Now that the pre-flight checks have been done and your seat is adjusted properly, the next step is to start the engine. There are several cockpit controls that are used for starting the engine which all are adjusted depending on various scenarios and circumstances.
The most common training airplane is generally the Cessna 172. There are 5 main engine controls for the Cessna 172 as follows:
To set the throttle for engine start, find the 1/4″ mark on the throttle and align your finger with that marking. Push the throttle in until your finger reaches the stopping point.
The mixture control knob is next to the throttle control and has a red handle. This control changes the fuel to air mixture ratio. Pushing in increased the amount of fuel in the mixture (rich) and pulling back increases the amount of air (lean).
Pushing all the way forward is the “full Rich” position.
Pulling all the way back is the idle cutoff position “lean” (shut off engine) .
There is a lock button at the end which is used to prevent accidental movement and depressed for quick or large adjustments.
There is a function called “vernier adjustment” in which fine tunings can be made. Clockwise results in forward movement and counterclockwise a fine tuning on the pulling function. Another way to think of it is clockwise is fine tuning more rich & counterclockwise fine tuning the lean.
For startup on the Cessna 172, it should be set to fully pushed forward in the “full rich” position before start.
Pull back around 1″ for a general lean mixture.
The master switch turns the power on and off from the main battery and is located on the left side of the instrument panel (red switch). This doesn’t control the engine ignition.
Ignition switch and key
Similar to the ignition switch of a car, this switch is positioned on the instrument panel at the lower left and contains a 5 position switch. The positions are as follows starting with the left most position:
- R (magnetos-prop)
- L (magnetos-prop)
- Both (magnetos-prop)
For engine start, the position should be on the start position and once the engine starts, moved to the “both” position.
Oil pressure gauge
The oil pressure gauge is located in the engine instruments display panel and will normally show pressure around 30 to 60 seconds after the engine starts.
For reference, the oil pressure will increase more quickly after start if the oil is warm and will take longer if the oil is cold.
The engine should be shut off if the oil pressure gauge shows no pressure to avoid any potential engine damage.
Step-By-Step Procedure for starting the engine
Below is a step be step procedure for getting the engine started. This is in reference to the Cessna 172. Think of this as a checklist for starting the engine.
- Parking Brake – Once your seat is adjusted and you are all buckled in, the next step is to ensure that the parking brake is set. This should have already been set but now it is a good time to double check now before starting the engine.
- Lights – Turn on the strobes and/or beacon which will signal any others that you will be starting the engine and that the prop will be turning soon.
- Safety – Visually scan the area around the aircraft to ensure the area is clear for prop movement. Loudly yell out of the window, the words “Clear Prop” to alert anyone nearby and to give them a chance to respond. This should be done with the headset off to ensure you can hear a response.
- Start the engine
- Set the throttle to idle at 1000 RPM (as indicated on the tachometer) and ensure that the oil pressure is safely indicating in the green area.
Engine Starting Problems
There are many reasons why the engine won’t start. From complicated mechanical failures to a dead battery, sometimes problems happen.
If the battery is dead, then engine will not start. Often times, a dead battery could be due to the master switch being left on which has drained the battery. Recharging the battery in this scenario should solve the problem. If the battery is older or in bad condition, a replacement may be necessary, especially if the battery will not hold a charge. If the alternator is not functioning properly, the battery will not be able to charge which could also be a cause of a dead battery. In this case, the alternator would need to be repaired or replaced along with charging or replacing the battery.
* Starting the engine by hand-turning the prop should not be attempted.