The Mystery Continues

I've been meaning to write something about the disappearance of MH370, except that there's not a whole lot to say. What we don't know dwarfs what we do. With so little information to go on, speculation runs rampant ... and who's to say what's right?

That's still mostly true. At least, it's true until new facts surface.

Perhaps "surface" is an unfortunate word choice in this case. Last Wednesday, an interesting piece of debris washed up on the shores of Reunion Island in the Indian Ocean. It's the right size and shape, and more importantly it bears the Boeing part number for a flaperon on a Boeing 777 airliner. News agencies were careful not to go too far out on a limb with this, and only said it might be from MH370.

Caution is all well and good, but exactly one 777 has gone missing. One more than none, and one less than two. If you find such a part floating around the ocean, where might it come from? You get three guesses, and the first two don't count.

Now, we can't say a whole lot just yet. It's only one piece, after all. But its condition tells us a great deal indeed. It allows us to put some reasonable bounds on what might have happened.

First of all, we can once and for all discount and discard all those loony theories about terrorists hijacking it and flying it to a hidden airbase. The fact that fragments are washing ashore means it went down over water. I never could make myself take that option seriously, anyway. The Boeing 777 is an enormous airplane. You'd need eight thousand feet of runway to land it, and 45,000 gallons of fuel tanks to refuel it. Good luck building such a secret airfield without the NRO finding out about it.

No, that never even made bad sense. Nor did any of the other hijack/misdirection theories. The people who might have been able to pull it off lacked any visible motive, and the people with motive had no means.

So, it went into the water. But not on a steep, nose-dive trajectory. That kind of impact would have destroyed it utterly. It's in relatively good condition, no obvious deformation. That argues for some kind of horizontal entry, most likely after fuel exhaustion. Leading, of course, to the question of how it got there. There is certainly no shortage of theories.

What keeps tugging at my attention, though, is what we do know about the plane's path. It went incommunicado shortly after signing off with Malayan ATC, and shortly before they were supposed to contact Ho Chi Minh ATC for enroute clearance.

I wish I could remember precisely where I saw this -- odds are better than even it's someone James Fallows at the Atlantic was corresponding with at the time -- but it reminded me of one key fact. Pilots always have an alternate airfield in mind. No matter where they are in their flight plan, they always know the closest airfield they can make for if something hits the fan. And MH370 made a beeline for Penang, the closest airfield at the time that could accommodate them.

The question becomes: Why?

I'm having a hard time convincing myself that it was anything but a fire in the cockpit, possibly an electrical fire of some kind. In that case, standard procedure is to turn off anything that might be feeding the blaze. Radios, transponders, whatever; if it draws power it's got to go down, until you have the fire under control. The right turn at Penang confused me, though. Then, I went and did some digging. Not much, Googling for "penang approach chart" turns up all kinds of useful information. The details are here if you should care to see for yourself. The pertinent bit is shown below.

At first glance, then, it looks as if they set their autopilot to make a beeline for the BIDMO meter fix, and then join the inbound traffic for runway 04/22. They might even have programmed their autopilot to make the base leg turn ...

Under this theory, they failed to control the fire, and were no longer conscious when they got there. I'd even hazard a guess that no one onboard was. There are no airtight bulkheads on an airliner. Toxic air will get to everyone eventually.

Or it might have been decompression. We had a similar event, on a smaller scale, back in 1999 when Payne Stewart's private plane lost pressurization, and sailed across country until fuel exhaustion.

But this leaves one question unanswered: why did it turn south? If, indeed, it did turn south? Its last known course was more or less towards India. It had to have made a left turn in order to end up in a position for one of its parts to wash ashore on Reunion.

We still don't know. We won't know that until after we find the wreckage ... and we might not know even then. 

We may just have to get used to not knowing. While all questions have answers, we are not promised that all answers will be revealed.

Any Landing You Can Walk Away From...

As the old saying goes, any landing you can walk away from is a good one. And if they get to use the airplane again? That's a great landing. A couple of things I saw recently brought that to mind.

First, an incident reported by CNN. They didn't say which ship this was, but a Marine Corps AV-8B Harrier II pilot had a bit of excitement during a training mission. Takeoff was routine enough, but when he raised his landing gear, the nose gear didn't come all the way up. OK, that's bad. Time to go around for a landing. But wait, there's more!

CNN doesn't do embedding, sorry to say. But the rest of the story is that the nose gear wouldn't come all the way back down, either. But that's OK, because they're prepared for just such an emergency. Turns out they've got a standard piece of equipment to catch the nose. The pilot just has to line up on it exactly for it to work. Fortunately, lining up exactly is what Marine Corps aviators do for a living.

But, I have to say, that feat of airmanship pales by comparison to something I saw on my way home. The traffic seemed worse than usual. You almost never know exactly why. As I took the Highway 287 exit south from I-20, I saw some police cars parked on the overpass below. I didn't see what they'd stopped for. I was kind of busy driving. But, after I got home and checked up on some news, I saw what it was and wish I'd actually seen it.

Pictured: A lifetime supply of luck, expended.

Yes, you're seeing that right. Someone landed an airplane. On a curved highway overpass. IN RUSH HOUR. And they're probably going to live long enough to brag about it.

I'm trying to think of something else to say about this, and I'm failing miserably. If you pitched this as a scene in an action flick, they'd laugh you out of the room. No one would believe it. This is either a harebrained stunt gone wrong, or an unbelievably awesome feat of airmanship, bringing a busted bird home. I really hope it's the latter.

Either way, they've got a story to tell their grandkids that'll be hard to top.

Video Del Fuego, Part XLVII

The 1950s were a fine time to be an aeronautical engineer. There was so much new ground to be covered. There were so many new ideas to try. Many of those ideas were pretty weird, and there are plenty of perfectly good reasons we don't try them anymore, but no one knew those reasons ... yet. And there was only one way to find out. Which made that era, from approximately 1940 to 1960, such a rewarding time to work at places like Convair, Lockheed, Bell, or North American.

Some of the ideas to come out of that era shaped the way we still build airplanes to this day. Others, not so much. Some really peculiar aircraft parted company with their shadows in those years. For example, did you hear the one about the supersonic seaplane?



This beautiful craft was a contemporary of Convair's other delta-wing fighters, the F-102 and F-106, adapted to take off and land on the open ocean. The basic problem was this: the Navy wanted a supersonic fighter for fleet defense. But, there were serious doubts about being able to launch and recover supersonic fighters from aircraft carriers. So, Convair came up with the idea of adapting the Delta Dart with skids, so that it could take off and land at sea. The F2Y was a stunningly beautiful aircraft, and to this day is the only seaplane to break the sound barrier. That said, landing a delta-wing aircraft on water without hurting yourself is damn hard. They never built more than the one F2Y prototype.

Now, the Navy's designation F2Y leads to a question. Pre-1962, the Navy system for aircraft designation was first, a letter or letters for the mission; second, a series number; and third, a letter for the manufacturer. The numeral "1" was usually omitted. So, the Grumman F4F Wildcat was the fourth Navy fighter built by the Grumman corporation. And the Convair F2Y would have been the second Navy fighter built by Convair. What was the first, you ask?



Hoo boy ... Here was another solution to the problem of basing aircraft on ships. The Convair XFY was to be a VTOL fighter that could take off and land on any ship, meaning that any task force at all could have fighter support, even without a flat-top present. Lockheed also had an entry in this category, the XFV, but it never actually achieved full transition from vertical to horizontal flight, and never flew without a protective undercarriage. The Pogo managed several such transitions. The concept had a serious flaw, though. Imagine, for a moment, trying to land this thing on the fantail of a frigate, pitching and heaving in the middle of the ocean.

Yeah. No one else thought it was a good idea, either. You have to love a flight test report that ends, "We think it highly inadvisable to land this airplane."

We can look back and laugh now, but still ... this would have been a fine time to be a staff engineer at Convair. They got to work on some incredible stuff. For every crazy idea that didn't work, they had one or two that did. Designs that were cutting-edge when conceived were sometimes obsolete by the time they entered production. It was a wild, crazy time, and I'm kind of sorry to have missed it.

For Want Of A Nail

I have a fascination with the last irretrievable moment. In every accident, in every major event, there's almost always a definable moment where disaster could have been averted. If only key people had had one key piece of information, if only they'd made one decision differently, everything could have been different.

There was one such moment during the last tragic mission of Columbia. If the manager in charge had pushed for satellite images of the shuttle's underside, the extent of the damage might have been known, and it might have been possible to mount a rescue effort. There's a lot of mights involved ... but we also might have gotten those seven people back alive. And we might be seeing one now, in Washington. But that's not the one I'm talking about today.

On the first of June, 2009, Air France Flight 447 disappeared over the Atlantic Ocean. Its automatic systems had blurted out signals of danger, and then, silence. At the time, I had speculated about what might have gone wrong. Speculation was all it amounted to. Without the flight data recorders, no one would ever know the truth of the matter, and the data recorders were buried under eleven thousand feet of ocean. I fully expected no one would ever see them again.

I vastly underestimated the tenacity of France's Bureau of Investigation and Analysis. In May 2010, they had narrowed the location down to a five by five kilometer area. That gave them a small enough zone to allow a team from the Woods Hole Oceanographic Institute to make a more detailed search. In April of this year, they found the wreckage, and with it not only the flight data recorder, but also the cockpit voice recorder. If that wasn't amazing enough, they were able to recover all of the data from both devices. Truly, this was astounding work, and my hat's off to them.

Now, after sifting through the reams of data available to them, the BEA has issued some preliminary reports. It turns out that some of my initial speculations were right, some less so.

The data clearly tells us that the pitot probes had iced over, corrupting the data going into the air data computers. This meant that the data feeding the primary flight displays weren't any good. What's not clear to me yet is exactly what happened next. They don't say if an updraft lifted the nose of the aircraft, or if the ice on the aircraft caused it to slow to a dangerously low speed. I'm guessing the latter, because they say that the crew pulled the nose of the aircraft up, which they probably wouldn't have done if the aircraft was already nose-high. The main point is, the aircraft was already on the verge of a stall, and lifting the nose made a bad problem worse. The aircraft then simply fell out of the sky.

The preliminary report released today says that it's basically a pilot training problem. Pilots typically have little to no training flying an aircraft manually at that speed and altitude, and therefore have little intuition on how they should recover from a situation like this. The BEA recommendation is to add this condition to the pilot training syllabus.

After thinking about it a bit, I have a few observations of my own.

1) Standby instruments rarely get the respect they deserve. Ideally, your cockpit scan should include your standby instruments, especially in a glass-cockpit airplane. If your air data computers are hosed for whatever reason, your standby instruments may still have good information on what your airplane's doing. If your standby instruments don't agree with your primary displays, you've got a problem. Exactly what kind of problem you won't know, but at least you can start looking. This particular failure cascade seems to indicate that the crew were still flying by the primary displays, up to the point where they no longer had any aerodynamic control. Respect your ISIS, ladies and gents, that's what it's there for.

2) Airbus makes an exceptionally sturdy fuselage. Really, this could apply to any modern composite-structure fuselage. They're absurdly strong. From the initial reports, I expected that the aircraft would have broken up in midair from aerodynamic stresses. A mostly aluminum structure probably would have. But from the wreckage, we know that it was intact when it hit the water. It was doing some pretty serious gyrations on the way down, and didn't come apart. That's solid construction.

3) These days, we can find damn near anything, damn near anywhere. I was sure those recorders were gone forever. Fish food, if there are any fish that live two miles down. Apparently, modern sonar is as good as a searchlight. I don't know exactly how those French submarines were able to narrow the field down as close as they did, and for obvious reasons they're not telling. But it's clear that if they want something found on the ocean floor, it can be found. And that wasn't a guarantee ten, or even five years ago.

4) There's a good reason for all this, besides morbid curiosity. The reason people like me pick disasters apart like this isn't that we're morbid toads. We may be, but that's beside the point. We want to know what happened, and how it happened, so we can stop it from happening next time. If that's even possible. The important lesson to come out of all this is that we've uncovered a gap in pilot training. We have the means at our disposal to close that gap. Thirty minutes of simulator time a year, and a pilot will have "experienced" this situation with enough fidelity that he or she will know what to do if the real thing ever happens. The next time this happens we'll probably never hear about it. The passengers will experience a bout of worse than normal turbulence, the pilots will experience five minutes of bowel-freezing terror, but the airplane will arrive at its scheduled destination. We'd have not known this, if we'd let it alone. Poking and prodding is part of our job. Our duty. Not always the most pleasant part, but an essential part nonetheless.

It's not much consolation for the people who lost loved ones two years ago, but this knowledge, painfully gained, may allow us to save the next one. That's certainly worth something.

Dedicated to the memory of Dr. Don Seath, my first professor in Aerospace Engineering, who passed away in May from pancreatic cancer. You taught me well.

Chinese Stealth Fighter

The wires are abuzz this week with new pictures of what is supposed to be China's answer to the F-22 Raptor. After taking a critical look at the pictures, I am somewhat less than worried, although I understand how a casual viewer might be alarmed.

For purposes of comparison, here's a picture of the F-22 Raptor. The first example, a YF-22, first flew in September of 1990; and the first F-22 squadron came on-line for duty in December of 2005.



At first glance, this looks scarily similar:



There are, however, a few key differences, as well as a few important details to point out.

(1) The first is, of course, the time delay between the first flight of a new prototype and the IOC date of the first operational squadron. For the F-22 Raptor, that was just over fifteen years, from 9/1990 to 12/2005. Now, I have no reason to believe that the Chinese engineers are total idiots, but at the same time neither do I have reason to believe that they're supermen. I don't see them paring too many years off that figure. So, if we're to believe that the first flight was fairly recent, IOC can be no sooner than 2020-2025. By which time, we'll have ... well, I'll save that point for later.

(2) The second is that, while the fuselage sure looks like it's got a nice low-observable shape, the devil's in the details. For one, the shape is only half the story, there. Do they also use the right radar-absorbing materials in the skin? And, taking a closer look at the front view, we see a huge potential problem:



I count four under-wing hardpoints. External carriage of weapons and/or fuel tanks pretty much destroys any stealthing advantage your fuselage shape gives you. Unless this aircraft has provisions for internal weapon carriage, they lose the stealth part of the battle pretty horribly. (Caveat: those may not be hardpoints, but may instead by housings for control actuators. Even so, those 90-degree corners make nice little echo boxes that render the sloping fuselage moot.)

(3) The third point is readily apparent from a rear-view shot:



Oh, dear. Fixed axisymmetric nozzles. No thrust vectoring for you! Thrust vectoring is damned useful to have. Not having it, and then getting into a turn-and-burn fight with an airplane that does, is going to suck.

(4) The fourth problem is something I once heard described as the Montana Syndrome, after the Montana-class battleship. The Montana-class battleship was supposed to be the U.S. Navy's answer to the Japanese super-heavies Yamato and Musashi. It wasn't. Yamato and Musashi both got their tickets punched by the Grumman Avenger and the Curtiss Helldiver, and the Japanese sailors never once saw the American carriers that did them in. The few hulls of the Montana class that had been laid down were never completed. The battleship was an idea whose time had come and gone. I'm fairly convinced that the manned tactical fighter is headed down the same road. So far as I'm concerned, the Chinese are welcome to spend as much money as they like on last year's model. By the time this sees service in squadron quantity, air combat will have changed almost beyond recognition, and the skies may well be dominated by laser weapons and unmanned combat aircraft.

In short: panic is unwarranted. Calls for extending the production run of the F-22, likewise. This fighter doesn't look as good as what we're already fielding in the first place, and it's the wrong answer to an almost outdated question, anyway. We've already got a solid lead in UCAV technology. Extending that lead is fairly easy, provided we don't let ourselves get goaded into reprising last century's best technology.

Election 2010 Postmortem

The results are in, and they're interesting to say the least. Just like we do every two years, the entire House of Representatives and one-third of the Senate went up for election. As expected, the Democrats lost control of the House. Also as expected, they retained control of the Senate. But neither the victories nor the losses are entirely as they would seem on the surface. And, as a bonus feature, two other odds and ends from the week that I thought would be important.

(1) The Results: Currently, the tally looks something like this:

House of Representatives: 242 Republicans, 193 Democrats
Senate: 47 Republicans, 53 Democrats

Note that I put the Senate's Independents with the party they'd be expected support.

The pre-election predictions under-estimated the Republican gains in the House, and slightly over-estimated gains in the Senate. The main story here, I think, is the continuing lousy economy. We've known since about January that the Democrats would pay a steep price for holding the bag this year, and here's the pay-out. As I've said before, it may not be right or fair, but conditions like this always play against the party in power. The other big story of this election cycle was the heavy involvement of Tea Party activists, which brings us to ...

(2) The Tea Party: The Tea Party both did and did not help the Republicans. Their enthusiasm may well have put a few candidates over the top that otherwise wouldn't have made it. However, if we examine the results using the Electoral Explorer feature, an interesting picture emerges:

Non-Tea-Party House Races: 200 Republicans, 104 Democrats, 2 currently undecided
Tea-Party House Races: 39 Republicans, 83 Democrats, 7 currently undecided

In sum, Republicans not affiliated with the Tea Party won two races for every loss, and Tea Party Republicans lost two races for every win. I don't know precisely what this means, but surely, it's important. My gut feeling is that the contentious nature of Tea Party candidates had a tendency to backfire amongst moderate voters.

Still, it's pretty clear to me that not only did the Tea Party not win the House for the GOP, they may well have cost them the Senate. I think John Boehner may have figured this out. On Wednesday, he did not exactly sound like someone who had routed an opponent and had them on the run. The question is, who else has figured this out? Will the Tea Party activists continue to agitate and demand for ever more extreme candidates? Will they claim this as their victory, and carry this through into 2012?

The next election cycle could prove very interesting, indeed.

(3) A House Divided: And so, we find ourselves once again with a divided government. This is not especially unusual for us. We had such for most of Reagan's two terms, and for most of Clinton's two terms. It wasn't the end of the world then, and it won't be now. What I said before still holds: after a period of such intense change, it may well be a good thing to take a bit of a breather. The Executive and the Legislature will find a way to work together, sort of, if only to keep the government from shutting down altogether. But don't expect any major initiatives. The bad thing about this is that major decisions will probably get kicked down the road, and you can only get away with that for so long.

(4) ...It Must Be A Damn Peculiar Question: Jerry Brown? I didn't know he was still in politics. Either that, or the Terminator's last act before resuming his mission for Skynet was to open a rift to the '70s. Still, this -- even this -- isn't the weirdest thing to happen in California politics. There was a Congressional election from 1948 that merits notice. Republican Congressman Richard Nixon was facing a grueling, bitter contest against the winner of the Democratic primary ... Richard Nixon. Yes, Californians used to be able to register for both primaries. History leaves us no record of the Nixon-Nixon debates, but they must have been quite a show. All kidding aside, I wish Governor Brown all the luck in the world. He'll need it.

(5) A Fire in the Sky: This is just about the last thing you want to see when you look out of an airplane's window:



You've probably heard by now about the Quantas A380 that had to return to Singapore due to an engine fire. The immediate question that rose when I saw this picture was: is there a problem with this engine? This particular A380 uses the Rolls Royce Trent 900 engine, which was developed from the Trent 800 used in the Boeing 777. I had started to wonder about what kind of failure cascade could produce such an accident ... but today, we see this news item about yet another Quantas flight suffering engine trouble, this time a Boeing 747-400. Needless to say, this aircraft does not employ the Trent 900, although I think it does use another Rolls Royce engine. Anyway, I've stopped wondering about possible design flaws. It's probably time for someone to take a nice long look at Quantas' Singapore maintenance shop. [Addendum, 8Nov10: Then again, maybe not. BBC World Service had an item this morning regarding tests Quantas engineers have been running on their A380 fleet. They have identified problems with four of their six aircraft, which works out to one in six of their Trent 900 engines, if I understood it correctly. They haven't identified the specific problem yet, but it appears to be a oil leak of some kind in the turbine section. So, we may be back to my original guess, a problem arising from mating the Trent 500 core to the Trent 800 fan section.]

(6) At Last! By great good fortune, someone else has taken up the Sesquicentennial project. Disunion is a new feature over at the New York Times, updating several times a week. This is almost assuredly by chance, but I am simply delighted. Not just because I'm happy not to be doing this alone anymore, but for another set of perspectives. As I've said before, I've got the background to analyze the strategy, tactics, and such; but there are gaps in my education I don't know how to fill. This will be a tremendous resource for those of us interested in peering back a century and a half at our greatest crisis.

In any event, we've come to the end of yet another election season. It was a good one for some, a bad one for others. Either way, there's another one coming in two years' time. That's the great thing about our system. It's never completely, finally over. You always get another chance.

Video Del Fuego, Part XXVI

Presented for your viewing pleasure, ten of the best high-speed passes ever, each of which proves that "Maverick" from Top Gun was, in fact, a sissy.

Air France 447

Very bad news Monday: Air France flight 447, an Airbus 330 enroute from Rio de Janeiro to Paris, went down in the Atlantic Ocean between South America and Africa. We may never know exactly what happened. The "black box" lies under 11,000 feet of water just east of the Mid-Atlantic Ridge, and will be very difficult indeed to locate, much less recover. But although the details may never be known, I think we have enough information to know the broad outlines of what happened.

Here is the sequence of events, such as we know them as of Tuesday evening:

1) 0133 UTC: Verbal contact with crew at waypoint INTOL.
2) 0210 UTC: First ACARS message, indicating disconnection of the autopilot.
3) ~0210 UTC: Second ACARS message, indicating mode transition of flight control system.
4) ~0212 UTC: Series of ACARS messages indicating failures of the air data computer and the standby instruments.
5) ~0212 UTC: Series of ACARS messages indicating failures of two of three flight control computers.
6) 0214 UTC: Last ACARS messages, indicating electrical system failure, and failure of cabin pressurization.

There's been a lot of discussion about lightning. I tend not to give it much credence. Modern jet aircraft are designed with the full knowledge not that it might get hit, but that it will get hit. They can take one hit, maybe more than one, and still recover full function. So, something else had to have happened.

Tim Vasquez, a former Air Force meteorologist, has a detailed analysis posted on his site. He overlays the flight path of AF447 onto a time-lapse of satellite weather data, which shows clearly that AF447 was flying over some pretty strong thunderstorms. One of the things in the time-lapse picture that pops out at you is a very strong updraft at 0200 UTC, just to the left of AF447's projected flight path.

Flying over thunderstorms is something commercial pilots do all the time, but none of them really enjoy doing it. Somewhere in the southwestern US, hanging over the base ops building, was a sign that read "There is no reason to fly through a thunderstorm in peacetime." Pilots are trained from day one to respect the authority of His Imperial Majesty, Cumulonimbus Rex. Modern storm-avoidance radars, standard equipment on passenger jets, make the job of avoiding dangerous conditions much easier. But still, things can -- and do -- sneak up on you. The weather radar doesn't have a 180-degree field of view. The specifics vary depending on model, but they can only "see" a cone out in front of the aircraft. Under most conditions, that gives a pilot plenty of warning. But, if a fast-developing updraft gets started right after your radar sweeps over it...

The sequence of the ACARS messages was the last piece in the puzzle. I may be wrong, but based on what I know, this is what I think happened.

The aircraft was upset by a very powerful updraft. We don't know exactly what attitude the aircraft was pushed into, but we do know that the autopilot kicked off. They're designed to do that automatically, if the angle of attack or the angle of sideslip get too high. Further, if the aircraft deviates far enough from nominal values for AOA and sideslip, the flight control computer will switch into an emergency mode, giving the pilot more control authority so that he can right the aircraft. Sometimes, that's enough. But the really nasty thing about unusual attitudes is that the data the air data computer relies on to feed the flight controls becomes corrupted. One by one, the flight control computers drop out as they encounter exceptions they weren't coded to handle. In an aircraft with fully fly-by-wire controls, this is fatal. Without a computer to translate his stick motion into control commands, the pilot cannot control the airplane. Inertia takes over. Inevitably, the stresses on the airframe become too great, the structure fails, and the airplane disintegrates.

If they can recover and analyze enough of the debris, that might tell a different tale. I hope they do, and they can. Maybe there's a clue in there that will tell us how to avoid the next accident. Or maybe not. One thing that strikes me sometimes as I drive past an airport and see airplanes sailing gracefully through the sky in exactly the way a hundred tons of aluminum shouldn't ... You've got to know, there's a risk in doing this. It's a small one. It's one we work hard to minimize.

But it'll never, never go away.

[Addendum, 10Jun09: Well, the danger of early speculation is that you end up getting details wrong. It's beginning to look like icing may have played a role. Ordinarily, the air up at that altitude is so cold that supercooled water cannot exist, and icing generally isn't a danger. But a sufficiently strong updraft might be able to haul enough moisture skyward to ice up some exposed surfaces ... such as the pitot tube.

[Airplanes have used pitot-static systems for years to measure airspeed and altitude. Indeed, until fairly recently, they were the only way to measure them. If your pitot tube ices over, you're essentially blind. But, they have heaters that can melt the ice off, provided that they've been turned on. Now here's where it gets interesting. Modern airplanes also have inertial navigation systems, that use a different method to compute speed. You no longer lose all of your information in an ice event ... but which set of information does your air data computer believe? And which set does it show the pilot? Is the pilot flying according to one airspeed, while the computer ciphers out the control laws in another? That can't possibly end well.

[The interesting thing here is that Airbus appears to have anticipated this particular corner, and has had a fix available since January. The upgrades had been propagating through the fleet with no particular urgency. I expect the urgency to step up a notch or two...

[I have to hand it to the engineers at Airbus, though. That was fast work, figuring out what might have gone wrong from fragments and scraps of error messages. It's in the finest traditions of our profession, and accelerated upgrades may well save lives in the future. Well done, gentlemen!]

Great Moments in Aviation, Part IX

As I wrote earlier, the pioneering age of aviation ended at or around 1910, once the airplane had assumed its now-familiar form. A new chapter opens in the fall of 1914, as an assassination in Sarajevo plunges Europe into war.

But the story isn't quite the one you'd expect. Conventional wisdom has it that wartime is a great spur for technology. This is mostly true. It does tend to focus the mind, and you get more immediate feedback as to what works and what doesn't. An active enemy is the harshest critic of performance that you'll ever find. But by and large, although the airplanes of 1918 were substantially faster and more powerful, they still employed the same basic ideas that they had in 1914. Granted, you do see the first all-metal frames used during WWI. But the most striking innovations were in the uses of the airplanes themselves.

You see, going into WWI, no one had the remotest idea what these newfangled contraptions were good for at all, if indeed they were good for anything.

But there was one immediately obvious application. Flying high above the trenches, a pilot could see for miles. He could see the disposition of the enemy forces in a way that no ground-based scout could. Almost overnight, aviation co-opted cavalry's centuries-old job of scouting and finding the enemy. Airplanes with camera-equipped observers became a common sight over the front. For the first time, generals had something close to a God's-eye view of the battlefield. Not that it did them a whole lot of good, since they had no real notion how to go about attacking a prepared position defended with machine guns. They tried, both sides, with the result being appalling slaughter and stalemate. But still, the observers flew above it all, capturing it on film.

Enemy planes flying overhead are never a good thing. Immediately, people began to talk about how to keep that from happening. You want your guy to be able to do it, but you want to deny that capability to your enemy. So, one fine day, a pilot took a pistol aloft with him, and tried to do something about it. Or so the story goes. I think it had to have been an observer. With a pilot, one hand and both feet are pretty much busy full-time; a pistol-waving pilot is either shooting left-handed or trying to fly left-handed. Neither one is liable to end well. Anyway, the pistols-aloft experiment pulled up a big fat zero, but the basic idea was thought fairly sound.

The next iteration was to mount actual machine-guns on the airplanes. Two variations were tried, with varying degrees of success. Two-place scouts were modified such that the observer had a swiveling machine-gun mount. In theory, this would give him a wide field of fire. In practice, he was as likely to shoot his own tail off as hit an enemy airplane. The more successful configuration involved taking a fast single-seater, and mounting one or two machine-guns facing forward. The pilot aimed his guns with the nose of his airplane. This was the configuration adopted as standard for pursuit airplanes. Pursuit airplanes' primary mission was to interdict enemy scouts, but quite often pursuit airplanes ended up skirmishing with each other. The best of these pilots became famous: Richthofen, Voss, Foch, Rickenbacker.

Another idea that was tried out early on was dropping explosives out of airplanes. The first bombing experiments were shockingly crude. Basically, the observer carried a few up with him, and then held them out over the side to drop them. They hit the ground every time. Beyond that, the system's accuracy left much to be desired. Then someone hit on the idea of carrying the bombs underneath, with a release mechanism, so that they could be aimed somewhat better. This was a distinct improvement. The early bombers couldn't hit as hard as artillery could, not even close, but the crew could see the target in real time. Meager as their bomb load was, they played a non-trivial part in the Saint-Mihiel offensive late in the war.

Although both sides went into WWI not knowing what to do with aviation, by the time the war was over, the basics of air war doctrine had been set. Three of the basic four functions of airpower had been defined: reconnaissance, air superiority, ground attack. Only transportation hadn't been seriously attempted yet. But it would be, and soon. The 1920s would bring a series of innovations that would make the airplane a lasting part of the civil economy.

Great Moments in Aviation, Interlude

By 1910, when Alberto Santos-Dumont built the Demoiselle, the basic form for all airplanes to follow had been set. There would be a few variations, but from then on, most would follow the same basic plan.



The obvious question is: why? Why this shape, and not another? The answer is that, in engineering, form follows function. To illustrate this, we'll compare the standard layout with the Wright Flyer layout, which we saw last time.

The Wrights had decided that control was the central problem, and therefore built their fliers to be very maneuverable. An unfortunate consequence of this was that the Wright designs were all statically unstable. This is a good thing from a maneuverability standpoint. Since the vehicle doesn't really want to fly straight and level, it's always ready to respond to a pilot command to do something else. But if you do want to fly straight and level, it takes a lot of work to keep it that way. So, the Wright fliers were easy to steer, but hard to fly. (An unstable aircraft might well be impossible to steer or fly. It all depends on the details.)

The European pioneers, on the other hand, preferred designs that produced stable gliders. That is, they would glide straight and level without any need for a pilot on the loop. This greatly reduces a pilot's workload in straight and level flight. Although they were harder to steer, they were much easier to fly.

By 1910, designers knew well what features of an airplane's design conferred the stability that they desired. In the pitch axis, you design for static margin. In the roll axis, you design for dihedral. Passive stability is relatively easy to achieve in the yaw axis, with the placement of the vertical stabilizer. (In practice, yaw and roll axes tend to be tightly coupled, and you really can't analyze them separately. But these illustrations still suffice for a basic explanation.)

Static margin is simply the difference between the location of the plane's center of gravity and the location of the plane's center of lift. Designers like for this to be a small, negative number. The reason they want it negative is that a negative static margin confers resistance to pitch-up gusts. If you tilt the nose slightly upwards, and the CG is ahead of the center of lift, then the natural tendency of the nose will be to fall back to neutral. But because you've built in a nose-down torque, you need to design the horizontal tail to provide negative lift, so that there will be no tendency to rotate in the cruise configuration. This also provides stability if you experience a nose-down gust, since the horizontal tail will produce more lift as the nose points downward, providing a net nose-up torque, again tending to reset the pitch attitude to neutral.

Dihedral has to do with the tilt of the wings of the airplane. This is easiest to see in low-wing monoplanes.



This configuration benefits roll stability. With slightly upswept wings, a low-wing plane will tend to roll back to vertical if upset in roll to the left or the right. The lower wing will produce a greater vertical force than the higher wing, providing the restorative torque. This also induces a side force that the pilot will have to counteract with a bit of rudder. High-wing monoplanes generally have little actual upsweep to the wings. Since the center of gravity is usually below the wing plane in this case, there's a pendulum effect that basically does the same thing, restoring the airplane to the horizontal with little extra effort on the pilot's part.

The placement of the vertical tail is perhaps the simplest and most obvious thing. The vertical tail is in back for the same reason that fletching is on the back of an arrow: weathervane stability. If you tried to shoot an arrow backwards, what would happen? The very first gust that pulls it off-center will pull it farther and farther off-center, until it's flying with the fletching in back again. Once designers realized this fact, no one ever seriously contemplated doing it any other way.

In my opinion, the year 1910 brings to a close the first chapter in the history of aviation. It was, in a sense, the end of an era of innocence. The pioneers all looked forward to a peaceful future, one where ever-advancing airplanes would knit mankind's far-flung civilization ever closer together with bonds of peaceful travel and commerce. None of them foresaw what lay only four years in the future, nor would they have believed it had anyone told them.

In 1914, the airplane would go to war, and the second chapter of aviation's history would begin.

Great Moments in Aviation, Part VIII

The story becomes somewhat crowded between 1896 and 1906. The year 1896 saw three pivotal events in aviation history. Octave Chanute brought together several glider enthusiasts on the shores of Lake Michigan, testing various kinds of gliders. Later that year, Otto Lilienthal died in a glider crash. And an American scientist, Samuel Pierpont Langley, built and flew a small unmanned heavier-than-air flying machine powered by a small steam engine.

Langley was, at the time, the founding director of the Smithsonian Astrophysical Observatory. In the 1890s he began research into the problem of powered flight. His first attempts were duplications of Alphonse Penaud's work with gliders powered by rubber bands. He was never entirely successful duplicating Penaud's results, but was successful enough to continue his own avenues of research. Langley focused on the problem of power, pushing to develop ever more powerful engines. In November of 1896, one of his powered machines took off and flew for 5000 feet. His success earned considerable recognition. In 1898, he received grants from both the War Department and the Smithsonian to develop full-scale manned versions of his Aerodrome. He soon abandoned steam engines in favor of the new internal-combustion technology. Over the next five years, he would refine the design of his Aerodrome, and that of its engine. Charles Manly and Stephen Balzer developed a 50-horsepower engine for use in the full-scale Aerodrome. In October 1903, the Aerodrome was ready for its first flight.



Or so they thought. Charles Manly took the controls for the first attempt. The Aerodrome, you see, didn't have a landing gear. It was launched by catapult. And Langley chose the Potomac River for his flights, for the stillness of the air. The Aerodrome, then, would reach flight speed by catapult launch off of Langley's houseboat. On the first attempt, a wingtip caught the edge of the catapult, sending the Aerodrome into the Potomac. Manly managed to extricate himself from the wreckage, and swim back to the houseboat. They also managed to salvage most of the wreck, and rebuild the Aerodrome in time for another test on December 8th. (Oh, so close, so close...) But the second test fared little better than the first. The Aerodrome cleared the catapult fine. But the Aerodrome immediately experienced what we now call "wing torsional divergence", and basically disintegrated in mid-air. Manly was once again dunked into the Potomac, along with what was left of the Aerodrome, and once again managed to swim to safety. Manly was 0-for-2, and promptly retired from the test-pilot business. The War Department was singularly unimpressed by these results, and terminated Langley's funding. One of Langley's assistants, Glenn Curtiss, made numerous improvements and upgrades, and eventually flew a heavily modified Aerodrome in 1914, somewhat salvaging Langley's reputation. But they missed their shot at being first to fly, by little more than a week, as it turned out.

Wilbur and Orville Wright also took up the challenge right about this time, in the late 1890s. They first became interested in roughly 1896, when they learned of Chanute's glider experiments at Lake Michigan. They began to study up on what had been done so far, and in May 1899, Wilbur wrote the Smithsonian Institute with a request for information and publications on aeronautics. Their study led them to believe that the key problem to be solved wasn't power so much as it was control. Provided that you could build a glider that was fully controllable in all three axes, you could always put an engine on it and fly. Their key innovation was their development of wing-warping for control. They noticed that birds in flight would control their direction by changing the orientation of their wing-tips, and sought to mimic this method in their biplane gliders. It proved to be quite successful. Within three years, they developed a very efficient and very controllable glider. In 1903, they began work on integrating an engine into this design. The engine they ended up with was a very small 12-horsepower engine, but very lightweight. In December 1903 they were ready to give it a try. On December 14th, the flipped a coin to see who would try it first. Wilbur won the coin toss, but the flyer stalled immediately after takeoff and sustained minor damage. Three days later, after repairs, Orville Wright took to the air, and flew under power and under full control for 120 feet.



Although they were first, the cautionary proverb "be careful what you wish for" is very relevant to their lives after that first flight. They undoubtedly built the first powered, fully controllable airplane. Also undoubtedly, they built the first airplane capable of flying a full 360-degree turn while airborne, which they did in 1906. But their technical success did not always translate into business and financial success. The Wrights had a well-documented penchant for secrecy that made them extraordinarily difficult to work with. They were mortally afraid of giving away their secrets. Most of their time and energy were consumed in battles both over their patents, and with the Smithsonian over credit for the first flight. Neither of them really had time anymore to devote to further work on their actual product. Wilbur died of typhoid in 1912, and Orville sold the company in 1915.

The last of the three major pioneers at work in the late 1890s was Alberto Santos-Dumont. Many Americans will have never heard of him. But if you think about it, there's something very curious about aviation nomenclature. Why, if the first powered airplane was invented by an American, do so many airplane parts have French names? Aileron, fuselage, empennage, and so on ... Well, it's because the world didn't stand still while the Wrights were tied up with all of their legal death-duels. And Santos-Dumont was largely responsible for the popularization of aviation in Europe.

He came late to heavier-than-air vehicles. In the late 1890s, he started building dirigible balloons. That is, hydrogen balloons that mounted both engines for thrust, and movable vanes for directional control. It wasn't a particularly uncommon sight to see Santos-Dumont flying over Paris at rooftop level, sailing over the streets under full control, occasionally stopping at fashionable outdoor cafes for lunch. In 1901, he won a 100,000 franc prize for flying from the Parc Saint Cloud to the Eiffel Tower and back within 22 minutes. After this, he began to turn his attention to heavier-than-air vehicles. In 1906, his first successful design, the 14-bis, flew in full view of the public in France. This became the first flight that was certified by an independent body, the Aero Club de France. His career as an aviator was sadly cut short, though, when he fell ill with multiple sclerosis in 1910. But he had inspired several other Europeans to follow suit, including such aviation pioneers as Louis Bleriot, Louis Breguet, and Henri Farman.



Alberto Santos-Dumont is also notable for another reason. When he was making his record-setting flights with his Number 6 dirigible, he noticed that he was having considerable difficulty consulting his pocket watch for time checks. In any kind of flying machine, one's hands are usually both busy at once, and generally a pilot seldom has a hand free for yanking out a pocket watch. Santos-Dumont took his problem to jeweler Louis Cartier, who devised a simple solution. Ladies had been wearing tiny watches on their wrists for years as jewelry. What Cartier did was to take a small pocketwatch, and affix a leather strap to it so that Santos-Dumont could wear it on his wrist. Then, he could check his watch without ever taking his hands from the controls. Overnight, the multifunction chronometer became the trademark of the aviator. Fashionable gentlemen began to wear them as well, and today the wristwatch is practically ubiquitous.



Today's watches have a few refinements that the originals lacked. Mine, for example, has an E6B flight computer built into the outside dial. It's a circular slide rule you can use to find out how much longer it will take to reach your destination, whether you have enough fuel to make it, and it also has a few built-in unit conversions. It's also useful for figuring tips. I found it curious, though, that wristwatches only became popular in the last hundred years, give or take.

In any case, after Langley, the Wrights, and Santos-Dumont the feasibility of manned heavier-than-air flight had been proven beyond all doubt. Incremental improvements would be made over the next ten years or so, leading to airplanes flying faster and higher, and even capable of carrying a useful load. The next big jumps would take place about ten years down the road, although not necessarily when or where you might expect.

Great Moments in Aviation, Part VII

We are coming to a point in the story where everything seems to be happening at once. That is mainly due to the fact that none of this is happening in a vacuum. For most of aviation's history to date, progress has been due to the lone work of a genius here, a tinker there, all working in isolation. This would all change in the 1890s. And in my opinion, that change is mostly due to the work of one man: Octave Chanute.

Octave Chanute was a French-born engineer who had already made a name for himself working on railroad and bridge projects all across America. He came to an interest in aviation relatively late in life. In 1890, he retired from his rail and bridge practice to study aviation full-time. He spent the next several years studying everything he could find about the subject, and in 1894, he published the first comprehensive index of aviation research to date, Progress in Flying Machines. Also, in 1893, he organized an aviation conference at the Columbian Exposition. Chanute had won enough respect for his earlier work that he could not be dismissed as a crackpot. If as eminent an engineer as Chanute thought it possible, well, there's probably a decent chance that there's something to this "flying machine" stuff after all...

One of Chanute's more important contributions was the refinement of the biplane form. He applied his bridge experience to the problem, and devised a structural bracing system that was both strong and lightweight.



But his most important contribution by far was the fact that he maintained a correspondence with everyone who was anyone in the field. He shared everything he knew freely, encouraging other experimenters to take up ideas that he'd had. Ideas began to fly thick and fast. Blind alleys were quickly identified and cut off. Gliders were built with successively better and better control methods. By the turn of the century, several projects were underway that could result in the long-sought flying machine. It was no longer a question if man would fly. The question became who and when. Three of Chanute's pen-pals were in the running. All would eventually succeed, but only one of them could be first.

Great Moments in Aviation, Part VI

(Editor's Note: I'd meant to continue this series last week, but I forgot that it was Tour of California time again. For those of you who care, Levi Leipheimer won his third straight Tour of California. It was also Lance Armstrong's first USA appearance since coming out of retirement, and Floyd Landis' first race since finishing his suspension. It's four months and change 'till the big race kicks off on July 4 in Monaco. It's the Return of the King, baby! Be there!)

When we last left our story, Sir George Cayley had just made a key realization that would ultimately pave the way to controlled, powered flight: the functions of lift, propulsion, and control must be separated in order to be made practical. The half-century separating 1853 from 1903 would see each problem attacked in turn, with varying degrees of success. Truly, we're still contending with them. We're always finding better ways of doing things, and cannot consider these things "solved" even now.

But the obvious thing to do in the latter half of the 19th Century was to study gliding flight in detail. And by far, the biggest name in gliders would have to be that of Otto Lilienthal. Lilienthal made over 2,000 flights with his gliders between 1891 and 1896. He became sufficiently skilled that he could use an updraft against a hill to hang seemingly motionless in the air, with respect to the ground.



The key differences between Lilienthal's gliders and Cayley's original design is first that Lilienthal eliminated the "basket" that Cayley's reluctant passenger rode in, and also that Lilienthal's wings were of a more advanced design. He spent a considerable amount of time studying the gliding flight of birds, especially storks, making detailed aerodynamic diagrams. Today, we call such plots lift polars and drag polars. The data he gathered drove his designs. Among other things, he was the first to build biplane gliders, which gave twice the lifting surface for the same wingspan, and also a more rigid wing structure. He also experimented with a movable elevator for improved pitch control.

His remarkable feats of gliding brought him worldwide fame. Unfortunately, they were also his downfall. On August 9, 1896, he lost control of a glider, falling more than fifty feet to the ground. He broke his spine, and died of his injuries the next day. A grievous loss, but yet not in vain. He gave everyone who followed a firm foundation on which to build. True controlled flight was scarcely more than seven years away.

Great Moments in Aviation, Part V

Meanwhile, across the English Channel, big things were also happening in England at the end of the 18th Century. The next important development in flight involves a man who is the most important figure in aviation that you've probably never heard of: Sir George Cayley.

Cayley was probably the first figure in aviation history to go about it in a scientific, systematic way. He spent a lot of time in the early 19th Century testing different wing shapes, finding out which ones worked best. He tested different configurations of wing and tail. His experiments led him to develop an efficient cambered airfoil, and he also discovered the beneficial effects of dihedral on a glider's stability. He set all of this out in his three-part treatise "On Aerial Navigation", published between 1809 and 1810. But, most importantly, in 1799 he etched this drawing onto a silver disc, preserved in the Science Museum of London:



The important thing about this image is that here, Cayley clearly separates the functions of lift, propulsion, and control. Prior flying machines attempted to do all with a flexible bird-like wing. This is the key conceptual breakthrough that eventually made powered flight feasible. Propulsion was a problem that Cayley never did solve, though. Although he experimented with gunpowder-fired internal combustion engines, they simply did not provide enough power-to-weight to make a flier work. He then turned his attention exclusively to gliders.

His diligent research paid off, though not quickly. He did not build a full-size man-carrying glider until 1853. But in 1853, man finally experienced gliding flight. It was a short flight, close to the ground, and nothing like soaring with the birds. Not yet. But a gigantic step had been taken.

Great Moments in Aviation, Part IV

Taking up the thread again in Western Europe, the story takes an unexpected turn when Joseph-Michael and Jacques-Etienne Montgolfier start fiddling around with the odd properties of hot gases.

I say "unexpected" because, although people had been gazing at birds and wondering for as long as humanity had existed, no records exist of anyone imagining the lifting power of hot air until November of 1782, while contemplating an assault on the British-held fortress at Gibraltar.

Gibraltar: it had been ceded to Britain by the 1713 Treaty of Utrecht, and it commanded the western end of the Mediterranean Sea. Needless to say, this was a major thorn in France's side. Assault from the seaward side is simply suicide. There are no beaches. The only harbor is well-covered by artillery from above. And the only approach from the landward side is narrow, and just as easily covered. As badly as the French wanted Gibraltar, well, they could want in one hand and spit in the other. Guess which one fills up first?

Which drove Joseph to wonder: what if there was somehow a way to approach from above? Say, if you could harness the lifting power of the smoke that headed up from a fire? There was no way for artillery to fire high enough to cover that approach. What a fine thing that would be ...

This might have gone the way of most idle thoughts, if the Montgolfier family hadn't been experts in cloth, paper, and wood. Joseph had exactly the right skills and materials to build a small proof-of-concept device that, when held over a fire, promptly sailed up to the ceiling. Once he showed his brother, well, there was nothing for it but to build a full-scale version that could carry the both of them.

About a month later, on December 14th, 1782, the brothers took their first balloon aloft. They lost control, not expecting the lifting force to be so great, and sailed one and a quarter miles across the countryside before making a safe landing. Larger balloons followed, as well as public demonstrations, until in September of the next year they made a demonstration at Versailles for King Louis XVI and Queen Marie Antoinette. Their fame, and fortune, had been assured.

Hot-air ballooning would become a dead end, though, since hot-air balloons are inherently limited by the cooling of the trapped gas. Hydrogen balloons were developed in parallel, and in competition with, hot-air balloons. Hydrogen balloons would come to dominate ballooning for the next 180 years, until helium became available in quantity.

Nevertheless, hardly anyone remembers the inventor of the hydrogen balloon. The Montgolfier brothers were first past the post, and are therefore enshrined as history's first balloonists.

Great Moments in Aviation, Part III

Lest we think that Western Civilization was having all the fun, we turn our attention to China in the 16th Century. The Chinese had invented gunpowder, and rockets. It's only natural for an inquisitive soul to imagine using rockets' power for flight. But that's a road fraught with peril, as poor Wan Hu found out the hard way.

Gunpowder rockets are, by modern standards, fairly simple devices. But they were absolutely cutting-edge state-of-the-art in the 16th Century. Heretofore, rockets had no use aside from fireworks and antipersonnel artillery, but Wan Hu saw potential in them for something more. As legend has it, he had a grand chair constructed, with forty-seven gunpowder rockets built into the base. One fine morning, he sat himself in the chair, and had his men touch off the rockets, sure he was taking a voyage into history. Well, he did, just not in the way he'd imagined.

There are challenges inherent in using rockets for propulsion. The main problem is symmetric thrust. If you want to fly straight, the axis of thrust MUST pass through the vehicle's center of gravity, or else the vehicle will begin to rotate. And once the vehicle falls even a little bit off vertical, its natural tendency will be to fall even farther off vertical, making a bad problem worse. If you've ever tried to balance a pen or pencil on end, you've seen how this works. Most of the other problems are related to maintaining symmetric thrust. All the rockets must start at the same time, and cut off at the same time, for example. They must produce uniform thrust, if you're using more than one. And they must burn in a stable, predictable fashion.

Well ... Forty-seven being a prime number, it's difficult to imagine a symmetric configuration. And with forty-seven lackeys with torches touching off fuses, it's difficult to imagine all the rockets starting simultaneously. And to top it all off, early gunpowder was notoriously finicky. Two rockets made from exactly the same batch of powder, made by exactly the same craftsman, rarely if ever flew the same.

Wan Hu's ride into history was short, but absolutely action-packed. The chair was consumed in a gigantic explosion, and Wan Hu was nowhere to be found afterwards. I suspect the searchers were looking for an intact body, not the small flaming fragments that poor Wan Hu had been blasted into.

It took hundreds of years of work to get it right, but even today riding into orbit on a controlled explosion isn't what anyone would call safe. Next time you watch a manned space launch, raise a glass in honor of the first poor brave soul to give it a try. He didn't go far, but he was the first, and that's worth something.

Great Moments in Aviation, Part II

After the legend of Icarus and Daedalus was first told by the Greeks, many years passed. They were forgotten, then re-discovered during the Renaissance. The next man to pick up the ball and run with it was Leonardo da Vinci.

Da Vinci had a lifelong fascination with, well, damn near everything. He had that remarkable combination of a fertile creative imagination coupled with an intensely analytical mind that could look at a bird in flight and not only wonder how such a thing could be, but deduce more or less how it works. There's scarcely a field of human knowledge at the time he didn't touch, but here, we're concerned with some of his most famous inventions: his flying machines. Interestingly enough, he left enough clues in his work for us to follow his thought process.

His first thought was to mimic birds mechanically.



This is a rather ingenious device that uses pedals to work the wings, which would flap like those of a bird, producing both lift and thrust. But the problem with this design is that a human simply cannot provide enough power to achieve flight this way. Which isn't the same as saying human-powered flight is impossible -- it's been done -- but it can't be done this way.

His second thought was to build a large man-powered vertical screw, with the idea that he could pump air in the same way that a screw of Archimedes pumps water, thus lifting the man airborne. The key thing here is that da Vinci realized that air is a fluid just like water, and thus obeys the same laws. This is a key revelation, one that will be put to great use later. Today, we look at this design and see the precursor of the modern helicopter. This, also, suffered seriously from the limit of man's direct mechanical power. It also suffered from da Vinci's insistence upon providing lift and thrust with the same device. It's his sole conceptual failure in both of these powered designs.

Once he'd given both of those up as bad ideas, his thoughts turned to pure gliding flight. And here, he finally hit upon something that was practical with the technology of his time. Unfortunately, history does not tell us if he actually tried a full-scale test with a human pilot.

Despite never having worked full-scale, though, the designs in his sketchbooks served as inspirations for all the great pioneers of aviation to follow. By documenting what didn't work, he prevented later generations from pursuing blind alleys and false starts. This, too, is progress.

Great Moments in Aviation, Part I

In the Western tradition, the first story about human aviation was the Greek legend of Icarus and Daedalus.

Daedalus had built the Labyrinth for King Minos of Crete. Minos, being an ungrateful and suspicious sort, imprisoned Daedalus in a high tower with his son Icarus. Daedalus got to thinking -- when you're shut up in a tower, you've nothing better to do -- and came up with a very clever plan. He figured that if he couldn't escape Crete by sea, then he'd fly out like a bird. How hard could it be?

So he got a bunch of feathers, and some wax, and made two pairs of man-sized bird's wings. One pair for Daedalus, and one pair for his son. At this point I feel compelled to mention that Daedalus had a wife and another son as well. Had they already escaped? Had he grown weary of their company, and decided to leave them behind? The legend doesn't say. It just says that just before they flew the coop, Daedalus warned Icarus not to fly too high, lest the sun melt the wax of his wings.

And so, they took to the air. The legend says that they passed Samos, Delos, and Lebyhthos -- which is a damned odd path. Those three islands don't lie in any kind of line. If you visit each in that order, then you've basically flown a victory lap around the Aegean Sea, including a pass by Crete between Delos and Lebynthos. Perhaps they flew by old Minos' palace to taunt him as they escaped. Anyway, when they were passing Lebynthos, Icarus was having so much fun that he soared up towards heaven, and exposed his wings to too much sun, and the wings came apart. This left poor Icarus to plummet towards the Aegean from a height where there's not a whole lot of difference between a splash and a splat.

Now, this was meant to be read as a morality tale, cautioning the young and hot-headed to heed the wise words of their elders. The details were never meant to be taken seriously. Nevertheless, it holds a place in my list of Great Moments in Aviation, since it was the first story where men used machines of their own making to take to the air.