Altitude and Airspeed Corrections

T-34C INSTRUMENTS

CHAPTER THREE

or gain in altitude. It is important in maintaining straight and level flight based on airspeed to set

the correct level flight attitude and support it with the proper scan pattern. For instrument flight,

the attitude gyro is the basic attitude indicator for nose and wing position. The nose position is

crosschecked with the altimeter and vertical speed indicator, and the wing position is

crosschecked with the RMI. The airspeed indicator is the performance instrument. The attitude

gyro should be adjusted so that the miniature airplane is superimposed on the horizon bar (for

normal cruise only). Since the greatest percentage of flight time is straight and level flying, the

correction techniques discussed here are extremely important. All attitude adjustments to correct

for errors noted on the attitude crosscheck instruments should be made on the attitude gyro.

Whenever an error in either heading or altitude is noted, first stop the error and stabilize, then

correct back to proper heading or altitude.

A correction to return to a desired heading should be made by establishing an AOB on

the attitude gyro and maintaining it until approaching the particular heading desired. As

a rule of thumb, the AOB used for heading correction should not exceed the number of

degrees you want to turn. Lead the rollout heading by the "onethird rule," i.e., by the

number of degrees equal to onethird the AOB. This lead in rollout will preclude turning

beyond the desired heading.

Corrections for small deviations from the desired altitude (1000 feet or less) should be

made by displacing the nose attitude from the level flight position on the attitude gyro

and maintaining it until approaching the correct altitude. Adjust power as necessary to

maintain 150 KIAS throughout your correction. The lead necessary to level off without

going beyond the desired altitude will depend upon the rate of change in altitude.

Adjustments for heading and altitude should be made as soon as the error is noted so that large

corrections will not be necessary. Corrections for large deviations from desired altitude (over

1000 feet): use 120 KIAS normal climb procedures if low, use 150 KIAS normal descent if

high. If an error is noted and the aviator immediately tries to correct back, prior to settling down,

the tendency is always to overcorrect.

In order to maintain level flight, the pilot must first establish the nose in the level flight position

on the gyro, trim to that attitude, and then crosscheck the altimeter and VSI to detect if the

aircraft's nose is indeed level (VSI indicating zero) at desired altitude (altimeter). Obviously,

both instruments must be used together. For example, when a rate of descent is noted on the

VSI, the altimeter is immediately checked to determine if the descent is undesirable (altimeter on

altitude or below) or beneficial (above altitude, and thus the VSI shows you to be correcting).

The vertical speed indicator is the best and most precise crosscheck instrument in level flight if

used properly. Used improperly, when its lagging factor is not taken into consideration, it can

lead to extremely erratic nose control as the pilot chases the VSI.

Altitude and Airspeed Corrections. There are several methods for correcting for a

deviation from desired altitude and airspeed or both. These consist of a power correction or a

power and attitude correction plus the need for retrimming.

BASIC INSTRUMENTS FLIGHT PROCEDURES 3-3