Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by KC135DELTA, Aug 7, 2007.

1. Aug 7, 2007

### KC135DELTA

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Hello again everyone,

I've made posts here before about the spending of money in aviation but never the makeing of it. My idea is simple: Giving pilots who arn't millionaires or master craftsmen the ability to fly a decent distance at a decent speed with a decent cost in a certified airplane (I know this forum is not about certified aircraft but this corner of aviation is one of the few where the pilots know their mechanics very well). So here is what I had in mind.

- 200knots - more if possible
- simple retracts
- room for 4 adults comfortably with baggage or 6 in high density
- stall speed of 45-50knots
- conventional construction with aluminum
- conventional engine - I was thinking 250-300 hp.
- extensive use of low drag aerodynamics to maximise the performance
- 800-1,000 miles of range.

Essentially I was thinking a very slick low drag fuse attached to a slick wing (I was thinking low wing) with the wing haveing some features you see on stol aircraft such as a large flaps *leading and trailing to maximise low speed performance without sacrificing the high speed cruise also. I've had my mind on weights but I don't want to set anything in stone so we will just develop those as we go to best fit us. Also the avionics would be kept simple with options to upgrade to glass or whatever mix best suits the customer.

Anyone interested?

Edit: I was thinking we could incorperate some of the simpler enhancements that you see on experimental aircraft to help pull it above the rest.

Last edited: Aug 7, 2007
2. Aug 7, 2007

### Rhino

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Sounds a lot like a Lancair.

3. Aug 7, 2007

### orion

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Generally, when considering a "true" four place configuration, the list tends to boil down to precisely the items you list. We've gone down this path with numerous customers over the years and each time the stated goal represents this particular class of airplane, the load, performance and layout numbers tend toward relatively consistent values. And they should since the numbers you present fall within the feasibility envelope for that class of airframe. Yes, there are a few issues that might force a bit of compromise but overall the feasibility is there.

But as you might guess, there is a catch: $So let me take a closer look at your statements and just provide my 2 cents worth: I know this forum is not about certified aircraft Since all airplanes start as "Experimental", whether slated for certification or not, nothing wrong with talking about it here. Giving pilots who aren't millionaires or master craftsmen the ability to fly a decent distance at a decent speed with a decent cost in a certified airplane Noble sentiment but as they say, "The devil is in the details". The three biggest drivers of airplane cost are simply the cost of certification, the limited market and insurance. The costs of developing a prototype aircraft aren't actually all that high and if you look at the specific issue of certifying the airplane, that too can potentially be done at a "reasonable" level. But where the real numbers come in is in the setup and certification of the factory and production line. Adding to that, it is the nasty little details of employee costs, the G & A expenses, tooling, machinery, etc. that add up to figures that make this endeavor a questionable investment. The limited market pretty much addresses what you have to charge in order to keep the company going, even when the market demand cools off. If we operated in the same numerical realm as automotive production then, like Detroit, we could suffice with small profits (average car manufacturing profits are only about$500 per car - give or take a bit) making up the bottom line with volume production.

Airplanes however operate in a much more limited market. As an example, we now have a bit over 500k registered airplanes in the US. In car numbers, that represents two to three years production of maybe just one model. As such, given the limited market, profits need to be substantially higher if the company is to survive. Furthermore, quite a bit of cash has to be re-invested back into the company since no airframe manufacturer has ever survived too long selling only one model. You need to come out with the next new model within about three to five years from initiation. In short, the flow of cash has to be continuous in order for the company to last more than a few years. (Yes, this is all a gross oversimplification but it does need to be at least touched upon in this type of discussion.)

And then you have insurance. I don't know how much insurance plays into the cost of each airframe today but in years past the number was as high as 30% - some estimates I've heard were even higher.

That makes it tough to provide the "affordable" product. Yes, it's possible but you better really know your market before diving in.

- 1,000 pound useful load; - 200knots - more if possible

Good goal. My Pathfinder has a bit over 1,000 pounds of payload and it does make for a very usable airplane. However, it'll do over 200 knots only in a dive, with no wings. Utility and speed are often at odds, especially if you then add things like slow stall and possible short field capability. It's not impossible but there are cost involved, especially in the choice of power-plant.

- simple retracts

This is a very relative term - simply said, no such thing. The moment you add the mechanisms, the hydraulics, the support systems, the necessary structure, simplicity goes out the window. Yes, with proper design and configuration you can control these issues, but only to a point. But given your goals, retracts can be a detriment since they will affect the bottom line, thus again affecting the "affordable" goal.

- room for 4 adults comfortably with baggage or 6 in high density

This represents a relatively large airplane - will need quite a bit of power to make the 200 knot goal.

- stall speed of 45-50knots

Good goal - will however require either a substantial flap system or a bit more area than optimal for the higher cruise speed goal. More area is generally preferred since you'll need a sizable wing anyway to fit the fuel, the landing gear, the controls, etc.

- conventional construction with aluminum

Not necessarily the cheaper alternative. The metal airframe generally results in high part counts and substantially longer assembly times than with an optimized composite design. It is also difficult to fabricate the low drag components that will be needed to meet the performance goals.

- conventional engine - I was thinking 250-300 hp.

Will probably have to be on the upper end of that range to meet the 200 mph mark for a small six place (or large four place).

- extensive use of low drag aerodynamics to maximize the performance

Aerodynamics is not magic - no special shaping will make you go faster, no special airfoil will revolutionize your performance. Optimal aerodynamics is a game of a few percent here, a fraction of a percent there. The only reason that most homebuilts outperform their certified counterparts is simply because they're a lot smaller and generally have much higher power-to-weight ratios.

- 800-1,000 miles of range.

Ideal goal but keep in mind most pilots tend to plan around two hour cross country legs, especially when flying with spouse and/or kids.

Essentially I was thinking a very slick low drag fuse

Difficult to do with aluminum unless you invest in some pretty pricey tooling and fabrication processes.

For small aircraft the leading edge flaps generally don't provide sufficient benefit to overcome the increased complexity, weight and loss of usable volume. It is also relatively difficult to arrive at a perfectly clean leading edge flap installation - the worst example of this is on the Helio where the leading edge slat has as much as a 1/4" gap between its trailing edge and the main wing skin. Yes, you can do a lot better but there is a good percentage chance that the leading edge devices will provide the airframe with a bit of a drag penalty.

In short, your goals are noble and yes, would make for a very nice, usable aircraft. But it is the getting there (finished airplane) from here (idea) that is the real challenge, especially if you have to fund the project out of your own pocket. And if history proves anything, finding investors for a "small" airplane is the exception, not the rule. But if you have ideas on how to solve the roadblocks, I'm sure we'd love to hear them.

4. Aug 8, 2007

### KC135DELTA

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Thanks for the fast reply. I think I'm leaning more towards speed than utility. Also should those Jet-A diesel's be considered? I hear they produce 30% more power on the same volume of fuel.

5. Aug 8, 2007

### Midniteoyl

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More like the (now defunked) Express, exactly.... except for the aluminum...and the retracts

Last edited: Aug 8, 2007
6. Aug 8, 2007

### Rhino

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Or the new Lancair they just announced, except for the aluminum of course. I don't think they plan six seats, but the cabin is considerably larger than the IV, and the payload is up quite a bit as well.

Whatever the case, many many people have tried to develop an aircraft with the above stated goals, but the price always manages to be about the same as what's already out there. I wish KC135DELTA the greatest of luck, and I hope he succeeds. But I'm not holding my breath at this point.

7. Aug 8, 2007

### orion

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Some time back I heard Express (or one of the kit owners) was working on a retract configuration but I'm not sure what happened to it. But you're right, the criteria above does sound a bit like the Express, although I think you'd have a hard time getting six seats in the airplane, even if the passengers were kids.

Regarding Diesels, for now I'd say don't hold your breath. Despite much initial energy and publicity, even the most promising developments don't seem to be reaching production as of yet. Also, the initial pricing estimates for the one or two engines going down the road of certification are high enough that they make Lycomings look like bargains.

Looking at your criteria, you'll probably need about 300 hp or better to exceed 200 knots with an airplane of the size you're shooting for. That pretty much confines you to the higher end Lycs or Continentals, although if performance is you main goal, then probably the most realistic choice from a that standpoint will be some of the smaller turbines - somewhere in the size class of the Allison 250 or so. But then again you get to the issue of affordability.

In doing this type of endeavor it is possible to control and limit the cost of many of the associated issues. However there are some that you just can't get past and you end up having to live with what's out there. And that's where the game of compromise starts to creep in, tweaking your airplane away from your initial goals.

8. Aug 10, 2007

### Midniteoyl

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9. Aug 10, 2007

### buzzbauer1

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Bob and Thread author.... has anyone ever played with the notion of using airspeed as the primary source to retract the gear. I have often thought if some sort of catch was disengaged... at a certain airspeed... scoops on the sides of the gear would act like a parachute and pull the gear into up position. The same for going down. Pull a lever and a scoup pops down... and pulls the gear slowly down to lock position? Kind of a Kooky idea for sure... but ... then have an electrical backup. Seems like I saw something like this in a cartoon, a hundred years ago??? Probably where it should stay... but who knows? Just a thought. Buzz.

10. Aug 10, 2007

### orion

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The problem with using airspeed to retract gear is that even at cruise you're actually not developing much pressure or enough lift (say, on a wing shaped door) to actually fully stow the gear. Most LG hydraulic systems operate between 2,500 and 3,000 psi. With lets say a 1.5" bore hydraulic cylinder you have the capacity to generate well over 4,000 pounds of force - at about 200 kts you're generating a dynamic air pressure of only about one or two psi. Quite a difference.

BTW, the name is actually Bill (assuming you mean me of course)

11. Aug 10, 2007

### Falco Rob

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Would make for an interesting exercise when you try to do retraction tests with the aeroplane up on jacks.:gig:

Maybe jack it up on the back of a semi then blast down the freeway at 100 knots.

I once saw a video of one of our local characters launch his float plane off a trailer like that. Had his son towing it down the runway behind his F250 . . . . crazy guy.

The problem was he couldn't keep his mouth shut about it and the video found it's way to CASA (the Australian version of the FAA) who promptly busted him.

12. Aug 10, 2007

### Kestas

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13. Aug 10, 2007

### RonL

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Some time back, i made reference to the pelican, and the design of tri-cycle landing gear. My thoughts were along this line for the nose gear, the two main wheels( somewhere between bicycle, and motorcycle) would be faired inside fins, that extended above and below the wings, with just enough wheel exposed to land on.

The nose wheel would be faired, and after lift off, a lock release, would allow the gear to be turned 90 degrees, and the wind would push against the fairing and raise it to an almost retracted position, where (by hand) it can be raised the final amount, and locked in place.
To land, the gear is released, and turned 90 degrees, which results in less resistence, and then forced down and locked in place.

On a plane this small, and slow, the nose gear is not a very large mass to work with.

Just a couple of thoughts

RonL

14. Aug 11, 2007

### buzzbauer1

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Re: Sorry Bill, Yes I meant you.

Ok, that makes sense about the air pressure PSI's. However, my thinking is more on the lines of a spiral slot cut into the struts. And a ball and socket type thingie would twist with little air pressure and simply follow around the shaft until in pace... maybe assisted my some manual lever? at any rte I still like the idea of making lemon out of lemonaide... and to try to use the air is a rather interesting idea. I guess by your thinking the chutes or air traps would need to be the size of a small wing. Might not be the best looking thing flying, even if it would power the gear. Thanks for accommodating my out of box thinking. It is why I am no longer at Disney Marketing. Believe it or not.... I was too out of the Box for them... sad but true. Disney , only a chosen few are allowed think creatively... and only in a few departments... certainly not in marketing. Did I get off task here a little? ADA at its finest! Buzz.

15. Aug 13, 2007

### KC135DELTA

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Hello guys and thanks for all the replys.

The airfolding landing gear is an interesting idea, but sounds kinda risky for what I had in mind here. The bellanca seems quite a bit bigger than what I had in mind and it is probably beyond the safe abilities of most pilots looking to buy their first used airplane. On another note after looking around I think I found something that fits the bill or comes close to it.

The RV-10;

I want to use a commonly used engine so parts and and mechanics that are familier with the engine are cheap and abundent. The Rv-10 with 235hp (same engine as the C-182) cruises at 194mph @ 75% throttle. It will fly about 850 miles with this engine at this speed at this power setting. Seems like good performance considering it doesn't have retracts. Granted it won't pull off the 6 seats it still does seem to do pretty well. One of the things I would change is the seating arangement:

I think if we flipped the rear seats around (faceing the rear of the airplane) they would be able to get more headroom and legroom along with a wider cabin at the seat backs. Allthough the baggage compartment would have to be modified accordingly.

16. Aug 13, 2007

### orion

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The argument of rear facing seats has been used before (White Lightning for exmple) but from a marketing standpoint, no-one actually wanted it. There is just something uncomfortable about facing aft in a small airplane. But yes, the aft seat headroom in an RV-10 is a bit short.

17. Aug 13, 2007

### KC135DELTA

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Do you know anything else about the white lightning? Why did it fail? 280mph sure seems fast on 210hp.

18. Aug 13, 2007

### orion

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Don't know much at all - I've heard that the performance was great, although the main reason for that was that the airplane was rather small - sort of like a Mooney although a bit sleeker. The overall design and structure were reportedly excellent but I think any potential customers really did have a hard time getting over the somewhat tight internal volume and the aft facing rear seats. The most common comment I heard was that it should've been marketed as a two place, but of course for that the price was a bit high (although I don't remember what the kit price was to be).

19. Aug 14, 2007

### KC135DELTA

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What would the viability be to kinda "revive" that design? Maybe make it more normal are far as seating goes but at 280mph that would certainly make VLJ customers look twice. What kind of prop are we looking at for these speeds?

20. Aug 15, 2007

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