and only one in five F-35s at a time might be able to fly a combat mission.  This is ten years after the first plane came off the production line.

There is no shame in making a lemon as long as it is abandoned before it does too much harm.  The Europeans tried to make their own versions of the Apache and Blackhawk helicopters, in the form of the Tiger and NH-90, respectively.  After at least ten years of service for each type, the readiness rate of the Tiger helicopter is only 21 percent and that of the NH-90 helicopter 40 percent.  Users are giving up on the European copies and prefer the American originals.  The situation is reversed in fighter aircraft – the Eurocanards work, while the F-35 is a hangar queen.

David Archibald is the author of American Gripen: The Solution to the F-35 Nightmare.

 

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