Fortress Aerials

FK209

Have since learned that FK209 is known to have been shot down on March 23, 1943, while serving with with 59 Squadron.

Fortress Aerials

Technical indeed! Means nothing to me but I agree: the upper wires are for R/T and I would deduce are for an HF command radio, the VHF command radio and associated aerial coming along a little later. I’m still stumped on side wire aerial but maybe this is part of the HF system too with the upper wires for tranmission and the side wires for receiving… thanks for all you input.

A Google search has turned up some information on Sterba arrays at: http://www.qsl.net/we6w/projects/Sterba_ant.txt

Although, of course, rather technical it seems fairly clear that a Sterba array is indeed the dipoles seen down the side of the fuselage of your Fortress. I am therefore certain that the dorsal aerial has to be a normal HF or VHF R/T aerial, rather than anything to do with ASV or other radar equipment.

There is only one Fortress photo in Boffin, which I’m fairly certain is an IWM photo. It is a nose shot, but doesn’t really show very much.

I must confess, even though I’ve met Robert Hanbury Brown a couple of time, I’ve never heard of a Sterba array before. It sounds as though they were the dipoles in your photo, but the description of them being 12 feet long suggests something else. I’ll see what I can find out and get back to you.

Fortress Aerials

Thanks, Ian. Any reference to ASV arrays for the Fortress in the book? In the meantime will try and find a copy. Assume the Sterba arrays are the rigid rods in the second photo I posted. Which brings us back to the wire aerials in the first photo… which I’m again thinking were not ASV-related.

I stand corrected! 😮 Having checked Robert Hanbury Brown’s autobiography, ‘Boffin’ I note the following: in early 1941 Coastal Command were alredy operating 110 aircraft fitted with ASV Mark II, 60 of them with simple forward-looking aerials and 50 with high-gain sideways-looking aerials (LRASV).

He also notes earlier on: the first thing I did when I returned to St Athan was to design a sideways-looking aerial array for the Whitley. From an aerial designer’s point of view nothing could habe been nicer; the Whitley had a long box-like fuselage which was ideal for mounting an aerial array. As a transmitter aerial we fitted an array of 10 half-wave dipoles on 5 kingposts mounted in a line 18 feet long down the centre of the fuselage like the backbone of a fish. For receiving aerials we mounted to Sterba arrays, one on each of the flat sides of the fuselage; each Sterba array was about 12 feet long. The overall power gain of the two aerials combined was about 50 which increased the range of the ASV by about 2.5 times; it could then detect coastlines at about 60 miles, ships of 10,000 tons at about 40 miles and surfaced submarines at 10-15 miles. We called this installation long range ASV (LRASV).

As I said previously, airborne radar isn’t really my thing and I’ve not done any primary research on this, so my apologies for getting it wrong!

Fortress Aerials

I can see this is going to take as few exchanges to sort out! Thanks for your reply. Have attached a later photograph showing the defintive rod fuselage aerials to which I referred. These did use the fuselage skin as a reflector for transmitting and receiving for LRASV. The underwing aerials were the receivers for the forward-looking looking comonent, the tranmission aerial for which was in the nose cone on the Fortress. One Fortress IIA was fitted with the dorsal transmission masts for trials at the RAE but these were discarded in favour of the dual-purpose aerials in this photo. My understanding is that LRASV was simply a switchable, sideways-looking enhancement of ASV II (by switichable I mean the operator could only select forward- or sideways-looking). How are we doing so far?

The dipole aerials which can be seen on the side of the fuselage certainly look identical to those of ASV II I have in several photos. I’m dubious that the aircraft’s skin would be used as a reflector; it would be more likely that a reflector aerial (such as those in a Yagi) would be used where needed.

These dipoles down the fuselage side were the transmitting aerials. Yagi type under the wings or on the nose would have been the receiving aerials.

It is important to recognise that there is a difference between ASV II and LR-ASV. The latter had large dorsal masts, leading to the aircraft being nick-named sticklebacks. This would be what you describe for the Liberator, Whitley and Wellington, but is NOT ASV II!

Fortress Aerials

Thanks, you two.

My understanding is that the definitive sideways-looking Long Range component of ASV II radar used rod-type dipole aerials to receive and transmit using the aircraft’s skin as a reflector – eight of these were mounted on each side of the rear fuselage in two rows of four some time after the first Fortress IIAs were delivered to the UK. But is it possible that these wire aerials could be an early configuation for ASV II? My feeling too was that the upper wires were for R/T but early versions of ASV II had separate aerials for the tranmit and receive functions so the upper wires could be an early form of tranmission aerial. They seem to have insulators at regular intervals suggesting they are segmented in some way. Other types like the Liberator I, Whitley and Wellington were fitted with tall masts with four sets of rods for the transmission function.

Yes, it is FK209, phtographed at Dorval prior to delivery. However, it only served with 59 Squadron from Chivenor. It was lost without trace while with 59 Squadron on March 23, 1943.

This Fortress 2A is FK209, alias 41-9203, of RAF 220 Sq. It crashed nr Ballykelly and repaired then was MIA 25/3/43.
It had ASV radar search attenae above the nose and under both wings. Whether the other two sets of aerials were ASV or not – I don’t know – sorry!
Regards
Skipper

I don’t know about the dorsal aerial (which might be R/T?) but the dipoles down the side of the fuselage look awfully like ASV to me. These would be the transmitting aerials of a sideways-looking system. Airborne radar isn’t my speciality, and I stand to be corrected, but I’m fairly sure that’s what these aerials were.