@Vulture et al. Question to the Real World Pilots out there: Are V-speeds refering to true airspeed

@Vulture et al. Question to the Real World Pilots out there: Are V-speeds refering to true airspeed or indicated airspeed (ktas/kias)? Reason for question - the manual for the MSFS Black Square King Air states the following:

HiobOP•9/18/24, 9:57 AM

- Maximum Cruising Speed 312 ktas

HiobOP•9/18/24, 9:58 AM

- Economy Cruising Speed 234 ktas

HiobOP•9/18/24, 9:58 AM

BUT V(ne) 263 kts?!

HiobOP•9/18/24, 10:00 AM

I can't make sense of this (assuming the values are correct that is)

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(41F) RAFAIR Dave H•9/18/24, 10:46 AM

VNE, the redline on the airspeed indicator, is an indicated airspeed, but the critical flutter speed may be a true airspeed. So the margin separating VNE from the critical flutter speed gets smaller as you gain altitude.

((41F) RAFAIR Dave H VNE, the redline on the airspeed indicator, is an indicated airspeed, but the cr...

HiobOP•9/18/24, 10:51 AM

That's what I figured. Are all the other V's (flap retraction, gear retraction, turbulence penetration etc) also indicated Airspeeds then I assume? (I'm aware that the difference is marginal close to the ground)

Arno•9/18/24, 1:32 PM

Yes, they are usually aerodynamic speeds, and these are governed by the IAS. TAS has no bearing on aerodynamics (except mach effects)

mechsicko•9/18/24, 3:00 PM

VNE is based on true airspeed. It's usually determined by the flutter speed of the wings or some other lifting body. This leads to a service ceiling in ac called the 'coffin corner', since you can't fly slower than stall or faster than VNE and at some altitude those line converge since stall is airspeed and VNE is true

mechsicko•9/18/24, 3:02 PM

..For ac not limited by their propulsion that is

Mmechsicko VNE is based on true airspeed. It's usually determined by the flutter speed of t...

HiobOP•9/18/24, 3:02 PM

That's the opposite of what @(41F) Dave H said and would render the given values in the manual without any sense.

HiobOP•9/18/24, 3:03 PM

Again, I have no pilot training, just from logic I would assume that IAS makes more sense for a Vne

mechsicko•9/18/24, 3:11 PM

Aeroelastic flutter is a momentum thing so is based off TAS. For ac not limited by their engines (gliders for instance) you have to continually reduce IAS to keep from ripping off the wings as you increase in altitude.

AC like the U2/TR1 are examples of this regime of flying where at operational cieling they are teetering between stalling and ripping off the wings due to these converging lines on the flight polar. Can't fly slower than stall, IAS, but can't exceed TAS VNE w/out losing the craft

Mmechsicko Aeroelastic flutter is a momentum thing so is based off TAS. For ac not limited ...

HiobOP•9/18/24, 3:19 PM

Thank you. I appreciate the explanation. However that doesn't help me for my specific question from above.

My question - more precisely - was, how can it be that the Vne is lower than the max. cruise speed, with the latter given in TAS and the former not specified?

mechsicko•9/18/24, 3:21 PM

Missed the first question.. no idea but it sounds wrong for VNE to be lower than any other recommended speed to fly

j9murphy•9/18/24, 3:23 PM

https://tailspinstales.blogspot.com/2009/11/vne-ias-tas-and-bvds.html#:~:text=Never%20Exceed%20Speed%20(Vne)%2C,an%20effect%20on%20your%20BVDs.

• Vne, IAS, TAS and BVDs

Flying adventures, aviation history, and aircraft flights written by those who experienced them first-hand.

Mmechsicko Missed the first question.. no idea but it sounds wrong for VNE to be lower tha...

HiobOP•9/18/24, 3:23 PM

That would only make sense, if the Vne is given in IAS

(

(41F) RAFAIR Dave H•9/18/24, 3:32 PM

VNE is definitely ias as it’s the redline on the speed indicator which measures indicated airspeed , military ones also convert this to mach numbers as speed gets close to mach as mach is based on density altitude as well as true airspeed

mechsicko•9/18/24, 3:45 PM

I know what the redline on my airspeed indicator means and I also know that only applies to standard atmospheric conditions. The higher I go the more math is involved to figure out what my current IAS should read to keep from exceeding VNE. Many planes have a placard to remind pilots to take density altitude into account for this reason

HHiob That would only make sense, if the Vne is given in IAS

mechsicko•9/18/24, 3:47 PM

I think this might? answer your initial question https://aviation.stackexchange.com/questions/79284/how-can-the-cruise-speed-be-larger-than-vne

Aviation Stack Exchange

How can the cruise speed be larger than Vne?

I recently read the POH for a M20V, the advertising for this aircraft states that the top speed is 242 KIAS. The POH gives the Vne at 196/195 KCAL/KIAS.
I have found a similar discrepancy, the Vl3 ...

mechsicko•9/18/24, 4:09 PM

This being a complicated subject, there are probably a few right ansers because ac are so different from one to the next.

HiobOP•9/18/24, 4:19 PM

Yeah. it dawns on me. What is so irritating to me is, that it is stated that the Vne needs to reduce with altitude. Which is exactly what IAS does inherently, but the key seems to be that Vne decreases more than IAS and therefore the Vne(ias) has to decrease even more than that……
my head is starting to hurt…..

buzzbomb•9/18/24, 4:38 PM

V speeds are aways given in KIAS aka indicated. Cruise speed is not a "V" speed per se and will often be expressed in Indicated or True depending on its intended use. You fly Indicated airspeed but you flight plan with true airspeed. If you look at the power charts for the King Air you will see torque, rpm, fuel flow, KIAS and KTAS for different pressure altitudes and temperatures. Now how VNE is determined depends on how the aircraft is certificated as high altitude and high airspeed aircraft use different formulas to determine it. This can lead to some strange results. Take the Duke and the turbine Duke for example. The VNE on the Turbine Duke is lower than the Piston Duke since it flies higher and was certificated under different standards requiring a different formula for VNE determination. essentially once you get over 25k VMO/MMO become dominate. I read the exact details how this is done a long time ago but cannot find the reference

Arno•9/18/24, 4:38 PM

I have never heard of Vne being dependent on altitude/TAS. It is a structural speed that depends on IAS. Your airplane will only be affected by the TAS when getting close to Mach 1, where the air stops being compressible. I don't think flutter characteristics change significantly with TAS/Altitude to warrant a different Vne. What is coffins corner is where you can't go faster in an airliner due to mach buffet , but can't go slower due to your AOA, minimum stall speed. That's where any turbulence will force you to dive down, which is not a good thing

Arno•9/18/24, 4:40 PM

The cruise speeds are in TAS to advertise how fast you can get from A to B in an aircraft. This is confusing, because your optimum IAS when flying the thing will be lower.

AArno I have never heard of Vne being dependent on altitude/TAS. It is a structural sp...

buzzbomb•9/18/24, 6:01 PM

"I don't think flutter characteristics change significantly with TAS/Altitude to warrant a different Vne" .. It depends on the type of aircraft and how its certificated. for most light GA its essentially not an issue. BUT even a light GA aircraft that is Turbo-normalized that equation changes. For example a SR-22t can operate up to FL250. It has a fixed VNE (205KIAS) up to 17500 and a linearly decreasing one that is reduced to 175KIAS at FL250. This isnt a direct result of structural loads but is a result of reduced flutter/aeroelastic margin due to higher TAS at a given indicated airspeed in the flight levels.

Bbuzzbomb "I don't think flutter characteristics change significantly with TAS/Altitude to...

mechsicko•9/18/24, 6:31 PM

The only reason it’s not an issue with most light (powered) ga is their engines service ceiling are too low to matter. In gliders it’s a serious consideration though for high altitude/wave flying where you can get to fl400 and beyond. Perlman 1’s (Perlman Project, high alt glider research) coffin corner is about 60k ft as it’s just a modified DG505m. Perlman 2 which is purpose built for this can safely reach fl900, higher than the U2.

mechsicko•9/18/24, 6:35 PM

The convergence of flutter speed based on tas and the stall speed in ias is what defines both of their envelopes

HHiob @Vulture et al. Question to the Real World Pilots out there: Are V-speeds refer...

Vulture•9/18/24, 6:37 PM

V speeds are in IAS, but at higher altitudes there are often speeds that are TAS limited (often due to flutter or mach effects). For example, even in my LS6 glider, Vne decreases with altitude, and this is shown on the airspeed indicator with several red lines below the Vne mark, with an altitude next to it.

HiobOP•9/18/24, 6:43 PM

Thanks y’all. I think I got it now!

Vulture•9/18/24, 6:45 PM

If you zoom in, you can see that at 19700', Vne is down to 118 KIAS. Trust me, an LS6 can hit 118 KIAS easily cruising under a western clould street - BTDT over the Grand Canyon at 17999' a few times. So you have to keep that in mind when blasting along fat, dumb, and happy; because if you get sucked into a Cu, getting out by diving may not be an option, and opening the spoilers at VNE is not a really good idea...and without gyros, well, you know what happens next.

HiobOP•9/18/24, 6:50 PM

I guess operating at the edge of the envelope is always risky business

Vulture•9/18/24, 6:51 PM

For those of you not familiar with racing gliders - you can get to redline with an easy push on the stick and about a 5 degree dive for less than a thousand feet. Back when low passes were common, a normal pattern was a wormburning Vne pass across the field dumping water ballast then pitching up to a closed pattern. Or sometimes a second Vne pass...not that I would EVER do anything that fun

Vulture•9/18/24, 6:55 PM

Vulture•9/18/24, 6:57 PM

Different subject: has anyone use their Rhino with AFS 4?

buzzbomb•9/18/24, 7:13 PM

my Rhino was just delivered!!!

HHiob Thanks y’all. I think I got it now! 💪

buzzbomb•9/18/24, 7:14 PM

its a tricky subject that is overtly colored by ones [often limited] experiences. Even in most pilot forums talking about VNE triggers a ton of discord

Arno•9/18/24, 7:14 PM

LS6 is nice. But I fly gliders too, never seen a speedo with more than one Vne on it.

buzzbomb•9/18/24, 7:15 PM

ive been meaning to get my glider rating for years. I live within an hour of two glider ports, i should finally give it a go

Arno•9/18/24, 7:16 PM

certainly, it is much more satisfying to stay up there by skill rather than by fuel. In europe, gliding tends to be cheaper than powered flying due to winch launching and clubs sharing the investment.

Arno•9/18/24, 7:18 PM

And it will train natural stick and rudder skills, you'll fly planes like riding a bike.

buzzbomb•9/18/24, 7:19 PM

i started in Utralights when i was a kid and moved to GA when i was 19.

AArno LS6 is nice. But I fly gliders too, never seen a speedo with more than one Vne o...

mechsicko•9/18/24, 10:10 PM

That info is usually in the factory fight manual

mechsicko•9/18/24, 10:10 PM

…as opposed to the panel

RReed I started with 11 degree throw limiter for helos and now I’m running a 10-8 thro...

buzzbomb•9/19/24, 12:00 AM

Is there a template or cad for the general throw limiter dimensions that you used? Im thinking i will need one more custom than the 11 degree

Bbuzzbomb Is there a template or cad for the general throw limiter dimensions that you use...

TheAmazinGreat•9/19/24, 12:21 AM

https://discord.com/channels/965234441511383080/1092338475795238962/1092338475795238962

buzzbomb•9/19/24, 12:31 AM

thanks... Search for Throw limiter and nothing came up

Bbuzzbomb Is there a template or cad for the general throw limiter dimensions that you use...

Reed•9/19/24, 1:17 AM

He linked the correct thread. I’m installing a new limiter of 9,8 this week.

buzzbomb•9/19/24, 1:57 AM

yeah i already checked it out..need to make some measurements and then ill print one. I have the 11 to try first but im sure i want less aileron deflection than pitch

Khangirey•9/19/24, 6:00 AM

Anyone interested in my Rhino Monstertech Mount plate? I upgraded to a sim rig so I don't need it anymore

102nd-YU-devill•9/19/24, 8:08 PM

Hi all, I am pretty my question was already discussed somewhere but i have no idea how to find it. The question is: why does the stick stiffen under Gs and not under dynamic pressure (airspeed) in Il2GB? Does IL2 not provide speed as telemetry?

@Vulture et al. Question to the Real World Pilots out there: Are V-speeds refering to true airspeed

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