ilovecornfields Posted May 9, 2018 Report Posted May 9, 2018 (edited) Heard this noise after shutting down the engine and putting the plane away in the hangar. This was after a short (20 min) flight to a local airport with no issues during the flight. Took this video a couple of minutes after I noticed the noise. It slowly decreased in amplitude and by the time I got the top cowling off noise was gone. Master and mags were off the entire time. Tried doing a runup afterwards and alternator, mag drop, mag grounding all seemed normal. Any thoughts? Plane is an Ovation 2 with no vacuum pump. edit: YouTube video link http://www.youtube.com/watch?v=mtsz_n8ZO3s CE371C63-C083-4929-962B-34230EEE4E13.MOV Edited May 9, 2018 by ilovecornfields Quote
carusoam Posted May 9, 2018 Report Posted May 9, 2018 How about posting in YouTube? Easy and everyone can view it... Trying to view it on an iPad, it locked up MS... Best regards, -a- Quote
ilovecornfields Posted May 9, 2018 Author Report Posted May 9, 2018 13 minutes ago, carusoam said: How about posting in YouTube? Easy and everyone can view it... Trying to view it on an iPad, it locked up MS... Best regards, -a- Thanks. Added a link to the original post. My first YouTube video! 1 Quote
carusoam Posted May 9, 2018 Report Posted May 9, 2018 Know what fuel boiling sounds like? learned two things today! My first iPhone post... -a- Quote
takair Posted May 9, 2018 Report Posted May 9, 2018 Hangar elves doing post flight maintenance? Quote
ilovecornfields Posted May 9, 2018 Author Report Posted May 9, 2018 46 minutes ago, carusoam said: Know what fuel boiling sounds like? learned two things today! My first iPhone post... -a- Sounded different than the usual post-shutdown percolating. Seemed more mechanical or electrical to me. That’s what I originally thought, which is why I didn’t take the cowling off right away. I wish I hadn’t waited because by the time I got it off the noise had stopped. Quote
jaylw314 Posted May 9, 2018 Report Posted May 9, 2018 was it raining? water dripping onto something hot somewhere? Quote
N201MKTurbo Posted May 9, 2018 Report Posted May 9, 2018 (edited) Maybe something like an alternator cooling fan that is loose and kept spinning. Edited May 9, 2018 by N201MKTurbo 1 Quote
carusoam Posted May 10, 2018 Report Posted May 10, 2018 Where I get the fuel boiling idea from... for the IO550.... and a great way to understand the hot start procedure.... 1) This is the basis for needing the hot start procedure... 2) When The Fuel gets hot enough under the cowl, it starts to vaporize, Essentially, it boils, generating bubbles of fuel vapor. 3) If you attempt an ordinary start, without flushing the fuel system of all the bubbles, the mixture gets all goofed up. Some is pushed forwards releasing pressure and others arrives as vapor and not fuel... really confusing whether you have flooded the engine or starved it. 4) The hot start procedure... takes this hot bubbling fuel and sends it back to the selected tank... (IO550 only) 5) This is only knowledge from reading the POH... I have only assumed that it is right... 6) You can experiment with this idea.... After a flight on a hot day is the only time this will happen... It gets louder and more noticeable, the hotter the day is... It takes time to get hot enough to boil... Park the plane quickly, and get out and listen.... it will still be quiet... Once it is boiling... try to cool it off using the hot start procedure.... Throttle in, mixture out, fuel pump on.... (just like prepping for the hot start) There is still going to be a part of the fuel system that is not recycling back to the tank. It probably boiled away and went down stream anyways, like it or not... When I hear that sound, it is a reminder to open the oil door and point into the wind... when doing a quick turn... 7) For a visual experiment of a similar challenge... boil a pot of water... on the stove in the kitchen... turn off the stove... Dump half the bubbly water down the drain... (similar to boiling fuel going back to the tank) Replace the water that has been dumped with cold water from the tap... (similar to cold fuel coming from the tank) Put the pot back on the hot stove... that is no longer on... (similar to fuel being in the hot, slowly cooling engine) You get the similar experience... the bubbles go away as soon as the cold water gets added to the pot... Bubbling May begin again if the stove is really hot and the replacement water isn’t very cold.... Briefly, on a hot day when you hear the boiling sounds. Do the throttle in, mixture out, fuel pump on, following the procedure... see if there is a change in the boiling sound... taking the cowling off will take too much time... It better be quiet for a while or the hotstart procedure isn’t working right.... Fuel is a funny substance... we want it to vaporize fully, but not until we are done metering it into the engine...the vapor bubbles are what messes up the metering.... Let me know if this doesn’t sound right... I’m only a Chemical Engineer masquerading around as a Private pilot.... Best regards, -a- 1 Quote
ilovecornfields Posted May 10, 2018 Author Report Posted May 10, 2018 Thanks for the responses. It may have been bubbling but definitely not the sound I’m used to. After taking the cowling off and sending the video to the mechanic he had me start the engine and do a runup and it seemed to start right away. I always open the oil filler door when I shutdown so I doubt it was too hot in there. Looked at the JPI data for the flight and everything looked good. Didn’t know the alternator had a separate cooling fan. I’ll have to ask the mechanic about that tomorrow. Also, no rain, no water, not a particularly hot day and no hamsters to be found anywhere. 1 Quote
Marauder Posted May 10, 2018 Report Posted May 10, 2018 Hamster on a tread mill? Clarence When I first heard it, I thought there was a midget under the cowl pleasuring himself. ⚕️ 1 1 1 Quote
Marauder Posted May 10, 2018 Report Posted May 10, 2018 Thanks for the responses. It may have been bubbling but definitely not the sound I’m used to. After taking the cowling off and sending the video to the mechanic he had me start the engine and do a runup and it seemed to start right away. I always open the oil filler door when I shutdown so I doubt it was too hot in there. Looked at the JPI data for the flight and everything looked good. Didn’t know the alternator had a separate cooling fan. I’ll have to ask the mechanic about that tomorrow. Also, no rain, no water, not a particularly hot day and no hamsters to be found anywhere. It is definitely not the hot fuel sound. Really does sound like some sort of device spinning. A cooling fan makes sense.Sent from my iPad using Tapatalk Pro Quote
carusoam Posted May 10, 2018 Report Posted May 10, 2018 If you left the Master on.... there is one fan that the long bodies get that the other M20s don’t... But it supposed to come on with the windshield defrost lever...? How is that for being equally incorrect, but more terse this time...? Best regards, -a- Quote
bonal Posted May 10, 2018 Report Posted May 10, 2018 Turbine blades turning in the wind, come on now when did you do the upgrade? 1 Quote
ilovecornfields Posted May 18, 2018 Author Report Posted May 18, 2018 It looks like @carusoam wins the prize. After a couple of ground runs, a couple of trips around the pattern and an inspection at my home airport, I flew out to Top Gun. Had an awesome experience there. Mark came out as soon as I pulled up and has his ear on the cowling within seconds (after seeing the keys on the glareshield, of course). The plane made the noise again and he thought it was normal due to fuel evaporating, but took the cowling off and did an inspection. He also installed my Hubba Hubba hubcaps (since apparently the FAA requires a 337 for hubcaps!) and I had an uneventful (and much more relaxing) flight home. Couldn't be happier with my experience with Top Gun. Mark seemed extremely knowledgeable and was really efficient and welcoming. Would definitely recommend them to anyone looking for a MSC in California. Price was very reasonable as well. 3 Quote
thinwing Posted May 18, 2018 Report Posted May 18, 2018 337 to change hubcaps even if they aren't original design is just rediculous Quote
Hank Posted May 18, 2018 Report Posted May 18, 2018 7 hours ago, thinwing said: 337 to change hubcaps even if they aren't original design is just rediculous I agree. It's not a major modification per the FARs, just another fearful CYA by an A&P who js afraid to make a decision and doma simole logbook entry. Quote
ilovecornfields Posted May 18, 2018 Author Report Posted May 18, 2018 4 hours ago, Hank said: I agree. It's not a major modification per the FARs, just another fearful CYA by an A&P who js afraid to make a decision and doma simole logbook entry. I’m not a mechanic but I think it was required by the STC. I didn’t get the impression that it was my mechanics idea to do that. Quote
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