Basic Attitude Instrument Flying

Basic Attitude Instrument Flying

The two basic methods used for learning attitude instrument flying are ‘control and performance’ and ‘primary and supporting’.

Cross Checking
The first fundamental skill is cross-checking (also called ‘scanning’ or ‘instrument coverage’). In instrument flying, the pilot maintains an attitude by reference to instruments, producing the desired result in performance.

Cross-checking is mandatory in instrument flying. In visual flight, a level attitude can be maintained by outside references. However, even the altimeter must be checked to determine if altitude is being maintained. Due to human error, instrument error, and airplane performance differences in various atmospheric conditions, it is impossible to establish an attitude and have performance remain constant for a long period of time.

Examples of cross-checking: Selected Radial Cross-Check – when the selected radial cross-check is used, a pilot spends 80% - 90% of flight time looking at the attitude indicator, taking only quick glances at the other flight instruments. With this method, the pilot’s eyes never travel directly between the flights instruments but move by way of the attitude indicator.
Inverted-V Cross-Check – In the inverted-V cross-check, the pilot scans from the attitude indicator down to the turn-coordinator, up to the attitude indicator, down to the VSI, and back up to the attitude indicator
Rectangular Cross-Check – In the rectangular cross-check, the pilot scans across the top three instruments, and then drops down to scan the bottom three instruments. This scan follows a rectangular path. This cross-checking method gives equal weight to the information from each instrument, regardless of its importance in the manuever being performed.

Common Cross-Check Errors:

• A beginner might cross-check rapidly, looking at instruments without knowing exactly what to look for
• Fixation - Staring at a single instrument, usually occurs for a reason, but has poor results. For example asking to do a 500fpm climb will fixate you on the VSI and the aircrafts speed may be dropping too much.
• Omission – Failure to anticipate significant instrument indicators following attitude changes. For example, in a roll-out from 180 degrees steep turn, straight and level flight is established with reference only to the attitude indicator, and the pilot neglects to check the heading indicator for constant heading information.
• Emphasis on a single instrument – Reliance on a single instrument is poor technique as it may provide inadequate information or errors.

Control and Performance
Aircraft performance is achieved by controlling the aircraft attitude and power. Aircrafts attitude is the relationship of both the aircrafts pitch and roll axes in relation to the Earths horizon. An aircraft is flown in instrument flight by controlling the attitude and power, as necessary, to produce both controlled and stabilized flight without reference to a visible horizon.

Control Instruments The control instruments display immediate attitude and power indications and are calibrated to permit those respective adjustments in precise increments. Control is determined by reference to the attitude and power indicators. Power indicators vary with aircraft and may include manifold pressure, tachometers, flue flow etc.
Performance Instruments The performance instruments indicate the aircrafts actual performance. Performance is determined by reference to the altimeter, airspeed or VSI.

Navigation Instruments
The navigation instruments indicate the position of the aircraft in relation to a selected navigation facility or fix. This group of instruments includes various types of course indicators, range indicators, glideslope indicators, and bearing pointers.

Procedural Steps in Using Control and Performance

1. Establish an attitude and power setting on the control instruments that result in the desired performance. Known or computed attitude changes and approximated power settings helps to reduce the pilot’s workload.
2. Trim until control pressures are neutralized. Trimming for hands-off flight is essential for smooth, precise aircraft control. It allows a pilot to attend to other flight deck duties with minimum deviation from the desired attitude.
3. Cross-check performance instrument to determine if the established attitude or power setting is provided to the desired performance. The cross-check involves both seeing and interpreting.
4. Adjust the attitude and/or power setting on the control instruments as necessary.

Primary and Supporting
All manoeuvres involve some degree of motion about the lateral (pitch), longitudinal (bank/roll), and vertical (yaw) axes. Instruments are grouped as they related to control function and aircraft performance as pitch, control, bank control, power control, and trim.

Pitch Control

Pitch control is controlling the rotation of the aircraft about the lateral axis by movement of the elevator. After interpreting the pitch attitude from the proper flight instrument, exert control pressures to affect the desired pitch attitude with reference to the horizon.

These instruments include the:

• Attitude Indicator – Gives direct and immediate indication of the pitch attitude of the aircraft. It is the only instrument that portrays both instantly and directly the actual flight attitude and is the basic attitude reference.
• Altimeter – If the altimeter indicates a loss of altitude, the pitch must be adjusted upward to stop the descent and vice versa. The altimeter can also indicate pitch attitude in a climb or descent by how rapidly the needles move.
• VSI – If the needle moves above zero, the pitch attitude must be adjusted downward to stop the changes in the indications of the VSI can prevent any significant change in altitude.
• Airspeed Indicator – The ASI gives an indirect reading of the pitch attitude. A repaid change in airspeed indicates a large change in pitch

Power Control
During or immediately after adjusting the power control(s), the power instruments should be cross-checked to see if the power adjustment is as desired. Whether or not the need for a power adjustment is indicated by another instrument(s), adjustment is made by cross-checking the power instruments.

Power indicator instruments are:

• Airspeed Indicator
• Engine Instruments: Tachometer, Manifold pressure

Bank Control

When flying in instrument metrological conditions, pilots maintain pre planned or assigned headings. With this in mind, the primary instrument for bank angle is the heading indicator. The heading indicator is the only reliable instrument, providing it is aligned with the magnetic compass to display the magnetic heading.

Trim
Trim control uses either the rudder or elevator trim to help control the aircraft around the lateral and vertical axis.

The Attitude Indicator is the only instrument that gives you both Pitch & Bank

Errors:

• Over controlling
• Improper usage of power
• Fail to cross check and take action