@ Mike.

Thank you for your detailed comments. I am not sure that the gentleman from Avweb was directing his report as a marketing tool.

The Jet makers are absolutely right to introduce such a product. I see plenty of appeal with owners that are quite alright with these limitations that you correctly quote.

Range limitations due to RVSM is quite real but manageable, spending more than four hours in a plane is tough no matter the comfort, I know a few things about that...

I am not aware of the noise issue however I agree that the quieter the better.

Many points you make are spot on... Chute, yaw damper, servos working excessively, l do not see such an impact that makes this a deal breaker, this plane will sell.

The point is that in reality before I would drop that kind of money a straight CJ with Tamarack winglets is where I would go.

For now I will enjoy flying my bosses "Jets" and when home my piston plane.

Regards...

Yes, you have managed to pull forward the few critiques mentioned in the Aviation Consumer article, Mike. Congrats.

But, you've skipped the paragraphs that use words like perfect and superb and sexy.

The title of their article is: "Cirrus Vision Jet: Near Perfect Execution"

And the final sentence says: "For those who can afford the $2 million entry fee, we think they’ll get one of the best-value high-end personal aircraft we’ve evaluated."

Oops..

Scott, very, very interesting observation from a systems perspective.

The one I can afford (which is none).

Tim

I think the thing looks a whole lot better if you stop looking at it as a jet, and start looking at as a new Cirrus model, with a ~$1.1MM engine upgrade.

My apology to the many who have likely posted this exact thought in the prior 367 pages. I might have even done it.

apologies accepted. This isn't about the Cirrus anymore. It's strictly entertainment.

ATC has decided it is a turboprop.

From Flying review:

The vertical speed indicator showed a climb of 1,250 feet per minute, not eye-popping performance but not bad for a single-engine airplane loaded with three adults, baggage and 230 gallons of fuel on a relatively warm day.

I thought we were climbing quite nicely, but it didn’t take long before New York Departure lost patience with our progress. It was bad enough that the controller had to ask what a Cirrus Vision was; once Matt explained that we couldn’t climb at a faster airspeed we were instructed to level at 6,000 feet and stay there to accommodate crossing arrivals into Newark Airport. Jets aren’t intended to fly low for extended periods of time due to the higher fuel burn; on a number of occasions during our trip, ATC didn’t quite seem to know what to make of a turbojet airplane with performance closer to that of a turboprop. With time they’ll figure it out, but carrying a little extra fuel for low-altitude excursions is probably a good idea.

New York Approach wouldn’t allow us to fly the jet arrival. Instead they put us on the “turboprop only” arrival, which — you guessed it — put us at a lower altitude.

Turboprop procedures, designed for lower altitudes and speeds, will burn even more of that previous fuel over what a real jet gets to do.

SF50 performance:

Altitude: FL280, like a turboprop
Range: ~1000nm, like a bad turboprop
Payload: 400 lbs full fuel, like a bad piston twin
Speed: 280-300 knots, like a turboprop
Climb: 1250 fpm 300 lbs under gross?, like a piston twin
Noise: need ANR headsets, like a turboprop
Redundancy: like a single engine turboprop

But it is like a jet in other ways:

Training requirements: like a jet
Maintenance costs: like a jet
Needing long runways: like a jet
Intolerant of icy, snowy, wet runways: like a jet
Fuel burn down low: like a jet
Engine program minimum hours: like a jet

So, yeah, the SF50 is basically a turboprop, a mediocre one at best, which inherits the negatives of a jet on top of that.

I think it is very telling that the Eclipse EA500, with a LOWER thrust to weight ratio, achieves 3424 FPM climb, 375 knot cruise, and 15% more range on 20% less fuel. I expected a performance penalty for the SF50 being a single, but I am surprised at the magnitude of the penalty that was realized. Cirrus obviously worked very hard on the "slowest" part of the design goal, they absolutely nailed it.

Mike C.

"The sidestick felt comfortable in my hand as I pitched for the best rate of climb airspeed of 160 knots. The vertical speed indicator showed a climb of 1,250 feet per minute, not eye-popping performance but not bad for a single-engine airplane loaded with three adults, baggage and 230 gallons of fuel on a relatively warm day."

http://www.flyingmag.com/cirrus-sf50-vi ... fly#page-4

Is it possible to back-calculate thrust, drag, etc using reasonable assumptions from that data?

That's what two engines do for you when it must be able to fly on one. Basically the SF50 is flying like a OEI jet at all times and it shows in the performance.

The the eclipse has a lower thrust:weight, something else is going on to explain climb performance. (Gonna guess cross sectional area, wing loading, control surface drag and thrust efficiency)

That argument would be true if the one engine had considerably less total thrust than the two engines did.

But in this case, the one FJ33-5A engine has MORE thrust than the two PW610Fs combined. 1 x FJ33-5A = 1846 lbf, 2 x PW610F = 1800 lbf.

So the SF50 is the same weight as an EA500, MORE thrust, and yet hugely less performance. Same power in, less results out, means inefficiency. And this is not about altitude, the climb performance sucks in the same air that the Eclipse makes 3424 FPM.

The rough equivalent would be taking a CJ2+ with two FJ44-3A-24 2490 lbf engines and replacing it with one 5000+ lbf thrust engine (say the PW306D used on the Soveriegn) and then the plane lost half its climb rate and 100 knots in speed.

I am pretty sure if you put one PW306D on a CJ2+, it would not suck as bad as the SF50 does. One wonders if Cirrus crippled the performance in some way on purpose, above and beyond the expected SEJ efficiency penalty.

Mike C.

Is that derated or max thrust at sea level?


Tim

That argument would be true if the one engine had considerably less total thrust than the two engines did.

But in this case, the one FJ33-5A engine has MORE thrust than the two PW610Fs combined. 1 x FJ33-5A = 1846 lbf, 2 x PW610F = 1800 lbf.

So the SF50 is the same weight as an EA500, MORE thrust, and yet hugely less performance. Same power in, less results out, means inefficiency. And this is not about altitude, the climb performance sucks in the same air that the Eclipse makes 3424 FPM.

The rough equivalent would be taking a CJ2+ with two FJ44-3A-24 2490 lbf engines and replacing it with one 5000+ lbf thrust engine (say the PW306D used on the Soveriegn) and then the plane lost half its climb rate and 100 knots in speed.

I am pretty sure if you put one PW306D on a CJ2+, it would not suck as bad as the SF50 does. One wonders if Cirrus crippled the performance in some way on purpose, above and beyond the expected SEJ efficiency penalty.

Mike C.

You'd have to know the engineering data for the FJ33-5A thrust for a given indicated airspeed, altitude, and temperature.

Assuming the engine can produce 1846 lbf at sea level, ISA, and 160 knots indicated:

Part of the thrust is needed to fly level at 160 knots. Part is needed to climb. The climb part can be calculated and then you can subtract that from the engine thrust to find the level drag.

"3 adults, bags, 230 gallons" probably equals 600 pounds cabin load and 1540 lbs fuel, 2,140 lbs useful load. Assume an empty weight of 3600 lbs, weight is 5740 lbs, or 300 lbs under max ramp weight.

To push that up a frictionless incline at 160 knots and achieve 1250 FPM requires a thrust of 443 lbf.

Now we don't know what the engine was producing, but we can assume it was less than the rating due to being above sea level and being ISA plus temperatures.

Let's assume the plane, at gross, can achieve ~2000 FPM at sea level and ISA (which seems to match numbers given by various sources, requires confirmation). That requires 741 lbf. The engine produces 1846 lbf, thus it takes 1105 lbf to fly level at 160 knots, or to say it another way, the plane has a drag of 1105 lbf at 160 indicated at gross.

In the article example, 1250 FPM ISA plus, we have 1105 lbf drag and need 443 lbf for climb, so engine output is 1548 lbf, or about 84% of rating. The drag would actually be a bit less due to lighter than gross weight, so the engine output would be correspondingly less of rating, maybe 1500 lbf.

But this isn't really right because the 1846 lbf thrust rating isn't at 160 knots indicated airspeed. You need data from Williams to know this number, and they don't give that out to anyone other than OEMs.

It should be noted that the EA500 has significantly less than 900 lbf drag since it can have an engine failure and still climb on one engine, and that's with the extra drag of asymmetric thrust.

Mike C.

What's your favorite jet Mike?