Crankshaft Seal Blowout In Flight and Emergency Landing

Mike S said:

Thinking about this, the coke buildup itself may well be a limiting factor----------it takes some oil to be baked into the coke, right??

As the hole closes up from the coke, what happens to the available vacuum, and the flow of oil???

I wonder if there is a spot where the buildup will limit the oil flow to where there will be no more buildup----------yet there will still be a small opening???

Can the coke actually close off the hole entirely ????

Now back to your regular programing.

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Interesting postulation. How much oil actually goes out that tube, since it is the air-side outlet of the air/oil separator? Certainly there is some gaseous, and perhaps some liquid oil or contaminants, that pass that way, and could be subject to attaching to the tap wall and coking. Hopefully most of the liquid goes out via the oil-side exit of the separator, at least while the engine is running. After shutdown, perhaps a little oil drips down the tube towards the CVV, and also adds material that may make it to the coking site. If I'm in sync with you Mike, you're thinking that the suction through the CVV might limit full closure of the tap, right? Leads back to the question, how small a hole leads to enough case pressure to blow the seal?

DanH said:

Reality says the informed will make their own choice.

The real issue involves getting the word out about coking the exhaust tap, so the uninformed will not descend from the heavens in a shower of oil.

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Well put. Its a potential HP mod for me, and, as with any other mod I make, I watch its impact on the operation of the engine or airframe, and weigh its effectiveness. Its not an "at any cost" program either, so eyes are wide open on every mod, this included. If this adds little value, its gone. If it adds value, and safely (given maintenance and a bypass/relief), it stays. Just one person's (hopefully informed, certainly attentive to input) choice.

BillL said:

Really good question! It also probably depends on how much blow by there is. Also, as rings rotate etc, does the blow-by change, wander with time? Probably.

Bob, As you check the crankcase pressure would it be possible to install an orifice of a couple of sizes to see how the pressure changes? I bet that is already in your test plan

I gotta get finished and flying so I can provide some data too.

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Tell me more Bill…the why, how, what of it. Certainly game!

This is getting mucho air time in many circles. Talked to another VAF poster today by phone, who has an ASA AOS, but a DIY CVV tap, made from Moroso and other parts. He's done some testing to determine optimum depth and angle of the tap, in terms of max vacuum generated. Has piqued my interest! He also uses O2 sensors in ports similar to his CVV tap ports (all are screw-in).

OK, now there's a tee-up for a new thread, eh!

Cheers,
Bob

akarmy said:

Ok, ya it's twice the cost of the other separator, but it's larger and works great, and in the grand scheme of things its not that much money.

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Andy: The Raven system looks like a catch bottle / vs. separator. Is that right? If so, how often and how do you drain the oil out of it? thx. doug

pressure

I have the ASA system on my plane and its working as advertised I will be adding the back up value or doing the slit in the rubber tube as Tom suggest
my question is how much pressure has to build up to blow out the front seal?
I want to make sure if I do the slit in the tube it would open up to relive the pressure.
Tim

I wonder if the manifold pressure sensor used by Dynon for the MAP engine gauge function would work for monitoring crankcase pressure. The Skyview system is easy to reconfigure and perhaps add crankcase pressure to the engine monitor...

Randall

One of my earliest flights (at the age of 12 to 14) had a similar outcome, but we didn't have Skyview back in the 50s. The pilot had me fly the plane, an Ercoupe, to short final while he lowered the windows, stood up, and cleaned the windscreen with a rag. He then landed with no problem, and no engine damage. We also were about five minutes out. Scary, even to someone who didn't know much about flying.

Congrats on handling this in such a professional manner. Interesting to see how well the Skyview helps in such a situation. I hadn't thought of that.

Bob

tclaire said:

I have the ASA system on my plane and its working as advertised I will be adding the back up value or doing the slit in the rubber tube as Tom suggest

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If you cut a slit in the tube it will negate the case vacuum.

DanH said:

If you cut a slit in the tube it will negate the case vacuum.

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If done correctly it won't. The goal is to not remove any material just slit along the length of the tube. You could even do it on the inside of bend to make double sure it won't be open under atmospheric pressure and negative pressure.

dlomheim said:

Andy: The Raven system looks like a catch bottle / vs. separator. Is that right? If so, how often and how do you drain the oil out of it? thx. doug

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It has a return to the oil sump via a #10 line. It's an inverted catch tank so it has a ball bering that flops over to switch the input and output when negative, but it has a normal breather coming out the side and for all practical purposes functions as a separator as well. I have not had any noticeable oil coming out the vent which is located just above the exhaust pipe like a normal breather.

Seal

Anyone have any idea what kind of pressure would happen to be in the case for the front seal to blow out seems like it would be pretty high pressured to blow the seal out would think it would blow out any Coke build up before the seal

Pictures of Airwolf Installation

As was asked by a few of you, here are some pictures of my Airwolf Separator installation on my RV-10.



This is a view of it mounted on the firewall. Right behind the #5 cylinder.


Here is the inlet from the right rear baffle. This is what is recommended if you don't have a vacuum pump outlet. Who has a vacuum pump anymore?



This is the backside of the rear baffle showing the connection to the separator and the drain hose into the accessory case.



This is the top showing the tube from the engine breather outlet


This is the outlet, which is about 6" above the exit floor.

Hope this helps.

Vic