So you think Cessna didn't know that when designing the 525?

Yeah, they knew, and they figured out the right design point for the wing. That would have been a very basic part of the design. Airfoil shape, wing span, aspect ratio, etc.

You think they would leave 15% range on the table?

No way.

This is why I don't think there is 15% to gain with wing extensions/winglets.

Mike C.

Exactly. There’s a difference between a winglet and an active winglet. The small active aileron unloads the wing as necessary to prevent over stressing. Cessna never had that technology.

At cruise, most of your drag is parasitic (drag from the shape), and not induced drag (drag from creating lift). The winglets actually increase parasitic drag from higher frontal and wetted area. They do reduce induced drag, but not by an amount that would reduce the overall drag by 15%.

CJ2+ at FL450, ISA, 11000 lbs, MCT:

Stock per Cessna manual: 388 KTAS, 683 lbs/hr

Tamarack claims: 400 KTAS, 683 lbs/hr

Specific range improvement is just 3%.

And that does NOT account for the fact the Tamarack airplane is heavier by about 200-250 lbs. Interpolating their chart, this means:

Tamarack claims at 11,250 lbs: 400 KTAS, 688 lbs/hr

Specific range improvement: 2.3%

Yes, there is benefit on faster climb that the cruise numbers don't take into account, but that improvement can't be big enough to yield a net 15% range improvement. At MGTOW, ISA, CJ2+ gets to FL450 in 28 minutes and 555 lbs of fuel without the winglets. 555 lbs is just 14% of the total fuel capacity of the plane, so how the heck do you save 15% right there? Winglets help, but there sure can't MAKE fuel in the climb.

It should also be noted that CJ2+ routinely exceeds book speeds. If Tamarack is getting 400 knots instead of 388 in the book, much of that may have already been in the plane itself before the mod.

So, I remain highly skeptical. The numbers don't add up. Boeing, who would do ANYTHING to improve range 0.5%, can only get about 4% range improvement out of winglets.

If I owned a CJ series, I'd steer clear of the Tamarack winglets until they have a proven service history and their benefits can be objectively measured. Let the early adopters find all the bugs and issues. It wouldn't surprise me if, in 3-5 years, Tamarack is out of business and the mod is frowned upon in the market and perhaps unsupportable in the long run.

Mike C.

At cruise, most of your drag is parasitic (drag from the shape), and not induced drag (drag from creating lift). The winglets actually increase parasitic drag from higher frontal and wetted area. They do reduce induced drag, but not by an amount that would reduce the overall drag by 15%.

CJ2+ at FL450, ISA, 11000 lbs, MCT:

Stock per Cessna manual: 388 KTAS, 683 lbs/hr

Tamarack claims: 400 KTAS, 683 lbs/hr

Specific range improvement is just 3%.

And that does NOT account for the fact the Tamarack airplane is heavier by about 200-250 lbs. Interpolating their chart, this means:

Tamarack claims at 11,250 lbs: 400 KTAS, 688 lbs/hr

Specific range improvement: 2.3%

Yes, there is benefit on faster climb that the cruise numbers don't take into account, but that improvement can't be big enough to yield a net 15% range improvement. At MGTOW, ISA, CJ2+ gets to FL450 in 28 minutes and 555 lbs of fuel without the winglets. 555 lbs is just 14% of the total fuel capacity of the plane, so how the heck do you save 15% right there? Winglets help, but there sure can't MAKE fuel in the climb.

It should also be noted that CJ2+ routinely exceeds book speeds. If Tamarack is getting 400 knots instead of 388 in the book, much of that may have already been in the plane itself before the mod.

So, I remain highly skeptical. The numbers don't add up. Boeing, who would do ANYTHING to improve range 0.5%, can only get about 4% range improvement out of winglets.

If I owned a CJ series, I'd steer clear of the Tamarack winglets until they have a proven service history and their benefits can be objectively measured. Let the early adopters find all the bugs and issues. It wouldn't surprise me if, in 3-5 years, Tamarack is out of business and the mod is frowned upon in the market and perhaps unsupportable in the long run.

Mike C.

Tamarack's own numbers show that improvement in specific range to be 2-3% over the Cessna book numbers.

If Tamarack can get 15% more range with this mod, then yes, it is magic since their own numbers don't support that.

Mike C.

I love it when really smart people argue, er, debate.

Especially about topics that ar interesting.

This is calculable.

At 11,000 lbs, stall speed flaps up zero bank is 97 KIAS for a CJ2+ (keeping with the example airplane I used before).

At an AOA of 1.0, you are stalling and generating all the lift the wing can at that airspeed.

The lift you can generate is proportional to the square of the airspeed, and proportional to the AOA. At double the airspeed, you can generate 4 times the lift at 1.0 AOA, or the same lift at an AOA of 0.25.

The CJ2+ in my example was cruising at 181 KIAS, M 0.69, at FL450, ISA, MCT. That's 1.87 of stall speed, which works out to an AOA of 0.29. It is FL450, after all.

If you slow down to M 0.65, that is 170 KIAS. That is 1.75 of stall speed, which works out to an AOA of 0.33.

To get to AOA 0.5, that would require being at 1.41 stall, 137 KIAS, M 0.52.

Going from M 0.70 to M 0.65 doesn't sound like it would take you from AOA of 0.2 to 0.5. That sounds exaggerated.

Capture a video of this, it would be educational. Fly at M 0.65 steady in cruise, observe AOA, then accelerate to M 0.70 and observe change in AOA. Let's see what the numbers are.

(Note that stall speed does change with high altitude somewhat, I ignored that aspect, not too great a change in the M 0.70 and under region, though).

Mike C.