Blenheim IF Night fighters - 2018 model BQ-W

[Robert A]

Just a couple of quick questions on this subject.

How many crew flew in the nightfighter Blenheims? and, who operated the AI?

I seem to remember seeing a pic og the AI equipment in the rear fuselage just behind the turret, can't remember where, doh! so does this mean the Gunner also worked the AI and directed the pilot thereby making the navigator surplus to requirements?

I'm thinking of doing my Frog Mk1 as a 406 Squadron a/c from RAF Acklington

TIA,

Bob

Edited August 19, 2011 by Robert A

[DCRanger]

I seem to remember seeing a pic og the AI equipment in the rear fuselage just behind the turret, can't remember where, doh! so does this mean the Gunner also worked the AI and directed the pilot thereby making the navigator surplus to requirements?

I'm pretty sure that the AI set sat on the shelf behind the observer(AI operator).

[Seahawk]

I seem to remember seeing a pic og the AI equipment in the rear fuselage just behind the turret, can't remember where, doh! so does this mean the Gunner also worked the AI and directed the pilot thereby making the navigator surplus to requirements?

My instinctive response to the question, based I think on a photo I've seen, is that the set was in the fuselage forward of the turret with the ex-gunner AI operator facing forward. There might just be room there to squeeze in a trainee operator as well. But I may be totally wrong. Superb book though it is, Rawnsley's "Night Fighter" isn't great on technical detail but it might well contain in incidental details incontrovertible evidence of such things as whether the AI Operator was in the fuselage or in the cockpit or sat facing forward or aft. I agree with you that a navigator would seem de trop.

[AWFK10]

I think there's a photo of one in the Graham Warner tome on the Blenheim.

Not in the first edition, as far as I can see - perhaps in the second one, though? There is a photo of Bristol's development airframe, K7072 (a Mk IV) with the turret replaced by a small observation cupola. The book confirms M J F Bowyer's reference to the order for the turret to be removed from aircraft in four squadrons but says 'One hundred conversion sets were ordered but by the time they began to appear at the squadrons at the close of 1940 the Blenheim was nearing the end of its longer-than-expected career as an "interim fighter"'. However, whenever the crew of Blenheim nightfighters are named in the section of the book dealing with the latter part of 1940, there are only two of them - this includes the names of fatalities resulting from aircraft losses, which you'ld certainly expect to include everyone on board.

The only illustration I ever recall seeing of a turretless Blenheim If is a sketch showing the armament and radar layout in Bill Gunston's nightfighter book of the mid 1970s.

[Nick Millman]

The operator occupied an improvised position in the fuselage forward of the turret location, facing front and kneeling on a 'pad' of folded blankets on the floor.

Regards

Nick

[Robert A]

Thanks guys.

Nick, does that mean the navigator was surplus to requirements?

[DCRanger]

Thanks guys.

Nick, does that mean the navigator was surplus to requirements?

It was the gunner who became redundant. The navigator in the early part of the war is more correctly referred to as the observer who combined the job of navigator and bomb aimer. (The fighter version of the Blenheim could carry a small load of 40lb bombs on external racks in addition to the gun pack). Later the observer's brevet was replaced with a navigator's brevet which was also worn by AI operators in night fighters.

Edited August 20, 2011 by DCRanger

[Nick Millman]

Who did what in the early Blenheim nightfighters can be a little confusing. Chisholm (in 'Cover of Darkness') recalls flying a 604 Sqn AI equipped Blenheim with "a gunner in the turret" and an observer monitoring the radar equipment. Braham (in 'Scramble') mentions the "gunner" declaring the AI equipment unserviceable and clambering forward to sit beside him for the rest of the flight. Ian White's tome on the History of Air Intercept Radar & the British Nightfighter doesn't say much about the crew positions but does include a fascinating description of the Blenheim cockpit from a pilot and a good account of how the radar operators were subsequently selected and trained.

Rawnsley mentions the turrets being removed and says that the gunners were given a choice - to be posted away as gunners to some other unit or to remain with the squadron and learn to become radar operators.

One of them, I can't remember who and can't find it now, mentioned that at one stage there were more operators than aircraft so pilots had a choice who they flew with.

Edited August 20, 2011 by Nick Millman

[Robert A]

Thanks DC and Nick,

I was going to do it in flight but as there's no definitive answer on this I'll just do the a/c on the ground with no crew on board.

One of the guys who goes to my local hobby shop also mentioned that he'd been led to believe that the navigator sat in the central well between the wing spars using the AI and the gunner manned his turret as normal.

So it's all a bit confusing, which may be quite understandable as it was all quite new and maybe different squadrons tried numerous different ideas as they developed their tactics etc...

Oh well, Many Thanks anyway,

Bob

Edited August 22, 2011 by Robert A

[Adam Maas]

A gain of 80mph seems a considerable overstatement: if a Blenheim could go that fast there'd have been no need for Mosquitos. I don't recall seeing numbers like that mentioned even for the more comprehensive Cotton PR conversion. It may be a mishearing of 18mph, although perhaps a little more would be hoped for!

Note that even if it was a 80mph gain, that still would have left the Bleinheim much slower than a Mosquito. 80mph would have given a top speed around 320mph for the Bleinheim, which is 80-100mph slower than a Mosquito at altitude (the NF.30 was the fastest, 424mph at 30,000 ). Based on the testing provided, it sounds more like a misheard or mispoken quote that was supposed to say that speeds up to 280mph were achieved.

[Test Graham]

The Mk.I bomber Blenheim was credited with 285mph (must have been a good one) so had the 80mph been true then removing the turret would give a speed of some 360 mph. Comparisons must be fair: in the late thirties, no-one was imagining a high-altitude two-stage night fighter. DH were claiming, on very little relevant experience, an unarmed bomber promising up to 400mph. 40mph (or 10%) would not have been enough to justify the effort on design and development of a any new type, with the effort needed to get it into production. I was illustrating the point that the 80mph for removing the turret was an obvious nonsense, not suggesting that the Mosquito was anything other than a genuine improvement.

[gruffy]

I'm pretty sure that the AI set sat on the shelf behind the observer(AI operator).

According to Graham Warners book- the Bristol Blenheim, P239 , "Faced aft to opperate the Al Mk III set installed in the fuselage 'well' behind the the cockpit between the main spars"

Edited August 23, 2011 by gruffy

[Ed Russell]

the 80mph for removing the turret was an obvious nonsense

Earlier on in the chapter I quoted above, it says "the removal of turrets should result in an 8-10 mph gain" - I wonder if that transmuted into 80 mph?

As far as crews go, the part of the 604 ORB I have seen lists crews as 1, 2 or 3 persons. I think I know why but I'll do a bit more ORB analysis and check.

I think 1=just pilot (for mechanical checks etc and as AI target) 2=pilot and gunner (no AI fitted) OR pilot and AI operator (no turret if operational mission or no turret gunner if AI check) and 3=pilot, gunner and AI operator (AI and turret fitted).

Someone pointed out to me that if the number of pictures was a measure, the vast majority, if not all, had turrets. On the other hand there are very few 1940-41 pictures of AI fitted ones at all. These aircraft were state of the art, top secret at the time so pictures were probably discouraged.

[DCRanger]

According to Graham Warners book- the Bristol Blenheim, P239 , "Faced aft to opperate the Al Mk III set installed in the fuselage 'well' behind the the cockpit between the main spars"

This photo of the AI set in a Blenheim was published in Flypast February 2007. The caption says it was mounted in the fuselage well behind the observer. Until now I had always taken that to be the space immediately behind the observers seat but in front of the bulk head. I thought that was awkard enough but for the operators of six squadrons that spent the winter nights of 1940/41 the arrival Beau's must have been a great relief. Presumably when the gunners were made redundant the observer also had the task of operating the radio which I believe was usually located behind the gun turret. Surely that was relocated to somewhere more convenient unless the nightfighters were also fitted with VHF radios?

[mhaselden]

Great pic. Love the high-quality modular systems rack (aka plywood and a couple of wooden joists) used to hold the kit in place. Necessity is the father of invention?

Incidentally, was the pic of a MkI or a MkIV? I presume the former, since that's what the thread is about, but I'm just trying to be sure.

Cheers,

Mark

[Test Graham]

The initial batch of sets arrived without any parts for the installation in the aircraft, but these were earlier than the Mk.III. Possibly the photo is miscaptioned? I repeat my recommendation in post 10: the book has several chapters on the early AI and its fitting in the Blenheims.

[Nick Millman]

The initial batch of sets arrived without any parts for the installation in the aircraft, but these were earlier than the Mk.III. Possibly the photo is miscaptioned? I repeat my recommendation in post 10: the book has several chapters on the early AI and its fitting in the Blenheims.

Seconded.

[DCRanger]

Great pic. Love the high-quality modular systems rack (aka plywood and a couple of wooden joists) used to hold the kit in place. Necessity is the father of invention?

Incidentally, was the pic of a MkI or a MkIV? I presume the former, since that's what the thread is about, but I'm just trying to be sure.

Cheers,

Mark

The caption doesn't specify but I have always assumed it is a MKI as that is the main focus of the article (but again, perhaps wrongly?). It does say that the set is a MKIII set and the box on the right is the power pack.That raises another question (apologies if this is thread drift) but with the extra space in the nose of the MKIV and no need for navigation charts would the AI set be in a different location?

[Test Graham]

The aerials were designed around the Mk.I, which caused some problems, but after solving those the first aircraft delivered were Mk.IVs. These things happen. The set was intially placed in the nose but Dowding was furious because he saw the lights as as a problem. Some items had to remain near the aerials in the nose but the main set was moved to the centre of the aircraft.

The picture may show a Mk.III set replacing an earlier one in an early aircraft, or it maybe that the installation fix became standard - after all, it worked, didn't it?

Edit: for an earlier posting: the AI radar interfered with HF, so the nightfighters went to VHF radio. This was happening in Fighter Command anyway.

Edited August 24, 2011 by Graham Boak

[Nick Millman]

The caption doesn't specify but I have always assumed it is a MKI as that is the main focus of the article (but again, perhaps wrongly?). It does say that the set is a MKIII set and the box on the right is the power pack.That raises another question (apologies if this is thread drift) but with the extra space in the nose of the MKIV and no need for navigation charts would the AI set be in a different location?

The first set to be used successfully was the ARI 5003 (Airborne interception Radar Mk IV) with the Mk III produced from late 1939 only used for training according to one source. The Mk III equipment consisted of a receiver, transmitter and an indicator. I suppose the mid-fuselage location in a Blenheim would be determined by weight considerations?

There were test versions of the Mk IV, TS 36 and TS 127, which I suspect might have been used in the early Blenheim radar ops (?) but the equipment was more complex consisting of receiver, transmitter, indicator unit, modulator, voltage control panel and impedance matching unit.

I doubt very much that the operator faced aft because the obvious and easiest location to secure the somewhat bulky equipment would be against the central wing spar assembly otherwise it would impede the rear fuselage and top hatch.

[Ed Russell]

I repeat my recommendation in post 10: the book has several chapters on the early AI and its fitting in the Blenheims.

I have to agree with your recommendation, and indeed, I acted on it. It's a most interesting, if a little dry, account of the radar war. Obviously, they couldn't find pictures either, so they illustrated it with the next best thing.

Note not only the lack of turret but the position of the azimuth unipole compared to the Squadron book, where it is represented by a disc on the cooling gill - this picture looks like the cooling gill has a cut-out to avoid hitting the aerial

[Selwyn]

I have to agree with your recommendation, and indeed, I acted on it. It's a most interesting, if a little dry, account of the radar war. Obviously, they couldn't find pictures either, so they illustrated it with the next best thing.

Note not only the lack of turret but the position of the azimuth unipole compared to the Squadron book, where it is represented by a disc on the cooling gill - this picture looks like the cooling gill has a cut-out to avoid hitting the aerial

Forgive me if this appears a silly question, but am I right in assuming that the arials as depicted are repeated on the other wing/ power egg?

Selwyn

[DCRanger]

Forgive me if this appears a silly question, but am I right in assuming that the arials as depicted are repeated on the other wing/ power egg?

Selwyn

For the MKIII AI set they are as shown with no antenna on the starboard wing.

[brewerjerry]

Hi

Found this thought it maybe of interest.

Osprey Blenheim squadrons of WW2 by John Lake

...... At the RAE, L1290 was tested with various mid upper turret and ring gun configerations,and this led to fighter command eventually deciding ( on 2nd october 1940 ) to replace the blenheim fighters heavy turret with plywood fairings.....

..... On 2nd october fighter command ordered that the 64 aircraft equipping its four blenheim If squadrons should be modified, purchasing 100 modification kits, 604 squadron began modifying its aircraft that month with 25, 219 & 604 following suit..

It doesn't mention if any IVf nightfighters were converted.

Cheers

Jerry

I have to agree with your recommendation, and indeed, I acted on it. It's a most interesting, if a little dry, account of the radar war. Obviously, they couldn't find pictures either, so they illustrated it with the next best thing.

Note not only the lack of turret but the position of the azimuth unipole compared to the Squadron book, where it is represented by a disc on the cooling gill - this picture looks like the cooling gill has a cut-out to avoid hittin the aerial

Hi

Many thanks for posting the diagram very interesting.

Cheers

Jerry

Edited August 26, 2011 by brewerjerry

[brewerjerry]

Hi

not a night fighter and in canada but came across this whislt browsing

cheers

Jerry

http://www.learning-to-fly.com/images/Bristol-Blenheim.jpg