# Homework Help: Plane Landing Question

1. May 29, 2007

### rtreska

Ok so I'm quite new here and I have been asigned an assignment in my grade 12 Physics class where I must find a novel (any novel) and analyze any physics concepts in it. Currently I have picked up Clyve Cussler's "Cyclops" and have found a few scenarios that include physics. One of them is where the narrator describes a plane landing at a speed over 200 miles an hour and says that she (one of the characters) would tear her self to peices. Now I'm just wondering what can I describe and what kind of calculations I can present to my class. Any examples or calculations that you guys may think are realevent would be greatly appriciated!

By the way does any one know any other novels in which I can analyze some physics concepts in? If so please let me know. Thank you for all your help, I really appriciate it.

2. May 29, 2007

### Danger

Welcome to PF, Rtreska.
With a good pilot at the controls, and a good runway, a 200 mph landing is well within reason.
There are boundary effects as with any landing, and they'll be much more significant at that speed. That's the ground effect responsible for an aeroplane 'floating' just before touchdown. Essentially, air gets trapped between the wings and the ground, which drastically increases their effective lift. It's also tougher to compensate for a cross-wind (particularly gusting) because you have to react faster.
I'd be more concerned about blowing a tire. The wheels have a certain amount of inertia which makes them reluctant to start spinning. If you've watched commercial or military birds set down, you've probably seen little puffs of smoke coming from the gear. That's rubber burning off of the tires from the friction of them scraping along the runway before they start to turn. The faster the landing, the more pronounced that effect is. It's the same idea as slamming on the brakes in a car.
Of course, the type of plane is important as well. Some aren't built to even fly that fast, never mind land. How they're constructed is critical.

Last edited: May 29, 2007
3. May 29, 2007

### AlephZero

The "normal" landing speed of commerical aircraft is about 150 mph. See
http://www.geocities.com/capecanaveral/Lab/8803/tech_wb.htm

There is a good reason why the landing speeds of different aircraft types are similar: at a busy airfield, air traffic controllers have a much easier life when everybody flies at the same speed and keeps a constant distance from the plane in front of them!. AFAIK the normal "speed limit" close to commercial airfields is 200 knots (a bit more than 200mph), for the same basic reason.

The standard angle of approach is 3 degrees, so the vertical speed on a 150 mph touchdown is about 150 sin 3 degrees = 8 mph (or less, because of the ground effect, as Danger said).

Assuming the book is talikng about human passengers (I dunno, I haven't read it!) the thing that would would "tear the passenger to pieces" is high deceleration, not high speed.

4. May 30, 2007