Siezed low-time neglected turbocharger

[pfhoeycfi]

Help me out. I'm missing something in this thread and others that I've read on engine choices. If money and weight are not the problem, what's to stop anybody from installing an O200? Welding a mount? Modifying the cowl?

[SNX1508]

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.....The fact still remains that Sonex has had a turbo and non turbo aerovee fail in their factory aircraft killing two and seriously injuring two others. To date no explanation or plausible theory has been provided by sonex and probably never will be.

Keith
#554

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.....Oh and one more thing, since it was brought up about the factory crashes. Its a whole new thread, but my intuition that these were both low fuel situations.

WaiexN143NM
Michael

*****************
All, FYI,

The NTSB investigation docket for the N12YX incident was updated & released to the public on December 11, 2017.
For interesting reading, see the N12YX National Transportation Safety Board Aviation Accident Factual Report, found here:

https://app.ntsb.gov/pdfgenerator/Repor ... l&IType=LA

…and also the file titled “Record of conversation – FAA Inspector, which can be downloaded from the NTSB docket database, found here:

https://dms.ntsb.gov/pubdms/search/hitl ... B51F5993CC

Terry L. Cooper
SNX #1508
Tail Wheel
AeroVee #0736
N296SX
2005 construction hours, and was completed in October 2016
http://www.mykitlog.com/SNX1508
First engine run: https://www.youtube.com/watch?v=K9wP77I ... e=youtu.be
FAA Inspected & Airworthiness Certificate issued 11/4/2016
Sport ASEL endorsement on 8/9/2017
Tailwheel endorsement on 9/7/2017
Sonex #1508 N296SX first flight on 11/29/2017

[Gordon]

More VW engine debate.................

No disrespect to you Noel but........you haven't flown yours over hostile country yet.

It's easy to sit back and have a hypothetical discussion at your computer about engine reliability but when your are at 8500 feet over miles of completely hostile country (Northern Ontario, Canada) like I have in my Lycoming RV-6 you have a different feeling in your gut. A forced landing, at best is a life threating event and at worst is fatal.

I don't plan to fly my VW powered Onex in any of those places that I used to fly the Lycoming. If Sonex had offered other engine mounts for the Onex, I would have likely went with the 3300 Jabiru or UL Power.

Maybe next time............

Gordon..........Onex.......Hummel 2400

[pfhoeycfi]

fyi...

Per the Sonex website Onex ULP mounts are available from Kaolin Aviation. I contacted them late spring and the price for the mount was reasonable. I decided on the B however.

peter

[OneTallShort]

How about a 9.6 oz, 12V, 700 ma pump?
https://www.amazon.com/gp/aw/d/B0196WL55G

Bryan, At a max temp of 100C, I think that may be a bit low for coolant...

Personally I'm wondering if an auxiliary oil pump isn't the way to go... and just be able to keep the engine oil flowing after shutdown for a few minutes...that way you're not adding an additional fluid to the mix. (which isn't included in your weight)

Something like this 12V Oil Scavenge Gear Impellor Pump: https://www.ebay.com/itm/12V-3-7GPM-Gea ... 2963220647 (which is just my first quick look, and may be more flow than needed...but this mentions turbo use..)

My take is that it's the oil sitting there, heating up on shutdown that is coking, but if we maintain flow, then the overheating will simply not occur. I'm not sure where this pump would sit in line and what backflow valves would be needed though... I'd want it to be independent of the engine oil pump...don't want to add an electrical flight requirement...on the ground...that's another story.

But is air cooling really out as a solution? That's basically the factory answer...take the turbo blanket off so there is more airflow around the unit,...and remove places for the oil to collect. Using a small electric squirrel cage fan directed at the turbo on the ground might be a simpler, lighter answer...or just adding a few gills above the unit on the cowl (behind the plenum)...which may be my first move...

But the first move we should be talking about as a group is monitoring the temperature of the unit. Most of us 4 bangers have an extra thermocouple or two channel (especially the MGL units) that can be used to monitor what's going on in the current field installed units. Let's get and share some data!

Your mileage/ flight time may vary. This is experimental aviation. Not factory approved.

---
Gregg Short
Sonex 715 with a Turbo Aerovee installed but not yet run.

[NWade]

Since a few responses have shown that either I didn't communicate clearly or people are misinterpreting what I said, let me try to clarify my earlier post. Also, I'll provide my detailed thoughts on improving the Turbo's reliability...

1. I never said VW engines are as-reliable or as-easy as purpose-built aircraft engines. In fact, I thought I was being specific when I said that conversion engines always have some degree of compromise to them, by definition. So if you thought I was defending the AeroVee (or any other conversion engine) in my comments, there was a miscommunication. I do not think that conversion engines are the lowest-effort or most-reliable solutions. My main point was that companies like Rotax, Jabiru, Rotec, UL, and others provide aircraft engines that are just as well-engineered as Lycomings and Continentals - there is nothing magical about those two brand-names.
2. When talking about certified aircraft engines like Lycs & Contis, saying "I feel" or "in my gut" or words to that effect prove the point I was trying to make about them: People _feel_ a certain way about them (and you are totally entitled to your feelings). But a lot of folks (not necessarily _you_, but lots of folks I've talked to around airports) base their feelings on incomplete data, hearsay, and a lack of working knowledge of how internal combustion engines work; or lack of hands-on experience working on engines**. Lycs and Contis are by far the most numerous aircraft engines so people are more-familiar with them from a brand-recognition standpoint; but that doesn't automatically disqualify others (as an analogy, look back at when Honda and Toyota came to the US in an era where people were familiar and comfortable with Ford and GM).
3. When I see people spiral into a bunch of negative comments about a particular item, I see a lot of these feelings and second-hand knowledge get thrown around, and less first-hand experience and data being used to back up people's arguments. Also, we generally don't see a discussion about alternative solutions and their relative tradeoffs. If there was a magic-bullet solution that was universally better than all of the others, then the sport/industry would consolidate around that solution (excepting the few mad-scientist types among us). :-)
4. We're in the hobby of Experimental Aviation. I can understand people's frustration at Sonex Aircraft not officially _supporting_ some engines or other hardware; but at the same time there is nothing _stopping_ you from putting whatever you want onto _your_ airplane. We are each the manufacturer-of-record for our own craft; not Sonex. As long as the DAR signs it off, that's all that matters! I think with the Sonex web store and the relative ease of ordering parts (quality and timing aside), builders sometimes forget that they are well within their rights to find a local welder/mechanic/machinist/fellow-EAA'er and fabricate up whatever parts they want. If you truly want an O-200 on your Sonex, go look at another small aircraft that has one, figure out how to adapt or re-make that engine mount to fit the Sonex firewall, and go for it! :-)
5. Lest anyone think I'm a fanboy, please look up my other forum posts - I have had some parts-quality problems with my AeroVee components (such as a prop-hub being improperly machined, screw-ups in the crankcase machining process, and a curved vertical stabilizer-tip). So I fully understand people's frustrations with Sonex Aircraft! The crew there has always been very pleasant on the telephone and I think they're good people in their hearts, but there have been some SNAFUs in the last couple of years. My personal speculation, based solely on my interactions with them, is that some of this is due to the diversification of the Sonex product-line - its spreading staff attention thinly across all of the things they're trying to do (the Turbo, the Onex, the Jet, the Drones, etc). But at the same time I have no insight into their finances or their operations, and it could be that they _need_ to do this in order to keep their business viable over the long-term. Running a business requires compromises and difficult decisions so I am wont to give them the benefit of the doubt. And I will say that some of their parts have been improved in recent years (i.e. AeroCarb to AeroInjector, better fiberglass parts like the newer split cowling, etc) - so they're not totally resting on their laurels. Right now my opinion of the company is that they're good people who are trying to tackle too much and/or are being put in some difficult situations. I wish my experience was a little better; but at the same time I don't think Sonex is a "bad" company, or that they're going down the tubes. They're just complicated and sometimes flawed, like most of us. :-P

Now, regarding that Pesky Turbocharger (the actual topic of this thread)...

• In response to the earlier post about Turbocharger engineering/best-practices and the linked document - If you look at the way the AeroVee Turbo is plumbed into the oil system, you'll see that it seems to meet the design criteria set out in that article:
  
  • Oil enters from the top of the turbo and drains out the bottom.
  • The oil return line is plumbed through a pump (pulling suction on the line) and returned into the crankcase below the level of the turbo, but above the level of the oil sump (so there's no back-pressure on the oil return line)
  • The oil feed into the top of the turbo is above the crankcase, and the tube has an upward bend in it.
  • So when the engine isn't running there is no pressurized oil forcing its way up into the feed line. Theoretically, the oil in the feed line and in the top of the crankcase oil galleries should drain back down into the sump (not progress forward into the turbo).
  • Also - theoretically - the oil in the turbo should be able to drain down into the "mini-sump" (mounted to the bottom of the turbo) after shutdown.
• But I am concerned that the theory may not be true on that last point. The reason for my concern is that I have to think that the mini-sump and the return line (back to the oil pump) are full of oil when the aircraft is running. Then when you shut down the engine, the oil pump stops spinning and becomes a "blockage" in the oil return line. Also, the oil return line is piped upwards from the pump back into the crankcase, so gravity won't help pull any oil through the (non-rotating) oil pump in any case. So in my mind you have a bunch of oil sitting in that return line, mini-sump, and possibly in the turbo itself after shutdown; and that oil has nowhere to go.
• If oil is trapped in the turbo and there's a bunch of heat-soaking in the turbo housing after shutdown, then things are inevitably going to get coked/crusty in there. The only two options are: [A] Get all of the oil out (which may be nearly impossible, as there will likely be at least a film left around the bearings), or [B] Have some fluid circulation in the turbo after shutdown to help carry away the heat.
• If you want to carry away the heat from the center of the turbo, you have two ways to do it: Use the oil gallery or use the water passages.
• If you want to use oil, then you have to have a way to keep pumping oil through the turbo after the engine is shut down. The current plumbing doesn't provide a way to do that. Given the engine-driven oil pump, you'd need to add a separate (electrical) oil pump and a set of oil lines to pull oil from the engine sump and pipe it into the oil inlet at the top of the turbo. This immediately presents some complexity and design challenges:
  
  1. You wouldn't want this pump running when the engine is turning, because you'd over-pressure the turbo feed-line and possibly starve the engine sump/oil-pump. We don't want operator-error causing a blown-out oil line or a seized engine in-flight, so how do you arrange relays or switches to reduce or eliminate operator error? Also, how do you set up this system to automatically turn on after engine shutdown and run for 5-10 minutes (or do you rely on checklists and assume responsibility for the negative repercussions if you forget it a few times over the course of a year)?
  2. When the engine is turning, the engine oil-pump pulls suction on the oil return-line from the turbo. How do you arrange your secondary oil loop (from the sump to the turbo) so that the suction on the return line pulls oil from the top of the engine crankcase instead of siphoning it up from the sump?
  3. When the engine is _not_ turning and the electrical pump is running to circulate oil, you're pressurizing the line that feeds into the top of the turbo. How do you ensure that oil gets forced into the turbo and not simply blown "backwards" into the top of the engine crankcase? Do you install a bunch of one-way-valves and add components to inspect, replace, and possibly fail in flight? What are the consequences of such a check-valve failing - does it fail "open" or "closed"? If it fails closed, you starve the turbo of oil in-flight and guarantee it seizes up...
• OK, so what about using the water passages?
  
  1. As some have suggested, passing the existing oil through the water passages as an "extra loop through the turbo" would seem to provide a simple solution and give extra fluid to absorb heat. But there are three flaws with this plan: First, you aren't really adding much extra fluid so you can't absorb that much extra heat. Second, the oil gets pretty hot on its first trip through the turbo; when you pass it immediately back through the turbo you're adding hot fluid to the system; and with a smaller temperature-differential on the second pass the oil isn't going to absorb that much extra heat. Third - and this is the kicker - when you shut the engine down you still have no coolant flow and now you're heat-soaking an even larger puddle of oil to get crusty/coked. IMHO a couple of extra tablespoons of oil sitting inside the turbo aren't going to meaningfully help with post-shutdown heat-soaking - the heat has nowhere to go if its still trapped inside the assembly!
  2. OK, so what about adding another oil loop from the engine sump to the water passages of the turbo? Well, now you're right back to an electric pump that can run after engine shutdown, and many of the issues I raised above. Sure, you don't have to worry about check-valves as much, but you still have to worry about this pump running at the right times and *not* running whenever the engine is turning. Plus, if the oil isn't moving when the engine is turning, your turbo water passages are now an excellent place where the stationary oil just gets brutally cooked during the flight, then circulated into your engine sump after the flight is over. This seems like a recipe for problems to me!
  3. OK, so what about using a few pounds of water and some kind of small motorcycle or lawn-tractor radiator? A water system that's isolated from the engine oil supply would obviate a lot of the issues mentioned above; but it still presents some challenges:
     
     • The simplest solution would be a "natural circulation" system that allows water to be heated by the turbo, flow upwards and forwards to a radiator, cool off (via intake air), then flow down through tubing to a low spot in the cowling and then upwards again back into the turbo. However, the Sonex cowling doesn't really have space anywhere above the engine cylinders to mount a radiator - not without fabricating a big hump in the cowling. And its unknown whether natural circulation would work well-enough without requiring a lot of steam-pressure inside the system (leading to possible blow-outs of the water piping. Not as catastrophic as an oil line blow-out, but certainly not fun to deal with the mess and possible electrical shorting/damage/chaos). We might be able to mount a radiator (and supplemental water tank if needed) below the engine inside the existing cowling (a la the old bottom oil-cooler); but now the hot water must be forced downwards from the turbo to the radiator. This is not going to allow for natural circulation to be effective, especially after engine shutdown and no fresh air over the radiator to keep it cool - remember that post-shutdown heat-soak seems to be the harshest thing on the turbo, and is therefore the problem we want to solve the most.
     • We could add an electric water pump and use that to obviate the need for natural circulation; but again there are questions about how much water we need (so the temp and pressure of the water doesn't get too high as it absorbs more and more heat from the turbo during flight), and we need to keep it running after engine shutdown. And ideally we'd still prefer natural circulation even after we shut down the water pump (so superheated water doesn't sit inside the turbo and keep it hotter for longer - remember the whole idea is to carry away heat from the center bearing so the oil in there doesn't get cooked); if the turbine is operating at many hundreds-of-degrees (or perhaps up over 1000 degrees), then running a water pump for 5 minutes after shutdown (with no cooling air flowing over the radiator) won't bring that system down to room temperature or anything close to it. Oh, and on a practical note we'd need to figure out how we can plumb water piping in around and behind the turbo (which is tight on a Sonex).

The bottom line is that the oil and water passages on the turbo don't appear to provide a simple/quick/easy solution to the potential problem of post-engine-shutdown heat-soaking of the center bearing and oil in the turbo. At least, not one I've been able to think up. I certainly would love to find one, though! I'm still going to give my turbo a go, but I would definitely feel more comfortable about its longevity if we had a better way to cool it off after flight.

Take care,

--Noel

**Background note: Before getting my pilot's license, I was involved in auto-racing. I drove and also wrenched on cars ranging from SpecMiatas to purpose-built GT-1 cars with 750hp V8s. I am by no means a professional, but I've helped rebuild engines and transmissions for several of those vehicles.

[Brett]

Well Noel it certainly looks like by your post you have spent a heck of of lot of time thinking about all the options. I really appreciate the response you’ve written as you bring up quite a lot of things I’ve also thought about. I myself sit at the hangar a fair bit thinking about all sorts of options and so on to add cooling or this or that or different oil systems. Fact of the matter is that I can’t get past boils down to the turbo being incompatible. I’m no expert believe me, but I am a 43 yr old car mechanic. I work in a multi franchise service and repair dealership. We have Hyundai, Ford, Honda, Subaru, Suzuki and Nissan. It’s a tough game trying to know all these brands but one thing sticks out is not one car ever over my entire life has had cooling ports on a turbo and them not been connected. Another thing springs to mind around the year 2000 or so was Nissan’s brought out the ZD30 Diesel engine with a water cooled turbo. Had failures quite often. Later on they revised the turbo and fitted an oil cooled only turbo to the engine. They only stopped selling this engine in Oz about 2 years ago And one thing is for sure the turbos not once in my whole time ever needed changing due to being coked up... they just eventually wore out after around 200 000 km depending on how nice the owner was in regard to oil changes. How many stop starts in that lifespan I could not even hazard to guess.
I look at the cessana 400 in the hangar next to me that hasn’t flown in about 5 years that has the cowls off permanently. Twin Turbos hanging right under the engine in the lowest spot possible. Oil cooled only and that motor btw has about 500 hours on it. Neither turbo has been replaced. Those big Continental engines only run on dinosaur oil so surely that’s saying something.
This motor and combination has so much potential but putting a cheap arse turbo on an aircraft engine that you can buy from eBay for around $400 is not doing me or the company any good in my opinion. I’m actually sick of being the laughing stock of my Aeroclub now due to working on my plane engine more than flying it. I estimate I have about 5 more flights before I’ll need a new turbo. This will be the decisive time for me in regard to fitting a more suitable turbo and potentially throwing more money away or just biting the bullet and either making a mount or buying one for the 912 uls and sadly putting it all behind me.

[lutorm]

I was on a short cross country flight and an exhaust valve rocker arm broke and the motor stopped cold. I blame it on cheap parts from China or Brazil or where ever it is that Sonex sources their stuff.

This is a bit of an aside but, if you don't mind me asking, which cylinder was it? And did you figure out why?

The reason I'm asking is because I've learned that the Type 1 VW apparently has a weak oil supply to the heads, especially to the (as mounted in our planes) left side. All oil to the left head comes through a single gallery connected to the center cam bearing, and the pushrods only get oil when the valves are actuated, a small fraction of the time.

People running high-performance VWs have been making modifications to the engine to increase the oil supply to the heads (see Bob Hoover's "HVX mods", http://bobhooversblog.blogspot.com/2007/05/hvx-mods.html.) He encouraged those mods for aircraft applications, too, but I've never seen them mentioned in the Aerovee context. Since I'm currently rebuilding our Aerovee, I'm making them.

The same guy was a big proponent of adding oil filters, saying it was the single most important thing to enhance the reliability of the VW engine. After seeing the inside of our engine, I'm doing that too.

If you browse those web pages, you'll find a lot of accumulated VW experience. Another thing he says is that, with the quality of VW parts available today, you can not just get a bunch of parts, bolt them all together, and expect to end up with a reliable engine. You need to make sure everything fits together properly. Perhaps that is why some people seem to have an Aerovee that runs flawlessly while others have nothing but problems: dumb luck?

[mike.smith]

Oh and one more thing, since it was brought up about the factory crashes. Its a whole new thread, but my intuition that these were both low fuel situations.

There is no information to bear that out. The first factory crash was on takeoff for a familiarization flight and to my knowledge had plenty of fuel. At the scene of the second crash investigators noted there was enough fuel in the tank to complete the intended flight (that information comes first hand from the two pilots involved).

[Waiex 49]

It was asked:

This is a bit of an aside but, if you don't mind me asking, which cylinder was it? And did you figure out why?

It was the exhaust valve rocker on cylinder #4.

Why did it break?

I don’t know for sure, but I believe that cheap VW aero engine kits are made up from cheap aftermarket parts that don’t hold up.

What I can tell you for sure is that it isn’t much fun when your engine stops running. Things get real serious in a hurry and the “advantages” of a “cheap” engine aren’t of much comfort.