5.2 Pitch, Bank & Power Instrument Interpretation

Pitch, Bank & Power Instrument Interpretation

Quick Answer: The FAA recognizes two primary concepts for attitude instrument interpretation: the Primary and Supporting Method and the Control and Performance Method. In the Primary and Supporting method, instruments are categorized by flight axis (Pitch, Bank, Power) where the Primary instrument provides the most direct and pertinent information for a specific maneuver (e.g., Altimeter for straight-and-level pitch, Heading Indicator for straight-and-level bank). In the Control and Performance method, Control instruments (Attitude Indicator + Tachometer/Manifold Pressure) are set to known values to produce desired results on Performance instruments (Airspeed, Altimeter, VSI, Heading). Trimming always follows the rule: Pitch, Power, Trim.

To control an aircraft solely by reference to instruments, a pilot must interpret how changes in aircraft pitch, bank, and power influence total aerodynamic performance. The Federal Aviation Administration outlines two distinct, highly effective methods of teaching and practicing attitude instrument flying: the Primary and Supporting Method and the Control and Performance Method.

---

The Primary and Supporting Method

The Primary and Supporting method groups flight instruments into three distinct functional categories: Pitch Instruments, Bank Instruments, and Power Instruments.

For every specific flight maneuver (straight-and-level, constant-airspeed climb, constant-rate descent, standard-rate turn), one instrument in each category is designated as Primary (providing the most direct and essential indication for maintaining the desired condition), while the remaining instruments serve as Supporting references.

+-----------------------------------------------------------------------+
|                   INSTRUMENT CLASSIFICATION GROUPS                    |
|                                                                       |
|   +-----------------------+---------------------+-----------------+   |
|   |   PITCH INSTRUMENTS   |  BANK INSTRUMENTS   | POWER INSTRUMENT|   |
|   +-----------------------+---------------------+-----------------+   |
|   | • Attitude Indicator  | • Attitude Indicator| • Manifold Press|   |
|   | • Altimeter           | • Heading Indicator | • Tachometer/RPM|   |
|   | • Airspeed Indicator  | • Turn Coordinator  | • Airspeed Ind. |   |
|   | • Vert Speed Ind(VSI) |                     |                 |   |
|   +-----------------------+---------------------+-----------------+   |
+-----------------------------------------------------------------------+

1. Pitch Instruments

Pitch instruments reflect the angular relationship of the aircraft's longitudinal axis relative to the Earth's horizon:

• Attitude Indicator: Provides direct, instantaneous pitch attitude information. However, because pitch attitude varies with airspeed, aircraft weight, and configuration, it is considered a supporting/transitional instrument in stabilized straight-and-level flight.
• Altimeter: The Primary pitch instrument for straight-and-level flight. If altitude is constant, pitch is correct for that airspeed and power setting.
• Airspeed Indicator: The Primary pitch instrument in a constant-power, constant-airspeed climb or descent (e.g., climbing at $V_y$). Pitch directly regulates airspeed when power is fixed.
• Vertical Speed Indicator (VSI): The Primary pitch instrument in a constant-rate climb or descent (e.g., maintaining a 500 FPM descent on a non-precision approach).

2. Bank Instruments

Bank instruments reflect the angular relationship of the aircraft's lateral axis relative to the horizon:

• Attitude Indicator: Provides instantaneous bank angle display. Used as the primary transition reference when entering or rolling out of turns.
• Heading Indicator: The Primary bank instrument for straight-and-level flight. If the heading indicator is motionless on the assigned heading, the wings are level.
• Turn Coordinator: The Primary bank instrument during a standard-rate turn. The miniature aircraft indicates the precise rate of turn (3°/sec), while the inclinometer (ball) indicates coordination.

3. Power Instruments

Power instruments indicate engine output and aerodynamic energy:

• Manifold Pressure Gauge / Tachometer (RPM): Primary power instruments during power adjustments and transitions (establishing climb, cruise, or descent power settings).
• Airspeed Indicator: The Primary power instrument in straight-and-level flight at a constant altitude, as well as in constant-rate climbs and descents. Once altitude is locked on the altimeter, airspeed directly reflects engine power output.

---

Master Matrix of Primary and Supporting Instruments

The following matrix summarizes the primary and supporting instruments across the core IFR flight regimes:

---

The Control and Performance Method

While the Primary and Supporting method is favored for initial instrument instruction and system malfunction analysis, the Control and Performance Method is widely utilized in advanced flight training, turboprop, and jet transport operations.

This method operates on a simple, universal formula: $\text{Attitude} + \text{Power} = \text{Performance}$

+-----------------------------------------------------------------------+
|                 CONTROL AND PERFORMANCE ARCHITECTURE                  |
|                                                                       |
|   +-----------------------+       +-------------------------------+   |
|   |  CONTROL INSTRUMENTS  |       |    PERFORMANCE INSTRUMENTS    |   |
|   +-----------------------+       +-------------------------------+   |
|   | • Attitude Indicator  | +==>  | • Airspeed Indicator          |   |
|   | • Tachometer / MAP    |       | • Altimeter & VSI             |   |
|   | (Direct Pilot Inputs) |       | • Heading & Turn Coordinator  |   |
|   +-----------------------+       +-------------------------------+   |
+-----------------------------------------------------------------------+

1. Control Instruments

Control instruments display immediate attitude and power changes. The pilot directly manipulates flight controls and throttle to set precise values on these instruments:

• Attitude Indicator: Shows immediate changes in pitch attitude and bank angle.
• Power Indicators: Tachometer (RPM), Manifold Pressure (MAP), Engine Pressure Ratio (EPR), or Torque.

2. Performance Instruments

Performance instruments indicate the aircraft's actual flight path, speed, and altitude response resulting from the control inputs:

• Airspeed Indicator, Altimeter, Vertical Speed Indicator, Heading Indicator, Turn Coordinator, and Angle of Attack (AoA) indicator.

3. Navigation Instruments

Navigation instruments indicate aircraft position relative to ground facilities or space-based waypoints (VOR, Localizer, Glideslope, GPS CDI).

Operational Procedure for Control & Performance:

1. Establish: Set known pitch and power settings on the Control instruments (e.g., 2.5° nose up, 2,300 RPM).
2. Trim: Trim away all control yoke pressures.
3. Cross-Check: Observe the Performance instruments to determine if the desired performance (e.g., 110 knots at 4,000 feet) is achieved.
4. Adjust: If performance deviates, make a calculated adjustment on the Control instruments and re-trim.

---

Proper Trim Technique ("Pitch, Power, Trim")

A fundamental law of instrument flying is that an untrimmed aircraft cannot be flown smoothly on instruments.

+-----------------------------------------------------------------------+
|                      THE GOLDEN WORKFLOW FORMULA                      |
|                                                                       |
|    [ 1. PITCH ]   =====>  Establish desired pitch attitude on AI      |
|    [ 2. POWER ]   =====>  Set required throttle / RPM / MAP           |
|    [ 3. TRIM  ]   =====>  Relieve control pressures HANDS-OFF         |
+-----------------------------------------------------------------------+

The Common Trimming Trap

A common student error is attempting to use the trim wheel as a flight control to drive the nose up or down. Trimming before establishing the pitch attitude induces severe overcontrolling, pitch oscillations, and airspeed instability. Always:

1. Fly the aircraft first: Use manual elevator pressure to place the miniature aircraft exactly on the target pitch attitude.
2. Set power: Adjust engine power to the known power setting.
3. Relieve pressure: Roll the trim wheel until all back or forward yoke pressure disappears completely.

Standard Rate Turns & Aerodynamic Calculations

A Standard Rate Turn (also known as a Rate One Turn) is defined by the FAA as a turn completed at a rate of $3^\circ$ per second. At standard rate:

• A $90^\circ$ heading change requires 30 seconds.
• A $180^\circ$ standard turn requires 60 seconds (1 minute).
• A full $360^\circ$ circle requires 120 seconds (2 minutes).

Note on High Speeds: In high-speed commercial jets operating above 250 KTAS, standard rate turns require excessive bank angles. High-speed aircraft typically fly a half-standard rate turn ($1.5^\circ$ per second) or cap bank angle at $25^\circ$ to $30^\circ$.

---

Calculating the Required Bank Angle for a Standard Rate Turn

As True Airspeed (TAS) increases, the centrifugal force in a turn increases. Therefore, to maintain a constant $3^\circ$/second rate of turn at higher airspeeds, the aircraft must fly at a steeper bank angle.

Pilots use two standardized mental math rules of thumb to calculate the required bank angle:

$\text{Bank Angle} = \left( \frac{\text{TAS}}{10} \right) + 7$

$\text{Alternative Formula:} \quad \text{Bank Angle} \approx 15\% \text{ of TAS} \quad \text{or} \quad \left( \frac{\text{TAS}}{10} \times 1.5 \right)$

Standard Rate Rollout Lead Point Rule

When rolling out of a coordinated turn onto an assigned heading, inertia and roll rate require leading the rollout. The standard rule of thumb is:

$\text{Lead Point (Degrees)} = \frac{\text{Bank Angle}}{2}$

Example: If turning in a $20^\circ$ bank toward a heading of $090^\circ$, initiate the rollout $10^\circ$ prior ($20 / 2 = 10^\circ$) at heading $080^\circ$ (for a right turn) or heading $100^\circ$ (for a left turn).