The first time I ever flew a DME arc was on my CHECKRIDE back in 1992. Up until then I had only just read and talked about them. I was doing the multiengine portion of my commercial checkride, and because my instrument rating was at that point for single-engine only, I had to demonstrate an approach in the multiengine aircraft to gain instrument privileges in the multi. During preflight, I rejected the Seminole I had trained in when I found an oil leak (the examiner approved of that decision), so I got assigned a different Seminole from the flight school that I had never flown before. It had a DME in it, so of course fair game, the examiner asked me for a DME arc. I did it, I passed, all thanks to my fabulous instructor. Turn 10 Twist 10!!
OK, probably gonna get a lot of flack, but this is my opinion. The term 10 twist hand method is a bad choice and not really safe. Here’s why. In the IFR environment it is very busy and task saturated then to add more work than is needed. Turning the OBS every 10° and turning, the airplane will lead to the situation where most pilots get so engrossed that they overshoot their inbound course. This is the method that is worked for me in my 45 years of flying. Using the above example that John is showing, when you arrive at JEBNO, you will turn to the left because the VOR now will be on your right and you will be approximately 90° from the fix. This you can note with looking at your DG or HSI. R077 will be on your left side of the DG or HSI and R258 will be on the right side of the DG or HSI. As you’re no flying the arc you monitor your DME. In a Cessna 172 at about 100 or so knots you turn towards the right approximately 3° to 5° every five seconds. If you’re getting closer to the VOR, you delay your turn, if you are moving away from the VOR you increase your turn by a degree or two to get back on DME. 80% of the DME arc that I do is dead on and occasionally, it may wander .1 nm either side. That is acceptable standards. as I’m doing this and flying the arc I turn my OBS to the inbound course and also watch my DG/HSI as that inbound course heading will be approaching the 90° point either left or right depending on the direction of the arc. When you are about 80° or on the OBS around two dots, you can start your turn inbound and you generally will wind up directly on course within the donut. Try this method in the simulator and see if this does not decrease your workload and make understanding a DME arc more clear. One other thing I may be weird, but I do a lot of reverse sensing flying. It keeps me sharp and it lets me have situational awareness at all times. Some of the planes I fly just don’t have HSIs. If you really wanna be a hot shot in your expensive plane, you probably can let the auto pilot fly the approach for you. Fly safe.
Never heard of DME arcs until well after my instrument rating when I went to USAF flight school and used an RMI. I always wondered how to do it with a plain old OBS setup.
The first time I ever flew a DME arc was on my CHECKRIDE back in 1992. Up until then I had only just read and talked about them. I was doing the multiengine portion of my commercial checkride, and because my instrument rating was at that point for single-engine only, I had to demonstrate an approach in the multiengine aircraft to gain instrument privileges in the multi. During preflight, I rejected the Seminole I had trained in when I found an oil leak (the examiner approved of that decision), so I got assigned a different Seminole from the flight school that I had never flown before. It had a DME in it, so of course fair game, the examiner asked me for a DME arc. I did it, I passed, all thanks to my fabulous instructor. Turn 10 Twist 10!!
Wow nice work! Sounds pretty stressful, but you handled it.
OK, probably gonna get a lot of flack, but this is my opinion. The term 10 twist hand method is a bad choice and not really safe. Here’s why. In the IFR environment it is very busy and task saturated then to add more work than is needed. Turning the OBS every 10° and turning, the airplane will lead to the situation where most pilots get so engrossed that they overshoot their inbound course. This is the method that is worked for me in my 45 years of flying. Using the above example that John is showing, when you arrive at JEBNO, you will turn to the left because the VOR now will be on your right and you will be approximately 90° from the fix. This you can note with looking at your DG or HSI. R077 will be on your left side of the DG or HSI and R258 will be on the right side of the DG or HSI. As you’re no flying the arc you monitor your DME. In a Cessna 172 at about 100 or so knots you turn towards the right approximately 3° to 5° every five seconds. If you’re getting closer to the VOR, you delay your turn, if you are moving away from the VOR you increase your turn by a degree or two to get back on DME. 80% of the DME arc that I do is dead on and occasionally, it may wander .1 nm either side. That is acceptable standards. as I’m doing this and flying the arc I turn my OBS to the inbound course and also watch my DG/HSI as that inbound course heading will be approaching the 90° point either left or right depending on the direction of the arc. When you are about 80° or on the OBS around two dots, you can start your turn inbound and you generally will wind up directly on course within the donut. Try this method in the simulator and see if this does not decrease your workload and make understanding a DME arc more clear. One other thing I may be weird, but I do a lot of reverse sensing flying. It keeps me sharp and it lets me have situational awareness at all times. Some of the planes I fly just don’t have HSIs. If you really wanna be a hot shot in your expensive plane, you probably can let the auto pilot fly the approach for you. Fly safe.
Thanks for your input! Turn 10, twist 10 certainly isn't the only way to do it.
Never heard of DME arcs until well after my instrument rating when I went to USAF flight school and used an RMI. I always wondered how to do it with a plain old OBS setup.
Thank goodness for RMI!
Nicely explained, thank you
It's always fun to fly DME arc
Agreed, they can be a lot of fun!