REFLECTOR: TAS

[Laurence Coen]

Scott,

You just proved my point about "rocket science".  I just ran the problem on my E-6B.  With the wind from 270 at 10 knots and a TAS of 180 knots.  A heading of 270 yields a ground speed of 170 knots.  At a heading of 242 (28 degree error) yields a GS of 171 knots.  A heading of 62 (242-180) gives a GS of 189 knots.  189+171/2=180 knots, the exact TAS.  No this method doesn't work during thunder storms but none of the other methods work either.

Larry Coen
N136LC


From: Scott Derrick 
Sent: Tuesday, July 30, 2013 11:41 AM
To: Velocity Aircraft Owners and Builders list 
Subject: REFLECTOR: TAS


I think an accepted method of determining your TAS is a triangular course of equal length legs(time flown). You probably will not end up at the starting point.

You will need a GPS that allows you to set the current point/waypoint and display how many miles you are from that point in real time
Fly a 360 heading degree, Set point, for a fixed set of minutes, for our airplanes this should be 3-5 minutes.  Record the minutes/miles
Turn 120 degrees right, Set point, fly the same number of minutes.  record minutes/miles
Turn 120 degrees right, Set point, fly the same number if minutes, record minutes/miles

add all the minutes add all the miles, divide minutes into miles, that your miles per minute

multiply by 60 for MPH

If you mean how to convert your current GPS ground speed into TAS, you need the winds, your direction, altitude, barometric pressure and current temperature.  You learned all this when getting your private license. A lot of GPS's will do the conversion for you after you enter the appropriate data.

I have a TAS indicator on my IAS gauge, I set the temp and altitude, and it displays the TAS, this is based on how accurate my  my pitot/static  system is correctly adjusted and how accurate is my OAT sensor.

Scott


-------- Original Message --------
Subject: Re: REFLECTOR: Conversion
From: Laurence Coen <lwcoen at hotmail.com>
To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
Date: 07/30/2013 10:00 AM

  I don't know why folks keep trying to turn something simple into rocket science.  If you fly directly into the wind, record your ground speed (GPS), then fly a 180 course and record your GPS speed and average the numbers (S1+S2)/2 you will know your TAS +- one knot.  To answer your next question as to how do you know when your flying directly into the wind.  Start with the wind sock as a starting point.  Fly 10 degrees left of that and note GPS speed.  Continue turning right in 5 degree steps for 3 more readings.  The lowest GPS reading is the heading closest to directly into the wind.  Fly 180 from that heading and you're done.  It turns out that with a 10 knot wind and you get within 10 degrees of the true wind heading the error will be less than one knot.

  Larry Coen
  N136LC


  From: Gordon Putney 
  Sent: Monday, July 29, 2013 1:28 PM
  To: Velocity Aircraft Owners and Builders list 
  Subject: REFLECTOR: Conversion


  Will someone please point me towards the formula converting ground speeds in each of four directions to actual speed.
  Thanks,
  Gordon Putney


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