My memory is stirring – way back in early 60’s in the Weybridge D.O. drawings would have a side column where drawing changes were listed in a shorthand note, say ‘Dim 1.23 was …’ and the drawing issue would be raised – some times the issue would be a superscript P followed by a letter. At some defined time the drawings would be frozen & issues would change to numeric & any further changes would be the subject of a Modification committee & if agreed would be assigned a number. This number would then be listed in the change column & the drawing changed to reflect the mod. The committee would also agree as to which aircraft would be affected on the production line. The modification would be described & noted for reference, but back then not sure how that was done before the aircraft entered service, probably in the Committee meeting minutes, although there should be a register listing the mods somewhere.
In service mods would again be analysed by a mods committee & a Modification leaflet created, it would also be decided if it was to be incorporated by Service, manufacturer, or working party. If still in production then assigned aircraft would carry that mod.
Thats my memory – could be faulty at my age!

Back on topic!
Photos taken at Deer Valley 1977 where my father re-assembled her after disassembly at Blackbushe.

AndyY, the reason I surmised that the dial had been overpainted is that there is paint in the countersink & the screw slots, which I would not expect to see on a pre manufactured dial.
As for static use, say in a wind tunnel, then surely U tubes would be a better device, not very practical for use in flight testing.

Doesn’t look like a Pobjoy, no cooling fins…what about a Douglas twin or a Cherub?

Sounds as if the patient suffered from locking wire rash……

G-info confirms IGU with Universal until ’66, but OCR was sold to Jersey late ’59. Both stared out as 5D’s but do not know when converted to Gipsy Majors, certainly were Gipsys when I flew them.
Keith

I must admit that I’m having a problem fully understanding how the prop angle is balanced if its not on the stops. when I flew with my father in his Proctor (many, many years ago), he of course took off in fully fine pitch in order to get the best acceleration, but once airborne would bring both the throttle & pitch control back to about 70% to achieve cruise speed, so presumably the prop was ‘floating’ between fine & coarse in order to keep a constant rpm via the csu, not necessarily a constant airspeed? I only ever flew fixed pitch jobs, so could not experiment myself, but I did get my father to go to full coarse in flight when at full throttle – rpm went from 2400+ down to about 1900, but he didn’t leave it there long enough to see if speed increased or decreased.
Now when you are saying that drag increased depending on blade angle, this presumably can be affected by blade planform & centre of pressure position relative to the blade rotation (radial) axis – if thats wrong then increased or reduced drag can result……ohh it gets very complex.
All I know about props is messing about with curves in Flight Sim 2004 to get J near a reasonable value for HP & airframe drag – presumably the fixed software caters for the rest in theory!
Think I should stop now before I dig a big hole for myself, but thank you for your explanation, & I will go & try Wiki-ing!
Keith

I would say its a ‘M’ you can see the break of the stencil between the last vertical stroke of the M & the bit of the V, then there is just the top of the first stroke of the M peeping above the tailplane.
Keith