Raptor Aircraft

[SoonerAviator]

I was really thinking more of aerodynamics, such as the claims he's making for the Raptor, but as long as we're talking engines..
What's important in an aero engine:

1. Reliable
2. Fuel efficient
3. Reliable
4. Reasonable acquisition cost
5. Reliable
6. Field serviceable

Oh, did I mention that they need to be reliable? As others have mentioned, the currrent low speed, direct drive, air cooled engines do their jobs pretty well, which is why they don't change much. Continental tried making engines that produced more power for their displacement, remember the Tiara series? Don't worry, no one else does either. One of their significant drawbacks were that they used more fuel than did the direct drive engine. If you look at the most efficient internal combustion engines, they are the very low speed diesels that power ships. These typically turn around 100 rpm, and are very large displacement. I don't doubt you could get a little better fuel specifics by adding electronic ignition and a better fuel injection system, but apparently not much, or else the existing manufacturers would have done so.

Don't forget about development cost. The total number of aero engines produced is very low, a modest sized automotive engine plant produces more engines in one day than the entirety of general aviation consumes in a year, there are not a lot of development dollars to be had.



An aero diesel really needs to be a clean sheet design, and the combination of low potential sales and a relatively low price per engine conspire against this happening. That general aviation seems content with flying its legacy fleet doesn't help either.



While it's true that the turbo engines do produce peak torque at propeller friendly engine speeds, they don't make much power there. You might be able to get Rotax 912 kind of power out of that engine, but I bet it would be a good bit heavier than the Rotax as well



I watched that. Now, not only would I not fly in that airplane, should it ever get aloft, I'd rather it not fly over my house. What are the principal's qualifications as an aircraft designer? It sounds like he's using the "that looks about right" method of design. He's at the point where he's looking for a test pilot and the prototype is shredding parts on a taxi test??

I agree with most of that, however, I think bigger driver of the "lack of improvements" in the piston-GA realm with regard to engine tech is certification costs. I mean, a clean-sheet design would be great an all, but even something as simple as updating to a modern fuel-injection/direct injection setup would have exorbitant certification costs. Engine manufacturers (inlcuding Lyco/Conti) have just about zero reason to put any money into R&D for updates to existing engine models. Even if there were a 10% gain in power/SFC from doing small mods to cylinder design or intake/fuel injection, they wouldn't bother with it because of the immense cost of certification. Hence why Rotax is about the only one who has made modest improvements over the years because their barriers are quite a bit lower in the Experimental realm. I don't think it's that GA is content, it's that there's no other option given that certification costs kill any development that would be possible.

 

[FormerHangie]

I agree with most of that, however, I think bigger driver of the "lack of improvements" in the piston-GA realm with regard to engine tech is certification costs. I mean, a clean-sheet design would be great an all, but even something as simple as updating to a modern fuel-injection/direct injection setup would have exorbitant certification costs. Engine manufacturers (inlcuding Lyco/Conti) have just about zero reason to put any money into R&D for updates to existing engine models. Even if there were a 10% gain in power/SFC from doing small mods to cylinder design or intake/fuel injection, they wouldn't bother with it because of the immense cost of certification. Hence why Rotax is about the only one who has made modest improvements over the years because their barriers are quite a bit lower in the Experimental realm. I don't think it's that GA is content, it's that there's no other option given that certification costs kill any development that would be possible.

Here's the upgraded fuel injected, electronically controlled aircraft powerplant: Lycoming iE3 series

And here's the first airplane that uses it:

If someone's ready to step up and order a number of new airplanes with an upgraded powerplant, looks like Lycoming is ready to supply it. Cape Air has committed to buying something like 100 of these.

 

[drotto]

I agree with most of that, however, I think bigger driver of the "lack of improvements" in the piston-GA realm with regard to engine tech is certification costs. I mean, a clean-sheet design would be great an all, but even something as simple as updating to a modern fuel-injection/direct injection setup would have exorbitant certification costs. Engine manufacturers (inlcuding Lyco/Conti) have just about zero reason to put any money into R&D for updates to existing engine models. Even if there were a 10% gain in power/SFC from doing small mods to cylinder design or intake/fuel injection, they wouldn't bother with it because of the immense cost of certification. Hence why Rotax is about the only one who has made modest improvements over the years because their barriers are quite a bit lower in the Experimental realm. I don't think it's that GA is content, it's that there's no other option given that certification costs kill any development that would be possible.

Would going to shaped pistons and changing the shape of the heads and possibly manifold provided everything else stayed the same, still require full recertification? Much of the increase in power and efficiency of auto engines are a result of those types of changes.

Those would be incremental changes, and much of the research and methods have already been done for the auto industry.

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[SoonerAviator]

Here's the upgraded fuel injected, electronically controlled aircraft powerplant: Lycoming iE3 series

And here's the first airplane that uses it:

If someone's ready to step up and order a number of new airplanes with an upgraded powerplant, looks like Lycoming is ready to supply it. Cape Air has committed to buying something like 100 of these.

Yup, but I was referring to being able to swap in (say at overhaul, whatev) the newer technology into an existing airframe. Aircraft wasn't certified for that engine model, so it's about impossible to swap the new one, even if the dimensions/etc. are all identical. Certified FAA regulations just kill any of that ability for the "market" to move forward to newer/improved engine designs.

Would going to shaped pistons and changing the shape of the heads and possibly manifold provided everything else stayed the same, still require full recertification? Much of the increase in power and efficiency of auto engines are a result of those types of changes.

Those would be incremental changes, and much of the research and methods have already been done for the auto industry.

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Most likely. Certified airframes are made compliant with a specific engine model or two. Those models are specifically called out, so moving to a new engine model involves lots of cash and piles of paperwork to accomplish. For the low volumes we are talking about, engine makers and aircraft companies don't see any benefit. New manifolds/injectors/heads need to be tested in all of the same flight regimes as the original certification because it could change the data in the AFM.

 

[hindsight2020]

.....primary non-commercial would have solved that economic incentive hurdle....buuuuut we didn't think it a big deal the FAA said "not gonna let you have that" during part 23 re-write implementation. Sooo here we are, paying Tiger Woods child support money for grenading exhaust valve POS TCM cylinders and unobtanium Textron aircraft parts. Yai!

 

[FormerHangie]

Yup, but I was referring to being able to swap in (say at overhaul, whatev) the newer technology into an existing airframe. Aircraft wasn't certified for that engine model, so it's about impossible to swap the new one, even if the dimensions/etc. are all identical. Certified FAA regulations just kill any of that ability for the "market" to move forward to newer/improved engine designs.



Most likely. Certified airframes are made compliant with a specific engine model or two. Those models are specifically called out, so moving to a new engine model involves lots of cash and piles of paperwork to accomplish. For the low volumes we are talking about, engine makers and aircraft companies don't see any benefit. New manifolds/injectors/heads need to be tested in all of the same flight regimes as the original certification because it could change the data in the AFM.

There are STCs for engine swaps, there's no technical reason someone couldn't get one to put one of these iE3 engines in some legacy aircraft. In this case, it's also redoing the engine controls, and possibly the fuel plumbing. It might require a new cowling, new baffles, a different propeller and spinner, new heater box, etc. I also get the impression from Lycoming's web site is that they'd expect you to commit to buy a certain number of units as well. I don't think the issue is technical or legal, I think it's economic, that few would spend the money for an incremental improvement in performance on their old airplane.

The engine technology exists, it's just waiting for someone to use it to build new airplanes.

 

[Velocity173]

Jeez just watched the last vid. He just can’t catch a break. Now I’m beginning to think first flight might have ended in disaster. That Lpex failing??? Then, he’s got wires resting on the aileron cables. That’s just attention to detail stuff there. Still wish him the best though and honestly hope he presses on.

 

[nauga]

That Lpex failing???

What's the source for that thing?

Nauga,
and sheer shear

 

[Velocity173]

What's the source for that thing?

Nauga,
and sheer shear

Towards the end. Not even sure what the purpose of the part is or how it failed.

 

[nauga]

Towards the end. Not even sure what the purpose of the part is or how it failed.

I watched the video, hence my question. What's the source for the part, not the source for your statement.

Nauga,
untorqued

 

[GRG55]

Here's the upgraded fuel injected, electronically controlled aircraft powerplant: Lycoming iE3 series

...If someone's ready to step up and order a number of new airplanes with an upgraded powerplant, looks like Lycoming is ready to supply it. Cape Air has committed to buying something like 100 of these.

And therein lies the problem. Cape Air will require a whole 200 engines...well, maybe a few spares on top of that. This Lycoming is an incremental improvement on the venerable 540. Hardly enough to get any tech savvy Millenial's heart fluttering.

General Motors produces an estimated 39,000 cars.
Per day.

Who in hell is going to tool up to develop and produce some magical new, high-efficiency piston aircraft engine in this circumstance?

Piston GA is NEVER again going to sell anywhere near enough units per annum to be able to support the type of clean sheet engines being lusted after by some on this forum.

Get over it.

And be thankful we aren't quite to the end of the line. Yet.

 

[Lowflynjack]

There's only one Raptor to me...

 

[Velocity173]

If you’re gonna link an Eagles video make sure it isn’t blocked!

 

[nauga]

If you’re gonna link an Eagles video make sure it isn’t blocked!

I dunno, I kind of appreciated it.

Nauga,
and a little P&M for the tennis-sweater set

 

[3393RP]

Jeez just watched the last vid. He just can’t catch a break. Now I’m beginning to think first flight might have ended in disaster. That Lpex failing??? Then, he’s got wires resting on the aileron cables. That’s just attention to detail stuff there. Still wish him the best though and honestly hope he presses on.

I've never built an airplane, but I do have years of experience with carbon fiber race cars at the highest professional level. After watching the video, all I can say is holy ****, I wouldn't taxi that thing 50 feet, much less fly it.

He's using control cable bulkhead openings for wireways. The cables and wire bundles are separated by little more than a centimeter. There is wiring run aimlessly through void spaces with no restraints. It may look good at 1 G, but that's not where airplanes operate.

The aileron cable pulley stands that deformed the fuselage are bonded directly to the skin with no force distribution doubler, and I'd wager that issue is present throughout the aircraft. There are probably multiple potential failure points in the aircraft due to non-existent engineering examination of bracket and pulley attachments.

The failure of the elastomeric-in-shear drive coupling is rather alarming. It obviously failed with a load substantially less than that which flight would require. How did he determine its suitability? How does he know the engine torque won't cause the engine mount isolators to fail?

That video really exposed how poorly the aircraft has been constructed, and the total absence of any materials and stress engineering on components makes it assuredly dangerous.

 

[Stephen Poole]

And therein lies the problem. Cape Air will require a whole 200 engines...well, maybe a few spares on top of that. This Lycoming is an incremental improvement on the venerable 540. Hardly enough to get any tech savvy Millenial's heart fluttering ... (snip) ... Who in hell is going to tool up to develop and produce some magical new, high-efficiency piston aircraft engine in this circumstance?

But that applies to general aviation in general, not just to engines. It's not a huge market. When you compare GA numbers to auto industry numbers, whether you're talking about tires and brakes or complete, ready-to-fly aircraft, GA is a rounding error by comparison.

Sorry, but I'm with Tantalum and Co on this one.

Comparing Granny Smith to McIntosh apples: 100HP, uncertified Rotax engines. A little Googlin' shows that a brand new, normally-aspirated, Rotax 912ULS engine can be had for around $18,000-19,000. (It's considerably more light weight than the equivalent Lycoming and Continental, too, incidentally.) You can buy the 912iS with fuel injection and an electronic engine management unit for a few thousand dollars more.

I suspect that Rotax will eventually produce a diesel, and/or a higher-powered 6 cylinder, at which point, you're going to see them in even more new aircraft. I don't think they'll ever "kill" Lycoming and Continental, but they will certainly take a larger and larger market share in the future, because they're more modern, more advanced units. (IMNHO.)

 

[Brad Smith]

I don't see how this project will ever deliver on the performance claims. Those crudely manufactured hinges on the canard are gonna cost him some precious knots. I hate to say it, but the whole project looks like it was designed and built by the TLAR method. Not the best approach for an aircraft that hopes to see a max speed of 300 kts.

 

[GRG55]

But that applies to general aviation in general, not just to engines. It's not a huge market. When you compare GA numbers to auto industry numbers, whether you're talking about tires and brakes or complete, ready-to-fly aircraft, GA is a rounding error by comparison.

Sorry, but I'm with Tantalum and Co on this one.

Comparing Granny Smith to McIntosh apples: 100HP, uncertified Rotax engines. A little Googlin' shows that a brand new, normally-aspirated, Rotax 912ULS engine can be had for around $18,000-19,000. (It's considerably more light weight than the equivalent Lycoming and Continental, too, incidentally.) You can buy the 912iS with fuel injection and an electronic engine management unit for a few thousand dollars more.

I suspect that Rotax will eventually produce a diesel, and/or a higher-powered 6 cylinder, at which point, you're going to see them in even more new aircraft. I don't think they'll ever "kill" Lycoming and Continental, but they will certainly take a larger and larger market share in the future, because they're more modern, more advanced units. (IMNHO.)

Unlike engines, I haven't heard anybody here clamouring for new, high technology, higher performance, more efficient piston aircraft brakes or tires?

Rotax will never produce a diesel, and I doubt it will ever produce a six cylinder gasoline aircraft engine either. My point remains unchallenged - there isn't enough market volume/production of piston GA aircraft to justify either investment.

The current Rotax aircraft engines have their roots in the much greater volume of motorized recreational vehicle engines Rotax manufactures for its parent company, Bombardier (snowmobiles, jet skis, etc). Without that, there would never have been a Rotax aircraft engine of any sort. Those applications demand high output in a small, light package (one reason Rotax also still produces some 2-cycle engines). Those origins are why the Rotax aircraft engines are small displacement, light weight gasoline engines, and will remain so.

 

[FormerHangie]

Unlike engines, I haven't heard anybody here clamouring for new, high technology, higher performance, more efficient piston aircraft brakes or tires?

Rotax will never produce a diesel, and I doubt it will ever produce a six cylinder gasoline aircraft engine either. My point remains unchallenged - there isn't enough market volume/production of piston GA aircraft to justify either investment.

The current Rotax aircraft engines have their roots in the much greater volume of motorized recreational vehicle engines Rotax manufactures for its parent company, Bombardier (snowmobiles, jet skis, etc). Without that, there would never have been a Rotax aircraft engine of any sort. Those applications demand high output in a small, light package (one reason Rotax also still produces some 2-cycle engines). Those origins are why the Rotax aircraft engines are small displacement, light weight gasoline engines, and will remain so.

The 912 is a dedicated aero engine, but its primary market is for UAVs. Rotax has built more than 50,000 of the various 912 series engines. Without the volume provided by the UAV market, I doubt the 912 would exist.

 

[jsstevens]

The 912 is a dedicated aero engine, but its primary market is for UAVs. Rotax has built more than 50,000 of the various 912 series engines. Without the volume provided by the UAV market, I doubt the 912 would exist.

Which, given the military’s desire to a single fuel source could drive a diesel solution. But not a larger (200+ hp) solution.

 

[Bacho]

The failure of the elastomeric-in-shear drive coupling is rather alarming. It obviously failed with a load substantially less than that which flight would require. How did he determine its suitability? How does he know the engine torque won't cause the engine mount isolators to fail?

Without commenting on the rest of the project, those isolators will fail REALLY fast if they get subjected to any sort of misalingment. Without seeing the failure and the rest of the project up close I can only guess. My guess would be that he has some misalingment, or the extra load created by loading up the prop created some.

Edit, I missed the close up at the end of the video. I do not like that arrangement much. I would elimnate that isolator.

 

[Crashnburn]

Some thoughts. Rotax's latest offering is 141 HP, for 5 minutes. It comes in both certified, and uncertified versions.
The 912 iS Sport (100 HP) is also available in certified, and uncertified versions.
I'm not sure about the 914, which is 114 HP, and turbo-charged.

There's an outfit - AutoPSRU(s) - that makes Propeller Speed Reduction Units up to 400 HP.
http://www.autopsrus.com/
They also sell Wankel conversions - 180HP NA, and 200 HP TurboNormalized

Of course, none of these PSRUs are certified.

 

[Grum.Man]

The problem with the PSRU is by the time you buy that and an auto engine you have as much or more tied up in it than a traditional aviation engine.

 

[ktup-flyer]

What's the source for that thing?

Nauga,
and sheer shear

https://www.flender.com/en/Products/Couplings/ELPEX-S-Rubber-Disk-Coupling/p/ATN02602

 

[GRG55]

If you’re gonna link an Eagles video make sure it isn’t blocked!

I'm not having any trouble with the link.

 

[hindsight2020]

 

[3393RP]

I was surprised to see the Raptor's PSRU had shell type journal bearings, but after examination of the video that shows the disassembled unit, it's not surprising they failed.

Considering the minor amount of PSRU run time, the absence of actual flight loads during that run time, and its operation at speeds well below flight requirements, the severity of damage it incurred indicates that the design and execution of the PSRU is wholly deficient. The defects present another indication that the aircraft suffers greatly from the absence of qualified engineering input.

 

[drotto]

I was surprised to see the Raptor's PSRU had shell type journal bearings, but after examination of the video that shows the disassembled unit, it's not surprising they failed.

Considering the minor amount of PSRU run time, the absence of actual flight loads during that run time, and its operation at speeds well below flight requirements, the severity of damage it incurred indicates that the design and execution of the PSRU is wholly deficient. The defects present another indication that the aircraft suffers greatly from the absence of qualified engineering input.

I know they would cost more, but there are diesel aircraft engines made. Why not use developed and more mature tech? Diamond is planning on putting a 360 (may have the HP slightly off) engine in the DA50's. That would seem like a good fit, even if the cowling needs a bit of tweaking.

Also, doesn't a little less then 12 inches of prop clearance seem really tight for a rear mount engine? I understand it should be fine for takeoff, but it you flair for landing, that thing seems like it is going to hit.

They also underestimated the rotational torque on the rigging turnbuckles and needed to brace them. Along with making all those little stop blocks to keep the rudders in alignment.

The more videos I have watched over the last few days just make the design seem flawed.

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[3393RP]

The more videos I have watched over the last few days just make the design seem flawed.

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It's design by reaction. He tries something, it fails, so something else is tried. That's why it's taken four years to get to this point.

The guy doesn't even have a pair of flush cuts to trim tie wrap tails.

 

[donjohnston]

Also, doesn't a little less then 12 inches of prop clearance seem really tight for a rear mount engine? I understand it should be fine for takeoff, but it you flair for landing, that thing seems like it is going to hit.

Canards don’t flare in the landing. They land and takeoff relatively flat. I don’t recall what my prop clearance is but 12” sounds about right.

 

[Velocity173]

Yeah, I’m thinking 12 inches on my Catto. During a normal landing, the canard will have stalled before the prop hits anyway.

 

[Kenny Phillips]

Well shoot I’m convinced. Hook me up with that 900hp IO-550.

Under certain conditions, 1,000 HP per liter can be realized. So I can easily do what you want. Just not for 2K hours.

 

[unsafervguy]

It's design by reaction. He tries something, it fails, so something else is tried. That's why it's taken four years to get to this point.

The guy doesn't even have a pair of flush cuts to trim tie wrap tails.

Even worse, adjusting a multi thousand dollar prop using channelocks? Buy a couple of proper size wrenches please. Shows a lack of attention to details to me.

 

[Tantalum]

I have to try and appreciate what he's doing, creating a new product, trying new things, etc., and documenting each step of the way, that's tremendous.

But some of this seems a little half baked.. I mean, the crank pulleys are causing the keel floor to bend?? And you would think the power plant and associated components would be well over engineered. Definitely does seem like a trial and error home build, vs something that was "measured five times and cut once" - I mean, the dude did not know what his prop clearance was nor what kind of clearance change he may get during rotation, until he measured it with a tape measure...

Someone said up top that this guy follows a "looks about right" engineering method, and I couldn't agree more. I mean, "the keel floor looks pretty thick, surprised it's bending like that" ... yikes!

 

[donjohnston]

The thing that surprises me is that there is a ton of prior knowledge out there that he could have tapped into. What he's doing (at least the airframe stuff) is very similar to the Velocity. The pulley issue is not an issue on my plane because it's reinforced with gussets.

I wouldn't be surprised if the test pilot saw the electrical wire laying on the cables and decided that there was a bunch more similar stuff that he couldn't see.

 

[Brad Smith]

Back to the engine debate for a moment... A high-performance single can cruise @ 200mph for hours and do it every day with no over heating or other major issues. That’s the benefit of using lots of cubic inches optimized to swing a large prop under 3000rpm with an acceptable sfc and with excellent reliability. There’s really no need for a redesign of something that has worked so well for longer than most of us have been alive. Adding water-cooling and fuel injection offer small benefits at the risk of more failure points. See the AD’s concerning the injected 172’s high pressure fuel pumps.
Gravity fed is dead reliable and when you’re up there reliability trumps any small gain in performance or efficiency from some “modern” addition to a formula that has worked for decades.

 

[Tantalum]

Back to the engine debate for a moment

I understand that there's little demand for the capital investment needed to improve these engines, given that new aircraft sales numbers are dismal for piston planes, but the idea that they are reliable and the best we can get is just patently false

you can't even look at your engine wrong or risk it might lose power or come apart in flight. We are literally flying on 1930s and 1940s technology with 0 advancements made since then. People change their oil every 25 hours and are terrified of finding metal in it, these motors are pathetic and the single biggest weak point in our planes

 

[tspear]

Back to the engine debate for a moment... A high-performance single can cruise @ 200mph for hours and do it every day with no over heating or other major issues. That’s the benefit of using lots of cubic inches optimized to swing a large prop under 3000rpm with an acceptable sfc and with excellent reliability. There’s really no need for a redesign of something that has worked so well for longer than most of us have been alive. Adding water-cooling and fuel injection offer small benefits at the risk of more failure points. See the AD’s concerning the injected 172’s high pressure fuel pumps.
Gravity fed is dead reliable and when you’re up there reliability trumps any small gain in performance or efficiency from some “modern” addition to a formula that has worked for decades.

Fuel injection increases reliability, reduces maintenance, reduces many common failure conditions (carb ice anyone?)....
As for water cooling, not sure it is worth the weight. However, water cooling allows for a much tighter tolerance, longer lasting, reduced operating range requirements.... It has many benefits. The only two questions which would cost money to answer are:
1. Is the weight payoff worth it?
2. How do you make it so there is a lower failure rate?

Then you can start to think about fadec, and EFFI. I normally go around 150K miles on a car before I trade it in; with city driving, I average around 45mph. This means that ECU has over 3K hours on it and works great. Compare that to how many times I will have spent $1500 bucks overhauling two sets of mags every five hundred hours.

I could probably gone on for a long time.... At the end of the day, it takes money to make these happen in the aviation world to get certification. And the market really is just to small to cover the cost.

Tim

 

[SoonerAviator]

Fuel injection increases reliability, reduces maintenance, reduces many common failure conditions (carb ice anyone?)....
As for water cooling, not sure it is worth the weight. However, water cooling allows for a much tighter tolerance, longer lasting, reduced operating range requirements.... It has many benefits. The only two questions which would cost money to answer are:
1. Is the weight payoff worth it?
2. How do you make it so there is a lower failure rate?

Then you can start to think about fadec, and EFFI. I normally go around 150K miles on a car before I trade it in; with city driving, I average around 45mph. This means that ECU has over 3K hours on it and works great. Compare that to how many times I will have spent $1500 bucks overhauling two sets of mags every five hundred hours.

I could probably gone on for a long time.... At the end of the day, it takes money to make these happen in the aviation world to get certification. And the market really is just to small to cover the cost.

Tim

Exactly. Having to accept a top overhaul halfway through a 2,000 hr TBO and multiple other mag/vacuum/etc overhauls in that same period is ridiculous. It’s reliable only because there’s not much else to compare it to in piston GA.

If someone came out with a liquid cooled engine of similar weight (or even 100lbs more) but had FADEC/Direct-FI, and a 3,000 TBO, I bet people would jump to it in a heartbeat. The 30’s/40’s tech gets the job done, but pretending like we can’t manage to design something better is flat out disingenuous.

 

[Bacho]

Even worse, adjusting a multi thousand dollar prop using channelocks? Buy a couple of proper size wrenches please. Shows a lack of attention to details to me.

Those are knipex pliers. Guys here are use them pretty often in place of a large wrench. Not the perfect tool but much better in that application than channel locks.