REFLECTOR: Hot Starts & Mag Cooling

[Jones Nick]

The 500 hour mag check/rebuild is a recommendation from Slick and TCM. Most experience shows trouble starting approaching the 500 hour mark.

Best regards,
Nick

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On Behalf Of Fred Anderka
Sent: Tuesday, August 16, 2011 4:30 PM
To: reflector at tvbf.org
Subject: REFLECTOR: Hot Starts & Mag Cooling


Just having returned from Tucson and Boise where the temperatures were in the 100's I have not had any problems starting a hot engine in those temperatures.



One of the problems that you can hear developing while refueling is the fuel boiling out of the injector lines (hissing noises) leaving an empty injection system if you are stopped for more than 15 minutes.



My procedure for the IO-550N is:

Mixture Full rich.

Prime on HIGH for 1-3 seconds, you can hear the pump sound change as it starts to get some back pressure.  Switch to LOW, leave on.

Throttle - Full in.

START, it should catch within a second, if not, prime on high for an additional second.  Be prepared to retard the throttle immediately, with the MT prop it tends to rev. VERRY quickly.

Leave the pump on LOW until ready to take off.



Have never flooded the engine with this procedure.  Also with the engine this hot any excess fuel evaporates almost immediately and is the reason for the full throttle start.





While the mags on the IO-550N are under the shroud they get lots of cooling during flight, but, after landing and parking I believe the mags must get VERRY hot, you can see lots of heat coming out of the two NACAS due to convection.



On trying to leave Victoria last week I found my left mag was dead.  After removal and some diagnostic work I found that the distributor shaft bushing was worn and quite sloppy and the distributor finger must have snagged one of the spark posts and rotated about 60° on the Nylon gear.  Although there was a healthy spark, when in the #1 position (red tooth up) it was firing #5 plug.



After an overnight mag delivery and lots of $ & sweat the engine ran as before a few hours later.  Although I noticed that there was a greater RPM drop on the RIGHT mag now.  As soon as I get the original mag rebuilt, the right mag is coming off for a check.  The two mags on the IO-550N are identical and can be interchanged.  Although the factory engine only has 497 hrs. on it, the distributor shaft bushing wear seems way too excessive.  My AMO tells me that a 500 hr. check is mandatory on a certified aircraft, sounds like a good idea for all.



Fred Anderka

C-GHOL, XL RG
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