Wednesday, November 30, -0001
How to make every runway seem longer
What Makes a Runway Short?
The Psychological Factors
Ignoring everything having to do with an airplane's performance, a runway is universally considered short when it's significantly shorter than what we're used to. It's a mental thing that may have nothing to do with reality because almost every "normal" general aviation airplane (as opposed to special short-field birds) will land and take off in a space that's far shorter than the average pilot is willing to challenge. For instance, a quick study of available stats shows that a Cessna 152 requires less than 500 feet to stop, while Cherokees, 172s and such all fall into a required runway range of 550 to 650 feet. Bonanzas fall into the under-800-foot range. These are factory specs, measured at gross weight with zero wind, around 60 degrees at sea level with moderate (not severe) braking.
Look back at those numbers, and yes, they're accurate. But, they're rollout distances only, measured at the factory from where the tires first touched to where our trusty bird stopped. But, even if we were to add 300 feet to each, how many average pilots are willing to take their C-172 and such into a runway that's less than 1,000 feet long? In fact, how many pilots, in general, have ever turned final to 1,000 feet of runway? It looks tiny. Impossible to land on! It's very intimidating, and many pilots would avoid it, if given a choice. Other pilots who love short-field work, however, wouldn't bat an eye at it because it's not out of their comfort zone. So, short is relative to what we're used to. However, there are other factors that do make a runway short.
First, it could be said that what's short for one airplane can be too much for another. A thousand-foot runway in a Cub is like turning it loose at JFK, while a loaded Cirrus might be out of luck: It needs 1,140 feet to land and 1,600 to take off. Most aircraft require more to take off than land. However, ignoring the limitations of the hardware, other non-aircraft related factors can make a runway short almost regardless of its length.
Bad approaches. Tall trees, etc., at the thresholds can make a 3,000-foot runway short because not all of it's accessible.
High altitude. Thin air means the airplane will be carrying more ground speed than at a lower altitude, and the engine won't be putting out as much horsepower.
High temperatures. Along with altitude, temperatures increase/decrease the density altitude and can greatly affect the way an airplane can perform on a given runway.
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