Failed experiment with my alternate air solution

[koda2]

Not sure if I showed this before, but just another reason to experiment with Vans design.

This is a view from the floor looking up at the carb inlet.
A friend was flying his RV on a cross country flight when the engine coughed, quit momentarily and then resumed flying, but rough.
On return home we started trouble shooting.
One cylinder and exhaust valve was damaged for reasons unknown.

The filtered air box was removed and the alternate air assembly had failed and parts were missing.
The picture shows part of a rivet/washer assembly that stuck in the carb inlet.
The remaining parts that were ingested went through the engine.
Fortunately the old Lycoming just spit them out and kept flying.



Dave A.

[gerard_opio]

Does anyone take a look at the Robinson R22 alternate air automatic valve?
It is based on a system with four springs, and mechanics guys here told me they never found any issue with that. It is certified also ...
It's look like it can installed on the Van's air box.

Any comments?

Gerard

[Mark Dickens]

Is there a link? I'd be interested in learning more

[gerard_opio]

Originally Posted by Mark Dickens

Is there a link? I'd be interested in learning more

You may read page 71.4 figure 71.5 in the "illustrated parts catalog" for R22, chapter 71 POWERPLANT

http://www.robinsonhelicopter.com/r22_ipc.html

Gerard

[Mark Dickens]

Originally Posted by gerard_opio

You may read page 71.4 figure 71.5 in the "illustrated parts catalog" for R22, chapter 71 POWERPLANT

http://www.robinsonhelicopter.com/r22_ipc.html

Gerard

Thanks. Nice to see a new design and it certainly looks reliable. Those springs must not be too stiff, especially considering there are four of them

[Jrskygod]

That sure is a lot of pieces to get loose and be ingested. Must work tho. I sure don't hear of Robinsons falling out of the sky for that reason tho.

[gerard_opio]

After a new look today at the R22 and discussing with the maintenance guy,
I just ordered the parts from Robinson to install on the FAB.
The R22 engine is Lyco 320 derated to 140HP so if it works for it I hope the springs will be good enough for my Lyco IO-320.
I soon as the engine will be running (in a couple of weeks ... ) I will post an update.

Gerard

[Steve Melton]

I would never put all those pieces in there.

[Mark Dickens]

I wouldn't have a problem with the design although I'd use a castle nut and cotter pin in a drilled bolt instead of the lock nut.

[cajunwings]

Haven't gotten to this yet but I will graft the alternate air door from a Twin Comanche induction elbow to the bottom of the Vans fab. The spring rate should be correct for this application since my IO-320 came from same Twin Comanche. Have not decided whether to just leave it fully automatic or add a manual override. It's fairly simple compared to the R-22 setup. Many of the Piper Cherokee models have something similar in the lid of the airfilter housing.

Don Broussard

RV 9 Rebuild in Progress