Partial Panel (Loss of Primary Flight Instruments)
Partial-panel flying means controlling the airplane after losing primary instruments — classically a failed attitude indicator and heading indicator (vacuum/AHRS failure). You fly using the remaining instruments (airspeed, altimeter, VSI, turn coordinator, magnetic compass, or a backup display) and apply compass turn corrections.
Step by step
- 1Recognize and confirm the failure (e.g., a slowly toppling attitude indicator, a flagged display, or a vacuum gauge in the red).
- 2Maintain control using the remaining instruments: the turn coordinator for bank/heading, the airspeed/altimeter/VSI for pitch, and the magnetic compass for heading.
- 3Fly small, smooth control inputs and a deliberate cross-check of the partial set of instruments.
- 4For heading changes, use timed standard-rate turns on the turn coordinator and verify with the compass.
- 5Account for compass errors: ONUS / UNOS — turning to NORTH, undershoot the rollout; turning to SOUTH, overshoot (in the Northern Hemisphere) — and watch acceleration/deceleration error (ANDS) on east/west headings.
- 6Manage the workload: tell ATC, request help/vectors as needed, and proceed to a suitable airport/approach partial panel.
Tips & common errors
- Pitch from airspeed/altimeter/VSI, bank/heading from the turn coordinator and compass — and trust them.
- Timed turns at standard rate (3°/sec) are the reliable way to change heading without an HI.
- Compass rules: UNOS (Undershoot North, Overshoot South) on turns; ANDS (Accelerate North, Decelerate South) on E/W headings.
- Reduce workload — engage the autopilot/backup if available, declare if needed, and keep the airplane upright and on altitude first.
ACS completion standards
The commonly-tested tolerances for this maneuver. Always confirm the current ACS for your certificate.
- Maintain control and the assigned altitude ±100 feet, heading ±10°, and airspeed ±10 knots using the available instruments.
- Recognize the failed instrument(s) and continue safely (often to an approach) partial panel.
- Use proper compass-turn technique and manage workload/ATC coordination.
FAA source
FAA-S-ACS-8 (Instrument Rating ACS), Tasks: Instrument Flight w/ failures & approach with a loss of primary flight instruments; Instrument Flying Handbook FAA-H-8083-15, Chapters 7–8.
This is an original, plain-English study summary grounded in the public-domain FAA Airman Certification Standards and FAA handbooks cited above. It is a study aid, not flight instruction, and not a substitute for the official ACS, the handbooks, your aircraft’s POH/AFM, or a certificated flight instructor.
Related maneuvers
- Attitude Instrument Flying & the Instrument ScanAttitude instrument flying is the foundation of all instrument flight: you control the airplane by interpreting the instruments instead of looking outside. You set an attitude on the attitude indicator (control), verify the result on the other instruments (performance), and trim. A disciplined cross-check (scan) prevents fixation and keeps every parameter in tolerance.
- Constant-Airspeed Climbs & DescentsOn instruments you frequently change altitude at a constant airspeed. You set a pitch and power for the desired airspeed, hold it with the scan, and lead the level-off so you roll out exactly on the new altitude and back at cruise airspeed.
- Rate Climbs & Descents (Constant Vertical Speed)Sometimes you must hold a specific vertical speed (for example to meet a crossing restriction or to fly a constant descent rate on an approach). You adjust pitch and power to pin the VSI to a target rate while still controlling airspeed, then lead the level-off.
- Steep Turns (Instrument)On instruments, a steep turn (typically a sustained 45° bank) tests your cross-check and control as the higher bank increases the back-pressure and power needed to hold altitude. With no outside horizon, you must control everything by the attitude indicator and supporting instruments.
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