BeechTalk - BT

Username Protected · **Posted:** 27 Jan 2016, 12:07

Username Protected wrote:

I'm not assuming anything. I'm looking at available options. Nobody makes a twin SF50. This thread is about a real product that has tracks on flightaware and will be available for sale very soon. Or should I say, that is what I thought we were discussing.

Lol, and you expect BT to stay on point?

Tim

Username Protected · **Posted:** 27 Jan 2016, 12:13

a twin SF50 is gonna need some more fuel storage...which could eat into cabin space

Username Protected · **Posted:** 27 Jan 2016, 12:13

Username Protected wrote:

But wait, the EA550 cost more than the SF50, so doesn't that prove the point?

The present cost structure of the SF50 and Eclipse are skewed. The SF50 has not yet made it into actual production, so the pricing is likely optimistic. The EA550 isn't designed to be made in handfuls per year like it is presently, so the costing is skewed the other way. Net result, neither example represents a reliable cost point for the SEJ versus TEJ debate when you compare apples to apples.

Mike C.

The bold portion primarily affects the capital and setup costs. e.g. you need a 50 ton metal stamping device that can handle one piece a minute versus one an hour. It does not have a significant effect on the actual cost to manufacture. Since the production line is dedicated to Eclipse, you do not have any change over or setup overhead, and the manufacturing equipment has already been paid for by the bankrupt company....

Tim

Username Protected · **Posted:** 27 Jan 2016, 12:25

Username Protected wrote:

a twin SF50 is gonna need some more fuel storage

Your piston think is showing again.

Twin needs less fuel.

Flies higher, burns less per mile going faster.

EA550 has 45 gallons LESS fuel than SF50, goes FURTHER, on TWO engines.

The rules you understand for piston airplanes do not apply to jets.

Mike C.

Username Protected · **Posted:** 27 Jan 2016, 12:28

Username Protected wrote:

I'm looking at available options. Nobody makes a twin SF50.

Nobody makes a single one, either.

Cirrus has been keeping a lot of stuff secret so we don't actually know what it is they intend to sell.

My point all along is that Cirrus has made a strategic mistake in making the SF50 a single. Given the same development time and money, a twin would already be out and flying in customer hands and performing much better.

Mike C.

Username Protected · **Posted:** 27 Jan 2016, 12:34

Username Protected wrote:

Given time, guess what, knowledge and technology have alleviated the majority of the issues to a point where a single piston is very close to a twin piston in terms of capabilities.

Jet is not a piston.

Mike C.

Username Protected · **Posted:** 27 Jan 2016, 12:38

Username Protected wrote:

Given time, guess what, knowledge and technology have alleviated the majority of the issues to a point where a single piston is very close to a twin piston in terms of capabilities.

Jet is not a piston.

Mike C.

Username Protected · **Posted:** 27 Jan 2016, 12:43

Username Protected wrote:

He makes a fair point. Compare a Pilatus to a King Air.

oooohhhh, can I take that one Mr Ciholas?

Username Protected · **Posted:** 27 Jan 2016, 12:43

Username Protected wrote:

Compare a Pilatus to a King Air.

Not jets.

Mike C.

Username Protected · **Posted:** 27 Jan 2016, 12:56

Username Protected wrote:

Compare a Pilatus to a King Air.

Not jets.

Mike C.

Username Protected · **Posted:** 27 Jan 2016, 13:03

A propeller

Username Protected · **Posted:** 27 Jan 2016, 13:05

A duct.

Username Protected · **Posted:** 27 Jan 2016, 13:08

Username Protected wrote:

What is the difference between a modern turboprop engine and a high bypass turbofan?

About 100 knots and 15,000 ft.

The prop begins to lose performance at high true airspeeds and in thin air. The turbofan does not. This is because the prop turns slowly, the fan does not. The slow prop has a high advance angle and the blade thrust is not aligned in the direction of flight.

Example of high advance angle ~300 knots and ~FL250, 1600 RPM:

https://www.youtube.com/watch?v=ugvWNAXgswE

Put that at 400 knots and FL410 and the prop simply can't produce good forward thrust.

Meanwhile, fans are running 15,000 to 20,000 RPM. They don't suffer the issue of high advance angle.

You can't speed up the prop to 15,000 RPM, it would go supersonic and fly apart as well.

Mike C.

Username Protected · **Posted:** 27 Jan 2016, 13:13

Username Protected wrote:

Compare a Pilatus to a King Air.

Not jets.

Mike C.

Username Protected · **Posted:** 27 Jan 2016, 13:26

Username Protected wrote:

...fans are running 15,000 to 20,000 RPM. They don't suffer the issue of high advance angle.

Though it naturally varies with size, fan speeds are generally in the 2,500 - 7,000 rpm range.
A 4' diameter fan will have the tips go supersonic at approximately 5,000 rpm.

Cirrus SF50