I wish new C-172s were a bit better.

[iflyforpie]

Sure:
Vso=36 KIAS - check
Large fowler flaps (45 degrees LND) - check
Absence of major AD's (not a single one on the airframe) - check
No known frame failures in flight - check
Simplicity -check
Utility - check

in addition - 5.5GPH for 140KTAS cruise; Vne=168KIAS; rate of climb over 1000fpm

The numbers were for the DA20.

In addition to your numbers being a bit embellished (it used to be only Piper owners who did that ), it can't do most of what I can do with a 172. We used to have a DA20 for a company hack. All we could do with it was parts runs because it had no payload, no space, and a low wing.

This is what I meant by utility. We take a group of two above average weight tourists up in ours and bring in $300/hr. Flight schools who have dead time can do that too under 406.... provided they have an aircraft people can fit in and see down out of. We use our 172 for wildlife telemetry (where the antennas mount to the wing struts), boat counts, aerial photography, finding lost cars/boats/cows, and I don't have to be picky about what tools and parts I put into it to go rescue an aircraft.

I can camp under the wing, I don't get wet when I get in, I don't bake in the sun when I am #10 for takeoff, I don't have to climb up over a wing to get into it.

Now, lots of this stuff doesn't have anything to do with composites I know. But it seems that the composite mindset is dead set on velocity and efficiency and pretty airplanes (though the DA20 is a stretch ). If somebody made a certified, four place, high wing composite aircraft, that had a generous wing area and good short field performance, I'm sure you'd have a winner.

Like I said before, DA20s and DA40s are just trainers and private aircraft. I'm not aware of any that do 702/703 ops and the extra they bring to training (speed, efficiency, gadgets) bring little extra student's learning process (even with the 172SP, it was too fast on my 150NM so I had to do another flight to top up my xcntry), and are unrepresentative of what a new CPL will be flying for their first job.

[akoch]

pretty airplanes (though the DA20 is a stretch )

Loved that one

I guess it is hard for a Cessna person to believe the numbers I used. Whether these are embellished or not, a simple POH check can confirm (and you can actually trust the numbers published in there).

Clearly we use different scoring systems regarding the aircraft use and utility. What you are saying sort of makes sense... in isolation. But makes no sense if you are thinking about a private aircraft. At least I used very different criteria when was on the market.

But you are right, the materials have nothing to do with that. It is just the fact that Cessna has not changed the 172 in so many years, and a lot of people still think of it as a viable aircraft. Until people change, the aircraft won't. Hence the original question of this thread... Whether we agree or not, it is the other companies that are innovating at the moment.

[Shiny Side Up]

Until people change, the aircraft won't. Hence the original question of this thread...

The aircraft won't change though, because the requirements that people have of it won't. I seriously doubt that someone is going to come up with a sudden new way of using these things. The only things I could see changing with the basic 172 layout is its powerplant, especially if they figure that electrical thing out.

One of the most common things I get asked about the airplanes is how draggy the strutted wing looks, which obviously deleting in a new design is a big selling point. The thing is though, that uncool looking strutted design is the best set up possible, for the size of airplane and the role it fulfills. deleting the strut means you have to do something else that penalizes the airplane in some way, In the Cherokees it meant having a big fat draggier wing - the same for the Cardinal for that matter. In the Diamond and the Cirrus designs it meant having to put a lot of steel into the wing to give it sufficient strength - if you get a chance take a tour of the Diamond factory one of the more reassuring things about the design is how heavy duty that main spar is, an I-beam of steel wrapped in fiberglass.

Clearly we use different scoring systems regarding the aircraft use and utility.

Again then, I'm not sure how your scale for utility works then. Either private owners or working users can make the same utility of the aircraft. Though I would disagree with Iflyforpie in that the materials don't make a difference. Try cutting new holes in a Diamond and a Cessna and figure out which is going to be the easier job.

Besides utility we also have operations costs and other logistical considerations. I'll tell you one thing, I know my fleet of old Cessnas is a lot cheaper to run compared to one of my competitor's fleet of Diamonds. If I had his maintenance bills I'd cry, though to be fair he's harder on his planes than we are. I can't see how that would be much different in private ownership. The aluminium fuselage will always be cheaper to maintain than a composite one. On that note, we should also talk about hangarage costs which also aren't cheap, but are more optional for the owner of a metal airplane. Something to think about, for typical hangarage costs, if you saved that money you could afford to repaint your airplane about every five years.

I hate to say it, but the basic Cessna configuration has evolved through almost as long as aviation has, and as an evolutionary design has ended up as it is though surviving and changing as it has been required. It shares the configuration with as equally long lived designs, and I don't forsee any newcommers changing what is just a plain useful airplane shape.

[costermonger]

Indeed, though as above the 172 has around a 150 to 200 lbs advantage on the DA40 and a way more tolerant CoG envelope. The advantage of an aluminium airframe.

Some of the long range DA40s w/ G1000 often have a sufficiently aft empty CoG that they're not just "pretend" 4-seaters in the normal sense, but instead they're truly impossible to put 4 adults in. The one we operate has the composite 3-blade prop on it, which weighs less but saves the weight where the aircraft needs it most, way out on the nose.

I really do like the airplane - it'd be my choice over the 172, provided they are both capable of doing the job. It's just more fun to fly.. But it just can't begin to compete with the 172 on utility terms, especially when you compare it to the 172RG. The RG is something like 5 pounds heavier, same engine (just no fuel injection) and is going to be ~15 knots slower than the DA40 at more or less the same fuel burn, but with full tanks it gives you an extra 100 pounds of payload and another hour in the air.

The RG even comes out favourably compared to the new 172. A typical S and an RG will both have an empty weight in the 1650-1700 range (those new seats are heavy!) but the RG is faster, has a greater fuel capacity and a higher gross weight. It probably won't be as pretty and it definitely won't be as quiet, but it will give you more options if you're trying to move people/things around.

[Shiny Side Up]

It probably won't be as pretty and it definitely won't be as quiet,

Actually one of my biggest peeves with the DA40 (besides the back breaking seats) was the ammount of noise it lets into the cabin since the air vents in a poorly planned set up pass through the engine compartment and firewall. Its very quiet when they're closed, but with as warm as it is under the bubble, I only ever did that in the absolute depth of winter. The new Cessna 182 with the scimitar bladed props was much better soundproofed, despite having a more monsterous fuel into noise processor up front.

[costermonger]

Actually one of my biggest peeves with the DA40 (besides the back breaking seats) was the ammount of noise it lets into the cabin since the air vents in a poorly planned set up pass through the engine compartment and firewall. Its very quiet when they're closed, but with as warm as it is under the bubble, I only ever did that in the absolute depth of winter. The new Cessna 182 with the scimitar bladed props was much better soundproofed, despite having a more monsterous fuel into noise processor up front.

That's true. When it's really cold, things are nice and quiet but it's also freezing as well, since the canopy is a few inches from your cheek and the cabin heat just doesn't seem to keep up.

I haven't flown a 182 with that prop on it, but a slightly quieter 182 is hard to argue with. I'm not usually the guy paying for the fuel, so I'd pretty much always prefer to fly behind a 540 than a 360. So much smoother.

[iflyforpie]

One of the most common things I get asked about the airplanes is how draggy the strutted wing looks, which obviously deleting in a new design is a big selling point. The thing is though, that uncool looking strutted design is the best set up possible, for the size of airplane and the role it fulfills. deleting the strut means you have to do something else that penalizes the airplane in some way, In the Cherokees it meant having a big fat draggier wing - the same for the Cardinal for that matter.

Ah yes..... the cool factor. I remember falling in lust with the Cherokee from the first time I saw it in Goldfinger (Pussy Galore wasn't too bad either). But going into fight training, Cessna it was. Dumpy looking generic slow strutted airplanes made the same year I was born. I simply couldn't believe that the Cherokee predated the Cessnas I was flying by 20 years.

The Cherokee was simply brilliant though. Yes, it had a fat wing (it was a 6 Series laminar flow wing.... exactly the same as the P-51... but draggier at the speeds flown--especially the constant chord short wings of the earlier versions).

But by having one spar at 50% chord, they kept the floor flat and made it the front support for the rear seats. No subfloor like the 172, just some chines off a boat hull for ridigity and a tunnel for control cables. The gear could be made shorter and provide more stability. The fuel tanks were 'wet' and simply added to the wing skin in front of the spar. With these features, the Cherokee was light enough to compensate for the heavier wing, fittings, and center section (empty weights were the same or less than a 172 of the same era).

The Cardinal (another plane that I love the looks of) had none of those advantages. It still had the sub floor, and the wide and heavy spring steel gear (of which the unstreamlined tubular version was very draggy). So it was slower, which made the fat laminar flow wing even worse. Sleeker looking but slower than the 172 by a few knots. Terrible center of gravity range because of the very forward position of the pilots seat and loss of authority in the stabilator in the flare--most original 177s have at least one firewall repair in the logbook.

But back to the cool factor. Cool planes often aren't profitable ones. I've seen so many aviation businesses fail because they chose the airplane first, then tried to find work for it.

I am probably doomed to fly strutted Cessnas for the rest of my life (even the 337 has them! ) but if it means I can make a decent living doing so, I'll leave the fancy sleek airplanes to those who can afford them....

Though I would disagree with Iflyforpie in that the materials don't make a difference. Try cutting new holes in a Diamond and a Cessna and figure out which is going to be the easier job.

Well, neither is going to be easy without the proper tools, training, and approvals.

The only real difference is the hard times required for curing on the plastic airplane. Cutting is roughly equal. Doubler layout about the same. Etch, alodine, prime, riveting, and paint wouldn't be much different than wet layup or prepreg, vacuum bagging, curing, sanding and painting.

Of course, I know which one I'd rather do.

[Colonel Sanders]

I had to laugh when I read this:

http://life.nationalpost.com/2012/09/13 ... o-swallow/

Land Rover recently lopped a whopping 318 kilograms from its flagship Range Rover, but it required a wholesale change in the SUV’s unibody frame to aluminum, an advancement not currently feasible for any but the most expensive luxury automobiles.

That "advancement" was available on all Cessnas by 1950
and is currently poo-poo'ed here as "old technology", not
an "advancement for the most expensive luxury automobiles"

[iflyforpie]

I had to laugh when I read this:

http://life.nationalpost.com/2012/09/13 ... o-swallow/

Land Rover recently lopped a whopping 318 kilograms from its flagship Range Rover, but it required a wholesale change in the SUV’s unibody frame to aluminum, an advancement not currently feasible for any but the most expensive luxury automobiles.

That "advancement" was available on all Cessnas by 1955
and is currently poo-poo'ed here as "old technology", not
an "advancement for the most expensive luxury automobiles"

That's marketing for you CS.

I remember when I was in an Acura dealership looking at an Integra, they had an aluminum NSX on the floor. The salesman boldly said that it was corrosion proof because it was made from aluminum. I asked if it was better than aircraft aluminum, because I was working for Kelowna Flightcraft at the time and was deriving most of my income fixing rotten airplanes.

[Geo]

But it seems that the composite mindset is dead set on velocity and efficiency and pretty airplanes (though the DA20 is a stretch ).

Hey! The Katana is WAY prettier than a 172. AND it has a stick. :p

g

[akoch]

In the Diamond and the Cirrus designs it meant having to put a lot of steel into the wing to give it sufficient strength - if you get a chance take a tour of the Diamond factory one of the more reassuring things about the design is how heavy duty that main spar is, an I-beam of steel wrapped in fiberglass.

Shiny.... there is no steel in the DA20 or DA40. The DA20 has fiber glass and kevlar spar, the DA40 is carbon fiber and kevlar. Not steel i-beam or anything like that. The only metal mesh (also not steel, but lightweight alloy) is the lighting protection embedded into the DA40 fuselage. It is not structural, just for the conduction to satisfy the IFR requiremetns. The spars are strong as it is. Well over 12G load capacity... each.

[cgzro]

I always wonder about the life expectancy of composite v.s. aluminum. I mean Aluminum planes can be left outside and while they do corrode, its slow and damage can be fixed by drilling out the panal in question and riveting in a new one. So most Cessna's likely can be operated more or less indefinitely if they are properly maintained. We have plenty of examples of metal/wood/fabric lasting a very long time, albeit with components being replaced as they age, but thats not such an easy option with composite so perhaps the lifetime of the airframe needs to be factored in, but there is no doubt the flight performance of composite is superior... often vastly so.

[akoch]

Well, ask the glider guys. Many of their planes approach 50-years in service. Or refer to this document for more technical review of the matter:
http://depts.washington.edu/amtas/event ... .Salah.pdf

[cgzro]

Thanks for posting that link, very interesting reading.

[Shiny Side Up]

In the Diamond and the Cirrus designs it meant having to put a lot of steel into the wing to give it sufficient strength - if you get a chance take a tour of the Diamond factory one of the more reassuring things about the design is how heavy duty that main spar is, an I-beam of steel wrapped in fiberglass.

Shiny.... there is no steel in the DA20 or DA40. The DA20 has fiber glass and kevlar spar, the DA40 is carbon fiber and kevlar. Not steel i-beam or anything like that. The only metal mesh (also not steel, but lightweight alloy) is the lighting protection embedded into the DA40 fuselage. It is not structural, just for the conduction to satisfy the IFR requiremetns. The spars are strong as it is. Well over 12G load capacity... each.

You're right the DA20 doesn't have any but the main spar of the DA40 does. I've seen them being made man. There's two 1" by 1/4" strips of steel which form the caps on the "I" cross section of the DA40's main spar. That's a pretty hefty chunk of metal. Those two strips are then bound into the I shape of the spar and wrapped in fiber glass . That ammount of metal was both what was required for the electrical conductance requirements for IFR and to add strength to the wing for the extra weight of the 4 seat model. Incidentally, those "light weight alloys" are also mostly steel, no matter what fancy name the sales people come up for them. I think the one that's all the rage these days is Chromoly, but its still mostly carbonated iron in there.

[akoch]

Admittedly I have not seen the spars made. Not that I am looking to contradict you, I just never heard of the steel part. Diamond always maintained those are carbon fiber spars. From the website:

...aluminum fuel cells protected by the DA40's dual carbon fibre spars help prevent post impact fires, a 26G rated safety cell cockpit, airbag seatbelts...

The maintenance manual and parts manual also show them as:

"The cantilever wing is a semi-monocoque structure. Each wing has two I-shaped spars with webs made form GFRP/rigid foam sandwich and caps made from CFRP bands. Each wing has top and bottom shells made of CFRP/GFRP/rigid foam sandwich which bond to the spars. GFRP ribs and webs bond to the spars and shells to complete the structure."

"Each wing has two I-section spars. The front spar on one side is the same as the rear spar on the opposite side. Many layers of uni-directional carbon fiber make the spar caps. The number of layers in the spar caps decreases from root to tip. Each spar has a shear web. The shear web has GFRP skins and a rigid foam core. Glass cloth fillets attach the spar caps to the shear web."

The maintenance manual can be found here: http://www.diamond-air.at/fileadmin/upl ... mplete.pdf

Now, would not it be a good thing for 172 if it had dual carbon spars, protecting the fuel tanks so that there is no post-impact fires happen, spars not requiring inspection and not subject to fatigue? And at least twice as strong each. This can be done today, with no weight penalty and basic re-engineering. Except the company needs to spend money and invest in it, as well as into the recertification. Why bother is probably the answer.

[Beefitarian]

Now, would not it be a good thing for 172 if it had dual carbon spars, protecting the fuel tanks so that there is no post-impact fires happen, spars not requiring inspection and not subject to fatigue?

If that's true it sure would be. If it's opinion...

[Shiny Side Up]

There's steel in those things, I know its tough to take and its not something they advertise since that would make them sound somewhat unfuturistic. Remember what we said about marketing? If it makes you feel better though the ol' 172 has steel in it as well, there's a big square tubing chunk in each of those ol' struts.

As per carbon fiber spars on 172s well there just is no real point, especially given the design, unless you want to just raise the production costs. Do the aluminum spars not do a good enough job of protecting the fuel tanks already? I don't see a lot of Cessnas burning up on impact.

[akoch]

You misunderstood me. It does not matter to me if there is steel or isn't in the spars. I'm more of the engineering type than marketing. Who would complain if there was steel making it stronger. It is just that I am not aware of such thing, can't find any supporting material on such statement (can't rate the official service and parts manual as "marketing"). Doing a steel spar inside a carbon spar... does not seem to make sense to me. I could understand aluminum, magnesium, dural etc etc. It is just the steel i-beam that makes me wonder Plus the fact that the carbon/glass fiber sandwich is as strong, actually stronger than steel. And the spars on the DA40 or 20 do not require any additional reinforcement as far as I can tell...

[Beefitarian]

I know a way we can settle this. link

[Shiny Side Up]

Doing a steel spar inside a carbon spar... does not seem to make sense to me.

That's because its not a steel spar inside a carbon spar, from before:

There's two 1" by 1/4" strips of steel which form the caps on the "I" cross section of the DA40's main spar.

To be specific, there's a foamed core which are capped top and bottom by the steel strips. The whole thing is wrapped in carbon fibre to form an I beam, and then wrapped again in fiberglass. Its pretty neat to see it made. The steel essentially gives it ridgidity while its being made to form the initial shape, but does dual purpose of forming part of the electrical conductance of the airframe.

[akoch]

Perhaps it is taking the "composite" to a new extreme adding steel to the mix. Or indeed it is done to channel the current from the metal mesh in case of a lighting strike. Beef is already looking for a saw to settle this

[xysn]

What stood out to me was not the value increase but the technology improvements.

I wondered again. If cars have improved so much? And they have. Seriously, compare a 1974-1984 of the same model car. They are vastly different, though they have come up in price there is way better value.

Why not the C-172? It has fuel injection also but most people don't feel it has improved significantly. I like the new ones but I don't think they are nearly improved enough. Certainly not to the point of being comparable in advancement to highway vehicles.

GA aircraft don't have the same competitive pressures. Basically everyone in North America needs access to a car, and needs to drive. When driving gets expensive, it's a political issue because people generally need to drive no matter how expensive it is. When flying gets expensive, people just stop flying.

The oil crisis, small fuel efficient competitors, and the government - through fuel economy standards and crash test standards - motivated a lot of improvements in fuel economy and safety.

A Katana uses 17 litres per hour making 60 hp. If you drive a Civic for an hour at 100 km/h you'd burn maybe 6 litres and if I remember correctly it takes about 70 hp to keep a Civic going at 100 km/h.

That doesn't mean good auto engines are good aircraft engines but there must be some room for improvement.

[akoch]

Say Eclipse/Katana burn about 17-21 liters per hour going 250km/h. A Civic does 100km/h and burns 7liter/h or so. Pretty much same figure. Consider that an aircraft goes more direct as well.

In car numbers the Eclipse/Katana are in 28MPG territory, which is Civic ballpark.

[Colonel Sanders]

That doesn't mean good auto engines are good aircraft engines

Finally, after decades of nonsense, someone admits it.

there must be some room for improvement

Are you proposing that there is some Grand Conspiracy (tm)
stopping people from implementing these improvements?

Sure, blame paperwork for certified aircraft, but what's holding
the homebuilders back?

They all fly Lycomings. Only tweak they've made is to replace one
magneto with electronic ignition, for better starting. Despite all
the decades of hype, no one runs FADEC. And that's it.

To all the auto engine fans out there: Why aren't you running
a Porsche PFM engine? Superior German engineering - or not.
Despite blowing a billion bucks, they couldn't out-perform a
Lycoming, which all the experts claim is "old technology". Well,
maybe it is, but it's also better technology.

How many auto engine conversions are there at your airport?
How many have you personally flown as PIC?