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IFH · IFH Chapter 4

Instrument Cross-Check (Scan) Patterns

Master the IFR cross-check: selected radial, inverted-V, and rectangular scan patterns, plus the three classic scan errors every instrument pilot must avoid.

CFI's Whiteboard Explanation

Think of the scan as your eyes' job in IMC: never let them stop. Most pilots use a selected radial scan — eyes always return to the attitude indicator between quick peeks at airspeed, altimeter, heading, and VSI. The AI tells you what the airplane is doing; the other instruments tell you whether it's working.

Watch out for the three killers:

  • Fixation — staring at one gauge
  • Omission — skipping an instrument entirely
  • Emphasis — trusting one instrument too much

Trim the airplane. An out-of-trim plane wrecks your scan because you're flying with your hands instead of your eyes.

Handbook Reference
IFH Ch 4

4.scan-patterns. Instrument Cross-Check (Scan) Patterns

Instrument cross-check, also called the scan, is the continuous and logical observation of the flight instruments for attitude and performance information. In attitude instrument flying, the pilot must learn to systematically interpret the instruments rather than fixate on any single one. The Instrument Flying Handbook (FAA-H-8083-15B), Chapter 4, identifies several recognized scan patterns and the most common errors that degrade them.

Purpose of the Scan

No single flight instrument provides all the information needed to control the aircraft. Aircraft attitude is established by reference to the attitude indicator, while aircraft performance is verified on the pitot-static instruments (airspeed, altimeter, VSI), the heading indicator, and the turn coordinator. The scan ties these together so the pilot can detect deviation from the desired flight condition and correct it promptly.

Common Scan Patterns

The IFH discusses three primary techniques. None is mandatory; each pilot adapts a pattern that fits the maneuver, the cockpit layout, and personal preference.

  • Selected Radial Cross-Check. The pilot's eyes return to the attitude indicator after looking at each of the other instruments — AI to airspeed, back to AI; AI to altimeter, back to AI; AI to heading indicator, back to AI; and so on. About 80–90% of scan time is spent on the attitude indicator, with brief glances at the supporting instruments. This pattern works well for pilots whose primary attitude reference is the AI and is the most widely taught for basic attitude instrument flying.
  • Inverted-V Cross-Check. The pilot scans from the attitude indicator down to the turn coordinator, back up to the AI, down to the VSI, and back to the AI, tracing an inverted V. This emphasizes bank and pitch trend information.
  • Rectangular Cross-Check. The eyes move across the top row of instruments (airspeed, AI, altimeter), then drop and sweep back across the bottom row (turn coordinator, heading indicator, VSI), forming a rectangle. Every instrument receives equal attention, which can be useful in unusual attitudes or partial-panel work but tends to over-emphasize secondary instruments in normal flight.

In a glass cockpit (PFD), the same logic applies: attitude information is centered, with airspeed, altitude, vertical speed, and heading arrayed around it. The pilot's eyes still return to the attitude reference between checks of the data tapes.

Common Cross-Check Errors

The IFH highlights several errors that disrupt an effective scan:

  • Fixation. Staring at one instrument — for example, watching the altimeter unwind during a descent — to the exclusion of the others. The aircraft's attitude can change significantly while attention is locked.
  • Omission. Failing to include an instrument in the scan, such as forgetting the heading indicator during altitude changes and allowing heading to drift.
  • Emphasis. Placing too much importance on a single instrument and using it as the sole reference for control inputs, instead of cross-checking it against others.

Building an Effective Scan

A good scan has three characteristics: it is systematic, deliberate, and adaptive. Systematic means the eyes follow a repeatable pattern. Deliberate means the pilot consciously interprets what each instrument shows rather than glancing past it. Adaptive means the pattern shifts with the maneuver — during a level turn the heading indicator and turn coordinator demand more attention; during an altitude capture the altimeter and VSI dominate; during airspeed transitions the airspeed indicator gets more glances.

Example: Straight-and-Level Cruise

Using a selected radial cross-check, the pilot might scan: AI (wings level, pitch on the horizon) → altimeter (3,000 ft, no trend) → AI → heading indicator (090°) → AI → airspeed (110 KIAS) → AI → VSI (zero) → AI. Each glance lasts a fraction of a second, and the AI is the constant reference.

Example: Level Standard-Rate Turn

AI (establish ~15° bank) → turn coordinator (verify standard rate) → AI → altimeter (hold altitude) → AI → heading indicator (track rollout heading) → AI. Pitch and bank are set on the AI; the turn coordinator and altimeter confirm performance.

Trim and Workload

A properly trimmed airplane reduces the physical effort of holding attitude and frees mental capacity for the scan. An out-of-trim airplane forces the pilot to fight the controls, which inevitably leads to fixation and omission. Trim is therefore part of an effective cross-check, not separate from it.

Summary

  • The scan is a continuous cross-check of attitude and performance instruments.
  • Three common patterns: selected radial (most common), inverted-V, and rectangular.
  • Most pitch and bank control comes from the attitude indicator; supporting instruments verify performance.
  • The three classic errors are fixation, omission, and emphasis.
  • Effective scans are systematic, deliberate, and adapt to the maneuver and phase of flight.
Oral Exam Questions a DPE Might Ask
Q1What are the three common cross-check (scan) patterns described in the Instrument Flying Handbook?
The selected radial cross-check, where the eyes return to the attitude indicator between each supporting instrument; the inverted-V cross-check, from the AI to the turn coordinator and VSI; and the rectangular cross-check, sweeping across the top and bottom rows of the panel.
Q2What are the three most common scan errors, and how do you recognize them?
Fixation is staring at one instrument while attitude changes elsewhere. Omission is leaving an instrument out of the scan, such as letting heading drift during an altitude change. Emphasis is relying on a single instrument for control instead of cross-checking it against others.
Q3Which instrument should be the focal point of your scan in normal attitude instrument flight, and roughly how much time should you spend on it?
The attitude indicator is the primary reference because it directly displays pitch and bank. In a selected radial scan, roughly 80–90% of scan time is on the AI, with brief glances at the supporting instruments to verify performance.
More from IFH Chapter 4
Control and Performance Method
Cross-Check Techniques (Instrument Scan)
Primary and Supporting Instruments
Drill it, not just read it
Adaptive questions on every IFH topic.

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Instrument Scan Patterns: IFH Chapter 4 | GroundScholar