Jean-Leon Morin wrote
>My question is - any idea what kind of machine this might be off of? There
>are many mentions of it being for an "S-4" automatic pilot. I don't know
>anything about aircraft so I wonder if this is an obscure part or something
>fairly common. It looks like it might actually be a retrofit.
Well, the model number doesn't spring to mind, but Sperry autopilots were
to be found on a variety of military and converted military aircraft as
late as the mid seventies when I stopped flying for a living. It wouldn't
surprise me if there were still DC-3's, Expediters, and DC-6's still in the
air somewhere "Powered by Sperry." I haven't seen a Sperry in a cockpit
since then but again, I don't fly for a living anymore and I don't often
get a chance to drive from the left seat in anything more serious than a
172 or 185 which generally do not run to wonderful luxuries such as
autopilots, and by god they are wonderful things to have in a
plane. However, there was once a time when Sperry ruled the field.
Sperry pretty well invented the modern autopilot as we know it, both
hydraulic and electric, although I seem to recall that the Germans were
leaders in the electric field at some point.
One thing I do know is that it was a specially built Sperry autopilot that
guided a C-54 from the States to England, I believe, and right down to the
runway at that in 1947. The flight controls were untouched from
taxi-on-active through flare and landing. That stunt is routine with
airliners today but in 1947?
Being a pilot, ("Aircraft Commander" in politically correct speak), I never
had to get my hands dirty in the air force and when bush flying only
allowed by the licensed a&p mechanics to dirty them with straight muck so I
am not familiar with the inner workings of the autopilots. But the bit you
have would have been one of several installed in an aircraft to operate the
flight controls.
Some aircraft such as the Lockheed F104 were stuffed solid with the things
since it flew at speeds that made manual control of the flight controls
impossible. Of course, if you developed a hydraulic pressure problem then
things got real interesting. Other aircraft would have need of fewer
hydraulic servos. There were many variations involving cables, hydraulic
lines, electrical servos, and combinations thereof.
It wouldn't surprise me to learn that the S-4 servo you have is still
available new. Aviation is as conservative as the Roman Catholic Church
when it comes to change and the most unlikely of vintage parts are still
being made for aircraft. Sort of a Land Rover philosophy -- if it worked
for Dad and Grandad then it will work for me attitude.
Rick Grant
1959 SII 88"
VORIZO
Calgary Alberta
www.rickgrant.com
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