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Old 01-14-2015, 07:30 PM
N731DM N731DM is offline
Join Date: Dec 2009
Location: Golden, Colorado
Posts: 7
Default Crankshaft Seal Blowout In Flight and Emergency Landing RV-7A

About a month ago I launched on a flight from the Denver area to northwestern New Mexico through the Colorado mountains in my RV-7A. I left the airport trimmed for takeoff power and climbed rapidly to about 10k msl before trimming for cruise climb. While leaning I noticed that my oil pressure had dropped to about 35psi. I immediately cranked a 180 degree turn, pulled power and called the tower to declare an emergency. On the way back to the airport I monitored oil pressure and had occasional excursions below 25psi but none for any extended period of time. I made the airport with ease and did not require the assistance from the fire trucks that had been rolled out for me.

Unlike the RV-8 with the blown crank seal, my plane lost its oil out the sides of the cowl through the piano hinges and out the bottom of the cowling. There was very little on the windscreen and except for low oil pressure there was no indication that anything was amiss. I did not know how bad it was till I landed and got out of the plane. The accompanying pictures show the oil streaking down the sides of the plane. The bottom was much worse.

When I removed the cowl, it was evident that the loss of oil was from a blown crank seal. One side was completely blown out and oil was everywhere. My engine had about a quart of oil left in the sump when I drained it. I decided to remove the engine and have my engine shop tear it down. Luckily I did, the main bearings were trashed but the rest of the engine was in good shape. It is now being overhauled.

Once the engine was out I began searching for the cause of the seal failure. In September, 2013 I installed the AntiSplat oil separator with the saddle mount and vacuum valve to help keep my belly clean. That was 165 hours ago. After talking to AntiSplat I removed the saddle mount and vacuum valve and found two items. First, the rivet that holds the vacuum valve together had failed and was lying in engine side of the valve (see pic). This allowed the backing plate on the other side to float free. Blowing through the failed valve showed restriction through the valve toward the exhaust. There was no restriction of flow back toward the engine. Second, the pipe from the valve through the saddle mount was almost completely coked up. There was about an eight inch hole in the coke greatly restricting flow (see pic). I took a pen and attempted to push it through the coked up oil. It did break but it required substantial force to break through the coke. I shot two videos of the mount and valve ( and

I believe the crank seal failure was caused by over-pressuring of the crankcase caused by the AntiSplat products. It is hard to lay the blame for the over-pressuring to either the vacuum valve or the saddle mount. The valve was defective and the saddle mount was almost completely closed off. Either or both in conjunction could have caused the problem. If you have one of these systems on your plane ? Beware. Antisplat has a service bulletin concerning these problems and attempted to notify owners. Unfortunately, I did not receive this notification. If you have not seen it, go to their web site. Also, make sure you have their Safety Bypass Kit installed. As for me, I will run the air/oil separator, but will never again install the saddle mount or vacuum valve on my plane. I was very lucky to have made it back to the airport and will not take that chance again.

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Old 01-14-2015, 07:40 PM
JimWoo50 JimWoo50 is offline
Join Date: Oct 2005
Location: Chicago sw suburbs
Posts: 411
Default Glad you are ok

Nice job flying the aircraft.
Jim Woolard C56
N9855J RV-6 Donated 2020
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Old 01-14-2015, 07:50 PM
Mike S's Avatar
Mike S Mike S is offline
Senior Curmudgeon
Join Date: Sep 2005
Location: Dayton Airpark, NV A34
Posts: 16,109
Default Welcome to VAF!

David, first post, and it is a major biggie. Welcome to VAF

Good job flying the plane, very glad you are here to write up the experience instead of the NTSB doing it.

This issue of the air/oil separator has been hashed out many times in the past------
Mike Starkey
VAF 909

Rv-10, N210LM.

Flying as of 12/4/2010

Phase 1 done, 2/4/2011

Sold after 240+ wonderful hours of flight.

"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
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Old 01-14-2015, 07:54 PM
Steve Melton's Avatar
Steve Melton Steve Melton is offline
Join Date: Apr 2011
Location: Cincinnati, OH
Posts: 3,529
Default whew!

Good job getting it back. I'll just keep cleaning the belly.
Steve Melton
Cincinnati, OH
RV-9A, Tip-up, Superior O-320, roller lifters, 160HP, WW 200RV, dual impulse slick mags, oil pressure = 65 psi, EGT = 1300F, flight hours = 900+ for all

Simplicity is the art in design.
I was born an airplane nut. I have no explanation for it.
My Artwork is freely given and published and cannot be patented.
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Old 01-14-2015, 08:15 PM
Walt's Avatar
Walt Walt is offline
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 6,351

Originally Posted by Mike S View Post
This issue of the air/oil separator has been hashed out many times in the past------
You're not the first to have a problem with this setup... and unfortunately you probably won't be the last!

With a fresh OH you should have a nice tight engine, my suggestion for what its worth is remove it and live with a little oil on the belly
Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 2000+ hrs, New Titan IO-370, Bendix Mags
Website:, Email:, Cell: 972-746-5154
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Old 01-14-2015, 08:56 PM
strahler13's Avatar
strahler13 strahler13 is offline
Join Date: Jan 2005
Posts: 401

Mike, your comment-----This issue of the air/oil separator has been hashed out many times in the past------makes it sound to me like you are implying that this is old news. Nothing left to discuss--move along. I think quite the opposite. Here seems to be another purchaser of the Anti-Splat product that did not get any notification from the manufacturer, in spite of claims to the contrary.

I can't help but think the OP is VERY lucky. A flight in mountainous terrain with a fortunate result.

I don't have a dog in this fight, but I can't help but think people are putting their lives in serious jeopardy.

Mark Strahler
RV-6 (Purchased flying)
KFFC-Peachtree City, GA
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Old 01-14-2015, 09:01 PM
Jesse's Avatar
Jesse Jesse is offline
Join Date: May 2005
Location: X35 - Ocala, FL
Posts: 3,711

Originally Posted by Walt View Post
You're not the first to have a problem with this setup... and unfortunately you probably won't be the last!

With a fresh OH you should have a nice tight engine, my suggestion for what its worth is remove it and live with a little oil on the belly
Amen to that!
Jesse Saint
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Old 01-14-2015, 09:02 PM
grubbat's Avatar
grubbat grubbat is offline
Join Date: May 2012
Location: Ga
Posts: 718
Default Good job

Congrats on getting your bird back safe and sound. It could have been a lot worse.

Sorry you had to be the ginny pig on the clean belly contraption. Those things are neat when they work, and when they don't, well, hey, it's expermential!

Seriously, glad you lived to tell your story for others who can now benefit.


RV-3 Sold
RV-4 Sold
1968 Twin Comanche - Sold
RV-6a Sold
1965 Comanche 260 - Sold
RV-9 Built and Flying
600A Aerostar - Sold and regretted
2000 Maule MXT-7 Project
1965 Maule M4 Bushwacker projectů till RV-15 shows up
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Old 01-14-2015, 09:15 PM
N427EF N427EF is offline
Join Date: Oct 2005
Posts: 1,565
Default Time to remove Antisplat Air /Oil sep

Sorry to hear of your misfortune but great job flying the airplane.

I have read and heard all about the coking up of the breather line when plumbed into the exhaust and I still have the system in use.
After reading about the first incident of a blown crankshaft seal I now am seriously considering removing the whole Antisplat Air/Oil gizmo.

To the OP:
Was your reed valve supplied by Antisplat?

Glad you are ok.
Ernst Freitag
RV-8 finished (sold)
RV-10 IO-540 8.5:1
Running on 91 Octane E10 mogas since 2011
Don't believe everything you know.
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Old 01-14-2015, 09:52 PM
BillL BillL is offline
Join Date: Sep 2007
Location: Central IL
Posts: 6,322
Thumbs up Moderator ?

Very Happy David got down safely! Good job. Sorry you missed the big discussion here on VAF about this very thing. David, do you have any suggestions as to getting the word out?

Moderator: Wouldn't this SECOND alert (seal blow out) reach more people in "Safety" - with a modified title for all to read?


Last edited by BillL : 01-14-2015 at 09:59 PM.
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