Basics - (Elevator) Trim

antone wrote:

Can't quite get the hang of this. I mean, I understand the concept, I just can't seem to get it right when flying the Cessna 172.

What generally happens is I trim too much or too little, resulting in my aircraft bouncing up and down like it was on a trampoline until I eventually find what I was looking for, by which time the plane is probably 500ft outside the altitude I was aiming at.

So are there any tricks to this, or is it simply a case of trial, error and learn? Anyone's advice would be much appreciated.

Using simple, unprofessional terminology:

Establish your atitude, altitude and desired speed by handflying first.

Only then begin to trim in very small increments. Needless to say, keep scanning your instruments to ensure that you're staying within your desired limits.

Tailhook is right. First when you are climbing to a desired altitude, you need to establish climbing Power (in level flight, or straight after take off), you then need to adjust your Attitude (i.e. pitch up to start the climb and maintain the climb) and then adjust your Trim in small increments, whilst constantly relieving more and more pressure on the yoke until you can take your hands away.

For ascents: ➡ Power, Attitude, Trim - PAT

For descents: ➡ Attitude, Power, Trim - APT

For descents, it is Attitude, Power, Trim, so you need to reduce nose up attitude, lower your power, and then slowly change the trim to stabalise the aircraft and reduce the pressure on the controls.

Hope it helps 😉

99jolegg wrote:

Tailhook is right. First when you are climbing to a desired altitude, you need to establish climbing Power (in level flight, or straight after take off), you then need to adjust your Attitude (i.e. pitch up to start the climb and maintain the climb) and then adjust your Trim in small increments, whilst constantly relieving more and more pressure on the yoke until you can take your hands away.

For ascents: ➡ Power, Attitude, Trim - PAT

For descents: ➡ Attitude, Power, Trim - APT

For descents, it is Attitude, Power, Trim, so you need to reduce nose up attitude, lower your power, and then slowly change the trim to stabalise the aircraft and reduce the pressure on the controls.

Hope it helps 😉

I'd never heard of the P A T 😳 ... nice one Jon 😀

Its something all flight instructors teach when teaching how to trim a plane when doing your PPL 😉

99jolegg wrote:

Its something all flight instructors teach when teaching how to trim a plane when doing your PPL 😉

PPL? I got my instructions from a fighter ace " Get it right boy or you might not get a second chance!!!"

But it works, though the terminology sometimes differs 😀

I have a somewhat different view, especially of descent techniques but also for enroute climbs. When descending, the acronym I could use is T. When I'm ready to descend, I will roll in sufficient trim to establish the rate of descent I want to use. It is not necessary to apply elevator force through the control yoke to do that nor do I adjust power setting until it is necessary to do so to control airspeed. There is no reason you could not use APT for descents but it is not necessary and I like to use higer speed descents to make up for some of the time I spent at lower climb speeds in my initial ascent.

PAT does work for initial climbs but for enroute climbs, I also use trim to establish the climb and then go to full power once I am sure I will not redline RPM's. If I am crusing at max cruise RPM's (2600 RPM at 5,000 feet in my C-172) and I go to full power before establishing the climb, I could overstress the engine.

I neglected to mention in my first post on this topic that having to frequently adjust trim settings, as posed in the original question, is normal. It takes a light and discerning touch on the trim wheel to get it right in the real airplane and, if anything, Sim is even more difficult since you cannot feel the control forces as well as in real airplanes.

Once trim is correctly set, it must be frequently adjusted by slight increments because th aircraft is burning off fuel and weight and balance are constantly changing. I don't know if Sim models that fuel burn off but I do notice that trim needs adjusting in Sim, just not as frequently as in the real airplane.

Don correct as usual! I think as an experienced pilot one does not necessarily do things by the book but for training purposes APT is very useful. In fact thinking about it maybe I do it subconciously....flying tomorrow so will know!

Sorry to hijack this post but PH I have read your many helpfull posts and was wondering what planes you fly?

It's good to hear from real pilots 😉

My instructors taught me P.A.T as well, but slightly differently. My training manual shows the following:

Climb from S & L: PAT
S & L from climb: APT
Descent from S & L: PAT
S & L from descent: PAT

I'm not saying my way is better, however, just adding to the conversation. 😉

to me, trim is sort of like chocolate syrup on ice cream. without trim, i can maintain the plane at a certain altitude quite well. with trim, i can just "sit back and relax" as the plane keeps its self trimmed. 😎

Thank you all for your thoughts. So, it seems the answer is "No, there's no easy trick" which is what I suspected.

Off to do more practice, then 🙂