Wednesday, June 26, 2013

An Open Letter to Hollywood from an Aerospace Engineer

Short version: you clearly know nothing about how plane crashes happen. Please consult someone who does.

I have seen a number of plane crashes in movies and TV. This really shouldn't be a surprise; they are big, dramatic events, so you can burn a fair amount of your special effects budget (or with some careful use of models and stock footage, very little of it) in a nice dramatic scene.

Problem is, real plane crashes (even of light aircraft, much less the full sized commercial widebodies that the TV and movie industry prefers) are really rare, so people don't have much idea what they look like or what causes them.

Or, more to the point of what triggered this note, what can NOT cause them.

I have now seen it several times (most recently on a TV show): someone gets a firearm (sidearm or one-shot, note, not even a rifle) onto an airplane, and fires a round that punches through the sidewall, often at a window. This causes the sidewall to explode outward, decompressing the airplane and causing it to crash.


First off, there is actually no guarantee that such a round would penetrate all the way to the outside. Possible? Certainly. Probable? Depends on the round and exactly where it hits. A window is, granted, an easier barrier to beat than the sidewall/insulation/skin stack up.

But let's set that aside and say you do puncture the pressure vessel. What happens? Contrary to some perceptions aircraft at cruising altitude are not in a vacuum (if they were they couldn't fly). Nor is an aircraft cabin at full sea-level pressure during such a phase of flight. So there is MUCH less than one atmosphere of pressure difference between inside and outside. How much? Again, it depends. The 787 (which has not yes had a hull loss, much less a crash, that I've heard of and has a MUCH tougher skin) has a measurably higher pressure than other commercial birds out there and is still at less than sea-level pressure at cruising altitude.

Aircraft are designed to withstand depressurization through much bigger holes than even a shotgun with slugs could produce. Nor is the structure so weak that punching a hole will cause a secondary hull loss - again, designed and extensively tested for that. Shooting a hole in a window will break the window, and you will probably loose some of the 'glass' (it isn't) to secondary spalling, but the frame WILL remain. A round through the hull (assuming your bullet actually breaches the sidewall, the insulation, and still hits the skin with enough energy to break it) will expand even less.

So, the aircraft is depressurizing. There will be screaming, oxygen masks will deploy, etc. Will the airplane crash?


The airplane WILL suddenly and (to the passengers) inexplicably dive. It will do so more steeply than anything most passengers have experienced outside of a roller coaster. This will not, however, be the first stage of a crash - it is a deliberate and carefully rehearsed action on the part of the flight crew to get the plane down to thicker air, where there is enough oxygen that people can breath it without passing out. See, those oxygen masks with the teeny little tubes and the bags they tell you may not inflate? That's temporary, supplemental oxygen. If you tried to breath that, and that alone, in a fully oxygen depleted atmosphere you would pass out. That's OK because as noted aircraft by definition do not fly in vacuum. There's always SOME oxygen outside the hull, and the pressure inside even after a full decompression won't be lower than the pressure outside. The oxygen system is designed to keep everyone conscious while the plane makes a worst case emergency descent (which can involve being stuck over the Himalayas and unable to descend to the desired altitude for a while).

So, the plane goes into a (by most people's definition, probably including your stomach's) steep dive for a few minutes, then... it levels off. Wow, we're really low now, we must be in danger of crashing if the pilot makes a mistake, right?

Wrong again. You're "low" by commercial cruising standards. You will, in fact, dive to under 10,000 feet. You might very well go down to 5,000. Plenty of margin for error.

So... we're fine?

Well, the pilot will have declared an emergency and will be looking for the nearest place to land before you even figure out what's going on.

Oooh! Emergency! So we're in great danger?

Again, sorry, no. You're in potential danger, and that's far too much for the FAA to allow. Commercial aircraft are designed to withstand any single failure without crashing (if you don't believe me, look up how many commercial widebodies have crashed throughout aviation history - and note that the worst aviation accident was on the ground!). By decompressing you've had one failure and used up your design margin, so you now have to land since the aircraft MIGHT not be OK if something ENTIRELY UNRELATED TO THE FIRST INCIDENT happened. Anything related to the first incident? We designed for that. Again, look at the crash statistics. We're good at designing for stuff.

So you CAN'T bring down a plane with a pistol?

Well, I can't say that, but your best odds are to shoot the pilot in the back of the head (while the autopilot is off, mind, which isn't for much of any given flight) and cause the co-pilot to panic for a minute, allowing the plane to get into an out of control condition which he can't recover from. Note that modern cockpit doors are "bullet proof". (I make a habit of using the quotes because it all depends on the bullet - a .50 BMG will hole a remarkable number of "bullet proof" items, but smuggling something that will fire THAT onto an airplane is beyond even my abilities. Yes I know how to smuggle a firearm onboard an airplane, I choose not to and I'm not going to say how on the internet.)

Huh. What if I shoot an engine?

Good luck. We design not only to fly on one engine, but to fly after one engine EXPLODES. Granted, that's a tough one, and especially if you were low at the time the pilot might not be able to recover. You still get better odds by shooting the pilot, though getting into the cockpit is non-trivial.

Uh... control cable?

Oooh, you did some homework! Yes, those cables (slowly becoming just more electrical wires) that turn the pilot's actions into flap, rudder, etc. movements are very imported for continued flight. Thus they are protected, dual-control, or can be worked around. A failure of a control cable would be a "single failure" so, say it with me! We designed for it. Besides, are you holding a set of blueprints while you aim?

Fuel tank?

Hollywood does like the "shooting a gas tank makes it explode" idea. Pity that's actually a low probability event (look up Mythbusters). Punching a hole in a tank does not inherently produce a spark to make fuel ignite. In fact we work VERY hard to ensure that there is nothing in or around a fuel tank that CAN make sparks (special coatings on fasteners, grounding wires all over the place, etc.). Bullets are typically made of lead and copper, neither of which is great for making sparks.

Despite our best efforts, accidents happen and people die. Over the years, however, we've made flying miles above the ground in an aluminum can filled with fuel, electronics, and other hazards safer than walking down the sidewalk. Again, look at the list of commercial widebody crashes. Note that the top ten usually includes the Tenerife incident, which was a ground collision, and a 2003 crash in Iran which was an IL-76 (a Russian design - the Russians just aren't as good as we are). You'll also usually see TWO losses to anti-aircraft missiles in the top 20 (Iran Air 655 in 1988 and KAL 007 in 1983). Sorry, we can't design for that. Depending on the list you may see 9/11. While the TSA is unlikely to stop another such attack, hardened cockpit doors and improved crew and flight procedures (thank you FAA, not TSA) will make such an attack VERY hard to replicate.

But even counting all those things that engineers can't design for, look at the list in total, no exceptions. Now look at the number of fatalities from car crashes, or from private aviation, every year.

We design well. Hollywood please take note.

Tuesday, June 25, 2013

From the Front Lines: June Faire

June Faire was the first weekend in June.

Yes, I'm more than a little behind on posting.

I participated in the 1st may become annual bardic competition of June Faire. It was a fairly standard head-to-head, fixed topic, contest. I did King Rorik for "War" and Dulcinea for "Love" and lost both rounds. Sigh. To be fair, there was some excellent competition out there. For one thing, there were bagpipes. I had never heard the Star Wars theme on bagpipes before, but now I have. :-)

I spent most of my time, however, with the Moneyer's Guild. Yes, that means 'almost all the time the Faire was open Saturday and about half of Sunday.' We were doing the fund raiser thing again, and I spent most of my time doing the demo/sales pitch.

We did take a little time Sunday, however, to give three of us (myself included) our Journeyman's Oaths. I am now a Journeyman of the Moneyer's Guild of An Tir. :-)

Monday, May 13, 2013

Scotland, Day 11

Homeward bound again.

I carefully collected Italian coins when I went to Italy, and naturally enough I decided to collect some UK coins in Scotland. I carefully sorted my coins to keep examples of each major minting (not each year, just head/tail combinations).

The US gets along with the penny, nickel, dime, and quarter plus slowly increasing use of dollar coins. Yes, we have $0.50 pieces and a few other oddities but they are rare.

In common circulation the UK has 1p, 2p, 5p, 10p, 20p, 50p, one pound, and two pound coins. They do not use one pound notes – the smallest paper money is a five. Paper notes, BTW, are not only issued by multiple mints but given distinctly different appearances by those mints. The Banks of England, Scotland, and Wales all issue currency. I expect this accounts for some of the variety in coins, as well. All the currency I took over was Bank of England, but much (though not all) of the paper change I got was Bank of Scotland. Anyway, back to coins.

The US has state (and now territory and national park) quarters.

In the UK I collected 31 different one pound coins, ignoring year marks.

The one pound coin is a solid hunk of metal – about the same diameter as a quarter but twice as thick. It is, notably, thick enough that they print words on the edge. This process must be at a different stage than the stamping, however, since the text shows up both ‘right side up’ and ‘upside down’ relative to the obverse/reverse. Three different faces are in use (all of Queen Elizabeth, just different portraits) and over a dozen different backs; about half of these had multiple faces, indicating a long minting history.

I bought two bottles of whiskey at the duty-free store, brining my total inbound load to just under four liters in eighteen containers. Yes, I declared it at US customs.

While at Heathrow I also saw my first A380 in person. I admit to prejudice, but they look like big ugly birds to me. The 747 which carried me back to Seattle is a much prettier aircraft.

British Airways served a tasty meal and 'high tea' on the return leg, which according to departure and arrival times was only an hour long. Ah, the fun of time zones. I managed to watch several movies in that hour.

Speaking of US Customs, three uniformed and two plainclothes CBP officers (granted, the latter could have been anything from local detectives to FBI – I can’t read plainclothes THAT well) were waiting on the jetway for the flight. A wall of uniforms at the official “border” I expected (and got), but five LEOs on the jetway makes me think something unusual was going on. What, I will probably never know. Entry into the US involved more paperwork than entry into the UK but no questions at all (OK, returning citizen vs. entering foreigner – I still expected more hassle on the US end). It seems reasonable to conclude that whatever caused five cops on the jetway had the rest of the CBP focusing on other things too, and uninterested in me.

All in all it was a marvelous trip. Not flawless, to be sure, but if I was offered the chance to do it all over again, flaws included, I would.

What more can one say?

Thank you Scotland for bagpipes, whiskey, dancing, and just being a blast in general.

Saturday, May 11, 2013

Scotland Day 10

American tourist move of the day: needing to buy a piece of luggage to get all the souvenirs home.

Britishisms: too many to count. Heck, I found myself slipping unintentionally into a vaguely Scottish accent at one point…

Look, one of my suitcases was on its last legs anyway, OK? Yes, I most certainly DID leave room in my bags on the trip out for expected souvenirs.

I just didn’t leave nearly enough. Even with another bag it was a tight squeeze.

The American Contingent spent yet more time with the newlyweds. Notably, six of us went to the Scotch Malt Whiskey Society.

The SMWS is not a normal bar, nor do they even have a normal selection of whiskey. All the bottles behind the bar are the same shape, color, and have labels in the same pattern. The labels do not bear the names of distilleries, they bear numbers. And almost every one of them contains cask-strength single malt Scotch.

Cask strength means that the whiskey has not been cut with water (a normal step in the bottling process) after it is taken from the cask it was aged in. Thus while normal whiskey is ~80 proof, cask strength is ~120 proof.

I had assumed that something with that high an alcohol content would overwhelm the flavor. Laphroaig had already corrected that impression.

The SMWS showed me what I’d been missing. Cask strength not only gives fuller flavors, it makes it easier to pick out the subtle flavors one often sees listed on the better grade of whiskey. I suppose a connoisseur might find this like hitting a tack nail with a sledgehammer, but I do not have that refined or trained a palate. Four of us were drinking, and each of us ordered three drams, with much exchanging of tastes.

You might wonder how we decided what to order, there being only numbers to order by. Well, each number has a description. Not a sentence or two on the side of a bottle, a long paragraph of whimsical text which is as likely to note a hint of gasoline, or advise you to call to mind a Christmas dinner, as it is to mention a ginger finish. Names are applied, but no boring distillery name – “An enticement of sweet oak.” “Heather honey and burnt toast.” “Doctors’ surgeries and flower shops.” Drams are placed in one of 11 categories based on cost. This range from ~$7.50 for a Green Dram to about $50 for a White Dram, not forgetting the Copper Dram (which is more than the Gold Dram) or the Tartan Dram. I think whoever made the list had a few too many drams in their system at the time.

Sadly, they were out of “Below the Decks of the HMS Britannia.”

They do tell you the region (Speyside, Islay, etc.), the cask type, and so forth, in addition to the more entertaining elements of the description. For that matter, crowdsourcing has provided an app which you can use to look up the distillery, as part of the number is keyed that way. Without this aid I still managed to order three delicious drams, and I don’t think anyone got one they didn’t like.

I shall be exploring cask strength whiskeys with great interest from now on.

Friday, May 10, 2013

Scotland Day 9

Stirling Castle is in Stirling, and of course Edinburgh Castle is in Edinburgh. No surprises.

Stirling, however, would be at most a medium-sized town in the US. Edinburgh, while not huge, is a real city.

So the effect of a castle sitting on a volcanic plug in what is, basically, the middle of the city is more than slightly odd to American eyes.

Stirling would be a challenge to take, especially pre-gunpowder. I don’t think I’d want to attempt Edinburgh without modern weapons, preferably including heavy artillery. Helicopters flying a NOE approach would be subject to plunging fire from three of the sides.

I almost suffered a casualty on the approach myself – the wind took my hat off and nearly blew it away (and ‘away’ would have been over the edge of a fifty-plus foot drop). Even men in armor would find wind like that a complicating factor in an attack, and apparently it was not an abnormally windy day.

The castle, however, as legend tells it, was taken via a secret passage by thirty brave Scottish warriors who stormed the place and slaughtered the garrison. Modern historians have gently suggested there were probably more like 600 of them, while stipulating all the other aspects. The Scots are known to exaggerate just a wee bit from time to time.

The hill has been fortified since Roman times, though exactly when the first sections of the present structure were built are, once again, unknown.

The castle is home to two notable pieces of artillery. One is Mons Meg (I’m sure Google will provide pictures and history). I will note that one can, and I did, insert one’s head and shoulders fully into the muzzle. That is a Really Big Gun. The second piece of note is even more powerful, though less impressive on the surface and not at all SCA period: a modern 105mm howitzer. This one is still used – six days a week at 1PM it is fired as a time gun. The day it isn’t fired is Sunday. Guess which day I managed to visit?

Edinburgh is on the southern shore of an ocean inlet of the North Sea. One can fairly easily see the north shore from the castle. The tour guides are apparently asked if it is Norway (unreasonable but at least demonstrating some knowledge of geography), France (sigh), and the United States (perhaps someone who visited the Scotch Whiskey Experience on the way up to the castle).

The castle also has a very old, and very small chapel that is still used as such. When I say ‘very small’ in this case I mean that my living/dining room at home is about the same size. You can nearly stretch out your arms and touch two opposing walls on the short axis. Another thing you don’t really get from books or pictures.

Not to be outdone by Stirling, Edinburgh Castle has FIVE giftshops. Admittedly this includes several for separate museums inside the structure. One of these is for the crown jewels of Scotland: the crown, the scepter, the sword, and the Really Big Rock. Technically that last is the Stone of Destiny… but you can’t help looking at this thing and thinking “Really Big Rock.” It is not planed, or some beautiful piece of marble, or in some mystic shape. It is a really big, vaguely rectangular prism, of… rock. It is also the only piece that is still in use – the King/Queen of England is also the King/Queen of Scotland, and the Stone is used in coronations to represent this fact; the monarch sits on a throne with the Stone underneath (in older days the kings of Scotland sat on it directly). It does not look like a comfortable rock, either. This means that part of the coronation planning includes a trip by a heavily armed convoy from Edinburgh to London carrying… a really big rock. The crown, scepter, and sword remain in Edinburgh.

I am of the opinion that this represents relations between Scotland and England very well indeed. “Yes, fine, you rule us, as a reward you may sit on our rock.”

Speaking of the Scotch Whiskey Experience while I did not get the tour I did stop in at their bar. Their bar has approximately 300 (an estimate, not an exaggeration) different whiskeys available (almost all Scotch). Just as an example, six different Auchentoshans, and six different Balvenies. They also have a nice chart which groups the various single malts by flavor. Find your favorite around the edge, push a button to turn its light on, and then see what’s nearby. I’ve already used this (sadly non-interactive in picture format) as a reference back here at home.

A bunch of the wedding guests joined the bride and groom for a tour of Mary King’s Close. A close is a medieval name for a narrow street (a narrow alley, in modern scale). Parts of this one and some of the surviving buildings are now three stories underground. It is done up as a piece of living history – the sort that doesn’t get into the history books. Our guide was a foul clanger (phonetic spelling, there); someone who was paid by the city to interact with plague victims while they lasted. I would have preferred a different choice of ambiance, or if they’d picked a single century and stuck to it, but once again walking through medieval rooms is an invaluable experience for a SCAdian. Some of the discussion of how the plague was dealt with I want to double check, but if correct is a nice bit of period knowledge.

We also joined the newlyweds for dinner, where I once again fooled someone into thinking I was current or ex-military without meaning to. This time it was a retired US Army colonel (surgeon, but still an O-6). I might have a future as a con artist if this ability of mine wasn’t completely unintentional. Also at this dinner I had haggis. I am told it was good haggis. If so I never want to have bad haggis, though I’d be willing to have good haggis again.

I don’t know – sushi, haggis, beer… I think I need to give up my standing conceptions about food. Yeah, the sushi thing happened a while ago (right after moving to Washington). It was still a major alteration in my standing list of likes and dislikes.