Rally Pilot Operating Handbook
Copyright 2008, Rally Aircraft
Revision 4.1
25
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Total distance to clear a 50 ft obstacle .............. 1,300 ft
These distances are well within the available takeoff field length; however, a correc-
tion for the effect of wind may be made based on
Note 3
of the takeoff chart: de-
crease the ground roll by 10% for 10 knots head wind. The correction for a 13 knots
headwind is:
(13 knots ÷ 10 knots) x 10 = 13%
This results in the following distances, corrected for wind:
a) Ground roll (zero wind) ............................... 550 ft
b) Decrease in ground roll (550ft x 13%) ........ 70 ft
c) Corrected ground roll (a-b) .......................... 470 ft
d) Total distance to clear a 50 ft obstacle (zero wind) ....... 1,300 ft
e) Decrease in total distance (4300 ft x 13%) .................... 170 ft
f) Corrected total distance to clear a 50 ft obstacle (d-f) ... 1,130 ft
5.23 CRUISE
The cruising altitude should be selected based on a consideration of trip length,
winds aloft, and the airplane’s performance. A typical cruising altitude and the ex-
pected wind enroute have been given for this sample problem. The cruise perform-
ance chart (Fig. 5-5) is entered at 6,000 ft altitude and 68°F above standard
temperature. The engine speed chosen is 4500 RPM, which results in the following:
•
Power ......................... 48%
•
True airspeed ............... 100 kts (115 mph)
•
Cruise fuel flow ........... 3.8 gal per hour
5.24 FUEL REQUIRED
The total fuel requirement for the flight may be estimated using the performance
information in Figure 5-4 and 5-5. For this sample problem, figure 5-4 shows that a
climb from 2,000 ft to 6,000 ft requires 1 gal of fuel. The corresponding distance
during the climb is 10 nautical miles. These values are for standard temperature and
are sufficiently accurate for most flight planning purposes.
However, a further correction for the effect of a non-standard temperature is to
increase the time, fuel, and distance by 10% for each 8°F above standard tempera-
ture, due to the lower rate of climb. In this case, assuming a temperature 61°F
above standard, the correction would be:
(61°F ÷ 46°F) x 10 = 20%
With this factor included the fuel estimate would be calculated as follows:
a) Fuel to climb (standard temperature) ....................... 1.2 gal
b) Increase due to non-standard temp. (1.2 gal x 20%) .......0.2 gal
c) Corrected fuel to climb (a + b) ............................ 1.4 gal
Using a similar procedure, the distance to climb results in 14 nautical miles. The re-
sultant cruising distance is:
d) total distance ...................... 400 nm
e) climb distance ...................... 15 nm
f) cruise distance (d - e) ............. 385 nm
