Bombing Intervalometer? Anyone ever see this before?

[2banaviator]

Me again, tapping into the collective knowledge of the WIX Community...

I've come across this very interesting artifact and can't determine precisely what system it was a part of, or what aircraft may have had it installed.

Judging from the controls and ground speed disks, I'm hypothesizing that it is a mechanical bombing intervalometer, similar to the AN-B3 used across many bombers in WWII. It has no data plate, but is stamped on the back USN and, inside, its frame is stamped with the USN anchor emblem used on instruments during that era. The ground speed disks are labeled with ordnance types from WWII, but could be pre or post WWII as I've not had a chance to match the list against the years of use of those bomb types. I thought that it may have been a component of the Sperry S-1 system, but I've not been able to confirm.

So what aircraft, flown by the US Navy, would have carried bombs up to 4,000 lbs? My best guess is a PB4Y, or perhaps PBJ.

The photos make it appear small, but it is actually 7.5 inches tall, 6.5 inches wide, and 4 inches deep, and weighs a hefty ~8.5 lbs.

Any ideas?






More info can be found here: https://aeroantique.com/products/ordnance-intervalometer-us-navy.

Feel free to ask any questions and I'll try to answer. I'm not looking to sell it (unless you can use it for a restoration project, just PM me), just want to learn more about it.
Thanks, in advance!

[Cvairwerks]

The M34 was built in 1951 and the M43 in 1962, so you can figure that whatever used that unit was in service in 1962-63. Also, since the M43 was a subsonic weapon, a pretty slow bird carried it. P4M maybe...

[airnutz]

Also P2V mebbee?

[Chris Brame]

Mercators were retired in 1960; Skywarrior maybe?

[2banaviator]

The M34 was built in 1951 and the M43 in 1962, so you can figure that whatever used that unit was in service in 1962-63. Also, since the M43 was a subsonic weapon, a pretty slow bird carried it. P4M maybe...

Some clarification and documentation may help here:

The controller disks show M34 and M43 as the AN-M34 and AN-M43, not without the "AN-" designation. I have a reference document from Sept 1945 that lists both of these, so unless I'm missing something, both were available in 1945. Also, the pages in that document that are specific to those 2 bombs list them as "Obsolescent"(sic). The document is US Bombs and Fuzes(sic), Pyrotechnics, published by the US Navy Bomb Disposal School. I've posted the pdf here: https://aeroantique.com/pages/downloads, and anyone is welcome to download the 366 page document.

The other aspect is that the aircraft must have been capable of carrying multiple (at least 2 or more) 4,000lb bombs. Why else would an intervalometer have been necessary? And would that not rule out the P2V? (perhaps Taigh can weigh in)

[airnutz]

Sorry, not the PV-2 Harpoon, but the P2V(P-2) Neptune which was good for up to 8000# load. Nice gadget 2ba..nicely intact.

[JohnB]

Wild guess and the correct timeframe...How about a Marlin?
A device like that could have been used to balance weapons drops from wing stations.

[Taigh Ramey]

It's more of a ballistic input device rather than an intervalometer and was used as a part of a WWII radar set. I am sorry that I forgot the radar set designation but I'll try and figure it out when I am back at the shop. Isn't there a data tag on it?

The RADAR operator would basically enter the ballistics for the different types of bombs along with the groundspeed and altitude which would help determine the slant range and release point in the radar. The radar would present a line on the scope and when the target would cross this line the bombs would be released usually automatically through the radar. The pilot would need to fly the aircraft right over the target or use wind corrections as determined by the RADAR/ Radar Operator.

This is a simplistic explanation of which I am solely capable.

I agree that the bombs referenced are definitely WWII as is your control box. I have a set of discs but would like to get an example of your box for the museum's collection. Should you ever decide to part with it please let me know.

[2banaviator]

It's more of a ballistic input device rather than an intervalometer and was used as a part of a WWII radar set. I am sorry that I forgot the radar set designation but I'll try and figure it out when I am back at the shop. Isn't there a data tag on it?

The RADAR operator would basically enter the ballistics for the different types of bombs along with the groundspeed and altitude which would help determine the slant range and release point in the radar. The radar would present a line on the scope and when the target would cross this line the bombs would be released usually automatically through the radar. The pilot would need to fly the aircraft right over the target or use wind corrections as determined by the RADAR/ Radar Operator.

This is a simplistic explanation of which I am solely capable.

I agree that the bombs referenced are definitely WWII as is your control box. I have a set of discs but would like to get an example of your box for the museum's collection. Should you ever decide to part with it please let me know.

Taigh, I should have just reach out to you from the start!

Your message helped me do a little bit of research, and all along I had the right document in my library (the Radar Observer Bombardment Information File ROBIF July 1945) to provide the answer. (anyone can download the pdf at Army Air Forces Collection http://aafcollection.info/items/detail.php?key=23&pkg=lx!title!!23!13!title!up!20

This module is the "Computer Box" to the AN/APS-15A Radar system, aka BTO "Bomb Through Overcast". Looks like it was used fairly widely across bombers come 1945. And, I did uncover that APS-15A was used in the Martin PBM-3C Mariner, so there's the USN link. It was probably also used in PB4Y's, but I've not confirmed that yet.

Taigh, you're the first on the list when I'm ready to part with it!

[Taigh Ramey]

Very cool. APS-15 was bouncing around in my head for this unit but so are a lot of other strange numbers so with my old age I need to check the facts so I do not spread any fake news!