Small Plane Crash at Carp - Pilot Injured

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rookiepilot
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Re: Small Plane Crash at Carp - Pilot Injured

Post by rookiepilot »

jakeandelwood wrote: Sun Nov 04, 2018 11:35 pm 2 stroke engines can be very reliable, they have less moving parts.
After you.......No thanks.
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Re: Small Plane Crash at Carp - Pilot Injured

Post by jakeandelwood »

photofly wrote: Tue Nov 06, 2018 10:28 am Reading up on the wikipedia entry on two stroke engines, it says:

Large two-stroke engines, including diesels, normally use a sump lubrication system similar to four-stroke engines. The cylinder must still be pressurized, but this is not done from the crankcase, but by an ancillary Roots-type blower or a specialized turbocharger (usually a turbo-compressor system) which has a "locked" compressor for starting (and during which it is powered by the engine's crankshaft), but which is "unlocked" for running (and during which it is powered by the engine's exhaust gases flowing through the turbine).

So if you need all those extra parts for lubrication, doesn't that wipe out some of the benefits of fewer moving parts?

I doubt we'll ever see someone design a new, certified aviation piston engine in our lifetime.
Are you discounting all the Thielert and Rotax engines that are certified? I'm not knowledgeable in detail about all the new engines out there, but I'm sure there are some.
"All those extra parts" you mean a supercharger or turbocharger? I believe many aircraft piston engines already have those, turbos anyways.
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Re: Small Plane Crash at Carp - Pilot Injured

Post by PilotDAR »

"All those extra parts" you mean a supercharger or turbocharger? I believe many aircraft piston engines already have those, turbos anyways.
Yes, a few GA aircraft engines have superchargers, and turbochargers are common. Superchargers have more moving parts, and turbos are critical for lubrication.

How does this relate to an accident of a non-certified aircraft near Carp?
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Re: Small Plane Crash at Carp - Pilot Injured

Post by jakeandelwood »

PilotDAR wrote: Wed Nov 07, 2018 6:24 am
"All those extra parts" you mean a supercharger or turbocharger? I believe many aircraft piston engines already have those, turbos anyways.
Yes, a few GA aircraft engines have superchargers, and turbochargers are common. Superchargers have more moving parts, and turbos are critical for lubrication.

How does this relate to an accident of a non-certified aircraft near Carp?
Yes, all these Av Canada forums stay on topic. A turbo is critical for lubrication? On what aircraft might that be?
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Re: Small Plane Crash at Carp - Pilot Injured

Post by photofly »

On the putative aircraft that has the high-reliability 2-stroke engine with a low moving part count and lubrication provided by oil that drains into a sump.

Keep up, please.
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Re: Small Plane Crash at Carp - Pilot Injured

Post by PilotDAR »

A turbo is critical for lubrication? On what aircraft might that be?
Well... turbo charged aircraft. Yes, if the turbocharger bearing seals fail, it is possible for the turbo to suck the engine oil out, causing engine seizure. It is also known on some turbo'd Continentals, where the turbocharger oil scavenge pump is within the starter adapter, that this pump can fail, and a turbocharger, and possibly engine failure results. If the turbocharger impeller shaft is starved for lubrication, the shaft will wear rapidly. The impellers can contact the housing, and break up, sending metal to places it should not be.

So a turbo charger should be considered a moving part, and because of its speed and criticality, a complex moving part. It is lubricated from the engine's lubrication system. When it has a failure related to lubrication, it's bad for the engine. Note that prudent piloting of turbocharged aircraft includes a cool down prior to shut down, which in part assures that the impellers can slow, as pressure bearing lubrication will stop when the engine stops turning. You don't want the impellers spinning away at 50,000 RPM for minutes with no pressure lubrication!
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Re: Small Plane Crash at Carp - Pilot Injured

Post by jakeandelwood »

I'm aware of all that. Actually you said "Turbos are critical for lubrication" not "lubrication is critical for turbos" that's why I questioned that statement
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Re: Small Plane Crash at Carp - Pilot Injured

Post by photofly »

Yes. According to the wikipedia page (I am not an expert on engine lubrication) so-called "normal" lubrication of a two stroke engine requires an additional turbocharger:
Large two-stroke engines, including diesels, normally use a sump lubrication system similar to four-stroke engines. The cylinder must still be pressurized, but this is not done from the crankcase, but by an ancillary Roots-type blower or a specialized turbocharger
If the lubrication requires a turbocharger then some of the advantage of having fewer moving parts in a two-stroke engine is lost.

As I said, please do try to keep up.
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Re: Small Plane Crash at Carp - Pilot Injured

Post by PilotDAR »

Actually you said "Turbos are critical for lubrication" not "lubrication is critical for turbos"
Yes, I said what I said. If a turbocharger impeller [shaft] suffers a partial or total failure, the effect of that could be critical for lubrication of the whole engine (all the oil get pumped out of the engine). The pilots of Rotax two stroke powered ultralight aircraft must be puzzled by this discussion!
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Re: Small Plane Crash at Carp - Pilot Injured

Post by jakeandelwood »

PilotDAR wrote: Thu Nov 08, 2018 2:08 pm
Actually you said "Turbos are critical for lubrication" not "lubrication is critical for turbos"
Yes, I said what I said. If a turbocharger impeller [shaft] suffers a partial or total failure, the effect of that could be critical for lubrication of the whole engine (all the oil get pumped out of the engine). The pilots of Rotax two stroke powered ultralight aircraft must be puzzled by this discussion!
Yes, you are right about that. You may run out of gas though long before a bad turbo could lose all your engine oil, but maybe not.
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Re: Small Plane Crash at Carp - Pilot Injured

Post by DanWEC »

jakeandelwood wrote: Fri Nov 09, 2018 12:50 am
PilotDAR wrote: Thu Nov 08, 2018 2:08 pm
Actually you said "Turbos are critical for lubrication" not "lubrication is critical for turbos"
Yes, I said what I said. If a turbocharger impeller [shaft] suffers a partial or total failure, the effect of that could be critical for lubrication of the whole engine (all the oil get pumped out of the engine). The pilots of Rotax two stroke powered ultralight aircraft must be puzzled by this discussion!
Yes, you are right about that. You may run out of gas though long before a bad turbo could lose all your engine oil, but maybe not.
Huh??
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Re: Small Plane Crash at Carp - Pilot Injured

Post by PilotDAR »

You may run out of gas though long before a bad turbo could lose all your engine oil, but maybe not
Well, you have fuel quantity indicators, so you can monitor consumption of fuel, so prudent pilots will land before they run out of gas. There is no in flight means to monitor engine oil quantity for horizontally opposed piston engines, so if the turbo is blowing your engine oil overboard, you really have no way of knowing that! By the time you see the oil pressure decrease, you're moments away from damaging the engine if it's not shut down. So you've at least lost power, you may have damaged the engine too.

In my youth, I was the cleaning kid for a VW/Porsche dealer. One day, one of the mechanics asked me to follow him while he test drove a Porsche 930 he was working on. My instruction was: "Follow me as I drive, when you see a massive amount of blue smoke suddenly come out of the exhaust, I'm going to pull over, pull over too, and take me back to the shop, the 930 will be towed home.". We did this, as as expected, the car suddenly emanated a huge cloud of smoke, and we pulled over. During the drive back, mechanic Franzl explained to me that he knew that the turbocharger impeller shaft oil seal was failing, but Porsche would only warranty it if it had completely failed. So he followed through on it's failure (indicated by the huge cloud of blue smoke, as the engine oil was rapidly sucked out the hot exhaust), and shut the engine down the instant it failed, so the engine itself would not be damage by oil starvation. All ended well, and I had my first introduction to turbocharging systems. The Porsche 930 engine, though hardly like a simple two stroke engine, is a horizontally opposed air cooled engine, so surprisingly similar in arrangement to most light GA engines.

It's obviously important for a pilot to understand the systems of the aircraft they fly, and be prepared to take action to prevent a situation from getting worse. So we've drifted a discussion from an unfortunate pilot who crashed his ultralight, to discussing two stroke engines, heavy diesel engines, and turbocharger systems. Have we covered the topic broadly?
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Re: Small Plane Crash at Carp - Pilot Injured

Post by photofly »

Not yet. Does anyone have any advice for keeping a pet octopus?
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Re: Small Plane Crash at Carp - Pilot Injured

Post by jakeandelwood »

I know airplanes have fuel gauges and on should monitor fuel. What I'm saying is a tiny amount of oil will make a fair amount of smoke, a bad turbo is hardly going to expel 12 liters of oil in the average flight. I'm not saying you should fly with a turbo going bad just that if it goes bad in the air I doubt you will run the engine dry before the flight is over.
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Re: Small Plane Crash at Carp - Pilot Injured

Post by gwagen »

jakeandelwood wrote: Fri Nov 09, 2018 12:53 pm I know airplanes have fuel gauges and on should monitor fuel. What I'm saying is a tiny amount of oil will make a fair amount of smoke, a bad turbo is hardly going to expel 12 liters of oil in the average flight. I'm not saying you should fly with a turbo going bad just that if it goes bad in the air I doubt you will run the engine dry before the flight is over.

The oil lubricating the turbo is under pressure. An immense volume can be pumped through in a short time, especially when the oil seals have failed.
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Re: Small Plane Crash at Carp - Pilot Injured

Post by pelmet »

jakeandelwood wrote: Sun Nov 04, 2018 11:35 pm 2 stroke engines can be very reliable, they have less moving parts.
pelmet wrote: Wed Oct 17, 2018 7:56 pm I did talk recently to someone who seems to be in the know about the two stroke market but won't post anything now until I confirm what he said in order to be 100% that I am posting what he actually did say. Will take a little while I am afraid.
I briefly met this person again. He has four and a half thousand hours behind two strokes and said that any failures that he is familiar with have been maintenance or pilot error.

He talked about engines that are tuned for higher altitudes(such as 5000 feet) and then operated at lower altitudes resulting in a lean mixture. He also mentioned that new engines should not be started until they are ready to fly. Some owners get a new engine, start it, and then don't fly for a year or so leading to corrosion. Proper oil/fuel mixture is important(some engines apparently have a pump that can automatically mix).

I didn't have much time to talk and some of this info could be not exactly correct as I wrote it down later after our discussion. It seems to me like letting an two-stroke engine sit(perhaps they can be preserved) unused for a long time might be more detrimental than for a four-stroke and perhaps they are less forgiving when abused.

Any opinions?
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Re: Small Plane Crash at Carp - Pilot Injured

Post by photofly »

Most of those considerations should apply to 4-stroke engines too, no? I don't see anything technology specific about an engine corroding if it sits for a year, or needing careful mixture control.

Except: "engines that are tuned for higher altitudes(such as 5000 feet)"

I can't be the only person to question the safety or wisdom of an airplane engine where a safe operating altitude has to be set on the engine before you take off? Bearing in mind the nature of airplanes to go up, and down, and all?
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Re: Small Plane Crash at Carp - Pilot Injured

Post by pelmet »

photofly wrote: Fri Nov 30, 2018 8:03 am Most of those considerations should apply to 4-stroke engines too, no? I don't see anything technology specific about an engine corroding if it sits for a year, or needing careful mixture control.

Except: "engines that are tuned for higher altitudes(such as 5000 feet)"

I can't be the only person to question the safety or wisdom of an airplane engine where a safe operating altitude has to be set on the engine before you take off? Bearing in mind the nature of airplanes to go up, and down, and all?
Thanks,

Fuel/oil mixture would not apply to the four strokes. Corrosion would although I did wonder if the two strokes are less tolerant of corrosion and less forgiving of improper operation/abuse.

He is from South Africa with some quite high elevation airports(although there is plenty of that sort of thing in North America). I believe the same issue can happen on four stroke engines although they have a mixture control. Not sure about two-strokers.
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Re: Small Plane Crash at Carp - Pilot Injured

Post by photofly »

A 4-stroke operator doesn't have to worry about fuel oil mixture, but does have to worry about oil temperature and pressure, which I guess the 2-stroke is relieved of. So again from what your contact said, I don't see much difference in complexity or either more or fewer "things for the operator to screw up" between a 2- or 4-stroke powerplant.
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Re: Small Plane Crash at Carp - Pilot Injured

Post by pelmet »

photofly wrote: Fri Nov 30, 2018 11:24 am A 4-stroke operator doesn't have to worry about fuel oil mixture, but does have to worry about oil temperature and pressure, which I guess the 2-stroke is relieved of. So again from what your contact said, I don't see much difference in complexity or either more or fewer "things for the operator to screw up" between a 2- or 4-stroke powerplant.
Thanks,

I wasn't even aware that two stroke operators don't have to be aware of oil pressure and temp. Yet they do have to worry about fuel/oil mixture. Sounds quite different to me although perhaps you are correct in the last sentence. I will try to find out more.

Once again, I wonder if the two-strokes are less forgiving of improper operation or somehow more "finicky".
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