WW2 Radar Calibration Devices - we have an answer.....

[Ed Russell]

What I thought were "radar reflectors" on this Avro Rota from 5 RMU are actually supports for a Heath Robinson-like cable set-up.



There are tripod structures on the front u/c leg, both tail fins and just below the rotor housing. There is a more elaborate structure on the tail. A cable runs between various points via what look like pulleys.

Even though the Flight was called 5 Radio Maintenance Unit I am fairly sure that this was a covert designation for a radar calibration unit.

Any ideas welcome...........

My build is progressing here

http://www.britmodeller.com/forums/index.php?/topic/234999409-avro-rota-529-radar-calibration-sqn-5-rmu-1448-rc-flt/

[GordonM]

Are you sure that's from 5 RMU? In Action Stations Revisited Volume 1 on page 183, Michael Bowyer has the same photo captioned as being a C30a from 74 Signals Wing based at RAF Duxford.

[Phil Evans]

They look like they might be insulators rather than pulleys

[GordonM]

They look like they might be insulators rather than pulleys

possibly Radio aerials then? I suppose on such a short fuselage it would make sense that an aerial would need an indirect route to provide sufficient length?

[Ed Russell]

The photo caption in The Aeroplane has it as 5 RMU and later 529 Sqn. Insulators is quite reasonable but a radio mast (like a contemporary single seat fighter) would be more likely if it was just an aerial.

[Phil Evans]

The reason I thought of insulators was because it reminded me of the sort of installation on a Gladiator, but reversed. Now I'm wondering if there is some sort of vertical frame on the centreline and the antenna/reflectors might form a diamond shape with the tips of the tail.

EDIT. I think I'm wrong about the setup as the angles don't look right (that's as I've just finished a night shift). Possibly an antenna running longitudinally from the tip of the tail structure to the cockpit and another from the tail tip to the upper tripod. That still leaves the lower tripod as a mystery as I can't see any connection to it. More guesswork and perhaps the lower tripod was the original fitting and the upper one replaced it?

Edited April 18, 2016 by Phil Evans

[Ed Russell]

In the best traditions of Britmodeller I have scrawled the positions of the tripods, insulators and cables.

A are on the tailplane ends and B is on the central fin. There is one line running from D downward and forward at 45 degrees which I cannot see an end for. it would be nice to think it joined another tripod on the opposite side undercarriage struts but there isn't one there.

Somewhere there is a simpla answer to all this............

[Garry c]

When I blow up the photo;

To me it looks like tripod D goes to the side,not to the rear.

Dotted line D goes into the fuselage at the end of the panel just behind the engine, just below the line where the upper and lower cammo meet.

Tripod C has a small egg shaped object on top.

NO idea what any of it means.

Good Luck

Garry c

[OneEighthBit]

Dunno if this helps but I adjusted the image levels a bit to bring out the wires.

[Phil Evans]

If you Google "Royal Air Force Rota" the second image is a bit clearer version of this one. You'd think that there would be more images available as this seems like a high quality shot rather than someone's personal photo. Is it one of a sequence?

[mhaselden]

Going to throw in some pseudo-plausible suggestions about this bird...feel free to dismiss my ill-informed ramblings.

Firstly, the aerial installation probably has nothing to do with radar - I don't see the Rota intercepting the radar transmissions and doing anything with them. The Rota was the target and so just needed to present a decent radar cross-section to be detected...and the whopping great rotor, radial engine and prop provide those nice big radar reflectors.

My suspicion is that we're seeing an improved comms system to provide more accurate D/F location of the Rota aircraft. In order to calibrate the accuracy of the ground-based radars, you'd need to know where the target was located with a fair degree of precision and accuracy. In 1940, radio D/F was probably the best way to do that, but ordinary aerial installations may lack the required precision and accuracy, hence we have 3 long aerial wires on the Rota forming a triangle, with the base running across the tail.

Of course the above could be pure effluent...but it's the best explanation up with which I can come.

Cheers,
Mark

Edited April 19, 2016 by mhaselden

[Ed Russell]

To me it looks like tripod D goes to the side,not to the rear.

Dotted line D goes into the fuselage

Tripod C has a small egg shaped object on top.

Garry c

Indeed this tripod points abeam - it's my crap drawing if it looks otherwise!

When I look closely, dotted line D is fictional, the (now) green line could end somewhere on fuselage - the white line following it down may be more of it

You are right - there's an egg there. (Edit - On closer inspection and further thought, it's quite likely a wind-driven generator, just out of the propeller arc.)

My suspicion is that we're seeing an improved comms system ......... hence we have 3 long aerial wires on the Rota forming a triangle, with the base running across the tail.

That's as good a suggestion as I have seen yet.

So here is an updated diagram...........

Thanks guys.

[Ed Russell]

I have acquired a book - Les autogires La Cierva - which has a much clearer picture and confirms Mark's theory above that the rig is a radio array. it says Good communications were the fundamental feature of these aircraft when used for calibrating radar installations.

it is a fascinating book, answering all questions about Ciervas. Who would have thought the RAN used them to search for torpedoes after firing practice?

[GordonM]

I have acquired a book - Les autogires La Cierva - which has a much clearer picture and confirms Mark's theory above that the rig is a radio array. it says Good communications were the fundamental feature of these aircraft when used for calibrating radar installations.

it is a fascinating book, answering all questions about Ciervas. Who would have thought the RAN used them to search for torpedoes after firing practice?

Conjures up mental picture of Junior Rating being sent to round Aussie beachside houses going "please sir can we have our torpedo back, please?"

[mhaselden]

I have acquired a book - Les autogires La Cierva - which has a much clearer picture and confirms Mark's theory above that the rig is a radio array. it says Good communications were the fundamental feature of these aircraft when used for calibrating radar installations.

it is a fascinating book, answering all questions about Ciervas. Who would have thought the RAN used them to search for torpedoes after firing practice?

Wow! I got something right!

[TonyTiger66]

Now I really have to get that book!

A secret obsession of mine; the Autogiro.

 

I had no idea the RAN used them  !

 

Great information in this thread  

 

TonyT