Commercial pilot · ACS CA.IX.C
Systems and Equipment Malfunctions
A commercial pilot knows each system on their airplane well enough to recognize a failure, keep flying, and work the checklist calmly.
Why this one matters
Systems failures rarely bring an airplane down by themselves; the pilot's reaction does. Startle, fixation and skipping the checklist turn a manageable failure into an undesired airplane state. A commercial pilot in a complex airplane has more systems and must know each one's failure and fix.
Can’t miss
- •Every malfunction starts the same way: fly the airplane, identify the problem, then run the checklist.(Airplane Flying Handbook (FAA-H-8083-3C), Emergency Procedures)
- •Power loss or a rough engine: best glide or the right airspeed first; carb heat on (carbureted); fuel selector to a tank with fuel or BOTH; mixture rich; fuel pump on if equipped; magnetos checked, then BOTH; then the checklist. With carb ice it may run rougher briefly as the ice melts; don't turn the heat off.(Airplane Flying Handbook (FAA-H-8083-3C), Emergency Procedures)
- •Alternator failure: shed electrical load, land before the battery runs out. Vacuum failure: cover the failed attitude and heading indicators, use the backups.(PHAK (FAA-H-8083-25C), Flight Instruments)
- •Blocked static source: altimeter frozen, VSI at zero, airspeed low above the blockage altitude and high below it; use the alternate static. Blocked pitot: with the drain blocked too, the airspeed acts like an altimeter; with the drain open, it falls to zero.(PHAK (FAA-H-8083-25C), Flight Instruments)
- •Landing gear won't extend: check the circuit breaker and position, then the manual (emergency) extension per the POH.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Complex and High-Performance Airplanes)
- •Electrical fire or smoke: master and alternator off, other electrical switches off except ignition, vents and cabin heat closed, extinguisher, land as soon as possible; ventilate only after the fire is out. Restore power one switch at a time only if the fire is out and you need it to keep flying, pausing after each.(Airplane Flying Handbook (FAA-H-8083-3C), Emergency Procedures)
- •An open door in flight is usually a noise problem, not a flying one: fly the airplane and land to close it.(Airplane Flying Handbook (FAA-H-8083-3C), Emergency Procedures)
What you should know
Power loss K1
- Common causes: fuel mismanagement (an empty tank selected, exhaustion), carburetor or induction icing, a magneto or ignition fault, an incorrect mixture, a turbocharger or fuel injection fault, roughness or overheating. Low or fluctuating oil pressure with rising oil temperature: land at the nearest suitable airport, since a complete failure may be close.(Airplane Flying Handbook (FAA-H-8083-3C), Emergency Procedures)
- A partial power loss can be more dangerous than a complete one, because it tempts you to press on. Treat it as an emergency and head for the nearest suitable airport.(Airplane Flying Handbook (FAA-H-8083-3C), Emergency Procedures)
Electrical, vacuum, pitot-static and displays K2
- Electrical: an ammeter discharge or low-voltage light means the alternator is off-line; reset per the POH, shed load, and land. Know which items are on which bus.(PHAK (FAA-H-8083-25C), Aircraft Systems (oxygen and pressurization))
- Vacuum: a low suction reading means the attitude and heading indicators will fail slowly; cross-check, cover them, and use the electric backups or partial panel.(PHAK (FAA-H-8083-25C), Flight Instruments)
- Pitot inlet and drain both blocked: the airspeed acts like an altimeter (rising in a climb, falling in a descent, no response to speed changes level). Inlet blocked, drain open: it falls to zero. Altimeter and VSI stay normal. Pitot heat treats pitot icing only.(PHAK (FAA-H-8083-25C), Flight Instruments)
- Static blocked: altimeter frozen, VSI at zero, airspeed low above the blockage altitude and high below it. The fix is the alternate static source; in most unpressurized airplanes the cabin pressure is a little lower, so the altimeter reads a little high, the airspeed fast, and the VSI shows a brief climb before settling; use the POH correction table. With no alternate source, breaking the VSI glass is the last resort.(PHAK (FAA-H-8083-25C), Flight Instruments)
- Electronic display failure: the other display usually shows reversionary mode; use the standby instruments and know how to select reversion.(PHAK (FAA-H-8083-25C), Flight Instruments)
- Gear or flap failure: check breakers and indications, then the POH emergency procedures (manual gear extension; a no-flap landing needs more runway). Inoperative or runaway trim: hold pressure, disconnect or pull the breaker, land.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Complex and High-Performance Airplanes; Your airplane's POH/AFM)
Smoke, fire, other systems and doors K3 · K4 · K5
- Electrical fire: master and alternator off, switches off except ignition, vents closed, extinguisher, then ventilate once it's out; restore only essential items, one at a time, only if needed to keep flying. Engine fire: fuel off and the POH procedure.(Airplane Flying Handbook (FAA-H-8083-3C), Emergency Procedures)
- Other systems, first action, then the POH: oxygen or pressurization failure, oxygen on and descend (below 10,000 feet cabin altitude for an oxygen failure); deice or anti-ice failure in icing, exit the icing; autopilot malfunction or runaway, disconnect and hand-fly; inoperative trim, hold the pressure and land.(Your airplane's POH/AFM)
- An inadvertently opened door or window: fly the airplane, don't try to close it in flight unless the POH says, and land.(Airplane Flying Handbook (FAA-H-8083-3C), Emergency Procedures)
The pilot's side R1 · R2 · R3 · R4
- Use the checklist, by memory for the immediate items, then by reading it, so you don't miss a step under stress.(Airplane Flying Handbook (FAA-H-8083-3C), Emergency Procedures)
- Startle is real: a sudden failure can freeze you for seconds. Pause, breathe, fly the airplane, then work the problem by the checklist.(Risk Management Handbook (FAA-H-8083-2A))
- An undesired airplane state (unusual attitude, low speed) often follows a malfunction you fixated on: keep the scan going.(Airplane Flying Handbook (FAA-H-8083-3C), Emergency Procedures)
Scenarios
Decide what you would do first, then see the worked answer.
The low-voltage light comes on at night.
What do you do? See the worked answer
Check the alternator breaker and reset once per the POH; if it stays off, shed load, tell ATC, and land at the nearest suitable airport while the battery lasts.
PHAK (FAA-H-8083-25C), Aircraft Systems (oxygen and pressurization)
The gear indicator shows unsafe after extension.
What do you do? See the worked answer
Fly away from the airport at a safe altitude, check the bulb and breaker, cycle once if the POH allows, then the manual extension, and have the tower look.
Airplane Flying Handbook (FAA-H-8083-3C), Transition to Complex and High-Performance Airplanes
Smoke and the smell of hot plastic.
What do you do? See the worked answer
Electrical fire checklist: master off per the POH, extinguisher if needed, ventilate, land as soon as possible.
Airplane Flying Handbook (FAA-H-8083-3C), Emergency Procedures
Common mistakes
Fixating on the failure.
The airplane drifts into an undesired state.
Instead: Keep flying; scan.
Skipping the checklist.
Steps get missed under stress.
Instead: Memory items, then read the checklist.
Pressing on with a partial failure.
It may get worse far from an airport.
Instead: Land at the nearest suitable airport.
Now train it
Say it out loud, hear it asked, and take the quick check in this lesson’s practice pack. It tracks your shaky spots.
Got it?
When it feels solid, practice systems and equipment malfunctions out loud with our examiner.
Your progress is saved in this browser. Create a free account to keep it on every device, with your shaky spots and mock oral results in one place.
Go to the source (free)
Teaching this? The instructor lesson plan →
Sources
- Airplane Flying Handbook (FAA-H-8083-3C): Emergency Procedures
- Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C): Aircraft Systems; Flight Instruments
- Aeronautical Information Manual (AIM): Chapter 6, Emergency Procedures
- 14 CFR Part 91: 91.3, 91.205, 91.207
- Commercial Pilot ACS (FAA-S-ACS-7B): Area IX
- Your airplane's POH/AFM: Emergency Procedures
Study aid, not FAA guidance. Regulations change; check the current text at eCFR and the ACS. Checked against current sources 2026-11-13.