SECTION
5
PERFORMANCE
Fuel
to
Descend
Di
stance to
Descend
=Cruise fuel to descend - Airport fuel to
descend
=
57
pounds
-
10
pounds
=
47
Pounds
= Cruise distance to
descend
- Airport
distance to descend.
=
60
nautical miles -
11
nautical miles
=
49
nautical miles
Adjusted for
wind
(use
40%
of the
wind
at
altitude
for descent wind),
=
49
±
wind
contribution
=
49
+ [ 15.5 minutes
(4
15
k
t)J
60
mlnutes . x
no
s
=
49
nautical miles + 1.55 nautical miles
=
51
nautical miles
Cruise
Performance
With
Recommended
Lean
Mixture
(Figure
5-20)
Maximum
recommended
cruise
can
be
obtained with
2450
RPM
and
29.5
Inches
Hg.
manifold pressure.
The
approximation
method
for extracting data
from
the cruise tables
is
to
select
the next
lower
temperature
and
altitude
values,
which
are gen-
erally
conservative with respect to fuel
economy.
(
I)
(
2)
(3)
Enter the 5000-foot data
at
2450
RPM
and
29.5 Inches
H9.
mani-
fold pressure.
Use
-15
0
C
(5
0
F)
data for a
power
of
76.5%.
airspeed
of
182
KTAS
and
a total fuel flow
of
229
pounds
per
hour.
Correcting for a weight
of
6200
pounds,
the airspeed increases
to:
182
KTAS
+
(6850
pounds
-
6200
pounds)
(5
KTAS)
1000
pounds
182
KTAS
+ 3.3
KTAS
=
185
KTAS
Using
the interpolation
method,
interpolating
altitude,
temperature
and
weight, the actual
performance
is
71.1%
power,
192
KTAS
and
total fuel flow
of
214
pounds
per hour.
In
the
above
calculations,
for convenience, the weight
was
assumed
to
be
equal
to the takeoff weight
of
6200
pounds.
More
realistic
data
can
be
determined
if
the average cruise weight
is
used. This average cruise
weight
is
determined as follows:
0-10
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