Page 205 - Understanding Flight

CH07_Anderson 7/25/01 9:00 AM Page 192

192 CHAPTER SEVEN

100 % max. range

99% max. range
Distance/fuel

Speed

Fig. 7.11. Fuel consumption as a function of speed.

Turns

Now that we have the airplane in flight, let us make a turn. Unfortu-
nately, for commercial and general-aviation airplanes, turns are hardly
interesting. If they were, passengers would complain. (However, to
someone not familiar with a 2g turn, this might still qualify as inter-
esting.) High-performance turns are primarily the domain of fighter
and aerobatic aircraft.
In the discussion of the climb we saw that the engine, not the wing,
is lifting the airplane. But it is the wing that makes a turn. Recall that
in Chapter 1 we saw that the load on the wing (and the pilot)
increases when an airplane goes into a bank. In a turn the load factor
and stall angle of attack become two critical components in
An average pilot can withstand
understanding turn performance (refer to Figures 1.6 and 1.7).
about 6 g’s for a few seconds
The load factor is just like real weight as far as the wing is
without blacking out.
concerned. We know that the induced power and induced
drag vary as the load squared. So when an airplane makes a
2g turn the induced power and induced drag (which are important in
most turns) have gone up by a factor of 4.
With this reviewed, let us look at an easy (not high-performance)
turn with a bank angle of 45 degrees. This turn will put a force on the