Radio Magnetic Indicator - P-340

T-34C INSTRUMENTS

CHAPTER ONE

Radio Magnetic Indicator

The Radio Magnetic Indicator (RMI) (Figure 16) is a system containing a north

seeking element stabilized by a gyro wheel. It incorporates the features of a magnetic

compass in that it indicates the magnetic heading of the aircraft. However, the erratic

nature of the magnetic compass is overcome by the stabilization of the gyro.

Contrary to the operation of the other instruments on the panel, the RMI rotates about

its center and the pointers remain fixed. The face, or "compass card," is calibrated in

degrees. The instrument may be used as a directional gyro when the magnetic

influence is cut out of the system. Alternating current (AC) is required for the

operation of the RMI. A complete description of this system can be found in

NATOPS.

Use and Limitations. The RMI is the wing attitude crosscheck instrument for both

straight and level and straight climbs or descents. For level turns and climbing or

descending turns, the RMI is used as a performance instrument. It will give you an

indirect indication of wing attitude with the balance ball centered. With the balanced

ball out of trim, heading will drift, resulting in the RMI no longer acting as either a

wing crosscheck or performance instrument. In attitude instrument flight, it is

essential that our instruments portray an accurate indication of the aircraft's attitude.

It is imperative the balance ball is centered so that the RMI can provide us with

accurate attitude information.

Figure 16 Radio Magnetic Indicator

INTRODUCTION TO BASIC INSTRUMENTS 1-9