I should know this...

[jp]

For the sake of safety should we consider maneuvering speed to be an IAS or a TAS? If we consider it a TAS its IAS should be reduced with altitude I suppose.

[jfitch]

On Sunday, August 13, 2023 at 8:44:20 PM UTC-7, jp wrote:
> For the sake of safety should we consider maneuvering speed to be an IAS or a TAS? If we consider it a TAS its IAS should be reduced with altitude I suppose.

The sailplane mostly sees IAS and knows nothing about TAS. For maneuvering speed, stall speed, flap speed, etc., this should be correct. I say "mostly" because some things, like flutter speed and there for Vne are not quite that simple.

The reason is that all of the primary characteristics of the wing are proportional to dynamic pressure, and this is read directly by the air speed indicator as IAS.

[Eric Greenwell]

On Sunday, August 13, 2023 at 8:44:20 PM UTC-7, jp wrote:

> For the sake of safety should we consider maneuvering speed to be an IAS or a TAS? If we consider it a TAS its IAS should be reduced with altitude I suppose.

For the sake of safety, follow the speed requirements in your aircraft's flight manual. They will match what Jon Fitch wrote, with all but Vne being in IAS. Your aircraft should have a placard showing the IAS value of Vne at different altitudes; typically, it's given as a single IAS value up to 10,000 feet, but as a diminishing IAS value above that.

[jp]

Thank you for your replies. Makes sense. Also, I just found a discussion of Va that says it is a calibrated airspeed. Fits right in. I'm pretty conservative so I might still treat Va as a TAS and so reduce its IAS by about 2% per 1000' but it's good to know more about Va.

JP