Stopping & Restarting an AeroVee

[mike.smith]

I have a Sonex and not a Xenos, but I figured the engine-optional crowd would be the best place to ask about shutting down and restarting the AeroVee in the air. I do a lot of aerobatics, and while I've never had the engine quit (I keep to the usual positive G maneuvers), it's certainly a possibility if I mess up a little. So are there any things to note about restarting in the air? Just shut down like on the ground, and restart just like on the ground?

[Rynoth]

Good question, and I bet this is the best forum to ask as Xenos folks would do it more often.

I have performed 1 intentional shutdown - restart of my Aerovee in my Waiex by pulling the mixture. I recorded the event here:

https://youtu.be/CmnEc_UprfM?t=102

The main thing to note would probably be to avoid flooding the engine. I pushed the mixture from cutoff to full and immediately engaged the starter (just like a normal startup.) If the mixture was rich for an extended period I might suggest turning it over a few seconds with cutoff mixture before going rich.

[MichaelFarley56]

I never shut the AeroVee down in flight, but I did have several occasions where the engine would die on me on the landing roll out as I cleared the runway. My fault normally as I had the idle set too low and it simply died as the RPMs dropped too low.

I did discover however that the most important thing to do in that situation was to immediately pull the mixture to idle-cutoff right away so the engine didn't flood out. If I lost the engine and pulled the mixture quick it would start right back up, but if I didn't pull the mixture it would flood and take longer to restart.

If you're up flying and for whatever reason you loose the engine I would immediately pull the mixture to idle cutoff, hit the starter button and push the mixture back in as the engine spins. I bet it will restart right away. That way the engine doesn't flood.

My two cents of course!

[GraemeSmith]

I once did some testing of "air starting" a Continental while over a deserted airport on a dead quiet day. With the plane in level slow flight (flaps up) I pulled the mixture to stop the engine. Put the mixture back where it was and dived aggressively to spin the prop and restart the engine. Starting at 12,000ft DA It only used 500ft of dive to restart. But the lower I got (using a safety floor of 3,000ft) the more altitude was needed to restart the engine. In the end it was taking 1,500ft to get a start.

I don't think this was cooling but possibly the increasing air pressure as the plane got lower. As the air got thicker lower down, the jugs were taking more effort to turn them over as they were filled with a harder to compress "thicker" mixture. Well that was my thinking / reasoning. But that was a Marvel-Schebler carb. And I'm not sure our smaller Prince or Sensenich diameter props would have the grunt at lower RPM to get an air start. Which is not what you were asking anyway!

So to Mike Farley's:

"would immediately pull the mixture to idle cutoff, hit the starter button and push the mixture back in as the engine spins. I bet it will restart right away. That way the engine doesn't flood."

I'm pretty sure this is good advice. I sort backed into this solution once when I was too rich pulling a loop and the engine riched more on the pull and stopped. Realizing what had probably happened I still had the energy to bunt the plane level and as I hit the starter I was pulling the mixture out to lean the carb and as the engine caught - pushed the mixture in again to keep it running.

--

So add the two together. I suspect that the restart spot for the carb will vary with the Density Altitude the plane is flying at - but whether it makes an appreciable difference that one could calibrate - not sure. Perhaps the action of just steadily pushing the mixture in as you crank would find the correct spot at some point.

[racaldwell]

Mike,

If the prop is windmilling, do not hit the starter.

I also did an air start once on my One Design with an IO-360 angle valve engine. With the prop stopped (wood Performance Prop 3 blade) I dived vertical downline and right at Vne the prop suddenly spun up and started instantly. That took a few thousand feet to do. So I knew never to count on restarting with an air start.

Rick Caldwell
Xenos 0057

[Area 51%]

The local Xenos driver here in Crystal River had his engine (Aerovee) fail to restart last week but was lucky enough to make the airport.

Investigation showed the air filter saturated with gas and fuel was pooled in the bottom of the filter assembly up to the edge of the sealing material. There apparently was some failure of the mixture cut-off. Whether it was mechanical or related to soft grey tissue is unknown.

As a precaution against such a scenario, I drilled a small drain hole in the bottom plate before I ever started the engine.

[mike.smith]

Thanks for the input. Regarding the windmilling prop, I believe I've read in the forum previously that the AeroVee really doesn't windmill, or that you'd have to dive pretty hard to get enough speed for it to do that. Anyone have that experience?

[Rynoth]

Thanks for the input. Regarding the windmilling prop, I believe I've read in the forum previously that the AeroVee really doesn't windmill, or that you'd have to dive pretty hard to get enough speed for it to do that. Anyone have that experience?

In response, I'll again reference my video clip:

https://youtu.be/CmnEc_UprfM?t=102

My aerovee did not windmill below 80kts. Actual airspeed required to windmill must be higher in my setup, but I did not test above 80kt.

[bvolcko38]

I got my self launch endorsement in a Shiebe motor glider with a limbach engine, basically a certified VW. The instructor had me do an air start from about 4000'. It started windmilling on its own but I felt we were nearly vertical. My guess it that the Xenos with Aerovee will be similar. I will find out soon. Still in phase 1 testing.

[mike.smith]

Thanks for the input. Regarding the windmilling prop, I believe I've read in the forum previously that the AeroVee really doesn't windmill, or that you'd have to dive pretty hard to get enough speed for it to do that. Anyone have that experience?

In response, I'll again reference my video clip:

https://youtu.be/CmnEc_UprfM?t=102

My aerovee did not windmill below 80kts. Actual airspeed required to windmill must be higher in my setup, but I did not test above 80kt.

That backs up what I've heard previously. Funny that a VW is considered a "loose" engine, but it seems tight when it comes to turning the prop in the wind. So sounds like the best advice is to not count on windmilling the prop on a VW.