Angle of Ascent/Descent instrument

[HP52]

I acquired this somewhere, probably from my Father. It measures from 20Deg Ascent to 20Deg Descent.

The only clue is at the apex there is a
Crown
R.A.AF.
66A/389
There may be a mark on the Portside in the fwd web (viewed from aft).

My first time here - this looks like WW2 disposal stuff common in the 1960's.

To me it looks like something you would expect on an airship or submarine.

Appreciate any suggestions as to what it came from (wild thinking) would be a WW1 Blimp with a DH4 fuselage hung from a balloon in UK like at Carew Cheriton (Great little Museum BTWay)


Geoff Raebel - Australia

 

[Snautzer01]

Air Ministry Inclinometer Reference 6A/389

Officially called a 'Fore-and-Aft Level, Type B' these were first described in the 1934 edition of AP1275. The type 'B' variant superseded the Type 'A' which was used on RNAS ai...

www.oldnautibits.com

 

[Bretoal2]

"gave a visual indication of the angle of the aircraft through the air".... Really ?

 

[HP52]

Thanks Snautzer, looks like you have it identified. Mine does have a chamfered edge around the bezel.
I might stick it in the Foxbat and see whether I can blindly hold S&L with it + the Balance ball. It will need an adjuster to set the longitudinal trim to neutral.
I'll come back when The Oaks dries out and I can get airborne again
HP52

 

[HP52]

"gave a visual indication of the angle of the aircraft through the air".... Really ?

I'll try it out in the next few weeks (with a look out passenger) it looks doable. Mine varies from the picture, having a 45 Deg chamfer all around the bezel except around the two middle (adjusting screw - starboard side only - I don't understand the adjuster but could be some sort of fine Fore&Aft but I don't think so.
Hampdemon

 

[Bretoal2]

I'll try it out in the next few weeks (with a look out passenger) it looks doable. Mine varies from the picture, having a 45 Deg chamfer all around the bezel except around the two middle (adjusting screw - starboard side only - I don't understand the adjuster but could be some sort of fine Fore&Aft but I don't think so.
Hampdemon

I just wanted to say that the definition of this instrument's use is wrong.

Such a system, which is in fact similar to a spirit level, can only give the angle of the plane in relation to the true horizontal, and not the angle of the aircraft in the air , which is defined as the angle of attack, or incidence. For the same position relative to the horizontal, depending on whether the trajectory of the aircraft is ascending, stabilized in level or descending, the angle of attack (= angle of the cell relative to the air, or = incidence of wing profile) can be completely different.

 

[Jed]

Also used in the Hotspur Glider for note. As Bretoal2 mentioned, its just a spirit level that effectively shows how level the aircraft is.

Sorry for the shoddy photos, was trying to do this one handed, uphill with a tailwind.

 

[Reegor]

Wow, using this would be taking your life in your hands. It's got no gyro at all, so the angle shown is angle (relative to vertical) + effects of acceleration. Which will be all over the place if there is any turbulence.

 

[HP52]

Wow, using this would be taking your life in your hands. It's got no gyro at all, so the angle shown is angle (relative to vertical) + effects of acceleration. Which will be all over the place if there is any turbulence.

In the bag of stoneage aircraft instruments - most will have seen the Y sights used by the Dambusters - 455 Squadron (Hampden) and later 144 Sqn( Beaufighter) used the hand held Y sight for torpedo dropping. Hamdemon