What I am saying is that for the 3times rule the ROD needs to change for different speeds. Do you agree with that? If you do then we are not in dispute.
I've been saying in all my posts that the ROD depends on the aircraft type and speed. It was you who came up with a 1500 fpm ROD for all types of aircraft. But I'm glad that you now agree that the ROD depends on the speed. In fact, multiple people have mentioned 5x groundspeed as a good ROD. (Although if you do the calculation properly you'll find that it's more like 5.5x the groundspeed.)
The original post I replied to was someone saying they use the airline model ( i.e 250 kts ish and apply it for slower aircraft) The average for that is 1500fpm, which would not work for 90 kts.
A&C only said that he used the 3x rule to determine his TOD point. It was you who first mentioned anything about a 1500 fpm ROD, and started applying that ROD to small aircraft, with obvious results.
Anyway, I think we've now established that the 3x rule works for all types of aircraft, assumes a three (point thirteen) degree flightpath, and to achieve that three degree flightpath you need five (point five) times the groundspeed as your ROD. Agreed?
On a slightly different note. On occasion you can can descent light aircarft at 1500fpm without to much trouble. In some situations it may be necessary.
Tell me about it. I'm training for an aerobatics competition (basic level). When we perform a spin we have to end in a 90-degree downline and we see airspeeds of 90-110 knots, straight down, before we pull up to the horizontal. That's over 13.000 fpm. Not for long, obviously, and it's very unnerving the first few times. Fortunately we lose less than 1000 feet in such a spin so it's not that hard on the ears.
I do not recommend that technique if you find yourself 1000 feet too high on an IFR approach though.
