However, again, this was an unusual morning. Fortunately the startled prospective buyer did not get hit by the spinning prop.
#Master reboot flying full
The RON bag, extracted in darkness by the ferry pilot not only had bumped the mixture control, but also the throttle, so the aircraft engine faithfully roared to full power. Again, this morning, things were not normal. Normally this might have resulted in the engine firing, or even starting and idling. However, if the mixture idle-cutoff were in the cutoff position, there would not be fuel available in the carburetor to ignite, except for some reason (such as the ferry pilot extracting his RON bag in the dark) the mixture was nearly full rich. This was likely not noticed because not everyone does a magneto "ground" check in the off position during their run-up process. Normally that would not have been a problem, except the magneto switch in the aircraft was "open" in the off position, which meant that both magnetos were hot. Eventually something possessed him to rotate the prop through manually. The buyer arrived at the strip early the next morning, and while waiting for the ferry pilot, poked around the locked plane. A ferry pilot brought a plane to town at night, tied it down at the rural airport, and was to meet the prospective buyer the next morning. To relate a story which happened at a local airport several years ago. There is significant history that broken or intermittent magneto switches, broken or intermittent wires and other causes are responsible for unintended engine starts or undesired engine firings. Furthermore, magnetos, while switchable, are normally "grounded" to disable them. They have the advantage of being effective starting aids. Many aircraft engines also have "impulse" magnetos, which are spring loaded, and trigger on a very low rotational velocity. Magnetos are effective at creating energy even at low rotational velocities. The most significant source of ignition in most aircraft gasoline engines is the magnetos which are used to energize the spark plugs. Removing fuel eliminates these sources of ignition from causing continued rotation of the engine. Hot carbon deposits, hot spark plugs, nicks in pistons are all sources of continued ignition when trying to shut down an engine.
the risk of a partially rotating prop is non-zero. Since frequently props are moved to place cowl plugs, attach tow bars, etc. Oxygen is ubiquitous and is not practical to eliminate from the engine environment.Ĭompression can happen when someone intentionally or unintentionally moves the prop, which coupled to the crankshaft may cause a cylinder to go through a compression stroke. So shutting off the fuel is one way to prevent accidental "start" if even for one stroke. If the engine is starved of fuel, accidental combustion (and an accidental spinning prop) will not happen. Combustion in a gasoline internal combustion engine for most aircraft, requires four things: fuel, oxygen, compression and ignition.
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