"Robert Barker" wrote:

Working on getting my PPL and I'm trying to figure out the difference
between standard rate turns versus constant rate turns and their
relationship to speed.

IIRC, a standard rate turn is 3 degrees per second and turn you 180 degrees
in 1 minute. The rule of thumb for the bank angle to achieve this is to
divide the airspeed by 10 and add half the resulting answer - i.e., standard
rate at 100kts is about 15 degrees of bank... (So, if that's a standard
rate turn, what's a constant rate one? Something other than 3 degrees a
second?)

A standard rate turn is a specific KIND of constant rate turn. It's a
constant rate turn whose rate happens to be 3 degrees per second.

Ask your instructor to show you a chandelle or a lazy eight -- those are
maneuvers from the commercial checkride which are NOT constant rate; the
rate of turn changes throughout the maneuver. Be warned, your instructor
may be hesitant to show you these because the last time he did them is
probably the day he took his commercial checkride and he's forgotten how to
do them :-)

But there's an indicator of rate of turn on the turn coordinator that
indicates the standard rate turn. The mark doesn't move. The turn
indicator is a gyro instrument just like the attitude indicator which also
indicates bank. Question: How can the TI always hit the same mark for a
standard rate turn independant of airspeed if, in fact, I'm turning at
different bank angles as indicated on the AI?

Because the TC isn't an ATTITUDE gyro, it's a RATE gyro. Actually, a
modern TC is designed to measure a mix of roll (bank) rate and yaw (turn)
rate. There's a lot of clever engineering that went into designing how
these little wonders work.