P-51 fuselage fuel tank

[MiTasol]

Congratulations. An excellent simple explanation.

I had been trying to write something that described the operation as simply and clearly and just could not do it.

 

[Engineman]

Congratulations. An excellent simple explanation.

I had been trying to write something that described the operation as simply and clearly and just could not do it.

Thanks. This is quite a complex subject, one that made aircraft designers bald, I think! The same concept positive G "balance weight" was fitted to all Bf 109 E/F/G/K to modify handling feel under G loads, only it was a much smaller weight, maybe 1/10th, just 1 or 2lb. It might have been in earlier 109's as well, and other aircraft. I showed the large glass one from a Ju 388 in my parts quiz, although that probably functioned more as a load limiter.

Eng

 

[MIflyer]

On the early Ercoupes they put a bungee cord attached so that you could turn a crank and add pull force to the elevator. So you were trimming the control linkage rather than the elevator. It eventually was replaced with a more conventional trim tab on the elevator.

 

[Reluctant Poster]

Really? I would not have thought there would be enough room.

The US developed a new, UHF, much more sophisticated IFF, the BC-645, that had all kinds of features including the ability of aircraft to interrogate each other. But the British refused to change and you can't very well have two different IFF systems. As a result the BC-645 became a common surplus item offered to radio amateurs for about the next 40 years.

The British didn't refuse to adopt it there was debate about whether to adopt the British IFF or the US Navy's ABA aka the US Army's SCR -515 later known as IFF Mk IV.

From The CXAM Goes to War - Chapter 6 of Radar and the Fighter Directors

"Status of Identification Friend or Foe in the U.S. Navy, May 1942
Engineer Robert M. Page at the Naval Research Lab realized early in his radar research that the capability to identify friendly aircraft should be incorporated with radar, and he began work on radar recognition equipment in 1937. By early 1940 he had working prototypes of both aircraft-to-ship and ship-to-ship identification devices. At this time the General Electric Company was brought in to participate in production design as the prospective large scale producer. In mid 1940 navy and army representatives agreed that the new IFF sets would be used jointly by both services, and the designs were adapted to accommodate army requirements. By summer 1941 GE was producing engineering development models, with the the air/ship version being designated "IFF ABA" and the ship-ship version "IFF BI."

The Anglo-American cooperation in radar that started with the Tizard Mission soon cast a cloud over ABA and BI production. It had been agreed that both nations would use the same recognition devices to prevent misidentification of the other's ships and aircraft, and Page had argued strongly for the NRL system. The British were concerned, however, that the ABA/BI, which operated on a fixed frequency independent of radar frequency, had its frequency set too close to the operating frequency of the German Wurzburg radar. This could result in the Germans soon discovering the existence of Allied IFF and devising countermeasures. It was thus agreed that the British system, with modifications, would be used.

The British Mark II IFF did not use a single frequency, but rather scanned through the frequencies of all radars and responded on the frequency of the radar that had interrogated it. The Americans were concerned that as more radars with diverse frequencies were added to inventory, the Mark II could become overloaded, especially in the heat of battle. All agreed that the Mark II system would be modified to work at a fixed frequency, and would be designated IFF Mark III. It was also agreed that the American ABA/BI would be produced in limited quantities for testing so that it could be ready as a backup system if the Mark III were compromised. On 1 December 1941, the Chief of Naval Operations authorized American production of both the ABA/BI sets and the Mark II and Mark III with a priority second only to radar itself. More than 3000 of the ABA/BI sets were delivered for testing by the Army and Navy starting in early 1942. For both U.S. and U.K. use, the U.S. agreed to start large scale production of Mark II sets as a stopgap, pending development and test of the Mark III; then Mark III sets would be manufactured in the U.S. for both sides. Mark III sets started trickling into the fleet by May 1942. "

The USN used IFF MK II at Coral Sea and Midway. Even then only limited number of aircraft were so fitted. By October they were able to convert to IFF III.

From
HyperWar: The Capabilities and Limitations of Shipborne Radar [Chapter 9]
"A different system of IFF has been developed for use if the Mark III system becomes extensively compromised. Components of the Mark IV system have already been produced, but an extensive program of operational and maintenance training will be required to put this system into effective operation. The greater complexity of the Mark IV will probably cause more maintenance difficulty than is being encountered with the Mark III equipment."

The ABA IFF was judged to require more maintenance

"The Mark IV IFF system has certain advantages over the Mark III because of the higher operating frequency. But, since all the interrogators operate on the same fixed frequency and all the transpondors on a slightly different fixed frequency, keeping all the units tuned properly will pose a considerable maintenance problem if this system is put in use. However, if adequate test equipment is made available to the Fleet, there should be little difficulty in keeping the Mark IV system operative after the operational experience gained in the use of the Mark III IFF system."

From US Army TS Signals 2 The Test: Chapter 3: The Call for Equipment (January–May 1942)

"Another important project involved airplane identification. It had been obvious since radar's inception that the ability to detect aircraft at distances far beyond the range of vision would be of slight value unless some means could be devised to distinguish friendly craft. That accomplished, unidentified airplanes would be presumed hostile. To this end the U.S. Army and Navy had already begun work on airborne radar equipment which they called RR, for radio recognition. The British called their somewhat similar development IFF, Identification, Friend or Foe. After the Americans and the British compared notes on radar, the Americans adopted the British terminology, and by 1942 were adopting their equipment also, despite the fact that in some respects the American RR was better. In January, while continuing work on the airborne component of RR, the SCR-515, the ARL also went about converting a considerable number of British IFF Mark II sets to SCR-535's. By March, the Radar Unit was working also on American versions of a newer IFF, the Mark III and III-G, copied as SCR-595 and 695, respectively."

IFF Mark III was based on IFF Mark II which had a proven operational record. The pragmatic decision was made to select the system that had been shown to work in real life.

 

[Reluctant Poster]

If you could have sent Dowding and Park back from 1941 to 1935 they would have changed many things. By that time in 1941 they knew the war started in 1939 and France fell in 1940.

Actually I don't think there is much that Dowding should change. Of all the prewar thinkers in any field he foresaw the future better than any of them. In fact he didn't just foresee the future, he created it!

 

[pbehn]

Actually I don't think there is much that Dowding should change. Of all the prewar thinkers in any field he foresaw the future better than any of them. In fact he didn't just foresee the future, he created it!

I agree, but if you apply 20/20 hindsight and give Dowding Park and those concerned 5 years notice they would obviously have done better. Forget the Defiant, get the Beaufighter (or similar) in service for mid 1940. Have all factories concerned breaking ground 2 years earlier so Castle Bromwich is in full production at start 1940 making Mk IIs then Mk IIIs. Increase all production AND pilot training so that even losses in France leave you with 1000 S/E fighters. Pour more resources into Chain Home and GCI so they are all operational at start 1940. Put proper funding into Whittles jet engine and have a squadron operational in 1940, however rudimentary. If you are allowed such hindsight, the Battle of Britain probably wouldnt have started and if it did would have been over very quickly, same for any night time "Blitz". The story of when things arrived in service was in many/ most cases dependent on when work started and how many reesources they were given.

 

[SaparotRob]

You don't know what you need until you do but Chain Home was prescient.

 

[Reluctant Poster]

I agree, but if you apply 20/20 hindsight and give Dowding Park and those concerned 5 years notice they would obviously have done better. Forget the Defiant, get the Beaufighter (or similar) in service for mid 1940. Have all factories concerned breaking ground 2 years earlier so Castle Bromwich is in full production at start 1940 making Mk IIs then Mk IIIs. Increase all production AND pilot training so that even losses in France leave you with 1000 S/E fighters. Pour more resources into Chain Home and GCI so they are all operational at start 1940. Put proper funding into Whittles jet engine and have a squadron operational in 1940, however rudimentary. If you are allowed such hindsight, the Battle of Britain probably wouldnt have started and if it did would have been over very quickly, same for any night time "Blitz". The story of when things arrived in service was in many/ most cases dependent on when work started and how many reesources they were given.

Dowding never wanted the Defiant in the first place. He wasn't responsible for building factories or pilot training. He wasn't in charge of The Ministry of Aircraft Production. You're giving him responsibilities he never had. He did fund chain home. I don't what more you could expect one man to do.

 

[pbehn]

Dowding never wanted the Defiant in the first place. He wasn't responsible for building factories or pilot training. He wasn't in charge of The Ministry of Aircraft Production. You're giving him responsibilities he never had. He did fund chain home. I don't what more you could expect one man to do.

It is purely a hind sight discussion, if you can give Dowding 20/20 hindsight and transport him to 1935 you can do it with everyone else. Dowding didnt make a RADAR system or a teleprinter or a telephone line or anything else in what is known as the "Dowding System" he did turn off the Hurricane tap though, and that wasnt in his remit.

 

[pbehn]

You don't know what you need until you do but Chain Home was prescient.

Wanting "early warning" is as old as military conflict, castles were built on hills and observation towers put on top. Dowding, from what I have read, was not your normal genius if he was a genius at all Chain Home RADAR (RDF) wasnt state of the art even at the time, nothing in the Dowding system was unknown AFAIK. Maybe the use of colour to represent time was a clever innovation. BUT he realised he needed a system for a pi$$ing competition. He didnt want titanium and gold pots, he didnt want complicated pots, he wanted lots of pots and thousands of people trained in the correct way to pee so they could do it 24/7, with all information handled in such a way they the section commander could have the correct people peeing in the correct place at the correct altitude.

 

[Reluctant Poster]

It is purely a hind sight discussion, if you can give Dowding 20/20 hindsight and transport him to 1935 you can do it with everyone else. Dowding didnt make a RADAR system or a teleprinter or a telephone line or anything else in what is known as the "Dowding System" he did turn off the Hurricane tap though, and that wasnt in his remit.

The discussion is about what Dowding should have done differently not how Britain should have rearmed. I can't think of anything he should have done differently. Also, please explain the Hurricane tap comment.

 

[pbehn]

The discussion is about what Dowding should have done differently not how Britain should have rearmed. I can't think of anything he should have done differently. Also, please explain the Hurricane tap comment.

His letter halting the sending more Hurricanes to be lost in France often referred to as "the Hurricane Tap", this left Dowding with 500 Hurricanes and Spitfires when France fell . The discussion started about what we can think up in 2024 with 20/20 hindsight about how things were done wrong or could have been done better 90 years ago. If you give Dowding any 100% certain 20/20 hindsight knowledge he would certainly have shared it with those above him. Yes, I agree it is a nonsense discussion, as is criticising people long gone, not here to defend themselves, when we know much more about what the enemy was doing and how things panned out than they did or could. We still have clowns and their number increases by the year lambasting Chamberlain for his "peace in our time" speech and piece of paper when everything Churchill used in 1940 was ordered by Chamberlain as either Prime Minister (from 1937) or Chancellor (from 1931).

 

[Shortround6]

I agree, but if you apply 20/20 hindsight and give Dowding Park and those concerned 5 years notice they would obviously have done better. Forget the Defiant, get the Beaufighter (or similar) in service for mid 1940. Have all factories concerned breaking ground 2 years earlier so Castle Bromwich is in full production at start 1940 making Mk IIs then Mk IIIs. Increase all production AND pilot training so that even losses in France leave you with 1000 S/E fighters. Pour more resources into Chain Home and GCI so they are all operational at start 1940. Put proper funding into Whittles jet engine and have a squadron operational in 1940, however rudimentary. If you are allowed such hindsight, the Battle of Britain probably wouldnt have started and if it did would have been over very quickly, same for any night time "Blitz". The story of when things arrived in service was in many/ most cases dependent on when work started and how many reesources they were given.

This requires a considerable change in RAF and Air Ministry thinking.
In an old thread on somewhat similar lines I once counted at the end of 1938(?) that the RAF had about 1000 fighters on order (including end of Gladiator production, this may be low as Spitfire orders may have been increased in 1938 to about 510) and about 4000 bombers on order. I did not count trainers or flying boats or transports. These are 1938 bombers.
We can see at that point in time, where the emphasis was. At different points in time the emphasis changed. Unfortunately some times the allocations of increased resources did NOT change the proportions of of the emphasis or not by much.
To further your last statement. There were two orders for the Stirling bomber (100 aircraft each) before the Munich agreement which were soon changed to 1500 aircraft total a short while later and expanded production to 3-4 additional factories. 1st Production Stirling flew about 1 1/2 years after Munich and the first operational mission was 2 1/2 years after Munich with three Aircraft.
The British were trying desperately to increase the size of the RAF. You need about 10 ground crew for every pilot.