Hey, Ed, M 0.1 is a maximum cruising speed for most old fuds on the
Green Stamp.
BTW I don't think that OAT probe has much to do with the radar. I'd
suspect it's for the air data computer to feed the Machmeter (for some
reason the 21 has a big one, probably so the pilot will fly the exact
Mach commanded by his controller) and the engine and anti-ice systems.
BTW when the 21 was first placed in commission Sov philosophy didn't
allow the interceptor pilot much freedom at all; he was essentially
just the interface between the GCI controller and the two Atolls. I
used to watch their training intercepts on GCI radar at one base i was
at.
Cheers - Walt BJ