TM 55-2840-241-23
g. Engine Starting Characteristics
Adjustments. (Refer to fig. 5-6.1).
There are two fuel control adjustments
which can be used to change the start-
ing characteristics of the engine.
These adjustments are a starting derich-
ment adjustment in addition to a start
acceleration adjustment, which is on
some engines. The conditions, which can
be improved by these adjustments, are
indicated in Table 5-1.
(1) Start-Derichment Adjustment. (Refer to fig.
5-6.1). The start-derichment (derich) adjustment
can be used to correct lean (slow) start or rich (hot)
start conditions. This adjustment is effective
below 33% Nl speed. For slow starts at Nl speeds
between 35% and 55% Nl speed, refer to Start/Ac-
celeration Fuel Flow Adjustment, subparagraph
(2). (Refer to table 5-l).
NOTE
The start derichment adjustment on the latest modified
fuel control has a wider angular range than earlier models
(200° in Place of 100°). Neutral position for the latest con-
trol is 7 dots/70O from the counterclockwise stop. Neu-
tral on controls prior to this is a 4 dots/40°
counterclockwise. The effective start derichment speed
range is between 20% and 33% N1. Also, turning the ad-
justment to the clockwise stop closes the Py vent which
deactivates the start derichment.
NOTE
To accurately determine the proper adjustment, condi-
tions under which the adjustments are made should be
consistent, i.e., a fully charged aircraft battery, the same
residual TOT and the same lightoff speed.
(a) For low temperature with slow starts at 20-33% N1
speed, adjust the start-derichment as follows:
1 Remove lockwire securing adjustment locknut to Pc
filter-fitting.
Do not disturb the pointer-to-shaft sealed wire
at any time. This is an overhaul function only.
2 Loosen the adjustment locknut.
Figure 5-6.1. Start/Acceleration and Start
Derichment Adjustments.
During attempted start, TOT must be closely
monitored to prevent overtemperature opera-
tion. Record overtemperature in the Engine
Log.
3 Make adjustment using an Allen wrench.
Turn clockwise to enrich the starting fuel flow to
improve stagnated starts, cold weather starts, or
high altitude ground starts. Make adjustment in
10° maximum increments (dots are
10° apart) and
tighten locknut to 20-25 lb in. (2.3-2.8 Nm) after
each setting. Check the starting peak TOT after
each setting until satisfactory starts are made.
4 When desired adjustment is obtained, secure lockout
to Pc filter-fitting with lockwire.
Monitor TOT closely after start-derichment ad-
justment to be sure overtemperature limits are
not exceeded.
5-10.2 Change 11
