Figure 10-28. Best power mixture range.
This graph is designed to tell the TAS performance of the
airplane depending on the altitude, temperature, and power
setting. Using Figure 10-29, find the TAS performance based
on the given information.
Sample Problem 9
OAT.........................................................................16 °C
Pressure Altitude...............................................6,000 feet
Power Setting................................65 percent, best power
Wheel Fairings..............................................Not installed |
Begin by finding the correct OAT on the bottom, left side of
the graph. Move up that line until it intersects the pressure
altitude of 6,000 feet. Draw a line straight across to the
65 percent, best power line. This is the solid line, which
represents best economy. Draw a line straight down from
this intersection to the bottom of the graph. The TAS at 65
percent best power is 140 knots. However, it is necessary
to subtract 8 knots from the speed since there are no wheel
fairings. This note is listed under the title and conditions.
The TAS will be 132 knots.
Crosswind and Headwind Component Chart
Every aircraft is tested according to Federal Aviation
Administration (FAA) regulations prior to certification. The
aircraft is tested by a pilot with average piloting skills in
90° crosswinds with a velocity up to 0.2 VSO or two-tenths
of the aircraft's stalling speed with power off, gear down,
and flaps down. This means that if the stalling speed of the
aircraft is 45 knots, it must be capable of landing in a 9-knot,
90° crosswind. The maximum demonstrated crosswind
component is published in the AFM/POH. The crosswind and
headwind component chart allows for figuring the headwind
and crosswind component for any given wind direction and
velocity.
Sample Problem 10
Runway..........................................................................17
Wind........................................................140° at 25 knots
Refer to Figure 10-30 to solve this problem. First, determine
how many degrees difference there is between the runway
and the wind direction. It is known that runway 17 means
a direction of 170°; from that subtract the wind direction of
140°. This gives a 30° angular difference, or wind angle. Next,
locate the 30° mark and draw a line from there until it intersects
the correct wind velocity of 25 knots. From there, draw a
line straight down and a line straight across. The headwind
component is 22 knots and the crosswind component is 13
knots. This information is important when taking off and
landing so that, first of all, the appropriate runway can be
picked if more than one exists at a particular airport, but also
so that the aircraft is not pushed beyond its tested limits. |