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  #1  
Old 12-25-2021, 02:59 PM
Ron B. Ron B. is offline
 
Join Date: Nov 2007
Location: Yarmouth, Nova Scotia
Posts: 2,694
Default First flights unknown noise

My friend's RV-14 has about 7 hours on it. Today he said he was trying to figure out what is causing a noise that sounds to be coming from down by his feet. It is only noticeable or occurring when he reduces the throttle for landing. Today he said he made some slow flights and while reducing the throttle no noise was heard. He says he has been running the engine hard ( more than I would, I broke mine in at 25 squared and I'm not burning any amount of oil, normal 1 quart in 8 to 10 hours). I'm wandering if he's not running the EXP239 very hard and reducing power too fast . He thinks it's perhaps backfiring when he is reducing power. I'm thinking of having him reduce power overhead tomorrow so I can see if I hear anything from the ground.
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  #2  
Old 12-25-2021, 03:20 PM
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Jpm757 Jpm757 is offline
 
Join Date: May 2013
Location: Sherman, CT
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Default

Exhaust Backfiring?
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RV6 #20477 completed 1991 sold.
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  #3  
Old 12-25-2021, 05:23 PM
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Vlad Vlad is offline
 
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Location: Utah
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If he doesn’t have any carpet the floor resonance is pronounced at certain power settings.
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  #4  
Old 12-25-2021, 07:52 PM
Tom Martin Tom Martin is offline
 
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Location: Ontario, Canada
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I changed the short metal hangars to belting and it got rid of a lot of sound and vibration in the floor area
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EVO F1 Rocket 1000 hours,
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  #5  
Old 12-26-2021, 05:49 AM
Ron B. Ron B. is offline
 
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Location: Yarmouth, Nova Scotia
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Quote:
Originally Posted by Vlad View Post
If he doesn’t have any carpet the floor resonance is pronounced at certain power settings.
He does have carpeting.
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  #6  
Old 12-26-2021, 05:50 AM
Ron B. Ron B. is offline
 
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Quote:
Originally Posted by Tom Martin View Post
I changed the short metal hangars to belting and it got rid of a lot of sound and vibration in the floor area
WE are having trouble with one hangar slipping. Plan on addressing this today.
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  #7  
Old 12-26-2021, 02:26 PM
calpilot calpilot is offline
 
Join Date: Aug 2018
Location: Independence
Posts: 230
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I used to hear a funny noise coming from the right side of the Boeing, then I realized it was the co pilot!
Grin....

G.
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  #8  
Old 12-26-2021, 05:02 PM
Ron B. Ron B. is offline
 
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My friend tried not bringing the engine to an idle position on landing approach as if I recall correctly was Mike Seager’s instructions. A few flights today seamed to reduce the backfire considerably.
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  #9  
Old 12-26-2021, 05:32 PM
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rv6n6r rv6n6r is offline
 
Join Date: May 2007
Location: Gearhart Oregon
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Backfiring on throttle reduction / idle or close to, is pretty normal in these beasts. You can gentle the reduction to minimize it but I usually get some popping when reducing power for landing regardless of technique.
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  #10  
Old 12-26-2021, 05:39 PM
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JTJones JTJones is offline
 
Join Date: Jun 2015
Location: Haleiwa, HI
Posts: 157
Default Could it be…

…after-fire? In my -14 w/an IO390X I would get what was termed after-fire if I brought the throttle rapidly to idle. It also happened at idle at an airspeed above 80KIAS. That made glide testing disconcerting cause gliding at idle at best glide would cause the event. Adjusting idle mixture seemed to help.
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