crank case vent hose

[Bob_Belville]

The Massachusetts A&P re-installing my engine replaced the vent hose with a new one. IO 360 A1A in '66E.

 

When I got the plane home I removed the cowling and had my A&P look over the the installation. Overall he thought it looked like an excellent job with lots of new hoses and everything well routed and secured but had some concern that the end of that vent hose ought to have a whistle valve, I think that's what he called it, an end piece with a side hole that would prevent sealing in the event the end of the hose iced up. He also had some concern about a vacuum being created depending upon how the end of the hose pointed. (the hose extends all the way down to touch, or nearly touch, the trailing edge of the closed cowl flap.

 

Comments?

[MB65E]

I remade my breather hose with a whistle notch and had it extend past the cowl flap with a angle cut in the tube that faces aft. That's just to be safe and comply with the way the factory had it. Real world...Exit air out of the cowl by the end of the breather is probably well above freezing. The engine I would think would pump more air than a little pressure on the end of the hose could ever be. I'd ask the engine shop if they had the old piece.

[Bob_Belville]

I could not find a pic of what I had pre prop strike. Here's how the hose looks now. 

[N601RX]

It should have a tube stuck up in it and bent backwards.  There is a drawing in the parts manual.  If you have bladders there is an AD that requires a hole to be drilled in the pipe section.

 

Here is the drawing from the bladder install manual

[Bob_Belville]

It should have a tube stuck up in it and bent backwards.  There is a drawing in the parts manual.  If you have bladders there is an AD that requires a hole to be drilled in the pipe section.

 

Here is the drawing from the bladder install manual

Thanks. Curious why fuel bladders have anything to do with the crankcase vent?

[Guest]

Bob,

The end of the breather tube us usually made of aluminum with some form of relief hole or whistle slot in it .

While the air exiting the breather is warm when running it is moisture freezing inside the tube on shut down which can freeze solid and blow the front seal out, causing an un scheduled landing.

Clarence

[carusoam]

That is a great piece of sharing!

Best regards,

-a-

[N601RX]

Thanks. Curious why fuel bladders have anything to do with the crankcase vent?

They have nothing to do with it. If you read the comments to the AD a few of the commenters pointed that out, and said that if that was a problem then it should apply to all Mooneys. The FFA basically said they disagreed.

Comment Issue No. 4: Crank Case Vent Hole Is Unrelated to the O&N Bladder Fuel Cells

What is the commenter's concern? The commenter states that, if Mooney airplanes with the bladder fuel cells installed need to have this vent hole drilled in the engine's crankcase breathers, the FAA should then include all piston-powered airplanes.

What is FAA's response to the concern? To this date, FAA has not received data indicating that the condition exists on any other installations other the Mooney airplanes with the O&N fuel cap installation. If our continued evaluation reveals such a condition, we will consider further rulemaking action on other type design aircraft.

We are not changing the final rule AD action based on these comments.

[Bob_Belville]

http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/0/6ff2eeba54075bb686256f65005b79bc/$FILE/042504.pdf

 

A complete non sequitur! I suppose I should not be surprised.

 

Thanks for all the spot on advice. I don't know what happened to the aluminum tubing that I suppose was there but it will be no problem to fashion a new one complete with the whistle hole. 

[Piloto]

Your hose installation is fine. The hose or tube end opening should be pointed backward. This creates vacuum to relieve crankcase pressure. There is no.need for a hole. Oil temp is hot enough for any ice. Any liquid residue will just drain out. No side hole either on later Mooneys

Jose

[M204ever]

There is a need for a hole.

The fwd crankshaft seal blows off in case of  an engine breather line blockage.

It is field experience and it is not smart to ignore.

[Guest]

Your hose installation is fine. The hose or tube end opening should be pointed backward. This creates vacuum to relieve crankcase pressure. There is no.need for a hole. Oil temp is hot enough for any ice. Any liquid residue will just drain out. No side hole either on later Mooneys

Jose

That all may be true, until the liquid water meets sub zero degree air, at which point it turns to ice blocking the vent.

If Mooney did not add holes in later models it is an oversight on their behalf. Likely the same engineer who designed the cabin heater in the Bravo. Works great in southern climates but not so good in the north.

Clarence

[Piloto]

That all may be true, until the liquid water meets sub zero degree air, at which point it turns to ice blocking the vent.

If Mooney did not add holes in later models it is an oversight on their behalf. Likely the same engineer who designed the cabin heater in the Bravo. Works great in southern climates but not so good in the north.

Clarence

But a Goose Bay and going over Greenland to BIRK four times in the winter at over FL180 I have never observed any icing related problems with no side holes breather lines. Neither have seen a Mooney service bulletin or AD calling for side holes on the line. The breather line is at least 1/2" diameter and runs down with no toilet traps so where would the water accumulate? And at subzero temp is very likely that you will have the engine preheated before engine start. And with oil vapors at over 100F on a running  engine and unlike pitot tubes the breather line facing backward with the only air flow coming out from hot air of the cowling there is simply no chance for icing.  If you feel more comfortable having the side hole is fine with me just wipe out the oil in the cowling.

 

José

[N601RX]

In Bob's case the bladder AD requires the hole to be there.

[Dale Logsdon]

The FAA thought the hole was important enough to issue an AD on a Cessna Lycoming engine mod. STC that left the hole off some 30 years ago. (Cessna AD 82-07-02 gives a good drawing of what the hole should look like.)

[Yourpilotincommand]

Thank you all!!! I at least know that my breather tube is upside down as well as out of position.