Partial-panel flying

Start with usable information, not a covered dial

Partial-panel flying means controlling and navigating with a reduced set of reliable instruments after a failure. The missing item may be a mechanical attitude/heading gyro, one display screen, an AHRS, air data, electrical power, or several shared dependencies. This lesson applies the recognition principles in instrument and avionics failures to the approach decision; it does not repeat every failure mechanism.

Maintain control while comparing independent information and validity indications. A slowly drifting vacuum attitude gyro can remain convincing. Two displays driven by the same failed AHRS or ADC are not independent backups. Identify what failed, what still receives valid data/power, and what the aircraft manual permits you to use. If an instrument is positively identified as unreliable, preventing it from drawing your attention may help, using the appropriate equipment procedure; do not cover the only reliable reference or dismiss an unexplained disagreement.

IFH 11-7–11-8: instrument and pneumatic-system failure · ACS VII.D: loss of primary flight instrument indicators

Cross-check performance without chasing lag

If no usable attitude indicator remains, use the available reliable performance instruments together with known aircraft pitch/power/configuration relationships practiced with an instructor. A conventional turn instrument supplies turn-rate/direction information, not a complete pitch/bank picture. Altitude, vertical speed and airspeed help interpret pitch performance; heading or a stabilized compass reference helps direction. Each has limitations and must actually be usable after this failure.

For example, with an electrically powered turn coordinator and pressure instruments still valid after vacuum failure, reduce the task to a stable heading, altitude and airspeed. Use small, smooth corrections, confirm their effect, and recheck the other axes. A lagging VSI is a reason to allow the response to settle, not a reason to make a larger correction. Fixating on altitude can allow a turn or speed change to develop unnoticed.

Do not infer a universal pitch angle or power setting from this example. The instructor must establish appropriate values and control techniques in the actual airplane. If pressure data are also invalid, the usual altitude/airspeed cross-check is no longer reliable; use the actual failure checklist and independent information, and treat the additional loss as a major capability change. GPS groundspeed is not indicated airspeed.

IFH 7-36: partial-panel performance cross-check · IFH 11-7–11-8: use of remaining functional instruments

Use a directional reference that remains valid

If the heading indicator fails but the magnetic compass and turn instrument remain usable, plan changes with their limitations in mind. Compass turning errors are strongest near north/south headings; acceleration errors are strongest near east/west headings. Their direction depends on the hemisphere, as explained in the magnetic compass lesson. A transient reading during a turn is not a precise bank or heading reference. Use instructor-practiced turn-rate/timing techniques and stabilized compass checks, with wind correction for the actual track. For a verified standard-rate 3°/second turn in still air, a 30° heading change takes about ten seconds; roll-in/out and actual rate affect the result.

With a usable standby heading or approved reversionary display, that may provide more complete information. Confirm its power, sensor and alignment instead of assuming “standby” means independent. A GPS track depicts movement over the ground; wind makes it differ from heading, and near-zero groundspeed or invalid GPS data can make it unsuitable. It does not become an attitude or turn-rate instrument because the primary gyro failed.

Reduce maneuvering demands when possible. Ask for a manageable vector or route, avoid unnecessary steep turns, and allow time to configure and brief. Rate turns, magnetic-compass technique and recovery from unusual attitudes need safe instructor-led practice; this written example is not a solo IMC experiment.

IFH 7-21: compass limitations and timed turns · IFH 7-36: partial-panel concepts · IFH 11-7–11-8: failure control · ACS VII.D.R2/R3: control and distraction

Check the inputs before trusting automation

An autopilot or flight director can use the same attitude, heading, air data or navigation source that failed. Unexpected commands, invalid sources or inability to verify the mode require prompt use of the approved disconnect/reversion procedure and manual control with reliable references. An autopilot is useful only when its required information and operating status remain valid.

For a display-screen failure with serviceable sensors, the aircraft may provide an approved reversionary display. Follow its procedure, then verify attitude, heading, altitude/airspeed, navigation source and any annunciated failures. A menu change cannot repair a failed sensor. Backup batteries have installation-specific endurance and loads; determine the actual supported equipment and plan a timely landing without inventing a “forty-minute” guarantee.

Before flight, practice the actual controls with an instructor: which button disconnects automation, which display can show reversionary data, which standby source is independent, and which alerts or limitations forbid continued use. During an unexpected failure, do not explore unfamiliar menus at the expense of control.

IFH 11-4–11-7: electronic-display/power failures · ACS VII.D.K2: failure effects and mitigation

Tell ATC what you can and cannot do

Report the malfunction and its operational effect as soon as practical. Under 91.187 in controlled airspace under IFR, a navigation, approach or communication equipment malfunction report includes identification, affected equipment, how IFR capability is impaired, and the assistance desired. Even when the failed item is a flight instrument, communicate a control or clearance limitation promptly and request help.

Example: “Primary attitude and heading indicators failed. Maintaining control on remaining instruments. Unable the published procedure turn; request vectors to a suitable approach and a longer final.” State the actual capability, not just “partial panel.” If needed, declare an emergency so ATC understands the urgency. ATC cannot see all your limitations and cannot make the aircraft airworthy.

Select an airport and approach using remaining independent attitude/performance references, navigation and communication, weather, terrain, runway, fuel and workload. A working localizer or GPS signal alone does not solve a loss of flight control information. A simpler approach with better weather and radar assistance may reduce demands, but its actual equipment, chart and minimums still govern. If you cannot comply, say so before accepting the clearance.

14 CFR 91.187: malfunction reports · ACS VII.D.S1: advise inability to comply · AIM 6-2: emergency assistance

Prepare the failed-instrument approach before final

The ASEL ACS VII.D task prepares for a nonprecision approach without the primary flight instruments, using the nonprecision task's skill elements. That is a supervised practical-test/training task, not a claim that every failure leaves an actual nonprecision approach safe. Your real remaining equipment and urgency determine the operational choice.

Brief a usable approach and its navigation source, fixes, courses, segment altitudes, step-downs, MDA, visibility, MAP and missed instructions. Establish the aircraft's appropriate configuration and stable performance early. Apply the charted restrictions and use a valid MAP-identification method; do not assume timing is always available or that a GPS advisory glidepath removes a step-down or MDA.

During final, cross-check lateral course information, the remaining reliable heading/turn indication, altitude trend, airspeed, power and configuration. At MDA, remain at or above it until the applicable descent/landing requirements are met; without them, execute the missed at the MAP. Use a manageable missed route with the actual remaining references. If the aircraft cannot follow the published procedure, communicate that before final and obtain appropriate instructions or use emergency judgment.

With an instructor, practice timely configuration, valid reference selection, checklists, lateral/vertical control, minima/MAP recognition and a missed approach. Actual tolerances and proficiency belong to the flight evaluation; completing the quiz only checks these concepts.

ACS VII.D.S2 and VI.A: nonprecision approach with primary indicators unavailable · 14 CFR 91.175: descent and missed requirements · AIM 5-4: approach guidance and missed approach

Replan after a vacuum failure

Fictional equipment example: in IMC, the vacuum gauge falls and the mechanical attitude and heading gyros disagree with the electrically powered turn coordinator. Separate pressure instruments remain consistent with power and the climb/level-off history; installed navigation and communication remain powered. You have practiced this failure in this aircraft with an instructor. A nearby airport has better weather and a suitable nonprecision procedure.

Maintain control using the verified remaining references, follow the actual failure checklist, and prevent positively identified failed gyros from misleading the cross-check. Disconnect automation if its required sources are invalid, following the aircraft procedure. Tell ATC the capability loss and assistance needed; evaluate the nearby airport and approach against real charts, fuel and limitations rather than continuing to the original destination out of habit.

Identify a second failure that would invalidate the plan: pressure indications becoming unreliable, loss of the turn instrument's electrical source, insufficient approach-navigation capability, or backup-power depletion. These are reasons to reassess urgency and options immediately. A practice session should use safe simulated failures and preserve working instruments/ATC access as the instructor requires.

IFH 11-7–11-8: vacuum failure and remaining references · ACS VII.D: approach with loss of primary indicators

FLIGHT SCENARIO

What would change your plan?