![]() ![]() fly the arc making corrections to stay at 90-degrees to the radial until reaching the lead-in radial at which time you begin the intercept turn. A DVOR (such as I have on my aircraft) will allow you to keep a running track of radials as the are crossed. The non-conformance way, with ATC approval, is to fly a tangent to the arc much closer in than the IAF to allow. by just flying at 90-degrees to the radial you will be always flying the tangent to the arc with adjustments made for wind drift you can fly the arc and remain oriented as you approach the lead-in radial where the intercept heading is flown to the final approach course. If your aircraft has an RMI or a DVOR you have another option since you have a constant read-out of the radials extending from the VOR. fly the arc making corrections to stay at 90-degrees to the radial until reaching the lead-in radial at which time you begin the turn to intercept the inbound radial. ![]() Slight deviations may be made for wind correction and on reaching the lead -in radial you turn a 45-degree intercept to the final approach course. Turn the OBS ten-degrees in the direction of the arc, when the needle centers turn ten-degrees into the arc and reset the OBS for the next ten degrees. Standard instruction is begun by tracking to a VOR until the distance equals l10% of the ground speed plus the arc DME before turning to 90 degrees of the inbound course. At the lead-in radial you make a 45-degree cut toward the final approach course This process is repeated plus adjustments for wind drift until you come to the lead-in radial. Advance the OBS setting by 10-degrees and fly to intersect the radial at which time you will change heading ten degrees and change the OBS by another ten degrees. You are now ready to turn 90-degrees to fly tangent to the arc. The standard method of flying a DME arc consists of flying toward the center of the arc and executing a turn when you are at a distance of the selected DME arc plus 1-percent of the aircraft ground speed. Round to half mile for lead-time to turn. Square the Mach number, ignore the decimal. Lead the turn to the chord line by dividing one percent of the ground speed by two to get the lead-in distance or Ground speed divided by 200 does the same thing but not mentally Otherwise, just vary arc to keep distance. Identifying lead-in radial is critical and one other along the way. Use chart to make first intercept turn which may vary in degrees. DME arcs are well on their way to obsolescence. ![]() DME arcs can be eliminated by accepting vectors to the final approach course. Localizers twitch at 2.5 degrees so begin early. VOR needles are alive at the ten-degree point. Intercept turns off the arc should begin ten degrees early. Tune appropriate navaid and OBS for final approach course. An airspace you wish to avoid can be arced around using a center located VOR or ARP as reference. An IFR certified GPS can be used to fly an arc. Wind direction and velocity changes will require changes in you chord lines. The 10-degree chord lines only work in no-wind conditions. Should you get two miles inside on your chord line turn 5 or 10 degrees out. The IFR flight test allows only one nautical mile each side of the arc. DME arc airspace is protected four nautical miles up to 500 feet each side of the arc. Once you are unintentionally outside the arc be aggressive with up to a 30-degree cut for a chord line. You will remain always slightly inside the arc where corrections are easier to make than when outside. The DME will count down and then up and then just before you reach the arc, take another 10-degree cut. 9 divided by 2 to give 4.5 nm lead-in required for standard rate turn. Lead the turn to the chordline by dividing one percent of the ground speed by two to get the lead-in distance. Entry from the outside requires that you make an 80 degree heading change just prior to the arc at the IAF. Charted arc radii vary from seven to 30 miles. DME location must be in IFR certified GPS database to be legal in flying the arc. DME is no longer required above 24,000' if you have an IFR certified GPS. Only DME distance is required for flying the arc. ![]()
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