Roller-Smith WWII Aircraft Instrument SA-1A /

Description

WWII Aircraft Instrument SA-1A / ARN-1 Radio Altimeter Altitude Limit Switch USN

One really homely looking wartime SA-1A / ARN-1 Radio Altimeter Altitude Limit Switch that would've been found in the Navy's torpedo and patrol bombers during WWII and in some USAAF transports. You'd have found this one lurking on the instrument board of the Grumman TBM and TBF Avengers , the Lockheed PV-1 Ventura and the PV-2 Harpoon , Consolidated PBY Catalina , the PBM-5 Mariner , SB2C Helldiver , and the Convair PB4Y-2 Privateer on Navy row. The USAAF used them as well in the Douglas C-47 "Skytrain" transport.

Post war you might have found this system in the A-1 Skyraider , too.

What the heck is it, you ask?

This instrument - a rotating 11 position switch, as properly termed - was part of Radio Set APN-1. This system was designed to assist in measurement and indicate to the pilot altitude over terrain during flight - specifically low altitude - where monitoring height over terrain was critical. The instrument here was coupled with an Altitude Indicator instrument which was used to set a determined altitude at which flight was desired between the range of 50 to 300 feet and from 500 to 3000 feet. This switch system has detents starting at 50 feet incremented in 25 foot intervals to 300 feet. The switch and instruments used lights on the instrument board to indicate height - Amber light on dash indicated flight ops were at SET altitude. The Green light would indicate flight was above the set altitude. You didn't want to see the Red light come on as that'd indicate you were flying below the set altitude. And that meant bing! bang! boom! ouch! coming your way shortly.

Phenolic data plate on the unit is on the rear of the instrument reads:

SA-1A / ARN-1

110 FB / 336

NXsa - 62370 568 :CQC

She's ugly. One of the treasures as found decades ago in the cast-off pile from a scrapping operation that carved up most of the Navy's patrol and torpedo bombers here in AZ in the late 1950s. The housing is dirty, the back of the instrument has a few bumps - BUT she's all complete and glass is intact. From time to time we get asked for instrument that look worn and faded and distressed but complete for installation in a vintage panel. If you needed a less-than-perfect SA-1A, well, here it is. The selector knob works great. You could take this one apart, clean it, and it'd look great. Plenty of spare parts here if you needed them for fixing another example.

I don't know who contractor CQC was. Roller-Smith made the instrument it was coupled to - but no clue as to the maker of this switch. This one looks like it was last inspected or OH'ed in 1952. These were cheap, cheap, cheap in the war surplus catalogues like Palley's Supply in the early 1960s. You could get them brand-new in a box for about $1.95 and they were sold as multi-position switches. Need the 5 pin Cannon plugs for these units? We have those, too.

So these came from an absolute pile of instruments probably removed from Catalina, Privateers and Avengers that were scrapped at Litchfield Park Naval Air Facility in Goodyear, AZ in the late 1950s. The instrument boards were pulled out of the airplanes and the airframes fed into the furnace to pop back out as aluminum ingots. So many of the "nice" useful instruments were sold off on the surplus marketplace and found their way into GA aircraft. The altimeters - the VSI, the directional gyroscopes - all of those had a direct application and need in the GA market (albeit flooded already with a glut of wartime instruments). But these little SA-1As - not so much. They were the lonely stepchildren nobody wanted. I remember as a kid seeing a scrap yard seller grabbing random ones like this and throwing them against other items in the yard just to hear them shattered and break. Pretty sad. I think that caught me in my formulative years and we've got buckets and buckets of "ugly children" like these that I am trying to home late in life. In fact, take one of these and you have offer of a free feral kitten from our yard if you desire it.

Radium? Probably.

Ships cheapest via USPS Ground Advantage or FedEx Ground unless you direct otherwise. Questions? Please ask seller. And thanks for looking!