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| Monga |
 Posted: Mon Oct 26, 2009 5:04 am Post subject: Fear of flying -- questions |
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Forum Freshman
Joined: 26 Oct 2009
Posts: 10
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Hello. I am new here and have lots of questions. Please go easy on me.
I am terrified of flying. Here are a few questions about flying in commercial jet planes. All information appreciated:
1. What keeps the wings on? Are the planes built in such a way that it's impossible for the wings to fall off?
2. I was on a plane recently and there was a definite draft coming from one of the windows. How dangerous was this?
3. What is to stop someone from opening one of the emergency exits during a flight? (They have to be openable due to emergency procedures.)
4. Why does the engine pitch change so often? This always makes me nervous but I'm sure there's a good reason for it.
5. What stops ice forming on the wings and this preventing the flap things from moving safely?
6. In the case of "electrical failure", is there a back-up system? If so, how does it get turned on?
Thanks.
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| Scifor Refugee |
| Posted: Mon Oct 26, 2009 6:41 am Post subject: Re: Fear of flying -- questions |
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Forum Professor
Joined: 02 May 2005
Posts: 1885
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| Monga wrote: |
| 1. What keeps the wings on? Are the planes built in such a way that it's impossible for the wings to fall off? |
I have never heard of a wing falling off a commercial airline. Engines fall off occasionally, but the wing is really part of the body of the plane, so it isn't going anywhere...
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2. I was on a plane recently and there was a definite draft coming from one of the windows. How dangerous was this? |
I believe you that you perceived a draft, but it's verrrrry unlikely that it was actually a breach in the window. The aircraft's sensors would have detected it and the pilot would probably have made an emergency landing.
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3. What is to stop someone from opening one of the emergency exits during a flight? (They have to be openable due to emergency procedures.) |
The doors open in, and the air pressure inside is a LOT higher than the pressure outside. No human would be strong enough to open the door unless the plane was very close to the ground.
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4. Why does the engine pitch change so often? This always makes me nervous but I'm sure there's a good reason for it. |
Probably just the pilot applying more or less power as they climb, descend, turn, etc.
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5. What stops ice forming on the wings and this preventing the flap things from moving safely? |
This page has a nice summary. http://en.wikipedia.org/wiki/Ice_protection_system
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6. In the case of "electrical failure", is there a back-up system? If so, how does it get turned on?
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Each engine on the plane is also an electrical generator, and even one engine is enough to provide power to the whole plane. It also has backup batteries that automatically kick in if the plane's electrical system stops getting power from the engines for some reason. |
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| Monga |
| Posted: Mon Oct 26, 2009 7:11 am Post subject: Re: Fear of flying -- questions |
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Forum Freshman
Joined: 26 Oct 2009
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Thanks, Scifor. This is all very reassuring, apart from a few things:
1. Can the engines really fall off? Not sure if you're joking. Surely there must be some way to guarantee that they stay on? If one did fall off, would the plane be able to fly OK with the remaining engine? Or would the change in weight cause big problems, and/or a crash? Is it true that a plane can glide a long way on no engines at all?
2. There was definitely a draft. I could feel it coming from the edges of the small window next to my seat. I tried the window next to that, and there was no draft there.
One more question: I've read about the possibility of birds being sucked into the engines. How dangerous is this for the plane? Presumably it only affects the plane at take-off/landing, although those are probably the most important moments of the flight. I would have thought it would need a lot of birds to create any problems.
| Scifor Refugee wrote: |
| Monga wrote: |
| 1. What keeps the wings on? Are the planes built in such a way that it's impossible for the wings to fall off? |
I have never heard of a wing falling off a commercial airline. Engines fall off occasionally, but the wing is really part of the body of the plane, so it isn't going anywhere...
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2. I was on a plane recently and there was a definite draft coming from one of the windows. How dangerous was this? |
I believe you that you perceived a draft, but it's verrrrry unlikely that it was actually a breach in the window. The aircraft's sensors would have detected it and the pilot would probably have made an emergency landing.
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3. What is to stop someone from opening one of the emergency exits during a flight? (They have to be openable due to emergency procedures.) |
The doors open in, and the air pressure inside is a LOT higher than the pressure outside. No human would be strong enough to open the door unless the plane was very close to the ground.
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4. Why does the engine pitch change so often? This always makes me nervous but I'm sure there's a good reason for it. |
Probably just the pilot applying more or less power as they climb, descend, turn, etc.
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5. What stops ice forming on the wings and this preventing the flap things from moving safely? |
This page has a nice summary. http://en.wikipedia.org/wiki/Ice_protection_system
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6. In the case of "electrical failure", is there a back-up system? If so, how does it get turned on?
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Each engine on the plane is also an electrical generator, and even one engine is enough to provide power to the whole plane. It also has backup batteries that automatically kick in if the plane's electrical system stops getting power from the engines for some reason. |
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| Scifor Refugee |
| Posted: Mon Oct 26, 2009 8:22 am Post subject: Re: Fear of flying -- questions |
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Forum Professor
Joined: 02 May 2005
Posts: 1885
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| Monga wrote: |
Thanks, Scifor. This is all very reassuring, apart from a few things:
1. Can the engines really fall off? Not sure if you're joking. Surely there must be some way to guarantee that they stay on? If one did fall off, would the plane be able to fly OK with the remaining engine? Or would the change in weight cause big problems, and/or a crash? Is it true that a plane can glide a long way on no engines at all? |
Yes, there have actually been incidents of engines falling off of planes in flight. It's verrry uncommon, but it has happened. But all commercial airlines are legally required to be able to continue to fly in the event of an engine failing (or falling off). The last incident that I know of was in 2007 - everyone was fine, the plane just turned around and landed. http://www.msnbc.msn.com/id/21674981/
And yes, planes can glide a surprisingly long way with no power at all. I believe the glide ratio of a modern 777 is about 1:20, meaning that for every foot of altitude it can glide 20 feet. A typical commercial airline flies at around 5-6 miles altitude, so if all of the engines failed the pilot would have a 100-120 mile radius to find a place to land (and unless you're out in the middle of the ocean, there will almost certainly be somewhere to land within that distance).
That's why engine failures are most dangerous when the plane is just taking off or landing; if the plane is very high when the engines fail, there should be plenty of glide time to find a good place to land. If they fail when the plane is very low, the pilot's options will be much more limited. That's why that plane had to land in the Hudson river a few months ago; the engines failed as the plane was taking just off, so the pilot wasn't high enough to glide back to the airport.
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| One more question: I've read about the possibility of birds being sucked into the engines. How dangerous is this for the plane? Presumably it only affects the plane at take-off/landing, although those are probably the most important moments of the flight. I would have thought it would need a lot of birds to create any problems. |
Yeah, birds are bad news for airplane engines. But if it makes you feel any better, I believe there has only been one incident of deaths from bird strikes on a commercial airline, and it was in the 1960s. After that incident planes were built to better withstand bird strikes, which is probably why there haven't been any fatalities since then. |
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| Monga |
| Posted: Mon Oct 26, 2009 8:32 am Post subject: |
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Forum Freshman
Joined: 26 Oct 2009
Posts: 10
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| Thanks again. I feel much better about it. All the evidence suggests that flying IS extremely safe. For some reason, it just doesn't feel safe. |
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| Ophiolite |
| Posted: Mon Oct 26, 2009 9:32 am Post subject: |
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Time Lord
Joined: 25 Jul 2005
Posts: 6193
Location: Scotland
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This little story may destroy the feeling of wellbeing that scifor refugee has carefully nurtured, but that is not its intent. Rather I just want to point out how even unsafe events in flying are safe enough and can lead to great benefits.
In the 1970s I was routinely crew changing by DC3 charter flight from Singapore to Songklah on the east coast of the Thai peninsula, en route to an oil rig. The DC3, arguably the most succesful aircraft ever built, is a two engined propeller driven beast. These are piston engines - it's not even a turboprop.
Since it was an early morning flight I had gone to sleep. I was woken by my colleague who was quite agitated. The plane was leaping up and down and shaking from side to side. "Look. Look. We're on fire!" I looked out the window and sure enough the port engine was spewing great gouts of flame and smoke, while the wing jerked up and down in a dramatic fashion.
With the confidence and insanity that tend to come with youth I turned to him and said "This is a DC3. They are the safest aircraft on the planet. They are incredibly robust. They can glide for ever if they have to. If the starboard engine catches fire too, then wake me up. Otherwise just relax." I then went back to sleep.
We made an emergency landing at Kuantan - and here's the good bit - we then had to spend three days, all expenses paid in a four star hotel on the beach.
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The Universe is not only weirder than we imagine it is weirder than we can imagine. J.B.S.Haldane. |
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| Monga |
| Posted: Mon Nov 30, 2009 10:14 am Post subject: |
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Forum Freshman
Joined: 26 Oct 2009
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| Nice story, Ophiolite. Thanks. |
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| (In)Sanity |
| Posted: Mon Nov 30, 2009 6:45 pm Post subject: |
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Campus Security
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Location: Phoenix AZ
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Your far more likely to die getting to and from the airport then you are from the plane 
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| Monga |
| Posted: Tue Dec 01, 2009 3:04 am Post subject: |
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Forum Freshman
Joined: 26 Oct 2009
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| (In)Sanity wrote: |
| Your far more likely to die getting to and from the airport then you are from the plane |
Yes, I've heard that several times!
On the one hand, planes do seem incredibly safe. On the other hand, there are situations such as the Air France plane that went missing. If they're so safe, how did this happen?
I read an interesting article that suggested the flight computers could have misinterpreted the data they were collecting, and may have led the pilots to make the wrong decisions. |
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| (In)Sanity |
| Posted: Tue Dec 01, 2009 6:41 am Post subject: |
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Campus Security
Joined: 19 Oct 2004
Posts: 3043
Location: Phoenix AZ
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| Monga wrote: |
| (In)Sanity wrote: |
| Your far more likely to die getting to and from the airport then you are from the plane |
Yes, I've heard that several times!
On the one hand, planes do seem incredibly safe. On the other hand, there are situations such as the Air France plane that went missing. If they're so safe, how did this happen?
I read an interesting article that suggested the flight computers could have misinterpreted the data they were collecting, and may have led the pilots to make the wrong decisions. |
Or maybe they were just bad pilots, or maybe aliens snatched them ,etc. In the end it's all about statistics. Nothing is perfect, so once in a while a plane goes down. Does this mean you shouldn't fly? Of course not. Using that same logic one would also not take a shower, check their mail and especially drive a car. More people die every day from stupid things then do in a year from planes. Stupid things like slipping in the shower or getting hit by a car while checking the mail. We just rarely hear about these incidents as they are so frequent they are just not very news worthy.
In the end you have to risk living in order to live. Be more concerned about your day to day activities then the once in a while plane ride.
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| Solveer |
| Posted: Tue Dec 15, 2009 11:22 am Post subject: |
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I'd like to add some info to this since I have worked on developing aircrafts for several years and have personally been involved in some design, testing and analysis of some of the items you touch.
1. The wings are tested in a static load cell. They test to ultimate strength, something that the aircraft will never experience in real-life. The equivalent load experienced on a passenger would make anyone (maybe not jet fighter pilots for the first few seconds, but everyone else) pass out due to the high G's. The engineering behind this is well established and not the thing I would worry about.
2. The draft you felt came from the pressurization system. There is a constant amount of air pumped into the cabin (about 0.6 pounds of air per person actually) so that people feel comfortable (and can breathe). The aircraft itself is not perfectly sealed (well, but not perfect). So there is always some air leaking through gaps, seals and the places it is meant to go. A small amount of air passes from the overhead distributors through gaps in the interior surfaces and leaves the aircraft in a normal fashion. All part of the design and testing of an aircraft.
3. Doors (as mentioned above) are under a lot of pressure. The normal differential pressure between the inside and outside is in the range of 5-10 pounds-per-square-inch. Assuming the door is 6x4 ft (don't know this number), the resultant force to open would be 17300 pounds (at the 5psi delta-P)... I certainly can't open that. On top of that I believe commercial planes also have a cockpit indicator should someone be stupid enough to try.
4. Engine pitch/frequency is a function of RPMs. The pilot will increase/decrease as needed in order to stay on course/altitude and schedule. The engines often don't run at 100% (in fact, never, they will usually only run in the 70-80% range). There is more power required to climb (as part of the regular flight path and to avoid weather and traffic) so the pilot will increase the thrust when needed and then go to a more energy efficient setting.
5. Ice build up is part of flying (at low altitudes, at high altitudes there is no ice formation because there is no moisture). The wings are required to have de-ice systems (de-ice refers to a system that allows ice to build up and then shed it, whereas anti-ice is for locations where ice may never build up). Engine inlets have anti-ice as well as other structures. The flaps cannot build up ice since they are on the trailing edge of the aerodynamic surfaces (only the forward facing surfaces can build up ice since that is where the droplets hit the surface). All of this is extensively tested in worst-case situations. If something with the icing system fails, its because the Pilots made an error.
6. Power back up is such that each engine alone can supply the power needed. If all engines fail, the battery is required to have at least 30 minutes of back up for all required systems (it might be more for commercial aircraft, don't know).
Bird-strike: this is a (VERY nasty) test that gets performed. A turkey of a given weight gets shot at the engine, windshield and sometimes other critical areas and the damage observed. The engine has to function at a certain percentage of its nominal thrust after a direct strike.
Bottom line (hope this helps a bit): Aircafts are very complex pieces of equipment that are tested and certified to an extreme level of safety (don't expect this from your average car). All critical systems have a backup. If something happens, its because no other aircraft has suffered that before (after ever accident the rules are re-evaluated) or because of pilot error (they are way underpaid in my opinion). |
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| Monga |
| Posted: Mon Jan 25, 2010 2:50 am Post subject: |
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| Cran |
| Posted: Mon Jan 25, 2010 3:03 am Post subject: |
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| (In)Sanity wrote: |
| Your far more likely to die getting to and from the airport then you are from the plane |
"...sometimes I wonder if the airline shuttle bus drivers have been instructed to keep the statistics favourable ..." Micheal Flanders (of Flanders and Swan)
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| Pong |
| Posted: Mon Jan 25, 2010 5:00 am Post subject: |
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Forum Radioactive Isotope
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Monga. I think you'd understand that we humans, being animals, are predisposed to many things including fear. Our bodies charge it up and need to exercise it. Just like we need to sometimes feel calm, sometimes irate, sometimes giddy. So given then that it's in our nature to sometimes feel afraid, and if nothing jumps out at us we must look for it; the question is: what will each of us decide to be afraid of? I think that fearing plane crash is not a bad pick, if you had to pick anything in this world. 
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| k9n |
| Posted: Sun Jul 11, 2010 11:14 pm Post subject: |
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[quote="Solveer"]
3. Doors (as mentioned above) are under a lot of pressure. The normal differential pressure between the inside and outside is in the range of 5-10 pounds-per-square-inch. Assuming the door is 6x4 ft (don't know this number), the resultant force to open would be 17300 pounds (at the 5psi delta-P)... I certainly can't open that. On top of that I believe commercial planes also have a cockpit indicator should someone be stupid enough to try.
[/quote]
However planes have both inward and outward opening doors right? With inward opening doors, the higher pressure inside the craft would make the door impossible for a human to open. But with outward opening doors, the pressure would be enough within the cabin such that a human could actually push the door open at altitude, correct? |
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