WWII Air Ministry A.M. PILOTS Knee Pad Navigational COMPUTOR Mk 3 D. R.A.F 1940

**Danger** · 04-19-2019, 05:03 AM

Hey guys,

I just got this R.A.F Navigational Computor MK III D REF No.6B/180.
It's a bit rough, but it's perfect to me.

I've read that models A,B,C and D were made to strap on the leg. A&B was for slow speeds, C&D for higher speeds. In each case the first (A & C) were based on an isothermal model of atmosphere and the second (B & D) on an ICAN atmosphere.

Model F was made without a strap but with some scales on the reverse and made to stand alone on the chart table.

Models G & H do not appear in my 1944 RAF manual of navigation so there is a slight pointer to date. H appears to be stand alone on chart table for ICAN atmosphere - I presume G is for Isothermal Atmosphere.

The * indicates that the circular scale is rotated by grasping it. In the original Mk III the scale was rotated by a knob at the side but this probably proved too complicated.

The calculations based on altitude use standard atmospheres. The Isothermal atmosphere assumes that there is no change in temperature with altitude (not sure why, because it clearly does change). The ICAN atmosphere specifies a standard drop in temperature per 1000ft. ICAN is International Commission for Aerial Navigation.

Cheers,

Danger

**RMD** · 04-19-2019, 05:31 AM

Wow, a fascinating, and beautiful piece of preserved history.

Thanks' for posting this.

Take care.

**kradman** · 04-19-2019, 06:16 AM

Nice that it has still the straps normally you find these with them cut off

**reneblacky** · 04-19-2019, 06:22 AM

Cheers for showing, fantastic piece!
Here's the Australian RAAF equivalent I have, not so nice as yours though.

**RMD** · 04-19-2019, 07:07 AM

This one is cool as well

**Danger** · 04-24-2019, 12:14 PM

Thanks guys,

Does anyone know how the green bar works?
I used to have lots a few years ago, then it went down to 2 bars.
Then after posting this thread I got a notification which I didn’t understand and
Now I’m down to 1?

**reneblacky** · 04-25-2019, 04:13 AM

by Danger

Thanks guys,

Does anyone know how the green bar works?
I used to have lots a few years ago, then it went down to 2 bars.
Then after posting this thread I got a notification which I didn’t understand and
Now I’m down to 1?

If you don't post for some time they deplete