Blenheim Aerial Survey

Being a big Blenheim fan I noted variances in aerial fit which none of the published side views or scale plans appear to portray correctly. Something else these side views and drawings tend to overlook is the presence of IFF aerials.

The problem with aerial wires is that being just a thin steel wire (anyone know what dia these actually were?) they hardly show up on photographs, the only give-aways that they are actually there being the aerial masts and the insulators.

Having studied dozens and dozens of photographs in various books I concluded there were two major variations which I have tried to represent graphically in the below drawings. Note I am focusing on the Mk IV Blenheim.

The differences between A & B are the shape of the mast itself (straight broomstick type or tapered) and the presence of a fairing protecting the aerial lead-in point in the fuselage.

The second variation is where the tapered mast gets a bulge on top. From most photos it is impossible to make out what this bulge is but some time ago I was pointed to a website dedicated to 404 Sqdn (http://www.404squadron.com), the photo album on which contains several shots of Blenheim air- and groundcrew. Though intended as portraits some of these photos have been composed in such a way as to reveal a wealth of airframe details!

Photo PL07692 shows that the bulge on the mast is in fact a two part pressed alloy fairing but what is it for? It doesn’t seem to be there to cover the aerial attachment which is at the back of the mast, the fairing only covering the front.

PL07699 shows the “secondary aerial” that I depicted in red on the drawings, photo PL07716 then shows how this attached to the starboard tailplane. So far this is the only photo I found depicting such a long secondary aerial, all others seem to have the shorter version as in C.

As for the IFF aerials, from various photos (mostly taken by airgunners from their turret hence rather unsharp) it was clear that this attached to the underside of the tailplane tips (unlike on the Spitfire which has an attachment on the tailplane leading edge) and then 404 Sqdn came to the rescue again with photo PL07705, on which one can see a wingnut below the tailplane tip!

Originally the Blenheim was fitted with a T1083/R1082 transmitter/receiver which by 1941 were replaced by the T1154/R1155 set. A TR9 radio set was then also fitted for use by the pilot and which permitted voice communication as opposed to morse.

What I now would like to know is if that secondary aerial would point to the aircraft being fitted with the TR9 set and what that bulge fairing on the aerial mast is for! The Air Publication Vol I that I have for the Mk IV does not give any info on radio installation, unlike the Vol I’s for other aircraft I have.

Answers or just ideas would be much appreciated!
Cheers,
Walter