Canard as Elevator

[LargePrime]

It should be noted that flutter is not simply related to IAS (ie you can't take a Cozy to 48,000 feet with a turbine and safely cruise at 390 knots with an IAS of 200). This mach .67 cruise would indeed be experimental.

 

390 MPH at 48L feet is not .67 mach if we define mach (as we should) as the "speed of sound". It would be less than .3.

 

Please post a referance that states the IAS is not a (THE) first order variable in flutter. Very curious about that.

 

Thank you

[Tyson]

Originally posted by LargePrime

390 MPH at 48L feet is not .67 mach if we define mach (as we should) as the "speed of sound". It would be less than .3.

 

Please post a referance that states the IAS is not a (THE) first order variable in flutter. Very curious about that.

 

Thank you

 

1) "Speed of sound" = 38.967854*sqrt(T+273.15)

where T is the OAT in celsius. TAS is true airspeed in knots.

At 48,000 T usually = -56 celcius

Plugged and chugged CS = 574 knots at 48,000

 

2) IAS of 200 knots at 48,000 ~ TAS of 392 knots.

 

3) Mach Number (M) = TAS/CS

392 knots (plane) / 574 (sound) = Mach .68

 

Above text copied from the web.

The calculators I used for these numbers are (formulas are crude):

http://www.csgnetwork.com/tasinfocalc.html

http://www.csgnetwork.com/machonecalc.html

 

What do you mean "how we should" define the speed of sound?

 

As for the flutter issue, check my message under Marc's newer speed thread.

[LargePrime]

http://www.aerospaceweb.org/question/atmosphere/q0112.shtml

 

Very interesting read.

 

I am guessing that 38.967854*sqrt(T+273.15) is a simplification? I would assume pressure would be a factor in this function at some point.

Notice how the speed decreases to 36K then stays constant to 66K then increases to 154K

 

Wild.

 

And thanks again Tyson

 

PS

I misquoted your KTS as MPH, which is fair as you mistook MPH for KTS.

But .3 was still incorrect.