"thumb method" for determining hold entry
I was taught this method by my instructor when I was working on my instrument rating. I have also read about this method in instrument books, such as the ASA instrument flying manual.
I have discovered that this method does not work all the time, but yet I haven't found in textbooks what the "exceptions" are. Can anyone explain these to me?
If your holding instruction is (sorry if I screw this up, I haven't done this for a while!)... "Hold east of the 10 DME fix on the 270 radial of the ABC VOR, left hand turns, EFC at blah blah." When you arrive at the 10 DME fix you are heading 270.
Wouldn't the correct entry be the direct entry? Why is it that if you use the thumb method it would tell you that either parallel or teardrop entry is appropriate when that's incorrect? Or am I just doing the thumb method incorrectly?