Topic: Why do airplanes fly

[Dionysus]

ikr

You're so immature, panda.

[D'oh!]

DO NOT SMOKE ON A PLANE, especially mine.  I will make sure you get a $10,000 fine and or prison time, it is not worth the risk you're causing.

I wish you were my pilot a few years ago.  The guy next to me returned from the bathroom just reeking of cigarette smoke.  The stewardess soon confronted him about it, but basically just gave him a stern yet subdued warning.  I guess there was too much paperwork involved to consider making a big deal out of it.

[benschwab]

If my coffee won't spill, why don't they do this every time I fly commercially (once a month)? I would pay more money.

I speculate that you are unusual.

[Hanes]

If my coffee won't spill, why don't they do this every time I fly commercially (once a month)? I would pay more money.

I speculate that you are unusual.

"We only have one open seat, and it's on a flight that has scheduled barrel rolls.  Is that all right?"

[Galactus]

   Thanks for the answer Belgarath. The plane flip to put out a fire wasn't on a documentary or anything
like that, it was in an episode of Human Target.

[Belgarath]

   Thanks for the answer Belgarath. The plane flip to put out a fire wasn't on a documentary or anything
like that, it was in an episode of Human Target.

Ahh.  Now that makes sense.  TV writers tend to take a LOT of liberty in airplane facts. 

[Shibboleth]

I used a 747 to defeat two MIG's in head to head combat over NAM. I didn't have any missiles so I just trapped them in my jet wash and hit them with my landing gear.

[khendar]

Hey Belgarath whilst you're here busting airplane myths:

Can a 747 do a loop ?

When smoking on planes was legal the air inside had to be refreshed more often, which resulted in better air quality than we have now that they've banned it.

Smoking also allowed the engineers to locate microscopic flaws in the skin of the plane. The smoke would be sucked out of the holes and leave tarry trails.

[Belgarath]

Hey Belgarath whilst you're here busting airplane myths:

Can a 747 do a loop ?

When smoking on planes was legal the air inside had to be refreshed more often, which resulted in better air quality than we have now that they've banned it.

Smoking also allowed the engineers to locate microscopic flaws in the skin of the plane. The smoke would be sucked out of the holes and leave tarry trails.

A 747 could do a loop, but I don't know if the airplane could take the g-loading coming out of the loop.  It wouldn't be a nice pretty circle either, it'd be very lopsided.  Any airplane can do a loop if you start the maneuver with enough energy (think speed).  The thing which would cause the problem would be pulling out of the dive before you hit the ground and before you overspeed the aircraft and start losing bits.

Airplanes use compressed air which is bled off the engine.  This air is cooled and then passed into the cabin.  Now, if you were to just keep blowing the air in, you'd cause the plane to explode, so the way that the pressure is controlled is with an outflow valve.  If you close the outflow valve more, you increase cabin pressure.  Opening the valve decreases cabin pressure.

So knowing that, you can ask the question.  If that air isn't replaced, and considering that there aren't a bunch of plants breathing carbon dioxide on the plane, doesn't it make sense that you need to replace the air fairly regularly?  And that's exactly what happens.  Now different individual aircraft types will filter air to different degrees.  Smoke would gum up all of these air systems to a considerable degree.

Smoke COULD find holes, but that's not how they did it.  Heck, this accident happened before smoking was banned:

http://en.wikipedia.org/wiki/Aloha_Airlines_Flight_243

(Well, I think it happened right about the same time as smoking was banned.  Within a month)

I can remember being on airplanes back then.  They were AWFUL because smoke permeated the cabin.  Airlines made smokers sit in the back of the plane (generally because the outflow valve is located aft and thus the air typically moves from the front to the back)

If there was a change in the way air was recirculated, it would be driven by fuel savings, not less smoking.

[Shibboleth]

When an pilot comes on the radio and says something like, "We are going to move to a higher altitude to avoid some turbulence." I always wonder.... can you see turbulence on a radar or are other planes talking to each other and giving advice? Do pilots from different planes chatter with each other when they are in the air?

[Belgarath]

When an pilot comes on the radio and says something like, "We are going to move to a higher altitude to avoid some turbulence." I always wonder.... can you see turbulence on a radar or are other planes talking to each other and giving advice? Do pilots from different planes chatter with each other when they are in the air?

No, you can't see turbulence.  You move because either:

1) Someone in front of you reported it to ATC
2) You can see thunderstorms (which mean turbulence)
3) Your dispatcher who is monitoring the weather along your route sends you a message saying forecasts indicate it and you might want to move to a different altitude.

Pilots don't chat with each other while flying, you could but you don't.

[quokka]

Pilots don't chat with each other while flying, you could but you don't.

I wish they would extend this to truckies. You need to keep the truck channel open in case something important is said over the radio, but 99% of the time it's this witty banter;

"Hey Pete, that you"?
"Yeah mate, who's this"?
"Barry mate; how's trucking treating you"
"Yeaaaaah, not bad mate, how's it treating you"
"Alriiight mate, can't complain".

It doesn't stop, which means listening to podcasts or audio books is pretty much impossible.

[David "Stubb" Oswald]

Pilots don't chat with each other while flying, you could but you don't.

So after Christmas this year I was flying from Paris to Charlotte and we hit some turbulence over the Atlantic Ocean. I remember watching the little screen that shows where we were, altitude, and speed; and we were right over the middle of the ocean at the time. The captain (or one of the pilots) came on the intercom and said he was talking with a pilot on a plane flying the same path about thirty minutes ahead of us and that pilot said the turbulence had ended, so we would be coming out of it soon.  So was he actually talking to some ATC (I would imagine we were to far from land to still communicate)?

[Belgarath]

Pilots don't chat with each other while flying, you could but you don't.

So after Christmas this year I was flying from Paris to Charlotte and we hit some turbulence over the Atlantic Ocean. I remember watching the little screen that shows where we were, altitude, and speed; and we were right over the middle of the ocean at the time. The captain (or one of the pilots) came on the intercom and said he was talking with a pilot on a plane flying the same path about thirty minutes ahead of us and that pilot said the turbulence had ended, so we would be coming out of it soon.  So was he actually talking to some ATC (I would imagine we were to far from land to still communicate)?

That's sort of a special case.  When you're flying over open water, you do have a frequency reserved for direct pilot to pilot communications, simply because that is how you find out about things like weather.  Apologies, I was directing my comments to over land communications.

Over the middle of the ocean you have two forms of communication with ATC.  First is the HF radio which is basically AM radio.  It has a very long range, but is really poor quality.  The other option is direct satellite communication, which is as clear as talking on the telephone.  In either case, when you're out over the ocean you don't get radar control.  You are controlled by timing and altitude.  You report over certain waypoints with certain information (the acronym is I-PTA-TEN).

Oh, I know you're going to ask:  What the heck is I-PTA-TEN???

I-dentification
P-osition
T-ype (IFR/VFR)
A-ltitude
T-ime (over the P above)
E-TA to the next reporting point (including the name)
N-ext fix after that.

So you would say something like:

'Jetblue 123 over HOGGS, IFR, FL350 at 1500 zulu, 50 minutes to DULEE, FATHR next'

Which tells the ATC folks where you are, where you're going and where you're going next.  They then take all of this and plot it out and if two planes are projected to be at the same altitude and within 20 miles of each other, they'll give someone a course change or an altitude change.

[av8rmike]

I was chatting to someone and the subject of what makes airplanes fly came up.  I'm sure I can remember an SGU episode where someone said that the actual mechanism was widely misunderstood or unknown, but I can't for the life of remember the details.

At school we were told it had something to do with a lower air pressure over the top of the wing, but I've got a feeling that might not be completely correct.

Maybe I'm just missremembering, but would someone be able so shine a light on this form me?

The mechanism is perfectly well understood: Money.