Inspired by #1075: Ask an Airline Pilot

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Inspired by #1075: Ask an Airline Pilot

Postby KodiakRS » Tue Jul 03, 2012 4:45 pm UTC

You're in a cigar tube hurtling along several times faster and many thousands of feet higher than evolution could possibly have prepared you to go.

Most people don't realize how spectacular that statement is. You're sitting in a chair flying along at an altitude where an unprotected human would die in seconds, at nearly 700 miles an hour, experiencing something that human beings tried for thousands of years to achieve. Eventually the airplane, an object sometimes as big as an apartment building, is brought back down to earth within a few feet of it's intended target. Now think about this: Every day there are about 30,000 airline flights in the U.S. If we lean towards the conservative side that means there are about 100 million airline flights over the last decade. Of those 100 million flights, four resulted in a fatal crash. Four out of 100 million.

Despite the prevalence of commercial aviation in our daily lives, and it's incredible safety record, very few people actually know what goes on behind that magic door to the cockpit. Other than a quick glance as you get off the plane, and a few sentences from a disembodied voice over the P.A. the cockpit is a total mystery to the traveling public. The funny thing is that I find people are very curious about what airline pilots do, and most of them, even the well educated sciency types (XKCD readers) are usually somewhat misinformed.

So here's your chance to ask a real-life airline pilot about what we actually do up there.



Before we begin I'll answer some of the common ones.

-Yes your cellphone will make the plane explode in a horrible fireball, please turn it off when asked to do so. No airplane mode doesn't count.
-9/11 was not a hoax.
-No, I can't get you free tickets, unless you want to get married.
-I'd give it about a 50/50 chance of a civilian landing an airplane if the pilots died. Assuming you even KNEW the pilots were dead before the airplane ran out of fuel.

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Re: Inspired by #1075: Ask an Airline Pilot

Postby Izawwlgood » Tue Jul 03, 2012 4:51 pm UTC

I saw coming attractions for some new Denzel Washington film wherein he plays a drunken pilot who somehow manages to land a plane after catastrophic engine failure by pulling out of a dive upside down and then rotating it.

Legit?
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Re: Inspired by #1075: Ask an Airline Pilot

Postby gorcee » Tue Jul 03, 2012 5:17 pm UTC

Izawwlgood wrote:I saw coming attractions for some new Denzel Washington film wherein he plays a drunken pilot who somehow manages to land a plane after catastrophic engine failure by pulling out of a dive upside down and then rotating it.

Legit?


Not from a dive from cruising altitude, under those conditions. The trailer shows skin panels ripping off of the aircraft. If that's the case and airspeed is high enough to cause catastrophic aeroservoelastic failure of those components, you're probably not going to manage to bleed off enough speed, inverted, to belly-land the plane.

30,000 feet at, say, 480 knots. Then you dive. And you need to get it to under, say, 180 knots to let the belly of the plane (which is typically designed to absorb the impact of a belly landing at normal landing speeds) take the brunt of the impact. And all of this while your flaps are getting ripped off... not gonna happen. Not out of a dive recovery, at least.

Now, if you had a locked jackscrew on your HT, and you caught it at cruise altitude, and could lower airspeed and achieve an attitude so that the tail was either at near stall, or counter-act the pitch down moment, then maybe.

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Re: Inspired by #1075: Ask an Airline Pilot

Postby Роберт » Tue Jul 03, 2012 5:40 pm UTC

I have a kid's book that says pilots need to know what every button and dial is for in a super-complicated cockpit. How close is this to true?
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Re: Inspired by #1075: Ask an Airline Pilot

Postby pseudoidiot » Tue Jul 03, 2012 5:41 pm UTC

How much is manual and how much is automatic now-a-days? I'm assuming this varies greatly by aircraft.
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Re: Inspired by #1075: Ask an Airline Pilot

Postby gorcee » Tue Jul 03, 2012 5:43 pm UTC

pseudoidiot wrote:How much is manual and how much is automatic now-a-days? I'm assuming this varies greatly by aircraft.


I read this, and for some reason envisioned an airplane with a shifter. *FWOOOSHSHHH* chk *FWOOOOOOOOOSHHHH* chk *FWOOOOOOOOOOOOOOOOOOOSHHHH*

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Re: Inspired by #1075: Ask an Airline Pilot

Postby pseudoidiot » Tue Jul 03, 2012 5:52 pm UTC

Careful, you'll kill the clutch!
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Re: Inspired by #1075: Ask an Airline Pilot

Postby KodiakRS » Tue Jul 03, 2012 10:26 pm UTC

Роберт wrote:I have a kid's book that says pilots need to know what every button and dial is for in a super-complicated cockpit. How close is this to true?


Very. You could point to any button and switch in my current aircrafts cockpit and I would be able to tell you what it does, when you should push it, and any limitations associated with pushing it. It's really not too difficult though. It's sort of like someone with PhotoShop or a CAD program who knows what all the functions of that program are.

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Re: Inspired by #1075: Ask an Airline Pilot

Postby KodiakRS » Tue Jul 03, 2012 10:36 pm UTC

Double post due to posting from cellphone.

pseudoidiot wrote:How much is manual and how much is automatic now-a-days? I'm assuming this varies greatly by aircraft.


It varies greatly, not only by aircraft but by airline and pilot as well. For example, I'm allowed to turn the auto-pilot on at 600' above the ground on take off and as low as 200' on landing. My personal preference is to hand fly until we've reached our final climb speed which happens around 11,000' and disconnect the autopilot as were turning to allign ourselves with the runway.

Other things vary as well. For example almost all airline jets have what's called FADEC (full authoritydigital engine control). Where your thrust lever movements are interpereted by a computer that then decides how to adjust the engine to do what you've requested.

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Re: Inspired by #1075: Ask an Airline Pilot

Postby ShootTheChicken » Tue Jul 03, 2012 11:03 pm UTC

KodiakRS wrote:-Yes your cellphone will make the plane explode in a horrible fireball, please turn it off when asked to do so. No airplane mode doesn't count.


Please elaborate on this. I'd put the odds of at least one person per flight forgetting to turn off their phone at roughly 100%, yet 100% of planes don't crash.
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Re: Inspired by #1075: Ask an Airline Pilot

Postby pseudoidiot » Tue Jul 03, 2012 11:12 pm UTC

I'm fairly certain that statement wasn't serious.

Especially considering the number of times I've left my cellphone or Kindle on during takeoff. Purely by accident of course...
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Re: Inspired by #1075: Ask an Airline Pilot

Postby ShootTheChicken » Tue Jul 03, 2012 11:13 pm UTC

Yeah I half-thought it was a joke, but the rest of the post was relatively not-a-joke, so... just making sure. Although in that case, why do they ask you to turn off your phone?
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Re: Inspired by #1075: Ask an Airline Pilot

Postby KodiakRS » Wed Jul 04, 2012 12:18 am UTC

ShootTheChicken wrote:Yeah I half-thought it was a joke, but the rest of the post was relatively not-a-joke, so... just making sure. Although in that case, why do they ask you to turn off your phone?


It was a joke, apparently a not so good one.

As far as turning off electronic devices. Yes the CAN interfere with the aircraft, in a number of different ways.

The most basic of aircraft navigation equipment, one level more advanced than maps and eyeballs, is the magnetic compass. It simply aligns itself with the earths EM field and the attached card shows you which way you're going. Of course if the EM field is overridden by something, say a plane full of cellphones being used to tweet about how assanine this rule is, it may result in the compass being off by a few degrees. While most airlines now use ring laser gyros to determine heading information, some aircraft still use an EM measuring device called a flux gate compass in conjunction with a gyro to provide heading information. If you're ever at LaGuardia international airport taxiing for takeoff you may notice a yellow sign that says "Caution: large magnetic deviations may exist in this area" or something like that. This is why that warning is there.

Another reason is that the signals being sent TO the aircraft could be messed up by the EM field of a few hundred people playing words with friends as their aircraft comes into land. The system that most aircraft used to navigate in for landing is called a localizer. All over the airport you'll see lines on the ground that look like ladders with uneven rung spacing. These are called ILS critical areas, and when visibility is greatly reduced aircraft aren't allowed to cross them in order to prevent the signal going to aircraft on approach from getting messed up.

The likelihood of either of these two scenarios is VERY slim, it would take a LOT of unshielded electronic devices to cause enough of a problem to be an issue. But the possibility is there.


I highly recommend that people just take a few minutes to look out the window, ponder some worldy matter, or perhaps even start a conversation with the person next to you. They won't bite, probably.

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Re: Inspired by #1075: Ask an Airline Pilot

Postby poxic » Wed Jul 04, 2012 12:39 am UTC

"In the unlikely event of a water landing..."

Most of the water "landings" we hear about were a result of a catastrophe in the air -- fire in the cockpit, gigantic stall without enough time to recover, that sort of thing -- so all the floatation devices in the world weren't much use. In a less shitty situation, where control is still possible, what's the pucker factor on landing on a sufficiently-long strip of water?

I guess I'm sort of asking just how godlike Captain Sully was, aren't I?
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Re: Inspired by #1075: Ask an Airline Pilot

Postby pizzazz » Wed Jul 04, 2012 1:09 am UTC

KodiakRS wrote:
ShootTheChicken wrote:Yeah I half-thought it was a joke, but the rest of the post was relatively not-a-joke, so... just making sure. Although in that case, why do they ask you to turn off your phone?


It was a joke, apparently a not so good one.

As far as turning off electronic devices. Yes the CAN interfere with the aircraft, in a number of different ways.

The most basic of aircraft navigation equipment, one level more advanced than maps and eyeballs, is the magnetic compass. It simply aligns itself with the earths EM field and the attached card shows you which way you're going. Of course if the EM field is overridden by something, say a plane full of cellphones being used to tweet about how assanine this rule is, it may result in the compass being off by a few degrees. While most airlines now use ring laser gyros to determine heading information, some aircraft still use an EM measuring device called a flux gate compass in conjunction with a gyro to provide heading information. If you're ever at LaGuardia international airport taxiing for takeoff you may notice a yellow sign that says "Caution: large magnetic deviations may exist in this area" or something like that. This is why that warning is there.

Another reason is that the signals being sent TO the aircraft could be messed up by the EM field of a few hundred people playing words with friends as their aircraft comes into land. The system that most aircraft used to navigate in for landing is called a localizer. All over the airport you'll see lines on the ground that look like ladders with uneven rung spacing. These are called ILS critical areas, and when visibility is greatly reduced aircraft aren't allowed to cross them in order to prevent the signal going to aircraft on approach from getting messed up.

The likelihood of either of these two scenarios is VERY slim, it would take a LOT of unshielded electronic devices to cause enough of a problem to be an issue. But the possibility is there.



Any idea what the comparative size is between the EM fields of all those cell phones, and the size of the field generated by the aircraft's own electronics? What about any potential fields generated by non electronic devices, like ordinary magnets?

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Re: Inspired by #1075: Ask an Airline Pilot

Postby pyronius » Wed Jul 04, 2012 2:12 am UTC

1: what are the odds of surviving a crash (say for instance if all available engines fail, no airport is within distance, and all other systems still function) and in what portion of the plane are the odds the greatest?

2: why are planes not just controlled with a joystick like in flight simulators? that would be so much simpler.

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Re: Inspired by #1075: Ask an Airline Pilot

Postby KodiakRS » Wed Jul 04, 2012 2:46 am UTC

pyronius wrote:1: what are the odds of surviving a crash (say for instance if all available engines fail, no airport is within distance, and all other systems still function) and in what portion of the plane are the odds the greatest?

2: why are planes not just controlled with a joystick like in flight simulators? that would be so much simpler.


1: Giving odds on survivng a crash like you've described is a very hard thing to do. It is totally dependent on the type of surface on which the pilot chooses to land, and the design of an aircraft. For example a few years ago a BA 777 landed just short of the runway following a dual engine failure. In 1989 a somewhat similar situation happened with a 737 and about a third of the people died. The major X factor in surviving a crash where the impact isn't fatal is fire. Your ability to quickly exit the aircraft is key to survival in the event of a fire. Surviving the impact is more or less dumb luck.

2: A lot of them are. Most fighters and airbus aircraft are controlled with joysticks.

poxic wrote:"In the unlikely event of a water landing..."

Most of the water "landings" we hear about were a result of a catastrophe in the air -- fire in the cockpit, gigantic stall without enough time to recover, that sort of thing -- so all the floatation devices in the world weren't much use. In a less shitty situation, where control is still possible, what's the pucker factor on landing on a sufficiently-long strip of water?

I guess I'm sort of asking just how godlike Captain Sully was, aren't I?


The pucker factor is pretty damn high. Landing an airliner off airport will ALWAYS have a high pucker factor. Aircraft are actually designed to "land" on water and not break apart. Landing on water has one major advantage in that it seriously reduces the risk of a post crash fire. The main problem with landing on water is that your survivability once you get out the plane is pretty dismal unless you can get rescued in a hurry. The part of what sully did that impresses me isn't the landing itself but when he made the choice to land there in the first place. Returning to land at LaGuardia had to be a REALLLLLLY tempting option.

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Re: Inspired by #1075: Ask an Airline Pilot

Postby UniqueScreenname » Wed Jul 04, 2012 3:37 am UTC

What's the difference between turning your phone off and airplane mode? I realize that this may not be a pilot question, but my theory was they always told you to do that so that you would remember to check your phone instead of assuming that you've turned it to airplane mode but actually hadn't.
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Re: Inspired by #1075: Ask an Airline Pilot

Postby KodiakRS » Wed Jul 04, 2012 4:06 am UTC

UniqueScreenname wrote:What's the difference between turning your phone off and airplane mode? I realize that this may not be a pilot question, but my theory was they always told you to do that so that you would remember to check your phone instead of assuming that you've turned it to airplane mode but actually hadn't.


AFAIK Airplane mode disables your phones ability to transmit. This basically makes it like any other electronic device meaning it needs to be off during takeoff and landing, but can be used at other times. Without airplane mode you technically can't use it at all. It's also a good way to save your phones battery life because it keeps it from frantically searching for a signal through the flight which kills your battery.

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Re: Inspired by #1075: Ask an Airline Pilot

Postby ShootTheChicken » Wed Jul 04, 2012 4:09 am UTC

Can commercial airliners dump fuel to prevent fire? I mean this assumes they aren't in a pure panic in the moments before the landing, but are they equipped to do that?
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Re: Inspired by #1075: Ask an Airline Pilot

Postby darknut » Wed Jul 04, 2012 5:40 am UTC

ShootTheChicken wrote:Can commercial airliners dump fuel to prevent fire? I mean this assumes they aren't in a pure panic in the moments before the landing, but are they equipped to do that?


they dont dump fuel in order to extinguish fires, in case of fires there are fire bottles (just another name for fire extinguisher) for each engine, upon activation they spray directly into the selected engine(s), there are also shut off valves between the engines and fuel tanks (multiple valves i believe)

as for fuel dumping, the main reason that exists is to reduce weight for landing in an emergancy,
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Re: Inspired by #1075: Ask an Airline Pilot

Postby Adacore » Wed Jul 04, 2012 6:07 am UTC

I thought I read somewhere that most commercial airliners had no capability to dump fuel. Wikipedia seems to corroborate this - it was a feature of early aircraft in the 1950s and 1960s, but hasn't been installed on most twin-engine planes built since then. Aircraft with more engines may or may not have it.

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Re: Inspired by #1075: Ask an Airline Pilot

Postby darknut » Wed Jul 04, 2012 6:50 am UTC

i dont know a lot about which ones do and dont have the ability, the rules are that if the aircrafts take off wieght is higher than its landing wieght it must have the ability to jettison fuel (normally it would burn off the wieght in flight, but in emergancy it may have to dump)this is as much as i now to be true, its a law
in my previous post i was trying to find a referance to an actual law but gave up

im almost positive there are new aircraft still in the heigher takeofff weight than landing weight category, and i am positive they didnt stop in the 60s
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Re: Inspired by #1075: Ask an Airline Pilot

Postby eSOANEM » Wed Jul 04, 2012 10:39 am UTC

KodiakRS wrote:The most basic of aircraft navigation equipment, one level more advanced than maps and eyeballs, is the magnetic compass. It simply aligns itself with the earths EM field and the attached card shows you which way you're going. Of course if the EM field is overridden by something, say a plane full of cellphones being used to tweet about how assanine this rule is, it may result in the compass being off by a few degrees.


Bollocks.

That may be what you were taught, but it is not the case.

I sail, and have been on a yacht with at least three phones (and a similar number of iPods lying around the boat) on with data connections, data being pushed and pulled through them and, even with one in my pocket as I stand at the wheel, less than a foot from the compass, it is not causing any deviation. Given that signal strength goes with an inverse square law, if a single phone less than a foot from a cheap compass on a training yacht doesn't mess it up, even a very large number of phones in the cabin of a plane won't mess up the plane's compass.

Besides, the far bigger source of deviation would be the plane itself. Large lumps of metal tend to mess with compasses moreso than phones. Now I suspect (very strongly) that the compasses on planes have all been swung to compensate for it however, swinging a ship (or, in this case, a plane) is an imprecise art and the amount of deviation will depend on the position of the landing gear and the contents and arrangement on the cargo in the hold so any errors (which must necessarily exist) in the compensation for magnetic deviation from solid metal are going to swamp any additional deviation due to phones.

KodiakRS wrote:Another reason is that the signals being sent TO the aircraft could be messed up by the EM field of a few hundred people playing words with friends as their aircraft comes into land. The system that most aircraft used to navigate in for landing is called a localizer. All over the airport you'll see lines on the ground that look like ladders with uneven rung spacing. These are called ILS critical areas, and when visibility is greatly reduced aircraft aren't allowed to cross them in order to prevent the signal going to aircraft on approach from getting messed up.


Consumer devices are not allowed to broadcast on ATC or navigation frequencies and devices are tested for compliance with this. Because of this, unless aircraft have really shitty radios, phones/iPads/iPods/PSPs etc. will not interfere with them. The reason planes aren't meant to fly over the ILS critical areas is because the plane, being a large lump of metal, will absorb most EM radiation sent through it including a good chunk of any radio signal. This has nothing to do with any currents in the plane and everything to do with it being a big lump of metal.

darknut wrote:i dont know a lot about which ones do and dont have the ability, the rules are that if the aircrafts take off wieght is higher than its landing wieght it must have the ability to jettison fuel (normally it would burn off the wieght in flight, but in emergancy it may have to dump)this is as much as i now to be true, its a law
in my previous post i was trying to find a referance to an actual law but gave up

im almost positive there are new aircraft still in the heigher takeofff weight than landing weight category, and i am positive they didnt stop in the 60s


Wikipedia corroborates this. The first pic on the fuel dumping page is of an A340-600 which, according to the page for the A340 first flew in 2001.
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Re: Inspired by #1075: Ask an Airline Pilot

Postby KodiakRS » Wed Jul 04, 2012 8:03 pm UTC

eSOANEM wrote:
Bollocks.

That may be what you were taught, but it is not the case.

I sail, and have been on a yacht with at least three phones (and a similar number of iPods lying around the boat) on with data connections, data being pushed and pulled through them and, even with one in my pocket as I stand at the wheel, less than a foot from the compass, it is not causing any deviation. Given that signal strength goes with an inverse square law, if a single phone less than a foot from a cheap compass on a training yacht doesn't mess it up, even a very large number of phones in the cabin of a plane won't mess up the plane's compass.

Besides, the far bigger source of deviation would be the plane itself. Large lumps of metal tend to mess with compasses moreso than phones. Now I suspect (very strongly) that the compasses on planes have all been swung to compensate for it however, swinging a ship (or, in this case, a plane) is an imprecise art and the amount of deviation will depend on the position of the landing gear and the contents and arrangement on the cargo in the hold so any errors (which must necessarily exist) in the compensation for magnetic deviation from solid metal are going to swamp any additional deviation due to phones.


Aircraft mag heading indicators are indeed checked for deviation. There's a card near them that lists the condition they were tested in (usually just radios on, whatever that means) and the amount of deviation for various headings. I know cellphones CAN screw with the compass because I do it intentionally sometimes. It's not uncommon for a compass to become slightly sticky and rather turn the entire airplane to get it to change I just place my cellphone next to it and it provides enough magnetic force to break it free and get it swinging again. I also use to to place my cellphone on the glare shield next to the compass just enough to get it to swing about 15 degrees to see if my students would check it back when I was a flight instructor. The odds of a cellphone in the cabin affecting it are VERY rare but they are there.

eSOANEM wrote:
KodiakRS wrote:Another reason is that the signals being sent TO the aircraft could be messed up by the EM field of a few hundred people playing words with friends as their aircraft comes into land. The system that most aircraft used to navigate in for landing is called a localizer. All over the airport you'll see lines on the ground that look like ladders with uneven rung spacing. These are called ILS critical areas, and when visibility is greatly reduced aircraft aren't allowed to cross them in order to prevent the signal going to aircraft on approach from getting messed up.


Consumer devices are not allowed to broadcast on ATC or navigation frequencies and devices are tested for compliance with this. Because of this, unless aircraft have really shitty radios, phones/iPads/iPods/PSPs etc. will not interfere with them. The reason planes aren't meant to fly over the ILS critical areas is because the plane, being a large lump of metal, will absorb most EM radiation sent through it including a good chunk of any radio signal. This has nothing to do with any currents in the plane and everything to do with it being a big lump of metal.


ILS signals are historically twitchy. There have been cases of ILS signals being distorted by everything from a microwave right under the approach path, to trees. Yes trees.* It's plausible that some sort of electronic device near the antenna could distort the signal just enough to cause a problem. Not likely, but plausible.

eSOANEM wrote:
darknut wrote:i dont know a lot about which ones do and dont have the ability, the rules are that if the aircrafts take off wieght is higher than its landing wieght it must have the ability to jettison fuel (normally it would burn off the wieght in flight, but in emergancy it may have to dump)this is as much as i now to be true, its a law
in my previous post i was trying to find a referance to an actual law but gave up

im almost positive there are new aircraft still in the heigher takeofff weight than landing weight category, and i am positive they didnt stop in the 60s


Wikipedia corroborates this. The first pic on the fuel dumping page is of an A340-600 which, according to the page for the A340 first flew in 2001.


Yes airplanes still come with fuel dump mechanisms, and yes they're mostly used to shed excess weight in the form of fuel in order to make landing weight. Generally speaking, the longer the range of the aircraft the more likely it is to have a fuel dump mechanism. If an a340 takes off from Paris headed for L.A. it's going to have a LOT of fuel onboard. On takeoff it can weigh over #800,000. However, it's maximum landing weight is about #570,000. So if it takes off and has some sort of failure that would require it to return to Paris it needs the ability to dump a few hundred thousand pounds of fuel. Burning that off with just the engines could take a very long time.



*The localizer at DTW for 27L was named I-EPA in honor of the EPA who held up it's installation for months because a few trees would have to be chopped down to ensure a clean signal.

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Re: Inspired by #1075: Ask an Airline Pilot

Postby eSOANEM » Wed Jul 04, 2012 8:58 pm UTC

KodiakRS wrote:ILS signals are historically twitchy. There have been cases of ILS signals being distorted by everything from a microwave right under the approach path, to trees. Yes trees.* It's plausible that some sort of electronic device near the antenna could distort the signal just enough to cause a problem. Not likely, but plausible.


A microwave of course using a magnetron, the frequency of the emissions of which are easily varied by changing the load. Seeing as a magnetron is an electrical device, such a malfunction could occur easily and could cause it to transmit on a frequency which could interfere with navigation. Seeing as a phone's aerial is controlled digitally, a malfunction to change the frequency of transmission would be incredibly unlikely (as well as make the phone useless).

Trees I'm surprised at, but I am certain that has more to do with trees being big objects than anything else. Big objects mess with radio, it's why the radio in your car gets crackly when you drive under a bridge, that doesn't say anything about phones. If anything, it says that the problem lies in the ILS.
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dhokarena56
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Re: Inspired by #1075: Ask an Airline Pilot

Postby dhokarena56 » Wed Jul 04, 2012 9:34 pm UTC

Why on earth don't planes come with parachutes? It seems to me that of all the devices you could use to save lives in event of an accident, parachutes would be a good choice.
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Re: Inspired by #1075: Ask an Airline Pilot

Postby KodiakRS » Wed Jul 04, 2012 10:45 pm UTC

dhokarena56 wrote:Why on earth don't planes come with parachutes? It seems to me that of all the devices you could use to save lives in event of an accident, parachutes would be a good choice.


They do. There's a company called Cirrus that makes a popular line of single engine piston powered aircraft. One of their main selling points is that they all come with a chute.

On bigger airplanes it's a little bit more tricky. First off you have the sheer weight issue to deal with. The parachute on the cirrus aircraft is pretty darn big to begin with, and that's for an aircraft that weighs about #3,000 max. The airbus a380 has a max takeoff weight just over a million pounds so you can imagine how big that chute would half to be. Then there's the speed issue. The terminal velocity of a human being is in the 120MPH range depending on posture/size/air density. 120MPH is dangerously slow for a large jet. In fact, the crash of Cologon 3407 happened because the airplane dropped below it's 130kts (150mph) stall speed. Imagine the force placed upon a parachute if it was opened up attached to a million lbs of metal going 200+ MPH? You could stagger the opening somehow with multiple chutes of increasing size but now your adding even more complexity to an already overly complex system.

Then consider that you have to be in the right attitude to have a successful opening. If you're in a large bank, or inverted, the chute will just make the problem worse.

By the way, you will occasionally see airplanes equipped with small spin recover chutes. These are simply designed to allow the aircraft to get out of an unrecoverable spin and either continue flying or eject from the aircraft.

Successful spin chute usage: http://www.youtube.com/watch?v=kqXuZhcpt10

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Re: Inspired by #1075: Ask an Airline Pilot

Postby Steax » Thu Jul 05, 2012 12:50 am UTC

I'm pretty sure the cell phone ban thing is less about if it's ever happened, and more about playing it safe. It's not like you'll get reception up there anyway.

If Airplane Mode doesn't work, then we're about to see a lot of falling planes...
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Re: Inspired by #1075: Ask an Airline Pilot

Postby Adacore » Thu Jul 05, 2012 12:58 am UTC

Steax wrote:I'm pretty sure the cell phone ban thing is less about if it's ever happened, and more about playing it safe. It's not like you'll get reception up there anyway.

Actually, I think you do get reception, at least to some extent. I've read a few places, mostly in reports about hijacked planes, that the passengers were able to use their cellphones while in flight. The wikipedia article on the United 93 hijacking lists numerous people on the plane who had telephone conversations with family/friends/911 operators, for example.

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Re: Inspired by #1075: Ask an Airline Pilot

Postby Steax » Thu Jul 05, 2012 1:04 am UTC

I recall those being mostly from the onboard phones and because the plane wasn't at cruising altitude yet.
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Re: Inspired by #1075: Ask an Airline Pilot

Postby Adacore » Thu Jul 05, 2012 1:37 am UTC

You're right in that they were mostly from onboard phones, I hadn't thought of that, which was silly. There were two calls from cellphones, apparently, though. The article states that the plane was on autopilot at an altitude of 40,700 feet, but it's unclear if it descended by the time the cellphone calls were made.

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Re: Inspired by #1075: Ask an Airline Pilot

Postby PhoenixEnigma » Thu Jul 05, 2012 4:05 am UTC

Steax wrote:I'm pretty sure the cell phone ban thing is less about if it's ever happened, and more about playing it safe. It's not like you'll get reception up there anyway.

If Airplane Mode doesn't work, then we're about to see a lot of falling planes...

The bolded is they key point. The primary reason cell phones are banned on planes is for the sake of the mobile network, and in fact it's the FCC that has banned it in the US (though the FAA discourages it, it's not technically banned by them and they have left final authority on the matter with the airlines). Being above the towers throws all sorts of assumptions of mobile network design out the window (for one, that the cellular devices are mostly in a flat plane), and combined with the high speeds, it can cause some pretty funky (and bad) things to happen on the network side. Some mobile standards also flat out won't work above certain speeds, though I can't recall exactly which standards or speeds - for some reason I recall vanilla GSM having feasibly-reachable limits, but I could be wrong.

If cell phones actually made planes fall from the sky, we'd see a lot of falling planes. There are a few airlines in the Middle East and Europe that allow cellular devices to be used on planes - but they install picocells to provide coverage and backhaul the calls with more traditional air-ground methods.

If you're seeing a cell phone deflect a compass, that's almost certainly just plain magnetism at work. Cell phones contain magnets - often reasonably strong, if small ones - in their speakers, and they also potentially exist in cell phone cases (Blackberry ones in particular). Luckily, magnetism falls off even faster than EM (inverse cube, not inverse square of distance), so it's not really an issue unless you are putting the phone right beside the thing.

ETA: An actual question (partly inspired by the biting comment): When there's an emergency in the air of some kind, who decides how that's going to be handled? What kind of criteria go into "we can finish this flight" as opposed to "we need to be on the ground 5 minutes ago"?
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Re: Inspired by #1075: Ask an Airline Pilot

Postby Izawwlgood » Thu Jul 05, 2012 4:09 am UTC

Truthfully, I thought banning phones was in the case of emergency, to prevent people from fiddling with things. Just like why putting your tray in the upright position isn't because the thing will kill you, but because if there's a crash and people need to get off the plane ASAP, you don't want people texting or whatnot.
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Re: Inspired by #1075: Ask an Airline Pilot

Postby KodiakRS » Thu Jul 05, 2012 7:34 am UTC

Remember that joke in the OP about Cellphones causing the airplane to magically explode? This is why it was there...

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Re: Inspired by #1075: Ask an Airline Pilot

Postby Steax » Thu Jul 05, 2012 7:45 am UTC

I do find the cell phone thing to be oddly strange, though, because a great deal of people who know about planes are waaaay over in the "they're actually fine" or "holy shit turn that off or we're gonna die" camp. It's an interesting thing to talk about.

Question: I sometimes feel a bit uncomfortable when I see things like floppy inner-plane-walls, or whatever they're called. What's actually between the cabin and the open air? what's between that inner wall and the outer skin?
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Re: Inspired by #1075: Ask an Airline Pilot

Postby wam » Thu Jul 05, 2012 9:14 am UTC

Being in the aviation industry (on the modification and maintanence side) this is an interesting thread as I don't speak to pilots nearly enough!

Steax wrote:I do find the cell phone thing to be oddly strange, though, because a great deal of people who know about planes are waaaay over in the "they're actually fine" or "holy shit turn that off or we're gonna die" camp. It's an interesting thing to talk about.


Also when you install new electronic components in the cockpit you have to do electronic emissions tests, to check that everything works.

Steax wrote:Question: I sometimes feel a bit uncomfortable when I see things like floppy inner-plane-walls, or whatever they're called.


Depends on exact vertical location but the main ones are called sidewall panels.

Steax wrote:What's actually between the cabin and the open air? what's between that inner wall and the outer skin?


Insulation and wires mainly.

http://www.airliners.net/photo/Air-Fran ... fb5b6783db

I have much better photos but can't really post them.

PS sorry for the quote sniping
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Re: Inspired by #1075: Ask an Airline Pilot

Postby Steax » Thu Jul 05, 2012 11:13 am UTC

So basically a floppy wall thing isn't any harm, right? There was a moment in my childhood when planes got scarier as I realized that, yes, there are only a few inches between me and the sky.

Also, on the accident avoidance side: are there any signs that passengers should be aware of that might indicate that something's wrong? I often hear different whistles or hums on planes, but I expect that to be because of differences of seating, weather and plane models. Still, it's nice to know if there are clear indicators that passengers should report about.
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Re: Inspired by #1075: Ask an Airline Pilot

Postby wam » Thu Jul 05, 2012 11:42 am UTC

Yeah floppy walls are probaly due to wear on the bindings, but no they are not structural.

To be fair there shouldn't be anything that the passengers notice that the maintence guys haven't seen. Or that isn't reported by sensors.

Interesting fact (don't read if your a nervous flyer)

Spoiler:
If you look on aircraft (not sure how universal this is though) and you can see little bits of blue tape, thats where they are marking cracks/defects that need to be watched through maintanence. As theres a maximum crack size they are allowed.
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Re: Inspired by #1075: Ask an Airline Pilot

Postby dubsola » Thu Jul 05, 2012 12:23 pm UTC

On the inside or the outside?


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