# What is happening when the airplane lands? **URL:** \ **Category:** Factual Questions\ **Created:** [October 12, 2010, 7:44pm UTC](https://boards.straightdope.com/t/what-is-happening-when-the-airplane-lands/556909 "2010-10-12T19:44:58Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [October 12, 2010, 9:18pm UTC](https://boards.straightdope.com/t/what-is-happening-when-the-airplane-lands/556909/21 "2010-10-12T21:18:03Z")
> [@Chessic\_Sense](#): > > I can tell you from experience that the brakes on a plane are nowhere near as effective as aerodynamic brakes. I can stop my Cessna in two ways- stepping on the brakes or pulling up the elevator. The former stops you eventually. The latter stops you right away. I’m guessing if you graphed the stopping power of wheel brakes versus aerodynamic brakes you’d see a crossing point where above a certain speed the air brakes are better and below which the wheel brakes are better. At least my gut tells me when taxiing your air foils aren’t going to do jack to stop you and it is all the wheel brakes doing the work. Where this crossover point is I have no idea (and doubtless is different for different planes). ---
**Author:** ![EmAnJ](https://avatars.discourse-cdn.com/v4/letter/e/d2c977/32.png) [@EmAnJ](https://boards.straightdope.com/u/EmAnJ)\ **Post date:** [October 12, 2010, 9:20pm UTC](https://boards.straightdope.com/t/what-is-happening-when-the-airplane-lands/556909/22 "2010-10-12T21:20:51Z")
> [@Chessic\_Sense](#): > > If you want to overcome your fear of flying, just consider what happens when an engine quits. The plane doesn’t become a rock. It becomes a glider. At 4,000 feet, a Boeing 747 can glide 11.6 miles. That’s a lot of space for such a low altitude. If the landing gear doesn’t open, you can still land perfectly safely on the belly of the aircraft. Sure, the plane is ruined, but you’re still alive. > > So the only way you’re really in trouble is if the wing falls off or someone shoots you down. What are you so worried about? All of my fear is irrational, and based on my lack of knowledge about the physics of flying. Mostly, I was/am nervous with turbulence, but last week, someone on SDMB linked to an article called ‘Ask the Pilot’, and in it, he said something about how turbulence is more a matter of passenger comfort for the pilot, not anything to worry about. For some reason, that helped. I guess my fear is a combination of things. As we’re taking off, I think ‘How come it’s taking so long to get up? We’re going to hit the end of the runway!’ and then as we lift, the groan of the plane is unnerving. If the engine whines (like it did on my am flight to LV), it freaks me out, like there may be something wrong with the engine. I was able to rationalize that it’s probably the first flight for that aircraft that day, so the engine was just cold. Sure enough, the sound went away after a while. Bumps that I can hear and feel below my feet while we’re in the air also make me nervous. Not sure why, and I usually tell myself it’s luggage falling in the compartment below. Moderate turbulence isn’t fun for me, though I’ve found that larger aircraft seem to experience less then the smaller, rural aircraft (which I fly on often). I enjoy the landing, though I’ve found that there seems to be a lot of turbulence when coming in for a landing, especially coming in the Calgary (home). I’ve had a couple of bad landings here, but luckily, the fact that I ‘survived’ it seems to help reduce my fear. I think another major reason for this fear is lack of control (a theme that seems to run my life - eating disorders, anxiety, etc., all seems to point back to this ‘lack of control’ issue). If I am in a corporate jet or Cessna (have been on a few occasions), where I can see the pilots and the instruments, I have less anxiety, even thought the flight may be more rough. I also have this issue when driving - I can’t sleep or take my eyes off the road if I am a passenger, most of the time. ---
**Author:** ![EmAnJ](https://avatars.discourse-cdn.com/v4/letter/e/d2c977/32.png) [@EmAnJ](https://boards.straightdope.com/u/EmAnJ)\ **Post date:** [October 12, 2010, 9:25pm UTC](https://boards.straightdope.com/t/what-is-happening-when-the-airplane-lands/556909/23 "2010-10-12T21:25:31Z")
> [@Whack-a-Mole](#): > > > [@EmAnJ](#): > > > > Go ahead and post links to the hairy landing due to wind shear - I am interested in watching stuff like that and it seems to have no real effect on my fear of flying. > > [Here ya go](http://www.youtube.com/watch?v=5X_7Xt2ga-s) (the last one the plane looks to come inches away from a crash). Ho-ly crap! Why would a pilot attempt to land crosswind? Don’t airports have runways that run in different directions, so the pilot can land without having to attempt a landing in a crosswind? Are these crosswind landings happening at airports with only one runway? Would a commercial aircraft attempt a landing in those conditions? ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [October 12, 2010, 9:28pm UTC](https://boards.straightdope.com/t/what-is-happening-when-the-airplane-lands/556909/24 "2010-10-12T21:28:49Z")
> [@Machine\_Elf](#): > > re: anxiety due to turbulence and hard landings, it may be helpful to realize that these planes are built tough. _Really_ tough. For reference, a Chevy Corvette will give you something close to 1 g of acceleration when you stomp on the gas in first gear; if you’ve ever felt anything like that, it’s pretty dramatic. Commercial aircraft will tolerate _several_ g’s in any direction before suffering permanent damage. People who weren’t wearing their seatbelts have occasionally been severely injured and even killed (head injuries) by severe in-flight turbulence, but the plane itself was unharmed. It will take a lot of abuse before the pilot starts to worry; just keep your seatbelt fastened while flying, and know that the plane will tolerate far more punishment than you think. I forget where I saw it but it was a wing loading test for some commercial jet. The whole thing happens on the ground and they put big hydraulic jacks on the wing and bend it upward. It is shocking how far it got before it failed (much further than would ever realistically occur in flight). I recall seeing the 787 on its maiden flight and being surprised at how much its wings flexed upward. It is a new design for a wing (carbon fiber) and I understand this flexing is absolutely normal and not an issue with that plane whatsoever. Heck…the wings are probably even stronger than most other commercial jets. Still…heckuva thing to see. ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [October 12, 2010, 9:29pm UTC](https://boards.straightdope.com/t/what-is-happening-when-the-airplane-lands/556909/25 "2010-10-12T21:29:50Z")
> [@EmAnJ](#): > > All of my fear is irrational, and based on my lack of knowledge about the physics of flying. There’s a way of overcoming that. 😉 Seriously, you can take a few lessons at your local municipal airport. You may be frightened, but remember that airplanes hardly ever crash. By taking lessons – and taking control – you will learn what’s going on and it will reduce your fear. Just don’t ‘lock up’. When the instructor lets you handle the controls, don’t get frightened and hold them in a death grip. When he says, ‘I have the airplane,’ or ‘Let go!’, let go. ---
**Author:** ![EmAnJ](https://avatars.discourse-cdn.com/v4/letter/e/d2c977/32.png) [@EmAnJ](https://boards.straightdope.com/u/EmAnJ)\ **Post date:** [October 12, 2010, 9:33pm UTC](https://boards.straightdope.com/t/what-is-happening-when-the-airplane-lands/556909/26 "2010-10-12T21:33:53Z")
> [@Johnny\_L.A](#): > > > [@EmAnJ](#): > > > > All of my fear is irrational, and based on my lack of knowledge about the physics of flying. > > There’s a way of overcoming that. 😉 > > Seriously, you can take a few lessons at your local municipal airport. You may be frightened, but remember that airplanes hardly ever crash. By taking lessons – and taking control – you will learn what’s going on and it will reduce your fear. > > Just don’t ‘lock up’. When the instructor lets you handle the controls, don’t get frightened and hold them in a death grip. When he says, ‘I have the airplane,’ or ‘Let go!’, let go. I’ve actually been considering that for years but I think the cost is pretty high to do something like that. Maybe I’ll look in to it some more. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [October 12, 2010, 9:40pm UTC](https://boards.straightdope.com/t/what-is-happening-when-the-airplane-lands/556909/27 "2010-10-12T21:40:16Z")
> [@EmAnJ](#): > > > [@Whack-a-Mole](#): > > > > [Here ya go](http://www.youtube.com/watch?v=5X_7Xt2ga-s) (the last one the plane looks to come inches away from a crash). > > Ho-ly crap! > > Why would a pilot attempt to land crosswind? Don’t airports have runways that run in different directions, so the pilot can land without having to attempt a landing in a crosswind? Are these crosswind landings happening at airports with only one runway? Would a commercial aircraft attempt a landing in those conditions? Depends on many things. Some airports have alternate runways. Many others don’t. Landing in crosswind is normal…common even. I suspect it is rare for a pilot to land without some amount of crosswind. The issue is just how strong a wind the planes are allowed to land in (I suspect there are rules for this but I do not know). What will get them more than the crosswind itself is a gusting crosswind. Some planes you can see are pointed in a distinctly different direction from the runway to overcome the crosswind while the plane was flying straight down the runway (and then they point the nose back on the runway at the last moment). Spooky how far out of line they can be (I once was able to see down the runway to the other end because of this despite sitting near the back of the plane). Nevertheless pilots train on that and generally handle it fine. The ones who get into what looks like more serious trouble are those caught by a strong gust. Pilots who land ahead of someone report conditions so follow-on pilots know what to expect but that only goes so far. Occasionally a plane gets caught out by these. Planes are reluctant to fly around needlessly. It is expensive (consume more fuel), complicates the control tower’s job, pisses off passengers and so on. It is scary for the passengers…I imagine the pilots leave with new gray hairs after landings like that. ---
**Author:** ![Robot\_Arm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robot_arm/32/18280_2.png) [@Robot\_Arm](https://boards.straightdope.com/u/Robot_Arm)\ **Post date:** [October 12, 2010, 9:49pm UTC](https://boards.straightdope.com/t/what-is-happening-when-the-airplane-lands/556909/28 "2010-10-12T21:49:45Z")
> [@EmAnJ](#): > > Why would a pilot attempt to land crosswind? Don’t airports have runways that run in different directions, so the pilot can land without having to attempt a landing in a crosswind? Are these crosswind landings happening at airports with only one runway? Would a commercial aircraft attempt a landing in those conditions? Lots of airports have runways in multiple directions, but not all. [Logan Airport](http://maps.google.com/maps?q=Logan+Airport&oe=UTF-8&ie=UTF8&hl=en&hq=&hnear=Logan+Airport+(BOS),+1+Fish+Pier+St+E,+Boston,+Suffolk,+Massachusetts+02128&ll=42.36292,-71.00318&spn=0.042935,0.082483&t=h&z=14) has runways going in all directions, [Sea-Tac](http://maps.google.com/maps?q=Sea-Tac&oe=UTF-8&ie=UTF8&hl=en&hq=&hnear=Seattle-Tacoma+International+Airport+(SEA),+Seattle,+King,+Washington+98188&t=h&z=13) has three runways, all parallel. (Remember, of course, that you can land on them in either direction.) The biggest factor may be how much land was available to build on, both when the airport was created and during expansion. Sea-Tac dates back to the '40s, when planes had propellors and Seattle was something of a backwater. Who knew they’d ever need more than one runway? As to that video, in two of the clips the planes are in Boeing colors, with extra instrumentation on the plane. Those were probably during testing. They may have deliberately sought out conditions to test crosswind landings. One of the other clips was from the old Kai Tak airport in Hong Kong. Land there was at a premium and the approach to the airport was notoriously hairy. Because of the mountains and buildings, you wouldn’t line up with the runway until just before touchdown. That pilot may have misjudged his turn and had to get back over the runway. ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [October 12, 2010, 9:53pm UTC](https://boards.straightdope.com/t/what-is-happening-when-the-airplane-lands/556909/29 "2010-10-12T21:53:42Z")
> [@EmAnJ](#): > > I’ve actually been considering that for years but I think the cost is pretty high to do something like that. Maybe I’ll look in to it some more. Tell me about it! I’ve been grounded this decade! (Stupid mortgage and car payment, and having been unemployed for a while! :mad: ) Getting a license is expensive. I think, though, that an ‘overcoming fear’ flight or two shouldn’t be too bad. A quick look shows that [Springbank Air](http://www.springbankair.com/) charges CDN$95/hour for a Cessna 172. (Curiously, they don’t rent them ‘wet’ – with fuel, which is normal here. Plan on about 32 litres per hour.) The instructor costs CDN$60/hour. They list ‘First Flight Lessons’ for $80/half-hour and $160/one hour. You might give them a call to see if they can help you out with lots of take-offs and landings, plus a bit of straight-and-level just to overcome your fear. There is a bit of danger, however. You may discover that you like it. In that case it can be very expensive indeed. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [October 12, 2010, 10:01pm UTC](https://boards.straightdope.com/t/what-is-happening-when-the-airplane-lands/556909/30 "2010-10-12T22:01:39Z")
> [@EmAnJ](#): > > If the engine whines (like it did on my am flight to LV), it freaks me out, like there may be something wrong with the engine. I was able to rationalize that it’s probably the first flight for that aircraft that day, so the engine was just cold. Sure enough, the sound went away after a while. I wonder if what you were hearing was the flaps being retracted. I have noticed on some airplanes the machine that winds them back in can be distinctly whiny. ---
**Author:** ![Magiver](https://avatars.discourse-cdn.com/v4/letter/m/4491bb/32.png) [@Magiver](https://boards.straightdope.com/u/Magiver)\ **Post date:** [October 12, 2010, 10:21pm UTC](https://boards.straightdope.com/t/what-is-happening-when-the-airplane-lands/556909/31 "2010-10-12T22:21:06Z")
> [@EmAnJ](#): > > All of my fear is irrational, and based on my lack of knowledge about the physics of flying. Mostly, I was/am nervous with turbulence, but last week, someone on SDMB linked to an article called ‘Ask the Pilot’, and in it, he said something about how turbulence is more a matter of passenger comfort for the pilot, not anything to worry about. For some reason, that helped. > > I guess my fear is a combination of things. As we’re taking off, I think ‘How come it’s taking so long to get up? We’re going to hit the end of the runway!’ and then as we lift, the groan of the plane is unnerving. If the engine whines (like it did on my am flight to LV), it freaks me out, like there may be something wrong with the engine. I was able to rationalize that it’s probably the first flight for that aircraft that day, so the engine was just cold. Sure enough, the sound went away after a while. > > Bumps that I can hear and feel below my feet while we’re in the air also make me nervous. Not sure why, and I usually tell myself it’s luggage falling in the compartment below. > > Moderate turbulence isn’t fun for me, though I’ve found that larger aircraft seem to experience less then the smaller, rural aircraft (which I fly on often). > > I enjoy the landing, though I’ve found that there seems to be a lot of turbulence when coming in for a landing, especially coming in the Calgary (home). I’ve had a couple of bad landings here, but luckily, the fact that I ‘survived’ it seems to help reduce my fear. > > I think another major reason for this fear is lack of control (a theme that seems to run my life - eating disorders, anxiety, etc., all seems to point back to this ‘lack of control’ issue). If I am in a corporate jet or Cessna (have been on a few occasions), where I can see the pilots and the instruments, I have less anxiety, even thought the flight may be more rough. I also have this issue when driving - I can’t sleep or take my eyes off the road if I am a passenger, most of the time. Your fear is not irrational but it may lack a little statistical relevance. I know seasoned airline pilots who greatly prefer to ride in the cockpit rather than in the passenger compartment specifically because of the sense of control it provides. ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [October 12, 2010, 11:07pm UTC](https://boards.straightdope.com/t/what-is-happening-when-the-airplane-lands/556909/32 "2010-10-12T23:07:42Z")
> [@EmAnJ](#): > > Why would a pilot attempt to land crosswind? Don’t airports have runways that run in different directions, so the pilot can land without having to attempt a landing in a crosswind? Are these crosswind landings happening at airports with only one runway? Would a commercial aircraft attempt a landing in those conditions? Cross wind landings are quite normal. Some airports have cross runways but then some don’t. There are many reasons why the duty runway would have a crosswind, it may be longer, it may be a better runway for traffic flow with respect to other airports in the area, in many cases it’s simply that the wind isn’t lined up precisely with the runway. You might have a 40 knot wind 30 degrees off set from the runway, that will result in about a 20 knot crosswind component and close to 40 knots headwind. In our aircraft we can take-off and land in up to 36 knots of crosswind. With reference to your OP, a jet will typically descend with the engines at idle. Because the wings on a jet are very efficient and they don’t have props to act as a big air-brake they are quite good gliders. Tubro-props are a bit different and will normally descend with power on. Back to the jet example, from a cruising altitude of say 35000 feet they will start the descent about 100 nm from the airport at idle power and essentially glide to the airport. Depending on ATC it is possible to keep the power at idle until quite late on final approach, however ATC may restrict the descent for traffic separation which may result in leveling off and applying power to maintain speed. As the jet gets lower, the air gets thicker and it naturally slows down, as it gets toward the final approach and with the airspeed reducing below the flap limiting speeds flaps will be progressively selected which further slows the jet down. Once below the gear extension speed the landing gear will be lowered, that further increases drag and reduces speed. Once the airspeed comes back to that desired for the approach and with landing flap set and the gear down power will be applied to maintain that speed and from then on the aircraft is flown to the runway with no other configuration changes. During the approach the spoilers will be armed and after touch down they will automatically deploy to dump lift from the wing. Many jets have automatic brakes that can be set for a certain strength and they will come on automatically after landing. Reverse thrust is not necessary to meet the landing performance requirements but is normally used anyway. This whole approach process will normally be flown by the autopilot with the pilots commanding speed changes and selecting gear and flaps at the appropriate times. It may also be flown by hand if the pilot wants to but hand flying increases the workload of the support pilot so it’s typically only down when the workload is expected to be low, e.g, little traffic and a straight forward approach. During the descent power may be applied if the speed gets lower than desired and air-brakes might be deployed if the speed gets too higher and the power is already at idle. The air-brakes feel like a rumbling vibration through the airframe and pilots normally avoid using them as unusual noises can disturb nervous flyers. ---
**Author:** ![mnemosyne](https://avatars.discourse-cdn.com/v4/letter/m/c4cdca/32.png) [@mnemosyne](https://boards.straightdope.com/u/mnemosyne)\ **Post date:** [October 13, 2010, 3:04am UTC](https://boards.straightdope.com/t/what-is-happening-when-the-airplane-lands/556909/33 "2010-10-13T03:04:33Z")
Hard landings are reportable events in Canada, and there is no report of one so far in the [CADORS](http://wwwapps.tc.gc.ca/Saf-Sec-Sur/2/cadors-screaq/m.aspx?lang=eng)for landings at Calgary this weekend. WestJet WJA 188 did hit a gopher, though, and US Airways AWE247 from Phoenix reported an unsafe gear, but the indication cleared before landing - I suppose if that was your flight, perhaps they had additional issues with the gear after touchdown. You can keep an eye on it if you’d like (the National Report is useful for that), but there’s a good chance that the landing you experienced might have been a bit of a bounced one, but not necessarily a “hard landing” based on the definition of speed/angle/whatever for the plane you were on. > [@EmAnJ](#): > > If the engine whines (like it did on my am flight to LV), it freaks me out, like there may be something wrong with the engine. I was able to rationalize that it’s probably the first flight for that aircraft that day, so the engine was just cold. Sure enough, the sound went away after a while. > > Bumps that I can hear and feel below my feet while we’re in the air also make me nervous. Not sure why, and I usually tell myself it’s luggage falling in the compartment below. Check your airplane ticket - were you flying on an Airbus A320 (318/319/321?)? I believe it’s the IAE engines (or Roll’s?) that have a characteristic whine on take off, while other engine types are more growly. It’s just part of the movement of the air/components inside that particular engine design engine as it produces high power - nothing to do with the cold. My husband can recognize an A320 with those engines based on take-off sound alone, as he’s had to work with them a lot. I’m sure other aircraft engines have weird noises like that too that are just part of their general design. It’s also incredibly unlikely that any luggage is falling around in the baggage compartment. What you’re hearing might be (early on) the landing gear retracting and doors closing (often a noise associated with a “bump” in the plane as it begins to fly more smoothly once the drag is removed. You feel a thump and bump when the gear are deployed due to the drag, too). In some planes - again, I think it’s more in the A320 family, there’s the Power Transfer Unit that has alternatively been described as barking/whining/thumping. It’s just balancing out the hydraulic pressures in the two (or more?) systems to keep everything working optimally. Other onboard systems might cause bumps and noises and vibrations in the plane as well. > [@Whack-a-Mole](#): > > I forget where I saw it but it was a wing loading test for some commercial jet. The whole thing happens on the ground and they put big hydraulic jacks on the wing and bend it upward. It is shocking how far it got before it failed (much further than would ever realistically occur in flight). > > I recall seeing the 787 on its maiden flight and being surprised at how much its wings flexed upward. It is a new design for a wing (carbon fiber) and I understand this flexing is absolutely normal and not an issue with that plane whatsoever. Heck…the wings are probably even stronger than most other commercial jets. > > Still…heckuva thing to see. Of course, the designers of the plane (and the pilots and passengers!) _want_ the wings to flex, because otherwise they’d snap right off in flight. Pay close attention to a conventional wing next time you’re on a plane - they move quite a bit too, though it’s possible the composite wings flex more - I just don’t know. I recently read that Bombardier stopped testing the CSeries wing at 150% flexing design limit because it met testing criteria and they wanted to keep it longer in order to do other stuff to it. [Here](http://www.youtube.com/watch?v=sA9Kato1CxA)’s a little video of the B787, where they actually bust the wing after 150%. Pretty cool. ---
**Author:** ![Kevbo](https://avatars.discourse-cdn.com/v4/letter/k/e47774/32.png) [@Kevbo](https://boards.straightdope.com/u/Kevbo)\ **Post date:** [October 13, 2010, 4:03am UTC](https://boards.straightdope.com/t/what-is-happening-when-the-airplane-lands/556909/34 "2010-10-13T04:03:47Z")
Wing tip vortices are an essential part of the mechanism by which wings produce lift. If you could eliminate them, the airplane wouldn’t fly. Winglets allow the wing to produce larger, slower turning vortices than a straight wing of similar span. They allow a shorter wing to mimic a longer one. Larger, slower vortices result in less drag, reducing fuel consumption. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [October 13, 2010, 6:07am UTC](https://boards.straightdope.com/t/what-is-happening-when-the-airplane-lands/556909/35 "2010-10-13T06:07:28Z")
> [@mnemosyne](#): > > Of course, the designers of the plane (and the pilots and passengers!) _want_ the wings to flex, because otherwise they’d snap right off in flight. Pay close attention to a conventional wing next time you’re on a plane - they move quite a bit too… Oh I know it. Been on more than a few flights where the wings are positively flapping like a bird. A little disconcerting but I know full well they are designed to do so and it is a good thing else, as you mention, they’d snap. Indeed many things we consider rigid flex and are meant to do so. I’ve been on the upper floors of skyscrapers where the building’s sway was evident. In that case you cannot see it from the outside or even feel it but you can see its effects (on things like chandeliers swaying). ---
**Author:** ![standingwave](https://avatars.discourse-cdn.com/v4/letter/s/9de0a6/32.png) [@standingwave](https://boards.straightdope.com/u/standingwave)\ **Post date:** [October 13, 2010, 7:44am UTC](https://boards.straightdope.com/t/what-is-happening-when-the-airplane-lands/556909/36 "2010-10-13T07:44:39Z")
> [@EmAnJ](#): > > All of my fear is irrational, and based on my lack of knowledge about the physics of flying. It helps to appreciate how insanely tough modern airliners are. A friend of mine was an mechanical engineer for Boeing and he told me once about the wing tests. Incredible! Check out [this article](http://www.komonews.com/news/boeing/89392307.html) which has a picture of a 787 undergoing wing load testing. Wings can take an amazing amount of abuse. ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [October 13, 2010, 12:20pm UTC](https://boards.straightdope.com/t/what-is-happening-when-the-airplane-lands/556909/37 "2010-10-13T12:20:30Z")
> [@mnemosyne](#): > > > [@EmAnJ](#): > > > > If the engine whines (like it did on my am flight to LV), it freaks me out, like there may be something wrong with the engine. I was able to rationalize that it’s probably the first flight for that aircraft that day, so the engine was just cold. Sure enough, the sound went away after a while. > > Check your airplane ticket - were you flying on an Airbus A320 (318/319/321?)? I believe it’s the IAE engines (or Roll’s?) that have a characteristic whine on take off, while other engine types are more growly. It’s just part of the movement of the air/components inside that particular engine design engine as it produces high power - nothing to do with the cold. My husband can recognize an A320 with those engines based on take-off sound alone, as he’s had to work with them a lot. > > I’m sure other aircraft engines have weird noises like that too that are just part of their general design. I’m pretty sure the whiny sound of these engines during takeoff is a characteristic of [high bypass ratio turbofan engines.](http://en.wikipedia.org/wiki/Turbofan) These are engines in which the fan disc (visible at the front of the engine) moves a lot of extra air through the nacelle, but _outside_ of the engine (in addition to cramming the usual amount of air directly into the engine itself). Not just the A-320, many other large planes (Boeing 747 and 757 come immediately to mind) also use high bypass ratio turbofans because they are quieter for a given level of thrust than other engines. I believe the whine is related to operating the engine at a high power setting (sucking a lot of air through it) while the aircraft is moving forward at a relatively low speed, typically 200-300 MPH during the early part of the ascent. As the plane approaches cruise speed (typically 500-600 MPH), the forward speed of the aircraft is helping to stuff air into the engines, resulting in a different angle of impingement of the air on the blades of those big fan discs, and causing the whining noise to fade away. A clear demonstration of the whining noise can be seen in [this video,](http://www.alexisparkinn.com/photogallery/Videos/2006-757_departure.wmv) which shows a Boeing 757 at an airshow doing a low-altitude, high-speed flyby (followed by a 45-degree climbout). As he crosses the far edge of the airfield at the start of the video you can hear that characteristic whine as the engines spin up to full power. According to [the source page](http://www.alexisparkinn.com/airliners_videos.htm) (other cool vids there, BTW), the speed of the pass was about 350 knots (~400 MPH). > [@EmAnJ](#): > > Bumps that I can hear and feel below my feet while we’re in the air also make me nervous. Not sure why, and I usually tell myself it’s luggage falling in the compartment below. Pretty sure that’s the landing gear being retracted shortly after liftoff (and extended shortly before landing). ---
**Author:** ![EmAnJ](https://avatars.discourse-cdn.com/v4/letter/e/d2c977/32.png) [@EmAnJ](https://boards.straightdope.com/u/EmAnJ)\ **Post date:** [October 13, 2010, 12:28pm UTC](https://boards.straightdope.com/t/what-is-happening-when-the-airplane-lands/556909/38 "2010-10-13T12:28:19Z")
> [@mnemosyne](#): > > Hard landings are reportable events in Canada, and there is no report of one so far in the [CADORS](http://wwwapps.tc.gc.ca/Saf-Sec-Sur/2/cadors-screaq/m.aspx?lang=eng)for landings at Calgary this weekend. The hard landing was on the flight to Las Vegas. Is there something similar for the US? ---
**Author:** ![EmAnJ](https://avatars.discourse-cdn.com/v4/letter/e/d2c977/32.png) [@EmAnJ](https://boards.straightdope.com/u/EmAnJ)\ **Post date:** [October 13, 2010, 12:34pm UTC](https://boards.straightdope.com/t/what-is-happening-when-the-airplane-lands/556909/39 "2010-10-13T12:34:22Z")
> [@mnemosyne](#): > > It’s also incredibly unlikely that any luggage is falling around in the baggage compartment. What you’re hearing might be (early on) the landing gear retracting and doors closing (often a noise associated with a “bump” in the plane as it begins to fly more smoothly once the drag is removed. You feel a thump and bump when the gear are deployed due to the drag, too). In some planes - again, I think it’s more in the A320 family, there’s the Power Transfer Unit that has alternatively been described as barking/whining/thumping. It’s just balancing out the hydraulic pressures in the two (or more?) systems to keep everything working optimally. Other onboard systems might cause bumps and noises and vibrations in the plane as well. > [@](#): > > Pretty sure that’s the landing gear being retracted shortly after liftoff (and extended shortly before landing). The bumps I’m feeling happens mid-flight - I know what the landing gear retracting feels like. I’m guessing it’s probably the Power Transfer Unit \*\* mnemosyne\*\* mentions. Also, you guys are awesome! Thank you! ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [October 13, 2010, 12:38pm UTC](https://boards.straightdope.com/t/what-is-happening-when-the-airplane-lands/556909/40 "2010-10-13T12:38:28Z")
> [@EmAnJ](#): > > I think another major reason for this fear is lack of control (a theme that seems to run my life - eating disorders, anxiety, etc., all seems to point back to this ‘lack of control’ issue). I think this is something that causes anxiety for nearly every airline passenger at some point. The best pilots are _extremely_ smooth at the controls, to the point that if you close your eyes you can’t tell when the plane is changing direction; you’d swear they were professional limo drivers in a previous life, they’r e that smooth. The worst pilots seem to think their job is to demonstrate the maneuverability of the aircraft by performing snap turns, sudden changes in pitch, and making large, sudden changes to the engine power settings. I’ve been flying since I was a little kid and I usually enjoy it, but pilots who fly like this make me nervous because when I feel a sudden change like that, my visceral reaction is to wonder if we’re dodging other air traffic. [Previous page](https://boards.straightdope.com/t/what-is-happening-when-the-airplane-lands/556909.md?page=1) [Next page](https://boards.straightdope.com/t/what-is-happening-when-the-airplane-lands/556909.md?page=3)