Please educate me....

[Half Fast]

I just read the article about the Remox GXiS in the May issue of APOA Pilot and I'm a little confused about something. The spec sheet on page 73 lists Vx as 51KIAS and it also lists Vs1 as 51KIAS.

This seems to say that the plane achieves best angle of climb when it's stalled.

Now I'm just a student pilot, so maybe there's some subtlety here that I don't get. My instructor hasn't shown me how to do stall climbs yet; maybe I should ask.

I believe the FAA requires a max Vs1 of 45 knots for LSAs, so maybe the 51KIAS number is a typo.

Still, other numbers look sorta funny. For instance, Vso is 42 KIAS but Vr is only 40 KIAS, so you could presumably rotate into a stall, though I'm trying to figure out how a plane can rotate below its stall speed in the first place.

Can someone further my education in aerodynamics by making sense of these numbers for me?

 

[dmspilot]

Stall speeds are power-off. If you've ever done slow flight at MCA you know you can fly slower than the published indicated stall speed. Additionally, stall speed is lower in ground effect. Finally, whether you can rotate or not is a factor of the effectiveness of the elevator and doesn't have much to do with stall speed. With enough elevator and enough prop wash you can rotate at 0.

 

[ircphoenix]

I just read the article about the Remox GXiS in the May issue of APOA Pilot and I'm a little confused about something. The spec sheet on page 73 lists Vx as 51KIAS and it also lists Vs1 as 51KIAS.

This seems to say that the plane achieves best angle of climb when it's stalled.

Now I'm just a student pilot, so maybe there's some subtlety here that I don't get. My instructor hasn't shown me how to do stall climbs yet; maybe I should ask.

I believe the FAA requires a max Vs1 of 45 knots for LSAs, so maybe the 51KIAS number is a typo.

Still, other numbers look sorta funny. For instance, Vso is 42 KIAS but Vr is only 40 KIAS, so you could presumably rotate into a stall, though I'm trying to figure out how a plane can rotate below its stall speed in the first place.

Can someone further my education in aerodynamics by making sense of these numbers for me?

You can rotate well below stall. Depends on the aircraft. Rotate doesn't mean lift off. They happen close together in our small airplanes if you're doing it right, but they're two separate things.

 

[WannFly]

I can technically rotate at 41, published stall speed with flaps is 49. A couple of days back, went up to 9k to test out some theories with AOA. At cruise power, airspeed 44, no flaps, stall horn blazing, some buffet, but no stall, full aeleron and elevator authority. Still confused about all those published numbers, they make my head spin

Sent from my SM-G935V using Tapatalk

 

[Half Fast]

Stall speeds are power-off. If you've ever done slow flight at MCA you know you can fly slower than the published indicated stall speed. Additionally, stall speed is lower in ground effect. Finally, whether you can rotate or not is a factor of the effectiveness of the elevator and doesn't have much to do with stall speed. With enough elevator and enough prop wash you can rotate at 0.

Ah. Got it. Thanks.

I still doubt the 51KIAS stall speed is correct, though. Otherwise, I don't see how it can be an LSA.

The Tecnam Bravo I fly has a Vs1 of 39 and a Vx of 60, so the Remos' numbers looked weird to me.

 

[FastEddieB]

Are you sure that 39k speed isn't Vso (full flaps)? I'd think it would be.

 

[Half Fast]

No

Are you sure that 39k speed isn't Vso (full flaps)? I'd think it would be.

Nope. Vso is 35 KIAS at 40 deg flaps, per the manual.

That's KIAS, not KCAS. At low speeds, KCAS is higher than KIAS, but the graph in the manual doesn't go that low. Interpolating the curve a bit, I suspect that Vso is close to 39 or 40 KCAS.

 

[FastEddieB]

Cool. That's slower than many LSA's.

Vso in the Sky Arrow is about 39k, which is why I asked.

Oh, I see you're saying your CAS might be around the same, so it figures.

Sky Arrow figures, if you're curious:

 

[Half Fast]

Yep, if you look at the KIAS number for full laps in that table, you see it's 38, not too far off the Bravo's 35, and max flaps on the Bravo is 40 degrees compared to 30 for your Arrow.