Re: Rules of thumb

Absolutely right. I'm not suggesting anything different!

In addition to Peters point, I had a play today and a chat, and we reckon
that whilst in THEORY the plane might level off as air density increases, in
practice it is unlikely because our operating levels are too low and our
available powers are too small (where "our" means yer average flying club
warrior etc).

And when a Warrior will cruise pretty much at say 2300RPM and not a jot
below (to maintain 100kts) then dropping the power, even from full throttle
revs (say 2550) by my mentioned 250 would still leave only 2300 which is
only just level flight. Anything less than that and it will sink till it
crashes. Obviously it could be trimmed to fly level at a lower speed but
the principle holds.

If our average PPL was cruising along therefore at 3000 feet and dropped the
revs by 300, then no, he'd never reach denser air and level off.

I will have a climb to c10,000 feet though one day soon and have a gander
from that rarified level!

David



"Chris" <today@xxxxxxxxxxxxxx> wrote in message
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"david" <david_perry@xxxxxxxxxxxxx> wrote in message
news:dvpgj6$41l$1@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
I love rules of thumb, mostly because being a bear of very little brain,
they help me. Doing the FI course, as I am, I am being taught RoT all the
time, most I have heard of but I found one today that's brand new to me.
So, in the spirit of sharing...

when you want to cruise descend, REDUCE the POWER by half the required
RoD in feet in revs and touch nowt else. She'll settle and descend at
cruise speed till you either stop it or crash!

So, if you want to get your PA28 to go down at 100kts and 500fpm, drop
the RPM by 250 revs and down ye go.


I was always taught to trim for airspeed not attitude so that any change
to throttle would have me doing either climbing or descending at the
trimmed airspeed.



.

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