Discuss the problems and solutions to all of the situations that Pilot X finds himself in.
"Are we going in?" Paul asked.
"I think so" I responded.

All engine parameters were good and correct.
I opened the throttle 3/4 full before releasing the brakes and going all the way... Probably just as well as if I'd held it at full throttle for a time maybe the power loss would have occurred sooner/lower.

She lifted off easy one third of the way down the runway, situation normal, power pressure and temperatures all good.
Then at 150 feet the airspeed reduced to between 50 and 55 KIAS and so I lowered the nose and flew level.

A look at the engine gauges showed more than 28 inches manifold pressure, and maximum RPM, but there was too little power to climb.

At 65KIAS I looked for where I might go...
But she was still inching up very slowly and we would reach around 350 feet AGL before landing.

With enough power I carefully turned to field after field, not much choice with only small fields.
I flew a wide circuit as this gave me more choices of suitable places to crash.

I throttled back and there was no change in performance and so elected to leave the throttle wide open.
The engine ran best with carb heat selected, but carb icing was not the problem.
I believe that the fuel flow was insufficient, a blockage had occurred, and carb heat enrichened the mixture. Perhaps a lower throttle setting would solve the issue, matching power setting to fuel flow, but I did not play with this, my concentration was on crash site to crash site as I inched us around to finally turn final for the same runway we had taken off from (no turn back, one complete wide field in mind in mind in mind circuit to land in the same direction).
The landing was uneventful.

The electric fuel pump was on and the flaps were set in the T/O position all the way.
I brought the propeller back to the top of the green range, but this made no difference.

With the throttle fully open the manifold pressure remained above 28", and at 65KIAS the propeller maintained max/top of green RPM, but there was insufficient power to climb.
These guides do not give you a true indication of power if there's insufficient fuel getting into the engine.

Perhaps at 50% power or so the propeller will maintain the max RPM at 65KIAS.
With the throttle full open the manifold pressure will be similar to outside static pressure plus any ram effect.

I have my theories on what the problem may be.
A newer mechanical fuel pump has been fitted...
The carburettor floats are likely to be 'pre mod'.
There's likely to be a restriction in the fuel system.

I had a similar problem with G BIOW just after I got it.
It turned out there was scum in the carburettor fuel inlet gauze filter that occasionally blocked fuel flow causing anxious moments as the pilot pumped the throttle home.
This was easily rectified with a blow or air to clear the filter.
User avatar
By MichaelP
Slightly rough, and I wondered whether fuel flow reduction effected one or both carbs.
At high RPM the engines' roughness is reduced.

There's a sense that carb icing is a problem with the Rotax engines here, because application of carb heat solves some roughness, but now I wonder whether it's a fuel flow/lean mixture issue some here experience.

I was not able to stay around to see the problem solved today.
Sometimes a 'Pilot' is not welcome...
User avatar
By Keef
This one puzzles me.

At a given MP, a defined power output is needed to hold a particular RPM in level flight (unless there's a VP prop, which in this case seems unlikely). If the power reduces and MP stays the same, the aircraft will need to descend to hold RPM.

I'll be interested to hear the diagnosis.
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By Paul_Sengupta
Um, I'd have thought it would have to be a VP prop.

Rotax? Carbs? Another guess would be Marj's carb rubber split/detachment.
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By Charles Hunt
'It happened to me' rather than 'That Worst Day' ??
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By MichaelP
The Katana has a constant speed propeller and so limited power, enough to fly at 65KIAS, was enough for the CSU to maintain max RPM.

Yesterday we had fuel pouring out of the carb air intake with the fuel pump on and the throttle open... Stuck float valve, opposite problem to what I experienced.
I'm told the engine has been fixed now and the aeroplane has had two test flights... We'll see tomorrow.

Of course I will once again preset my mind with the takeoff safety brief... If I go flying 8) I'll look at the engine first.