Wait a sec. I didn't care for your wording of the bet.

I will bet you $1K that IF the SF50 makes it to market it will be wildly successful and one of the hottest selling planes out.

Wait a sec. I didn't care for your wording of the bet.

I will bet you $1K that IF the SF50 makes it to market it will be wildly successful and one of the hottest selling planes out.

Yes. I do think the SF50 will make it to market also. It'll be here before the HondaJet too.

Sell? Yes.

Delivery? No.

If aviation was defined by what could be sold, it would look a lot different than it does today. For example, Moller flying car.

Unfortunately, the laws of physics, the realities of economics, and the regulatory environment of aviation determine what exists.

I'm not sure airline operating economics scale to private GA. When you fly a 777 four thousand hours/year, a 3% change in fuel efficiency becomes enormous.

But setting aside regs, I take mike's main point being that there's not a good place to put a single jet engine in a certifiable plane that has to carry a cabin. Whatever efficiency you may gain from a larger turbine is lost with installation problems.

But the point Mike misses is that a single large engine costs less to purchase. Sure you have more engineering issues, but those are largely a one time cost.


Tim

The basic Carnot cycle limits what you can do. Jet engines are most efficient the hotter they run. To run hot at low altitude means less air, means smaller compressor, means smaller jet engine. Then at high altitude the engine runs out of air and losses power. So you can't make it work well at both ends. The only thing Cirrus can do to make the airplane more efficient is to put a smaller engine in and suffer reduced cruise speeds at max cruise altitude and long time to climb, both of which make the plane even worse.

The most basic fact is that a jet at FL250 doesn't get the reduced drag of operating at FL410. So even if the jet engine gets better at lower altitudes, the jet airplane is still worse off than if it could fly high.


I don't know any passenger which gets uncomfortable having two jet engines instead of one. I know those that don't like having one.


All of us do. The implication some don't is strange.


Mostly concur, though I think Cessna could make a quite viable SETP and I bet it would sell fairly well. It astounds me what SETPs cost, and I think Cessna could build one under $2M.


It is no worse than the SF50 when that happens, and then 30 minutes into the flight, they can go to FL410 after leaving the congestion. The EA500 has the OPTION to fly high when it can, and most do.


Per capita, the middle of the country buys more aircraft than the coasts. They are the most useful in those areas. If you live at a major city with direct flights anywhere, a private aircraft is less useful.

For example, there are more SR20/22 registered in Texas than in California and New York combined, yet CA + NY populations are more than double TX. Private aircraft are not really an "urban" thing.

Mike C.

I was referring to mechanical efficiency - you make some gains having one big engine vs. two small but you lose something by the inability to position it ideally.

Economically, yes, that helps A LOT. Now the jet can be pushing through thin air, make high speeds, at low fuel flows.


It depends. If the jet is small enough, then certain techniques are enabled (such as "blisk" instead of individual blades) which result in cheaper parts. The primary issue with being smaller is needing tighter tolerances but then being smaller makes them easier to achieve.

PWC PW610F shows how small an engine can get and be quite efficient.


One FJ33 is cheaper to PRODUCE than two PW610F. But I bet the one FJ33 INVOICES for about the same as two PW610Fs.

The reason is that Williams needs to make back its development money somehow on HALF the units shipped. Also, the economies of production scale are lessened with half as many units. And then there is the residual revenue from engine operation and parts. Williams has half as many units to sell HSI and OH parts for as time goes by. The residual parts money can be worth MORE to Williams than the sales price of the engine outright.

Then lastly, Williams suffers higher liability for a jet engine on a single engine airplane. Every in flight shutdown is a potentially very serious accident whereas a twin jet is a nuisance that actually GENERATES revenue.

Add all that up, and the cost of the FJ33 to Cirrus for an SF50 is equal or more than two PW610Fs.


This is true. The larger single jet has better fuel specifics, say about 5% better. But the SEJ installation negates that advantage over a twin jet with pylons. Specifically in the SF50, the canted top mounted engine creates pitch moments that have to be removed by aerodynamic forces, and the V tail creates pitch trim drag. So the fuel specific advantage is negligible when looked at from a SYSTEM perspective.

And this didn't even discuss the altitude limits. FL250 or FL280 that SF50 gets is WAY less efficient than FL410 a twin jet gets.


Less cost (purchase, fuel, and maintenance) and the fact that more powerful engines are available now to enable large body twin jets.

2 versus 3 or 4 is a very different safety and regulatory question than 1 versus 2, however.

Mike C.

Not when the engine maker includes the extra costs for making only half the units, the lost revenue from parts supporting only half the units, the higher amortization per unit of development costs, and the higher liability given the engine is on a single.

And then the bigger engine simply costs more to make just from being bigger.

In the end, it is a wash between a big single jet and two smaller ones in terms of loaded costs on the airframe.

Don't apply piston think to jets. It doesn't work. There are no good reasons to have a single engine jet. The penalties for being a piston twin don't apply to jets.

Here's another aspect. The FJ33 has ZERO volume applications so far. The SF50, if it gets to market, will be the only type using FJ33 in any numbers. Guess which customer base now gets to be part of Williams field trials?

Recall the PW610F problems with combustor issues that the Eclipse folks suffered through. Shows you that even a highly tested and certified engine can have teething problems when put into actual service. Also, Williams had a pretty bad experience making the FJ22 (the canceled first engine for the EA500, cycle life 1!).

And the FJ33 engine, untested in the field to any significant degree, will be on a SINGLE! Scary!

If I really, really, really wanted an SF50, I'd wait until it has been in the field 2+ years and see what the teething problems are like, then buy one used IF the field history is good. Ask any Eclipse owner about the "early years" of having an entirely new airframe and entirely new engine built by a company entirely new to jets.

Mike C.

What do you propose as criteria for "wildly successful"?

Needs to be specific and testable with information available publicly.

Mike C.

People argued quite loudly that the Cirrus was a joke, until they took over the piston market.

People are saying the same thing about the jet… seems like deja vu.

Mike,

You write a lot but at the end of the day you're not the only guy who knows how airplanes work.

Cirrus has people that know how airplanes work too. If the SF50 is such a waste of time to produce, then why is Cirrus doing it? (Consequently, this IS how I feel about the HondaJet )

What's with the FL250 thing? My PC12 is certified to FL300. TBM I think goes to FL350. That said, there's not much reason to go higher than FL250 in the PC12 because it starts losing too much power. The SF50 doing 300 knots at FL250 is a market dominator. It doesn't need to go 400 knots. The whole point of the SF50 is to dominate the piston market. They're not trying to beat a Lear. Baron for $1.3MM or Cirrus Jet for $2MM?? Which would you chose?

As for the bet, I'll bet you $1K the SF50 is a wildly successful airplane on the market as opposed to "it's going to bankrupt the company and it's a complete waste of time", like you say. Can't get much clearer than that.

Now that's about the smartest advice I've heard on this topic. Learned my lesson buying a larger first run boat. The early Eclipse stories are stuff of nightmares.

Other than owners of other brands that lacked the innovations and attributes I don't recall anyone calling the Cirrus a joke. Maybe a cruel joke.

Still I see the plane as a fad, just like the VLJ fad in general that appears to be a tremendous flop. I actually would want a jet one day if the need arises but I dang sure want to get over weather.