Engine Failure on Take-Off

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Avio
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Engine Failure on Take-Off

Post by Avio »

Was attempting a short flight around PNG (Tapini - high altitude) with AS16 historic weather of 30 degrees C, dew point 22, and just within a minute of full power / full prop takeoff (mixture correctly leaned / mags ground-tested okay), the engine started coughing and appeared to go dead, and I had to reduce power significantly before it would come alive again. And I had to maintain lower power (lower throttle and lower RPM) initially to keep the engine going, before I could add more power during the climb. Carb temp was mostly in range so it can't be due to icing. In fact it was on the hot side.

Could it be all due to the engine running too hot using full power takeoff in the hot 30 degree heat? When I tried taking off again using lower power setting, the engine held up pretty fine.

Anyone else experienced this?

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AKar
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Re: Engine Failure on Take-Off

Post by AKar »

Probably too lean mixture as the engine recovered during climb.

-Esa

Avio
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Re: Engine Failure on Take-Off

Post by Avio »

Tried various attempts and found that the only way to prevent engine failure (airport altitude about 4,500 ft), was to lean the mixture correctly first on ground check, and set the prop to 2000 rpm. Then takeoff at 32 MP. Take way the engine held up fine. Is that the way to do high-altitude takeoff ?

On another issue, after some hard landing on uneven airstrip, I found the elevator trim was auto reset to neutral zero, when it was previously trimmed a lot to nose high. This happened on at least 3 occasions. Is there something wrong somewhere?

Avio
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Re: Engine Failure on Take-Off

Post by Avio »

The manual says to use Rich mixture when MP and RPM in yellow range. When I set to rich mix, full MP and full prop takeoff at 4500ft the engine tends to quit within a minute unless I bring back power almost immediately after takeoff.

Now which is right for high altitude takeoff - lean or full rich ?

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Piper_EEWL
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Re: Engine Failure on Take-Off

Post by Piper_EEWL »

Did you check the hangar? Could be a bad fuel filter?!
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AKar
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Re: Engine Failure on Take-Off

Post by AKar »

Yes, a tour to the hangar would be the second step.

-Esa

Avio
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Re: Engine Failure on Take-Off

Post by Avio »

Did already. Everything is fine, except for a few cylinders showing 60 to 70 percent compression.

alan CXA651
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Re: Engine Failure on Take-Off

Post by alan CXA651 »

Hi.
During my around the world trip in the A2A C172 , with real weather from ASN , i had to do an high alt high temp take off , and with full power , the engine was spluttering and aircraft was not gaining speed down the runway , what i had to do once at full throttle was to bring the mixture towards lean until i got the engine behaving correctly for takeoff.
so you might have been to rich for your alt , ie incorrect fuel to air ratio , as the high alt coupled with high temps would thin the air out , the one thing you do need to monitor very carfly when taking off in high alt high temp airfields , is the engine cht temp , and also you will need a longer runway for takeoff due to the thin air.
regards alan. 8)
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AKar
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Re: Engine Failure on Take-Off

Post by AKar »

Yeah, there are quite a few variables, and more so with Active Sky. I'd need to try out the A2A T-6 in similar conditions to play around myself, but unfortunately I'm unable for a moment.

Also recall that reducing RPM directly affects supercharger speed, and hence the manifold pressure achievable.

-Esa

Avio
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Re: Engine Failure on Take-Off

Post by Avio »

So far even when leaned correctly, engine still sputters and quit, only to wake up again if i bring throttle back before slowly adding back power. Also, the prop needs to be about 2000 rpm.

My guess is it could be overtemp somewhere at full power, even though CHT was within range.

Manual says mix to Rich during takeoff, but that applies to lower altitude. At high altitude, mix just needs the right leaning to run, but temp builds up fast too.

Tomas Linnet
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Re: Engine Failure on Take-Off

Post by Tomas Linnet »

Did you check thar automixture is off?
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MkIV Hvd
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Re: Engine Failure on Take-Off

Post by MkIV Hvd »

Avio wrote: 09 Aug 2020, 07:34 So far even when leaned correctly, engine still sputters and quit, only to wake up again if i bring throttle back before slowly adding back power. Also, the prop needs to be about 2000 rpm.

My guess is it could be overtemp somewhere at full power, even though CHT was within range.

Manual says mix to Rich during takeoff, but that applies to lower altitude. At high altitude, mix just needs the right leaning to run, but temp builds up fast too.
At higher altitudes the workable mixture setting band is actually quite narrow. I just did some testing at Tahoe - 6268' ASL @ 19°C = ISA +16.4°C if I calculated correctly...if not I don't really care, I just know it's freaking high!! :shock:

Here's the way to set yourself up for success: start like normal with the mixture rich...after start and after you have the prop in fine pitch, bump the RPM up to 1000 and rough-set the mixture before taxi - lean until RPM increase then decrease and then back rich enough for smooth running. During your runup (which you always do, right? :wink:) the last thing checked is the mixture...the same procedure on every time regardless of airport elevation. The procedure is throttle up to 1500 rpm for the prop and mag check, then advance the throttle to 2000 RPM and fine tune the mixture prior to taking the runway for takeoff. The only difference is that you don`t return the mixture to full rich after the runup at high altitude airports.

** Note: if anyone read this prior to 2253Z, Don't do that...I've since corrected it... :wink: :mrgreen:

The takeoff is normal with the prop set full fine but you'll not see 36" of manifold pressure, rather somewhat less depending on density altitude. RPM will still go to max @ 2250. Normal climb power reductions apply after the gear is up and you should be good to go from there. I didn`t notice anything abnormal with temperatures.

Most of my Harvard takeoffs back in the day were from Calgary (CYYC - 3606' ASL) or Springbank (CYBW - 3940' ASL), either of which on a hot summer day could easily get up into a density altitude of 6000' ASL+, so pre-takeoff leaning procedures were used whenever the temperature was over 20 - 25°C or so.

Cheers,
Rob
Rob Wilkinson
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Avio
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Re: Engine Failure on Take-Off

Post by Avio »

Thanks Rob and folks. I did pretty much as described herein. On power reduction after takeoff, I notice that would have to be done almost like within a minute, else the engine would start quitting. But once power is reduced (MP 30 and prop 2000 pm), it would do fine.

Wonder though is this how it is in real world T6. Having an entire engine quitting when running a little longer than a minute at full power seems to cut it too close from a safety perspective.

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MkIV Hvd
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Re: Engine Failure on Take-Off

Post by MkIV Hvd »

Avio wrote: 09 Aug 2020, 17:53Thanks Rob and folks. I did pretty much as described herein. On power reduction after takeoff, I notice that would have to be done almost like within a minute, else the engine would start quitting. But once power is reduced (MP 30 and prop 2000 pm), it would do fine.
Wonder though is this how it is in real world T6. Having an entire engine quitting when running a little longer than a minute at full power seems to cut it too close from a safety perspective.
Nope, the real world T-6/Harvard does not have that issue...and neither does the A2A model when the mixture is set properly :wink:

My frame of reference; 500 hours real world time in Harvards and the fact that I went back to Lake Tahoe yesterday afternoon when the temperature was 30°C to re-try the takeoff. Start was normal, leaned for taxi, fine tuned the mixture during the runup and took the runway. As we’re above full throttle altitude, the highest manifold pressure I could get was 32” @ 2250 rpm. My first power reduction is usually to 30”/2000 rpm, but this time I only brought the rpm back to 2200 and left the throttle at 32”. After climbing like that through 9500’ I put the prop back to full fine/2250 rpm for a bit as I continued up to 10,000’. There were no issues with the engine and the CHT never went into the yellow range.

All other things being equal, I’m convinced your issue is the mixture setting… :wink:

Cheers,
Rob
Rob Wilkinson
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Avio
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Re: Engine Failure on Take-Off

Post by Avio »

Thanks Rob. Not sure if the issue arises due to Active Sky though.

How I leaned the mixture was I ran the RPM to 2000, then leaned till the rpm drops, then add back a couple of notches of mixture to raise back up the rpm.

As long as right after takeoff I reduced engine power (32 MP, rpm a little more than 2000), engine seemed to hold fine.

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