Systems & equipment malfunctions

A malfunction isn’t always an emergency

Definition

Not everything that breaks is an emergency. A malfunction is anything abnormal; an emergency is an immediate threat. The skill: recognize what’s happening, keep flying the airplane, troubleshoot in order, then decide — land as soon as practical (an abnormal you manage) or as soon as possible (a threat you can’t). The classic trap is startle: a door pops open on climbout — loud and alarming, but the airplane flies fine, and pilots have crashed trying to fix it instead of flying.

Explanation

Most malfunctions leave you a flyable airplane — the real hazard is overreacting. Control the airplane first, then work the problem: recognize, control, analyze, act.

The call	What it means
Land as soon as PRACTICAL	An abnormal you can manage — finish flying to a suitable airport and get it looked at (e.g., alternator failure, a rough-but-running engine that smoothed out).
Land as soon as POSSIBLE	A real threat that’s getting worse — take the nearest survivable option now (a fire, a failing engine you can’t restore).
The startle trap	A door popping open is loud and alarming, but the airplane flies fine. Fly it first — don’t crash trying to fix a non-problem.
The order every time	Recognize → keep flying → troubleshoot → decide (practical or possible).

Why it matters

The number-one killer in a minor malfunction is startle — the pilot stops flying to chase the problem. An open door, a popped breaker, a warning light: fly the airplane first, every time.

Common error

A sudden noise or light makes pilots freeze or fixate. The airplane still needs flying.

The cabin door pops open just after takeoff. Your first action is to:

Airplane Flying Handbook — Emergency procedures — systems malfunctions

Partial power loss / rough engine

Definition

The engine runs but not right — rough, low power, or surging. First ask: is it making enough power to hold altitude? Fly the airplane, then troubleshoot the usual causes: carb heat ON (carb ice is the #1 cause of a rough engine in a carbureted trainer), mixture (too lean or too rich runs rough), a mag check (switch L then R — a fouled plug or failing magneto), and fuel (selector to a good tank, boost pump, primer locked). If it smooths out, land as soon as practical. If it keeps deteriorating toward a total failure, it has escalated — run the engine-failure flow.

Explanation

Work the causes in order rather than guessing. Carb heat first on a carbureted engine, then mixture, mags, and fuel — the things that make an engine run.

Rough / partial power	Try this (exact items: POH)
First — fly	Is it making enough power to hold altitude? Pitch for the airspeed you need, then troubleshoot.
Carb heat	ON — carburetor ice is the #1 cause of a rough engine in a carbureted trainer.
Mixture	Adjust — too lean or too rich runs rough; enrichen for the altitude.
Magnetos	Switch L, then R — a fouled plug or a failing mag runs rough on one side.
Fuel	Selector to a good tank · boost pump on · primer in & locked.
Then decide	Smoothed out? Land as soon as practical. Getting worse toward total? Run the engine-failure flow (M7.1).

Why it matters

A rough engine is often a fixable partial — carb ice clears with heat, a fouled plug clears with leaning. But it can also be the first sign of a total failure, so you troubleshoot AND keep a landing spot in mind.

Common error

Students jump to the mixture or the mags and forget carb heat — the single most common cause.

Your carbureted trainer’s engine starts running rough in cruise. The first thing to try is:

A DPE might ask

Rough engine in cruise — walk me through your troubleshooting.
How do you tell carb ice from a fouled plug?

Airplane Flying Handbook — Partial power loss / rough engine

Electrical / alternator failure

Definition

A low-voltage light or a discharging ammeter means the alternator has quit — you’re now running on the battery, and it won’t last. Respond: try the POH reset once (alternator/field off, then on), reduce electrical load (shed non-essentials per the POH), keep what you truly need (comms, and enough for the landing), and land while you still have power. It’s an abnormal, not an emergency — but the battery clock is running, so land as soon as practical.

Explanation

The battery is a reserve, not a supply — minutes, not hours, depending on load. Shedding load stretches it; landing promptly is what actually solves it.

Alternator failure	Do this (per POH)
Recognize	A low-voltage light or a discharging ammeter — you’re now on the battery.
Reset once	Try the POH reset — alternator/field off, then on — a single time.
Shed load	Turn off non-essential electrics; keep comms and enough for the landing.
Land practical	The battery won’t last — land while you still have power for radios and flaps.

Why it matters

Run the battery flat and you lose radios, flaps, and electric instruments on final. Managing the load and landing while you still have power keeps the failure an inconvenience, not an emergency.

Common error

Ignoring a low-voltage light — or leaving everything on — drains the battery right when you need it for landing.

The low-voltage light comes on in cruise. What’s happened, and what do you do?

Airplane Flying Handbook — Alternator / electrical failure

Instrument failures — recognize & fly the good ones

Definition

Instruments fail quietly. A vacuum or gyro failure makes the attitude indicator and heading indicator slowly lie — cross-check them against the others, and if they disagree, trust the turn coordinator, airspeed, altimeter, and compass. A pitot or static blockage makes the airspeed, altimeter, and VSI misbehave — use the alternate static source and cross-check. The skill here is recognition: knowing which instruments to distrust. The partial-panel flying technique itself is Module 4.

Explanation

No red flag pops up when a gyro spins down — the instrument just drifts. Catching it means comparing instruments against each other and against the airplane’s feel.

Instrument failure	Recognize → trust
Vacuum / gyro	The attitude & heading indicators slowly LIE. Cross-check; trust the turn coordinator, airspeed, altimeter, compass. Technique: M4.4.
Pitot / static blockage	Airspeed, altimeter, and VSI misbehave. Use the alternate static source and cross-check (M4.1).
The skill here	Recognition — know which instruments to distrust. Flying partial panel is the M4.4 technique.

Why it matters

A slowly-failing attitude indicator has led pilots into spirals in cloud. Recognizing the failure — and trusting the instruments that still work — is the difference between a non-event and a loss of control.

Common error

Believing the failed instrument because it looks normal — the whole danger of an insidious gyro failure.

In steady level flight the attitude indicator shows a slight bank, but the turn coordinator and compass say you’re wings-level. Which do you suspect?

PHAK — Flight instruments — failures

Controls & configuration

Definition

Malfunctions that change how the airplane handles. A trim runaway or failure — hold the control pressure, disable the electric trim per the POH, and fly on manual trim. A flap failure or asymmetric (split) flaps — don’t force it; land with the flaps you have (a faster, flatter, no- or partial-flap approach and a longer rollout). A door or window open in flight — it’s loud and drafty but the airplane flies; secure it if you safely can, otherwise land and close it. In every case: fly first, then land as soon as practical.

Explanation

None of these stop the airplane from flying — they change how it flies. Fly the airplane you now have, and plan the approach around it.

Controls / config	Response
Trim runaway / failure	Hold the control pressure, disable the electric trim per the POH, fly on manual trim.
Flap failure / asymmetry	Don’t force it — land with the flaps you have: faster, flatter approach, longer rollout.
Door / window open	Loud and drafty, but it flies. Secure it if you safely can; otherwise land and close it.
Every case	Fly first, then land as soon as practical.

Why it matters

A flap or trim problem is a handling change, not a loss of control — unless you fight it. Knowing the no-flap approach is faster and the runaway trim gets disabled turns these into routine precautionary landings.

Common error

Trying to force a jammed flap or salvage a normal-flap profile instead of flying the configuration you have.

The flaps won’t extend on downwind. You:

Airplane Flying Handbook — Flight control & configuration malfunctions

The malfunction decision

Definition

The through-line: recognize → fly the airplane → troubleshoot systematically → decide (practical vs. possible). Any malfunction can escalate — a rough engine can become a total failure, smoke can become a fire. Keep reassessing; the moment it crosses into an immediate threat, switch to the emergency response. And when in doubt, declare — help costs nothing, and ATC would rather roll the trucks and cancel than find you the hard way.

Explanation

The discipline is matching the response to the severity — neither overreacting to a non-problem nor pressing on with a problem that’s growing.

The decision	How it goes
Recognize → fly	Name the problem; keep flying the airplane before anything else.
Troubleshoot	Work the checklist / memory items in order — don’t guess.
Decide	Practical (manage it) vs. possible (get down now) — match the response to the severity.
Watch for escalation	Rough engine → total failure (M7.1); smoke → fire (M7.2). Reassess constantly.
When in doubt	Declare — help costs nothing, and you can always cancel.

Why it matters

Most accidents from malfunctions come from the two extremes — startle-driven overreaction, or stubbornly pressing on. Recognize, fly, decide, and keep reassessing.

Common error

Sticking with the abnormal label after the situation has clearly become an emergency.

A partial power loss is now so severe you can’t hold altitude. Is this still just an abnormal?

Airplane Flying Handbook — Emergency procedures