Piper Arrow trim gets stiff at 150 mph.

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paramax55

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paramax55
I have a '72 Arrow II, 200 hp. When I bought the plane, the trim was SUPER stiff. Everyone who tried it complained about it. After a couple of months, I kicked myself because all it needed was a fresh lube. Well, here it is, a year amd a half later, and it started to get stiff while in the descent. I decided to fix it right, so I took the whole jack screw assembly apart. I cleaned everything down to metal and used fresh Luriplate Aero on it all before putting it back together (everything but the cable and outside of the drum).

Well, it works like a dream now - until you get up to about 150 mph. It stiffens up and the electric trim clutch just slips. Level off and slow down, and everything goes back to good. You can manhandle the yoke, take pressure off the trim tab, and it also works. I also noticed that the top part of the threads on the jack screw are worn. The bottom of the threads look normal - kind of how it would look if you used a bolt to "jack up" a heavy load and "stretched" the threads.

I'm thinking I'd like to try a new jack screw and see what happens, but I don't see a part number for it - only for the drum, washers, and cotter pins. I'm sure I could make another with the lathe and mill - maybe even using some all-thread (I doubt there's a ton of stress on it), but I'd prefer not to be a test pilot if a store-bought piece is available.

Anybody have any other ideas?
 
Isn't Vne about 152 kts in an Arrow II? I wouldn't imagine you spend a lot of time in that range and you certainly shouldn't be going past that.

My thought is that you're hitting a range where the mechanics of the lever to roll the trim cannot overcome the 150 mph wind forces trying to push the trim tab flat again. It works otherwise. I presume it works easily on the ground. The one change is that in the air going at Vne, you have a lot of wind pushing back on the trim tab. It may even be a design mechanic that you're hitting a stop designed to keep you from trimming to more than Vne.

I presume you made all the proper log book entries and had the proper authorization to do the work.
 
Kts vs Mph... doesn't even hit the yellow until 160 mph.
 
bflynn said:
Isn't Vne about 152 kts in an Arrow II? I wouldn't imagine you spend a lot of time in that range and you certainly shouldn't be going past that.

My thought is that you're hitting a range where the mechanics of the lever to roll the trim cannot overcome the 150 mph wind forces trying to push the trim tab flat again. It works otherwise. I presume it works easily on the ground. The one change is that in the air going at Vne, you have a lot of wind pushing back on the trim tab. It may even be a design mechanic that you're hitting a stop designed to keep you from trimming to more than Vne.

I presume you made all the proper log book entries and had the proper authorization to do the work.
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Vne 214mph
Vno 170mph

There's an arrow I rent that doesn't give much down trim while doing a cruise descent.
 
okay... everyone sees the kts vs mph thing now. Seems like a normal operating speed.
 
Isn't it funny that there is always someone who is more worried about the paperwork than actually fixing the airplane correctly? Yes, I am working with my IA and his answer was "I'd ask your forum buddies. They'd probably know." As far as "safe" vs "legal"... I could have continued to fly the airplane with a dry jack screw (for instance) and it would have been perfectly legal - but not safe. Someone could argue that removing the tailcone and lubricating the jack screw involves a complex disassembly and, therefore, is not legal without an A&P - but it would make the airplane more safe. If one had to choose, which is better?

This airplane is both safe and legal.
 
Do not skimp on MX when it comes to jackscrews, well don't skimp on MX at all, but especially on jackscrews

Lube is your friend, as are inspections


Are there any easier access, access panel mods for the arrow?
 
James331 said:
Do not skimp on MX when it comes to jackscrews, well don't skimp on MX at all, but especially on jackscrews

Lube is your friend, as are inspections
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So true. Someone loved this airplane in the past - and it wasn't either of the last two owners. It's taken the better part of a year to get this thing back in shape.
 
paramax55 said:
Hey, Thanks!
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I liked the part listing with serials. Looks like a good supply house but I haven’t used them. Muncie is also another good place to check for Piper parts.

I usually give the poster a ration of crap for my search engine services but let you slide because you’re new here. Be on notice that in the future said ration of crap will be supplied. Welcome to POA.;):D

And yeah, I found a lot of parts sources when fixing stuff on the ‘kota. It takes some effort to overcome a few years of neglect.
 
Well, mow that I look again, #37 is listed as "SHAFT - stabilator trim." I thought it was pointing to a washer.Screenshot_2017-11-08-15-53-06.png
 
bnt83 said:
Almost free considering oil filters are like $20 now.
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I’m guessing that if the screw has wear problems the bearings have problems too (which may explain the problem under load). Renew the assembly for another $100? Easy call even if not paying for labor.
 
paramax55 said:
This airplane is both safe and legal.
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If your trim is binding during flight, at any normal speed, it isn't safe or legal (ie: Piper didn't design it that way).

paramax55 said:
So true. Someone loved this airplane in the past - and it wasn't either of the last two owners. It's taken the better part of a year to get this thing back in shape.
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:rolleyes:
 
JAWS said:
If your trim is binding during flight, at any normal speed, it isn't safe or legal
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He isn’t flying it illegally.

With that being said, the trim cable could be slipping off the pulley causing it to rub against the trim bracket. Keep in mind, that if memory serves me correctly, the trim and elevator design is the same in the PA-32 and Arrow, so the same bracket that carries the trim line also carries the elevator cable. If the two rub together long enough it could cause friction damage to the elevator pulley and ultimately interference with the elevator control. Keep in mind this is worse case and likely not as extreme as what you describe, although I thought I’d mention it as food for thought. Wouldn’t want this to turn into a runway trim situation either. Best to ground the airplane and have someone knowledgeable take a peek, because this shouldn’t be happening.
 
I didn't write that the OP was flying illegally.

I did write that the trim system, if it binds in flight, is not safe or legal.

Ryanb said:
Best to ground the airplane and have someone knowledgeable take a peek, because this shouldn’t be happening.
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Exactly! :)
 
The cable is not slipping off the pulley, nor the drum, nor is anything rubbing. And, as EricVKX stated, this may be something that's not unusual for a PA28. Resistance will increase with speed. The human hand may not even feel the difference. My electric trim may have a loose clutch. And I don't get into this situation unless I have a situation in which I'm making a REALLY good ground speed - like a tailwind or cool, dry, dense air.

This airplane is not getting grounded for this. I fly this thing more than 200 hours/year and, thinking back, I've run into this since early on. It's a slight issue and I probably just didn't notice it before. I'm at the point with this airplane that I'm fixing picky little stuff that I probably only notice because I fly it all the time. If the IA didn't think it was an issue while he was standing in front of the plane, I'm not worried about ending up in a smoking hole yet. I just want to fix it.
 
paramax55 said:
I'm at the point with this airplane that I'm fixing picky little stuff that I probably only notice because I fly it all the time.
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I would not characterize pitch trim as a picky sort of thing, lol. But hey, that is just me.

paramax55 said:
If the IA didn't think it was an issue while he was standing in front of the plane
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Was he made aware of the issue at the last annual? Was he placed in the plane and flown in it to show him first hand what is going on? It is real easy to stand on the ground and make a judgement call with someone else's butt on the line. I would want to fly in the thing and see what is what. But hey, that is just me again! :)
 
Well, maybe I can benefit from your guy's expertise... how worn is my jack screw? How stiff does the trim get? How far out of adjustment is my clutch? How out of shape is my trim cable?
 
You've aready stated that the jackscrew has visible wear, trim gets stiff at higher airspeed, and you're not grounding the aircraft because of it. You're an idiot.
 
paramax55 said:
The cable is not slipping off the pulley, nor the drum, nor is anything rubbing. And, as EricVKX stated, this may be something that's not unusual for a PA28. Resistance will increase with speed. The human hand may not even feel the difference. My electric trim may have a loose clutch. And I don't get into this situation unless I have a situation in which I'm making a REALLY good ground speed - like a tailwind or cool, dry, dense air.

This airplane is not getting grounded for this. I fly this thing more than 200 hours/year and, thinking back, I've run into this since early on. It's a slight issue and I probably just didn't notice it before. I'm at the point with this airplane that I'm fixing picky little stuff that I probably only notice because I fly it all the time. If the IA didn't think it was an issue while he was standing in front of the plane, I'm not worried about ending up in a smoking hole yet. I just want to fix it.
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You sound like someone who is spending entirely too much time trying to rationalize and explain away something that you know isn’t right.

Your airplane is trying to tell you something. Best to listen to it even if you don’t listen to folks here.


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I'm much more of an idiot than dealing with a jack screw. The tires also have visible wear. The spark plugs aren't new, either. The mags are fresh, but I coupled them with used spark plugs! I'm a COMPLETE MORON!

Listen to the airplane telling me something? Didn't I come here asking for a part number? How quick we all are to bash without even seeing the airplane...
 
paramax55 said:
Well, maybe I can benefit from your guy's expertise... how worn is my jack screw? How stiff does the trim get? How far out of adjustment is my clutch? How out of shape is my trim cable?
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It is worn to the point of not being airworthy. It needs to be fixed before being flown again. It is not preventative maintenance. As shown above, McFarlane sells a complete kit.
The trim should run smoothly at all speeds. If it doesn't, it is binding somewhere.
Good luck.
 
paramax55 said:
I'm much more of an idiot than dealing with a jack screw. The tires also have visible wear. The spark plugs aren't new, either. The mags are fresh, but I coupled them with used spark plugs! I'm a COMPLETE MORON!

Listen to the airplane telling me something? Didn't I come here asking for a part number? How quick we all are to bash without even seeing the airplane...
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Binding under load is a common sign of worn threads. Now, how worn? Enough to raise the friction to where you can't move it properly. That's a bad sign. I have seen worn threads on other stuff, to the point that any significant load could easily strip the remaining metal and now we have a nut that moves freely up and down on the jackscrew. That's what happened to the Alaska Airlines airplane that crashed off the California coast years ago. Wrong lube, worn threads, no free-play inspections. In your Piper, a stripped nut is going to let the tab flop around and probably flutter, and flutter will tear the whole stabilator off the airplane within milliseconds.

Some of us have been around long enough to have read a lot of accident reports. Some really stupid stuff shows up in some of those. Worn-out parts are sometimes blamed for inflight failures.
 
Be cautious the Cessna 172 has takeoff trim problems as the default takeoff trim is NOT halfway up the wheel but rather a third.
 
Bradley W said:
Be cautious the Cessna 172 has takeoff trim problems as the default takeoff trim is NOT halfway up the wheel but rather a third.
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A) What does that have to do with his Piper?
B) Not all 172s are the same in this regard. Rig the aircraft to the proper trim settings by measurements.
C) What’s the “problem”?

Usually the bigger problem in a Cessna is a chunk missing out of the grooves on the trim wheel and the trim “jumping a track” like an old record player needle skipping, and then the indicator and the mark aren’t indicating properly. This would be found at a proper annual or 100 hour if the trim system is checked correctly and would be pretty noticible to all but the most overloaded or inattentive pilot.

But still has nothing to do with his Piper.
 
I fly a grumman and I believe the horiz stab and trim is the similiar. I have seen a similiar problem with my and a few other grummans flying in the yellow usually doing decents. I ususlly cruise 2450 at 10500 at 130kt and decend about 150kt. vne is about 160k. We grumman guys are good at quick fast decents and if the trim is not right it causes the similiar problem you may be encountering. Usually the problems you have been pm ing are normal for linkage and gears getting dirty or dry and this does help mask the problem we have found. Our problem is that the the center of the trim wheel in not properly centered or rigged correctly. If this is the problem the trim wheel will run out in the up or down position at low speeds like approach or take off. Additonally at higher speeds the trim movement is hardened and will not further trim. If the trim you have is the one simiilar to ours then the trim moves across the entire horizontal stab and moves in the direction of the trim. It is designed to harden up at limits for better control of PIO induced ocillations during landing operations. Most other aircraft have a small trim tab and it moves in the opposite direction...... Any way try and rig your trim correctly and this might fix the problem... One other poblem to look for is sometime a surface will flutter or get hard if the suface is not balanced correctly. There are weights inside these surfaces usually under the tip fairing and if you have had a paint job or other repair to the surface it will need to be rebalanced. Bty movable control surface part must be removed from aircraft to do the balancing but it does fix a hard control or flutter at high speeds ....... \

Robert Bowling
AP PPSEL
 
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