RV6 O-360 loss of power on takeoff

[SkyDweller]

A friend of mine had experienced an intermittent power loss on takeoff today (landed safely). Will outline below. O-360 with dual Pmags and CS prop.

After the failure and some checks he performed multiple full power run ups and everything was normal.

ANY recommendations on other items to check would be appreciated.

- complete loss of power at around 300’ AGL
- partial power returned just enough to get him over the trees to safety.
- electric boost pump was not on during takeoff

We spent the day looking over things in an attempt to identify the cause.

- tanks were sumped before flight, but we sumped both again multiple times including raising the tail in an attempt to drain any remnant of water which might have been behind the sump.
- checked for pressure and vacuum on inlet and outlet of engine driven fuel pump
- checked all linkages for throttle/mixture
- pulled all plugs and ohm checked leads
- checked gascolator

 

[JonJay]

EMS data available?

 

[1bigdog]

A friend of mine had experienced an intermittent power loss on takeoff today (landed safely). Will outline below. O-360 with dual Pmags and CS prop.

After the failure and some checks he performed multiple full power run ups and everything was normal.

ANY recommendations on other items to check would be appreciated.

- complete loss of power at around 300’ AGL
- partial power returned just enough to get him over the trees to safety.
- electric boost pump was not on during takeoff

We spent the day looking over things in an attempt to identify the cause.

- tanks were sumped before flight, but we sumped both again multiple times including raising the tail in an attempt to drain any remnant of water which might have been behind the sump.
- checked for pressure and vacuum on inlet and outlet of engine driven fuel pump
- checked all linkages for throttle/mixture
- pulled all plugs and ohm checked leads
- checked gascolator

I would think a fuel flow test at climb attitude would make sense as a starting point. Good luck.

 

[Avanza]

A friend of mine had experienced an intermittent power loss on takeoff today (landed safely). Will outline below. O-360 with dual Pmags and CS prop.

After the failure and some checks he performed multiple full power run ups and everything was normal.

ANY recommendations on other items to check would be appreciated.

- complete loss of power at around 300’ AGL
- partial power returned just enough to get him over the trees to safety.
- electric boost pump was not on during takeoff

We spent the day looking over things in an attempt to identify the cause.

- tanks were sumped before flight, but we sumped both again multiple times including raising the tail in an attempt to drain any remnant of water which might have been behind the sump.
- checked for pressure and vacuum on inlet and outlet of engine driven fuel pump
- checked all linkages for throttle/mixture
- pulled all plugs and ohm checked leads
- checked gascolator

I think that the powerloss is fuel related. A simultanius problem with both Pmags at the same time is highly unlikly. But check key ignition switch.
Check carb fuel inlet strainer.
At full throthle carb ice is not expected but this can not be rouled oute. How was the weather, cold wet climate ? Previous experience of carb ice ?
Check alternate air function.
More than 10 year since carb overhaul ? If so, this is a god idea.
If all checks out OK, on the first 5 flights let engine run until warm on ground and perform run up just before take of.

Good luck

 

[WillG]

I've had similar situation - twice, until I changed to better than Van's carb heat muff. O320 160HP.
Might put that on the list of possibilities.

 

[Roy Thoma]

When were the fuel tanks built? “Slosh” was recommended during early RV years.

I recently heard a story about an RV that had multiple engine stoppages with many hours between the stoppages. Ignition and fuel components were replaced between stoppages and the problem seemed fixed, until it returned tens of hours later. Turned out to be loose “slosh” in a tank that would block the fuel pickup.

Regards,

 

[paulsmeds]

Sounds like a partially blocked fuel flow as others mention. You didn't mention that you switched tanks with the fuel selector. Just a thought but a mostly blocked line from one tank to the selector could cause what is happening. Restricted flow allows for the carb bowl to supply enough fuel to the engine to run for the taxi, run up and even full power for short time. But full power for a longer time , the restricted flow can't keep up starving the engine of fuel. Would cause a momentary loss of power and restore as the bowl fills again. Throttle back and it could even run okay because the line is not fully blocked. Just a thought. Switch tanks and keep a close eye on the fuel pressure to see if it goes way down with full power.

 

[apivovarov]

Items to check
1. Fuel System Check
- Fuel Pickup Lines & Fuel Screen: Inspect these for any potential obstruction. Sometimes, even a small piece of debris or an internal line collapse can intermittently obstruct fuel flow.
- Fuel Venting: Blocked or partially obstructed fuel tank vents can restrict fuel flow, particularly under high demand. Ensure all vents are clear and functional.
- Electric Boost Pump Operation: Since the electric boost pump wasn’t engaged during takeoff, it could be beneficial to test takeoffs with it active to see if there’s a performance difference, though it shouldn’t generally be required.

2. Ignition System
- Ignition Cutoff & Grounding: Ensure all ignition grounding wires and cutoffs are solid. An intermittent short could momentarily cut spark to one or both mags.

3. Vapor Lock or Cavitation
vapor lock or fuel cavitation could happen if fuel lines are exposed to high heat. Though less common, especially with an O-360

4. It can be very useful to completely drain the fuel tanks (with the tail up) to see what comes out, especially if there’s suspicion of contamination or water in the fuel.

Additional information
To get a clearer picture of the cause, the following details from the owner could be valuable:

Fuel Information:
When and where was the fuel last purchased? Any recent fuel contamination issues reported at that location?
How much fuel was onboard at takeoff? This might help assess if fuel sloshing or low levels played a role.

Pre-Takeoff Observations:
Were there any unusual sounds, vibrations, or indications during engine startup, taxi, or run-up?
Was there a notable temperature or humidity condition that could impact fuel vaporization?

Behavior of Instruments During the Power Loss:
Did any engine instruments (RPM, fuel pressure, manifold pressure, or EGT) show abnormal readings right before or during the power loss?
Was there any warning light, or did any gauge suddenly drop, fluctuate, or spike?

Power Recovery Details:
Was the power recovery gradual or sudden, and how long did it take to stabilize? This can provide clues as to whether the issue was fuel, ignition, or airflow-related.
Did adjusting the throttle or mixture control help restore power, or was it unrelated to any control input?

Environmental and Load Factors:
What was the aircraft’s weight and balance at takeoff? High loads could exacerbate any marginal power loss issue.
Were there any unusual weather conditions (e.g., strong crosswinds, turbulence) that might have impacted airflow into the intake?

Post-Flight Observations:
Did the owner notice any fuel leaks, unusual odors, or other signs of fuel system abnormalities after landing?
Any fluctuations or odd behaviors during subsequent high-power ground tests?

 

[PhatRV]

You need to download the EFIS or EMS data and analyze

 

[turbo]

check your engine data and get a wobble test done. Robinson helo mechanics do the wobble check every 300 hours as a SB on the Robinson engines. they know the weak part of the lyc we fly behind.

 

[Carl Froehlich]

In addition to the previous comments:
- Running 100LL or Mogas?
- Fuel selector valve in the proper position?
- Any crud in the gascolator filter when you inspected it?
- Any crud in the carb inlet strainer?
- Why no boost pump on takeoff?
- EMS data on fuel pressure, CHTs and EGTs would be helpful.

Carl

 

[fixnflyguy]

Make sure the a fuel pick-up tube hasn't come loose. Happened to a friends RV-8 and it was drawing fuel from the tube only when fully submerged to the B-nut. His scenario was similar, but that's dependent on how the fuel tube is routed. he did it twice, made it back to field dead stick both times. Engine quit just as he leveled off in his case. I had him sit in cockpit on the ground, turn on boost pump while I lifted tail.. pump cavitated about the time I hit "level" attitude. This was only on one tank, and he never switched on his flame out and tried re-start. Upon tank open-up, the fuel pick up anti-rotation/B-nut safety had never been done and it had loosened and moved.. Could have been a much worse outcome.

 

[blaplante]

Upon tank open-up, the fuel pick up anti-rotation/B-nut safety had never been done and it had loosened and moved.. Could have been a much worse outcome.

Did the airframe logs reflect SB 06-2-23 having been done, or not? In buying a used plane, if the airframe log doesn't have an entry for this we have to assume it wasn't done, inspect, and enter the inspection into the log. The job isn't done until the paperwork is complete!

 

[fixnflyguy]

Did the airframe logs reflect SB 06-2-23 having been done, or not? In buying a used plane, if the airframe log doesn't have an entry for this we have to assume it wasn't done, inspect, and enter the inspection into the log. The job isn't done until the paperwork is complete!

I didn't do the routine maintenance on that particular RV-8 and the owner wasn't the builder. He is based at same airport as me, and has had a couple RV's..come to think of it, it was his RV-4, not his RV-8. I built mine, and I'm also an APIA that maintains a bunch of local birds, certified and experimental. I'm sure many other APIA's can attest, there are plenty of airplanes that don't have the documentation the think they do...especially the EXP's. The fuel tank SB's are not user friendly to do with tanks on, nor mandated by regs. Many a builder incorporated the "change/SB" during their build and didn't specifically document such, however, the wonderful selection of inexpensive and small borescopes makes things a bunch easier on owners and techs to find out what's been complied with vs. what's not without complete disassembly.

 

[HotRod6A]

I found aluminum trash from tank construction on the inlet of my boost pump, something to check! There should be a coarse screen on the fuel pickups, but these slivers where able to get past. Vapor lock is real with these tight cowled planes, if the lost of power was on quick turnaround like getting fuel and taking off again then this is when vapor lock potential increases, boost pump certainly helps mitigate.

 

[SkyDweller]

Thank you everyone for the responses. Very good recommendations here! Fuel tank was removed and various components inspected fully, but without any surprises. Engine and components are high time (slightly over TBO, but definitely over on age) and he has opted to go ahead with a full overhaul.

Lead times and prices are insane now. While I had always planned on pushing things beyond TBO as long as my compressions and oil analysis were good, you run the risk of many months or even over a year of being grounded. After watching him enter this experience, I’m considering lining up my overhaul sooner than later just to ensure I don’t have a large and somewhat heavy paperweight in the hangar. If it took me a year to get my own plane back in the air that’s almost $14,000 worth of hangar fees and insurance wasted to not even be able to fly!

Keep those engine funds growing and plan ahead!

 

[rockyfatcat]

Thank you everyone for the responses. Very good recommendations here! Fuel tank was removed and various components inspected fully, but without any surprises. Engine and components are high time (slightly over TBO, but definitely over on age) and he has opted to go ahead with a full overhaul.

Lead times and prices are insane now. While I had always planned on pushing things beyond TBO as long as my compressions and oil analysis were good, you run the risk of many months or even over a year of being grounded. After watching him enter this experience, I’m considering lining up my overhaul sooner than later just to ensure I don’t have a large and somewhat heavy paperweight in the hangar. If it took me a year to get my own plane back in the air that’s almost $14,000 worth of hangar fees and insurance wasted to not even be able to fly!

Keep those engine funds growing and plan ahead!

Loss of power on takeoff isn’t going to get fixed by overhaul. People regularly fly motors 2-3 times recommended TBO. Do some real troubleshooting on fuel delivery and ignition.

If the engine has good compression and isn’t making metal you are headed down the wrong path.

If you transfer everything you have on this engine onto a brand new engine and it does the same thing. How much money did you spend not troubleshooting?

 

[georgemohr]

Others have said this already, but if you have an EFIS you must start with the data download. You'll see a fuel flow drop, or an MP drop, or something that will lead you to the problem.

 

[rockyfatcat]

Loss of power on takeoff isn’t going to get fixed by overhaul. People regularly fly motors 2-3 times recommended TBO. Do some real troubleshooting on fuel delivery and ignition.

If the engine has good compression and isn’t making metal you are headed down the wrong path.

If you transfer everything you have on this engine onto a brand new engine and it does the same thing. How much money did you spend not troubleshooting?

I had a intermittent situation on my certified aircraft where I would do a full run up including a max takeoff power test. Occasionally he engine would stumble before I reached the first turn off.

I would abort. Do another full run up and try again. Usually that would clear things up. Leaving me to think:
Engine not warm enough?
Plugs fouled?
Ice in the intake?

The last time it did this the second run up didn’t clear things up and I took it back to the barn and pulled all 8 plugs. They didn’t look bad. They only had about a hundred hours on them.

My hangar mate has a spark plug testing machine. I tested all the plugs and for whatever reason, when the pressure was dialed up to 80 psi, some of the plugs quit making spark.

I drove to Aircraft Spruce and bought, gapped, and installed 8 new plugs.

As Harry Potter would say “mischief managed”!

A new set of plugs is cheap. Do you have someone who can test your magnetos? Can you ohm out your plug wires? Have you verified fuel pressure? Cleaned your gascoalator recently?

Find a better mechanic, to do some more troubleshooting. You could replace every bit of your fuel delivery and ignition system for a fraction of the cost of a new motor.

 

[airguy]

Unfortunately, since the decision is already made to overhaul the motor, we will probably never get down to the bottom of this.

 

[blaplante]

Unless it happens again on the overhauled engine. Which unfortunately I give 50/50 odds.