What altitudes do propeller driven airplanes usually fly at?

Answer 1

This is left up to the discretion of the pilot, and different pilots have different approaches to the question of what altitude to fly at. Furthermore, weather often plays a vital role in dictating what altitude any given flight will eventually be flown at.

There are some rules and guidelines, some of these are...

Eastbound airplanes are generally supposed to cruise at odd-thousands plus 500 feet. 3,500 5,500 7,500 and so on while westbound airplanes are generally supposed to cruise at even thousands plus 500 2,500 4,500 6,500. This is done for traffic separation purposes. It is hoped that with this system airplanes traveling in opposite directions (which are the hardest to spot) will thus be separated by 1000 feet of altitude even if they are otherwise completely unaware of eachother.

Another important consideration is oxygen. The FAA mandates that any flight crew flying at 12,500 feet or higher for more than 30 minutes, or higher than 14,000 feet for any period of time must use supplemental oxygen. It is also required to provide oxygen for passengers if the aircraft flies higher than 15,000 feet. Airliners and the like all have pressurized cockpits so that the "cabin altitude" (the air density of the cabin) never exceeds 8,000 feet even though the aircraft itself may fly well above 20,000 feet. Some small propeller-driven aircraft have pressurized cockpits, but most do not. Of the ones that do not, some have built-in oxygen systems, most do not. The pilot may bring a portable oxygen system if he intends to fly this high, but this is expensive and cumbersome, so most pilots who do not have pressurized cabins in their aircraft will stay below these altitudes.

Something else to be considered is airspace rules. Any aircraft flying through clouds or above 18,000 feet must comply with a whole new set of rules (IFR or Instrument Flight Rules) which keeps the aircraft constantly under the watchful eye of air traffic control. This is in contrast to VFR or Visual Flight Rules where the pilot is more or less free to do as he pleases. Many pilots of small propeller-driven airplanes are not certified to fly IFR, and are thus prohibited from flying into these areas. Such pilots must maintain a certain amount of distance horizontally or vertically from any cloud layers or risk entering a very dangerous situation. Meanwhile, a pilot who IS IFR certified may specifically fly through a rainy cloud layer to get on top where its a beautiful sunny day (after having gotten permission from ATC).

The ground is also something which is always on a pilots mind. The altitude of the ground above sea level changes from place to place. Ground elevation in my home town of Kansas City for example, varies from 700 to 1000 feet above sea level. Towers are also an important consideration and a smart pilot will always plan his flight to be well above any obstructions. Turbulence levels and wind directions can change drastically from one altitude to the next, and a pilot may choose an altitude that gives him a "free ride" with the wind at his back, or may choose to fly at a specific height to avoid turbulence.

Another thing to consider is fuel effiency. Some airplanes have a special type of propeller (a constant speed propeller) which allows them to use their engine power more efficiently at high altitudes. Since the air pressure is lower up there, you lean the fuel mixture, and thus burn less fuel with each combustion cycle. This can save a frugal pilot a lot of money if he uses it carefully.

All things being equal, on a sunny day with no clouds, no wind, and no particular hurry, i will usually fly between 3,000 and 7,000 feet above ground level. The view is nice from up there, its easy to spot landmarks, but you still have plenty of altitude to spare in case something bad happens. "Altitude equals safety" is an old flying adage.