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So if someone put a small turbine on a patrol like the rv 10 has how fast could it fly ? Is it a structure issue or a control issue at a higher speed ?
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Speed has little to do with horsepower and most to do with drag. I'm sure you'd gain a good many knots if you cruised in the upper teens on o2, but down low where these airplanes normally live it'd be a rather small cruise increase and a crap ton more fuel burn. -
I sat right seat in a C206 Amphib with the Soloy turbine conversion. I could not believe the acceleration and climb angle! When asked about speed, the owner explained that the original VNE still applied, so as long as it wasn't 'indicating' past red line - you were good. Might be good up really high, but I sure wouldn't want to be at VNE down low in the bumps.
It WOULD be fun to have that takeoff thrust and beta, though!
Bill
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I am getting ready to have the arcs on my airspeed indicator labeled and I am not seeing any full definitions in the forum. I have the white arc as 41 to 100 mph, max flap speed. The green arc is 48 mph to Vno which I haven't seen defined. The Yellow arc would go from Vno to Vne, the never exceed speed. Anyone have suggests for these missing numbers?Comment
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Bruce, your question was on my to-do list and I'm sorry it has taken so long to get back to you.Originally posted by spinningwrench View Post
To find Vne, we need to ask Bob. If you get through please feel free to report back. I tried calling just now but he is busy. The Vne might be based on structural loads or something else like flutter considerations.
The yellow arc is a little harder. When I think about defining airspeed limits, I think about the V-g (V-n) diagram. Rod Machado wrote a nice series of articles about them with the first one being here:
The link at the bottom is broken but here is a link to the second part, which is the part that gets to the yellow arc:
There is a very good article here:
The Vans article is coming from the perspective of not oversizing engines, because routinely operating too fast reduces the margin. There's no way to know how strong of a gust you may encounter, so the closer you are to the edge, the more risk you take. The longer you fly at speeds approaching the edge, the more times you roll the dice.
Skip Smith wrote a very good article in the January 2006 issue of Sport Aviation, which you can search for on the EAA archives.
Part of the problem with the yellow arc is that you'll need to establish some expectations and assumptions. You can decide on how much of a gust you want to be able to withstand, and at what weight. It is not possible to say "here is a single speed" at which the airplane is indestructible. Instead we have to decide on what is an acceptable level of gust and risk, which is a policy choice rather than an engineering choice. If you want to assume current TC standards, they are designed to handle a gust of + /- 50 feet per second at cruise speed and a + /- 25 fps gust at design dive speed. More here:
If you want to get nerdy about it 25.335 gives the formula for calculating some of these things. Naturally we aren't flying under part 25 with our e-a/b airworthiness certificates, but those numbers were probably arrived upon with some sound thinking.
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I just dealt with this as Dynon is pre-programming my HDX and asked for speeds
I guessed but called Mark to confirm, I was very close but tweaked them a bit to be on the safe side
Companion so very similar to the Patrol
Vne 165
Vno 120 ( I was gonna go with 125 but Mark’s tone made me lower it to 120)
Vfe 100
Vso 38
Vs1 46
Hope this helpsN678C
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I ran some numbers based on CS-VLA 355 (I think it is the same formula as in Part 25.335 and CS-23-335). You could say I fell into a hole. The Vc/Vno comes out as 110 KIAS (There are a lot of conditionals in the regs and I may not have considered them all). The regs say this formula should be used unless some other more appropriate rationale can be used. Also I am missing some definite data about the airfoil. The "a" variable is the slope of the lift curve (change of lift per one radian of AoA change). Supposedly it's a number between 4 and 6, the lower numbers corresponding more to high-lift airfoils. I made a wild guess with 4.4. If anybody finds a lift curve for the Patrol Ribblet airfoil we could make this more precise.
Here is my python code if you want to play around a bit. It's actually quite interesting to see how different wing loadings, limit load factors, and air densities affect the Vc/Vno. I am also pretty sure the convention is to calculate Vc with MTOW but I am not 100% sure.
# Calculate design cruise speed Vc
# For the Bearhawk Patrol this is also the Vno, Vra
# Formula from CS-VLA 341 Gust load factors
# Formula also in CS-23.341 Gust load factors
n = 4.4 # max loadfactor, utility 4.4, normal 3.8
g = 9.81 # gravity
wingspan = 10 # wing span [m] including fuselage section
mac = 1.6 # mean aerodynamic chord [m]
mass = 907 # MTOM [kg]
wingloading = mass/(wingspan*mac)
rho_0 = 1.225 # density of air at sea level [kg/m^3]
rho = rho_0 # density of air at altitude considered
a = 4.44 # slope of lift curve of airfoil [lift increase per one radians]
Ca = mac
mu_g = 2 * wingloading / (rho * Ca)
K_g = 0.88 * mu_g / (5.3 + mu_g)
Ude = 15.24 # gusts [m/s] - CS-VLA, CS-23 for Vc
# Ude = 13.7 # gusts [m/s] - FAA Part 23 within 50-125 kt
# Ude = 7.62 # gusts [m/s] - CS-VLA for Vd
Vc = ((n-1) * 2 * g * wingloading) / (rho_0 * a * K_g * Ude)
Vc_knots = Vc * 1.94384
print(Vc_knots)
You can run it in a browser through this link.
Originally posted by jaredyates View Post
Bruce, your question was on my to-do list and I'm sorry it has taken so long to get back to you.
To find Vne, we need to ask Bob. If you get through please feel free to report back. I tried calling just now but he is busy. The Vne might be based on structural loads or something else like flutter considerations.
The yellow arc is a little harder. When I think about defining airspeed limits, I think about the V-g (V-n) diagram. Rod Machado wrote a nice series of articles about them with the first one being here:
The link at the bottom is broken but here is a link to the second part, which is the part that gets to the yellow arc:
There is a very good article here:
The Vans article is coming from the perspective of not oversizing engines, because routinely operating too fast reduces the margin. There's no way to know how strong of a gust you may encounter, so the closer you are to the edge, the more risk you take. The longer you fly at speeds approaching the edge, the more times you roll the dice.
Skip Smith wrote a very good article in the January 2006 issue of Sport Aviation, which you can search for on the EAA archives.
Part of the problem with the yellow arc is that you'll need to establish some expectations and assumptions. You can decide on how much of a gust you want to be able to withstand, and at what weight. It is not possible to say "here is a single speed" at which the airplane is indestructible. Instead we have to decide on what is an acceptable level of gust and risk, which is a policy choice rather than an engineering choice. If you want to assume current TC standards, they are designed to handle a gust of + /- 50 feet per second at cruise speed and a + /- 25 fps gust at design dive speed. More here:
If you want to get nerdy about it 25.335 gives the formula for calculating some of these things. Naturally we aren't flying under part 25 with our e-a/b airworthiness certificates, but those numbers were probably arrived upon with some sound thinking.
Last edited by noema; 11-29-2023, 02:59 PM.Bearhawk "XHawk" Patrol, O-360, Trailblazer 80", tubeless 26" Goodyears, Stewart Systems. See XHawk Build Log.Comment
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