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n7188u
Joined: 15 Nov 2015
Posts: 401
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 Posted: Mon Nov 15, 2021 5:57 pm Post subject: Noisy cockpit |
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Dear Europa Friends,
First let me say I am really enjoying my Monowheel. This last weekend I took my wife on a trip to Miami (first x-country on the Europa for her) and it was a total success. She really loved it and we had a great weekend.
With that said I have a question about something that has been bothering me for a while. Although the airplane has been great, I am trying to gain confidence in my engine. Let me explain: My engine is a 912ULS rebuild by an iRMT Repair Center. Not quite an overhaul though (no crankshaft change but engine was torn down, inspected and were necessary new parts installed). The engine runs quite nice but I did have some issues with it that have been addressed. I am having a little difficulty fully trusting this engine as I think it feels a little rough and noisy.
I have been told that the engine sounds great and smooth from outside the airplane (some people thought it was an electric airplane since it is so quiet) but I find it quite noisy inside and feels a little rough. Maybe its me being picky since it is really not bad but I am so used to after almost 40 years of flying behind Lycosaurus and Continentals engines that I find that my engine seems to scream inside the Europa cockpit. Vibration is not high but I do feel what I can only describe as a high frequency short amplitude harsh vibration in the panel and I can hear it contributing to some level of fatigue after an hour or so of flying. It's a bit gritty and makes me feel as if the gearbox is grinding itself to pieces. But oil looks fine, no metal in the filter or magnetic plug and the gearbox clutch torque check passes fine. I have balanced the carbs multiple times. I have dynamically balanced the prop and replaced the rubber mounts with Europa supplied ones. I have to reiterate, it's not bad and my Lycoming on the LongEZ vibrates more but in the Rotax it feels a bit harsh and I am not used to it. I did fly in an RV-12 with the same engine and it felt smoother. So a few questions:
1.- Is the Europa a little noisier and transmits more vibration from the engine than say an RV-12? The RV-12 felt and sounded like a normal airplane inside, my Europa engine sounds like it screams.
2.- My aviasport tach needle vibrates quite a bit. Like a high frequency buzz. My altimeter also tends to wobble a bit at certain power settings. is this normal?
3.- I just installed new mounts from Europa but do you guys think that these mounts may be a little hard and allow a bit of vibration to pass through to the airframe. They do feel hard.
4.- Could it be just me not used to the Rotax? maybe this is perfectly normal in the Europa and the RV-12 just happens to be a little smoother. my airplane has not interior covering, just painted. the RV-12 I flew was covered inside.
If I just knew that it is normal for the Europa to be a little noisier than the RV-12 inside I would relax. Just no way to know since the only Europa I have ever flown is mine. Maybe it's a monowheel thing (it has after all a big hole underneath and the engine is attached to this central tunnel that could act as a horn!)
Thoughts?
Best Regards and Thanks.
Chris
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budyerly@msn.com
Joined: 05 Oct 2019
Posts: 282
Location: Florida USA
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| Posted: Mon Nov 15, 2021 8:17 pm Post subject: Noisy cockpit |
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Chris,
I'm surprised, as the Rotax with the Europa supplied CKT muffler is quite quiet with the 912S.
N12AY is a trigear. With the sealed tunnel and 914 it is very quiet. Most passengers in it are amazed at how quiet and smooth it is.
That said, the Mono tends to be noisier due to the wheel well and airflow through the tunnel.
The 912S is not that much noisier than the 914. Turbos with a muffler really quiets it.
The 912S is a bit rougher of an engine than the 914. But it is smoother than a Lycoming.
The RV and Zenith Rotax powered aircraft are noisy in my opinion (I've flown a lot of Zeniths). The metal tends to reflect the noise in the cockpit
The LSA metal aircraft are not terribly noisy with an interior and properly fitted canopy.
A properly built composite aircraft is very solid sounding. Free from oil canning noises common in metal aircraft.
In my articles on my website and other places I give some typical causes of vibration. Word doc attached of an old one.
In my Rotax troubleshooting guide I make mention of the carb balance tuning. I normally can balance a Rotax by ear and visual inspection.
If the mag drop (ignition check) is at the limit or a touch higher, you have carb balance and or ignition issues.
Here are some tips for smoothness some folks don't realize:
Run up the engine and if your calves begin to vibrate, it is the propeller. Your calf muscle is about the 1/4 harmonic of the prop.
If the prop has one blade out by a 1/2 degree the vibration is awful. Make sure the prop blade angles are as close as possible to one another. If you didn't static balance your prop with the spinner. You must.
Trying to find noise and vibration is straight forward:
On the ground: Tied down.
Pull the cowl and run the engine and note the ignition modules. They should be steady from idle to full power. I mean you should be able to read the serial number at idle and fuzzy up to 4000. After 4000 the uncowled engine is hard to read.
Check the exhaust and look for any broken springs, down pipes and make sure the reflector shield is secure and doesn't rattle. The muffler and pipes should not contact the cowl or engine frame.
Check the Binx nuts are tight and the frame is tight.
Check the propeller tracking while its running. (Safely abeam the prop arc at low power and well clear.) I know that's odd, but it happens that blades have been known to flex. One poorly seated blade can be seen.
Check the spinner tracks. Europa classic spinners are tough to get precisely smooth. And they are long and heavy.
Have the propeller dynamically balanced. (The Europa is a very light aircraft and the whole airframe shakes from the prop blast sometimes making a prop balance difficult.) It may need to be done in flight.
I've flown hard and soft mounts. Neither had a noise difference or vibration.
Listen to your exhaust note. If very loud you probably have a modified muffler or its blown out a baffle. The Rotax can sound like one of those rice burner cars the kids run around in if the muffler is not either a Rotax or the even quieter CKT muffler.
There are a number of mufflers for the Rotax. Some are awful. I'm prejudiced in that the CKT is the nicest note. That's why it is used by most of the manufacturers in Europe as it meets the DB level.
Look for engine to cowl rub marks.
Ground Airframe Checks:
Run the engine at various RPMs (roughest point preferably) and listen to the airframe. Put your ear next to the wing, the stabs, the fuselage.
Ground Rattle checks:
Doors without any seals will rattle a bit.
Access panels that are loose especially the cockpit ones are noisy, heavy wires rattle if not tied.
Rudder cables that are not properly guided and clearance and vibrate against bulkheads, and fuselage unless properly supported.
The panel starboard side is often only secured at the top and will vibrate against the fiberglass firewall.
Climb in the aircraft:
The Europa is like being in a Thermos insulated bottle. Pretty well solidly glued and therefore like wood in that it is devoid of skin rattles and noises. If you hear rattles and noises, you have components that are vibrating in the structure.
Case in point: If a control rod in the wing is just barely clearing a rib, if there is vibration, it will be transmitted to the airframe.
Feel the airframe at different RPMs. Relax your legs and feel the movement of your butt, legs, and arms.
Observe your instrument panel. A shallow clear cup of water that is splashing is your first sign of serious vibration issues.
Check your instrument panel is not vibrating blurring the analogue instruments.
The mono wheel well can be rather noisy from air flow. This depends on many factors:
The gaps in the gear and brake handle and any other holes. Gear frame arm to fuselage cutout clearance.
Door seals are important. If the door seals are leaky, there is a suction in the cockpit formed and the air is pulled through the slots in the cockpit module.
Wing gap seals are necessary also as the air between the fuselage and wing root as the air smacks into the spar then rumbles into the cockpit.
Finally, interior finish choices are important. Paint is light, but the fabric / padded leather interior is very quiet.
At 100 knots or less you can casually talk in 12AY. Over 120 knots indicated, the wind noise outside the canopy is quite loud in any aircraft.
I've never needed ANR headsets in any of the aircraft I have built.
I'm interested in your rebuilt engine. Did they tinker with anything or is it stock? A difference in timing makes a difference in smoothness. Like I said before, if the muffler is one of those "Performance" mufflers. They are loud.
Finally, paint and finish tightens up the aircraft, smooths the airflow also. It is like a washed car is quieter.
My test is:
If my wife can go 2000 miles in 6 hops without complaining about noise, seats, or anything other than our bladders, I know my plane is comfortable and quiet. She can't go that far in our Honda Accord. She prefers my F150 when we travel.
Hopefully, you find your issues and enjoy a very quiet, comfortable aircraft.
Best Regards,
Bud Yerly
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n7188u
Joined: 15 Nov 2015
Posts: 401
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| Posted: Tue Nov 16, 2021 6:42 am Post subject: Re: Noisy cockpit |
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Great reply Bud. Very detailed as always.
I will create a checklist and go through the checkpoints you outline. A few notes based on preliminary reading of your message but first one question:
What do you mean by "should be able to read the serial number at idle and fuzzy up to 4000. After 4000 the uncowled engine is hard to read."?
1.- I have zero insulation inside. No carpet, nothing on the firewall, noting on the sides. Airplane not painted but quite slippery based on high cruise speeds (130-140 knts). Airplane is indeed noisy at my high cruise speeds.
2.- I don't have the intake plenum on the engine. Just good old fashion cone K&N filters. I did that to keep the airplane light on the nose. I was planning to install the plenum after flying the airplane a little but the performance is so spectacular as it is I decided to leave it alone. I do know that intake noise can be high in the two stroke Rotaxes.
3.- Engine feels silky smooth at the ground when doing runup at 4000 RPM.
4.- Prop not static balanced since the dynamic balance (with spinner) is almost dead on. Tweaked it to made it better though.
5.- My spinner is off according to what people tell me. Have not fixed that but it is a light DUC CF one.
6.- Checked blade pitch with a laser tool I made. Will check track though.
7.- I do have a buzzing tach needle and my "used" altimeter wobbles up and down around 100'.
8.- The muffler used to touch the top of the cooling tunnel but fixed that. No evidence of interference.
9.- My IAS at low altitude is always at 130-140 knts or so yes that can make it noisy (CAS is a little lower than that)
My engine: Pulled out of a school CTLS because it reached TBO. Rebuilt (not overhauled but completely torn apart) by an iRMT Repair Center in Canada. The owner is an iRMT instructor. Confirmed with Rob Seaton at Rotech that the place is legit before buying the engine. No modifications. All stock. New CKT muffler. I did have a few issues with the engine (needed new ignition module and had to do some work on the carbs). But it is running good and strong.
Best Regards,
Chris
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budyerly@msn.com
Joined: 05 Oct 2019
Posts: 282
Location: Florida USA
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| Posted: Tue Nov 16, 2021 7:50 am Post subject: Noisy cockpit |
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Answers in Red:
What do you mean by "should be able to read the serial number at idle and fuzzy up to 4000. After 4000 the uncowled engine is hard to read."
See 4 below.
1.- I have zero insulation inside. No carpet, nothing on the firewall, noting on the sides. Airplane not painted but quite slippery based on high cruise speeds (130-140 knts). Airplane is indeed noisy at my high cruise speeds
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