Jump to content

CTSW Surging


tevbax

Recommended Posts

Finally got all the BRS mess wrapped up and went for a test flight last night. Full power on departure, other than trim being way out of whack, it flew great! So, grabbed a friend and went back up for a longer flight. He's getting used to the plane, so did a series of steep turns, flew past our homes, and headed back to the airport. Engine was running at approx 4800 RPM. Then, the surging started. Engine RPM would drop to 3200 then back to 4500 back to 3200 back to 4800 - like a timed oscillation. The engine did run fine at idle for the landing with no sign of issues. 

This plane has had the carbs rebuilt, linked and synced. Annual was just done in March. Previous owner ran only 91 non-ethanol fuel. All AD's and SB's have been completed. Vents are all facing forward, and fuel is water free/ contaminant free through the gascolator. 

Any ideas on where to start looking? My first thought is something floating around in the float bowls. Since the main was active during the surge, and it idled fine, that kind of tells me that something was plugging the main. Run up after on the ground revealed no surging or hesitation. 

Video link below - watch the tach. 


CTSW - 2006

Rotax 912 ULS


Video

P.S. Don't judge the landing

Link to comment
Share on other sites

So, here's an interesting turn. I talked with Brett @ Leading Edge at Airventure. When our mechanic put our carbs back together from Leading edge, he neglected to hook up the carb balance tube that runs through the airbox. The tubes that are on the carbs were exactly where Leading edge left them - in the hangers that hold the float bowls on. 

Heading to the airport tonight to reattach the balance tube. Carb bowls were absolutely spotless with NO sign of residue or debris. 

 

Link to comment
Share on other sites

That will absolutely cause funky issues. Depending on airspeed and AoA, there can be fluctuations in pressure under the cowl which will affect the fuel flow through the jets. Good catch.

Fortunately that wouldn't necessarily result in harm, you likely wouldn't have lost power completely, but certainly scary.

Link to comment
Share on other sites

Unfortunately when using text, emails or anything in print you get a story, but maybe not all small details and you just have to assume something’s are in place or have already been done. This is why I usually prefer phone calls. It’s usually quicker and far more informative.

Link to comment
Share on other sites

1 hour ago, Roger Lee said:

Unfortunately when using text, emails or anything in print you get a story, but maybe not all small details and you just have to assume something’s are in place or have already been done. This is why I usually prefer phone calls. It’s usually quicker and far more informative.

This for me was a detail I knew nothing about. When i asked the A&P what the little plastic tube coming out of the airbox was for, he stated that it held in the air filter. I've had a good laugh this week. Flew the plane last night, no sign of surging. But, only beat the pattern. Ill get a longer flight tomorrow after im done working at Airventure. 

Link to comment
Share on other sites

  • 7 months later...
1 hour ago, Danilo209 said:

Does the teflon tube that connects through the airbox is supposed to have a slit through it to let clean air in?   I'm having stumbling issues with WOT on take off and this is something I'm not sure if its factory or something the PO did. 

The idea is that the vent tube should have the same pressure as the inlet of the filtered air to the carb. Make sure all of the slits in the tube are inside the airbox. If one gets outside it will cause issues.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...