Trim in a Piper Warrior

[KOAK Flyer]

Hey everyone,

I am a new flight instructor and have started a student off in a 1977 PA-28-161 Piper Warrior. The majority of my training has been in Cessna 172s, but I have about 20 hours of Warrior time in addition to about 70 hours in an Arrow. The problem I am finding is that my student is having a very difficult time maintaining wings level for straight and level flight, as he can hold his altitude well but the wings keep oscillating right and left. We have tried switching the fuel tanks, adjusting rudder trim, and covering up the flight instruments, but the difficulty is still remaining. I will say that, when I covered up the instruments, the degree to which the oscillations occurred decreased, but they still exist to the point where, every 20 or 30 seconds he has to apply a slight control correction. As I don't have as much experience in a Warrior as I do a Cessna, and because I am a new flight instructor, I am not exactly sure as to what the problem may be, though I suspect it is a combination of fixation on the flight instruments, not applying the correct amount of rudder trim, and, to a lesser degree, fuel imbalance in the wings. Anyone have any comments or suggestions as to what I can do to help this student? Thanks!

 

[tgrayson]

Anyone have any comments or suggestions as to what I can do to help this student?

He might also be using the yoke to support the weight of his arm. Ensuring that he holds the yoke with a very light grip can prevent that from happening, the proverbial two fingers. Also, holding the yoke from the base of the horn rather than at the end might allow him to rest his elbow elsewhere.

How does the airplane fly, hands off?

 

[bdhill1979]

He might also be using the yoke to support the weight of his arm. Ensuring that he holds the yoke with a very light grip can prevent that from happening, the proverbial two fingers. Also, holding the yoke from the base of the horn rather than at the end might allow him to rest his elbow elsewhere.

How does the airplane fly, hands off?

as usual T is right

In one of my early lessons I tell them to let go and put their feet on the floor, and just watch for a minute. I let the plane just do whatever it wants and it demonstrates the inherent stability of the airplane. Then I will upset the airplane a little and again demonstrate how after a few oscillations the airplane will eventually come back to a stable attitude. Then we go through each of the controls individually; just the trim, just the rudder, just the ailerons (which demonstrates adverse yaw really well), just the throttle.

What you develop is an understanding that for the most part it is the pilot that makes the airplane not fly straight, not the airplane wandering away from them.

I see it a lot in early instrument training as well when they look down and their left hand goes down too, taking the yoke with it.

 

[BillPerryCFI]

The heavy left hand syndrome is a killer every time. People think that they have to grip the yoke, not simply hold onto it. Fuel imbalance in the Warrior/Archer series shouldn't give you too terribly much roll imbalance, but if your carrying an odd number of people or significantly more weight on one side vs the other I would look at that.

An easy diagnosis for a crooked airplane is this. Simply align the rudder (not the nosewheel) using the nose wheel tow bar and the ailerons (match position from side to side) from the outside during a preflight and look at the control positions inside. It will become pretty quickly apparent if they don't line up if they are out of rig. In over 1,100 hours in the Archer/Warrior/Seminole/Seneca series instructing, that's what I've found to be the most common (and most annoying :whatever.

 

[ppragman]

In the cherokees Ive been flying, if I get really tired, I'll burn more out of the left tank so that it balances my hand. Works great. (lol)

 

[OregonTrail]

In the cherokees Ive been flying, if I get really tired, I'll burn more out of the left tank so that it balances my hand. Works great. (lol)

autopilot.

I flew a tank in a cherokee for 1.7 just to feel the affects of imbalanced weight, wasnt that big of a deal.

 

[shdw]

I will say that, when I covered up the instruments, the degree to which the oscillations occurred decreased, but they still exist to the point where, every 20 or 30 seconds he has to apply a slight control correction.

Can you give more details? Are you flying hands/feet off to test this? Is it a typical turbulent summer day or is it completely calm? What kind of fuel loading do you have in each wing when it is occurring?

Also on a different note, if covering up the instruments is helping I would bet your student has Flight Simulator X syndrome. If you like, you can try covering them more often and making him fly the horizon to get his eyes out and off the panel more. Horizon eye level = level flight.

 

[KOAK Flyer]

Thanks for your replies everyone. I tried covering up the instruments again today and emphasized the light grip on the yoke and the result was that the student had much better control of the aircraft in terms of keeping the wings level.

As far as handling, I have been able to get the aircraft trimmed up to where I can keep the wings level, hands and feet off, for a little over a minute before it starts a very gentle bank to one side or the other (fuel to the tabs in both tanks) in calm air conditions. I have not had a chance to check the rigging on the aircraft yet and will be interested to see what that reveals. Thanks again!

 

[shdw]

As far as handling, I have been able to get the aircraft trimmed up to where I can keep the wings level, hands and feet off, for a little over a minute before it starts a very gentle bank to one side or the other (fuel to the tabs in both tanks) in calm air conditions. I have not had a chance to check the rigging on the aircraft yet and will be interested to see what that reveals. Thanks again!

Welcome to spiral instability. Just about every small aircraft will eventually encounter, even on a calm day, some small displacement which will trigger this to start. You should sit back for 5-10 minutes one day and watch it as it progressively gets worse and worse until it finally ends in a spiral that if you didn't stop would end up making a big hole in the ground. It isn't a dangerous demonstration as it happens very slow, but it is a great demonstration to a student why they can't get distracted in the aircraft for long periods of time. Interestingly enough the calm days are the worst because you won't feel it happening if you aren't looking for it. This all happens because our aircraft tend to have greater directional stability than lateral stability.