Bill Sweetman teases out some information which sheds some light on the relatively low thrust to weight ratio of the F-35 JSF, the fact that the Pratt & Whitney F135 engine has a thrust to weight ratio of only 6.6:1.

By comparison, the F-100 engine (F-15, F-16), whose contract was awarded in 1970, has a thrust/weight ratio of 7.8:1, and the more modern F414 and EJ2000 (Superbug and Typhoon) exceed 9:1 thrust to weight.

Additionally, he notes that the vertical lift system used on the F-35B weighs 10,472 pounds with a thrust of 40,550 pounds, giving a thrust to weight ratio in that mode of 3.87:1, as compared to 5.6:1 for the Rolls Royce Pegasus used on the Harrier.

There is a saying that you can’t make a race horse out of a pig, but you can get an awfully fast pig, the F-4 Phantom comes to mind, but this is not a fast pig.

Pics of the F135 promotional brochure are from here.