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  #1  
Old 01-24-2016, 02:02 PM
TLYNCH TLYNCH is offline
 
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Default EAS? Anyone know how to calculate EAS: Equivalent Air

I found the formula: EAS (r0/r) 1/2
Reference page 11 in the FAR.
So far have learned that r is air density.
The "0" cannot be zero ?..

Is there some math expert out there?

Tim
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  #2  
Old 01-24-2016, 02:43 PM
David Paule David Paule is offline
 
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EAS is Equivalent Air Speed.

Here's the Wikipedia link.

Dave
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  #3  
Old 01-24-2016, 02:58 PM
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The terminology r0 in your formula is read as "r sub zero."

"r" in this case substitutes for rho which is density. "r sub zero" is standard sea level density. "r" is the density at the measured conditions.

The "1/2" is indicating "to the one-half power" which is the same as the square root.

Equivalent airspeed is defined mathematically as the True Airspeed multiplied by the square root of the ratio of the measured air density to the density at standard conditions.

So

EAS = TAS * SQRT ( r/r0 )
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Old 01-24-2016, 03:04 PM
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Tim, the zero is called a "subscript" in math. You will notice that it is written slightly below the line. In this case it represents the density of air in standard conditions at sea level. So it is a reference value and when the ratio of (r/r0) is written it is the ratio of the air density (r) to the reference air density (r0). [You wrote it as r0/r but I'm thinking it should be r/r0, but I could be wrong.] The term r0 is pronounced "r sub zero."

Usually, in engineering texts, the Greek letter rho (looks kinda like a "p") is used to express air density rather than the letter "r."

You didn't ask about the 1/2 but in the equation you reference, the 1/2 is an exponent of the ratio within the parentheses. An exponent of 1/2 is another way to say "the square root of."

Tim, I hate to dampen your enthusiasm, but when you fly your RV-12, you will not think about EAS. You may run across it on an FAA exam, but there are more challenging things to learn when you become a pilot.

If you can play a violin, I believe you can fly an RV-12.
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Old 01-24-2016, 08:40 PM
TLYNCH TLYNCH is offline
 
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Default EAS. Thank you!

Wow....thank you all....david, paul, r boy et. al.

I'm taking the practical test next and trying to anticipate the oral horror. One examiner gives 5 hour Orals.

And we have a Neil Armstrong graduate!!!

Thank you all for the good advice.....where else but Vans Air Force.

It was John Palese who cited the air density as rho.....though my study of atic Greek gave away the RHO r.

Tim
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Old 01-24-2016, 09:27 PM
TLYNCH TLYNCH is offline
 
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Thank you Carl.....yes....p. 9:
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Old 02-09-2016, 04:14 PM
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Question Test Results?

So, Tim, how did you do on the test?
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  #8  
Old 02-09-2016, 05:54 PM
TLYNCH TLYNCH is offline
 
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Default Test.... EAS question

Don
We scheduled 3 dates for the practical test but bad weather. Just as well...will give more time to study for the oral, learn about obscure trick questions like adiabetic compression. ......and get more hours when the weather improves. We will try again in April. Thanks for asking Don.

Tim
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  #9  
Old 02-11-2016, 06:53 PM
RFSchaller RFSchaller is offline
 
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Why would anyone care about equivalent airspeed for the RV-12 envelope? For that matter, why care about anything but indicated airspeed when you're in the air in an RV-12?
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  #10  
Old 02-11-2016, 09:48 PM
TLYNCH TLYNCH is offline
 
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Default EAS IAS TAS .... All virtually the same ?

Good question Rich. Reason is I was warned that one of the examiners up here gives an oral for the practical test 5 hrs. long. At my age, 70.... I can't afford to fail....

I've wondered as you suggest about using anything but IAS ....especially since CAS & IAS are identical per the POH for the RV12.

Maybe the only real concern would be TAS adjusted for varying altitude/temp ?

I've wondered about other calculations like isogonic lines with similar interest....what difference do isogonics make anyway? ...we live in Wisconsin, a virtual AGONIC location. Plus 1 or 2 around here means lpassing an airport on the left vs. right side of the plane!

Sure hope I pass this exam. Any suggestions welcome.

Tim
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