What Could You Do With A 65hp Turbo-Normalized Motor?

[Grimace]

We all know about feature creep in any design. And "hp creep" (Xhp is good, so X+20hp is better). But for a long time, this little engine had my mental gears turning. 65hp, 100lbs, turbocharged. Aerotwin Motors Corporation

If you designed a tiny little "speedster" for low altitudes and then allowed it to produce its full rated hp (or something close to it) up to 14,000 or 18,000 feet or more... would that be a viable (relatively) high speed X-country airplane? Or are there design tradeoffs between making something so light and optimizing it for high altitude flight (the need for breathing O2, notwithstanding).

The one obvious drawback here is that if this company went belly-up, it seems quite a bit more advanced than anything else in the marketplace, so your design would go along with the fortunes of the experimental engine manufacturer (historically, that's not a good bet). Anyway, it seems like a pretty big step in terms of lbs/hp, at least as far as the slow/cheap/economical end of the spectrum tends to go.

I'm sure some people here can generate some good thoughts on this..

 

[SVSUSteve]

If you designed a tiny little "speedster" for low altitudes and then allowed it to produce its full rated hp (or something close to it) up to 14,000 or 18,000 feet or more

The question is why would you want to be exposed to the cold air temperatures and hypoxia of those altitudes in something small enough to be a "speedster" with a 65 hp engine?

would that be a viable (relatively) high speed X-country airplane?

It depends on what you are comparing it to when you say "relatively"? A Cessna 172? An Aeronca? A car? A bicycle? Amtrak?

By aviation terms, nothing with a 65 hp engine is going to be "high speed". Even with an LSA size limitation attached to it (which is to say you kill the marketability as a means of cross country travel thanks to limits on fuel volume, baggage and passengers), you'd probably sit right at 100-110 knots. You get up to 14,000 feet, not only is it going to be cold and have reduced oxygen levels, you're starting to get into territory where it's not uncommon to have a calm day involving a 10-20 knot wind. Looking on Fltplan.com for a flight Denver to here at 16,000 feet, I could be facing up to a +17 knot headwind and that's pretty modest. That pretty much offsets whatever benefit you might see in a "turbonormalized 65 hp" engine powered "speedster"

its full rated hp (or something close to it)

Are you a pilot currently?

 

[Jay Kempf]

We all know about feature creep in any design. And "hp creep" (Xhp is good, so X+20hp is better). But for a long time, this little engine had my mental gears turning. 65hp, 100lbs, turbocharged. Aerotwin Motors Corporation

If you designed a tiny little "speedster" for low altitudes and then allowed it to produce its full rated hp (or something close to it) up to 14,000 or 18,000 feet or more... would that be a viable (relatively) high speed X-country airplane? Or are there design tradeoffs between making something so light and optimizing it for high altitude flight (the need for breathing O2, notwithstanding).

The one obvious drawback here is that if this company went belly-up, it seems quite a bit more advanced than anything else in the marketplace, so your design would go along with the fortunes of the experimental engine manufacturer (historically, that's not a good bet). Anyway, it seems like a pretty big step in terms of lbs/hp, at least as far as the slow/cheap/economical end of the spectrum tends to go.

I'm sure some people here can generate some good thoughts on this..

That motor is pretty tall for it's size and weight and reduction drive setup. Meaning it would be tough to package into a clean structure that is small without a giant spinner or something like that. But that could be done. 65 hp with a high aspect ratio wing and pretty light weight could be a nice cruiser. Doesn't have to be tiny. Could be slightly more span than say an AR5 with similar performance if you were real careful about interference drag and maybe even made it a pusher instead of a tractor. No need to go higher than 10k for a nice fast cruise with no oxygen onboard during the summer. You could have heat on board from the engine easily with some ducting. Can't remember how much hp the Mooney Mite had but it wasn't much. That is a small aircraft with great performance and great design details.

 

[SVSUSteve]

You could have heat on board from the engine easily with some ducting.

You just have to be very careful how it is designed, built and maintained or you have an airborne equivalent of the Gaswagen used by the Einsatzgruppen. More than one homebuilt I've personally seen has had major problems with the homebuilt heating system because of poor design and/or shoddy construction.

Can't remember how much hp the Mooney Mite had but it wasn't much. That is a small aircraft with great performance and great design details.

But it was a single seat, severely range limited aircraft (<500 miles) that weighed less than 800 lbs fully loaded. They are a fun aircraft to fly (a friend of mine owns one) but they aren't exactly what I would classify as a "cross-country" airplane anymore than I'd classify the ultralights I have flown as such.

FROM WIKIPEDIA
General characteristics

• Crew: one pilot
• Length: 18 feet 0 inches (5.49 m)
• Wingspan: 26 feet 10 inches (8.18 m)
• Height: ()
• Airfoil: NACA 64A215
• Empty weight: 520 lb (236 kg)
• Loaded weight: 780 lb (354 kg)
• Useful load: 260 lb (118 kg)
• Max. takeoff weight: 780 lb (354 kg)
• Powerplant: 1 × Continental Motors C-65 wooden propeller, 65 hp (48 kW)

Performance

• Maximum speed: 138 mph (222 km/h)
• Cruise speed: 125 mph (201 km/h)
• Stall speed: 43 mph (69 km/h)
• Range: 440 statute miles (708 km)
• Service ceiling: 19,400 feet (5,900 m)
• Rate of climb: 1090 ft/min (5.53 m/s)
• Power/mass: 12 lb/hp (0.14 kW/kg)

 

[Grimace]

The question is why would you want to be exposed to the cold air temperatures and hypoxia of those altitudes in something small enough to be a "speedster" with a 65 hp engine?

Because you could go fast while burning something like 3gph? That seems like a good enough reason.

It depends on what you are comparing it to when you say "relatively"? A Cessna 172? An Aeronca? A car? A bicycle? Amtrak?

Well, let's start by comparing it to other alternatives, say comparable homebuilt aircraft that could be completed for less than $40K, or acquired for about the same.

By aviation terms, nothing with a 65 hp engine is going to be "high speed".

It's a relative term. Surely you are smart enough to comprehend that. I am not talking about mach 3 here, nor do I wish to specify a specific speed to be picked apart by dweebs with nothing better to do. Just suffice it to say "fast in accordance with general aeronautical principles for the power produced".

Even with an LSA size limitation attached to it (which is to say you kill the marketability as a means of cross country travel thanks to limits on fuel volume, baggage and passengers), you'd probably sit right at 100-110 knots.

Who mentioned anything about LSA? And it seems to me quite a few aircraft have already gone quite a bit faster than that on similar hp.

You get up to 14,000 feet, not only is it going to be cold and have reduced oxygen levels, you're starting to get into territory where it's not uncommon to have a calm day involving a 10-20 knot wind. Looking on Fltplan.com for a flight Denver to here at 16,000 feet, I could be facing up to a +17 knot headwind and that's pretty modest. That pretty much offsets whatever benefit you might see in a "turbonormalized 65 hp" engine powered "speedster"

Well, I'm not imagining an airplane that is required to maintain a specific flight level. I would think that, like most aircraft, it would be capable of flying at one altitude when the winds are with you and an entirely different altitude when winds are against you. Heck, it might even be capable of flying low enough to touch the ground, you know, to land and stuff. So really, it would be capable of flying at different altitudes.

Are you a pilot currently?

Nope. I got to about 25 hours of flight training, money was tight, and I realized there isn't a damned practical thing I could do with a pilot's license except waste more money on meaningless flights. Since then, I've done little more than entertained the idea of hopefully finding something compelling enough, performance-wise, to justify the time and expense of continuing that endeavor.

And if that's a reference to the full-rated hp not being the typical hp at cruise, well, then forgive my simplistic language. Nevertheless the question still stands as to whether there are, aerodynamically speaking, tradeoffs for high altitude performance. This is an interesting question to me, if for no other reason than in my years of aviation background and training, I've never heard of, or seen, such a low power engine available, which could so ably compensate for altitude. So, please, even if it's just a pipe dream, indulge my curiosity. How does taking a small single-seat aircraft designed for 65hp up to an altitude of 20,000 feet differ from doing the same for, say a 6-seat twin-engined aircraft built around, say, TIO-360's?

 

[Jay Kempf]

You just have to be very careful how it is designed, built and maintained or you have an airborne equivalent of the Gaswagen used by the Einsatzgruppen. More than one homebuilt I've personally seen has had major problems with the homebuilt heating system because of poor design and/or shoddy construction.

Yup. Assume design that doesn't include asphyxiation. There are plenty of good examples out there as well as there are bad examples. Probably the oldest design is a heat muff. But yeah anytime you mix potential breathing air with hot exhaust or cooling air both from the engine compartment there is always the potential to design a lethal contraption.

 

[Grimace]

The Mooney Mite isn't a bad example. I'd think 140kts cruise would be a reasonable conservative target (though the MM was referenced in mph). Of course if we were to use hyper-modern techniques like composite construction and enclosing the engine with a full cowling, we might be able to do even a bit better...

Winds nothwithstanding, 140kts cruise would be 190kts at FL180. And, if the winds were with you, who knows how fast you could get somewhere...

It seems to me that there's really nothing out there designed to take advantage of high altitudes with this little hp. I'm just wondering if it's an aerodynamics thing, or if nobody's really tried to design a fast high altitude airplane for such low power (which may be understandable for a variety of reasons, I suppose). But would this be an unfilled niche? Or wild goose chase?

 

[djschwartz]

Because you could go fast while burning something like 3gph? That seems like a good enough reason.

Hardly! Just ask yourself, "Why isn't everyone, or even any significant number of folks, cruising around in the equivalent of a Formula 1 racer today?", or, "What happened to the formula V types that were supposed to be really fast and really inexpensive and fly on small converted VW engines?" Simple. Because sacrificing everything for speed results in a very uncomfortable aircraft with little or no utility and more challenging handling characteristics. So you have to include include some level of comfort and utility in your investigation if you want to appeal more than a very tiny fraction of the flying community. That discussion has been had ad nauseum on this forum and in other venues.

 

[Grimace]

Hardly! Just ask yourself, "Why isn't everyone, or even any significant number of folks, cruising around in the equivalent of a Formula 1 racer today?", or, "What happened to the formula V types that were supposed to be really fast and really inexpensive and fly on small converted VW engines?" Simple. Because sacrificing everything for speed results in a very uncomfortable aircraft with little or no utility and more challenging handling characteristics. So you have to include include some level of comfort and utility in your investigation if you want to appeal more than a very tiny fraction of the flying community. That discussion has been had ad nauseum on this forum and in other venues.

Again, "fast" is a relative term which I would rather not define concretely at this point as it's just an idea floating in my head. 150mph seems pretty fast to me, relative to driving. And it also seems within the realm of feasibility with modern composites and laminar flow airfoils. I'm not imagining a race plane here... just something that can take advantage of thinner air with turbo-normalization in a relatively low hp application. I'm just wondering if there are any aerodynamic "gotchas" beyond the obvious...

 

[SVSUSteve]

Because you could go fast

Like I said, define "fast". A 120 knot cruise speed at an altitude where at least half the time you're likely to have a 10-30 knot headwind isn't "fast" in my book. Down low on calm windless days, 120 knots feels like you're qualifying at the Speedway here in Indy, but at the flight levels, it seems like you're going very, very slowly.

while burning something like 3gph? That seems like a good enough reason

When my fiancee's Kia gets 30 mpg on the highway which breaks out to about 2.5 gph. The difference is that a 20-30 knot headwind in cruise isn't going to make the car slower than the airplane.

If you just want to fly something that sips fuel, then just say so or do it. Not everything has to be everything to everyone. You want to go high, you want to go fast, you have to trade things off especially if you want to do it safely or comfortably.

Who mentioned anything about LSA?

Because for 65 hp to push anything more than a hundred or so knots you are most often limited to single or two seat aircraft which tends to put it within the weight class of LSAs, performance notwithstanding. I was referring to the number of seats and the MTOW of the aircraft and not the cruise speed limitation associated with "true LSAs".

And it seems to me quite a few aircraft have already gone quite a bit faster than that on similar hp.

Examples please, preferably not one off "Gee look what I can do!" ones either.

Nope.

That's what I figured.

And if that's a reference to the full-rated hp not being the typical hp at cruise, well, then forgive my simplistic language.

It was a reference to most of your lines of reasoning which show that you're most likely new to the hobby both as a pilot and as a designer. Pie in the sky logic and "I can make it work!" attitudes tend to be strongly associated with people who possess little in the way of practical experience. You occasionally see it in people with more experience but it's most often the realm of student pilots, newly minted PPLs, non-pilots and- worst of all- kids who want to build an airplane.

I've never heard of, or seen, such a low power engine available, which could so ably compensate for altitude

The general rule is that if there's not a common or readily available engine to do something, there's probably a reason why someone isn't making them. There's little need for a turbocharged 65 hp engine unless you're one of the few who thinks that flight just below the flight levels in an unpressurized aircraft with only a marginal amount of horsepower even with the turbocharging is a great and fun thing or you have an urge to race go-karts up Pike's Peak.

How does taking a small single-seat aircraft designed for 65hp up to an altitude of 20,000 feet differ from doing the same for, say a 6-seat twin-engined aircraft built around, say, TIO-360's?

Because that six-seat aircraft has a reason for existence (to get people from point A to point B) and has the power to sustain an adequate cruise speed at that altitude for cross-country flight. As I pointed out before, if you just want to fly, there's plenty of puttering around at low altitude to be done with lower horsepower aircraft. Trying to push an aircraft to its ceiling with a marginal engine even at low altitude is a great example of that old adage about "just because you can do something does not mean that you should do it."

The other point I will make is let's say you have a range of a Mooney Mite (roughly 500 miles) and want to use it. For the sake of expediency, let's say you're able to climb 1,000 feet per minute at 100 knots ground speed (pulling nice round numbers out of my ass for the sake of discussion here....as a general rule, your ground speed will drop as your climb rate goes up and your climb rate will drop as you climb but let's ignore that). You want to climb to say 16,000 feet from an airport at sea level. That puts you in climb for 16 or so minutes and puts you about 27 miles from your point of departure. You then level off to cruise at 120 knots (assuming that the winds aloft are magically zero or at least oriented in such a way that they are not a factor) and it's 448 miles to your top of descent (let's say 25 miles from your destination and riding the plane down at ground speed of 140 knots (you're coming down fast, near Vne, pretending that you're the Space Shuttle for the sake of argument) ). So we've got roughly:

16 minutes (0.27) climb time
3.75 hours in cruise
18 minutes (0.3) descent time (@ just over 800 fpm to 1000 feet AMSL)
4.32 hours to go 500 miles

Versus, a 4000 foot AGL cruise which gives you three to four minutes in climb, probably two in descent to the traffic pattern and the rest (let's say all but ten miles) at 120 knots.

5 miles @ 100 knots = roughly 3 minutes
490 miles @ 120 knots= 4.1 hours (roughly)
5 miles @ 140 knots= 2.15 minutes
4.2 hours approximately to go 500 miles.

You could very well end up with a longer flight because you're trying to fly higher. It's an oversimplification, but just trying to make the point that despite what some like to believe, there's not always a benefit to flying higher unless you have something in your way. If that something requires you to be at 14,000+ feet to have clearance, it might be wise to do it with more than the marginal reserve of a 65 hp engine since mountains aren't anything to trifle with because of the winds associated with them which can rip even an airliner apart (BOAC Flight 911 - Wikipedia, the free encyclopedia). I'm not trying to kill your dream, I'm just trying to give you food for thought and to help you avoid chasing windmills when you could be working on a practical design to suit your needs.

 

[Dan Thomas]

Because you could go fast while burning something like 3gph? That seems like a good enough reason.

Most small engines don't get really good SFCs. My A-65 burns 5.5 GPH at sea level and I never see less than 4.5 or so. The two-strokes are much worse. The A-65's larger brothers get better fuel mileage for their HP.

Dan

 

[SVSUSteve]

Winds nothwithstanding, 140kts cruise would be 190kts at FL180.

How do you figure?

And, if the winds were with you, who knows how fast you could get somewhere...

...or how the aircraft gets overstressed and you wind up finding out what the terminal velocity of the cockpit is as you plummet towards the ground.

It seems to me that there's really nothing out there designed to take advantage of high altitudes with this little hp

As pointed out before, there's a good reason for that. Both DJSchwartz and myself have given you a litany of reasons why.

I'm just wondering if it's an aerodynamics thing, or if nobody's really tried to design a fast high altitude airplane for such low power (which may be understandable for a variety of reasons, I suppose).

If it's 'understandable' why it has not been done, then why would one want to put in the several thousand hours required to design and build even a simple aircraft to do that?

I'd think 140kts cruise would be a reasonable conservative target

Dream on.

(though the MM was referenced in mph)

You do realize that 125 mph is about 108 knots right because a nautical mile is further than a statute mile? So for 140 knots you're talking about 162 miles per hour. Please tell me you realize the disconnect between a 65 hp engine and a vehicle capable of cruising at (not max speed) 162 miles per hour.

Of course if we were to use hyper-modern techniques like composite construction and enclosing the engine with a full cowling

"Hyper-modern"...that's a good one. Homebuilders are still using the composite techniques of the 1970s and probably will be for the foreseeable future as more or less the "rule" rather than the exception to it.

But would this be an unfilled niche?

No.

Or wild goose chase?

Yes.

 

[SVSUSteve]

Again, "fast" is a relative term which I would rather not define concretely at this point as it's just an idea floating in my head.

Yup. I know.

150mph seems pretty fast to me, relative to driving.

It's also practically not possible with the engine you're discussing in anything but a very, very cramped aircraft with spartan accommodations.

And it also seems within the realm of feasibility with modern composites and laminar flow airfoils.

To someone who doesn't know much about those technologies or aircraft in general, yes, it does seem that way. "Seems" is the key word in your statement.

I'm not imagining a race plane here...

Basically for the weight class necessary to get a 65 hp powered aircraft that high up, yes you are.

just something that can take advantage of thinner air with turbo-normalization in a relatively low hp application.

What are the real advantages of higher (really, middle altitude flight) in any direct sense? You're talking about flying into a rather hostile environment where unacclimatized folks can easily suffer ill effects (acute mountain sickness, etc) simply by rapidly ascending to those altitudes. It's cold (extremely cold such as an average of -20 C at 18,000 feet; try it in a poorly heated or unheated non-pressurized cockpit and it'll take a week for you to thaw out enough that your penis and testicles are once again visible), the air is thinner (so a lower partial pressure of oxygen), the winds are higher (previously discussed) and so there are huge tradeoffs to "taking advantage of" higher altitudes. If you're not careful and very, very cautious, it's a very good way to end up doing the flying equivalent of bending over and grabbing your own ankles.

 

[Lead Brick]

I think it would be a good match for a Quickie Q2. You'd have to redesign the cowling, but whatever. We're talking hypothetically here right?

 

[Grimace]

Like I said, define "fast". A 120 knot cruise speed at an altitude where at least half the time you're likely to have a 10-30 knot headwind isn't "fast" in my book. Down low on calm windless days, 120 knots feels like you're qualifying at the Speedway here in Indy, but at the flight levels, it seems like you're going very, very slowly.

AT LEAST half the time? Come on now. That just pegs you as a pessimist. If you had said 50/50, I could go along with it...

If you just want to fly something that sips fuel, then just say so or do it. Not everything has to be everything to everyone. You want to go high, you want to go fast, you have to trade things off especially if you want to do it safely or comfortably.

For me it's more of a question of what can it do WHILE sipping fuel? I mean, we can fly an ultralight burning 2gph. I'd want more performance than that. This is just a question of what's possible. I've asked at least 2 or 3 times... is there an aerodynamic drawback to low hp designs at high altitude. I want to know if there's a ratio, rule of thumb, or something that says "Nope, you aren't going to do very well at altitude with such marginal power." I know it's not going to be fast like an RV, or a Lancair. I'm not expecting that. But I'm wondering if there can be a hint of added performance brought to a design by having the capability of going high... or is the idea of turbocharging such engines merely a waste of time.

As best I can tell, the biggest issue is the inability to use Constant Speed props, but nobody here has yet had the brilliant analytical mind to bring that matter up. I wish they had. The person with the analytical mind capable of bringing up even that simple point would almost certainly be worth talking to.

Because for 65 hp to push anything more than a hundred or so knots you are most often limited to single or two seat aircraft which tends to put it within the weight class of LSAs, performance notwithstanding. I was referring to the number of seats and the MTOW of the aircraft and not the cruise speed limitation associated with "true LSAs".

I'm referencing a single seat design, but not LSA restrictions. I thought that would have been clear by my initial posts and also the international nature of this forum. My apologies.

Examples please, preferably not one off "Gee look what I can do!" ones either.

Well, if you've been around aviation as long as I have, you know how hard it is to come up with high performance planes with less power than a standard VW conversion.. but I'll try to provide some data points for the sake of discussion... I'll even ignore the one-offs (such as the AR-5 which prove what is POSSIBLE)..

KR1... 80hp 180mph (spec'd to fly with 60hp, probably has a cruise around 150-160 with that power.)
Hummelbird... 32hp 115mph (that's almost 120mph with less than half the horsepower we are discussing)
Sonerai I... 60hp 150mph
BD-5B... name your engine, these things would cruise more than 120mph on 65hp
Wittman V-Witt 1600cc 150mph (I believe a 1600cc VW is about 65hp. Correct me if I'm wrong)
Sambada US-10 65hp 152mph
Quickie Q2 65hp 140mph

As reported, those speeds I listed are cruise speeds.

That's what I figured.

It's hard to justify a pilots license when I can get 40mpg on a motorcycle that goes 0-60 in less than 3 seconds. But I do have my A&P and considerable composites manufacturing experience for you to turn your nose up at, if you'd like.

It was a reference to most of your lines of reasoning which show that you're most likely new to the hobby both as a pilot and as a designer. Pie in the sky logic and "I can make it work!" attitudes tend to be strongly associated with people who possess little in the way of practical experience. You occasionally see it in people with more experience but it's most often the realm of student pilots, newly minted PPLs, non-pilots and- worst of all- kids who want to build an airplane.

I think you are mistaking me for some bull-headed self-confident know-it all. If I've failed to heed good advice in either of the two threads I've started recently, let me know. If I've asked honest questions, and brought what I felt were different ideas to the table and defended them in the face of all evidence to the contrary, then I guess that's on me... but I think you are painting your own prejudices on me and it's rather distasteful and most undeserved, I assure you.

The general rule is that if there's not a common or readily available engine to do something, there's probably a reason why someone isn't making them. There's little need for a turbocharged 65 hp engine unless you're one of the few who thinks that flight just below the flight levels in an unpressurized aircraft with only a marginal amount of horsepower even with the turbocharging is a great and fun thing or you have an urge to race go-karts up Pike's Peak.

Well now, go kart racing up Pikes Peak does sound like fun, and if you think otherwise, you are a boring old fart. And I can think of lots of reasons why people aren't making low-powered turbo'd engines for airplanes... but "nobody is doing it" isn't a very persuasive argument as to why it isn't being done, so I would be greatly appreciative if you could please do better to enlighten me.

If I disagree with you, I'm sure it's only because I do not understand. But I assure you I am neither bull-headed, nor arrogant. A good amount of logical and insightful, detailed information would most assuredly sway my thinking. And I'm still waiting.

The other point I will make is let's say you have a range of a Mooney Mite (roughly 500 miles) and want to use it. For the sake of expediency, let's say you're able to climb 1,000 feet per minute at 100 knots ground speed (pulling nice round numbers out of my ass for the sake of discussion here....as a general rule, your ground speed will drop as your climb rate goes up and your climb rate will drop as you climb but let's ignore that). You want to climb to say 16,000 feet from an airport at sea level. That puts you in climb for 16 or so minutes and puts you about 27 miles from your point of departure. You then level off to cruise at 120 knots (assuming that the winds aloft are magically zero or at least oriented in such a way that they are not a factor) and it's 448 miles to your top of descent (let's say 25 miles from your destination and riding the plane down at ground speed of 140 knots (you're coming down fast, near Vne, pretending that you're the Space Shuttle for the sake of argument) ). So we've got roughly:

16 minutes (0.27) climb time
3.75 hours in cruise
18 minutes (0.3) descent time (@ just over 800 fpm to 1000 feet AMSL)
4.32 hours to go 500 miles

Versus, a 4000 foot AGL cruise which gives you three to four minutes in climb, probably two in descent to the traffic pattern and the rest (let's say all but ten miles) at 120 knots.

5 miles @ 100 knots = roughly 3 minutes
490 miles @ 120 knots= 4.1 hours (roughly)
5 miles @ 140 knots= 2.15 minutes
4.2 hours approximately to go 500 miles.

You could very well end up with a longer flight because you're trying to fly higher. It's an oversimplification, but just trying to make the point that despite what some like to believe, there's not always a benefit to flying higher unless you have something in your way. If that something requires you to be at 14,000+ feet to have clearance, it might be wise to do it with more than the marginal reserve of a 65 hp engine since mountains aren't anything to trifle with because of the winds associated with them which can rip even an airliner apart (BOAC Flight 911 - Wikipedia, the free encyclopedia). I'm not trying to kill your dream, I'm just trying to give you food for thought and to help you avoid chasing windmills when you could be working on a practical design to suit your needs.

Yup. Climb takes time away from cruise. I get that. But before you pull out random numbers, can we at least start to approach numbers that would be representative of what such an aircraft might actually look like? I think that would be much more persuasive and more easily allow me to see the errors of my inferior logic. 150mph cruise seems completely attainable, based on the several examples I listed above. I'm just trying to understand here.

And come on man, when I referred to "hyper modern" and "enclosed engine" in the same breath, I assumed you'd catch the humor. Do you really consider cylinder heads sticking out in the breeze to be a modern design approach?

 

[Detego]

AeroTwin Turbo Charged Engine:

• 65 HP @ 4200 RPM
• Weight: 100 lbs (135 lbs)
• Oil Tank Weight: 8lbs
• Gear Reduction Box w/ Centrifugal Clutch: 27 lbs
• Dimensions (Height): 17.5"
• Air Cooled 972cc 4 Stroke
• Bore: 101.6
• Stroke: 60mm
• Fuel Octane Requirement: 91UL


AEROTWIN Turbo 65 HP (48.5 KW)

Torque = HP X 33,000/(2 pi RPM)
or
65 X 33,000/(2 pi 4200) = 81 ft. lbs.


Static Thrust 68" Diameter Propeller
7.38 X (65 X 68/12) .67 = 376 lbs.*



* Same Thrust & as ROTAX 532 w/2.58 Gear Reduction (see used market).

 

[SVSUSteve]

AT LEAST half the time? Come on now. That just pegs you as a pessimist. If you had said 50/50, I could go along with it...

No, today is a very mild day. It's very unusual for there to be less that what we are seeing today so I am not being pessimistic. Just because it doesn't meet your expectations or proves to be a burden does not make it pessimistic.

But before you pull out random numbers, can we at least start to approach numbers that would be representative of what such an aircraft might actually look like?

Those are very middle of the road performance numbers for an aircraft of the size, power and configuration you are talking about. The reason I used "roughly" is simply because of the effects of winds, et cetera.

KR1... 80hp 180mph (spec'd to fly with 60hp, probably has a cruise around 150-160 with that power.)
Hummelbird... 32hp 115mph (that's almost 120mph with less than half the horsepower we are discussing)
Sonerai I... 60hp 150mph
BD-5B... name your engine, these things would cruise more than 120mph on 65hp
Wittman V-Witt 1600cc 150mph (I believe a 1600cc VW is about 65hp. Correct me if I'm wrong)
Sambada US-10 65hp 152mph
Quickie Q2 65hp 140mph

How many of those operate at high altitudes (and are thus equipped with heating, oxygen systems, seals on the doors etc) and how many of them have you set in?

I can tell you right now that a KR-1 or KR-2 is not a comfortable aircraft for anyone of average size (and I'm literally the 50th percentile adult American male in every aspect pertinent to cockpit layout). Ken Rand was a tiny little fellow (5'5" or so and about 160 lbs from what I have been told) and designed his aircraft to fit himself. Trying to design to fit someone who is taller, broader and heavier is going to require a larger cockpit and therefore more drag. As well as the need to account for the weight of an average adult American (200 lbs or so) which will require a larger wing if you want a decent amount of baggage. Then if you want to bring along a friend (which most of us do)....

The Sonerai I has a 300 statute mile range so it's not exactly a "cross-country airplane". I've flown one. They are a fun plane...actually they are a ****ing blast to fly. However, it doesn't meet most people's idea of a cross-country plane.

As for the Hummelbird, that's definitely not a plane you want to spend a lot of time in. It's like wearing a sweater designed for a child. File:Skeet Wyman Hummelbird.JPG - Wikipedia, the free encyclopedia Take a look at one compared to some adults and you'll see what I mean.

The Bede design...well, if you think you're that talented of a designer....I mean between Jim Bede and Burt Rutan that aircraft has one hell of a pedigree.

The Quickie is a heck of a design but it's severely lacking in range (about 500 miles) and, once again, look at who designed it. Mr. Rutan is a bit better versed in aircraft design than most.

The Sambada? Never heard of it.

150mph cruise seems completely attainable, based on the several examples I listed above. I'm just trying to understand here.

150 mph at say 8,000 feet is one thing if you're willing to sacrifice comfort, range and- to a large degree- safety if something were to go wrong. 150 mph at 18,000 is entirely another simply because of the requirements to protect occupants from the environment.

-20 C temperatures are not to be trifled with. Human skin freezes very quickly at temperatures around that (Proc. Am. Phil. Soc. 89: 177–199, 1945 if you want to fact check) and that's even without the help of a 150 mph slipstream. Lose a window or something and you're instantly blinded by the wind. There are a lot more factors at work here than just "Can you build an airplane that will go fast at X ft?"

As best I can tell, the biggest issue is the inability to use Constant Speed props, but nobody here has yet had the brilliant analytical mind to bring that matter up.

The biggest reason they aren't normally used on small aircraft (those just above the weight limit of the LSA category) is a simple one: weight. If you are trying to achieve the goals you've set for yourself, you're going to have to keep the weight down.

I wish they had.

Why? It adds complexity and weight to a category of aircraft that are meant simply to be for the "fun" of flying. That said, I suspect that the primary reason behind the entire sport pilot movement was a thinly veiled attempt (in the safest way possible: light slow aircraft with as few people on board as you can get by with) at proving or disproving the ability of pilots to medically self-certify.

I'm referencing a single seat design,

Noted. You might be able to pull off the performance you want in terms of speed but I continue to staunchly argue against the altitude concept. That said, if you simply want to go fast and there are planes that accomplish that in the category you're looking at, why go through the trouble of designing your own? It's a much bigger headache than you likely imagine.

but not LSA restrictions. I thought that would have been clear by my initial posts and also the international nature of this forum. My apologies

However you want to look at or try to justify it- other than speed- you're talking about an LSA for all intents and purposes.

It's hard to justify a pilots license when I can get 40mpg on a motorcycle that goes 0-60 in less than 3 seconds.

Which has what to do with the discussion at hand?

But I do have my A&P and considerable composites manufacturing experience

...and? You speak like someone who has no background whatsoever so it was an educated guess that you're a rank newbie to the world of aviation. What was I supposed to suspect about someone who acts as though they don't an aileron from their asshole?

for you to turn your nose up at, if you'd like.

I probably have as much experience with regards to aviation safety, human factors, crash survivability and related topics as anyone on this forum (since it's what I do for a living) so if you want to stop turning your nose up at my area of expertise. You have just gotten your tail in a knot over the fact that a couple of us have pointed out that your goal of having your cake and eating it too is not likely to happen and even if it does, you will be very likely to end up getting yourself hurt with the attitude that "I can overcome that!" that you've demonstrated on this thread. No offense intended but if others haven't done it before and it's not a common practice there's probably at least a few dead people (or at least a lot of failed designs) to explain it.

Towards that end, I'll leave you with a quote from Douglas Adams: "Human beings, who are almost unique in having the ability to learn from the experience of others, are also remarkable for their apparent disinclination to do so." That disinclination is exactly what I'm seeing in you and I have seen in before in another friend of mine. His name was Daniel Lloyd and I'd suggest that you two have a long talk but unfortunately, when his hubris finally caught up with him they identified Daniel by his dental records and fingerprints. I don't take saying that lightly nor do I wish to quash the desire to move the world of aviation forward but you asked what the challenges where and I have gone over a lot of them for you. You can take that as either my being a dick or you can look at them and use them to improve your goals and the design that is trying to meet them.

 

[Lead Brick]

If you haven't read this, it is worth the read. http://www.vansaircraft.com/pdf/hp_limts.pdf

 

[Grimace]

You know... rather than respond... I'll just thank Steve for his excellent and perfect advice! Thanks, Steve! It's all clear to me now. Thanks for helping a newbie understand.

 

[psween]

Aside from all the extra stuff that's been going on in this thread, there are some very good kernels of info. I too have played with the numbers for a high altitude personal cruiser type plane. It might help to better define high altitude and what kind of speeds constitute "cross country" capability. For some folks (I believe SVSUSteve might be one, but correct me if I'm wrong) cross country means literally across the country, so upwards of 1000nm range at a speed that won't have you sitting in the plane for 8-9 hrs., combined with altitudes in the flight levels that gets you above most weather and all terrain. That's one take on a cross country plane, and it's a valid one.

My personal take, which looks like it might align better with the OP and other GA pilots, is a plane with room for 1-2 people, comfortable enough seating to handle 5-6 hours legs, speeds in the 140-160 KTAS range, capable of cruising in the mid teens. My choice for this mission is a KR derivative, but there are other options out there.

I know this doesn't address the original question at all, but it seems that better defining a mission, vs. talking in generalities about "high altitude" or "cross country" planes might go a long way toward avoiding what seems to be mostly issues of semantics.

To steer back to the topic, what I'd do with an altitude compensated 65 horse motor is stick it in an airframe already designed around 65 hp, then do whatever that airplane is capable of doing, but maybe a bit higher! Doesn't need to be practical, or "cross country", or flight at 30k ft. to be informative or fun.

Patrick