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yak 55 engine surge, in flight

 
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Epistaxis



Joined: 19 Dec 2010
Posts: 13
Location: Nebraska, USA

PostPosted: Fri May 03, 2013 3:06 pm    Post subject: yak 55 engine surge, in flight Reply with quote

Hello, have a Yak55 which just presented with an engine or prop surge, after doing moderate acro. Initial indication was a rapid loss in performance. After throttle back, settled down to a constant surge. Fuel pressure was good and constant,have checked the entire fuel system everything is clean and clear. Can`t duplicate the problem on the ground during runup. But did surge again on next test flight. Would like to know if the aneriod diaphragm or the larger pressure diaphragm were failing could cause this, although no garbage was found in the carb screens. Or should I focuse on the prop and governor. Governor screen is clean as well. Has anybody run across this situation? Thanks

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viperdoc(at)mindspring.co
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PostPosted: Fri May 03, 2013 3:47 pm    Post subject: yak 55 engine surge, in flight Reply with quote

Have had the aneroid diaphragm cause surging and have had engine failure at 100% T.O. Power due to a flapper in the fuel line that broke off and blocked the carb fuel screen. With the flapper the surge was intermittent at high power settings. It improved with power reduction. The diaphragm was most noticeable at 5000 to 6000 ft.
Doc

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On May 3, 2013, at 6:06 PM, "Epistaxis" <ShawnJBurwell(at)aol.com> wrote:

Quote:


Hello, have a Yak55 which just presented with an engine or prop surge, after doing moderate acro. Initial indication was a rapid loss in performance. After throttle back, settled down to a constant surge. Fuel pressure was good and constant,have checked the entire fuel system everything is clean and clear. Can`t duplicate the problem on the ground during runup. But did surge again on next test flight. Would like to know if the aneriod diaphragm or the larger pressure diaphragm were failing could cause this, although no garbage was found in the carb screens. Or should I focuse on the prop and governor. Governor screen is clean as well. Has anybody run across this situation? Thanks




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javiercarrascob



Joined: 06 Sep 2009
Posts: 62
Location: Virginia

PostPosted: Fri May 03, 2013 5:21 pm    Post subject: yak 55 engine surge, in flight Reply with quote

I used to have a similar issue but after prolonged discent at lw RPM settings.

After changing to the auto spark plugs an keeping the temps over 150. never had it again.

Good luck.

Javier Carrasco
Yak-55m
N5245H

--- On Fri, 5/3/13, Epistaxis <ShawnJBurwell(at)aol.com> wrote:

Quote:

From: Epistaxis <ShawnJBurwell(at)aol.com>
Subject: yak 55 engine surge, in flight
To: yak-list(at)matronics.com
Date: Friday, May 3, 2013, 7:06 PM

--> Yak-List message posted by: "Epistaxis" <ShawnJBurwell(at)aol.com (ShawnJBurwell(at)aol.com)>

Hello, have a Yak55 which just presented with an engine or prop surge, after doing moderate acro. Initial indication was a rapid loss in performance. After throttle back, settled down to a constant surge. Fuel pressure was good and constant,have checked the entire fuel system everything is clean and clear. Can`t duplicate the problem on the ground during runup. But did surge again on next test flight. Would like to know if the aneriod diaphragm or the larger pressure diaphragm were failing could cause this, although no garbage was found in the carb screens. Or should I focuse on the prop and governor. Governor screen is clean as well. Has anybody run across this situation? Thanks


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Epistaxis



Joined: 19 Dec 2010
Posts: 13
Location: Nebraska, USA

PostPosted: Fri May 03, 2013 5:43 pm    Post subject: Re: yak 55 engine surge, in flight Reply with quote

Doc, thanks for the response, could you please clarify where you found sections of the flapper valve, which filter IE...course or fine on the firewall or in the carb inlet course screen, and was this part of the emergency fuel shut off flap. In addition, this evening after returning to the hanger and after the test flight this afternoon have found fuel dripping from and around the spray bar in the carb venturi. Thanks

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viperdoc(at)mindspring.co
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PostPosted: Fri May 03, 2013 6:17 pm    Post subject: yak 55 engine surge, in flight Reply with quote

A 6 mm and a 4 mm fragment of the inner liner of the main fuel line to the carb. We found it in the finger screen in the carb. It is not uncommon to have a small amount of fuel drip out of the carb after shutdown especially if you do not advance the throttle to wide open just as you cut the mags off. I am by no means an expert on the carb.
Doc

Sent from my iPad

On May 3, 2013, at 8:43 PM, "Epistaxis" <ShawnJBurwell(at)aol.com> wrote:

Quote:


Doc, thanks for the response, could you please clarify where you found sections of the flapper valve, which filter IE...course or fine on the firewall or in the carb inlet course screen, and was this part of the emergency fuel shut off flap. In addition, this evening after returning to the hanger and after the test flight this afternoon have found fuel dripping from and around the spray bar in the carb venturi. Thanks




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http://forums.matronics.com/viewtopic.php?p=399929#399929












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dsavarese0812(at)bellsout
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PostPosted: Sat May 04, 2013 5:48 am    Post subject: yak 55 engine surge, in flight Reply with quote

Actually the larger chunks of rubber never made it into the finger screen. Only smaller pieces were in the screen. The larger pieces were lodged in the interior end of the finger screen orifice where it makes a 90 degree turn. I had to remove the plate on the outside of the carburetor to gain access to the area where the larger chunks of rubber were lodged.
Dennis

On May 3, 2013, at 9:15 PM, "Roger Kemp M.D." <viperdoc(at)mindspring.com> wrote:

Quote:


A 6 mm and a 4 mm fragment of the inner liner of the main fuel line to the carb. We found it in the finger screen in the carb. It is not uncommon to have a small amount of fuel drip out of the carb after shutdown especially if you do not advance the throttle to wide open just as you cut the mags off. I am by no means an expert on the carb.
Doc

Sent from my iPad

On May 3, 2013, at 8:43 PM, "Epistaxis" <ShawnJBurwell(at)aol.com> wrote:

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> Doc, thanks for the response, could you please clarify where you found sections of the flapper valve, which filter IE...course or fine on the firewall or in the carb inlet course screen, and was this part of the emergency fuel shut off flap. In addition, this evening after returning to the hanger and after the test flight this afternoon have found fuel dripping from and around the spray bar in the carb venturi. Thanks
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Dale



Joined: 30 May 2007
Posts: 178

PostPosted: Sun May 05, 2013 5:08 pm    Post subject: Re: yak 55 engine surge, in flight Reply with quote

had this happen to me at a airshow formation flight, turned out to be the prop governor . Surged at all 70% and higher power settings but was barely noticeable at lower power settings. i replaced it and my problem went away.

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