DXB Posted December 1, 2019 Author Report Posted December 1, 2019 30 minutes ago, carusoam said: 6) There is one oddity in the EGT graph... each time something fails to operate.... the EGT spikes downwards... this is not what is expected of a two mag system running on one may... 10) something seems to have changed on cylinder one, stronger than what is happening on the other three... 11) or what ever happened to the mag is affecting cylinder one more strongly? 12) I grabbed a close-up of the run-up of the flight Dev shared... note where I left the data mark... cyl #1 looks like it's slightly misbehaving up to this point... But really goes its own way after this point... have a look... 13) I am baffled by the periodic downward spikes in the EGT... and how Cyl#1 stands out more than the rest... 14) The second mag peak, is clearly showing that mag misbehaving... most on cylinder #1... 16) What plugs are in there? Anthony it's the left mag that's bad (proven after landing). My mag check order on runup is LEFT-BOTH-RIGHT-BOTH. So it is the RIGHT #1(bottom plug) that has a hotter EGT at runup. It ran smooth at runup on both sides before the flight despite that observation. Cyl #1 has run hotter EGTs typically ever since that cylinder got changed to a new one 2 years ago. I think it is a red herring. I changed the plugs to new 50 hours ago (BYL-nosed Tempests). Changing to new plugs did not alter this behavior for #1. I interpret those downward spikes in the EGT trace as briefly getting ignition on both plugs, not the mag cutting out. Note the blazing hot EGT baseline above those downward spikes (gets up to 1700 for #1) - that's clearly ignition happening on just the right mag. 1
N201MKTurbo Posted December 1, 2019 Report Posted December 1, 2019 FWIW The condenser's action happens on every spark. The repetition rate doesn't have anything to do with it. The condenser forms an LC tank circuit with the primary winding. When the points open the magnetic field collapses inducing energy into the primary winding this energy is transferred to the condenser then back to the coil in a decaying oscillation. This decaying AC current in the primary induces the high voltage in the secondary winding. Without the condenser the DI/DT of the collapsing field drives the primary circuit voltage to infinity until it gets high enough to ionize the air in the point gap causing an arc. All the energy is dissipated across the impedance of the arc. Very little gets transferred to the secondary. 1 1
Yetti Posted December 1, 2019 Report Posted December 1, 2019 19 minutes ago, N201MKTurbo said: FWIW The condenser's action happens on every spark. The repetition rate doesn't have anything to do with it. The condenser forms an LC tank circuit with the primary winding. When the points open the magnetic field collapses inducing energy into the primary winding this energy is transferred to the condenser then back to the coil in a decaying oscillation. This decaying AC current in the primary induces the high voltage in the secondary winding. Without the condenser the DI/DT of the collapsing field drives the primary circuit voltage to infinity until it gets high enough to ionize the air in the point gap causing an arc. All the energy is dissipated across the impedance of the arc. Very little gets transferred to the secondary. Ionized the rubber on the coil wire on one of the fire trucks with a Ford 460. The Ford dealer did not feel the click so the wire was partially engaged. So lots of arcing across an air gap. Rubber on the boot was ionized as well.
Yetti Posted December 1, 2019 Report Posted December 1, 2019 1 hour ago, N201MKTurbo said: You may also have a bad condenser. That would be my second vote.
N201MKTurbo Posted December 1, 2019 Report Posted December 1, 2019 31 minutes ago, Yetti said: Ionized the rubber on the coil wire on one of the fire trucks with a Ford 460. The Ford dealer did not feel the click so the wire was partially engaged. So lots of arcing across an air gap. Rubber on the boot was ionized as well. Kind of a different deal. Having a gap in the secondary splits the energy between the spark plug and the gap. You will get 8 times as many arc events across the coil wire gap as any one spark plug. The arc generates a lot of heat and ozone, both of which are very bad for the rubber.
carusoam Posted December 1, 2019 Report Posted December 1, 2019 Dev is based at NE Philly... Alan is based at KVAY south Jersey... not too far away by Mooney... Best regards, -a-
DXB Posted December 16, 2019 Author Report Posted December 16, 2019 Wrap up to this story - I got the Surefly installed, and the bird is back home two weeks after I had to fly home commercial from Myrtle Beach. My first true breakdown experience, and a costly PITA all around. Thanks to @N201MKTurbo, @Andy95W, @carusoam, @Yetti and others for their insights. Chuck at Savvy Breakdown assistance (a free benefit of Global Insurance for me) was also hugely helpful in finding me maintenance help on a weekend away from home at a field with no shop. Savvy's subsequent management of the repair itself was not very impactful in my case but might have helped had it been unclear what had gone wrong or if the shop hadn't been communicative and responsive with me. In this regard, I think Deric at Executive HeliJet at KMYR did a good job and did not overcharge, particularly considering he was traveling to the ramp at a field 20 miles away to do the work. Also Surefly's customer service was great. Demand for these units is intense, and I had a SIM4N on backorder. They sent out a unit from their AOG stash to help me out. I will give a pirep on the Surefly in a separate thread, since lots of folks are considering this install.... 3
chriscalandro Posted December 16, 2019 Report Posted December 16, 2019 Let me know how you like that Surefly. I'm planning on going that route next time I need mag work.
carusoam Posted December 28, 2019 Report Posted December 28, 2019 Great follow up, Dev! Thanks for sharing the details... Best regards, -a-
Recommended Posts