Unit Seven: Environmental Systems

STUDENT GUIDE T-39N/G NATOPS

UNIT SEVEN: ENVIRONMENTAL SYSTEMS

REFERENCE: T-39 NATOPS MANUAL

ENABLING OBJECTIVE:

A.1

Locate and operate T-39N/G aircraft systems, given a mission in a T-39 in accordance with

NATOPS.

ENABLING STEP:

A.1.8 Recall the basic description, related systems, and operating limitations of the T-39N/G

environmental systems.

NATOPS SEVEN: ENVIRONMENTAL SYSTEMS

A. Air conditioning (primary cooling system)

1. 9th stage bleed air duct is split into three branches, cooled, hot, and door press.

a. Cooled, through heat exchanger (cooled by ram air), then through expansion turbine.

b. Mixing valve controlled by rheostat or toggle (to regulate temp).

c. Anti-icing valve to prevent icing in water separator (keeps conditioned air above 0 C).

2. Bleed air shutoff valve on each engine stops airflow if leak is suspected (CABIN AIR

SELECT switch)

3. Either engine can provide full system capability.

4. Aux air conditioner - main purpose is ground cooling and augments primary system.

a. MODE switch - air conditioner or circulation.

b. FWD EVAP/AFT EVAP - cockpit/cabin evaporators.

c. Should be OFF by 10K; shall be secured at FL 180 (due to compressor motor arcing).

d. Powered by Mission bus B (lost if single gen).

e. Uses Freon, NOT bleed air.

1. Cabin pressure regulator controls pressurization.

a. Pressure regulator inop from SL to 8000 MSL (unpressurized).

b. Regulator maintains 8000' cabin altitude above the 8000' pressure altitude to a

maximum of 8.8 cabin pressure differential.

ENVIRONMENTAL SYSTEMS

7-1