Detonation / Worries?

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jeremywatco

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jeremywatco
Hi All,

First post but been a on/off lurker for a number of years.

Anyways, today had my 210 out and was taking off from a high altitude airport (DA 8000ft). I leaned the mixture during runup 1700 RPM for best power. Because of the high DA and the fully loaded 210 I chose to do a short-field take off. Held the brakes went full throttle, engine started sputtering and shaking pretty good... engine cowling was moving as well. Took me a few seconds to figure out what was happening.. first though was water in gas or flooded engine clearing.. however it didnt go away. I then pulled about 2" of MP off and the motor surged back to life and was fine. Taxied off the runway, went back to runup.. this time leaned at full power and had no more issues.

As soon as I landed back home first stop was the mechanic that services my plane. He explained that I should have only leaned at full power runup as 1700 will cause too lean of a condition and the cylinders would be starved during takeoff. He recommended flying it locally a few times and report back any hiccups at all. If none then he will borescope it at next oil change but didn't seem to think of it being an urgent issue.

My question is this... should I ground the plane and have it inspected or listen to my mechanic (who I trust and is a very good 210 mechanic)? It ran in its "crappy" state for 5-10 seconds.. and it was alarming enough for me to abort take-off.. however it was fine after I corrected the issue.

Thanks
 
Yeah, I’m no mechanic, but his rationale seems pretty sound to me. If you lean the engine at a lower power setting than what’s required for takeoff, than you’re restricting the engine from getting the fuel it needs to make takeoff power.

I’d go full takeoff power, lean accordingly and then see if you still experience problems.
 
Yeah my main worry wasn't doing it again it was what damage did I just do to the engine. It was a very concerning episode.. engine was shaking so much the cowling was moving on top (like someone was inside the engine bay punching it. But what I will do is tomorrow I will go do some pattern work around my local field. Before actually taking off I'll do a few idle to full power run-ups... make sure it still purrs like a kitten.. slightest "that doesnt sound quite right" and its into the shop.
 
first off i am assuming a NA engine.think about this. at a DA of 8000 ft were you at full power? what does the chart say your power was? im going to guess about 65-70 power at best, what does the book say about leaning at lower power settings? the odds of engine damage by over-leaning at 65-70 percent are nil and none.
 
After leaning during the runup, was the mixture ever adjusted for takeoff power? If not, that should be most of your problem.

My ‘technique’ for high density alt takeoffs is to fine-tune the lean during the early part of the full power takeoff. I may start a bit leaner, but still on the rich side of any ‘max power’ position I want to be. Again, we’re not doing any ‘50 degrees lean of peak’ off a monitor, instead, by RPM and engine smoothness.
 
You did not damage the engine.
 
Leaning for Lycoming engines

Regardless of the fuel metering device, fuel management of normally aspirated engines is primarily dependant on the instrumentation available. The method is the same for both fixed- and controllablepitch propellers

For 5,000 feet density altitude and above, or high ambient temperatures, roughness or reduction of power may occur at full rich mixture. The mixture may be adjusted to obtain smooth engine operation. For fixed-pitch propellers, lean to maximum RPM at full throttle prior to takeoff where airports are at 5,000-feet density altitude or higher. Limit operation at full throttle on the ground to a minimum. For direct-drive and for normally aspirated engines with a prop governor, but without fuel flow or EGT, set throttle at full power and lean mixture at maximum RPM with smooth operation of the engine as a deciding factor
 
At 8000 DA it sounds like you just over leaned it.

Where were ya that it’s warm enough out that you calculated that this time of year? Sounds nice.

If you thought you detonated it, you shouldn’t have made a second takeoff attempt. What are you doing committing to a takeoff with a possible deficiency and then asking after you’re home!?

So, now that you’ve flown it home you should already know if the engine is behaving normally by now.

Nobody here is a photograph of your pistons. So... that’s how useful we really are. But I doubt it was detonating. Sounds more like standard fuel starvation stutter and dying from being too lean.
 
Tom-D said:
You probably did more damage to the prop with the stones and debris than the engine.
Always allow the aircraft to accelerate before you add full power. your prop will love you for it
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What @Tom-D says sounds something like and article I read about mountain flying, take off. The author said to lean during TO roll.
 
AKBill said:
What @Tom-D says sounds something like and article I read about mountain flying, take off. The author said to lean during TO roll.
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how many know their aircraft well enough to do the big pull ?

who knows what I am talking about?
 
As a follow-up... Took it out yesterday. Did several full power run ups. Smooth as butter. Did some pattern work, again smooth as butter. Did some close cross country work... ran perfect. I'm going to put this behind me and never make the same mistake twice. I'll have the shop check the cylinders at next oil change (about 10 more hours) and go from there. Thanks for the information.
 
Tom-D said:
how many know their aircraft well enough to do the big pull ?
who knows what I am talking about?
Click to expand...

I did not only a Big Pull, but I did an absolutely Huge Pull today, getting mine out of the hangar. It stumbled a little but I pushed it back in a little, and it was smooth again.
 
jeremywatco said:
As a follow-up... Took it out yesterday. Did several full power run ups. Smooth as butter. Did some pattern work, again smooth as butter. Did some close cross country work... ran perfect. I'm going to put this behind me and never make the same mistake twice. I'll have the shop check the cylinders at next oil change (about 10 more hours) and go from there. Thanks for the information.
Click to expand...

Your call, but based on what you originally posted I wouldn’t have the cylinders scoped.
 
Lachlan said:
With a vernier mixture control, lean for max power @ 1700, then three twists rich = best takeoff power in 99.999% of non-fuel injected O-360 variants.
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That might apply in some cases, but every airplane is a little different and some are a lot different. The geometry of mixture control systems varies widely, and even the internals of carbs or injection servos aren't consistent. Using a rote adjustment that works for one airplane or engine could easily lead to damage in another.
 
denverpilot said:
Full twists or half twists? :)
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Enough to drop about 100rpm. ;)

Worked like a charm on every single normally aspirated engine I flew out of Centennial from 2004 until we moved in late 2016. But, ya know, every airplane is different. Different fuel and different air, ya know? These engines are so incredibly advanced and high tech, right tolerances, advanced space age materials... it’s not like we’re flying behind 1930s tractor engines when we crank up a carbureted O-360. Oh, wait... ;)

Edited fer spelling...
 
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Lachlan said:
With a vernier mixture control, lean for max power @ 1700, then three twists rich = best takeoff power in 99.999% of non-fuel injected O-360 variants.
Click to expand...
I am based above 6000msl and often fly into airports which are higher(KTEX, KALS and others). I learned to do it similar to Lachlan's method. Lean for best power at a runup rpm of 1700-1800. Then go rich a few clicks. I don't do full power ground runups unless troubleshooting a problem, and prefer to have the airplane fully configured for takeoff (including mixture setting) prior to the takeoff run.
 
If I’m going to a high altitude airport, during a earlier flight or on the way there, I level off at airport altitude, adjust engine for 150° ROP, make a note of mixture position and use that setting. I will verify with fuel flow on roll out.
 
Lachlan said:
With a vernier mixture control, lean for max power @ 1700, then three twists rich = best takeoff power in 99.999% of non-fuel injected O-360 variants.
Click to expand...
I just go to max fuel flow (redline)....then once the gear is up....add the turns for cooling (above redline fuel flow).
 

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