Hi all, how do you pros handle a plane like the PA28 Arrow when it’s time to descend. I use the elevator trim but this can lead to various degrees of ups and downs, especially during turns. Is there a way to control the plane better during descent or is this pretty much the way it is?
Attitude changes are primarily done with the elevator. After the new pitch attitude has been established you trim the force away which is required to hold the yoke in its off-center position.
If you turn with a 30° bank angle or less, the nose should drop only a bit, if at all.
If it does, you have to pull the yoke back (don’t trim) to maintain the pitch attitude and when rolling out of the turn, start relaxing the back pressure.
Reduce Power — pitch for Airspeed — Trim . . . . . . . . . (PAT)
PAT down was what I read once as a mnemonic.
I will lower the nose with the help of trim because the airplane will speed up and nose down trim will be needed. I personally aim for a given rate of descent and if my airspeed starts to get close to or inside the yellow arc (in bumpy air) I will reduce power and still try to hold that given rate of descent.
When in stable and trimmed cruise at best power 75% setup, I just drop the throttle from full to roughly 50%.
The nose will drop so you just hold it for a VS of - 1000ft/m and after a few seconds it will stabilize itself with this descent rate at around 120kt IAS.
I don’t need to trim or anything, just the reduces thrust will turn into a stable descent at a nice VS.
You can control your descent (and climb) rate solely by the throttle.
This method works, but you should always actively fly the aircraft instead of waiting what will happen if you e.g. reduce power.
In your example the correct sequence would be to pitch the nose down to achieve a 1000ft/min ROD while simultaneously (or shortly after pitching the nose down) reducing the power to 50%.
That way you don’t need to trim, but you are still actively controlling your aircraft.
Btw, many prop pilots are happy if the speed finally increases during the descent while maintaining max cruise power. This requires re-trimming.
It’s not like something unexpected will happen. Thrust controls vertical speed if you trim for airspeed. Reduce thrust by keeping airspeed will result in the vertical speed required for descent. How is that not actively flying?
My approach will keep the IAS and avoids retrimming. It doesn’t matter if I pitch down or the aircraft does that, the result is exactly the same.
Well if you want to increase your IAS, that’s a different topic. I don’t see the need to do so since all your VNAV calculations will be different if you don’t account for the increased airspeed.
Much easier to have a constant IAS and throttle for the required VS.
Try not to fly the Aircraft on the trim !!
Set the attitude you want using the yoke, then set the trim to hold it there without force on the yoke.
As has already been pointed out above you can use PAT, or in some cases APT to set your descent up, depends on how you want to descend.
If your desired speed is greater or close to your cruise speed then you may choose to use APT, if your desired decent speed is less than your current cruise speed then it would be appropriate to use PAT.
It’s not about things that will happen, it’s about developing bad habits.
Your method works in one aircraft, but will not work in another.
On most prop driven aircraft the IAS during descent is higher than the cruising speed.
Presumably assisted here because prop drag is not modelled correctly, other than maybe the DR40? Pushing the prop lever forward for descent is not going to help here till they model this better I guess.
No. Prop drag is only a factor at idle.
The IAS speed on many props and turboprops is so low that it’s nice to see if it creeps upward a bit more during descent.
Even in the Dash7 and 8 we didn’t have to reduce power.
Did a few tests with the TBM and at high speed prop drag seems to be plausible.
The lower the speed becomes, the greater the lack of sufficient drag.
Aside from the advice already given,
power management is described in the manual in Descent section.
“Move the propeller lever forwards to the fully forward (high RPM) position and then reduce the throttle to obtain
15 inHg on the manifold pressure gauge. The airspeed will start to decrease.
Once the airspeed has reduced to 110 knots, start the descent by disengaging altitude hold mode and then
pitching down to obtain a -500ft/min descent rate.
As the aircraft stabilises in its descent, adjust the throttle to maintain 110 knots.”
Little Navmap is great for altitude and terrain planning.
1000 fpm is a little hard on the ears in an unpressurized aircraft like this one.
Which manual? I didn’t find anything concerning descent at all in my PA28 manuals.
Vno is 146kts, why would you want to slow down to 110kts?
Not everyone does, if you read the discussion I linked.
But it’s typical.
The Just Flight PA-28R Arrow III MSFS manual.pdf in
The ODM (also provided by JF) states 146KIAS (2400rpm, throttle as required) as well, with 1000fpm. Nothing to worry about.
110kt IAS descent @500fpm is in the “flying the arrow” chapter (page 67), not sure why they chose that speed.
Ctrl+F 110 in the linked thread shows nil results?
The 110 is from manual.
Read the discussion, it’s two pages.
Ctrl+F Arrow or Piper…nil results.
Page 67. How hard is it?
On my Arrow IV turbo (so different engine and power settings), when I need to start descending I pull about 2 inches of manifold pressure and let the nose drop. That gives me a 500 fpm descent at close to top of the green (145-150 kias). While descending every minute or so I pull another inch of mp.
Same approach as mine, just with the higher airspeeds due to the Turbo version and 500fpm for comfort.