DHC2 Misfiring

[ldufferin]

Does anydoby knows why my Beaver is doing some Misfires while in flight after a little while?

Any suggestions?

[shimmydampner]

Bringing up important maintenance issues to your engineer is probably an infinitely better idea than consulting an anonymous internet forum.

[CpnCrunch]

but not as entertaining.

[cdnpilot77]

K.Y?

[ldufferin]

Thank you but i m just trying to help the engineers, that s it.
So if u already had that kind of problem, please let me know.

Cheers

[Keenflyer]

Power settings? Type of miss? Change of supply of fuel? Been wet and very humid lately? How old the plugs? How many hours on the engine? Did they use old mag/plug leads when rebuilt? How log since the mags were looked at? What's the oil burn? Has it got an auto carb? If not how do you set the mixture when you change power settings?
Is this a joke? Windup?
One possibility is testicle resonance interfering with the sinewave polarity on the carbon rectifier leading to a disassociation of the beta pulses inducing an out of sync intersegmental core disequilibrium. Do you hum when you fly?

[Heliian]

Your engine is telling you it's about to fail, stop flying it until the problem is found.

[Doc]

Your engine is telling you it's about to fail, stop flying it until the problem is found.

My gawd.....the correct answer!

[frozen solid]

Your engine is telling you it's about to fail, stop flying it until the problem is found.

My gawd.....the correct answer!

Bingo. Turn it in to the engineers, mumble something about "glowing carbon particles" and refuse to test-fly it for as long as you can get away with.

[kevinsky18]

I had this issue a many years ago while flying my first Beaver gig in Northern Saskatchewan. The engine coughed and then caught in about a one second hesitation. Definitely woke me up and when I landed I informed the engineers. They had a quick look at fuel filters, timing etc, couldn't find anything and responded that "Beaver sometimes do that." I wasn't happy with the answer but they didn't seem at all concerned.

I continued flying the plane and about 4 days later it coughed again this time about a 2 second hesitation. Again back to the engineers who couldn't find anything and said it was all part of normal Beaver operations. It happened maybe one more time after that for a two second burst.

Then one day it coughed and the prop started to windmill. Long enough that I had my emergency landing spot picked out and I was setting up on a base leg when the engine sputtered back to life again. I returned to base and refused to fly the plane until the issue was resolved. I believe it was some sort of weird issue going on with the mags apparently both of them where affected. After that the plane ran smoothly and never coughed again for the remainder of the time I flew it. Since then I've flown close to a thousand hours on many different Beavers for several different companies and to date I've never had a Beaver cough like that again.

If you're using the prescribed amount of carb heat and are sure it's not carb ice then I would make sure you are 100% satisfied with the resolution you get from your mechanic.

[Swampdonk]

kevinsky18, sounds like the firewall cannon plug problem

[xsbank]

I had one cough, grounded it, they changed the entire ignition system and about an hour later, the master rod let go and it seized up solid.

It's broken. Don't fly it.

[zero]

Had one misfiring on me a few years ago in heavy rain...west coast heavy rain! Took another occurrence to get the engineers serious about it and found moisture was getting into a mag/mag wiring, problem solved.

[GyvAir]

I had one cough, grounded it, they changed the entire ignition system and about an hour later, the master rod let go and it seized up solid.

It's broken. Don't fly it.

Would a master rod or any connecting rod thinking of letting go give any warning, in particular in the form of misfiring/coughing/rough running?
Maybe I'm not clear on the connection you're making. (no pun or sarcasm intended)

[Colonel Sanders]

Would a master rod or any connecting rod thinking of letting go give any warning, in particular in the form of misfiring

I didn't get that either. I would have probably looked
at one of these first:

1) fuel/air problem. Not combustible mixture.
2) ignition. No/weak spark.
3) sticking valve. Combustion chamber not sealed.

But I was dropped on my head as a small child, when
I was taught that the top end makes the power, and
the bottom end takes the power.

[Heliian]

It could be almost anything, from something as simple as wiring/shorting to a broken baffle floating around half blocking the intake, maybe non sodium filled valves. A bent but not failed rod could present itself that way too, you answered your own question CS

Combustion chamber not sealed.

Start with the easy ones and work your way up till you find the problem.

When something has absolutely failed then it's easy, intermittent problems require much more work to diagnose and repair.

My experience has shown me that these beasts will almost always warn you of their impending failure, it's whether or not you're able to hear them that makes the difference.

[Colonel Sanders]

Start with the easy ones and work your way up till you find the problem

I start with the cheap stuff and work my way
up to the expensive stuff

Corollary of the above: if I'm looking at a 50
year old worn part that I'm not sure it's working
or not, and it costs $10, it's going in the trash can.

It's paid for, and if I don't replace it now, I'm
probably going to have to replace it later. Not
worth spending hours diagnosing or repairing.

[NeverBlue]

But I was dropped on my head as a small child, when
I was taught that the top end makes the power, and
the bottom end takes the power.

...so dry...too funny Colonel

[Heliian]

As far as just randomly changing parts because they're cheap is fine for you, but you can't do that to your customers. And I can't think of too many $10 parts in that system. God forbid someone takes the time to do a job properly. I'd be interested to know what the outcome was with this case, if simple parts changing fixed it or if they had to actually investigate and test and repair. If you don't want to "waste" any time at all, just change the mags and the rest of the engine, if the problem comes back then it must be the switch.


And yes, we know you were dropped on your head as a child and aren't very smart. (your own words, ad nauseum)

[pelmet]

My experience has shown me that these beasts will almost always warn you of their impending failure, it's whether or not you're able to hear them that makes the difference.

Personally, I think most engine types can give a warning. One time just before taking off in a turboprop with dart engines, the captain asked if I could feel a vibration occasionally rumble through. I had not noticed until he asked but yes, I could feel it through the seat. Thought it might be a prop imbalance.

But, everything else seemed normal so we took off from a not particularly nice departure routing actually. Anyways, on descent about 40 minutes later, the thing just autofeathered on us. A complete mechanical failure with an engine overheat light. The prop was completely seized when checked after shutdown. Turbines may give notice as well of impending mechanical failure.