System abnormalities and failures

This element is about how the airplane tells you a system has failed and what you do about it — the failure-recognition card you carry into the cockpit, plus the checklist discipline that makes the procedures actually work under stress. The decision-framing (when to declare, when to divert, how to weigh severity) lives in the systems risk-management element (R1). Here we stay close to the indication, the inference, and the immediate response.

Every failure has the same shape: an indication you can scan for, an inference about which chain just broke, immediate-action items you have memorized, and a checklist you read to clean up. Speed comes from pattern, not panic.

indication taxonomy

Failures speak through five channels. The scan is what catches them; knowing the channels is what makes the scan worth doing.

• Instrument anomaly — a gauge moves out of band. Oil pressure trending down, ammeter steady discharge, suction creeping to zero, fuel flow dropping. The instrument is doing its job — the question is which system it represents.
• Annunciator — a warning light or text message. Low-volts, low-fuel, oil-pressure annunciators on a 6-pack; CAS messages on a G1000 PFD. Designed to be unmissable; if one's lit, treat it as truth until cross-checked.
• Sensory cue — sound (engine roughness, prop ice slap, an airflow change), smell (burning insulation, raw fuel, hot oil), vibration (engine, prop, airframe). The first cue is often a sense, not a gauge.
• Control-feel change — heavy or asymmetric controls, a runaway trim wheel, an autopilot that won't behave. These are felt before they're seen.
• Performance shortfall — the airplane won't accelerate to the expected number, won't hold altitude at the expected power, won't climb at the expected rate. Performance trailing the book is one of the slowest signals to develop but one of the most reliable.

per-failure recognition cards

Each card is the same shape: indication → cause inference → immediate action → follow-up. The systems themselves are covered in the systems element (K1).

• Engine roughness — RPM fluctuates or the note changes. Causes (most likely first): carb ice, fuel issue, mag failure, plug fouling, mixture, induction blockage. Immediate: carb heat full ON, fuel selector to BOTH, check mixture, mag check L/R/BOTH to isolate. If unresolved, divert.
• Oil pressure loss — gauge below green. Cross-check oil temperature; if rising, the loss is real. Immediate: reduce power to minimum for level flight, declare emergency, land at the nearest suitable airport. Land NOW — engine seizure is the endpoint.
• Alternator / electrical — ammeter steady discharge, low-volts annunciator. Bus is on battery; finite budget. Immediate: shed non-essential loads (lights, pitot heat in VMC, extra radios), preserve essentials, declare, divert to nearest suitable airport with an approach you can fly.

• Vacuum pump failure (6-pack only) — suction gauge drops toward zero; AI and HI become invalid within ~30 seconds as gyros spin down. Cover the two failed instruments. Partial panel: turn coordinator + airspeed + altimeter + VSI + magnetic compass. On a G1000 there is no vacuum pump and no vacuum-failure mode — the equivalent failure is an AHRS/electrical issue indicated by the PFD attitude red-Xing.

• Pitot blockage — ASI errs (acts like an altimeter if the drain is also blocked: reads high in a climb, low in a descent). ALT and VSI unaffected. Immediate: pitot heat ON; if it doesn't recover, fly attitude + power and use the GPS groundspeed as a sanity check.
• Static blockage — altimeter freezes, VSI reads zero, ASI errs in the opposite direction from a pitot block. Immediate: open the alternate static source; expect a small reading bias (typically the altimeter reads slightly high) and apply the POH correction.
• Engine fire — flame or smoke from the cowl, instrument-panel haze, burning smell. Memory items: Mixture IDLE CUTOFF, Fuel selector OFF, Master OFF, dive to blow out, land or forced-landing as conditions allow. Do not attempt to restart.
• Electrical fire — smell of burning insulation, smoke from a vent or behind the panel. Immediate: Master OFF, vent the cabin, isolate (if you need a system back, re-power one item at a time). Land at the nearest suitable airport.
• Carbon monoxide — headache, drowsiness, nausea, often with a CO detector alert. Most common entry path is the cabin heat shroud around the exhaust. Immediate: cabin heat OFF, vents OPEN, supplemental O2 if equipped, land for exhaust-system inspection.
• Fuel anomaly — fuel pressure or flow off-nominal, gauges disagreeing with expected burn. Immediate: switch selector to BOTH, verify quantity, check the selector position. If contamination is suspected, plan a landing at the nearest suitable airport.
• Control jam / runaway trim — control resists movement or trim runs without input. Immediate: disconnect autopilot, apply opposing trim or manual force, land — partial controllability is enough for a controlled landing if you fly the airplane all the way through it.

the response pattern

Every card above resolves the same way.

1. Recognize — the scan catches the indication.
2. Infer — the indication names which chain just broke (K1's mental model is what makes this fast).
3. Memory items — execute the 1-3 immediate actions from memory.
4. Checklist — read POH Section 3 to clean up anything memory missed.
5. Decide — declare, divert, continue. The decision-tempo framework lives in R1.

Aviate-navigate-communicate stays first principle through all five steps: fly the airplane, then navigate to a safe outcome, then talk to ATC. Memory items keep the airplane safe through the first 30 seconds; the printed checklist is the verification that nothing important was missed; the decision is what makes the whole thing land somewhere appropriate.

checklist discipline

The procedures are only as good as the discipline that runs them.

• Do-list vs checklist. A do-list is read-then-do — right for rare, complex, or learning procedures (preflight on an airplane you don't fly every day, an emergency you've never run for real). A checklist is do-then-verify — fly the flow from memory, then read the list to confirm nothing was missed. Flow + verify is the professional standard for routine ops because it is faster than read-and-do and more reliable than memory alone.
• Touch and verify. Touch each control as you name it. "Master, ON" — and your hand is on the switch as you say it. Physical contact prevents the "I think I did that" shortcut; the verify step catches what touch misses.
• Emergencies are memory-then-read. Memorize the 1-3 immediate-action items per procedure; everything else gets read. Memorizing the full list trades reliability for speed in the wrong direction.
• Don't catch up by skipping. Behind the airplane is a state to fix, not a debt to pay. Slow down, request a delay, go around, hold — but complete each step as written.
• POH is authoritative. Per 14 CFR 91.9 you must comply with the AFM/POH; school or branded checklists are presentations of those procedures and must trace back. POH wins any conflict §91.9. The AFH walks the technique of running checklists under stress FAA-H-8083-3.

worked examples

Scenario 1 — engine fire on takeoff climb.

Just after liftoff you see smoke from the cowl and the instrument panel hazes over. Burning smell. The indication is unambiguous; there is nothing to troubleshoot.

Memory items immediately: Mixture IDLE CUTOFF, Fuel selector OFF, Master OFF. Dive to blow it out if airspeed permits. Land straight ahead or in a shallow turn to the most suitable surface; do not attempt to return to the runway from low altitude — the impossible-turn geometry doesn't work below pattern altitude. Decision: land NOW, even on a poor surface; airborne fire kills fast and the survivable landing wins over the survivable fire on a runway you cannot reach.

Scenario 2 — vacuum failure in IMC cruise.

Cruising on an IFR clearance in cloud, you catch on the scan that the suction gauge has crept to zero. The AI is starting to roll off slightly; the HI is drifting against the compass.

Recognize (suction gauge) → infer (vacuum pump → AI + HI compromised) → cover the two failed instruments and start the partial-panel scan: turn coordinator + airspeed + altimeter + VSI + compass. Declare to ATC and request vectors to the nearest suitable airport with an approach you can hand-fly on partial panel. Decision: divert to the nearest field where you can fly an approach you trust on partial panel — not the original destination. The chain (K1) is what made the failure name itself in seconds; the procedure is what kept the airplane upright while you decided.