I was watching the airplanes come in for a landing at Pearson last night during the ice-pellets storm, and wondered: the runways would be fairly slick, right? Do landing airplanes use mostly reverse thrust to slow down once on the runway, or do they also use wheel brakes? Seems that wheel brakes would be a bit iffy in these kinds of conditions…
They use both if you are just talking about large jets. Jets have reverse thrusters that they use heavily when they first touch down and then they rely on the brakes. You can usually hear and feel when they activate the reverse thrusters when you fly as a passenger.
Piston driven airplanes don’t have a similar mechanism. They rely largely on brakes other some have controls that add aerodynamic braking as well.
You are right that pilots have to be careful with the brakes on an icy runway. Planes can and do skid if the brakes are used to heavily when the plane touches down. That can be dangerous of course. The pilots act just like you would if you were driving a car on that runway. Be gentle with the brakes and maybe even pulse them a little to keep them from locking up.
Yes.
Jets use a combination of wheel brakes, reverse engine thrust, and spoilers (so-called “air brakes”) to stop on runways. In potentially hazardous conditions like icing, the airport will issue in its automated messages a warning like “reported braking action poor” or something as an indication that pilots should minimize the use of wheel brakes.
Prop planes like turboprops also have reverse-pitch capabilities on the propellers. Smaller planes like Cessnas and the like only have wheel brakes, so you have to be careful how you apply them.
When I was flying Cessnas almost all of my landings were full-stall, power-off. I just like to land that way. (This habit interfered with my helicopter training.) Since I almost always flew dad’s Cessna 172, and since he didn’t want to buy brakes all the time, this is how I landed:
I’d come in with full 40° flaps and the power set to idle. My wheels would touch down on the numbers. I’d hold the nose up for aerodynamic braking and swat the flaps up to get more weight on the gear. I’d hold the nose up as long as it would stay up. I always made the turnoff – and if it was particularly windy I’d have to add power while taxiing.
Just don’t use beta range in-flight! I’ve heard of twin-engine turboprop crashes that seemed to have been caused when the pilot selected beta range to slow descend more rapidly. If the props don’t go back at the same time, you can roll it. (Do single-engine turboprops have beta?)
On jetliners, most of the braking effort comes from the wheel brakes; the thrust reversers contribute very little.
The reason for the “spoilers” you see rising from the trailing edge of the wing during braking is not for aerodynamic braking, but to kill the wing’s lift, to get more weight on the wheels, so braking can be more effective.
Learn a new thing everyday. I always had assumed that something like a 747 had wheel brakes for crusiing the tarmac, but used reverse thrust for the big jobs, such as stopping itself.
Of course, some pilots slow down by throwing out an anchor. (Or at least using a metal hook to snag a wire. 
)
The last couple of times I have come back to land at Gatwick (at night) I was amazed that no reverse thrust seemed to be used at all, just air & wheel brakes.
I thought perhaps this was due to the aircraft type (which I cant remember) being better able to stop without the need for reverse thrust, but I think there are restrictions on the use of reverse thrust at night, due to the increased noise level it creates.
The spoilers create downforce, correct? Like the flaps used in NASCAR to make the crashes less spectacular (and protect the drivers, of course)?
I have to disagree or ask for a cite. Of course I’ve been wrong plenty of times so I say this in a pleasant sense, of course.
That said, since the spoilers work as aribrakes when airborne why wouldn’t they be just as effective on the ground? And the wheel brakes give a distinct nose-down ptiching moment to the aircraft on application that you don’t feel when only the thrust reversers are applied. What I mean is that immediately after touchdown and one hears the TR’s applied there is a very even deceleration. As you approach the runway turnoff and they start getting on the wheel brakes you get a sort of nose-down jerkiness on application.
Of course I could be remembering selectively. My buddy is a Captain with Continental and if I can get a hold of him I’ll see if I can get the full skinny. Or maybe there are some left-handers floatin’ around reading this…
Must issue the disclaimer that I’m a small plane pilot (in fact, many landings I don’t use brakes at all, just let it roll it a stop if there’s sufficient runway), but I would expect the spoilers on a big jet would BOTH kill lift - putting more weight on the wheels and making wheel brakes more effective - AND provide aerodynamic braking.
I’m not a pilot but this doesn’t sound right. The only reason big jets even have thrust-reversers is for stopping after landing. I also can’t believe that the TR wouldn’d be like 1000 times better, being right along the planes center of mass & strength (as opposed to way down at the wheels).
… And then there were the QANTAS bean counters saving money for the airline by requiring pilots to not follow Boeing standard braking protocols, resulting in the 1999 QANTAS 747 crash in Bangkok.
A related question suggested by this thread: do planes have ABS? If not, why not?
As I said above, I think some planes can slow down after landing without using reverse thrust. A lot of airports do not allow the use of reverse thrust (above idle settings) during certain night-time periods (2200-0600) for example.
So planes have to be able to land and slow to a stop with reverse thrust set to idle, or they cant use that airport.
I’m pretty sure I read in this forum recently that newer planes do have ABS. In large planes without ABS, it is apparently relatively easy to lock up a wheel with aggressive braking.
I’ll try to find a cite.
This is what I was thinking of:
From this thread, CookingWithGas provided this link, which states, in part:
Apparently, anti-lock braking systems were first developed for use in aircraft.
Cite:
http://www.mercedes-benz.com/e/innovation/rd/forschung_nov96.htm
BTW, a closer read of the website linked to in my last post suggests that the guy may need a tinfoil hat.
excuse my ignorance but how does a reverse thruster work? They can’t be operating the whole jet engine in reverse can they?