Not to mention, that jerrycan refilling is a bit of a mess, and potential safety hazard. A lot of airfields even prohibit jerrycan refuelling on the ramp.

I agree. Unless mogas becomes directly available on the airfields, mogas isn't really a viable option. I see mogas as a great "fallback option", ie. if you're stuck somewhere w/no avgas options for hundreds of miles.

So is diesel btw. (good for the SMA's/Thielert-Centurion and probably the Austro as well)

What would actually happen if you put normal car petrol into the tank, for an IO-540-C4 for example?

Presumably, detonation would not occur at the low CHTs present during takeoff, IF you transitioned to a cruise climb ASAP.

Any old twin worth it's salt is going to guzzle 25-30gph Avgas. Add to that a minimum cost of $25-30k per engine on overhaul, plus all the rest of the stuff you get stung with on old twins. I've shelled out $35K this year alone in maintenance (bless her heart). Even a financed Tecnam at 5% interest is going to be more cost effective at just 100-150hrs. Everything above that is gravy.

On a LA to NY trip of 2100nm, the Tecnam will burn $825 in Avgas, or $525 (this is airline competitive prices) in Mogas. Compared to my Commander at $2062 in Avgas. Same speed, same power setting. It doesn't take many hours before you've saved enough to pay for that monthly payment...

And come overhaul, you're looking at half the price or less compared to any Lycosaurus

Should not be as much. I am below 10GPH on high altitude flights, so 2x that. 30GPH is just being ignorant of engine management, or flying a turbo installation at 75% to 85% of max power.

But cost savings are not much good if you are stuck in icing conditions.

That's a good question. An acquaintance of mine flies mogas in his IO360 DA40F. (covered by a mogas STC) But I'd personally be wary of doing this on a IO540.
I'm not sure why, but I generally hear even higher consumption figures quoted for these old twin guzzlers. A friend of mine flies a C340, and it's running ~35gph at 75%. Try that with non-US avgas prices, and you're talking serious cash for even trivial trips. Although as people have mentioned in this thread, what's really killing the old twins are the damn maintenance bills.

Adam, please tell us it's been worth it after all! :ok:

I suspect it is because the ones you heard about are flown by pilots who are ignorant of modern operating procedures.

The engine doesn't care if it is in a single or a twin.

But yes an old twin will be relatively expensive to run because

- you have 2 engines and some ~80% of the 2nd engine is used to pull along that engine, plus the now substantially larger aircraft (longer wings are needed because the engines take up a fair bit of them, for example)

- most twins are very old and an old plane will tend to have a significant appetite for airframe parts (true for old singles too of course but a twin has more bits on it)

Yup everybody is ignorant about the operation of engines except you :rolleyes:

Adam flies an Aero Commander 520. It has GSO 435 Lycoming engines fitted with pressure carburators. His reported fuel flows are the best you are going to get from this engine. All the modern engine analysers in the world are not going to make any difference as this engine won't run smoothly at LOP.

In any case all the private pilots I know who operate twins are quite aware of how to run the engines economically because they are the ones who have to pay the big bucks when the fuel truck pulls up! They all have and use engine analyzers.

I don't think you got what I was getting at, BPF :ugh:

Yes it has for sure for me personally, but it's like people say: if you buy an aircraft cheaper, be prepared to spend as much again the first year to bring them "back". This has proven to be the case. Even though I knew that, it's only when you're actually faced with the bill that it hits home. But no regrets at all, even though this is money you can't get back if you sell it.

My squawks are pretty much all eliminated and ironed out now, so this year the costs will only be cosmetic, hopefully. But just to give an idea: a new paint job done right is $18K, an interior is $5-10K. Any new avionics installation is in the thousands etc. So it's not for the faint of heart.

With how many stops? 4 minimum, with all seats full 7? Obviously flying in the US is more reasonable but 7 stops in Europe starts to stack up. Especially if one has to utilise proper airports, which on a long international flight one would have to to be assured of completing the mission. Providing icing isn't an issue. Also the 2100 nm will take a looooong time.
The right avgas burner should be around 20-24 gph. Anymore than that would be discounted in my search for cost reasons.

If I wanted a twin (well I do...but...), I'd buy something like an old Seneca II (as it has turbos on and is pretty capable if you get de-ice boots etc...) relatively cheaply. I'd then overhaul the motors, put 3 blade props on, re-upholster and paint. Then depending on how flush I felt, I'd fit a new avionics suite.

So for £150,000 you could end up with a sweet "as new" aeroplane with modern avionics in great known condition.

Yep it will burn significantly more than a DA42 but at the end of the day if one buys a new aeroplane, you're going to lose a shed load of money in the first few years anyway, and that is more then equivalent to the fuel saving.

That is what I was getting at. I cannot see a problem (apart from it being illegal).

Don't forget the 1999kg STC, Englishal ;)

I don't know your definition of a REAL airport, nor why anyone should want one. But there's plenty of aerodromes with mogas available, especially round yours. Check it out at http://www.dulv.de/app/so.asp?o=/_ob...gas_170111.pdf for just one source. Have to admit I know of no airfield with a Mogas pump in my own country.

Oooo, though I'm generally a fan of some "legacy" types, NOT a Seneca II, or a number of other Pipers of that era. I have had first hand experience with very expensive repairs required for corrosion damage, because Piper would not support that type, with the required replacement parts. I quote the Piper Tech Rep: "Sir, that's a 40 year old airplane, we have not seen it in 40 years, and we don't want it in the air."

With that policy toward product support, I'm really happy I own the second most common Cessna ever!

Neither of those reasons are true.
Two smaller engines mounted on the wings are less efficient in weight, drag and specific fuel consumption than one larger one, no doubt. But it's nothing like 80% of the 2nd engine. That's ridiculous. Take a basic airframe available in twin and single versions. A 2x200hp Seneca vs 300hp Saratoga. The Seneca is faster. It is not substantially larger, it is about the same size. For that matter look at the Tecnam 2x100hp vs. 160-200hp singles.

I have never understood your theory that an old plane is expensive to maintain because of airframe parts. I have owned 2 old twins and the airframe parts cost has been negligible. I don't believe a properly maintained old twin cost more to maintain today than it did 20 years ago. However, they do cost a lot to maintain because they are complex and labour-intensive. There's more to go wrong and even trivial things can take a few hours labour before anything has happened. What is hugely expensive is taking a badly maintained old twin and fixing it. The other mistake is to base maintenance cost expectations on what the purchase price of the airplane is. The old twins have depreciated a lot in real terms but that hasn't changed the maintenance cost from the time in the 70s when they were the equivalent of $1-2m corporate airplanes.

There are thousands of Senecas flying about giving dependable service. In my 10 years of ownership I never had a part problem. And at least Piper didn't succumb to an equivalent of the SID debacle which has cost twin Cessna owners $100k each in some cases - ask any Australian C310 owner...

I have yet to hear of any consistent set of anecodotes about parts cost and availability for any old aircraft. They always contradict themselves. One person says
"the factory was struck by a giant meteorite in 1971 and vaporised. The company then went bust and all the drawings were burned. Parts sourcing is thus a nightmare for this Type"
Then someone replies
"Nonsense. The owners' association has a list of PMA suppliers and every single part can be sourced just as quickly and cost-effectively as for a type still in production"

I agree that different owner's experiences with airframe parts availability can vary greatly.

I was not involved in either of the two mentioned parts availability problems as the owner, but as the DAR (like FAA DER) asked to provide approval for a "made part", when Piper would not support the aircraft with the required parts. The quote I reference was spoken by Piper to me.

The Seneca II I was involved with was unairworthy as a result of corrosion - just certain parts, but critical ones! If there were any alternative sources for the required parts, a great effort expended, before I got the call, would probably have revealed it/them.

Similar challenges with Cherokees, and in particular an Arrow I was asked to inspect, have resulted in a similar response from Piper.

Yes, Cessna has mandated comprehensive inspections, which, in the era of "aging aircraft" for larger types, does have some merit. I believe that Cessna will still provide the required parts. (though I have not personally checked this). I attended a Cessna presentation on this subject, and nothing in that presentation lead me to think that Cessna did not want it's legacy twins flying, they were just intent on assuring their airworthiness. I understand it's beginning to filter down to the singles soon too.

I did check with Piper myself, and was twice told "No". That makes an impression upon me....

My vote goes for the Twin Com; great aircraft.:ok:

Obviously that's not true, so it could not have been a theory of mine.

It is the accumulated cost of poor maintenance (specifically poor lubrication, and corrosion) which makes an old plane potentially much more expensive to bring up to a "perfect" standard after it is bought by the next punter.

There are obviously exceptions, depending on whether the previous owner was diligent or not, but most owners do not maintain on a money no object basis. Most let things wear out and then they flog the plane. Same with cars.

But firstly few people are going to "totally fix" a 30 year old plane they have just bought, so they will be running along with a part of the legacy they bought, and secondly corrosion is something that does get increasingly expensive with airframe age (relative to hangarage history obviously, etc). That is just actual practice out there.

After the total-stripdown rebuild you had done on your 421C (ballpark cost £100k plus avionics?) I would have expected it to be close to zero for the rest of your flying life :)

Re the 80% fuel burn overhead, what figure would you offer?

The Twin Com is the aircraft that will do the job for you in the most efficient way. Fuel consuption will be 15gl total @ 160 knots (indicated at low level). In Oz there are some very knowledgeable people who will be able to you if you have problems, more over, they even produce their own parts (due to CASA rules). As for parts, some are more difficult to obtain than other but all are available, especially as Piper said that they will start to produce parts as needed, even if they have to reverse engineer them, price unknown.
If you decide to go for the twin Com feel free to contact me (by email) and I will introduce you to some people that will make sure that you won't get burnt, they can find the aircraft for you, will inspect and repair it as needed if you instruct.

Pilot DAR
These 3 bladed props, are they FAA STCed or just during development? How much are they? Some people will give their right arm to have these on their aircarft.

Thanks

If you are a really good engineer (like you are) and you live in a reasonably dry climate then there is no reason why 50 year old airframes should not be fine.

Being in the USA also helps. One of the things which costs money in Europe is that there is no authorised procedure for replacing bushes which are push-fit inserted into aluminium brackets. You have to either buy the whole bracket with the bush (typ. £1000) or you do a job off the books whereby you either (a) ream out the bush a bit and machine up a new pin or (b) push the bush out and machine up a new one and just buy the usually cheap bolt which goes into the middle of it. Some 99% of airframe parts are trivial to fabricate if you have a lathe and possibly a turret mill, but cost a fortune to replace officially. Under the right regulatory regime you just machine them up and an A&P/IA signs it off.

The other factor is whether there is a CMM (component maintenance manual). If you are totally anal about it, no CMM means the component cannot be worked on at all. I bet the 50 year old planes in question here were flying before anybody could spell "CMM". On things like Spitfires (AIUI) you can fabricate replacements if you have the manufacturing drawings, and for a Spit they do exist.

But then a Spit is not on an ICAO CofA which alone makes a massive difference to what you can do. We need to be comparing like for like.

Here in Europe, EASA-reg, the flexibility is gone unless you do stuff off the books. Put that together with crap lubrication (just squirting an aerosol lube into the bearings/bushes, without dismantling them and cleaning them) and that's why people with 30 year old C152s may be paying £7k to get them through the Annual.

MT has an STC for 3 blade props on the Twin Com

One of my personal favourites is the Rockwell 680/685. There's quite a lot of them in use in the Caribbean and Bahamas flying the inter island charter routes. It's fun flying too and the high wing is an advantage in tropical sunshine. I suspect though that you'd have to do a lot of research on the marque in order not to get slightly stung. The simple selection has to be the Twin Commanche. It has it's foibles though so a knowledgable conversion instructor, experienced on type, is a good idea.

I would suggest accepting the extra 20 litres an hour and just go for a twin version of what you have already!

Find a decent Seneca III. Better than the II in a few ways - extra 20 hp on take-off or EFATO, better cockpit layout, better weights (I think the MZFW of the II is limiting, although I only have a few hours on that so don't quote me).

Basically Piper never improved the Seneca from the III, just made it heavier with gimics.

The Seneca will be lovely and familiar to you. It will be cheap to buy (probably under US$100k) which makes up for the fuel burn over the Diamond or Tecnam, although not as cheap as a Comanche. However it won't be as old as the Comanche either, and it is larger. The cabin will of course be very familiar to you, as I understand will the handling.

The Seneca III is a great aircraft.

Still think the the lower running costs of the P2006 will replace alot of old iron. We are still on the mark one version of the aircraft. Things like low service ceiling and range may only improve with further revisions.

I would be very surprised in Tecnam don't put the new fuel injected rotax on the airframe in 912 and all probability 914 form. This will reduce fuel burn further, increase the range and possibly increase the service ceiling.

I agree with you Mickey. Apparently the new 912iSc has a 30% improvement in fuel economy. Granted, this is Bombardier marketing speak, so might not be entirely truthful. But a twin that burns 7gph in total, and can all of a sudden go 900nm on 62 gal of fuel, is going to make some inroads. I'd get one of those when they become available in a heartbeat if I could find the cash for it.

From a dollar vs capability calculation, twins represent a pretty good deal.

For example Barons are selling for less than the same model year Bonanza's, yet are 30 knots faster, carry more, have the redundancy of 2 engines, 2 vacuum pumps, 2 alternators, and many have deice and radar fitted.

Yes the total ownership cost will be more but you are also getting a lot more airplane. The big problem is finding a twin that has been properly maintained. There is a lot of neglected junk out their but a twin in good nick will not cost significantly more to maintain than the equivalent single and so insurance and fuel represent the biggest source of extra expense.

I don't get the P2006 for a private owner. If you are over 55 years old, for the price of a P2006 you could get a nice Baron/Aztec/Cessna 310 and pay for all the fuel and maintenance for the rest of your flying life and still be ahead.

Only if you never fly it, BPF. At just 100-150hrs per year, the Tecnam will be cheaper to own, even when financed, compared to a paid off dinosaur twin.
I've done the spread sheet.

You would have to spend another 450 K to buy the P2006. Financed, that is at least 3500 USD a month even with a 20 yr pay out. Plus probably an extra 200 USD a month for the higher hull insurance premium. 15 hours a month at 25 gal/ hr is 1875 USD vs 15 hours at 10 gal/hr for the P2006 which is 750 USD. The delta is over 2500 USD a month or $30,000 a year. Yes there is going to be more maintenance with the older twin but over a 20 year life it is hard to see how you come out ahead with the P2006....

FWIW, I bought a new plane 10 years ago, for £230k inc VAT, and have never regretted it.

The warranty bill came to about £100k (largely because they built the panel out of a pile of "serviceable" avionics which came back from customers, I am 99% sure) but as I say that was met under warranty :)

And then I had really minimal unscheduled maintenance for 10 years.

So a case can be made for buying something new. It probably depends on how lucky you feel :)

But the Tecnam twin has a more serious issue of having insufficient performance for IFR long distance flights around Europe. I won't get you high enough for sure, and arguably it won't get you far enough in the often sparse matrix of avgas v. Customs we have here. Nobody is going to pay that kind of money for that capability. By the time you have that much dosh to spend, you will hopefully have been kicking around this business for a few years and you will know what mission capability is required for what. And if you are a fresh PPL with loads of dosh you will do what everybody else does and buy an SR22 :)

They are aiming at FTOs and government surveillance stuff - just like Diamond with the DA42. There are actually relatively few private DA42 owners, and all those I know personally are deeply unhappy with it (mostly because of the Thielert business, but also due to general low QA) and even less happy with the factory and the customer service they get from there.

BPF

Are you sure about the MT STC? None of us seems to know about it inc. AP&IAs.

Rotax have just launched the new fuel injection and ECU control module for the 912S. This is clamed to improve fuel economy by a significant amount so may go some way to solving the range issue. TBO is 2000h, not the 1500 which was quoted in an earlier comment.

Rod1

And I am not the only one to distrust electronics even in a car engine, far worse for flying. One of the common factors of success of the current Rotaxen and the older US'an engines is the lack of electronics (with a little exception for the ignition modules and the regulator in the Rotax).

I just read the AVweb announcement. The only claim I could find was:

So I think they're comparing the 912iS to the likes of the O-200, and claim 30% lower fuel consumption than those. Well, duh. That's what the 912S already achieved.

I can't see any claim that the 912iS will have a significantly lower consumption than the 912S. And I would not consider that likely anyway: The altitude-compensated Bing carburetors on the 912S are already pretty efficient. Fuel injection offers a lot of benefits, but significantly lower fuel consumption isn't one of them.

Power output will be 100 HP too, by the way. Exactly the same as the 912S.

So betting on a better future for the P2006 just because there's a 912iS now is not a good idea, as far as I can see.

As far as I'm concerned, the 912 and 912S are great engines for two-seater VLAs and MLAs, and the 912iS will offer a few operational and maintenance benefits over the 912S. (But no significant performance increase.)

But putting two of them in a four-seater twin is just overreaching. Particularly since the whole contraption has to stay in the air if one fails.

Consider this: A realistic four-seater (not a "2+2") single needs about 160 HP. So any four-seater twin should require at least about 160 HP in each engine as well, to have any realistic flight performance on one engine.

Rotax has an excellent reputation for reliability. Fuel ignition is something I think they've worked on for a long time. I don't think this has been some skunk works project where they are just trying out something. So for now I'm giving them the benefit of the doubt (although that doesn't buy them much since I am not in their target market segment).

I would be interested in the ECU though. Did they design something from scratch, or just bolted on a stock standard automotive (e.g. Bosch) ECU, or something in between?

Well, by now we should all have learned that if we want a 4-seater with mission capability, we need to buy a 6-seater. It's unfair to criticise any aircraft for not being capable of filling the seats, filling the tanks and go 1000nm. There is no aircraft that can do it.

The Tecnam is no exception - it's a 2 seater twin with full capabilities, or 4 with less. That's fine by me as I fly on my own 90% of the time. I feel that unfairly, just because it's a twin, it gets compared to Senecas, Barons and King Airs that have over twice as much power. It's not that kind of aircraft. It's reinvented an old class and should be compared the long forgotten Wings Derringers or Miles Geminis, rather.

I don't see how they can deliver a 30% better SFC than another petrol engine operated at peak EGT or LOP.

The old Lycos already outperform any petrol car engine, of any era, on SFC. A higher-RPM engine like a Rotax should be slightly worse than a low-RPM direct-driven engine due to greater friction losses.

Seems to me some are still convinced we have proved particles can travel faster than light. It is a challenge rewriting the laws of physics and when it comes to the most basic (such as the fuel efficiency of engines and light aircraft) you have a real job on your hands.

You will get some efficiencies from automated and metered injection but even these are not going to be substantial, beyond that the physics of a combustion engine dont change a great deal from one make to another. In exactly the same way, make the fusealage more narrow, bin the spats etc all will have a reasonable impact on the engine(s) required and in turn on the ful burnt, but you get nothing for nothing. Some like sitting shoulder to shoulder in a Mooney and cosying up, others like to keep their friends a little further away and if they are big fat American friends will probably fly a Cirrus!

So in short I am afriad there really is no free lunch, the P2006 achieves its efficiency largely in the ways I have suggested and perfectly good I am sure it is but it is not because there is any amazing new technology that is at work - just the tried and tested, keep down the weight, keep down the drag and operate the engine at LOP or there abouts and anything you do beyond that will not amount to much of an improvement.

I really don't see this in the real world.

My findings are that the fuel burn is significantly less with a 912 than a continental.

At my local flying school we bank on a fuel burn of about 20 ltrs an hour for the o-200. The 912 about 14.

Probably largely because the Conti is flown full-rich. That is worth about 30% :)

Adam Frish wrote:

The Comanche 260C (and maybe the 260B) will take 4 people, full tanks (90gl), some bags and do 1000nm. The twincom with tip tanks will do the same.

...and if you have a 260C with tip tanks such as ours, you can trade the fourth seat for adding the tip fuel and getting another 400nm range.

Amazing how so many people simply refuse to see how amazingly efficient the Comanche is, just because it's old and they're blinded by shiny new plastic.