Charles is bang-on when he asks if anyone has a POH?

Sales literature lies. It's created by a marketing department in a reality-distortion field to deceive the gullible. It is absolutely meaningless. I learned this the hard way on my first new airplane purchase.

The only accurate reliable information will be found in a POH with a real W&B sheet.

Despite requests, Cirrus has not released it, not even, apparently, to position holders. I suspect only owners have a copy so far.

I'll get one eventually. Probably a lot of juicy stuff in there...

Note that SR22 AFM/POH is free on line.

http://servicecenters.cirrusdesign.com/ ... 72-006.pdf

If you go to the tech/pubs Cirrus web page:

https://cirrusaircraft.com/service-support/

And select SF50, you can see there are already quite a few SAs/SBs (I count 16 already!) and notes on SF50s. Some of them are AFM revisions (8 already), so you can get SOME data from that. Example is a takeoff performance revision:

http://servicecenters.cirrusdesign.com/ ... 7-05R1.pdf

One note particularly caught my eye:

"Tailwind:Add 40% to the ground run and 35% to the total distance for every 10 knots of tailwind."

Holy heck! Basically, never have a tailwind on takeoff!

The takeoff data basically says the plane is underpowered.

Reading the other AFM revisions gives some insights, but it isn't the complete AFM of course.

This ain't no SR22.

Mike C.

Mike what's your take on the SF50 thermodynamic power/effective thrust?

How can something with allegedly decent thrust/weight be so slow to accelerate and climb? Is it purely the engine cant?

Am I reading page 5 correctly? Airplane can’t be started or operated in Denver above 100F OAT? Santa Fe above 92F? The *average* summertime high in Santa Fe isn’t much less than that.

Is this type of restriction typical?

That upper temperature line is ISA+30.

Some planes are limited to ISA+30 (MU2 is).

Some planes are limited to ISA+40 (CJ, CJ2+ for example).

Some are in between (ISA+39 for Citation II/550).

So not unusual, but not necessarily the same as others.

Mike C.

Peak average high temp in Santa Fe is 83F around July 4.

90% of the time, on that date, the high is 90F or lower.

https://weatherspark.com/m/3506/7/Avera ... ted-States

It is not all that rare for a jet to need to depart in the morning to meet runway and other limitations.

Mike C.

I think it is a combination of engine cant (pushing the wrong direction, and the reaction in the deflector plate) and the overall aerodynamic inefficiency (bulbous cabin with large cross section, airfoil optimized for lift over drag, and finally the ridiculously draggy tail due to size and 4 interference drag points).

There could also be a low pressure area right in front of the engine inlet due to cabin curved surface. The engine is thus struggling to breathe. Normally in turbines, increased airspeed means the engines develop more and more power (mine increase about 10% during a takeoff run, jets can be similar). But if the cabin thins the air out, effectively shields the engine from ram air, that won't happen.

This plane is winning no efficiency awards.

If you put the takeoff and climb numbers of an EA500 next to the SF50, it will be embarrassing. The EA500 has *lower* thrust to weight ratio.

Notice how different this is from pistons. "Twin" does not mean "inefficient" for jets.

Mike C.

got it, thanks.

What's the ground roll of an Eclipse at MTOW and ISA? Looks like the SF50 is ~2,000'. All I can find for the Eclipse is the over 50' length.

Chip-

You won't find "ground roll" in many AFMs. The FAA requires distances to some point in the air.

FAR 23 specifies what the book should say. For landing, FAR 23.2130(a) applies to everybody:

The distance, starting from a height of 50 feet (15 meters) above the landing surface, required to land and come to a stop.

For takeoff, it is a bit more complicated. The SF50, being a single, is subject to FAR 23.2115(b):

For single engine airplanes and levels 1, 2, and 3 low-speed multiengine airplanes, takeoff performance includes the determination of ground roll and initial climb distance to 50 feet (15 meters) above the takeoff surface.

For the EA500, it qualifies as a "high-speed" multiengine airplane (Vmo > 250 KCAS), so it becomes subject to FAR 23.2115(c):

For levels 1, 2, and 3 high-speed multiengine airplanes, and level 4 multiengine airplanes, takeoff performance includes a determination the following distances after a sudden critical loss of thrust—
(1) An aborted takeoff at critical speed;
(2) Ground roll and initial climb to 35 feet (11 meters) above the takeoff surface; and
(3) Net takeoff flight path.

In summary:

SF50 takeoff distance is to 50 ft AGL.
EA500 takeoff distance is to 35 ft AGL *after an engine fails*.

SF50 and EA500 landing distance is from 50 ft AGL.

Why does the FAA do it from in the air?

First and foremost is that pilots should not be seduced by ground roll numbers into thinking that's how long a runway they need. You can't touch down right at the threshold, for example. So this builds in a reasonable margin.

Second, when flying an instrument approach, you end up over the threshold well above it, the threshold crossing height, and the landing distance has that already taken into account. Similarly, on departure, there can be runway lights, localizer antennas, and other structure just off the end of the runway you need to clear.

Lastly, the FAA doesn't want charts where the test pilot horses it off the ground only to wallow in ground effect. This would produce a very low ground roll number, but actually hurts distance to 50 ft quite a bit. By using 50 ft AGL, you have to do a more sane takeoff profile. It is the case that you use a longer ground run to have a shorter 50 ft distance. The goal is to find that speed and procedure that gets you to 35/50 ft in the least distance.

Yet, some makers do list ground roll numbers and Cirrus does for the SF50, but I don't think Eclipse does for the EA500/550.

The SF50 numbers for ISA, max allowed weights takeoff and landing, sea level, from this:

http://servicecenters.cirrusdesign.com/ ... 7-05R1.pdf

Takeoff: 3,326 ft (2,115 ft ground roll)
Landing 100% flaps: 3,011 ft (1,628 ft ground roll)
Landing 50% flaps: 3,345 ft (2,293 ft ground roll)

(I had to interpolate numbers since 15C is ISA)

I don't have an EA500 AFM, so numbers came from here:

https://www.flyingmag.com/aircraft/jets ... pse#page-2

Takeoff: 2,345 ft
Landing: 2,250 ft

I presume these are ISA, max weights, from FAA prescribed altitudes (they do say sea level).

Note that the EA500 numbers assume an engine failure *on the runway* at V1, then climb out one engine off, and the plane meets those numbers. With both engines operating throughout the takeoff, the EA500 will EASILY beat those numbers.

What are the take aways?

The EA500 dominates the SF50 when it comes to runway usage.

The EA500 takes off, *with an engine failure at the worst moment* in 1000 ft less than an SF50. This despite the SF50 having a *higher* thrust to weight ratio. Granted, the EA500 distance is to 35 ft and the SF50 is to 50 ft, but I can estimate the SF50 to 35 ft distance is only about 300 ft shorter, so the EA500 beats it to 35 ft AGL by 700 ft with one engine off.

On landing, both from 50 ft, the EA500 beats the SF50 by 750 ft if you use 100% flaps, by 1,100 ft if you use 50% flaps. Neither plane has thrust reversers. I don't think either have ABS either (EA500 has that as an option now).

The 100% flap SF50 landing distance numbers have an oddity. Generally speaking, the ground roll on landing is 1000 ft less than the landing distance. This is because a 3 degree slope from 50 ft takes 1000 ft distance, and that is why the touch down markers on instrument runways is 1000 ft from the threshold. And the 50% flap distances are right in that ball park.

But the SF50 100% flap numbers show the plane touching down about 1400 ft past the runway threshold (3000 ft landing distance, 1600 ft ground roll). Why? Feels like the plane Vref speeds are too high for the flare and it floats, but they can't lower them much due to balked landing climb requirements. So they end up having a float down the runway to bleed off excess speed they need to carry in the approach.

The above reason is hinted at in the document I linked above. The landing chart has gray blank cells and this note:

The greyed-out cells in the subsequent table signify that the aircraft is not capable of meeting the regulatory balked landing climb gradient for these conditions.

Those requirements are in 23.2120(c) which requires a 3 percent climb gradient in the landing configuration (that is, you have to be able to climb at least as fast as you came down on the approach). The 100% flap chart has a lot more grayed out boxes than the 50% flap chart, but the tradeoff is much longer landing distances.

I've attached the charts below.



Mike C.

Tires:

Nose 88 PSI 5.00x5, 10 ply, about 14 inches diameter, 4.75 inches tread width
Mains 105 PSI 18x5.5, 8 ply, about 17.5 inches diameter, 5.5 inches tread width

Not a turf runway airplane with those small tires and high pressures.

I bet tire life won't be great with long runway usage, small sizes, heavy braking, and high pressures.

The tire sizes are pretty much what is on a 172 (5.00x5 nose, 6.00x6 mains which are basically the same size as the 18x5.5).

Mike C.

SF50 versus Citation SII on runway usage, sea level airport and then Denver:

0 MSL, ISA (15C), max weight, zero wind:

Takeoff:
SF50 (6,000 lbs): 3,326 ft (flaps 50%)
SII (15,100 lbs): 3,240 ft (V1 93 KIAS, flaps 20)

Landing:
SF50 (5,550 lbs): 3,011 ft (flaps 100%)
SII (14,400 lbs): 2,640 ft (flaps landing, no thrust reverse)

6,000 ft MSL, ISA (3C), max weight, zero wind:

Takeoff:
SF50 (6,000 lbs): 4,111 ft (flaps 50%)
SII (15,100 lbs): 4,460 ft (V1 95 KIAS, flaps 20)

Landing:
SF50 (5,550 lbs): 3,479 ft (flaps 100%)
SII (14,400 lbs): 2,970 ft (flaps landing, no thrust reverse)

On takeoff, the SII beats the SF50 at sea level by a fraction, and is 8.5% longer at 6000 ft. On landing, the SII is less at both altitudes.

Note that takeoff is with the SII having an engine failure at V1 on the runway. In the absence of engine failure, the SII wins easily. Landing is also without using thrust reverse on the SII which will shorten the distances a fair amount.

(Why SII? I've been looking into it as my next plane, so I had data for it)

Mike C.

Closing in on 400 pages... remarkable.

Mike Ciholas' posts on this subject easily exceed 50% of the total

Mike Ciholas: 969 posts
Total posts: 5775 posts

16.8%

Mike C.