Seneca II, partial engine failure and leaning...

dans2992

dans2992

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Dans2992
So I just finished my Commercial Multi.

During a training flight, just after rotation at about 150ft AGL, the left engine started varying in RPM between 1000 and 2500 about once per second. RPM gauge thrashing back and forth, obvious power loss.

At first I thought it may have been a "simulated" emergency, but then realized it wasn't. Going through "identify, verify, feather", as I brought the throttle back for "verify" things smoothed out as I got back to 20 inches. (Takeoff power is 40 inches)

As long as it was making partial power, we decided to stop troubleshooting and get back on the ground. We came around the pattern (at 500' AGL) and landed.

The instructor mentioned seeing the fuel flow needle make a full circle around the gauge! Turns out the fuel controller was not set properly and was giving the engine _way_ too much gas at full throttle.

This was the second flight after an extensive annual. The problem was apparently "masked" on the first flight because the owner of the flight school had "leaned it a bit" for takeoff. He said "everyone knows you lean for takeoff".

Well, that's contrary to the POH and everything I've ever read. The engine is turbocharged making 40-inches and we're talking about an airport around 1000 MSL.

Does anyone have any idea where he might have gotten this idea?

After the fuel issue was fixed, there was some comment made like "well, if you guys had leaned like you were supposed to....". Blah blah blah.
 
The owner of the flight school is an idiot. Find someone else's planes to fly (but take that instructor with you, as he made a good decision in the actual event).
 
Ron is quite right about the owner...

The 'kota has the same base engine (-FB instead of the -EB on the Seneca). Do not lean for full power operation. The POH says it very clearly. The fuel controller should be set by the book and the engine should give book power. If it doesn't then it's time to find out what is wrong. If folks have been leaning for departure then the cylinders have been cooked and I'd hate to see what the top of the piston looks like.
 
I agree, the guy is an idiot! I used to have to lean my 421 for run ups, not a lot, but otherwise it was too rich and the mag check would create a larger drop on the left side than the right. :rolleyes: But, I have never leaned a turbocharger airplane for takeoff. I think the highest I ever departed was Colorado Springs, it's something around 5-6K MSL, but it was full rich. Turbocharged engines need that fuel for cooling.:D
 
Now this is coming from a guy who doesn't have his multi yet, but power rapidly going from full bore to almost nothing in less than a second sounds like a real problem, I would think that at 150 AGL you'd want to get up up and away. I feel like I'd have taken any power I could get and have left that mother at max power until I hit 500 AGL. (I realize the OP restored smooth operation by bringing the MAP back to 20" but let's pretend that didn't do anything)

How wrong am I for thinking this?
 
I was getting more power out of the engine at 20 inches running smoothly than I was while it was full power for 1 second, zero power the next, full power for the next 1 sec, etc.
 
dans2992 said:
I was getting more power out of the engine at 20 inches running smoothly than I was while it was full power for 1 second, zero power the next, full power for the next 1 sec, etc.
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I'd imagine the yaw control was a whole lot better, too.
 
CA.... Get your ME and you will answer your own question.
Too long to go into here, but the OP handled it perfectly.
 
I remember reading about a 210 owner who refused to repair/replace the worn sloppy linkages on his fuel control because he was able to "compensate" via the mixture control. One day he was unable to compensate quick enough....

Fortunately he was the only fatality and no others were injured. The NTSB questioned several of his friends who confirmed something was wrong with airplane as it briefly lost power when they received a ride in it.

Pure negligence. I'll look for that report later.
 
With normally aspirated engines, one should lean for takeoff if the DA is high (i.e. above about 4000 ft) and normally turbocharged engines don't require leaning for DA. But the stock engine in a Seneca II have a fixed wastegate and the power drops off when you're high enough that full throttle won't produce max rated MAP and well above that I think leaning would make sense. Seem like a moot point though.
 
gismo said:
With normally aspirated engines, one should lean for takeoff if the DA is high (i.e. above about 4000 ft) and normally turbocharged engines don't require leaning for DA. But the stock engine in a Seneca II have a fixed wastegate and the power drops off when you're high enough that full throttle won't produce max rated MAP and well above that I think leaning would make sense. Seem like a moot point though.
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Critical altitude for the fixed waste gate TSIO-360-FB is 14,000' IIRC. Really moot point unless you happen to be in the Andes or Hindu Kush. The fuel controller has altitude compensation anyway...
 
Clark1961 said:
Critical altitude for the fixed waste gate TSIO-360-FB is 14,000' IIRC. Really moot point unless you happen to be in the Andes or Hindu Kush.
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Kinda what I figured.
The fuel controller has altitude compensation anyway...
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Kinda what I figured. [/QUOTE]
So does the mixture remain constant as you climb above the critical altitude?
 
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gismo said:
Kinda what I figured.

Kinda what I figured.
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So does the mixture remain constant as you climb above the critical altitude?[/QUOTE]

I don't know. The Merlyn upper deck pressure controller (read some sort of abomination of a sorta-automatic wastegate controller) raised the critical altitude to 18,000' on the 'kota.

I know that I don't have to futze with the mixture once it is set, just keep opening the throttle during the climb. Don't go above 18,000 much (as in never).
 
Clark1961 said:
I don't know. The Merlyn upper deck pressure controller (read some sort of abomination of a sorta-automatic wastegate controller) raised the critical altitude to 18,000' on the 'kota.

I know that I don't have to futze with the mixture once it is set, just keep opening the throttle during the climb. Don't go above 18,000 much (as in never).
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That Merlyn setup is definitely the way to go with a TSIO360 but I didn't realize that is what you were referring to. With the OEM fixed wastegate I don't think there's a "critical altitude" and I suspect that leaning might be required well below 14000 but I don't remember that clearly and it's been beaucoup years since I flew in a Turbo Arrow.
 
gismo said:
That Merlyn setup is definitely the way to go with a TSIO360 but I didn't realize that is what you were referring to. With the OEM fixed wastegate I don't think there's a "critical altitude" and I suspect that leaning might be required well below 14000 but I don't remember that clearly and it's been beaucoup years since I flew in a Turbo Arrow.
Click to expand...

Just reviewed the POH, critical altitude with the fixed wastegate is 12,000. The Merlyn takes it up to 18,000.
 
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