Radio-Navigation

<body topmargin=0 leftmargin=0 marginheight=0 marginwidth=0> <table cellpadding=0 cellspacing=0 border=0 height="100%"><tr> <td valign="top" colspan=2 height=85 BGCOLOR="#0066FF" TEXT="#080000"> <div> <FONT SIZE="6" COLOR="#FFFFFF" FACE="Arial" ><B>ACA</B></FONT><FONT SIZE="5" COLOR="#FFFFFF" FACE="Arial" ><B>     </B></FONT><FONT SIZE="1" COLOR="#FFFFFF" FACE="Arial" ><B>|          </B></FONT>Retour à: <A HREF="index.htm" TARGET="_top" TITLE="ACA"><U>Page d'accueil</U></A>         <B>|         </B><A HREF="mailto:acacourrier@acabidjan.com" TARGET="_top" TITLE="mailto:acacourrier@acabidjan.com"><U>Ecrire à l'ACA</U></A></div> <div> Retour à:  <A HREF="id22.htm" TARGET="_top" TITLE="La boîte à outils"><U>La boîte à outils</U></A></div> <div> </div> </td> </tr><tr> <td valign="top" width=17,5% BGCOLOR="#FFFFFF" TEXT="#080000" bgproperties="fixed" background="2a520bc3.jpg"> <div> <B><IMG SRC="4f36f310.gif" border=0 width="111" height="49" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></B></div> <bR> <div> <A HREF="id264.htm" TARGET="_top" TITLE="NDB"><U>NDB</U></A></div> <div> <A HREF="id265.htm" TARGET="_top" TITLE="VOR"><U>VOR</U></A></div> <div> <A HREF="id266.htm" TARGET="_top" TITLE="ILS"><U>ILS</U></A></div> <div> <A HREF="id268.htm" TARGET="_top" TITLE="GPS"><U>GPS</U></A></div> </td> <td valign="top" height=395 BGCOLOR="#FFFFFF" TEXT="#080000" bgproperties="fixed" background="48908bb3.gif"> <div> <I><B>Radio-Navigation</B></I><I><B> </B></I><I>  </I><I>   </I><FONT SIZE="3" COLOR="#000099" FACE="Arial" ><I>              </I></FONT></div> <bR> <bR> <div> Les sujets NDB, VOR et ILS proviennent d'un site dédié à la radio-navigation.</div> <bR> <div> Pour voir le site, <FONT SIZE="2" COLOR="#0000FF" FACE="Arial" ><A HREF="http://www.navfltsm.addr.com/basic-nav-general.htm" TARGET="_top" TITLE="http://www.navfltsm.addr.com/basic-nav-g"><U><B>cliquer ici</B></U></A></FONT></div> <div> Pour télécharger un document Word (English), <FONT SIZE="2" COLOR="#0000FF" FACE="Arial" ><A HREF="http://www.acabidjan.com/_Files/NavAid.zip" TARGET="_top" TITLE="http://www.acabidjan.com/_Files/NavAid.z"><U><B>cliquer ici</B></U></A></FONT> (178K)</div> <bR> <bR> <div> <A HREF="id264.htm" TARGET="_top" TITLE="NDB"><U><IMG SRC="68396960.gif" border=0 width="150" height="150" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></U></A> <A HREF="id265.htm" TARGET="_top" TITLE="VOR"><U><IMG SRC="68296960.jpg" border=0 width="150" height="150" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></U></A> <A HREF="id266.htm" TARGET="_top" TITLE="ILS"><U><IMG SRC="68597960.gif" border=0 width="151" height="150" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></U></A> <A HREF="id268.htm" TARGET="_top" TITLE="GPS"><U><IMG SRC="68896960.jpg" border=0 width="150" height="150" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></U></A></div> <div> <TABLE BORDER="2" CELLPADDING="2" CELLSPACING="1" WIDTH="619" BORDERCOLORLIGHT="#C0C0C0" BORDERCOLORDARK="#808080" FRAME="BOX" RULES="ALL" HSPACE="0" VSPACE="0" BGCOLOR=#CCCCFF > <tR> <tD VALIGN=TOP HEIGHT= 16 WIDTH="141"><div> NDB</div> </tD> <tD VALIGN=TOP WIDTH="150"><div> VOR</div> </tD> <tD VALIGN=TOP WIDTH="150"><div> ILS</div> </tD> <tD VALIGN=TOP WIDTH="145"><div> GPS</div> </tD> </tR> </TABLE></div> <bR> <div> Les renseignements qui figurent sur ces pages ne sont malheureusememt pas (encore...)</div> <div> disponibles en français... <FONT SIZE="2" COLOR="#FF0000" FACE="Arial" >cliquez sur le sujet qui vous intéresse !</FONT></div> <bR> <div> <B>Les débuts de la radio-navigation</B></div> <div> Wallace over there by the white-board really got carried away when he overheard the </div> <div> word "Basics." I think we'll risk skipping his first lecture. </div> <div> We all intuitively know what Aviation Navigation means—it means knowing where you </div> <div> are, where you want to go, and having a good idea of how much time and fuel it will take </div> <div> to get there. Navigation means finding your way. </div> <div> The two most fundamental methods of finding your way in an airplane are <I>pilotage</I>—the </div> <div> identification of present position and direction of flight by seeing features on the ground, </div> <div> and <I>Dead Reckoning</I>. </div> <div> Dead Reckoning—an intriguing title. I was once told that the name stems from "You're </div> <div> Dead if you don't Reckon properly," but I think they were pulling my leg. </div> <div> Dead reckoning is the navigation procedure to plot and fly (in this case) a course based </div> <div> solely on mathematical calculations. </div> <div> UPDATE! UPDATE! Many Flight Simmers took pity on my pathetic lack of knowledge and </div> <div> patiently explained to me the origins of "Dead Reckoning." Here is one: </div> <div> "I have spent many (more than I care to count) years navigating sailboats all over the place. </div> <div> In the books that I learned from, it was referred to as 'ded. reckoning,' which stands for </div> <div> deduced reckoning as opposed to using true fixes."... thanks, dg.</div> <div> Dead Reckoning and Pilotage are so interdependent, though, that they are essentially one </div> <div> method. Ask a pilot how he intends to navigate to his destination, and if he says "by Dead </div> <div> Reckoning," one knows that he also intends to look out the window at the ground features to </div> <div> check his progress. </div> <bR> <div> Neither Pilotage nor Dead Reckoning require assistance from electronic aids to navigation, </div> <div> thank you very much. If the weather is good, and it's daytime, and you can see the ground at </div> <div> all times, Pilotage can be very satisfactory. But change any one of those variables and the </div> <div> excitement level can quickly escalate beyond what a mortal cares to handle. </div> <div> Dead Reckoning, on the other hand, is a satisfactory navigation procedure whether you can </div> <div> see the ground or not. After all, both Charles Lindbergh and Amelia Earhart soloed across the </div> <div> Atlantic navigating with Dead Reckoning. </div> <div> Three properly-performed actions are necessary for dead reckoning navigation to get you to </div> <div> your destination, at the estimated time of arrival: </div> <div> The pilot must properly calculate the course and fuel consumption. </div> <div> The pilot must accurately fly the aircraft </div> <div> The weather service must correctly predict the winds-aloft. </div> <div> Omitted is "Put enough fuel in the tanks for the journey, and then some." That slight oversight </div> <div> has ruined more than one perfectly-navigated flight. Few will argue that if the aircraft is running </div> <div> low on fuel, the fuel indicator becomes the most fascinating gauge on the panel. Yes, indeed,</div> <div>  it does. </div> <bR> <div> The first two items in the list are under the pilot's control and most pilots have the good sense </div> <div> to do them right. The third criteria is the one that notches up the interest level. Winds-aloft </div> <div> predictions are seldom accurate, and may never be. Sometimes the miss is huge. No big </div> <div> deal, though, if you can see the ground, have chart in hand, and it is properly oriented to follow </div> <div> your flight. You simply adjust for the wind based on landmarks spotted below. </div> <div> Assume that your estimated course was to take you directly over the power company with its </div> <div> 100-ft. tall smoke stacks. But there it is a mile or so to your left, its plume of white smoke laying </div> <div> down horizontally blowing towards you. Obviously, you must turn left some few degrees to get </div> <div> back on course plus make a heading correction once back on course to accommodate those </div> <div> strong winds. </div> <bR> <div> After returning to course you check the next landmark to see how good your heading correction </div> <div> was, and so on for each landmark, until you reach your destination. Very simple in theory. </div> <div> There is nothing inherently inaccurate about dead reckoning; it is limited only by the information </div> <div> provided. Dead reckoning is, in fact, the basis of all navigation. </div> <bR> <div> <IMG SRC="68ce7df0.jpg" border=0 width="231" height="223" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <div> The equator is an imaginary circle equidistant from the poles of the earth. Circles parallel </div> <div> to the equator (lines running east and west) are <I>parallels of latitude</I>. They are used to </div> <div> measure degrees of latitude north or south of the equator. The angular distance from the </div> <div> equator to the pole is one-fourth of a circle, or 90°. Thus latitude would run from 90° North</div> <div> to 90° South of the equator. </div> <bR> <div> Meridians of longitude are drawn from the North Pole to the South Pole and are at right </div> <div> angles to the equator. The "Prime Meridian" which passes through Greenwich, England, </div> <div> is used as the zero line from which measurements are made in degrees east and west to </div> <div> 180°. </div> <bR> <div> Any specific geographical point can thus be located by reference to its longitude and latitude. </div> <div> From the earliest days, determining latitude was relatively simple; measure the height of </div> <div> the sun with a sextant. Longitude was a different matter. Greenwich Observatory was set </div> <div> up by King Charles II in 1675 to study means of fixing longitude, and the observatory </div> <div> became the acknowledged world authority on the subject. The telescopes and other instruments </div> <div> there determined the exact position of the meridian, and in 1884 an international conference </div> <div> in Washington agreed that Greenwich should be sited at zero longitude </div> <div> By using meridians, direction from one point to another can be measured in degrees, in a </div> <div> clockwise direction from true north. Draw a course line on a chart and measure the angle </div> <div> which this line forms with a meridian. </div> <div> When moving north or south by one degree of latitude, the distance remains approximately </div> <div> the same whether the observer is at the equator or in London, New York, Tokyo, or Sydney. </div> <div> That number would be unchanged vs. latitude if the earth were a perfect sphere, which it isn't. </div> <div> The earth is somewhat flattened at the poles. </div> <div> The distance situation is quite different when moving east or west. </div> <div> Note the convergence of the meridian lines at the poles. Thus moving east one degree at the </div> <div> equator is a greater distance in feet or meters than moving one degree east in London, </div> <div> New York, Tokyo, or Sydney. </div> <bR> <div> Nautical Miles and Knots</div> <div> The circumference of the earth is divided into 360°. Each degree is further divided into 60 </div> <div> minutes. If you move one minute east or west on the equator, you have gone one nautical mile. </div> <div> Thus a nautical mile is the circumference of the earth divided by 360, giving the distance in </div> <div> one degree, and that is further divided by sixty for the distance in one minute of arc. </div> <div> Earliest estimates of the earth's diameter was 18,000 statute miles. As methods of measurement </div> <div> improved over the years, the earth's circumference "increased" to 24,901.55 statute miles. </div> <div> Hence the distance of a nautical mile similarly increased with time, too. What a nightmare that </div> <div> must have been for cartographers and navigators. </div> <bR> <div> Regardless of calculations of the earth's circumference, the nautical mile has been standardized </div> <div> at 6076.113 feet, plus another gazillion decimals. One nm = 1.15 statute miles for the purposes </div> <div> of estimating. Again, there are a gazillion decimals in the actual conversion. Using 1.15 will </div> <div> not fly you into a mountain. </div> <div> There is a lot of lore behind the knot ... tying knots into lines and clocking the time for each </div> <div> to pass a sailing ship, etc. Suffice it to say that a knot is one nautical mile per hour and hence </div> <div> is 1.15 statute miles per hour. </div> <div> Two further subjects should be understood before going on to charts. </div> <div> VFR vs. IFR</div> <bR> <div> The first is VFR weather vs. IFR weather. If the weather is "good," which the FAA defines as </div> <div> a visibility of at least three statute miles and that you can maintain at least 500 ft. clearance </div> <div> from the clouds above you, then you may fly by Visual Flight Rules. Flying at VFR minimums </div> <div> is not very comfortable and you better know where those 1000 ft. TV towers are, because </div> <div> you'll never see them in time to avoid them. They are marked on your charts. </div> <div> In practical terms, VFR is 3 miles visibility and 1000 ft. ceiling, because the minimum altitude </div> <div> one can fly in an uncongested area is 500 ft. above the surface. But that minimum altitude </div> <div> increases to 1000 ft. <B>above obstacles</B> near cities. So, if you depart VFR from Podunk </div> <div> Hollow Airport, with reported ceilings of 1200 ft., you're not going to be legal with that ceiling </div> <div> flying above New York City with all of its skyscrapers reaching for your landing gear. </div> <bR> <bR> <div> <I> <script language="JavaScript1.1">  </script> <noscript> <a href="http://www.xiti.com/xiti.asp?s=124046" TARGET="_top"><img width="39" height="25" border=0 src="http://logv23.xiti.com/hit.xiti?s=124046&p=&" title="Mesurez votre audience"></a> </noscript>  </I></div> <div> Copyright © 2003 ACAbidjan - All rights reserved</div> </td> </tr></table></body>