Expert: Heiko Hanusch - 3/22/2006

Question
Capt. Hanusch,

Could you please explain the concept of 'spooling' in a jet engine?

Thanks

Answer
Hi Jascha,

Thank you for another question. I hope you are doing well.

Spooling is actually a very straightforward and easy concept to understand.
All it means is, the time it takes a jet engine to go from idle thrust to any other (higher) thrust setting.
Especially older engines (jets, low bypass ratio) take up to 8 seconds to go from idle to max thrust which is a concern in a go around condition. It is not uncommon for an older jet to actually touch down while performing a go around for that same reason.
This can also play a role in Windshear because it will take longer to escape. That is why Turboprops are actually easier to get out of a windshear event than jets, because a turboprop engine has almost no (~ 1sec.) spool time lag!

I hope this helps,

H2