A Question About Instrument Flying?

[B-J-J Fighter]

I was looking at the "rule of thumb" section of the page just a minute ago and noticed the formula for calculating distance travelled when flying a DME Arc. What would be the importance of knowing this other than situational awareness? BTW the "rule of thumb" section is a great area of the page. If you havent looked at it before you should check it out.

 

[midlifeflyer]

To give you something to do if you're bored while flying the arc.

I have the feeling it's a bit like the "distance to" calculation: fly off course (always wise under IFR) so that you canfigure out that if you stayed on course, you'd be there already.

 

[mar]

Descent planning

Large, heavy airplanes have more mass, more inertia and thus take longer to slow down to configure for the approach.

If you were given a clearance like, "maintain 2000 or above until established on a published portion of the approach, cleared ILS 25..." you could manage your descent to arrive at 2000 feet before you turned onto the LOC.

It would be really inefficient to hit 2000 as you intercepted the arc and then arc around for 10 or 12 miles at a higher power setting. Instead, it's a thing of beauty to watch a perfectly planned descent come together.

Turn onto the arc at 250 passing thru 3000 or whatever...level at 2000 for a few miles...airspeed bleeds down to first flap speed...turn onto the LOC...more flaps and gear...nicely stabilized...small corrections....then GREASER.

It all starts with the descent planning.
Fly safe.