Stall Speed Signal Module - What aircraft?

[2banaviator]

I've come across a WWII, 1942-vintage Stalling Speed Signal Assembly Type D-3, but I've not been able to link its use in any specific aircraft of the era. It clearly is intended to signal alarm in the event that the aircraft reaches adjustable and preset upper (dive or bank?) or lower airspeed limits which will result in a stall, between 100-400 MPH.

I'm speculating that it was used in larger multi-engine aircraft, but have searched through a number of flight manuals of USAAF bombers and transports to no avail.

Below is a photo, with more photos available here: https://aeroantique.com/products/stalling-speed-signal-assembly-type-d-3-wwii-us-army-air-force. Any help is appreciated!

[spencerat6]

I was told it was used in the NAA A-36 but have never been able to verify that. I have a couple of them. Bob

[2banaviator]

Thanks spencerat6. I have an A-36A Erection and Maintenance Manual (dated 1944), but this component is not shown in the section that reviews the Air Speed System or the cockpit. There were no later versions after "A" that may have used this, from what I can discern. Perhaps some A-36A's were modified to use this.

I still believe that other aircraft may have used it. Given that there were only 500 A-36A's produced, it seems coincidental that you and I have a combined 3 of an item that might have only been used in A-36A's.

Although I've not located it in any of its manuals, I'm speculating that it was used in some B-24's....

[CoastieJohn]

FWIW...just looking around I seen this. Not sure if it helps any. American Aero has this. I do believe they had an A-36 laying around there for a bit. Not sure if that proves anything though.

http://www.ebay.ph/itm/Parts-Catalog-St ... 2074924395

[2banaviator]

Thanks for the lead, CoastieJohn. So I purchased the 1942 D-2 and D-3 Stalling Speed Signal Indicator Parts Catalog TO No 05-1-30 for this item to try to find a clue about its use. The D-2 had limits of 50-300 MPH, and the D-3 range was 100-400 MPH, and appears to be the only meaningful difference between the two.

The key clue about its use is this statement in the Description on page 3 (emphasis mine):

"2.Description
a. The Types D-2 and D-3 Stalling Speed Signal Assembly is used on aircraft to affect automatically the release of instrument flying hoods in pursuit airplanes. The Signal Assembly opens and closes electrical circuits at two pre-set indicated airspeeds."

So the clue leads me to believe that this was used in training aircraft equipped with a feature to automatically activate a hood when the selected training scenario is attained. Or a Link Trainer?

I first speculated that this may have appeared on the instructors/attendants panel for the Link Trainers, but upon further reading of this document, a second clue emerged: it was definitely pitot-statically driven. Were the instruments on Link Trainers driven by simulated pitotstatic pressures? And did they have hoods that could be activated automatically? Or were there any training aircraft that might have had this equipment? An upper limit of 400MPH seems a bit high for trainers of the day...

Any other clues or paths to explore would be appreciated!

[JohnB]

While I'm no expert on the devices, every Link trainer I've seen had solid "canopies", thus not needing an aircraft-like folding instrument hood.

[Deuelly]

In the flying hood installation drawings for the P-40 they call for a type D-3.

Brandon

[2banaviator]

In the flying hood installation drawings for the P-40 they call for a type D-3.

Brandon

Thanks Brandon! What is your source document for the citation? Anything you can share? I have a few pdf P-40 manuals but haven't seen that reference in any of them. It would be very helpful.

[Deuelly]

2banaviator, The information is in the P-40 drawings. PM me your e-mail address and I can send you some pictures.

Also, I beleive the upper speed limit setting is so if the plane got away from the pilot in a high speed descent the hood would open.

[spencerat6]

Anyone else have info on these I've had mine 37 years they came out of Buffalo with the P-40 parts. Earl Reinert told me they were used in the NAA A-36 but I've never verified. Bob