Accurate Display Indication Requirements

T-34C AIRCRAFT SYSTEMS FAMILIARIZATION

CHAPTER FIFTEEN

WORKBOOK

AOA Probe

The AOA probe is located on the leading edge of the left wing. A rotary vane is attached to a

potentiometer located within the probe body. The vane is positioned by the relative wind

striking the leading edge of the wing. The potentiometer sends an electrical signal representative

of the AOA to the AOA electronic control unit.

AOA Electronic Control Unit

The AOA electronic control unit is a white rectangular box located in the aft cockpit on the deck,

right side. It is a solid-state electronic unit amplifying the AOA probe signal and sending it to

the AOA indicator pointer and indexer for display.

Accurate Display Indication Requirements

To display valid AOA information the aircraft must be airborne and in the proper wing flap

configuration; i.e., flaps full up (0%) or flaps full down (100%).

AOA Indicator

The AOA indicator is located in the upper left corner of the instrument panel in each cockpit. It

displays accurate AOA information in the form of arbitrary units. The indicator aids a pilot in

establishing the optimum aircraft wing AOA for a given airspeed. The display is comprised of a

pointer and a scale. The scale is graduated from 0-29 units in one-unit increments. Three special

indexes are marked on the scale at 20 units, 26 units, and 29 units. The 20-unit index is the

optimum approach index. This is the most important, since it is used in the early stage of the

AOA landing approach to establish the aircraft on the correct airspeed at 20 units. In the T-34C

this will be approximately 80 KIAS with flaps down and 95 KIAS with flaps up. The 26 unit

index is the stall warning index. The rudder pedal shakers, a physical stall warning feature, are

activated only in flight at or above 26 units. Activation indicates the aircraft is 5-10 KIAS

above actual stall speed. On landing, the rudder pedal shakers are disabled by a safety switch

located on the nose landing gear. At 29.0 units, the aircraft is fully stalled. Should the pointer

move into the red OFF portion of the dial, it indicates the system has lost 28-VDC power. The

pointer is operated by an electrical signal that is developed in the AOA probe.

ANGLE-OF-ATTACK SYSTEM

15-3