Small Plane Crash at Carp - Pilot Injured

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PilotDAR
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Re: Small Plane Crash at Carp - Pilot Injured

#26 Post by PilotDAR » Thu Nov 08, 2018 6:56 am

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

#27 Post by jakeandelwood » Thu Nov 08, 2018 11:09 am

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

#28 Post by photofly » Thu Nov 08, 2018 12:06 pm

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

#29 Post by PilotDAR » 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!
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Re: Small Plane Crash at Carp - Pilot Injured

#30 Post by jakeandelwood » 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.
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Re: Small Plane Crash at Carp - Pilot Injured

#31 Post by DanWEC » Fri Nov 09, 2018 1:02 am

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

#32 Post by PilotDAR » Fri Nov 09, 2018 6:10 am

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

#33 Post by photofly » Fri Nov 09, 2018 6:14 am

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

#34 Post by jakeandelwood » 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.
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Re: Small Plane Crash at Carp - Pilot Injured

#35 Post by gwagen » Sun Nov 11, 2018 6:42 am

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

#36 Post by pelmet » Thu Nov 29, 2018 7:29 pm

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

#37 Post by photofly » 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?
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Re: Small Plane Crash at Carp - Pilot Injured

#38 Post by pelmet » Fri Nov 30, 2018 9:52 am

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

#39 Post by photofly » 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.
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Re: Small Plane Crash at Carp - Pilot Injured

#40 Post by pelmet » Fri Nov 30, 2018 1:07 pm

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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Re: Small Plane Crash at Carp - Pilot Injured

#41 Post by photofly » Fri Nov 30, 2018 3:06 pm

pelmet wrote:
Fri Nov 30, 2018 1:07 pm

I wasn't even aware that two stroke operators don't have to be aware of oil pressure and temp.
For the avoidance of doubt, I'm not sure either... but if you're adding oil to the fuel as you burn it (which is implied by having to worry about your fuel/oil mixture) then the oil isn't recirculating or being used to remove heat, so it doesn't need to be pumped at pressure, and it's just going to sit at ambient temperature for wherever you keep your oil tank, so why would you monitor its temperature?

I guess you need to worry more about oil quantity more though.

Anyway, swings and roundabouts.
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Re: Small Plane Crash at Carp - Pilot Injured

#42 Post by pelmet » Fri Nov 30, 2018 3:36 pm

Thanks,

Hopefully some people with direct knowledge of two -stroke and four-stroke operations can add to this.
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Re: Small Plane Crash at Carp - Pilot Injured

#43 Post by jakeandelwood » Tue Dec 04, 2018 1:34 am

Well outboard motors are probably the most abused motors out their, they live in the harshest environment, are cooled with salt water, sit all winter long outside and they are operated at max throttle constantly. Johnson/ Evinrude made 2 stroke outboards from like 3 horsepower up to their big bad 300 hp V8 outboard, they are the only outboard manufacturer that still makes 2 strokes. I had a 25 Evinrude and that pushed my 15'000 pound sail boat, that thing went and went, never let me down. I don't see why corrosion would be any different between 4 or 2 stroke. If they can survive hanging of the back of a boat in the ocean then they can't be that bad.
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Re: Small Plane Crash at Carp - Pilot Injured

#44 Post by PilotDAR » Tue Dec 04, 2018 5:47 am

But isn't the challenger powered by an air cooled Rotax? It's the Scorpion which is powered by the liquid cooled Evinrude....
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