# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

**Re: 3-Star Fix - "Canned Survival Problem"**

**From:**Mike Burkes

**Date:**2008 Jul 8, 16:46 -0700

Hi GL that is pretty slick and I imagine the user would become accustomed to that type if that was his only exposure. It seems it is an advanced model i.e. I would assume the user has already visualized the wind triangle ala E6b and/or rough sketch and does not wish to fuss with pencil lines. Has anyone had experience with the Jepp Model CB-1(charles bravo dash one)? As always great stuff and thanks much! Mike Burkes On Jun 14, 10:11�pm, "Gary J. LaPook"wrote: > Gary J. LaPook wrote: > > > Gary J. LaPook had written:: > > > "The MB-2A is very similar to the MB-9 pictured here: > > >http://www.rekeninstrumenten.nl/pages%20and%20pictures/12071.jpg > > > except the true airspeed goes up to 1800 knots on the MB-9 while it > > only goes up to 1000 knots on the MB-2A. Since I don't fly planes that > > can exceed 1000 knots I prefer the MB-2A since its more limited speed > > range allows an expanded scale for the range it covers. > > > It is very similar to the Felesenthal PT computer pictured here: > > >http://www.rekeninstrumenten.nl/pages%20and%20pictures/12141.jpg > > > in that each of these computers solve the wind triangle with trig, no > > vector diagram is drawn." > > > Gary adds: > > > In case you were wondering how you can solve the wind triangle with > > trig on the MB-2A without a vector diagram �the answer is simple, the > > law of sines. TAS/sin RWA = WS/sin WCA = GS/sin (RWA +/- WCA). To do > > this on a digital calculator first figure the Relative Wind Angle (the > > angle the wind is coming from compared the true course, WD - TC. Next > > divide the True AirSpeed �by the sine of the RWA �and save that value > > in a memory as you will use this constant twice. �Next divide the Wind > > Speed by this constant, take the inverse sine and you have the Wind > > Correction Angle. Finally add or subtract the WCA from the RWA, > > subtract if the wind is a head wind and add if a tail wind, take the > > sine of this angle and multiply by the constant to give you Ground Speed. > > > The MB-2A does this computation for you. First place the TC arrow on > > the true course on the outermost RED scale and then read the RWA on > > the next inner RED scale lined up with the WD. �This first image shows > > this with the TC of 50, the WD of 100 giving a RWA of 50. > > > Next line up the TAS on the outermost BLACK "miles"scale with the RWA > > on the "wind scale" which is a sine scale. The next image shows 120 > > knots lined up with 50 on the "wind scale." > > > The "constant" mentioned above is found uner the "1" index but you > > make no use of this and you don't even have to notice, the computer > > takes care of it for you. > > > Next look on the "miles" scale for the Wind Speed and take out the WCA > > on the "wind scale." The next image shows a 20 knot WS on the "miles" > > scale lined up with WCA of 7.3� on the "wind scale." > > > Subtracting this 7.3 WCA from the RWA of 50 we then set the cursor on > > 42.7 on the "wind scale" and read out the GS on the Miles scale, 106 > > knots. > > > gl > > >>With the exception of the red numbers on the outside rings, your MB-2A > >>computer looks remarkably similar to the Jeppesen CR series (CR-3, > >>CR-6, etc.) - is it maybe a military version (or an earlier version)of > >>the Jepp one? > > >> Gary LaPook responds: > > >> The MB-2A is very similar to the MB-9 pictured here: > > >>http://www.rekeninstrumenten.nl/pages%20and%20pictures/12071.jpg > > >> except the true airspeed goes up to 1800 knots on the MB-9 while it > >> only goes up to 1000 knots on the MB-2A. Since I don't fly planes > >> that can exceed 1000 knots I prefer the MB-2A since its more limited > >> speed range allows an expanded scale for the range it covers. > > >> It is very similar to the Felesenthal PT computer pictured here: > > >>http://www.rekeninstrumenten.nl/pages%20and%20pictures/12141.jpg > > >> in that each of these computers solve the wind triangle with trig, no > >> vector diagram is drawn. > > >> The Jeppesen CR-3 pictured here: > > >>http://sliderule.mraiow.com/wiki/Jeppesen_CR-3 > > >> uses a diagram on the back to determine wind factors so its method is > >> completely different than the previous computers. �All of these are > >> similar in that they have the standard time-speed-distance scales and > >> they allow for compressibility in computing true airspeed. > > >> The original E-6B pictured here: > > >>http://www.rekeninstrumenten.nl/pages%20and%20pictures/12081.jpg > > >> uses a wind vector diagram on the back and does not allow for > >> compressibility in TAS computations. > > >> gl > > > > �IMGP4734-1.JPG > 186KViewDownload > > �IMGP4735.JPG > 185KViewDownload > > �IMGP4736.JPG > 183KViewDownload > > �IMGP4737.JPG > 184KViewDownload- Hide quoted text - > > - Show quoted text - --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To unsubscribe, email NavList-unsubscribe@fer3.com -~----------~----~----~----~------~----~------~--~---