✈️ K1b – Secondary Flight Controls

Q: What are the secondary flight controls?

Flaps and trim tabs.

Q: Purpose of flaps?

Increase lift and drag for slower, steeper approaches.

Q: How are flaps operated in the 172S?

Electrically by a motor controlled with cockpit switch.

Q: Maximum flap extension speeds?

10° = 110 KIAS; 20-30° = 85 KIAS.

Q: What type of flaps used?

Single-slotted.

Q: What does extending flaps do to stall speed?

Reduces it.

Q: Why retract flaps slowly?

Prevent sudden sink.

Q: What is the effect of nose pitching up with flaps?

Center of lift moves aft; downwash increases tail lift.

Q: What does the trim tab do?R

educes control pressure for steady flight attitude.

Q: How to check flaps on preflight?

Extend fully, verify smooth travel, hinges secure.

Q: What are risks of asymmetric flap extension?

Rolling and yawing toward retracted side.

Q: How does trim affect climb performance?

Doesn't change performance, just control effort.

Q: What's the failure mode for electric flap motor?

Jammed or partial extension; use POH abnormal checklist.

Q: What does full-flap go-around require?

Incremental retraction to prevent sink.

Q: Why should you not exceed Vfe?

Could damage flap system.

Q: DPE: "Flaps extend unevenly—what happens?"

Asymmetric lift; control roll with aileron, retract to match, go around if unstable.

Q: Flaps fail to extend—what's your plan?

Normal no-flap landing at higher speed, longer distance.

Q: DPE: "Describe effect of flaps on drag curve."

Moves curve left and up; more lift and drag at lower speed.

Q: Trim runaway occurs—what do you do?

Hold control opposite, pull breaker, disconnect autopilot, land.

Q: You forget to retract flaps—effect?

Reduced climb performance.

Q: DPE: "Why is trim important for instrument flight?"

Reduces workload and maintains stable attitude.

Q: Flap motor pops breaker—reset?

Once only; if trips again, discontinue use.

Q: DPE: "When might you use flaps 10° for takeoff?"

A: Short/soft field for lift boost.

Q: Nose pitches up sharply on flap extension—why?

Increased downwash over tail.

Q: DPE: "Flaps stuck half-down—how do you handle landing?"

Use appropriate approach speed and power; avoid abrupt pitch.

Q: Trim feels loose—fly?

No; possible tab linkage failure.

Q: DPE: "Can improper trim cause takeoff accident?"

Yes—excessive nose-up trim can cause premature lift-off/stall.

Q: Electric flap circuit inop but manual switch works intermittently—fly?

No; repair before flight.

Q: DPE: "How would you detect asymmetrical extension before it becomes dangerous?"

Watch roll response and visual flap position.

Q: Trim cable snaps in flight—what happens?

Trim freezes; continue holding pressure, land soon.

Q: DPE: "If flap position indicator fails, what do you do?"

Visually confirm position out the window.

Q: Full flaps in strong gusty wind—good idea?

No, increases lift loss risk—use partial flaps.

Q: DPE: "Why retract flaps gradually on go-around?"

Prevents sudden sink due to loss of lift.

Q: After landing, flaps won't retract—what might that indicate?

Electrical short or jammed motor.

Q: Why are slotted flaps more effective than plain flaps?

Slot allows airflow over flap to stay attached longer, increasing lift.

Q: What's the main risk of flap asymmetry?

Uncommanded roll.

Q: DPE: "Explain aerodynamic balance change with flaps."

Lift vector moves aft, increasing nose-down pitching moment.

Q: Why avoid rapid flap retraction on go-around?

Lift dump can cause sink or stall.

Q: How does trim interact with elevator?

Trim tab deflects opposite to elevator to aerodynamically "hold" attitude.

Q: DPE: "How would you identify a flap-motor failure during preflight?"

Switch click without movement or noise; breaker trip.

Q: How could ice affect flaps?

Prevents movement or causes asymmetry.

Q: Why is flap deployment prohibited above Vfe?

Structural load exceeds flap design limit.

Q: DPE: "How can incorrect rigging of flaps affect cruise performance?"

Increases drag, reduces airspeed.

Q: How does electric-trim runaway differ from manual-trim jam?

Runaway is uncommanded motion; jam is locked position.

Q: What's the effect of full-flap stall vs clean stall?

Occurs at lower speed but with sharper break.

Q: DPE: "How does aft CG affect trim?"

Requires more nose-down trim for stability.

Q: Why should trim always be neutral before takeoff?

Prevents excessive pitch-up or -down tendency.

Q: DPE: "What's the relationship between trim and stability?"

Proper trim enhances stability by balancing control forces.

Q: You extend flaps and circuit breaker doesn't pop, but motor smokes—what now?

Stop immediately; motor overheated—abort flight.