The SF50 is fundamentally not designed to fly at FL410, so even a regulatory change would not allow it.

If the SF50 was redesigned to fly at FL410, but still remained an SEJ with an X tail, its performance would be less than an Eclipse. Aerodynamically, it just can't be as efficient as the Eclipse plan form.

Mike C.

Well, for one obvious thing, the cabin PSI limits won't allow a suitable cabin altitude at FL410. To change PSI requires huge changes in structure, doors, windows, etc.

A more subtle issue has to do with stability requirements in the thinner air. V/X tails are not noted for being so stable to begin with and I predict the stability the would get at FL410 is inadequate as currently designed. The thin air simply doesn't dampen motions as well. This is why lots of high altitude airplanes have yaw dampers as required equipment.


The SF50 V/X tail design is intrinsically more draggy than the T tail of the Eclipse due to trim drag and higher wetted area. An X tail also has four surface to fuselage interfaces to cause drag, basically negating one of the few V tail pluses.

The SF50 canted engine thrust line is not aligned with the direction of flight, thus wasting thrust and requiring a deflector plate. The Eclipse engines are aligned with the flight path, nothing to disturb the jet outflow.

The Eclipse has two engines, each 900 lbs thrust, total 1800 lbs thrust. The SF50 has one engine, 1900 lbs thrust.

At FL280, Cirrus says (unverified) SF50 will do 300 knots on 69 GPH.

At FL280, EA500 will do 308 knots, 62 GPH, verified by actual example.

Less thrust, less fuel flow, but more speed, EA500 is more efficient being a twin than SF50 being a single.

Yes, this is backwards from pistons. Piston think doesn't work on jets.

Let the EA500 go higher and the advantage increases dramatically, much higher speed, much lower fuel burn, than the SF50.

Mike C.

I'm no Aeronautical Engineer, but that engine canted down can't be very efficient.
In fact, I'm willing to bet that the empennage has to work even harder [vs T tail) to push the tail down, creating even more drag.

Yuri,

Your typical "Wall St. Fat Cat" better be making 1-2 million a month, not a year, if he has any chance of supporting your described lifestyle.

The Pilatus burns 50 GPH at FL280. Why would the SF50 burn so much more?

Propulsive efficiency is likely better with the TP.

I'm going off King Air numbers, but the basic engine design is the same as the U-28/PC-12.

Engine is running closer to redline temp, which takes efficiency up a bit, and the prop hasn't fallen off the efficiency curve yet.

Jet is a bad way to make thrust unless you are using the speed or going high.

It is a jet.

Mike C.

Hey, I support a similar lifestyle on mere couple of hundred grand. I just rent instead of owning in Hamptons and fly an old Debonair instead of a jet.

You don't have to be rich to be happy... Or at least, that's what I keep telling myself.

This may be the case, but it's the case across all altitudes. If anything, would be a good reason to push the SF50 higher, less drag.

It's pure speculation, but Cirrus has a track record of not standing still. The current SR22 G5s are far more capable airplanes than the first SR22 G1 models. My guess is the jet will have a similar evolution. Installing a backup pressurization system of some type, and certifying to a higher altitude is a very logical move for a "SF50 G2" model.

Someone better read that a few times till it sinks in....

Andrew

Best way to visualize this:

Harrier vs Helicopter. If you need vertical takeoff, Which is the more efficient way?

The only reason a Harrier (or B model JSF) has all the tech and money thrown at it is an attack helicopter isn't fast enough.

Are you saying the Cirrus engineers overbuilt the fuselage by 35%? Did they do that to everything on the airplane?


There are only two choices:

1. It will require considerable rework.

2. Cirrus incompetently overbuilt it.

Take your pick.

The "we can overload it by 35% and nothing bad will happen" idea is a non starter for competent aerospace engineers.


It isn't about IAS. The thinner air and higher true airspeed create effects that are not IAS related. Damping is less, so disturbances last longer and oscillate more. This is why a high altitude airplane operating at 200 KIAS needs stability augmentation like a yaw damper, whereas one operating at low altitude, same 200 KIAS, doesn't.


It is called a "second engine".

Nothing else is as simple or effective as that.

From FL410 to 15K will take 30 minutes in a best glide. Try to design a backup pressurization system, with NO engine operating, that runs that long. I bet it ends up weighing MORE than having two engines due to batteries.

You may say "but I will do an emergency descent and not take so long". You just eliminated 90% of the possible landing sites by giving up your glide distance so readily.

Mike C.

It has a parachute

It is a jet.

Mike C.

It is not a jet.

Mike C.