Landings

A recent question came up about landing a plane. The question was "Why are some landings smooth and others hard?"

Well, first let me say that my landings are always smooth. That's a joke for those who have piloted a plane before. The reality of it is that not all landings can be smooth. While we pilots strive for that each and every time, we don't always get them.

Why?

There are several things happening during a landing. First off, the pilot is flying the plane. Many assume the auto pilot is landing the plane (see auto landings in a separate post). The pilot is busy correcting for changing wind conditions, modulating the power to maintain a desired airspeed and then at the last second, he/she will "Flare". A Flare is a maneuver where the pilot slows the descent to allow a smooth touchdown.

Things that can go wrong (for the pilot):

-Wind gust: a wind gust will sometimes add airspeed causing the plane to float like a balloon (known as ballooning) momentarily. This has to be corrected with precise control inputs so as to not fly to far down the runway making it hard to stop after touch down. Also the pilot is trying to prevent the plane from dropping onto the runway (hard landing) after the gust has subsided.

-Visual Illusion: pilots typically fly into airports that have similar sized runways in both length and width. As such, they get used to seeing a certain 'picture' when landing and will unconsciously maneuver the plane to land in that picture. The problem arises when the runway is much longer or shorter than the pilot is used to, or if its much narrower or wider than normal.
This can cause the pilot to flare too high or too low. Too high and the plane will ballon, too low and, well hard landing.

-Wind shear: if the wind were to shift from in front to behind (headwind to tailwind) during the flare, the resulting feeling is that the 'bottom falls out'. This too will result in a hard landing.

There are other things such as airport lighting, visibility and time of day (sunlight) that could affect the landing but a good pilot will always make a safe landing and make it as smooth as possible.