The "pretakeoff check" is the systematic procedure for making a last minute check of the engine, controls, systems, instruments, and radio prior to flight. Normally, it is performed after taxiing to a position near the takeoff end of the runway. Taxiing to that position usually allows sufficient time for the engine to warm up to at least minimum operating temperatures and ensures adequate lubrication of the internal moving parts of the engine before being operated at high power settings.
Some pilots devote too little attention to engine warmup. Most engines require that the oil temperature reach a certain degree before proper operation can be depended upon.
Today's air cooled engines generally are closely cowled and equipped with pressure baffles which direct the flow of air during flight to the engine in sufficient quantities for cooling purposes. On the ground, however, much less air is forced around these baffles and through the cowling, and any prolonged engine operation may cause overheating long before any indication of rising temperature is given by the oil temperature gauge.
Most modern high performance airplane engines are designed to be operated with very short warmup periods, the initial sluggishness of the oil being taken care of in the engine design. When operating these engines, a cylinder head temperature gauge usually is available to determine adequate operating temperatures. In the absence of such instrument, the takeoff may be made when the throttle can be advanced to full power without the engine faltering. Even in extremely cold weather the cylinder heads may overheat before any indication of such a condition shows on the oil temperature gauge. This is more likely to happen in very cold weather when the oil heats slower than in warm weather.
Before starting the pretakeoff check, the airplane should be positioned out of the way of other aircraft. It is recommended that the airplane be headed as nearly as possible into the wind to obtain more accurate operating indications and to minimize engine overheating when the engine is run up. After the airplane is properly positioned for the runup, it should be allowed to roll forward slightly so that the nosewheel or tailwheel will be aligned fore and aft.
During the engine runup the surface under the airplane should be firm, (a smooth turf or paved surface if possible) and free of debris. Otherwise the propeller will pick up pebbles, dirt, mud, sand, or other loose particles and hurl them backward, not only damaging the tail of the airplane, but often inflicting injury to the propeller itself. Inspection of the leading edge of almost any propeller which has been in use for any period of time will show the results of neglecting this precaution.
While performing the engine runup, the pilot must divide attention inside and outside the airplane. If the parking brake slips, or if application of the toe brakes is inadequate for the amount of power applied, the airplane could move forward unnoticed if attention is fixed inside the airplane.
Since each airplane has different features and equipment, the checklist provided by the airplane manufacturer must be used for the before takeoff check. The following, however, are some of the major items that should be checked or set before moving onto the takeoff runway:
1. Set parking brake or hold brake ON.
2. Check wing flaps for operation and set for takeoff.
3. Check flight controls for free and proper operation.
4. Set trim tabs for takeoff.
5. Adjust altimeter to reported altimeter setting or field elevation.
6. Set heading indicator to correspond with compass heading.
7. Set fuel selector to fullest tank.
8. Set propeller control (if equipped) to FULL INCREASE.
9. Set mixture control to RICH.
10. Set carburetor heat control to COLD.
11. Check engine temperature.
12. Adjust throttle to runup RPM.
13. Check each magneto for operation.
14. Set magneto switch to BOTH ON.
15. Check propeller governor (if equipped) for operation.
16. Set propeller control (if equipped) to FULL INCREASE.
17. Check engine instruments for normal indications.
18. Check engine idle speed.
19. Set flight instruments.
20. Check seat locked and seatbelt fastened.
21. Obtain takeoff clearance (if required).
22. Check cabin door locked.
23. Check runway and final approach for aircraft.
24. Check clock for time.
25. Recall takeoff "V speeds" (critical performance speeds).