How to do a P-Lead check

[SkyHog]

So I've decided its time to start doing P-Lead checks before shutdown. I used to do them when I first started flying and then got lazy I suppose.

I seem to remember doing it the same way as the runup mag check, but I recently heard that you should turn the key to "off" momentarily to check for a stutter. Wouldn't that cause a backfire?

Any tips on this?

 

[ScottM]

Wouldn't that cause a backfire?

Any tips on this?

Sometimes and is the reason I stopped doing them at every shutdown. I too am lookig forward to eharing from people on this. It seems that if you go from both to L back and then to R if you are seeing the drop in RPM that you P-leads are functional. Or do you sometimes actually just shutdown by grounding the mags instead of leaning the mixture?

 

[Henning]

So I've decided its time to start doing P-Lead checks before shutdown. I used to do them when I first started flying and then got lazy I suppose.

I seem to remember doing it the same way as the runup mag check, but I recently heard that you should turn the key to "off" momentarily to check for a stutter. Wouldn't that cause a backfire?

Any tips on this?

Just off idle, mixture very lean near ICO, click to "Off" for just a moment, I've never had a backfire.

 

[Let'sgoflying!]

Turn it off with the switch upon shutdown (it should quit), then full lean and don't touch the prop from that point forward. (How can you be sure if its really quitting unless it actually does, when using the off-on-lean technique?)

 

[poadeleted20]

Just off idle, mixture very lean near ICO, click to "Off" for just a moment, I've never had a backfire.

That's the ticket. Shutting down with the mag key rather than the mixture is not a good idea, as that leaves the engine more prone to accidental startup.

 

[Let'sgoflying!]

That's the ticket. Shutting down with the mag key rather than the mixture is not a good idea, as that leaves the engine more prone to accidental startup.

Startup? You just proved the mag switch works. Yes; dieselling, I suppose.

In my situation I can do the test, push it into the hangar and no one else is going to have access to it. I suppose an outdoor tiedown situation or rental would be different. I just don't think the test is complete til.... its done! ("Well, it sounded like it was quitting to me. Sorry about your head")

(my reference is the AD that applies to my Bendix switch, 76 07 12. It says, "1. b) With the engine at normal idle, rotate the switch lever or key through the 'off' detent, to the extreme limits of its travel, in the 'off' direction.
c) If the engine stops firing this indicates and airworthy switch.
d) If the engine continues to run with the switch in the extreme 'off' direction, indicating a malfunctioning switch, prior to the next flight....."
No where in the remainder of the AD does it say to turn the switch back to the on position.

 

[gismo]

That's the ticket. Shutting down with the mag key rather than the mixture is not a good idea, as that leaves the engine more prone to accidental startup.

'Zactly. IMO the only time you should shut down with the mag switch is when you are going to start right back up without getting out of the plane. I suppose you could hang a "Hot Prop" warning but that probably means touchnig the prop as well.

Like Henning, at dead idle and leaned I've never had a backfire while turning the mags off and back on quickly. When you do this start with the switch on one mag, usually right (the position closest to off). That way you don't mistake the drop going from two to one for the complete shutoff. If you accidentally kill the engine, just start it back up and then kill with the mixture.