I have a fear of flying, but through a lot of reading (about the safety of flying and airplanes in general) and sucking it up and doing it anyway, I’ve become a better flyer. I still hate take off and come close to panic attacks almost every time, but am getting better at dealing with turbulence, and love the landing (back on the ground, yay!).
I have been flying a lot lately, both for personal vacations and work trips, and am curious about what is happening as we come in for a landing. I feel the airplane slow, but how? When we touch down, it sounds like they reverse engine thrust - do they? What else is going on as we are coming in for final approach?
I just got back from Vegas last night, and when we landed there on the 7th, it was a HARD landing. It almost felt like we had the nose up too much and BAM, hard touch down for the rear of the plane. Why did this happen? Just pilot error or something else? Wind?
Links to information would be helpful, as well as personal experience / knowledge!
The plane essentially does a controlled fall. It gets held up by air passing over the wings, right? Well the idea is to slow the plane down enough so that it doesn’t get enough lift to stay up.
The pilot can slow the plane down by extending flaps. You’ll hear a mechanical hum when this is happening. If you have a wing seat, you’ll see the flaps start to extend outward from the inner half of the wings, on the trailing edge. This causes more lift and more drag. So the plane doesn’t need as much speed to stay up.
Then the plane will pitch up a little (5 or 10 degrees) to get even more lift and more drag. When the pilot wants to bring the plane down, he points the nose down and thus loses some lift. For a prolonged fall, he can pull the throttle back and let the plane fall just by lack of thrust.
When you land, you’ll see flaps lift vertically up from the wing surface. Those are spoilers, which stop the plane. You may also hear antithrusters, which also stop the plane.
What else do you want to know?
Yep. It’s wing vortices. There’s a high pressure zone below the wing, right? And a low pressure one above it? Well, air at the end of the wing tries to wrap around the tip of the wing. So instead of flowing off the trailing edge, it goes off at an angle. Since there’s less air on the bottom near the tip, air on the bottom near the middle moves to fill that void. This chain of effect happens all along the bottom of the wing. So you get a flow from the fuselage to the wingtip.
Then, on top of the wing, there’s more air coming up from the bottom at the tip, so that wing tip air is pushed toward the middle of the wing, and that pushes air in the middle toward the fuselage, and so on. That makes a flow from the tip to the fuselag, the opposite of what’s going on underneath the wing. So you get this spiral that develops. That’s a wingtip vortex.
The bent tip prevents air on the bottom from coming to the top. Well, as easily, anyway. The vortices are part of induced drag, which is drag caused by the production of lift. I honestly don’t have a good handle on how that’s different from aerodynamic drag, but you can read about it here. The point to remember is that the more the airstream flows sideways, the less it’s doing its job of lifting the airplane. Less lift means a higher angle of attack, which means more drag.
I’m trying to decide if you’re right about this. My first instinct was that the treadmill would have no effect other than maybe making the wheels turn faster, since that’s what would happen with a plane taking off from a treadmill.
But thinking about it some more I don’t think that’s necessarily true since there is no forward thrust when you’re landing.
However there is forward momentum. So I’m not sure about what would happen. In the case of a jet, you also have to consider the reverse thrusters. Hmm…
Thrust reversers are used on most (probably all) commercial jets.
There are different designs for different engines but all achieve the same effect of reversing the thrust to help slow the plane.
Here is a clamshell thrust reverser deployed (you can see them closed behind the engine which redirects the thrust forward). Note in that pic you can also easily see the flaps deployed at the back of the wing. In normal flight those retract up and back into the wing. Along the top of the left wing you can see the air foils deployed upward which provide some drag and stopping power as well.
Once deployed you hear the engines roar for a few seconds as the pilot throttles them up to provide stopping power.
The plane also has brakes just like on your car (albeit a lot bigger).
While not exactly common yet crushable concrete (do not know its proper name) is being deployed at more airports all the time for a plane that overruns the end of the runway. Basically the weight of the plane causes it to sink into the special concrete making it akin to the plane driving through sand which slows it down very fast if all else fails to stop you.
As mentioned above on approach the pilot deploys flaps which essentially make the wing bigger. This increases drag (slowing the plane down) and increases lift. The upshot is the plane can stay airborne at a slower speed (so you can hit the runway at 135mph and not 200mph). At the last moment the pilot will flare its nose up which causes speed to drop even more and cause it to “fall” the last few feet to the ground (a slow and light and controlled fall…shock absorbers do the rest). Then nose down then braking.
Some landings are harder than others for a variety of reasons. Sometimes the pilot just handles not as well as other times. More often though it is circumstances of that landing. If there is a lot of windshear the pilot may have to come in faster to maintain control. On occasion the windshear can make for very hairy landings (I’ll spare you the YouTube videos of some shocking landings…was on one myself and not fun and I like flying).
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. So I’m thinking that the treadmill will only make your tires spin faster. That will, of course, mean there’s more energy to take out of them, but I doubt it’ll be more than if I just used the elevator.
This I had no idea about, but looking at the pictures and diagram you posted, that makes sense.
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.
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?
One of my flight instructors showed me something interesting once. (We were in a four-seat Cessna at the time, see more below.) We had the plane perfectly balanced and trimmed, flying straight and level at 80mph. I took my hands off the controls, no problem. I pulled the throttle back (like taking your foot off the gas) and the plane started to descend. I pushed the throttle in and we leveled off; a little more and we started to climb. All the while going 80mph.
If the pilot just pushes the stick forward, the plane will descend, but it will pick up a lot of speed (like going downhill in a car or bike) which is not what you want when you’re landing. There is a theory of flying that the stick (wheel, yoke, whatever) controls how fast you go, and the throttle makes you go up and down.
Not quite true, from what I understand. But tricky to explain.
Imagine you’re standing next to a scale, one foot on the floor and one foot on the scale itself. You can shift your weight so that the scale barely reads anything, or you can put the weight on your scale foot, and the scale will show almost your full weight.
When a plane first touches the runway, it’s going almost fast enough to be flying. The wheels are on the ground, but the wings are still carrying most of the weight. The pilot deploys the spoilers to spoil the lift of the wing. Now that the wheels are firmly on the ground, the brakes and steering will work a lot better.
(Spoilers are useful for descending without picking up too much speed. Didn’t have them on that Cessna.)
There a scene at the end of Die Hard 2 that shows them perfectly. As one of the planes is landing and passes through some smoke, there a perfect shot of the smoke getting caught in the vortex behind the wingtip.
Must post link to the Gimli Glider story. A 767 rather than a 747 and not exactly a belly landing (no front nose gear) but close enough. Great story (and a happy ending…not giving it away since the pic in the link tells that much).
Good, short read. If you haven’t (whoever is reading this) give it a look.
These are the flaps at the rear of the wing that you’re talking about. On takeoff, they’re extended just a bit to increase lift, but for landing they’re extended and lowered quite a lot, which increases lift and also increases drag, allowing the plane to lose altitude without building up a whole lot of speed. If you’re seated behind the wing and have a view out the window, you’ll see these being extended in steps as you get closer and closer to the airport.
If you’re seated in front of the wing, you may be able to look back and see the [deploy on the leading edge of the wing. When the plane is flying in a nose-high orientation, these help the air wrap around the top surface of the wing without separating from it, which otherwise would reduce lift and cause the airplane to fall.
Deployment of these lift-enhancing devices may increase the wind noise when it happens. The other noisy thing is the landing gear, usually lowered a few minutes before touchdown. They add quite a bit of noise, and you’ll often hear some thumping around below the floor as the doors open and the gear come out and lock into place.
As has been noted, many commercial aircraft use thrust reversers on conjunction with the brakes on the landing gear, though I have been on commercial flights that skipped the thrust reversers altogether (perhaps they were lightly loaded flights?). One other thing you will see is that as soon as the wheels touch down on the runway, [url=Spoiler (aeronautics) - Wikipedia]spoilers](Leading-edge slat - Wikipedia) (large panels on the top surface of the wing) raise up. These “spoil” the lift-producing ability of the wings, causing the plane to settle firmly on its wheels and giving them the traction needed for heavy braking. The spoilers will also create lots of aero drag in this configuration, further contributing to deceleration. It can be disconcerting to look out the window and realize that with the flaps fully extended and the spoilers fully raised, you can see right through the damn wing, but no worries - the strength of the wing lies within the hidden area forward of those devices.
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.
