APPROVED FUELS
The “Limitations” section of the approved
AFM lists specific manufacturer’s fuels ap-
proved for use.
FUEL DENSITY ADJUSTMENTS
If optimum engine acceleration is desired, the
density adjustment knob on the front of the fuel
control unit should be readjusted to the fuel den-
sity setting for the fuel type being used. Refer
to the AFM for recommended fuel control adjust-
ment knob positions (density setting).
Engine stall margin may be reduced
during high-altitude operation if the
fuel control density adjustment knob
is positioned to a lower density set-
ting than that recommended for type
of fuel being used.
Either of two types of fuel density adjustment
knobs may be installed. They are designated
Type A and Type B (Figure 5-10). To make an
adjustment, push the knob in, rotate the knob
to the density setting desired, and release pres-
sure. If necessary, jiggle the knob until it locks.
The adjustment knob must be seated in its po-
sitioning detent for satisfactory operation.
AVIATION GASOLINE
Aviation gasoline may be used as an emer-
gency fuel and mixed, in any proportion, with
the various approved kerosene-base fuels.
Aviation gasoline may not be used in excess
of 25 hours between engine overhauls.
When using any aviation gasoline
in the fuel mixture, operation is lim-
ited as follows:
• Do not take off with fuel temperature
lower than –54ºC (–65ºF).
• Restrict airplane flights to below 15,000
feet.
• Both jet pumps and both wing standby
pump switches must be on and the pumps
must be operating.
NOTE
Certain aviation gas and jet fuel mix-
ture ratios can produce greater flam-
mability hazards under partially
filled aircraft tank or storage tank
conditions encountered during re-
fueling or mixing. Follow estab-
lished safety standards to eliminate
any possible sparks.
CAUTION
CAUTION
5-16
FOR TRAINING PURPOSES ONLY
LEARJET 20 SERIES PILOT TRAINING MANUAL
FlightSafety
international
Figure 5-10.
Fuel Density Adjustment
7
5
7
2
6
9
8
6
81
3
7
8
FU
EL ADJUS
T—
P
U
S
H
&
T
U
R
N
JP
-5
&
6
J
P
-4
P
U
S
H
T
U
R
N
NO
MINAL
D
E
C
IN
C
–1
+1
+
2
+
3
+
4
–6
–5
–
4
–
3
–
2
INDEX
PIN
INDEX
PIN
TYPE B
TYPE A
TYPE A
POSITION
TYPE B
POSITION
DENSITY
SETTING
8 6
7 8
7 5
7 2
6 9
81 3
JP5 & JP6
JP4
86
87
–5
–4
–3
–2
–1
+1
84
81
78
75
72
69
813
78
75
72
69
INCREASE
DECREASE
NOMINAL
