[Paleo Conservative]

Race car is a stretch, but 4 new CF6's would have the same thrust as 6 of the old TF39's.

But they won't be used at full thrust. They will be derated to about 53,000 pounds of thrust. Supposedly this is related to the time on wing guarantees by GE. Still that is almost like putting 5 of the old engines on.

[RayChuang88]

They will be derated to about 53,000 pounds of thrust.

Isn't most versions of the CF6-80 engine rated at under 56,000 lb. of thrust? I believe the engine they're using on the C-5M upgrade program is the same F103-GE-100 engines used on the E-4B command post and VC-25A Presidential transport, essentially a military-certified version of CF6-50 used on the 747-200B and DC-10-30 models.

[CALawyer]

"But they won't be used at full thrust. They will be derated to about 53,000 pounds of thrust."

I think the C-5's current thrust is around 47,000 pounds per engine. The CF6's unfortunately won't produce that unique sound that the original C-5 engines generate. Back in the late 1980s, I used to hear C-5s flying out of Burbank Airport every night (6,800 foot runway) when the planes were used to transport large sections of the F117 stealth fighter up to Palmdale for assembly.

http://www.ktb.net/~billmeco/burc5a.html