STUDENT GUIDE T-39N/G NATOPS
UNIT THREE: ELECTRICAL SYSTEM
REFERENCE: T-39 NATOPS MANUAL
A-1 Locate and operate T-39N/G aircraft systems, given a mission in a T-39 in accordance with
A.1.4 Recall the basic description, related systems, and operating limitations of the T-39N/G
NATOPS THREE: ELECTRICAL SYSTEM
A. DC Power sources
1. Two external power receptacles located under left engine inlet.
a. Oval utility outlet powers all buses except starter bus. Used for ground maintenance.
28 VDC, 300 amps.
b. Rectangular starter outlet. 28 VDC, 800 amps minimum required. Powers starter bus
only. (Batteries disconnected from start bus but still powers DC Essential bus.)
2. Batteries (5 batteries total in T-39)
a. - Two 26 volt, 40 amp hr, normally in parallel (in series for battery start).
- Temp gauges - amber at 120°F, red at 150°F (BATT HOT master caution)
- Approx 45 minutes of power avail in the event of dual gen failure. (Battery power only.
Secure hydraulic pump in T-39G model and use only if necessary.)
Two 7.2 volt batteries, each powers half of the emergency lights (30 minutes).
One Emergency standby attitude gyro battery (4 hours).
3. DC Generators
Two 28 volt, 400 amp engine-driven starter-generators. (Normal v = 27.5 - 29.5)
Powers the paralleling bus directly.
Act as starters during engine start (31-35%)
ELECTRICAL SYSTEM 3-1