31 January 2004 02:56
quoting myself......people get all worried about flying, when driving to the mailbox is umpteen times more dangerous. as a pilot i can testify to this. in the air, stupidity and mechanic failures can kill you, but you have time to recover. true, in landing, you have less time to recover. in my 300+ hours of flying, i've done a number of things that could have killed me. again, God wants me alive. i prefer to call them... learning experiences. but in a car, wow. you're driving, perhaps carelessly, perhaps not paying attention, perhaps aggressively because you're mad. you narrowly miss another car or one of them concrete pillar thingy's they like to put under bridges. bam, the adrenaline flows, you grab a couple breaths, settle down and drive normally. very soon you forget about it...
what have you learned? nothing. it's a commonplace experience, you think little of it. planes are actually very safe. shucks, we do stuff like check the oil before every flight. how often do you check the oil in your car? right, and see how long your car can run without being checked? an airplane engine can go even longer, becuase it is very well maintained. and the ratios are all wacked. an airliner goes down and it's major news, though i just heard of three serious car accidents on the traffic watch segment of the news on my way to work this morning. car wrecks don't make national news until there's been one of LA's famous 73 car pileups. it's somewhat painful to encounter people's naiveness about airplanes. they don't drop out of the sky if the engine quits. people will go up in gliders and soar on the wind currents for hours without an engine. it's because it's got wings. transfer this mental image of soaring to a normal powered aircraft. hey, it's got wings! true, a typical fourseat airplane does not have the glide ratio of a nonpowered glider. but it's still something like 12:1. that means that for every thousand feet of altitude the airplane can travel two miles. for example, if your engine fails at five thousand feet, the pilot has roughly ten minutes before he reaches the ground. in that ten minutes, he can fly ten miles, or farther if the wind is to his tail. but wait, before we impackt in a firey fireball of exploding fire, let's see what he'll do with those ten minutes. first he configures the aircraft for "best glide", the speed at which he can glide the farthest (similar to 55mph in a car, the speed for best mpg). then he'll pick a good spot to land. the observant amongst thee will note my use of the word "land," NOT impackt. but i'll come to that. what causes the engine to stop turning? yes, it could be a failure, but that's not the most common. most commonly, the engine will quit turning because of some inaction or incorrect action on the pilot's part. pilots are human, we're not always perfect (just usually perfect). but tell me, do you ALWAYS remember to signal your turns in a car? do you ALWAYS get the car started on the first turn of the key? do you ALWAYS stop for lights that have been yellow a while? do you ALWAYS leave home with enough gas to make your first planned stop? ah you say, but we can pull over to the side and thumb a ride to a gas station. true, until you run out of gas while crossing say the golden gate bridge, or on a single lane overpass at a huge interchange. then you have concrete barrier to the one side, rushing traffic to the other.. i say this to say that your case is not so clear as you say. but at any rate, pilots do do dumb stuff. we forget to talk to air traffic control occasionally. we have trouble starting the engine sometimes. we break FAA regulations occasionally. we miscalculate our fuel occasionally. are you one of those people who ALWAYS does those things above? good for you. you should be impressed with your perfection. for your information, there are pilots who are almost as close to perfect as you. i am not one of them. so what caused the engine to stop? nine times out of ten, it will be becuase the pilot forgot to "lean the mixture" (something your car automatically does for you), or he forgot to switch tanks (of which your car only has one), or he accidentaly bumped a switch. if it's not that, it could be a common error of another sort, such as ice forming in the carboratour. but now our pilot has ten minutes to figure that out. if any of those four things happened, most pilots could have the engine running again within 60 seconds, or much less. if they're familiar with the airplane, as soon as they hear the engine sputter they would be reminded, "doh!" so they perform the neccessary operation and the engine picks up smoothly, never to actually quit.
okay, so you win, let's say our engine actually dies, let's say it's thrown a few rods out the top of the cowling and the prop grinds to a stop. the pilot's next reaction will depend on whether or not he owns the airplane. if he owns the airplane he's going to say, "ooooooooh maaan. this is not goign to be cheap." if he's renting or borrowing the plane, he's goign to say, "ooooooooh maaan. i hope the owner's got his insurance up to date." then he's going to calmly configure the plane, pick a spot, and head for it. your typical small aircraft--i'm using small aircraft because they only have one engine. anything larger and it's going to have two. one quits, big deal, fly to an airport on the good one--your small aircraft will need less than 1000 feet to land. and that's a nice liberal figure. i know you're goign to accuse me of being selfish.. why take 1000 feet when a nice point of impackt will only take a 100 feet in diameter? i don't know if you were aware of this, but most airplanes have wheels on the bottom of them.. these are made to roll over the ground. sure, most planes do this on nicely paved runways, but there are some pilots who fly into strips that are basically a gravel road etched onto a hillside. and they do it all the time, safely. now your car has probably never seen a dirt road, but mine has. and you know what? it still works. you can get your car through a lot of stuff. cow pastures, shallow creeks, fairly rough mountain roads. it isn't good for it, but it can make it through. we're soft, but go to a third world country in the hills.. for instance some of the central american countries, and observe what they do with their little economy cars. now do the same with an airplane. landing in a field of corn stubble might not be all that good for the landing gear, but it can handle it. now your car won't go through a muddy corn field, niehter will an airplane, but it's usually better than a bunch of trees. but wait, say i'm flying somewhere outside of the midwest, say appalachia. it's all tree covered! well not quite, but marioujana patches are usually much shorter than 1000 feet, and it's no use surviving an off-airport landing just to get shot. well, what's so bad about it being tree covered? let's look at a normal landing at a nice happy runway. you know what the pilot does anywhere from 50 to 500 feet off the ground? he pulls the power to idle. it's like you coming up the street, letting off the gas, and coasting into your driveway. on final, we coast in, happy at our 12:1 ratio. this means we're decending towards the ground at 500 feet per minute, which works out to a vertical speed of 5.6mph. if we're not perfect, we can be a little high, so we come down at something more like 1000 fpm. 5.6mph? try this experiment. take your car out in the yard and drive towards the nearest tree at 5.6 mph (which your speedometer probably won't even register). if you live in the city, head for the nearest telephone pole. but first, say good by to your loved ones, because you will most certaintly die in the spectacular fireball that results, just like it does in an airplane crash.
after you get done inspecting your bumper for damage (you probably didn't even set off the airbags), consider this: we're not fond of hitting the ground at 5 mph. because this means we are on the ground for roughly a third of a second before we're moving upwards at approximately 5.6mph. if you want to visualize this, take a superball and bounce it on the sidewalk. that's what an airplane would do. here's how we fix this. it's called a "flare." we're moving down at 5mph, and forward at 60mph. we level the airplane off, right above the ground, trading our forward speed for vertical. so now our downward is zero, and our forward is gradually bleeding off towards 35 or 40. at this point the airplane gently stops flying, drops lightly to the runway, and coasts to a stop. everybody's happy. now transfer this happy mental image back to appalachia, all covered with trees. plane with stopped engine is gliding ever downward. just above the tree tops, the pilot flares, which stops the descent. in this particular case, he does it ever more agressively as the airspeed slows, bringing the nose higher and higher. but the plane doesn't have enough energy to climb, it just sinks bottom first. done well, and the pilot can probably slow the plane down to below 30 mph. try two experiments. walk over to the bushes around your house, the hedge kind, and hold your hand at a thirty degree angle. now sweep your hand down into the bush like an airplane, notice how the landing is cushioned? now construct a construction: make it thirty feet long, four feet wide, and strap it to the front of your slightly damaged bumper at a thirty degree angle. now cut the large tree down in your front yard, it needs to be a deciduous of some sort, like you'd find in appalachia. cut it so it falls out into the street. now take your car and back it down the street. drive towards the tree. when your car reaches 88 mph, you're going to see some serious... --actually, drive at thirty mph towards the tree, then let off the gas, so you're coasting like the airplane. i ain't going to lie to you, it won't be pretty, but you're not going to die in a firey fireball thing.
at any rate. the world doesn't suddenly end when the engine stops. you ask: what if a wing comes off? close your eyes and imagine yourself on your favorite rollercoaster. and don't look at me wierd when i ask you whether your tires are going to fall off before i ride in your car. plus, you should see some photos of planes that have landed with damage. old wwii photos of planes with large chunks missing, multiple engines dead, that still made it back to the field. photos of small planes that have bumped wings while in the air and still landed safely. you could drive your car over 4x4 only trails for years before it finally quit. airplanes can be the same way. they're built on the idea of simplicity. if it's simple, it won't break as easy, and it works.
let me throw in a thing about helicopters. when their engines quit, they don't drop like a rock to a point of firey impackt. a helicopter flies becuase of the spinning rotors. when the engine quits, the rotors freewheel, and the helicopter starts to drop. as it does, air moves up through the rotors, keeping them spinning (like blowing in the back of a fan spins the blades). since they're spinning, they produce some lift. granted, it's very inefficient, so the helicopter keeps dropping, but the descent is checked a little bit. i don't know any numbers, but i've seen this practiced (it's called autorotation) and i'd guess somewhere in the range of 30mph descent. fast enough to crush anyone's spinal cord on impact. but the last 50' are critical, just like in an airplane. the pilot will trade the potential energy stored in the spinning blades for kinetic energy to slow the descent, leveling it out and landing on the skids with a 5-15mph forward speed. this works well enough that many instructors will have the student take the autorotation all the way to a successful touchdown repetively, without causing undue stress on the humans or the airframe. the whole process happens a lot quicker, but then a helicopter needs less than 100 feet to touchdown in, not 1000'. so it could successfully land in a marijouna field, but if it's a DEA chopper, it's all over but the crime.
speaking of cars being more dangerous than airplanes, i quoted an appropriate quote on may tenth of last year here at the end of the post.
may03, 0130046c2240.2354
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