Page 210 - Understanding Flight

CH07_Anderson 7/25/01 9:01 AM Page 197

Airplane Performance 197

maximum load factor. So, at higher altitudes, the best turn During WWII, the “grasshoppers,”
performance decreases. airplanes such as the Piper Cub,
There is one caveat that allows tighter turns despite the loss had the lowest combat losses. In
of power available. The pilot can choose to “buy” power with one case, a Cub pilot, jumped by
altitude. In other words, in a descending turn, the pilot can a German fighter, managed to
supplement the engine power with the power it used to climb turn, land in a field, and hide the
to altitude in the first place (like a car going down a hill it first airplane in the time it took the
had to climb). This is why fighter airplanes engage at high German fighter to turn around.
altitudes but the fight progresses to lower altitudes. The
airplanes are using altitude to tighten their turns.

STANDARD-RATE TURNS
The turning rate is usually not a critical design issue for
aircraft other than fighters and specialized acrobatic airplanes.
However, all aircraft must be able to perform a standard-rate
turn. A standard rate turn for light airplanes is defined as a 3
degrees/s turn, which completes a 360-degree turn in 2
minutes.This is known as a 2-minute turn. For heavy airplanes
a standard-rate turn is a 4-minute turn. Instruments, either the
turn and slip indicator or the turn coordinator, have the
standard-rate turn clearly marked. Light aircraft are equipped
with 2-minute turn indicators while heavy aircraft are
equipped with 4-minute turn indicators.This is very useful to
pilots who are out of visual contact with the ground and for
air-traffic control when appropriate separation of aircraft is
desired.The pilot banks the airplane such that the turn and
slip indicator points to the standard-rate turn mark and then
uses a watch to time the turn.The pilot can pull out at any
desired direction depending on the length of time in the turn.
Note that the standard-rate turn should be well below the
maximum turning rate.

Landing

What goes up must come down. So another performance parameter is
landing distance. Landing distance is easier to understand than takeoff