12 Biden "green screen" not actually a green screen. (imgur.com) posted 3 years ago by everbe 3 years ago by everbe +16 / -4 14 comments share 14 comments share save hide report block hide replies
In some turbine engines there is a “clutch” brake so you can have the engine running without the rotor turning, or is possible it is the APU (auxiliary power unit).
Your other points are perceptive though.