M61A1

My best explanation would be that when you put more fuel in than the engine Can use, there is more unburned fuel leaving through the Exhaust.

It has been good to see that the responses are generally the same as the path I took. While working on it, I knocked the exhaust pipe with my knee and thought I heard a faint rattle. I gave it a thump on the side and sure enough something was adrift inside the muffler can. I cut the end off and found a largish piece of baffle had been floating about in there. The design of the can allowed the piece to partially block the outlet and likely one side of the can at times depending on where it got stuck. I was likely the rattle heard at idle was the loose piece, but it wasn't audible from the cockpit. A big sigh of relief as I've got a solid fault to work with. The exhaust was removed, a welded repair was carried out and re-installed The aircraft was ground run and test flown with no further problems. A borescope up the muffler will become part of my 50 hr inspections.

Power certainly did drop, fortunately being a hot day there was plenty of lift about. I had fresh 98 in it, and then put some fresh 100LL in it. Filter is clean. Float bowls clean and correct levels. CHT was normal for the weather, EGTs may have indicated differently if they were fitted, but this installation has none. I didn't even think of that, but probably because there were no weird noises when turning by hand. I have experienced this also, but only at idle. Float bowls were checked immediately after shutdown when the abrupt power drop occurred on ground run. No anomalies were found. I thought that also and the carbs and fuel system were the focus of my troubleshooting. Cables and stops have been checked and rechecked. Slides, diaphragms, needles and spring lengths checked and rechecked also. Everything seems to point carbs or induction. I'm just about tearing my hair out because I can't find a solid fault and I was planning to fly out at first light.

It has pod filters which are in good condition and it is in the high 20's low 30's in temp with about 25% humidity.

I will add at this time an acquaintance came over when I was faultfinding and leaned on the prop. He then started moving the prop back and forwards listening to the tiny amount of backlash in the gears and commented that he could hear that when it was idling. It's not the problem but it's a clue.

Mags checked out serv. Wiring all good. Intermittent problem still there

Checked as well. No fault found.

Both checked, just to rule out. Exactly what I thought.....Pod filters fitted. even swapped them with another set. After checking plugs it was noted that both sets on the left hand side were sooty while the ones on the right were normal. So float levels were checked, needles and seats tested and floats replaced with a spare set and float bowl vents and galleries were cleaned with compressed air. Also slide diaphragms and needles were inspected with no faults found as part of troubleshooting. All with no result. Then during a ground run there was an abrupt power reduction at full throttle, a mixture reading less than 10:1 (it only reads between 10 and 20:1) while still idling normally and low power operation normal (including air/fuel ratio)).

How about an actual problem? I had this issue a couple of weeks ago. The aircraft has a Rotax 912 with standard Bings with vent hoses as per Rotax instruction. The installation is pretty normal. A single throttle cable from the dual throttle linkage to a splitter which goes to each carb. The installation has an Air/Fuel Ratio gauge fitted. A let over from some previous testing. The exhaust is not standard Rotax but appears similar in design. Engine mounts are standard for the aircraft design, which has a bed mount. The whole installation has been functioning normally for around 400 hours. One afternoon on a normal sort of day with a normal takeoff, about mile from the strip, I reduce the throttle to cruise at 5200 RPM. Moments later power drops to 4800 RPM. After turning back immediately I cycle the throttle a little and find that 4800 RPM is all I'm going to get and the mixture is extremely rich at high power settings. If I reduce power the mixture returns to normal levels. After landing the engine idles and throttles up normally, but will not produce power above 4800RPM. After shutdown ( having a check under the cowl at various bits) and restarting everything appears to run normally, including ground run, but does the same again after taking off. I fixed it after four hours of troubleshooting and multiple ground runs and test flights. Any takers?

Oakey says PPR on ERSA. When I phoned ops to get permission, the standard answer is "You can't". They gave up some of their airspace when Wellcamp opened. Now the are very protective of what they have left. At least the deactivate on weekends and usually for 2 hours late afternoon.

Pretty sure you don't want to know what it made me think....😵

Why.....It's the simplest and most logical reason for indicated speed not matching ground speed. You said it a simple solution.

This could cause me some issues.....I frequently use my prop as a brake.😱

The content was perfectly comprehensible. You just didn't write what you actually meant.

RPM should still be 2300 ( constant speed), manifold pressure should slightly lower as the as the engine would have unloaded slightly when the prop fined up to compensate unless the pilot increased power to compensate for reduced airspeed, in which case the manifold pressure would be higher. That would be my best guess. I’m not educated on constant speed props, ask me about helicopters and I may be more helpful.

It's either MIB or DR Evil....Both of those use them. I saw it on telly.

Check the wind. Power loss would have been noticed the moment it occurred.

Either the tach was switched over to a different setting or you are getting extra signals from other cables with AC or other plug leads.

I have experienced this exact situation when cross checking another altimeter in flight. I have two instruments that read airspeed and disconnected the static off one to connect to the altimeter being tested. It was noted immediately that the ASI with cockpit static pressure was overreading significantly compare to the one with a proper static port and the GPS.... Virtually this exact scenario.

Don't feel a failure. The failure occurred when the question was written. Not when it was answered. I have had an instructor that used to asked such vague and broad questions. it seemed as that way he could always be right and you would always be wrong, because the answer could be whatever he wanted it to be.

I was going to make no further comment but, you've demonstrated clearly your own lack of understanding....You stated that the ASI was reading exactly where it should and that the ground speed was slightly less than than anticipated, which rules out the engine straight away. Then in your explanation you tell us that you have a lower airspeed....contradicting what was said previously. This is nothing to do with Occam's Razor, and there would have been a more clues than a couple of knots of missing ground speed. Next time I'll know better and not bother.

Maybe you really should write exam questions for CASA....They are always written in a vague manner with little relevance to the real world. I won't be giving it any more thought. I have actual things to fix.

That if it gets any worse you might actually take a look at the static system and do a leak check and cal your ASI at your next service. If you consider it enough of a problem, the answer would lie somewhere in the static system or the GPS. Since the GPS is unlikely, that leaves the static system. You can leak check the static system which will lead the a leak in the aircraft plumbing or a fault with the instrument. Depending on the aircraft type the little sleeve on the pitot used to calibrate the static system could have moved.

You could get a job writing CASA exam questions OME.