Run-Up and Before-Takeoff Checks

2.run-up-and-before-takeoff-checks. Run-Up and Before-Takeoff Checks

The run-up and before-takeoff check is the final systems verification performed before committing the airplane to flight. Its purpose is to confirm that the engine, magnetos, propeller, flight instruments, fuel system, and flight controls are all functioning correctly, and that the cockpit is properly configured for departure. Skipping or rushing this check has been a contributing factor in numerous engine-failure-on-takeoff accidents, so the AFH directs pilots to complete it deliberately and in accordance with the airplane's POH/AFM checklist.

Positioning the Airplane

The airplane should be parked in the run-up area:

• Headed into the wind whenever practical, to aid engine cooling and provide accurate static RPM.
• On a firm surface free of loose gravel, sand, or debris that could be ingested by the propeller or thrown into trailing aircraft.
• Clear of taxiways, with the tail not pointed at hangars, fuel pumps, or other aircraft.
• With the nosewheel (or tailwheel) straight and the brakes firmly held. On slick or icy surfaces, reduce run-up RPM as needed to prevent sliding.

Pre-Run-Up Configuration

Before advancing the throttle for the magneto check, complete the items the manufacturer specifies — typically:

• Parking brake set; toe brakes held.
• Flight controls checked free and correct (yoke/stick full travel, ailerons and elevator moving in the correct sense; rudder verified by visual or tactile check).
• Flight instruments set: altimeter to current setting (field elevation should be within ±75 ft per AIM guidance), heading indicator aligned with magnetic compass, attitude indicator erect, turn coordinator ball centered.
• Fuel selector on the proper tank (often both for high-wing trainers, or the fullest tank).
• Mixture rich (lean for high density altitude per POH).
• Trim set for takeoff.
• Engine instruments in the green; oil temperature warm enough for run-up (often a minimum of ~100°F or as specified).

Engine Run-Up

With the airplane secure, advance the throttle smoothly to the manufacturer-specified run-up RPM (commonly 1,700–2,000 RPM in light singles, e.g., 1,800 RPM in a Cessna 172).

1. Magneto check. Switch from BOTH to RIGHT, note the RPM drop, return to BOTH and allow RPM to stabilize, then switch to LEFT and note the drop. Typical limits:
   • Maximum drop on either magneto: 125–175 RPM (POH-specific).
   • Maximum difference between the two magnetos: about 50 RPM.
   • No drop at all on a magneto suggests a hot/grounded P-lead — a hazard during prop handling — and is a discrepancy. A rough mag often clears with leaning and a brief power increase to burn off fouled plugs; if the drop remains out of limits, return for maintenance.
2. Carburetor heat check (carbureted engines). Apply carb heat at run-up RPM and verify a small RPM drop (typically 50–100 RPM), confirming the system is delivering hot, unfiltered air. Return to cold.
3. Propeller governor check (constant-speed props). Cycle the prop control from high RPM to low RPM and back, observing a smooth RPM and oil-pressure response. In cold weather, cycle two or three times to circulate warm oil through the hub.
4. Engine instrument scan. Verify oil pressure and temperature, cylinder head temperature, ammeter/loadmeter, vacuum/suction, and fuel pressure are all within limits.
5. Idle check. Reduce throttle to idle and confirm the engine runs smoothly at the POH idle RPM (often 600–700 RPM). A rough idle can indicate fouled plugs, a lean mixture at idle, or induction leaks.

Before-Takeoff Checklist (CIGAR-TIP / final flow)

After the run-up, complete the before-takeoff items. A common memory aid is CIGAR-TIP:

• Controls — free and correct
• Instruments — set, in the green
• Gas — proper tank, quantity, fuel pump as required
• Attitude — trim set, flaps set per POH
• Run-up — completed
• Transponder — ALT, code set
• Interiors/exteriors — doors, windows, seatbelts, lights
• Props — set; mixture rich

Set radios and navigation, brief the takeoff (planned rotation speed, initial climb, abort criteria, emergency action if engine fails before/after rotation), and review departure instructions or the runway-heading-then-on-course expectation if VFR.

Takeoff Briefing (Memorized Action Plan)

The AFH emphasizes that every takeoff should be preceded by a verbal takeoff briefing so the response to an abnormality is reflexive rather than improvised:

• Engine failure on the ground roll: throttle idle, brakes, hold centerline, exit at next available taxiway.
• Engine failure after liftoff with insufficient runway/altitude: pitch for best glide, land essentially straight ahead within ±30° of runway heading; do not attempt a turnback (the impossible turn) below the altitude established for the airplane.
• Engine failure with adequate altitude: best glide, identify a landing site, troubleshoot, declare an emergency.

Only after the run-up, before-takeoff checklist, and briefing are complete should the pilot announce intentions, scan for traffic on final, and taxi onto the runway.