Is that a V8 under your cowl? Or are you happy to see me?

[SoonerAviator]

It's not that I think that you are wrong. I think that what you say makes perfect sense and I listed basically the same reasons why there is no demand for this in a private use piston GA. But this is the attitude that left GA engine tech so far behind. Or would have no aviation at all. The progress is not done by people that make sense, but by people who believe in the better future. We don't seem to have enough of those in private piston GA pilot community. And when we get them, they quickly realize just how daunting that road for the "better future" is and go away. Or don't and end up bankrupt.

Honestly curious if the certified, owner-maintained category ever came to fruition and it had enough leeway to allow these types of engine conversions, if it might allow some individuals to push that boundary. Lots of guys with C172/PA28 models that might be willing to try out some stuff on an old airframe with runout engines. Spend $40K+ for a new Lycosaurus which might be more than the old hull is worth, or $20K for an all aluminum LS engine and PSRU and get the bird back in the air. Twin engine airplanes would be an even more interesting case study, but I'd think that the packaging of a V8 would be problematic within the engine nacelle constraints.

 

[Bell206]

The progress is not done by people that make sense, but by people who believe in the better future. We don't seem to have enough of those in private piston GA pilot community.

While I don’t move through those circles much any more, I think there still is a solid group of forward thinkers in GA. However, most are smart enough to realize there’s no external market for their forward thinking and just enjoy their spoils on a select group of aircraft only.

it might allow some individuals to push that boundary. Lots of guys with C172/PA28 models that might be willing to try out some stuff on an old airframe with runout engines.

That can be done right now with TC aircraft just as the Corsair V8 was done. Granted an owner-mx category would simplify things but its lack doesn’t prevent it. There’s no requirement you need to pursue an STC to modify your aircraft. Plenty of “one-only” examples out there like the unlimited racers. When it comes to major changes to type design the feds main concern is if that change will kill someone else in the process and if you want to sell it. Beyond that there is not much restriction.

 

[SoonerAviator]

While I don’t move through those circles much any more, I think there still is a solid group of forward thinkers in GA. However, most are just smart enough to realize there’s no external market for their forward thinking and just enjoy their spoils on a select group of aircraft only.

That can be done right now with TC aircraft just as the Corsair V8 was done. Granted an owner-mx category would simplify things but its lack doesn’t prevent it. There’s no requirement you need to pursue an STC to modify your aircraft. Plenty of “one-only” examples out there like the unlimited racers. When it comes to major changes to type design the feds main concern is if that change will kill someone else in the process and if you want to sell it. Beyond that there is not much restriction.

I was thinking more about the type of restrictions that often come with many exhibition-experimental types. It's not that modifying your own aircraft is that difficult, from an FAA standpoint, but being then restricted into not being able to carry passengers, or having to submit an annual letter listing your intended destinations. There can be a lot of hassle depending on what type of Experimental class the aircraft is thrown into.

 

[Bell206]

I was thinking more about the type of restrictions that often come with many exhibition-experimental types.

I found that every modification and aircraft had their own influence on those restrictions. While you probably wouldn't get 100% of the things you wanted, have seen aircraft allowed to do over 90% of what the owner wanted to accomplish with the aircraft, to include pax carry. The guidance might be general, but with the proper homework and a good rapport with your DAR you might get what you want.

 

[kyleb]

....Training would become significantly cheaper, creating a bunch of new pilots that will not have a allegiance to Lyconti.

Yeah, but training would be cheaper if flight schools used C-150's and low compression, 150 HP C-172's and Cherokee 140's loaded out with legacy panels and ratty paint. Even better if they could run mogas in them (I don't think you can do that on rental planes, even with the STC, but someone will be along quickly to correct me if I'm wrong.).

For whatever reason, flight schools seem to gravitate towards spiffy C-172's with Garmin glass and which require 100LL. Affordability may be an issue, but it isn't the big problem which is people making the commitment.

 

[genna]

Yeah, but training would be cheaper if flight schools used C-150's and low compression, 150 HP C-172's and Cherokee 140's loaded out with legacy panels and ratty paint. Even better if they could run mogas in them (I don't think you can do that on rental planes, even with the STC, but someone will be along quickly to correct me if I'm wrong.).

For whatever reason, flight schools seem to gravitate towards spiffy C-172's with Garmin glass and which require 100LL. Affordability may be an issue, but it isn't the big problem which is people making the commitment.

well. That’s a different problem. 150 is 1. Old. 2. Problematic with UL, 3. Problematic with available panel or just not worth updating to anything useful beyond basics.

and ratty paint may be cheaper, but now we are going to unappealing for most would be pilots

And it’s still not cheaper than running this V8

 

[Dana]

In the end, to get widespread adoption of LS engines (or any auto engine), it would need to be type certificated... which means control of every part of the production process to aviation standards... which ain't gonna happen if you're buying short blocks from GM.

 

[MauleSkinner]

In the end, to get widespread adoption of LS engines (or any auto engine), it would need to be type certificated... which means control of every part of the production process to aviation standards... which ain't gonna happen if you're buying short blocks from GM.

I dunno…they STC’d mogas that way.

 

[Jeff767]

Knowing a few things about LS engines, and a few things about 300s and 320s, I like the LSs history over most of what is under the cowl of a 172

The LS is not a new engine and has a very good history even when run much harder than the aviation guys are running it

There are not many if any environments that run a engine harder than aviation. Most auto engines are designed to produce 50 to 70 HP reliably for very long periods of time with short bursts at higher power levels. The LS series was once tried in ski boats requiring continuous high power output. It did not go well. Certainly a auto engine can be modified for sustained high power but the modifications needed are usually pretty extensive to get a minimal service life. This is all before you add on a PSRU adding a completely new failure point.

 

[SoonerAviator]

There are not many if any environments that run a engine harder than aviation. Most auto engines are designed to produce 50 to 70 HP reliably for very long periods of time with short bursts at higher power levels. The LS series was once tried in ski boats requiring continuous high power output. It did not go well. Certainly a auto engine can be modified for sustained high power but the modifications needed are usually pretty extensive to get a minimal service life. This is all before you add on a PSRU adding a completely new failure point.

There are tons of GM v8's running in boats where the load on the engine is higher and suffers from ham-fisted operators. Granted, most of those are iron block designs, but that is more of a cost decision than anything having to do with material strength itself. Most of the engines are either idling or running 3500-4500 rpm. They last well over 1,000 hours as long as they are maintained.

 

[Bell206]

which ain't gonna happen if you're buying short blocks from GM.

But it can. There are a number of existing TC'd vehicle engines that all started from a core stick engine. You just need to quantify the existing production process which for some OEMs is easy as they use very similar quality procedures as aviation producers use. Its the same process used for other auto items on aircraft like alternators, etc. Three of these vehicle OEMs were mentioned in the OP article. Several even flew but not all achieved the same level of performance in the air as they did on the ground. And as I recall a couple of these companies even surrendered their TC, so technically one might be able to pick up where they left off? Regardless, Toyota built a whole aircraft around their TC'd Lexus engine with Rutan but in the end shutdown the venture. I've often wondered why no one offered to buy these existing dormant certified engine programs vs start anew with a different engine.

 

[Dana]

Car makers nowadays have production control and quantity systems that are better than anything the FAA requires for TC'd products, but different. To produce a TC'd product they'd have to manage a whole additional paperwork trail to satisfy the FAA. Given the small size of the aviation market, I can easily see how it wouldn't be worth the hassle and potential liability to the GM.

 

[WDD]

Yeah, but training would be cheaper if flight schools used C-150's and low compression, 150 HP C-172's and Cherokee 140's loaded out with legacy panels and ratty paint. Even better if they could run mogas in them (I don't think you can do that on rental planes, even with the STC, but someone will be along quickly to correct me if I'm wrong.).

For whatever reason, flight schools seem to gravitate towards spiffy C-172's with Garmin glass and which require 100LL. Affordability may be an issue, but it isn't the big problem which is people making the commitment.

I think Paul V of AvWeb summed it up well. More than gas mileage, flight schools want reliability above all else. They don't want to change how planes are currently maintained. What they have now is working to keep planes in the air at all times and changing isn't worth the risk.

 

[Bell206]

I can easily see how it wouldn't be worth the hassle and potential liability to the GM.

My bad. I thought you meant if someone was buying short-blocks from GM. I never implied GM would do it. But who ever was buying the blocks and applying for the TC could easily submit what GM uses for quality control and get it approved as part of their FAA production certificate. As you said GM's controls are more than acceptable. Besides if you look at the core FAA standards for production and type approvals you'll find quite a number of international standards like ASTM, SAE, etc. Its not all voodoo and gris-gris on the certification side.

 

[Dana]

Exactly. If GM was willing, it would be quite doable. But I doubt GM would be willing, which makes FAA approval essentially impossible.

 

[Bell206]

Exactly. If GM was willing, it would be quite doable. But I doubt GM would be willing, which makes FAA approval essentially impossible.

Interesting. I never dealt with GM, but are you saying if I bought a part directly from them they would refuse to supply IATF or ISO quality documentation for the part if I requested it? Guess need to scratch them off the potential vender list. Regardless, access to this type of documentation merely helps simplify the approval process but is far from a deal breaker.

 

[SoonerAviator]

Exactly. If GM was willing, it would be quite doable. But I doubt GM would be willing, which makes FAA approval essentially impossible.

Well, there have been a few other entries (Theilert, Austro) that used a Mercedes manufactured engine that was adapted to aviation and passed FAA cert approvals. I don't know that Mercedes had much to say about it, other than as a engine core supplier.

 

[Dana]

There are many cases of vendors totally uninterested in aviation, and refusing to sell to anybody who even mentions aircraft use. Many homebuilders have been through this. It's for my... uh.... airboat, yeah, that's it.

For GM or other large companies, the effort and risk isn't worth the relatively small reward unless they were dealing with another company large enough to shoulder much of the risk.

 

[3393RP]

There are not many if any environments that run a engine harder than aviation. Most auto engines are designed to produce 50 to 70 HP reliably for very long periods of time with short bursts at higher power levels. The LS series was once tried in ski boats requiring continuous high power output. It did not go well. Certainly a auto engine can be modified for sustained high power but the modifications needed are usually pretty extensive to get a minimal service life. This is all before you add on a PSRU adding a completely new failure point.

Purpose built watersports boats do not require "continuous high power output." The most widely used engines for these boats are the General Motors LS Series. Watersports boat engines are generally operated between 3,500 and 4,000 RPM, and speeds are dependent on the various disciplines:

Barefooting, 30-40 mph
Combo skiing, 25 mph
Jump skiing, 24-35 mph
Kneeboarding, 16-19 mph
Shaped skiing, 20-30 mph
Slalom skiing, 19-36 mph
Trick skiing, 11-21 mph
Tubing, 8-25 mph
Wakeboarding, 16-19 mph

Almost all purpose built marine engines for watersports boats are based on the GM 5.7 and 6.2L direct port injection LS Series. Ford engines are less popular.

The GM LS is offered in several displacement and horsepower versions. Your characterization of the engine as a failure in that role ("it did not go well") is highly inaccurate. LS powered watersports boats have outsold all other recreational boat types for several years.

One similarity between the LS boat engine and legacy aircraft engines is that both are operated at a lower RPM with a constant load. The marine LS in a watersports boat generally runs below 4,000 RPM, and horsepower output at that speed is comparable to an IO-540.

I'm curious about your statement that the LS would require "pretty extensive" modifications to have a "minimal service life." Can you elaborate?

 

[GaryM]

Exactly. If GM was willing, it would be quite doable. But I doubt GM would be willing, which makes FAA approval essentially impossible.

Forget GM, an Audi turbo diesel is the way to go.

At least, based on the number of times it came up in the Raptor thread.

 

[Bell206]

There are many cases of vendors totally uninterested in aviation, and refusing to sell to anybody who even mentions aircraft use. Many homebuilders have been through this.

I guess it depends on your experience. Perhaps its more on the E/AB side? I've bought a number of different non-aviation parts from small to large vendors and had no issues purchasing the parts even though they knew it was going on an aircraft. But it does void any warranty. Never bought a short block though and only dealt with Motorcraft and others on accessories. I have had some non-aviation shops decline to repair or service a part but usually found someone else who would assist. As to risk to the vendor, I guess they could look at it that way, but based on my experience I think if I approached GM (not a dealer) to buy 3 LS marine engines for use on an aircraft project, they would sell them and provide quality documentation. At worse, they may ask for a "hold harmless" agreement which I've also done. In the end, all the risk and liability falls to me or whoever uses those parts on the aircraft and signs it off.

 

[kyleb]

Purpose built watersports boats do not require "continuous high power output." The most widely used engines for these boats are the General Motors LS Series. Watersports boat engines are generally operated between 3,500 and 4,000 RPM, and speeds are dependent on the various disciplines:

Barefooting, 30-40 mph
Combo skiing, 25 mph
Jump skiing, 24-35 mph
Kneeboarding, 16-19 mph
Shaped skiing, 20-30 mph
Slalom skiing, 19-36 mph
Trick skiing, 11-21 mph
Tubing, 8-25 mph
Wakeboarding, 16-19 mph

Almost all purpose built marine engines for watersports boats are based on the GM 5.7 and 6.2L direct port injection LS Series. Ford engines are less popular.

The GM LS is offered in several displacement and horsepower versions. Your characterization of the engine as a failure in that role ("it did not go well") is highly inaccurate. LS powered watersports boats have outsold all other recreational boat types for several years.

One similarity between the LS boat engine and legacy aircraft engines is that both are operated at a lower RPM with a constant load. The marine LS in a watersports boat generally runs below 4,000 RPM, and horsepower output at that speed is comparable to an IO-540.

I'm curious about your statement that the LS would require "pretty extensive" modifications to have a "minimal service life." Can you elaborate?

Is there any longevity information on those motors in a marine application? Hours before rebuild/replacement? Even that might not be a good metric because I’d accept the risk of my ski boat being towed in. My airplane, not so much.

 

[3393RP]

Is there any longevity information on those motors in a marine application? Hours before rebuild/replacement? Even that might not be a good metric because I’d accept the risk of my ski boat being towed in. My airplane, not so much.

Most warranties are 5 years/1000 hours.

Based on my research and personal experience, failures are extremely rare. Just like your airplane, they require periodic inspections and ongoing scheduled maintenance.

 

[Sierra_Hotel]

High-strung 1000+ hp boat engines are usually rebuilt at 500 hours, but your standard Mercruiser 5.7 will run forever.

 

[genna]

There are not many if any environments that run a engine harder than aviation. Most auto engines are designed to produce 50 to 70 HP reliably for very long periods of time with short bursts at higher power levels. The LS series was once tried in ski boats requiring continuous high power output. It did not go well. Certainly a auto engine can be modified for sustained high power but the modifications needed are usually pretty extensive to get a minimal service life. This is all before you add on a PSRU adding a completely new failure point.

I can assure you that modern cars/engines are designed to reliably deliver a lot more than 70 hp for days at a time.

Escalade needs about 140hp to travel at 100mph. something it can do for hours.
And car’s engines do not live in a much easier steady state.

as far as planes, most cruise at 60-65% of max power. For a 360 that’s about 110 hp

 

[SoonerAviator]

Is there any longevity information on those motors in a marine application? Hours before rebuild/replacement? Even that might not be a good metric because I’d accept the risk of my ski boat being towed in. My airplane, not so much.

Part of the issue on longevity is that most boats in the US only rack up about 20-30 hours per year. So it takes a few decades to even get decent hours on it. I have a 1976 ski boat with an original Ford 351w and it only has about 800 hours on it and the original outdrive. Fires up and runs great every year.

Outboard motors tend to rack up more hours due to being more of an all-seasons design since it's self draining for cold weather. They routinely get 1,500+ hours out of a powerhead.

 

[kyleb]

Part of the issue on longevity is that most boats in the US only rack up about 20-30 hours per year. So it takes a few decades to even get decent hours on it.

Makes sense. When someone says "These motors last forever in boating applications", is that because it would take a hundred years for them to hit a 2,000 hour TBO? I mean, after 20 years at 25 hours a year, that's still only 500 hours. The boat is probably obsolete and pushed off into a corner somewhere by then...

 

[Dana]

Part of the issue on longevity is that most boats in the US only rack up about 20-30 hours per year. So it takes a few decades to even get decent hours on it.

Sounds like a lot of airplanes...

 

[SoonerAviator]

Sounds like a lot of airplanes...

Yup, lol. Eerily similar.

 

[SoonerAviator]

Makes sense. When someone says "These motors last forever in boating applications", is that because it would take a hundred years for them to hit a 2,000 hour TBO? I mean, after 20 years at 25 hours a year, that's still only 500 hours. The boat is probably obsolete and pushed off into a corner somewhere by then...

Indeed. Many times the boat hull is scrapped but the engine and outdrive get sold and live on in another vessel. Most inboard boat engines suffer death via water ingestion from a corroded/cracked exhaust manifold water jacket, or from improper winterization which generally ends up cracking the engine block since most don't have antifreeze or a closed cooling system.

 

[Jeff767]

Purpose built watersports boats do not require "continuous high power output." The most widely used engines for these boats are the General Motors LS Series. Watersports boat engines are generally operated between 3,500 and 4,000 RPM, and speeds are dependent on the various disciplines:

Barefooting, 30-40 mph
Combo skiing, 25 mph
Jump skiing, 24-35 mph
Kneeboarding, 16-19 mph
Shaped skiing, 20-30 mph
Slalom skiing, 19-36 mph
Trick skiing, 11-21 mph
Tubing, 8-25 mph
Wakeboarding, 16-19 mph

Almost all purpose built marine engines for watersports boats are based on the GM 5.7 and 6.2L direct port injection LS Series. Ford engines are less popular.

The GM LS is offered in several displacement and horsepower versions. Your characterization of the engine as a failure in that role ("it did not go well") is highly inaccurate. LS powered watersports boats have outsold all other recreational boat types for several years.

One similarity between the LS boat engine and legacy aircraft engines is that both are operated at a lower RPM with a constant load. The marine LS in a watersports boat generally runs below 4,000 RPM, and horsepower output at that speed is comparable to an IO-540.

I'm curious about your statement that the LS would require "pretty extensive" modifications to have a "minimal service life." Can you elaborate?

You are not looking at the HP required to maintain those speeds. RPM to a certain extent is meaningless. Typical inboard ski boats top out at 40 to 44 MPH. Surf and wakeboard boats sometimes slower. My current boat tops at 38 and is using over 250 HP to cruise at 28. Loaded down for wakesurfing I am only doing 11 mph but probably pulling 300 plus HP. Aluminum blocks don’t cool well in sustained high power operations unless purpose built for that. That is why the vast majority of boat engines are cast iron. It tends to prevent hotspots and heat more uniformly. Your car engine at cruise on the highway at 70 is probably putting out under 80 HP. It’s designed to do that virtually forever these days. At highway speeds your car is probably burning 2 to 3 gallons an hour to show how lightly loaded they are. Crank that power up and sustain it and service life drops dramatically. The LS series used in a Malibu boat mostly failed in under 100 hours. Detonation due to hotspots killed the motors and despite putting a lot of effort into it they were unable to fix the problem and had to recall the boats and replace the engines with a different type.
To put it in a different perspective boat engines generally last about 1000 hours. Some more and some less. That’s about 50,000 miles in a car. Most modern auto engines will do well over 200,000 miles. The current aircraft engines considering the sustained power requirements last quite well.

 

[SoonerAviator]

You are not looking at the HP required to maintain those speeds. RPM to a certain extent is meaningless. Typical inboard ski boats top out at 40 to 44 MPH. Surf and wakeboard boats sometimes slower. My current boat tops at 38 and is using over 250 HP to cruise at 28. Loaded down for wakesurfing I am only doing 11 mph but probably pulling 300 plus HP. Aluminum blocks don’t cool well in sustained high power operations unless purpose built for that. That is why the vast majority of boat engines are cast iron. It tends to prevent hotspots and heat more uniformly. Your car engine at cruise on the highway at 70 is probably putting out under 80 HP. It’s designed to do that virtually forever these days. At highway speeds your car is probably burning 2 to 3 gallons an hour to show how lightly loaded they are. Crank that power up and sustain it and service life drops dramatically. The LS series used in a Malibu boat mostly failed in under 100 hours. Detonation due to hotspots killed the motors and despite putting a lot of effort into it they were unable to fix the problem and had to recall the boats and replace the engines with a different type.
To put it in a different perspective boat engines generally last about 1000 hours. Some more and some less. That’s about 50,000 miles in a car. Most modern auto engines will do well over 200,000 miles. The current aircraft engines considering the sustained power requirements last quite well.

Most modern outboards engines are aluminum blocks and last just fine though. I'm sure a primary driver of the inboards not being aluminum blocks is that weight is generally less of a consideration in inboard applications, not to mention just using whatever truck block GM is currently manufacturing.

 

[Jeff767]

Modern outboards are excellent. They are however purpose built from the ground up to be boat engines. They are not auto conversions. Big difference! Outboards power heads would actually be much better than auto engines to convert to aircraft use. I suspect however layout might be a issue. You can cool aluminum for sustained high power and outboards are built for that applications. Auto engines are not.

 

[unsafervguy]

Modern outboards are excellent. They are however purpose built from the ground up to be boat engines. They are not auto conversions. Big difference! Outboards power heads would actually be much better than auto engines to convert to aircraft use. I suspect however layout might be a issue. You can cool aluminum for sustained high power and outboards are built for that applications. Auto engines are not.

however, in a marine application you have a unlimited supply of cool coolant to get rid of the heat using an open loop system. so, in an aircraft situation, you would be using a closed loop cooling system. i would assume it could be overcome, as rotax has done it on the closed loop systems in the seadoo, but it is still a problem that would have to be overcome.