Danny Deger

"EridanMan" <scott.cragg@> wrote in message
news:1176328741.004667.51380@y80g2000hsf. ...
snip

> Yoke. Changing pitch attitude almost always induces phugoid
> oscillations, with the yoke, those oscillations are trivial (almost
> subconscious) to damp. Trim provides no such mechanism (without
> grabbing the yoke anyways), so its generally a bad idea to fly with
> it.
>

You bring up a good point on phugoids. I have flown everything from J-3
cubs to F-4E (but no heavy time) and the difference in phugoid tendancy is
HUGE. On the Air Force jets, the trim in on the stick, so I didn't fly just
trim. I am currently flying a Taylorcraft which must have a highly damped
phugoid. I find I can fly it with only trim to make gradual changes in
altitude. In other planes, this can't be done as you mention.

Danny Deger

> For any pitch attitude change, the general rule of thumb is pitch,
> power, trim off pressure as necessary, in that order.
>
>> If I have nose-down trim applied to go fast at my low altitude, it seems
>> I
>> should be able to trim slightly upwards and change altitude easily, then
>> trim
>> back for level flight at the new altitude. If I already have nose-up
>> trim
>> applied, this may not work, and eventually I'll have to add power.
>
> It sounds like you're trying to fight the simulated phugoid
> oscillation by using trim to make very low amplitude adjustments...
> This just increases the period of the oscillations, it in no way
> prevents them from occurring.
>
> Power is a good, 'side effect free' mechanism of doing fine trimming
> of your aircraft's altitude. In fact, I know instructors who advocate
> only ever using the power to make the final 'lock' onto a new cruise
> altitude, no matter what.
>
> For example, the mechanism you would use to level off from a cruise
> climb would be as follows:
>
> 500 feet below target altitude, push the nose forward gently to bring
> airspeed up to cruise airspeed. Once you've reached cruise airspeed,
> go ahead and trim to hold the attitude, but allow your power surplus
> to continue pulling you up the last hundred feet or so to your target
> altitude, only backing off the power the moment you reach it.
>
> The descend-to-altitude is the same procedure, only with reduced power
> instead (set up the aircraft in cruise attitude before you hit your
> target altitude at a reduced descent power setting, and allow the
> aircraft to settle onto target altitude before increasing power back
> to cruise power)
>
> I can see the theoretical advantages to this approach, but I would be
> lying if I said I used to religiously (I still don't keep that far
> ahead of the aircraft).
>