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912ULS Airbox Water Intrusion

 
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budyerly@msn.com



Joined: 05 Oct 2019
Posts: 280
Location: Florida USA

PostPosted: Sun Nov 08, 2020 5:04 pm    Post subject: 912ULS Airbox Water Intrusion Reply with quote

PROBLEMS WITH EUROPA XS 912ULS INTAKE WATER INTRUSION

As many of you know, I install very few 912ULS engines as I believe that the 914 is the ideal engine for the Europa XS. That said, for the pilot not interested in flying high and fast but a little lower, with lower up front costs and fewer maintenance headaches, the 912UL and 912ULS are very acceptable substitutes. Particularly the 912ULS of 100 HP when equipped with a constant speed propeller. It is only slightly slower in cruise, lighter, has excellent takeoff performance when operating at density altitudes of less than 3000 feet, and is reasonable at cruising altitudes of 7000 feet or below. Granted it has been eclipsed by the new 912iS engine, but it is still much more cost effective than the newest Rotax injected computer babies and can be maintained with simple hand tools.

I recently had a second hand owner of a nicely built Europa XS powered by a 912ULS, which was built in accordance with the Europa manual, have to store his aircraft outside on the airport ramp for a year in central Florida. Time passed as he was busy with debilitating medical difficulties. I saw the aircraft derelict and looking like a mildew experiment. I decided to do some checking. I last saw the aircraft around Christmas time, however, we’ve had some 30 + inches of rainfall and extremely warm weather since then.

I received the OK from the owner and airport and on initial inspection, I could not pull the prop through. I opened up the cowl, and found the #1 and 3 cylinders had water in them, the airbox had some black mildew on the starboard side which plugged the 1/8 inch drain hole completely. This resulted in the starboard carb float bowl filling with water. The entire 1/3 carb had a redish brown film. The redish brown film was a fungus common here in Florida which grows on the inside surface of fuel tanks in the steamy summers. Further inspection showed the intake manifold slime covered also. The owner agreed to allow me to transport the aircraft back to the shop to dry it out and perform an engine and airframe condition inspection. After washing the exterior, upsetting many insect colonies, removing the carbs, pulling the plugs and lower oil return line, I removed a half cup of water from the cylinders and about the same from the bottom of the crank case. Luckily, the water in the crankcase simply flowed to the bottom and was covered by the settled oil. The bore scope revealed the pistons valves rings and cylinder walls were remarkably clean. His gearbox on removal showed no sign of water intrusion and looked like new. He got lucky.

I am now looking into what can correct this from happening to others with stock installations. Many of you owners have had similar comments over the years about the NACA duct opening on the Europa XS 912 UL/ULS allowing water to flow into the intake box. For short time outside tie down, the drain holes of 1/8 inch should be fine to drain most of the water that could possibly seep in. But to prevent water intrusion totally when tied down, the solutions were many and varied. For some builders you simply:

1. Never leave your aircraft outside in the rain. Obvious, but not always possible.
2. Cover the aircraft with a rain proof cover when tied down. Obvious for lengthy tie downs. However, for the average cross country flight, these covers can be quite bulky. The Europa does not have a sail locker in the bow. The covers are a bit pricey also.
3. A plug can be devised to block the inlet and most of the water. An inexpensive fix if done right.
4. Tape over the hole for tie down.
5. Fabricate a 914 style inlet and ducting to avoid the NACA rain inlet problem completely.
6. Make up some sort of water catch to drip the water away from the filter inlet hole.

For the diligent builder who follows the instruction without modification or the second hand owner who must tie his aircraft down in a rainstorm, is there a solution other than plugs and tape that can be easily done during an annual condition inspection to relieve him of the fear of a waterlogged engine?

Nev and I consulted on this some years ago and I've had a few changes in how I do it but my ideas are not the only ideas.

I will provide some construction background and diagrams on why this is an issue and perhaps some ideas of my own soon, but I am interested in your solutions also.

Best Regards,
Bud Yerly


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JonathanMilbank



Joined: 14 Apr 2012
Posts: 383
Location: Aberdeen area

PostPosted: Mon Nov 09, 2020 2:59 am    Post subject: Re: 912ULS Airbox Water Intrusion Reply with quote

When my aircraft used to have the Classic cowls with NACA air duct, before I fitted the Nev Eyre cowls without such inlet, I always took the canopy and forward fuselage cover with me if expecting to park outside somewhere. Each year one of my friends took the aircraft away for a fortnight and left it outside in the Scottish rain, which can often last for days. Seemingly the cover prevented water from entering the NACA duct and airbox, possibly because I washed the cover in a solution designed to waterproof tents.

The other route for potential ingress of water is the fuel tank breather tube on top of the fuselage behind the cockpit and, for that matter, the fuel tank filler cap situated on top of the Classic fuselage if its O-ring seal isn't good. Therefore if parking outside I wrap and tie something like a surgical glove over both breather tubes. Thus far I haven't failed to notice and remove the glove before flight.


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budyerly@msn.com



Joined: 05 Oct 2019
Posts: 280
Location: Florida USA

PostPosted: Mon Nov 09, 2020 2:25 pm    Post subject: Re: 912ULS Airbox Water Intrusion Reply with quote

Jonathan,

You folks in the UK do have a problem. A waterproof cover is best. No matter what you do, if exposed to the elements the cockpit, engine, and fuselage can get water in it. They just take up so much room for the good ones.

Yes those vents over the top can be pesky. In tight left turns and a fairly full tank, they vent fuel also. Even on the ground with a cold refuel to the top then letting the plane warm up in the hot summer sun, expands the fuel and you have a class a fuel stain.

That's why I put the vent on the bottom. But, on a mono that can lead to problems with muddy fields and clogging the vent if not placed properly.

Ah compromises.
All the best,
Bud Yerly


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