A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Regarding fix bearings
From: Mike Burkes
Date: 2008 Dec 21, 17:57 -0800
From: Mike Burkes
Date: 2008 Dec 21, 17:57 -0800
Hey GL, Mike Burkes here I would love to! I had a 1962 C-172 based at El Monte(EMT). I have a Private Pilot with Instrument Rating and 1000+ hrs total time but am not current. Did your C-172 have an astrodome? Just make sure a B-747 does not appear in your bubble or it will burst more than your bubble ha! But seriously that sounds like super great stuff! Mike Burkes On Dec 21, 2:34�pm, "Gary J. LaPook"
wrote: > Not just the military teaches this technique Greg. I have attached an > illustration from the 1998 edition of the Jeppesen Instrument Commercial > Manual which shows the same thing. Note that this page also illustrates > the "double the angle on the bow" technique which works real well in > aircraft. I have been a CFI, airplane, instrument and multiengine since > 1972 and have taught this method. > > I fly out of Santa Paula and CMA and I used to flight instruct at Navy > Point Mugu. Are you still flying? About a month ago I had to fly on > business down to Corona from SZP. I rented a Cessna 172 with an > autopilot and shot two sunlines on the way with my MA-2. When checked > against the GPS one line was off by three NM and the other by five NM. > Want to go flying sometime and shoot some sunlines? > > gl > > > > Greg R. wrote: > > --- On Sun, 12/21/08, Gary J. LaPook wrote: > > >> Another method is taught to every instrument rated pilot. > >> With the station near the wing tip (near the beam if talking about > >> ships) measure the time it takes for a certain number of degrees of > >> bearing change in seconds. Then divide the seconds by the number of > >> degrees of bearing change and the result is the distance to the station > >> in minutes. > > > Seems like I remember reading about that method in my instrument ground school books way back when (mid-70s), but I can't recall ever using it in practice (we mostly used DME back then, and GPS these days). I think you got some/most/all of your flight training in the military (?), so that curriculum might have been different from what us civilians were taught. > > > Of course, alternate methods of navigation are always good to have in your back pocket, and I wouldn't sell it short by any means. > > > -- > > GregR > > > --- On Sun, 12/21/08, Gary J. LaPook wrote: > > >> From: Gary J. LaPook > >> Subject: [NavList 6784] Re: Regarding fix bearings > >> To: NavList@fer3.com, "Beverley Maxwell" > >> Date: Sunday, December 21, 2008, 1:59 AM > >> It looks like the classic "double the angle on the > >> bow" technique. I am > >> attaching Dutton's explanation. > > >> Another method is taught to every instrument rated pilot. > >> With the > >> station near the wing tip (near the beam if talking about > >> ships) measure > >> the time it takes for a certain number of degrees of > >> bearing change in > >> seconds. Then divide the seconds by the number of degrees > >> of bearing > >> change and the result is the distance to the station in > >> minutes. This > >> works because the tangent of �one degree is approximately > >> equal to 1/60 > >> and this approximation holds true for small angles. > >> The actual formula is (time/degrees of bearing change) x 60 > >> = time to > >> the station. By measuring the time in seconds the > >> multiplication by 60 > >> is accomplished automatically when you take the result in > >> minutes. The > >> formula can also be worked to find distance. Simply measure > >> the time in > >> minutes and multiply by your speed in knot, then divide by > >> the number of > >> degrees of bearing change to give you your distance off in > >> nautical > >> miles. Measuring in minutes and multiplying by your speed > >> takes care of > >> the internal multiplying �by 60. In flying the bearings are > >> measured > >> with and ADF or VOR but the same technique works with > >> visual bearings. > > >> A simple example. Say it takes 120 seconds for the bearing > >> to change 10 > >> degrees. 120/10 = 12 minutes to the station. The same > >> example, 120 knots > >> times 2 minutes divided by 10 puts you 24 NM from the > >> station. This is > >> the same result as multiplying the 120 knot speed by 12 > >> minutes divided > >> by 60 minutes per hour. I have attached an excerpt from FM > >> 1-240 that > >> illustrates this. > > >> gl > > >> George Huxtable wrote: > > >>> in...@yahoo.com, or A-08, wrote the posting copied > > >> below. > > >>> That idea sounds original, simple, and interesting. > > >>> Tell us more, A-08. > > >>> George. > > >>> contact George Huxtable, at �geo...@hux.me.uk > >>> or at +44 1865 820222 (from UK, 01865 820222) > >>> or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 > > >> 5HX, UK. > > >>> ----- Original Message ----- > >>> From: > >>> To: > >>> Sent: Saturday, December 20, 2008 2:12 AM > >>> Subject: [NavList 6773] Regarding fix bearings > > >>> | > >>> | Regarding fix bearings: A convenient practice of > > >> taking two bearings at > > >>> one landmark is to take the first bearing at 45 deg, > > >> then second bearing is > > >>> taken off beam (90 deg). �In this case distance off > > >> beam is equal distance > > >>> traveled. > >>> | There are also few so-called "magic" > > >> angles which play the same trick: > > >>> upon using them distance travelled is equal distance > > >> off. > > >>> | > >>> | I wrote a formula which permits for the first > > >> bearing chose any angle you > > >>> want and then calculate the angle for the second > > >> bearing which, as a result, > > >>> equals distance travelled to distance off. > >>> | > >>> | I think it gives some flexibility in bearing taking > > >> and especially in > > >>> calculating distance off. > >>> | > >>> | Respectfully, > >>> | > >>> | A-08 > >>> | > >>> | > >>> | ------------------------------------------ > >>> | [Sent from archive by: inuik-AT-yahoo.com] > > > > �jepp2-66.jpg > 558KViewDownload- Hide quoted text - > > - Show quoted text - --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To unsubscribe, email NavListfirstname.lastname@example.org -~----------~----~----~----~------~----~------~--~---