A couple of fellow Aeronautical Engineers/Back country pilots and I have been discussing the design of a modern back-country/bush plane in the 3400-3600 gross weight range. Market research is in preliminary phase, and the design Details that have been decided upon are:

-Conventional Configuration (main wing defining CG range, i.e. no canard, tractor engine, and conventional empennage for pitch and yaw stability and control)
-Heavy 4, or light 5-6 seat configurations
-Composite Construction (primarily Carbon Fiber,some glass)
-high wing (lots of flap, perhaps slats, possible boundary layer control devices for use at low speeds, and no lift struts)
-Continental IO-550 powered with a heavy fuel burning variant to come when a decent diesel recip hits the market
-very durable conventional landing gear (considering a trailing-link design like the Wilga, but that may prove too complicated and heavy)
-Payload roughly equal to the empty weight
-206 style doors
-Primary design objective is rough/short field operations
-oversize tire, float, and ski installations will be considered from preliminary through final design phases
-Weight and Aerodynamic Drag will be minimized as primary and secondary design considerations (this seems obvious, but this machine is not intended for plush leather interior, de-icing equipment or dual Garmin 530s, and a plane with good low speed characteristics doesn't need to surrender to the drag accompanying strut bracing everywhere, exposed hardware, Hershey Bar Planforms and row after row of protruding rivet heads. No offense intended, I fly all of the parasitic, induced and interference drag sources mentioned here with great pleasure, It's just that it's now easier to eliminate the aforementioned and realize gains by doing so)

We are seeking feedback from the Back Country/Bush Flying community in regards to desirable features and characteristics for such plane? Any input is appreciated.

How about a Wilga with Cessna wings and your flat engine?

If you are going after the bush operators market make seat 5 and 6 for full size humans, 'cause that is what we are putting in the back of the 206. The seats need to be easily removable, and be able to be stored easily on board (so that if you are taking supplies in, you can take folks out). Also, make the seat rails recessed into the floor, so that boxes, dog food, whatever can be slid into position in the cabin, on the 206 we have to lift and place stuff over the seat rails. Lots and lots of rings (also recessed) for tying down stuff in the cabin. Seats rated for 350 lbs or more (that body weight is not unusual for the villages we serve). A huge CG envelope. Initial design should include an optional cargo pod, that doesn't hinder access for maintenance or inspection (eg the fuel drains for the kidney tanks on the 206 are accessed through the pod). Don't worry about comfort too much, most of the runs are 1 hour or less. But a bitchin' (yes I did use that term) heater. Big windows for the flightseeing market. Lots of cargo cubic space, we carry a lot of fluff like potato chips in boxes for the stores: light but a lot of cubes. You might want to take a look at the airvan, it is trying to compete with the 206 and has a lot of great features, but the price seems to be limiting its success. If you are really serious about this project you need to come up to Alaska spend time around the state looking at 206/7 operators to see how much abuse and use these planes take.

Can you take the basic Found idea and improve the wing and load capabilities? I like the airplane (a bit anemic on amphibs), it's a very strong airframe and the gear is as STOUT as you could ever want. It behaves very nicely STOL on wheels and is super simple to load up and operate. IO-540 and IO-580 current engines. If you could play with the wing and make it quicker and better on floats, use carbon fiber here and there. it'd be a nice unit.

( I would like a 12 volt system for operations away from facilities. Found is a 28... ggrrrrr)

FYI, Aviat looked closely at this very concept. In fact, they got to the point that the airplane was designed and at least partially constructed. They abandoned the project due to lack of market.

Check out the aforementioned Found airplane. They've been in production now for at least 7 or 8 years, and they aren't selling well at all. There are lots of reasons for that, but one of the big ones is that there really isn't much of a market for this type airplane.

Tailwheel airplanes are a huge liability risk as well.

And, frankly, as Outdaplane noted, the Cessna 206/207 and Cherokee 6 is still soldiering along in the boonies. Those operators aren't going to buy $500 Thousand airplanes, cause they just can't amortize the cost fast enough. So, until there's enough of these sold as toys, amortized and devalued, the commercial operators aren't going to use many.

Take a good look at the market--I just don't see what the market could be for a half million dollar airplane. And, I seriously doubt you could produce what you're describing for much less.

The Airvan is an interesting airplane, but again, it's expensive, and you can't make that many seats generate enough revenue to pay for the cost of a new airplane.

One day, the 206/207 and PA-32 will all be wore out, and maybe then there'll be a market for something like this. But remember, Cessna is still producing new 206.

MTV

mtv wrote:...Tailwheel airplanes are a huge liability risk as well...
MTV

Surely you meant "...are DEEMED a huge liability risk..."

Look at the Pilatus Porter, shrink it to fit whatever your size will be, and make it out of composite. The graphite rod spar material is actually cost competitive with metal because you use less of it to achieve the same strength. Now before anyone gets their shorts twisted... I am NOT an experienced bushplane driver, I have NOT worked in 100 below blizzards bringing sled dogs to remote villages, etc. etc.

But I do have more time in composite airplanes than some of the regulars here.

If you can keep an open mind, the main parameters that you might want to look at are -

1) A cantilever wing made with carbon rod spars is lighter, stronger and more efficient. Carbon longerons in the fuselage are stronger too. If Boeing finally admitted it, and assuming the 787 is as good as the numbers say it is, then all the bushwhackers here can admit it too. Carbon is stronger than aluminum. No you can't repair it with tin cans and pop rivets in the field. Carbon fiber rods are strong enough to allow the structure to handle really big flaps with offset Fowler hinges, which will give you good STOL performance.

2) There are airfoils that reduce drag without going overboard and losing all their performance when dirty. deHavilland and Pilatus and Dornier have figured that out for utility airplanes.

3) As crazy as it sounds, a one-piece wing is worth looking at. You save a lot of weight, COST, complexity, fittings, and get a stronger wing. Using a cantilever, one-piece wing allows an interesting storage and shipping option. You can remove four structural bolts, the fuel and control attachments, and rotate the wing 90 degrees. It can be put on a rail car, perhaps a shipping container, or stored in a narrow space. Believe it or not there is an ultralight airplane that uses this method. I believe these benefits are big enough to justify having to helicopter the airplane out if it is severely damaged.

4) If you design it correctly, a square cross section fuselage can have reasonably low drag. Look at the reduced drag of the Taylorcraft fuselage versus the Cub and Champ. Today's CFD and airflow predictive software can make this pretty simple. Your benefit is saving a bunch of time making tooling... you are able to make four single-plane composite sides for a fuselage instead of having to make a $million full size mold. For a bushplane, you can substitute some cleverness and save a fortune. If you want a sailplane with 50-1 glide ratio you need round molds. For a slab sided bushplane you can lay up all four sides on a flat or single curve table.

5) The carbon rods make for a VERY strong and flexible landing gear. One piece, no moving parts, no corrosion, lighter than steel or aluminum, and able to withstand large impacts. That means cheaper too. Main gear and tail gear legs can benefit from this greatly.

6) There is a lot of worthwhile performance to be gained in composite wingtips. Not the big droop tips either... Look at the recent Dornier seaplanes and their small airliners. Look at the latest Lancair sportplane. Look at Dean Wilson's last bushplane design, the "Ellipse".The swept tips make a measurable difference in slow speed ability. They create a pressure distribution which fight against, and lessen the wingtip vortices, which means more effective wingspan out of the same length wing. Look up the history of the Discus sailplane, and the wing planform developed by Wil Scheumann 25+ years ago.

7) Leave room for a BUNCH of different engines. The $5,000 "crate" Chevy aluminum V8 is being looked at by a LOT of smart airplane designers. 300-400 reliable horsepower, good fuel economy, enormous torque, excellent modern injection and ignition system, runs on cheaper car gas, very cheap to buy and very cheap to buy parts. Yes this would be experimental in the beginning, but experimentals are being sold now more than certified airplanes. I'm not telling you to start off with the V8... start with an airplane engine that exists now. But leave room in your firewall and engine mounting design for anything and everything that may come down the pike.

8 Put hard points in the wing. For civilian uses, this will make it a lot easier for people to sling external loads like canoes, bikes, whatever. Extra fuel tanks as an option are probably very worthwhile, sort of like a drop tank that doesn't drop. People operating sensors, cameras, etc. can also possibly make use of this. Obviously the hard points allow you to explore military uses later too.

I know in the yukon there is a need for somthing in between a 206 and a carivan, the airvan is interisting but with the same engine as the 206 how mugh more will it really haule? I think it needs to be basically a mini kodiac with somwere in the 20gph range for fuel burn ,160mph or so cruse, IFR and decent stol capibility. we too have discused this at allot and the biggest problem I see is you need a readily available engine that is bigger then the 550 and more dependable then the 985 and cheeper to run (and buy) then the pt6. if you can find such an engine expecially one that will run on jet fuel (third world countries its hard to get avgas and mission outfits will be your biggest market) then you might be on to somthing. but Im afriad with a 550 you are out of luck for all the reasons listed above.

Wing struts in the bush are a good thing. Got stuck in the sand in a 210 once and it was a b&*^% to get unstuck! Definitely need somewhere to push.

not to mention the wings falling off things like helios! triangles are strong!!!

Thanks for the feedback. Many considerations that had not occurred to me have been presented here. I agree with MTV that the airplane that I'm describing would need to sell for at least half a million, as it would need to be certified for production and Part 135 operations. This expense would be difficult for most commercial operators to amortize like they could a $150000 206. But Cessna is selling new 206s for half million. Developing, certifying, producing, and marketing such an airplane may be a pipe dream, but it's fun to discuss and think about.

If said aircraft has many of the high profile annoyances of the current fleet eliminated, can haul more, go faster, and operate out of shorter rougher strips, it may be viable. The market, it seems to me holds a gap for a 4500-5000 lb gross weight six+ seat bush plane that can be loaded up through large doors with easily modified seating configurations and clean accessible floors upon which supplies could be easily positioned and safely tied down. The lack of availability of engine options above 300 hp and below a PT-6, with proven reliability and guaranteed support in to the future poses the real conundrum. If there was a certified turbo-normalized diesel of reasonable weight in the 350-450 hp range, we would begin work on this plane today. Old Beavers fetch as much as 550k on the used market. I would think that some might be interested in spending 600-700k on a capable modern alternative over a 12000 hour Beaver from the fifties. Unfortunately, the automotive V-8 engines are not an option, because this plane would be certified. Only out of curiosity, does anybody know if one could one design an airframe around a R-985 and count on support in to the future?

Having tested, flown and designed extensively with composites, I am absolutely a believer in the superiority of Carbon fiber for wing and tail structures to all other available materials. You can build any shape that you want with perfectly smooth surfaces, achieve outstanding strength to weight ratios, tailor your stiffnesses specifically to your loads, have a practically infinite fatigue life, sustain tremendous damage without compromising airworthiness, have zero issues with corrosion, and repair nearly any damage temporarily or properly with no compromise to structure or contour.

Perhaps I am conceptualizing my dream plane vs. what the market desires here. This is why it's a rugged tailwheel design. If the market clearly preferred a trike, I'd probably go in that direction. I am very reluctant to roll over and compromise my designs for the "I don't respect the potential hazards of a product, therefore it's the manufacturer's fault that I screwed up because my lawyer said so" mentality. Designs are to Part 23 Certification standards, which are unbelievably conservative and are the benchmark for the world's GA machines. Many fine craft with conventional gear have endured more than half of a century without the FAA deeming them unsafe.

Have you looked at the Murphy Moose w/ the 360hp M14P. I know it's not all composite but it meets alot of your requirements. (has lift struts though)

I know that the idea is a clean paper design of the optimum bush plane. How about a new wing design using composites on a Cessna U206. I am currently working on the engine change STC for the 206. Waited for the Theilert 350hp diesel. Couldnt wait any longer. Now to tear down my composite wing idea. Unless you go for the latest light weight techniques and materials the aluminum wing would be heavyier. The lightest composites arent really bush friendly. I can stand on the wings I built for my Long Eze. Over designed and the same weight as an aluminum wing. Burt called them spectator proof.

Mabe you need to revive the IO-720

Problem with the R-985 P & W engine is that it hasn't been in production in something like 60 years. I think the 985 was out of production when the Beaver went INTO production. There were tens of thousands of new, in the box 985s available, though.

The engine is the issue for the airplane of the size you're talking about.

As to Cessna still building 206's, so the price point must be okay--look and see who's buying those new 206s. It's not commercial operators, it's wealthy individuals. The commercial operators AREN'T buying new 206s at least for the most part. You simply can't pay that much money and amortize it with the numbers of seats the plane offers. For that reason (the type buyer), the newer 206's look like luxury automobiles, and useful load just plain sucks, unless you want to strip that very expensive interior out and start over.

The demand for new airplanes isn't from commercial operators--it's from individuals. THose folks keep the airplane and depreciate it, and the commercial operators buy them for cut rate prices. That's how things work these days. And rich folk ain't going to buy a stripped out bush airplane.

Even the turbine Beaver can't make it commercially in most cases. It's not big enough, and too expensive. It takes an Otter/Caravan sized airplane to turn enough profit to make this much investment work.

And, by the way, if you're now talking about an airplane LARGER than a 206, that $500 K price point isn't going to get you there either. I'd guess for an airplane that size, you'd be looking $750 K square in the eye, before options.

MTV

What about the 720 Lycoming? They're around 400 horsepower.

I don't think that the IO-720 has a very good reputation. It was installed in a Commanche and several Aero-Commanders, but the crank shaft is too long and not dynamically balanced so sweetly like a good six cylinder engine. Sherpa installed that engine in one of their planes as well.

I'm hoping that a good 350-450hp Turbo-Diesel is developed for GA applications. Such an engine could serve a whole new crop of high-performance airplanes that could cater to emerging markets where 100LL is not so readily available.

Engine wise have you looked at the Allison C-20 as used in Jet rangers and Hughs 500s? 420 hp and burns around 22-25 gph. Just a thought.
Jim

The problem with aircraft diesels (to date, at least) is they tend to be heavy. We'll see if the future brings lighter, more powerful diesels.

Soloy conversions has produced a fixed wing version of the Allison C 20 with a gearbox for years. Problem there is $$$$. As in BIG $$$$, like any other turbine.

MTV

It was installed in a Commanche and several Aero-Commanders, but the crank shaft is too long and not dynamically balanced so sweetly like a good six cylinder engine. Sherpa installed that engine in one of their planes as well.

Also, some of the Piper Brave spray planes used that engine. I always thought they sounded pretty nice idling when taking on another load of chemical.