✈️ K1c – Powerplant and Propeller

Q: What engine does the C172S have?

Lycoming IO-360-L2A, 180 HP, fuel-injected, air-cooled, direct-drive, four-cylinder.

Q: What does "IO" mean?

"I" fuel-injected, "O" horizontally opposed.

Q: What kind of propeller?

Fixed-pitch, two-blade, aluminum.

Q: What are the four strokes?

Intake, compression, power, exhaust.

Q: How is mixture controlled?

Manually by pilot adjusting fuel-to-air ratio.

Q: What are signs of detonation?

Roughness, loss of power, high CHT.

Q: What causes pre-ignition?

Hot spots igniting mixture early.

Q: What do magnetos do?

Provide spark independent of battery.

Q: How does fuel injection differ from carburetion?

Delivers fuel directly to cylinders—no venturi icing.

Q: What is normal oil capacity?

6-8 quarts (min 5 for flight).

Q: What is vapor lock?

Fuel vaporizes in lines, blocking flow.

Q: How does the propeller create thrust?

Airfoil shape produces lift horizontally.

Q: What is shock cooling?

Rapid cylinder cooling causing metal stress.

Q: What are EGT and CHT used for?

Monitor combustion and temperature for mixture control.

Q: What happens if one mag fails?

Small RPM drop; redundancy remains.

Q: DPE: "During run-up the right-mag drop is 200 RPM and rough—what now?"

Lean mixture and burn off plugs; if roughness persists, shut down and call maintenance.

Q: Climb power, rough engine, fluctuating fuel flow—what's happening?

Air in line or injector clog; enrich mixture, check pump, land if unresolved.

Q: DPE: "How do you confirm an alternator-belt failure?"

Ammeter shows discharge, low-voltage light on, but engine still runs (mags independent).

Q: Sudden oil-pressure drop with rising temp—what's your response?

Reduce power, mixture rich, divert immediately—possible imminent failure.

Q: DPE: "How can you detect detonation in flight?"

Loss of power, high CHT, knocking sound; enrich, lower power, open cowl flaps if equipped.

Q: Engine stumbles right after fuel-tank switch—likely cause?

Air bubble or vapor; turn boost pump ON, wait for smooth operation.

Q: DPE: "Describe hot-start procedure for the 172S fuel-injected engine."

Mixture idle-cutoff, throttle open ½ in, crank, advance mixture when it fires.

Q: Engine rough at idle after run-up—what do you check?

Lean to clear plugs, verify mag grounding, ensure mixture full rich before takeoff.

Q: DPE: "What could cause a cylinder head to overheat?"

Lean mixture, high power, low airspeed, or blocked cooling fins.

Q: On descent, engine runs rough—why?

Mixture over-rich from denser air; lean slightly.

Q: DPE: "You see oil on the windshield—what's your action?"

Possible prop-seal leak; reduce power, divert, monitor oil pressure.

Q: Engine quits on takeoff roll—steps?

Thro ttle idle, maintain control, brake, mixture cut-off, mags OFF.

Q: DPE: "What is the first action in any partial-power loss?"

Maintain best glide, then troubleshoot (fuel, mixture, mags, pump, throttle).

Q: Engine vibration increases with RPM—likely cause?

Propeller imbalance or loose spinner.

Q: DPE: "Why does fuel injection reduce carb-ice risk?"

No venturi fuel vaporization; no freezing potential.

Q: EGT suddenly drops on one cylinder—interpretation?

Injector clogged or plug fouled; land and inspect.

Q: DPE: "Explain how to lean properly for cruise."

Lean to peak EGT then enrich 50°F for best power.

Q: Engine loses oil-pressure indication but temperature normal—what now

Suspect gauge or sender failure; continue at reduced power, monitor closely.

Q: DPE: "What's your procedure for engine fire in flight?"

Mixture cutoff, fuel OFF, master OFF, airspeed 100 KIAS to extinguish, land ASAP.

Q: During magneto check you switch OFF and engine keeps running—why?

Mag grounding fault; ignition circuit shorted open—do not fly.

Q: DPE: "Explain how the induction system provides alternate air."

Door opens automatically if intake filter blocked, routing warm air from cowling.

Q: How would you detect pre-ignition before detonation damage occurs?

Gradual roughness and power loss under steady power; immediate throttle reduction prevents failure.

Q: Why are there two spark plugs per cylinder?

Better combustion efficiency and redundancy.

Q: What is the consequence of using low-octane fuel?

Deto nation and potential piston damage.

Q: DPE: "What's the risk of long, steep descents with low power?"

Shock cooling—uneven cylinder contraction, possible cracking.

Q: How does oil aid in engine cooling?

Carries heat from engine to oil cooler and dissipates through airflow.

Q: What causes high EGT but low CHT?

Lean mixture producing hot exhaust but not sustained cylinder heating.

Q: DPE: "Why is fuel-flow gauge important in a fuel-injected system?"

Indicates mixture and engine performance; abnormal changes suggest injector or pump issues.

Q: What could cause an alternator to affect engine performance?

Excess load on belt drive—rare; electrical failure won't stop ignition since mags are independent.

Q: DPE: "Describe how manifold pressure changes with altitude in a fixed-pitch prop airplane."

It automatically drops with altitude since no constant-speed control; pilot monitors power by RPM.

Q: Why is it dangerous to run excessively rich at high altitude?

Fouled plugs, incomplete combustion, loss of power.

Q: DPE: "If an injector nozzle partially blocks, what will CHT show?"

One cylinder cooler due to less fuel; engine roughness develops.

Q: Why should mixture be leaned for taxi?

Prevent plug fouling and rough running from overly rich mixture at low power.

Q: DPE: "Explain what happens if magneto timing drifts."

Spar k occurs too early or late—reduced efficiency, possible detonation.

Q: What is the engine's redline RPM and meaning?

2700 RPM; maximum continuous limit—exceeding may cause mechanical failure.