Live mag check before shutdown

[kiwiblue]

Originally Posted by Jabawocky

Keeps your mind active when changing a/c types!

Absolutely Jabawocky! Showing my lack of familiarity with 'recent' developments in the smaller end of the market Ever had an issue with a prop firing when pulled through? Are there any particular procedures you observe due the fact there is still fuel present in the engine?

R J Kinloch: Luck indeed!!! What was the underlying cause? A hot mag? Fuel igniting on a hot-spot?

[Jabawocky]

Kiwiblue

This is turning into a good informative thread.

To answer your question, for the newer small end of town, there is no fear of a prop start on a Jabiru, it can't be started under 300RPM and unless you are superman, you can not achieve that by hand starting. This is a factory known fact not just my opinion. They are that way by design. They do not use the same kind of sprung magneto system as say a Lycoming.

As for Rotax, I do not believe they can be hand started in the 4 cycle engines, but that is not fact, just an opinion. The 2 stroke versions I think can be hand started. Maybe a Rotax guru can advise here.

As for policy around props, even the known to be unstartable by hand......Treat them as live. This is a habbit for all machines, but I must say its easy to become complacent.

J

[gassed budgie]

Should you inadvertently rotate the switch to 'off' with say 1800 RPM on, then back to on, you run the risk of damaging the exhaust system at a minimum. Should this happen, leave the switch off, allow the engine to shut-down completely then re-start normally. You will have done little more than raise your own blood-pressure and given yourself a good reminder to pay more attention next time.

Well done Kiwi. I haven't heard anyone else suggest this in a long, long time. If you happen to inadvertantly select magnetos 'off' when checking the mags, you run the real risk of stripping the teeth off the main gear drive in the magneto when the engine all of a sudden ramps up again. I've seen it done.



This is what the end result looks like. You ain't going anywhere anytime soon. I might point out that Bendix mags are more likely to strip the teeth off the gear than Slick magnetos.
As Kiwi has suggested, sight tight, relax, pull the mixture and then crank it again. No harm done.

[TLAW]

Gassed Budgie,
Yikes! Very informative photo.
I admit I once accidently selected 'OFF' during a run-up, realised what I had done, then quickly selected BOTH again. Won't do that again!
The instructor drolly asked if that was my normal procedure for checking mag drop.

[ItsOkMagsOff]

Mags off

Keys on dash where i can seem them please...

[bushy]

Nylon gears

Those gears are made of nylon and are definitely a weak point, and a good reason to use diesels which do not need mags. (if you could ever afford to buy one) The first engine failure I ever experienced was caused by a magneto gear failure.
Bendix mags need regular inspections and the nylon gears have a limited life. I once bought an aeroplane from an airline captain, who had had to overhaul the engine when an oil hose burst and dumped all his oil overboard.(I wonder why)
Within a few months we had a forced landing because the nylon gears in the mags were old and brittle, and one lost some teeth out in the middle of nowhere. We also discovered some necessary propellor work he had not told us about.
I think slick mags are better because you replace them instead of overhauling them, so you always have fairly new mags.
Magnetos need lots of attention, and they are critical.

[Sunfish]

I suspect that the reason the gears are nylon is so that they WILL break if the Magneto jams up. That way at least you should still have one functioning Magneto.

[Brian Abraham]

you should still have one functioning Magneto

Not necessarily so as some engines have the mags piggy backed on the same drive shaft. Whether they are driven by a nylon gear or not you would need to know your specific engine. Just the same, have had engine problems because a metal shaft stripped its gear teeth.

[kiwiblue]

whilst on all things mags...

A bit of thread-drift, but such is life

Should you ever find yourself in the unfortunate position of having to apply the Armstrong starter to your aircraft, a couple of mag-related things that may be useful...

• know which (if any) of your mags is the impulse mag -usually the left, but be sure. More likely to get a nice clean start off that one.
• know what type of mags you have installed... a shower-of-sparks mag will require the starter switch be engaged during the Armstrong -or there will be no shower-of-sparks... No spark = no fire By contrast, an impulse mag won't give a toss where the starter switch is.

Anyone have others they can add???

[Lefthanded_Rock_Thrower]

If you are trying to hand start a Lycoming after a failed attempt with the starter motor, the starter shaft will not disengage ( cog wind back into the starter housing ) until the engine has operated above 500 odd RPM ( after hand starting ).

You can not hand start a Shower of sparks ( starter vibrator ) type engine without both battery power and the starter button being pressed.

Continential are quite suseptible to cracked cylinders, with oil consumption above half a litre per hour or manifold pressure above 15 inches at 1000 RPM ( at idle, warm ) that would warrant further investigation, may also be running a little rich at idle.

Flying a PT6 with the condition lever in "Low Idle" does not save fuel, you are an idiot for thinking so.

Multi engine aircraft with engine driven hydraulic systems, when operating on one engine, will generally take longer to cycle the landing gear.

High oil level will generally cause the oil temp to be high inflight.

Engines do not operate very well with air in the tanks.

If you abort a start in a turbine, let it sit for a couple of minutes to allow the oil levels within the engine to equalise ( PT6 ).

A warning light in flight, actually definately means the light globe is working.