Sunday, April 24, 2011

Running Away to the Air, 3: I Never Thought of That!

I wasn't kidding when I said that I loved John Terraine's Smoke and the Fire,  a book about the "myths and anti-myths" of the First World War. He asked us to understand the historical actor within his context and understand his difficulties. The fact that he was defending Lord Haig only made it more poignant. It's always easy to criticise, but there's something about a uniform....

And then there's the bomber barons. I'm only vaguely arguing against straw men when I suggest that our picture is of H. G. Wells published War in the Air in 1907, and producing advance lineups at the CND next day. The government, as usual sensing the public will and steering a (secret) opposite course, immediately appointed a few generals to be in charge of bombing foreigners into extinction (including Germans, provided they could be forcefed melatonin pills). Said generals promptly ran out and began publishing articles on the inevitability of strategic bombing campaigns that would level all civilisation with a single "knockout blow." Twenty-two years later, the Prime Minister scheduled a meeting with the barons:

Prime Minister: "Good Morning!"
Some Honourable Generals Air Marshals: "Welcome to Ad Astral House!"
Prime Minister: "Ah, thank you, my good men."
Air Marshals: "What can we do for you, sir?"
Prime Minister: "Well, I was giving a speech in the Commons just now, declaring war on Germany, and I suddenly came all over bloodthirsty."
Air Marshals: "Bloodthirsty?"
Visiting Admiral: "Desirous of some effusion of human life."
Prime Minister: "In a nutshell! And I thought to myself, "a little knockout blow will hit the spot," so, I curtailed my activities, sallied forth, and infiltrated your establishment, seeking some block busting!"

Air Marshals: "Come again?"
Prime Minister: "I want to order some bombing."
Air Marshals: (lustily): "Certainly, sir. What would you like?"
Prime Minister: "Well, eh, how about a little precision day bombing."
Air Marshals: "I'm a-fraid we don't do precision, sir. Waiting on calculating bomb sights."
Prime Minister: "Oh, never mind, how are you on daylight area bombing?"
Air Marshals: "Just as soon as we get fighter escorts. We never have that at the end of the week, sir, we get them fresh on Monday."
Prime Minister: "No matter. Well, stout yeomen, some targetted night bombing, if you please."
Air Marshals: "Ah! It's been on order, sir, for twenty years. Was expecting it this morning."
Prime Minister:  "'T's Not my lucky day, is it? Aah, night area bombing?"
Air Marshals: "Sorry, sir."
Prime Minister: "Bombs lobbed in their general direction?"
Air Marshals: "Normally, sir, yes. Today the planes broke down."
Prime Minister: "Leaflet dropping?"
Air Marshals: "Ah! We have leaflet dropping planes, yes."
Prime Minister: "You do! Excellent."
Air Ministers: "Yessir. It's..ah,.....they're a bit lost....
 Prime Minister: "Oh, I like my leaflets a bit misplaced."
Air Marshals: "Well,.. they'd be very misplaced, actually, sir."
Prime Minister: "No matter. Fetch hither the bewildered bombers! Mmmwah!"
Air Marshals:  I...think they're a bit more bewildered than you'll like, sir."
 Prime Minister: "I don't care how bewildered they are.  Hand them over with all speed."
 Air Marshals: "Oooooooooohhh........!"
Prime Minister: "What now?"
Air Marshals: "The Colonial and India Offices have taken them all."
Prime Minister: "Demonstration flights?"
 Air Marshals: "No."
 Prime Minister: "You do some operational flying, don't you?"
 Air Marshals (brightly): "Of course, sir. It's an air force, sir. We have....
 Prime Minister: "No, let me guess. Night flying training?"
Air Marshals: "No, sir."  
 Prime Minister: "Figures. Predictable, really I suppose. It was an act of purest optimism to have posed the question in the first place. Tell me."
Air Marshals: "Yessir?"
Prime Minister: "Have you in fact got any flying here at all?"
Air Marshals: "Yes,sir."
Prime Minister: "Really?"
 (pause) Air Marshals: "No. Not really, sir."
Prime Minister: "You haven't."
Air Marshals: "Nosir. Not a plane. We were deliberately wasting your time, sir."
Prime Minister: "Well I'm sorry, but I'm going to have to fire you."
Air Ministers; "Right-o, sir."
     The Prime Minister hires a staff of editorial assistants and publishes a history of the Second World War in which it is all the air marshals' fault.
Visiting Admiral: "What a *senseless* waste of human life."

In less Pythonesque terms, the argument is usually put that what with all the dreaming of a bright future, the Air Staff failed to make any actual provision for the future. For Max Hastings, it's an air force that spends all of its money on buildings, neglecting research and development. In John Terraine's Right of the Line, it's a rather careless comment from Sir Maurice Dean to the effect that the RAF had moved backward from 1919 to 1929. That Dean was a 23 year-old new hire in 1929 might have been more explicitly shared.

But here's something that has already exercised me on this blog: we know what a ten year gap in research and development looks like, because we can compare the RAF of 1949 to that of 1939. When we do so, we appreciate that the planes have changed remarkably. When we drill down for an explanation for that, we find ourselves compiling lists of technological changes with profound implications in every aspect of human life. To say that the RAF should have been as ready for war in 1939 as it was in 1949 is to say that vinyl couches, hi fis, colour televisions and computers "should" have been on sale in 1939. It's a picture of the world in which technological progress is exogenous to historical development, in which a single tinkerer could have brought steam engines to the Roman Empire. So the stakes are rather higher for historical praxis than the narrow argument suggests.

And then there's this, which may or may not be accessible right now (I'm having trouble): in the 1938 Air Exercises, a pervasive fog set in on Sunday night, closing airfields widely in the south of England. As a result, a Harrow of 37 Squadron crashed into a tree when it came below the clouds to fix its location. A Battle was lost after spending 5 hours wandering. It crashed while landing in a field, and the air gunner was killed. 3 Demons sent up for night interception work were abandoned by their crews who parachuted to safety. The Exercises were cancelled the next day in driving rain on London. Terraine quotes Air Marshal Ludlow-Hewit's Inspector-General's report, notes 478 RAF forced landings in 1937--8, and goes on to observe that no civil airline would tolerate such statistics, because apparently he'd never heard of the 1938 Christmas Air Mail fiasco. (By the way, a book I found doing a Google search for a good source on the last.) The Air Marshals had apparently not seriously considered this whole "navigation" thing.

But, following Terraine's advice all those many years ago, one might ask whether it was actually all that easy.

Consider the problem, which is that you're in a plane, and you don't know where you are. Today we solve this problem with GPS. The fact that we need an orbitting network of satellites and computerised equipment to talk to them suggests that, just perhaps, the problem wasn't simple to solve. But maybe they had a simple solution in the old days, and GPS is just easier.

And, indeed, they did. You can figure out your location on the surface of the Earth in a very short time with nothing but some simple instruments, a very accurate clock set to a reference time, an unobstructed view of the stars, a celestial almanac, and awesomely powerful powers of mental spherical trigonometry. Things get more complicated the more rigorously you limit these assets. The most basic point is that it takes time to make observations, and time to calculate position from them. This is irrelevant for a stationary observation point, but introduces error in a reference frame moving with respect to the Earth. This gets to be more of a problem as the quality of the data degrades, perhaps because you are locked up in a loud, vibrating metal coffin of a plane moving through the darkness at a very high rate of speed.

There is a solution to this, called "dead reckoning." Knowing one's speed and direction of travel (which we can obtain in a nonlocal way from a compass), one can fit this data back into one's celestial observation set. Unfortunately, this introduces an additional problem. A WWII aircraft will have an indicated air speed will be in excess of 60 meters/second (caution: I'm just pulling a 3.6x adjustment to km/h out of my rear at this point.) However, this will vary from actual over-the-ground speed by a wind speed contribution of rarely less than 3 meters/second and sometimes more than 40. This contribution is very difficult to measure, especially at night, when you cannot use a drift sight.  In theory, you can take it out of a measure of indicated air speed in a pitot tube open to the outside air (if you are flying into or with the wind; otherwise it gets more complicated again) but for this you need to know atmospheric pressure outside. This will depend on the accuracy of your altitude measurement and in turn on a barometer calibration. Ideally, you want accurate, current meteorological information and a pitot that doesn't ice over. Fortunately, this problem was solved early in the interwar period. Unfortunately, it was solved again about six months later, and then again in another six months, and so on. Curse corporate PR releases as a source for the history of technology!

So what do we do about it? First, we realise that the whole problem is much more of a moving target than we might appreciate. John Alcock and Arthur Brown were fine aviators, and C. M.Poulsen, the longtime editor of Flight liked to tell a story about how Brown dropped an article on new air navigation techniques at the office shortly before leaving for Newfoundland, only to have some officers of the RAF come by next day to confiscate the manuscript. Because in 1919, the techniques used to fly a Vickers Vimy from Saint Johns to Ireland were a state military-technical secret. (Take the anecdote for what it's worth.) Yet the plane Brown was flying in had open cockpits and a cruising speed of less than half that of a WWII bomber. Those latter had astrodomes for navigational observation, but this would have been entirely impractical without Plexiglas/Perspex, first brought to market in 1933, on the basis, according to the official corporate history, of research into artificial bates for leather treatments. No wonder there's so much b.s. in WWII history of technology. (Although to make the feeble joke work --and I love feeble jokes, even I don't always get them in time-- I should have said pigshit. Because leather bates are made out of ....never mind.)

That's one thing, perhaps the least important thing. Another way to find out where you are in a plane when you're lost is to ask someone. Two or more radio stations on the ground can give you the bearing on which they hear your transmission, and you can do a "reciprocal bearing" on your charts to find your location. This technique takes off naturally from the older use of lighthouses. According to urban legend at least, in the first decade of radio, Marconi operators would gleefully jam requests for bearings made on pirate radios. Given the amount of noise early spark-gap transmitters made, it would be hard to tell if it were being done deliberately, but I throw this out for those who might think that the idea of electronic warfare somehow first glimmered in tactical minds in the fall of 1940. (Two accessible histories of electronic warfare.) You can also simply take your own bearings using a "radio compass," a common piece of equipment on everything from aeroplanes to Admiralty-subsidised trawlers by the late 1930s. This I throw out to suggest that the idea of having a device on board your ship that uses radio to give you navigational information was, also, not entirely a bolt from the blue in 1939. And that's without even bringing up sonic depth sounders on interwar fishing vessels or Western Electric's much announced, long delayed "radio altimeter."

So between bearing finders and weather reports, a radio is a pretty important asset for an aerial navigator. One might imagine a technology that could automate "dead reckoning" and make celestial navigation much easier, but if I talked about that I would be moving into the old "just in time paradigm." Cool as the Air Location Indicator was, it only got into the air in 1943. Instead, I'll finish up this post by talking about radios. Which can be complicated. Good thing that it's a magic complication! I mean, Doctor Howard might have blah-blah-blah about antenna impedances and such in "Topics in Electromagnetism" (and very occasionally about dialectic theory), but you can trust the engineers to get it right on the day and thus never actually use a partial differential equation. Surely?

Well, no. The process was, again, complicated. Here's a section that is going to read a little odd, because it is a paraphrase of Air Ministry scientist N. F. S. Hecht's summary of twenty years of work. It's illuminating (I think.)

Early radio communications were carried out in slow a/c. In these the antenna was a simple trailing wire played out by a manual reel (powered reels, although experimented with, were more trouble than they were worth). These antennae were sufficiently long to pick up long and medium wave signals. Unfortunately, as aircraft speed rose, the wires increasingly did not trail directly behind the aircraft, but rather doubled up, presenting a safety hazard, but more importantly reducing the effective length of the antenna while negatively effecting geometry. Various weights or fairleads reduced this problem, and with increasing speeds these became more elaborate and extended to the structure of the antenna itself. (Note that these cables had to be reeled up before landing, leading to one or two incidents in which commercial aircraft were thought to have crashed on landing on particularly foggy nights until a search party found it sitting out in the field, crew and passengers presumably waiting, incommunicado, for a bus before debarking. More commonly, this presented the problem of losing communications with the tower at the moment of landing.)

Faster a/c required less [insane] provisions, specifically,  shorter, fixed antenna. These necessarily had lower emitted and received power, worked on shorter wavelengths, and presented difficulties of location. Reducing current loss in this new generation of aerials forced designers away from making the aerial a simple part of the receiving/transmitting circuit. Instead, transformers were placed in the antenna circuit to make loading more efficient. However, the new aerials had remote anchors on wings, tails, etc. While one transformer in this case could be proximate to the receiver/transmitter, the other had to be remotely located. This meant that there had to be remote power control of the transformer as well.
In early RAF a/c circuits were simply earthed to large metal objects in the a/c such as engines. With all metal structures this became simpler. However, the capacitance of these structures was not so great that they could be safely regarded as a simple universal condensor of equipotential geometry, as the real earth is. Instead, aircraft structures carried induced oscillations that produced impedance in the radio circuits. To avert this, it was necessary to install condensors to smooth out these oscillations.
Even at an early date, the RAF found it necessary to use at least two frequencies, since short waves is not effective at the first skip annular ring, 150–300 mile ranges. This meant that the R/T circuit had to be set to variable frequencies. They also had to be set to varying powers, since in Fighter Command in particular aircraft were found to be communicating with both a/c in formation, and with ground control. This meant that some kind of volume control was necessary. The task was sufficiently complex that existing types of automatic volume control were inadequate. The author perhaps implies that the RAF was using a new type of automatic volume control, but states explicitly that the solution adopted by the RAF over time was still manual control.
Meanwhile, in operations aerials were found to ice over, while the cold affected wires. Vibrations, the particular nightmare of the classic British  high rpm-powerband sports car, loosened connections, while noise made communication difficult, leading to a veritable saga of spark plug shielded harness design and redesign. (Early shielded harnesses had a capacitance that fed back through the spark plug producing an erosive current in the points.)
Power for radio equipment had at first been taken from windmill generators. These were a fruitful field for the application of anti-icing measures and constant speed regulation of some kind,* but this has just come to an end, with R/T equipment now powered from the engine. This still required that batteries remain in the circuit both to provide power while the engines aren’t running and to provide the small, regulated currents required for indicator lights and so on. The new generators have presented difficulties. Voltage regulation is problematic, especially since their output has to be at both high and low voltage.

As I've said, I've paraphrased, with additional comments, an article by N. F. S. Hecht here. (“Radio in Aviation: A General Survey, With Special Reference to the Royal Air Force, J. Inst. Elec. Eng 85 (1939,2): 215–37.) ) Hecht is not, of course, in the business of giving away the store here. In particular, his section is working away at VHF-band radios suitable for aircraft, something that in practice mainly requires work on antenna impedances and radio volume controls. These will famously be deployed in the course of the Battle of Britain as one of many mid-battle technical improvements. Among other things, VHF radio will make single-seater fighter-reconnaissance types truly viable and give fighter bombers a role vaguely proportional to their cost.  

That, however, is not what I'm talking about here, and a good thing, because I'd have to go into handwritten notes to recover some stuff and this has already taken long enough. Mainly I'm trying to come across saying that radios, just like many other emergent technologies of 1939, were complicated and required a great deal of interwar work. This is no great insight, but contemplate the fact that when Hecht's section began work, there was no technology that allowed a person to adjust the volume of a remote speaker. I have an intuition that there's an intersection between the music industry and the military-industrial complex that we've barely even begun to explore. Perhaps the delay in developing radar compared with sonar and radio has something to do with the mindset within the music industry that focussed on the recording end. When focus shifted to reproducing, when we began seriously to think of "producing" music as a composite of tracks, amplifying it and transmitting it from situated speakers --when we got rock and roll. Perhaps as a result of a wartime paradigm shift? Or just because the technology matured. But is there a difference?

*So that the first constant-speed airscrews to fly powered radios, not the plane.

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