Aircraft Instruments & Basic Instrument Flying
Instrument interpretation, CDI reading, cross-check methods, and sole-reference flying
OBJECTIVE
Provide trainees with the knowledge and skills to interpret, cross-check, and utilize primary flight instruments in the T-38 Talon cockpit for sole-reference flying, with emphasis on reading and interpreting Course Deviation Indicators (CDI), effective instrument scan techniques, basic maneuvers, and recovery from unusual attitudes, to build a foundation for safe instrument operations under IFR conditions.
CONTENT
Standard Instrument Panel Overview
Understanding the layout and function of each primary flight instrument is the foundation of instrument flying. The "six-pack" arrangement is standard across most aircraft.
PRIMARY FLIGHT INSTRUMENTS (Six-Pack Layout)
ASI
Airspeed Indicator
Pitot-Static
ADI
Attitude Indicator
Gyroscopic
ALT
Altimeter
Pitot-Static
TC
Turn Coordinator
Gyroscopic
HSI
Heading/Situation
Gyroscopic + Nav
VSI
Vertical Speed
Pitot-Static
The ADI (Attitude Indicator) is your PRIMARY instrument - always return to it!
INSTRUMENT POWER SOURCES
Pitot-Static System
- • Airspeed Indicator (ASI)
- • Altimeter (ALT)
- • Vertical Speed Indicator (VSI)
Failure mode: Blocked pitot/static ports
Gyroscopic/Electrical
- • Attitude Indicator (ADI)
- • Heading Indicator (HSI)
- • Turn Coordinator (TC)
Failure mode: Electrical/vacuum failure
Reading the Course Deviation Indicator (CDI)
The CDI shows your position relative to a selected course (VOR radial, localizer, or GPS track). Understanding how to read and fly the CDI is essential for IFR navigation and approaches.
CDI COMPONENTS
Course Selector (OBS)
Rotates to select desired course/radial. The number at the top is your selected course.
Course Deviation Bar (Needle)
Vertical needle shows position relative to course. Centered = on course.
TO/FROM Flag
Indicates if the selected course will take you TO or FROM the station.
NAV Flag
Red flag = no valid signal. Remove flag = reliable navigation.
CDI NEEDLE INTERPRETATION
Needle Centered
You are ON the selected course. Maintain current heading.
Needle Left of Center
The course is to your LEFT. Turn LEFT to intercept.
Needle Right of Center
The course is to your RIGHT. Turn RIGHT to intercept.
CDI SENSITIVITY BY SOURCE
| Nav Source | Full-Scale Deflection | Each Dot |
|---|---|---|
| VOR | 10° off course | 2° per dot |
| Localizer (LOC) | 2.5° off course | 0.5° per dot (4x more sensitive!) |
| GPS (Enroute) | 2.0 NM off course | 0.4 NM per dot |
| GPS (Terminal) | 1.0 NM off course | 0.2 NM per dot |
| GPS (Approach) | 0.3 NM off course | ~350 ft per dot |
⚠️ Key Concept: "Fly TO the Needle"
The simple rule: Turn toward the needle to intercept the course. If the needle is left, turn left. If the needle is right, turn right. This works regardless of whether you're tracking TO or FROM the station.
TO/FROM FLAG LOGIC
TO Flag Displayed
Flying the selected course will take you TOWARD the station. You are on the side of the station where the reciprocal of your course would point.
FROM Flag Displayed
Flying the selected course will take you AWAY from the station. You have passed the station or are on the far side.
Warning: If TO/FROM flag shows the opposite of what you expect, you may have the wrong course set or be on the wrong side of the station. Cross-check your position!
Horizontal Situation Indicator (HSI)
The HSI combines heading and navigation information in one instrument, eliminating the need to mentally correlate a separate heading indicator with a CDI. Most modern aircraft and simulators use HSI displays.
HSI COMPONENTS
Compass Card
Rotating card shows current magnetic heading at the top lubber line.
Course Arrow
Points to selected course. The arrow head indicates the direction TO fly, tail indicates FROM.
Course Deviation Bar
Works same as CDI - lateral displacement from the course arrow center.
Heading Bug
Pilot-set reference for desired heading. Often coupled to autopilot.
Glideslope Indicator
Vertical needle on the side showing position relative to ILS glideslope.
HSI Advantage
The HSI shows course deviation relative to your heading pictorially. If the course line is to your left, the course IS to your left. No mental gymnastics required like with a basic VOR indicator.
Instrument Cross-Check Methods
An effective instrument scan is critical for maintaining aircraft control and situational awareness. There are several recognized scan patterns—the key is finding one that works and practicing until it's automatic.
THE THREE FUNDAMENTALS OF INSTRUMENT FLYING
1. CROSS-CHECK
Continuous observation of instruments for aircraft state
2. INTERPRET
Understanding what the instruments indicate
3. CONTROL
Making appropriate control inputs
SCAN METHODS
Selective Radial Scan (Recommended)
Start at the ADI (attitude), scan out to a supporting instrument, return to ADI, scan to another supporting instrument, return to ADI. The ADI is your "hub" - always return to it.
ADI → ASI → ADI → ALT → ADI → HSI → ADI → VSI → (repeat)
T-Scan Pattern
Scan across the top row (ASI-ADI-ALT), then down the center (ADI-HSI). Forms a "T" pattern.
ASI ↔ ADI ↔ ALT, then ADI ↓ HSI
Inverted-V Scan
Start at HSI, up to ADI, down to ALT, back to ADI, down to ASI. Good for approach work.
HSI → ADI → ALT → ADI → ASI
PRIMARY AND SUPPORTING INSTRUMENTS
For any maneuver, certain instruments are PRIMARY (direct indication) while others are SUPPORTING (confirm/trend).
| Maneuver | Primary: Pitch | Primary: Bank | Primary: Power |
|---|---|---|---|
| Straight & Level | Altimeter | Heading Ind. | Airspeed Ind. |
| Constant Speed Climb | Airspeed Ind. | Heading Ind. | RPM/N1 |
| Constant Rate Climb | VSI | Heading Ind. | Airspeed Ind. |
| Standard Rate Turn | Altimeter | Turn Coord. | Airspeed Ind. |
| Constant Speed Descent | Airspeed Ind. | Heading Ind. | RPM/N1 |
COMMON SCAN ERRORS
Fixation
Staring at one instrument too long, missing changes on others.
Omission
Skipping instruments in the scan, especially during high workload.
Emphasis
Spending too much time on less important instruments.
Chasing Needles
Making constant corrections instead of setting and monitoring.
Basic Instrument Maneuvers
Master these fundamental maneuvers before moving to more complex procedures like holding patterns and approaches.
STRAIGHT AND LEVEL FLIGHT
- • Pitch: Maintain constant altitude using ADI pitch attitude, verify with Altimeter
- • Bank: Wings level on ADI, verify with Heading Indicator (constant heading)
- • Power: Set for desired airspeed, verify with ASI
- • Trim: Reduce control pressures to zero - critical for scanning
CLIMBS AND DESCENTS
Constant Airspeed Climb/Descent
- • Pitch for airspeed (primary)
- • Power set for climb/descent
- • VSI shows resulting rate
Constant Rate Climb/Descent
- • Pitch for VSI (primary)
- • Power for airspeed
- • Common: 500 fpm, 1000 fpm
Level-Off: Lead altitude by 10% of VSI (e.g., 500 fpm = start level-off 50 ft before target)
STANDARD RATE TURNS
A standard rate turn is 3° per second, completing 360° in 2 minutes.
Bank Angle Formula
Bank = TAS ÷ 10 + 7
Example: 150 KTAS = 22° bank
Timed Turns
3° per second:
- • 90° turn = 30 seconds
- • 180° turn = 60 seconds
T-38 POWER SETTINGS REFERENCE
Climb
80-90%
Cruise
85-95%
Descent
50-70%
Approach
75-85%
Unusual Attitude Recoveries
An unusual attitude is any unintentional aircraft attitude outside normal flight parameters. Prompt recognition and correct recovery technique is essential.
RECOGNITION: HOW TO IDENTIFY THE ATTITUDE
Nose High Indications
- • ADI: Sky (blue) dominant
- • ASI: Decreasing
- • ALT: Increasing
- • VSI: Positive (climb)
Nose Low Indications
- • ADI: Ground (brown) dominant
- • ASI: Increasing
- • ALT: Decreasing
- • VSI: Negative (descent)
UNUSUAL ATTITUDE RECOVERY PROCEDURES
NOSE HIGH RECOVERY
- Add power (prevent stall)
- Lower nose to horizon
- Level wings
- Adjust power for desired flight
Priority: Prevent stall/departure
NOSE LOW RECOVERY
- Reduce power (reduce airspeed buildup)
- Level wings (FIRST!)
- Raise nose to horizon
- Add power for desired flight
Priority: Prevent overspeed/overstress
⚠️ Critical Principle
Nose Low: ALWAYS level wings BEFORE pulling up! Pulling back on the stick with bank applied tightens the spiral and can lead to structural overstress or accelerated stall. Roll wings level first, then raise the nose.
Trim and Control Technique
Proper trim technique is often overlooked but is essential for smooth instrument flight. A trimmed aircraft allows you to focus on scanning rather than fighting control pressures.
TRIM TECHNIQUE
Establish attitude - Set pitch and power for desired performance
Hold attitude - Maintain with control pressure
Trim off pressure - Small trim inputs until pressure is relieved
Verify performance - Aircraft should maintain attitude hands-off
Remember: Fly the attitude, then trim. Never trim to change attitude—use controls first, then trim to relieve pressure.
COMPLETION STANDARDS
Trainees will demonstrate proficiency in aircraft instruments and basic instrument flying through simulator exercises and oral explanations. Trainees must:
- • Identify all six primary flight instruments and their power sources
- • Correctly interpret CDI indications including needle position, TO/FROM, and sensitivity differences
- • Explain and demonstrate at least one instrument scan technique
- • Identify primary and supporting instruments for common maneuvers
- • Perform basic maneuvers in the simulator within tolerances (±100 ft altitude, ±10° heading, ±10 knots airspeed)
- • Correctly perform unusual attitude recoveries (nose high and nose low)
- • Demonstrate proper trim technique
Completion: Demonstrate understanding through simulator exercises and discussion