i. Deceleration Check.
Ground check the fuel con-
trol system and associated linkage by performing a
deceleration check. This check is applicable only when
using alternate fuels and must be performed before the
engine has had time to cool down.
N O T
JP-5 fuel is designated as the Army alternate fuel
to be used in the T63-A-720. No deceleration time
restrictions are imposed on the engine when the
Army primary fuel (JP-4) is used.
N O T
Perform each step in the sequence listed. Recheck
the deceleration rate after each step to determine
if there is a need for further correction. Replace
the fuel control if the deceleration rate is still
unsatisfactory after all steps have been com-
(1) Turn the generator switch off.
(2) Rotate the twist grip to full open, hold col-
lective at flat pitch and stabilize N2 at exactly 100%
(trim as required) for approximately 15 seconds.
Stop the time as the N1 needle passes through 65%.
The minimum allowable time is two seconds.
N O T
Practice and/or retakes may be required before
proficiency is obtained in timing the deceleration.
(4) If deceleration time is less than the time
allowed make two more checks to confirm the time. If
the confirmed deceleration time is less than the allowa-
ble minimum perform a rigging check. (Refer to para-
(5) Repeat the deceleration check. If the
deceleration time is leas than the allowable minimum
perform an idle speed check. (Refer to paragraph
(6) Repeat the deceleration check. If decelera-
tion time is less than the allowable minimum, replace
the fuel control.
j. Cleaning Gas Producer Fuel Control Fuel Filter.
Remove, clean and reinstall the fuel control fuel filter
assembly as follows. (See figure 5-8.).
(1) Thoroughly clean exterior of fuel control in
the area of the plug to prevent contaminants from
getting into the port after it is opened.
(2) Remove lockwire and remove plug (l),
spring (3), and filter assembly (4). Discard preformed
(3) Remove retaining clip (7), spring pin (6),
and separate washer (10), spring (9), and strainer (8)
During rapid throttle movements, make
appropriate anti-torque pedal correc-
tions to prevent aircraft from turning on
loose or slick surfaces.
(3) Snap the twist grip to the IDLE position.
Simultaneously start a time count using a stop watch.
from filter assembly (4).
Figure 5-8. Fuel Control Fuel Filter