Overspeed Needle

[Jack_C 1]

I finally found a YouTube video of a c90b that shows the barber pole decreasing.

[Guest bstolle]

SO, the pole SHOULD move then?

 

Yes

[Guest BeaverDriver]

Ahh ok. Cool :). I'm glad I could clear this up for you guys. If there's anything else you need to know, just ask. What I don't know (which is almost everything), I'll make up (as always) . OK, obviously I'm just kidding in taking the credit, of course. In all seriousness, this has been a neat and very interesting discussion, not to mention productive. Good job guys B) . Nice to see a good collaboration that produces results.

[rossdh 0]

http://www.aopa.org/pilot/features/2003/feat0305.html

 

Just found that. It quotes the max Mach number to be 0.46. The .cfg states it as 0.4...

[haskell 298]

Confirming: I was descending through 20,000 and got overspeed warning at 200 indicated. Well below the "red line"

[dbw1 444]

The barber pole does move. Down low vne is 226 kts and in the pic you can see it is lower at altitude - in this case @ 21000 feet. In the one I fly normal cruise depending on wieght, OAT and altitude is in the 230 -240 knotsd true range.

Dave

[Jason290 0]

If anybody here flies a real-life King Air C90B, it would be interesting to hear how the overspeed barber pole moves when altitude increases.  In other sims I have flow, it increases as altitude increases, which makes sense because the air is getting thinner.  But in the Carenado sim, it decreases as altitude increases, which makes no sense to me.

 

 

 

 

[WarpD 824]

If anybody here flies a real-life King Air C90B, it would be interesting to hear how the overspeed barber pole moves when altitude increases.  In other sims I have flow, it increases as altitude increases, which makes sense because the air is getting thinner.  But in the Carenado sim, it decreases as altitude increases, which makes no sense to me.

 

If you see it increasing, that makes no sense at all.  As air gets thinner, indicated airspeed drops due to lower pressure.  Since indicated drops, you should see the barber pole drop as well.

 

I have no idea why any other sims would model it as increasing... that really doesn't make sense.

[Jason290 0]

If you see it increasing, that makes no sense at all.  As air gets thinner, indicated airspeed drops due to lower pressure.  Since indicated drops, you should see the barber pole drop as well.

 

I have no idea why any other sims would model it as increasing... that really doesn't make sense.

Forget the calculus for a moment and think about it in terms of what an airspeed indicator's job is.  As I see it, the two most important jobs it does are, (1) at the low end--help you to keep from stalling, and (2) at the high end--help you to keep from ripping the wings off your aircraft.  So in the latter case, what it's really telling you is how much stress there is on the airframe!

 

At any given speed, the thinner the air, the less stress there is on the airframe; and for that reason, the higher the allowable max speed.

 

Doesn't that make logical sense?

[WarpD 824]

No... and you've got it all completely wrong.  It's telling you what indicated airspeed limit you have.  The barber pole indicates IAS which changes based on air pressure from altitude.

 

For aircraft that will climb high enough for it to matter, there is a Vmo value which is the only accurate speed at any altitude.