Steve, the rubber body of the hose departed from the Twist-Tite connector, the connector stayed attached to the AN fitting on the engine. I was able to push
the rubber hose back onto the Twist-Tite connector by hand but then was unable to pull it back off again. I caused 2 engine stop/start situations in-flight that day by selecting a faulty fuel pump. I believe the 2 restarts from near windmill to instantaneous
5700 rpm created pressure pulses at the barbed hose connection; the hot oil-heated rubber hose ballooned under pressure and slipped up over the barbs on the connector. That hose had 15 flight hours on it – without the engine surges/pressure pulses it would
not have failed that day – though it was bound to happen – a simple stainless worm clamp would have kept it together. It was the only hose of that type in my oil system. Lesson is there are high quality push-on connectors and there are poor quality push-on
connectors. I now use the AQP fittings and AQP stainless Racing Hose everywhere in the oil system. Jeff
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From:
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Steven W. Boese <flyrotary@lancaironline.net>
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Subject:
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Re: [FlyRotary] Re: Return to Flight - 2
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Date:
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Wed, 20 May 2015 17:16:59 +0000
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To:
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Rotary motors in aircraft <flyrotary@lancaironline.net>
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Jeff,
I did notice the oil pump outlet connection location in the photos. Unless the passage in the front iron going to the front cover O-ring has been plugged, capping the original front cover port still
leaves the O-ring subject to the oil pump outlet pressure.
I used the same front iron oil pump outlet location that you are using. That location is connected to an FC598-10 Aeroquip Socketless AQP hose which is the same type of hose that failed for you.
Did the hose itself fail or was the failure at the connection? While the oil pressure and temperature in the hose are well within the specs for the hose I am using, your experience has me reconsidering that decision. Maybe the specs refer to the hose itself
and not the actual connection?
Steve
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From: Jeff Whaley
Sent: Wednesday, May 20, 2015 12:51 PM
To: 'Steven W. Boese'
Subject: RE: [FlyRotary] Re: Return to Flight - 2
Steve, one thing I forgot to mention: Due to the potential of front-cover, o-ring failure I elected to not use that port and capped it. I removed a brass
plug from the front iron and tapped that port to accept a 16mm to flared AN fitting – that is where oil comes out of my engine. If you look carefully at the last two photos posted you can see it.
Jeff
From: Jeff Whaley
Sent: Wednesday, May 20, 2015 10:11 AM
To: 'Steven W. Boese'
Subject: RE: [FlyRotary] Re: Return to Flight - 2
Hi Steve, thank you for another detailed explanation; I know you have done a great deal of instrumentation on these engines and I appreciate your feedback –
those plots are priceless.
My oil temperature probe is mounted at the return port after the second oil cooler; my coolant temperature probe is mounted near the water pump outlet. The
Mazda oil cooler was NOT installed when the hose failed.
So from your explanation, the Mazda oil cooler is not the best choice for aviation use whether it’s a single cooler or linked in series?
It would not take too much effort (2-3 hours) for me to remove the Mazda cooler and reinstall my second Fluidyne where it was previously mounted; I kept the
cowl openings the same and adapted the Mazda oil cooler install to fit. I would have to go back to installing cover plates for winter operations to control oil temperature – I can live with that and with synthetic oil, cool oil is not a huge issue.
When I get the coolant temperature under control, time to re-experiment with only one oil cooler – two is definitely overkill for winter operations.
Jeff
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