Monica was an active warning system installed at the rear of Halifax(see above) and Lancaster aircraft. It depended upon aural returns to indicate the presence of aircraft astern. Unfortunately Monica was unable to differentiate between friendly and hostile aircraft and the continuous clicking over the earphones proved to be an irritant rather than a help. The Monica responses were therefore ignored, or more usually, the device was switched off.
A No. 100 Group RAF Stirling III bomber converted to carry Mandrel – a device to swamp (Jam) Freya and Würzburg radar.
I’ve always been impressed by the stories about Knickebein, Gee, Oboe, H2S, H2F, and IFF, as well as the stories about radar detectors on German submarine masts. The war was not won with 20 mm cannon and piston engines alone. I recently came across a story about the German smart bomb – the Hs 293. Konrad Zuse wrote that by the time the Germans deployed this radio guided bomb the British had deployed radio jamming on the correct frequency.
Later in the war, some Bomber Command bombers were converted to electronic counter measures and flew with the bomber stream. They used many different tactics to jam not just the radar but also night fighter control frequencies. Microphones were installed in some engine nacelles and the engine sound was broadcast from the aircraft on various frequencies.
Fake night fighter controllers were used, giving incorrect instructions to the night fighters and insisting they were the real ones and the Luftwaffe operators were the fakes (ensuring total confusion).
Tests were even done with an AWACS type aircraft using modified H2S radar, but I’m not sure if was used operationally.
The pathfinder forces used by the Luftwaffe consisted mainly of KG100, the resistance inside bomber command, by all the group commanders and Harris apparently rested on two points. One was the morale effect of the crews not included in the elite force; the other was the need for experienced crews in each squadron to mentor a rapidly expanding force. The pathfinder force was formed about a year after the Butt report laid bare how bad navigation was.
Radio navigation aids came in about 6 months earlier, in March 1942. The radio beams systems the Luftwaffe used did not have the range to reach Germany, unless the aircraft could fly at 30,000 feet, but they helped by giving the aircraft a positive fix position hundreds of miles from base, making navigation much more accurate. The problem was convincing the powers that be to expedite the deployment and to have the next device in the pipeline when the first was jammed.
The book R.V. Jones “Most Secret War
Mr Jones was called into an urgent meeting to discuss the loss of a bomber on the 13th August 1941. This bomber was fitted with one of the prototype GEE sets and was being used in the pathfinder role as an experiment. GEE was an electronic navigational and bomb aiming aid, though it is true to say it didn’t employ beams. It was far more sophisticated than that. Prior to GEE as Mr Jones explains, beam bombing as used by the Luftwaffe had been tried by British bombers against Brest.
Jones was not best pleased to find that the RAF had managed to present the enemy with a hand-built GEE set long before it could be manufactured in quantity and introduced into operations. However he devised a cover story which was fed back to the Germans. Whatever the reason, when adequate numbers of GEE sets were available from March 1942 onwards, no jamming was experienced until five months afterwards.
Jones says that Bomber Command issued strict orders in December 1943 that IFF was not to be used in any attempt to jam German nightfighters or searchlights (An urban legend which had gained great credence amongst RAF crews). The problem was that some crews continued to grasp at straws and if only two or three crews in every hundred left their IFF switched it was enough to give away the direction of the entire bomber stream, and at much further ranges than normal radar could have achieved. Probably the biggest problem was MONICA, a rear facing radar intended to warn crews of attacking fighters in their six o’clock. The problem was that the MONICA transmissions could be picked up fifty miles away and the Germans attacked from underneath with oblique mounted cannon instead of from behind.
But it wasn’t until a brand new JU 88 nightfighter with all the latest detection gear landed in the UK that it was finally made clear to everybody how dangerous any kind of sustained electronic radiation was. I guess if I’d been a bomber pilot I would have need a lot of convincing before I switched off the only device on board which could have warned me of an incoming fighter.
The use of pathfinder-type forces caused RAF’s Harris a huge quandary. Prior to the war, pathfinder forces had not been deemed necessary. With war upon GB, however, and with evidence of successful use thereof of such organizations by the Luftwaffe, some observers strongly advocated creation of similar units for the RAF. However, this “solution”, I believe, was not so clear-cut a thing for the leader of Bomber Command.
In order to create such forces, it was necessary to select crews and give them extra, expensive and time-consuming training. Inevitably, the crews selected were culled from the most capable, highly-motivated personnel available to Bomber Command. Thus, pathfinding crews “skimmed” the best and the brightest of the manpower available away from standard ops. Furthermore, the aircraft involved generally had to be modified, often at considerable extra expense and at the cost of time. Harris apparently concluded, initially, at least, that the cost to the RAF, in terms of highly-capable crews and scarce aircraft, was too high to pay. Later, under considerable pressure, he relented.
A good example of the difficulties therewith, I think, is that of 617 Sqn., which was specially formed for high-risk/high-results ops. Its results were spectacular and generally successful, but many of the men who formed this squadron already had served a tour with Bomber Command and had survived; now, they were being asked to place themselves in the mouth of the tiger once again. And losses on certain missions could be high. And how often could a leader ask such an effort from his crews? Recall that Gibson, first leader of 617, already had had a tour of operations prior to forming it up. After his service with 617, he served as a “master of ceremonies” target co-ordinator only to fail to return from one such mission. Losses of such men were undoubtedly felt not only by Harris, but also by Bomber Command crews in general.
Such electronic aids to accurate navigation and bombing as GEE and OBOE came online after Harris took command of Bomber Command. Both had limitations, but both were exploited by Bomber Command to the extent feasible. GEE was limited in its range because it was a line-of-sight device. OBOE could guarantee only a limited degree of accuracy, allowing the placement of bomb-loads within a large ellipse, albeit likely giving better results than bombing carried out via celestial navigation alone.
The RAF had a record of being progressive-minded when it came to exploiting electronics, starting with Dowding, who, it will be recalled, had given a great and early impetus to radar development in Great Britain by placing funds at the disposal of scientists and engineers toward the development of the earliest radars in that country.
The Germans, after all, possessed radar of their own, and used it to great utility during most of the conflict over the continent. Therefore I am not sure that Bomber Command had any period of “immunity” from German nightfighters during the time-period mentioned. RAF fought a massive, continuous and generally successful electronic counter-measures war against the Germans, aided handsomely by the investigations of such men as Jones into the nature of the Germans’ radar capabilities. Use of sophisticated jamming, “window”, and “spoof” raids by high-speed Mosquito Bombers were among the techniques used to frustrate the German nightfighter forces.
H2S was a revolution in radar technology. Exploiting the development of the resonant cavity magnetron, it allowed, for the first time, the generation of large amounts of electronic emissions in the so-called microwave range, from a remarkably small package. Previously, airborne radar was limited in its utility due to the long wave length and the concomitant size of the aerials needed. The returns generated by microwave radar, furthermore, allowed for superior navigation and target resolution in theory, and to some extent in practice. However, on the second mission on which H2S was used experimentally for proof-of-concept target-marking, an aircraft carrying this device was downed on its return from target-marking, near Rotterdam. The Germans promptly examined the aircraft carrying the device, and discovered that the Allies had a workable microwave radar. Steps were taken immediately to capitalize on this gift, in the form of detectors which could allow a nightfighter to locate Bomber Command aircraft actively emitting on operations.
Once the RAF realized that the Germans could home in on H2S transmissions, BC crews in due course were instructed to use H2S sparingly instead of continuously. It is clear, however, that many crews disregarded such instructions, perhaps because they considered that the functional utility of the device for navigation and attack outweighed the risk of detection and interception. In practice, short of stripping the device from all Bomber Command aircraft operating over the continent, there was precious little Harris could do to enforce his instruction on the matter of usage.
The nightfighter threat
IFF was supposed to be used only near and over Great Britain so as to allow AAA batteries and RAF nightfighters to positively discriminate between friendly aircraft and enemy. But German nightfighters, if they dared operate over Great Britain after the introduction of cavitron-fitted British nightfighters such as the Beaufighter, could exploit these emissions in a fashion similar to interceptions over the continent.
The blinding of the nighfighter radars lead to the deployment of new radars, the deployment of active radio aids on the bombers gave the nightfighters another method to track the bombers. One that the RAF could not jam. Let alone the RAF allowing the myth that the IFF set interfered with enemy radar to propagate. With the bombers flying as a stream it only needed one bomber to break silence to give the nightfighters a chance.
The capture of the Ju88G in July 1944 came as a considerable shock with its ability to home in on RAF radio transmissions. RAF radio discipline was improved dramatically, tail warning radar was removed as it was judged to be more an aid to the defences. At the same time passive radar warning devices were limited by the concentrated nature of the bomber formation, was that nightfighter coming in on you or another bomber nearby?
Oboe was in fact rather accurate, the theoretical accuracy was better than the maps allowed. The main disadvantage of Oboe was that it could control only one aircraft at a time, while GEE could be used by all bombers simultaneously. Therefore the use of Oboe practically dictated the formation of a Pathfinder Force.
On the other hand the people who developed H2S and other sophisticated navigation tools have complained that Benett’s PFF took a rather cavalier attitude towards them, often refusing to use them properly. The “boffins” apparently felt they could get more cooperation and better results from squadrons operating _outside_ the PFF!
H2S, IFF, the Monica tail-warning radar, and so on… Sometimes the danger was overstated, for example the German H2S homer was not nearly as accurate as believed. Sometimes it was underestimated, as was the case with IFF. Sometimes too the problem was properly understood and swiftly dealt with, as was the case with Monica. In other words, the record is patchy and inconsistent, but does not show that the RAF was indifferent to such considerations. It was just difficult for them to weigh benefits against risks.
In another example the Luftwaffe knew that if there was a major amount of RAF radio testing in the morning but comparatively little in the afternoon a major night raid was on, compared with a steady level of testing during the day.
The bombing of the enemy economy was very much an article of faith in the pre-war air forces, the one mission that clearly did not tie the air force to ground or sea operations. To be given the chance to prove the idea after years of thought had turned the idea into a dogma for some meant too many of the commanders had a very rigid outlook. In essence the scientists noted the bomber commanders tended to react to losses by asking for a solution, rather than looking for an edge from the start, and this was in contrast to the fighter organisations, in particular fighter command. This is a rule of thumb and did start to change during the war, you only have to look at the array of devices available in 1945, but an outlook that did contribute to the bomber commanders being less successful than they wanted, at times they were their own worst enemies.