Was reading in Shattered Sword a description of the mechanics of putting together a Japanese carrier strike in 1942. I had never realized that you needed to warm up a radial engine for about 15 minutes before it was safe to take off. Was wondering:

 

1) Do you needed to warm up a jet engine?, and

2) if so, for how long?

 

Also, got me wondering, how many aircraft can a catapult launch how quickly?

 

Figured you guys might know.

Was reading in Shattered Sword a description of the mechanics of putting together a Japanese carrier strike in 1942. I had never realized that you needed to warm up a radial engine for about 15 minutes before it was safe to take off. Was wondering: 1) Do you needed to warm up a jet engine?, and 2) if so, for how long?

 

I'm no jet engine mechanic, but I would say yes, but thanks to auxiliary power unit (APUs) and modern technology, we're talking only a few minutes.

 

I'd guess much of the 'warm up' time is dedicated to just making sure everything is running as it should.

 

Also, got me wondering, how many aircraft can a catapult launch how quickly?

 

With four catapults on a Nimitz, I think the rule of thumb is two aircraft every 37 seconds in daytime and one per minute at night.

 

This is not the same as overall sortie rate, however.

Was reading in Shattered Sword a description of the mechanics of putting together a Japanese carrier strike in 1942. I had never realized that you needed to warm up a radial engine for about 15 minutes before it was safe to take off. Was wondering:

 

1) Do you needed to warm up a jet engine?, and

2) if so, for how long?

 

"jet" engines have a few parts that spin very fast with extremely close tolerances and at very hot operating temperature. I don't know times and guess it depends on the materials used in the most demanding parts but generally warm up is necessary to get everything evenly heated up to an acceptable level before going to operating speeds and pressures. The turbine blades are pretty vulnerable and I seem to remember pretty trick metallurgy gets used there in modern units, that would undoubtedly help. There are also means available (and I think only used in military applications) where effective preheating is used to shorten warm ups.

 

Probably something in general aeronautic engineering sites (or paper in the library ) that would explain it. I'd be interested to hear what you find out if you look further.

Don Thomas

Googling the question "do jet engines require warmup?" gives a number of sites and fora to look at, the consensus seems to be that it's a good idea to let the engine idle for 3-5 minutes to get everything up to operating temps and stabilized. Failure to allow this warmup time can apparently cause engine failures, sometimes of the 'bits falling off the airplane' variety. OTOH, this is about the amount of time it takes to run through the post-start checklists, so you aren't actually losing any extra time or burning any extra fuel to do it.

IIRC, the Vulcans could get airborne 2 minutes from cold start.