TM 1-1520-238-T-4
6–166
6–83.
PILOT LOW RPM ROTOR INDICATOR – DOES NOT LIGHT AT 93% OR LESS
6–83
Tools:
Nomenclature
Part Number
Tool Kit, Electrical
SC518099CLA06
Repairer’s
Multimeter, Digital
AN/PSM-45
Personnel Required:
68F
Aircraft Electrician
References:
TM 1-1520-238-T-6
TM 1-1520-238-23
Equipment Conditions:
Ref
Condition
TM 1-1520-238-23
Access provisions –
L140 fairing and
L325, T250L, T250R,
T290L, T290R and
T325 access doors
open
WARNING
Turn off power before detaching or
attaching wires and connectors. High
current 28 VDC or 115 VAC is present.
Failure to do so could result in death or
serious injury.
1. Check for audio in headset.
Is low RPM audio warning present?
YES
Go to step 3.
NO
Go to step 2.
2. Check for open between:
P755–22 and P49–9,
P755–23 and P49–10.
Does open exist?
YES
Repair open wire. Go to
paragraph 6–81.
NO
Go to step 4.
3. Detach P49–18. Short P49–18 to ground.
Does indicator light?
YES
Replace engine out warning unit
(TM 1-1520-238-23).
NO
Go to step 5.
4. Check for 6 to 8 VAC between P49–9 and
P49–10.
Is voltage present?
YES
Replace engine out warning unit
(TM 1-1520-238-23).
NO
Replace rotor speed sensor A25
and isolation transformer T1
(TM 1-1520-238-23).
5. Check for open between P49–18 and P20–x.
Does open exist?
YES
Repair open wire. Go to
paragraph 6–81.
NO
Refer to TM 1-1520-238-T-6 to
troubleshoot the pilot
caution/warning system.
END OF TASK
