Originally Posted by
SonicFlyer
Serious questions about turbofans.... once fuel is cutoff, how soon is it safe to be in front of it? Obviously it is still spinning for a couple of minutes after cutoff and N1 decreases almost instantly, but at what point is there no longer a danger of getting sucked in after fuel cutoff?
Pretty much instantly. The pressure ratio drops to zero almost immediately, that's the woosh-sound you hear when a turbofan engine is shut down.