The Irish Aviation Authority has published a Safety Leaflet addressing the dangers and precautions to be taken when operating close to aircraft propellers. The leaflet can be read here.
New and student pilots might find it useful for me to delve into the dangers a little bit more. The points in the safety leaflet are well made, but all pilots should have a thorough understanding of how their aircraft engine and ignition system work. There are several popular engine manufacturers, and they all have different ignition and electrical systems that will affect how you handle the propeller. However, one rule is always paramount – always treat a propeller and engine as if it’s going to start! Even a kick from one cylinder is enough to move a propeller at such a force to cause serious injury. These rules should always be followed if you need to move an aircraft propeller:
- Never wear loose clothing or accessories (e.g. a lanyard) that could get caught if the propeller moved
- Never place a part of your body in the arc of a propeller
- Always check the ignition is off, battery off, throttle closed and brakes on (or chocks in)
- Always turn the propeller in the normal direction of travel unless specifically permitted otherwise in the flight manual/pilot operating handbook (POH)
- Always follow the specific guidance in the aircraft POH or maintenance manual
Hand Starting
Many older aircraft are not fitted with electrical systems and therefore need to be hand started by rotating the propeller with the ignition on so that the engine starts. This practice is safe once appropriate precautions are taken and it is completed by a suitably qualified individual. You should never attempt to hand start an engine unless you have been specifically trained to do so. While it may look easy, a thorough understanding of the risks and appropriate mitigations needs to be taken into account, and this can only be done correctly if you are suitably trained.
Rotating the Propeller
Many engines require that the propeller be rotated prior to engine start, e.g. radial engines, Gipsy Major, Rotax 912, etc. Always follow the guidance in the POH or engine operators’ manual when completing this task. Understanding the ignition system is very important when doing this. e.g. a broken P-lead on a magneto will make that magneto live, and rotating the propeller could cause the magneto to fire, causing the propeller to kick or the engine to start. By comparison, the CDI Modules fitted to a Rotax 912 tend to be much more reliable as they have no moving parts. However, the same precautions should be taken.
Manoeuvring Your Aircraft by Hand
There’s a wide range of GA aircraft, and each manufacturer will have a preference for how their aircraft should be moved on the ground by hand. Tow bars can be useful but present their own set of threats if you forget to disconnect it (see here). It’s usually impractical to move tailwheel aircraft by using the propeller due to the geometry involved. Some POHs do permit the aircraft to be pushed or pulled by the propeller, but usually from the root and never the spinner. Moving an aircraft with a variable pitch propeller using the propeller is not recommended. In any case, always reference the relevant POH for the manufacturer’s recommended procedure for manoeuvring your aircraft by hand.
As we approach winter and flying is likely to wind down a little, next time your flight is cancelled due to weather, why not take a few minutes to sit down and read up about the ignition system and propeller safety for your specific aircraft? You’ll find that information in your POH and the relevant engine operator’s manual. Just to highlight the dangers, here are a few videos that demonstrate some near misses caught on camera!
