Aircraft navigational drafting instrument

[Segedunum]

Hi

 

I found this instrument at an antiques fair, a few years back. And I wonder, what kind of aircraft would it have been used in, and the handwritten number and name on the box, is that an aircraft production number and nickname? Thank's in advance.

 

All the best

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[Lee Ragan]

I just wonder if this was used in the classrom to teach Navigators instead of being mounted in an airplane. These old arm type drafting machines take up a lot of room when you operate them, even the smaller ones. These were used before the days of a track type machine that didn't have the arm that swung out past the edge of the drafting table when you used it. I can't imagine using this thing inside an airplane, even the bag bombers and transports had cramped navigators stations. I've only seen navigators in flight using simple triangles as straight edges and dividers to plot courses. They wouldn't need to draft maps while flying.

Just my 2 cents worth. :ermm:

[Chris_B]

There were actually navigational trays in single seat fighters like the F4F, although the only photo I can find of the Wildcat's tray pulled out is in the book "At the Controls", and no evidence of this type of equipment is shown in the photo

 

However, in a large aircraft such as a B-17 or B-24, there would be ample room for the navigator to use such tools if they were compact enough...hard to get a feel for the size of the tools. The navigator had a huge list of responsibilities; I can't imagine recording landfall over the Continent or determining magnetic heading, true course, new course in an emergency, etc, without use of some tools

[Chris_B]

Oh-

 

I found an old Craigslist reference for an AN5750 drafting machine for aircraft; old link though

 

I also found this- no clue as to aircraft though

http://www.collectair.com/Good_Stuff.html

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Thank you very much, guys.

 

All the best

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[Lee Ragan]

However, in a large aircraft such as a B-17 or B-24, there would be ample room for the navigator to use such tools if they were compact enough...hard to get a feel for the size of the tools. The navigator had a huge list of responsibilities; I can't imagine recording landfall over the Continent or determining magnetic heading, true course, new course in an emergency, etc, without use of some tools

 

I agree that a Navigator used tools to do his duties, but the physical aspects of using an arm type drafting machine would seem to preclude it being used in a bomber. B-24's and B-17's didn't have as much room as you might think for use by Navs. A small navigation table and straight edges, dividers and hand held navigation instruments were about all the room he would have.

[Chris_B]

I agree they are cramped. I've sat at the nav table in a B-17. But the size of the instruments in the pic is not clear to me so I cannot say if they are too large

[Steindaddie]

Hopefully this helps: I showed the pics to my dad (a WW2 Navy pilot) and he said this drafting machine was usually called a "PMP" - Parallel Motion Protractor. He flew PBY Catalinas 1942-44 and says they had one just like it in his aircraft.

[Segedunum]

Hopefully this helps: I showed the pics to my dad (a WW2 Navy pilot) and he said this drafting machine was usually called a "PMP" - Parallel Motion Protractor. He flew PBY Catalinas 1942-44 and says they had one just like it in his aircraft.

 

Thank you very much, and thank your dad, from me. I really appreciate the help.

 

All the best

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[Salvage Sailor]

Hopefully this helps: I showed the pics to my dad (a WW2 Navy pilot) and he said this drafting machine was usually called a "PMP" - Parallel Motion Protractor. He flew PBY Catalinas 1942-44 and says they had one just like it in his aircraft.

 

Absolutely correct,

 

This is a PMP arm (parallel motion protractor) used to lay out courses on a large chart. It is the same type of arm used by the USN on the DRT (Dead Reckoning Tracer) aboard ships in CIC and in the pilot house chart-table by the quartermasters. The only difference would be the ruler. The air ruler is set up for long range/speed gradations whereas the naval ruler is set up at 2000 yd intervals (nautical miles).

 

There ya go.....