Yes they are, but if they were flying into IMC (Instrument Meteorological Conditions) and lost communications, that would be bad. On an IFR flight plan Center would note their lack of compliance with routing and give vectors off the old magnetic compass, get them somewhere in VMC (Visual Meteorological Conditions) where they could do a visual approach. Still hazarding a flight. I would hang him for the intent if not the successful completion of trying to commit murder.
From what I've read, he did this to get overtime pay to fix it. So he expected the plane to cancel the flight so he could work on it.
I don’t know how the perp gets off with less than attempted murder, other than he’s a nice Muslim who said he “meant no real harm” ! Sheesh, he should have known exactly what was at risk and disabled it anyway. Just as you explained.
He’d been a mechanic since the blooming 80’s. Unbelievable.