Cherokee 140 shutter

[corjulo]

Plane is on its way to mechanic but I would like some suggestions. A Old Cherokee 140 with a noticeable vibration at 4000 to 5500 RPMs. We haven't has this plane too long so it may have always been there. Prop balance, engine??

Also, opinions on the TPC additive? This engine has the auto gas modification, flow about 20 hour a month but always burn 100LL

 

[Anthony]

Plane is on its way to mechanic but I would like some suggestions. A Old Cherokee 140 with a noticeable vibration at 4000 to 5500 RPMs. We haven't has this plane too long so it may have always been there. Prop balance, engine??

Also, opinion on the TPC additive. This engine has the auto gas modification

Could be a lot of things, but a dynamic prop balancing may be in order. Have the engine mounts checked also. 4000 - 5500 RPMs? Do you mean 2400 - 2550?

TCP is good if your using 100LL, but don't keep the can in the plane when you fly. Its very dangerous stuff. Obviously you don't need it for unleaded mogas.

 

[ScottM]

A Old Cherokee 140 with a noticeable vibration at 4000 to 5500 RPMs.

Wow! Cherokees 140s really spin the prop that fast? I have never flown one but that seems almost twice as fast as every other plane I have ever flown.

 

[corjulo]

Could be a lot of things, but a dynamic prop balancing may be in order. Have the engine mounts checked also. 4000 - 5500 RPMs? Do you mean 2400 - 2550?

TCP is good if your using 100LL, but don't keep the can in the plane when you fly. Its very dangerous stuff. Obviously you don't need it for unleaded mogas.

OY

5000 WOULD GENERATE A VIBRATION. I MEAN 2400 TO 2500

 

[mikea]

I think if you use the proper ground leaning procedures you don't need the TCP. In my case I could tell when a plug was fouled because I have an engine analyzer. After getting the top overhaul - actually many flying hours after getting the top overhaul - the fouling stopped. I had a bad plug once in the meantime. The plugs were getting fouled by oil and not lead.

I went through a couple cans of TCP with no results I could put my finger on.

I also got in the habit of leaning like mad on the ground.

I once found the directions at Lycoming, but the gist is you set idle rpms, lean slowly until the RPMs climb a bit and then begin to drop. That will be WAY lean. Leave the mixture there until run-up, set it the same as it was after run-up, and of course go full rich on takeoff.

The idea is also to have it be so lean you can't forget to set full rich on takeoff because otherwise the engine will stumble.

 

[EdFred]

Since when does Piper make a camera?


shutter (n)

A mechanical device of a camera that controls the duration of a photographic exposure, as by opening and closing to allow light coming through the lens to expose a plate or film.

shudder (v)

To vibrate; quiver

 

[ScottM]

Engine mount pad?

 

[corjulo]

Talked with the mechanic. All the obvious stuff checked out. Mounts are good, nothing loose. Ran it at 2400 on the ground and found nothing. Next step it to take the mechanic up for a test flight.

 

[Richard]

There was a Warrior I flew that precisely at 1950 it would vibrate. Also when passing through 2400 or so. Both cases it was the RPMs setting up a harmonic with the prop.

 

[RotaryWingBob]

My Archer did something similar after I had to replace the prop (it couldn't be overhauled because too many nicks had been filed down over the years). When I took the first flight with the new prop everything was great until I reduced throttle to about 2100 for the descent. I got a strong vibration as soon as I pulled the throttle aft. I thought maybe I had carb ice, but heat didn't do anything, and the engine seemed to be producing normal power.

We tried balancing which helped a little but didn't stop the vibration. The prop shop suggested moving the prop 180 degrees. We removed the balancing weights, re-indexed the prop and the vibration went away.

 

[Stache]

Engine vibrations can be caused by many things so I will list a few. But the first thing to know has the engine had a prop strike, accident/incident or repairs?

1. Propeller spinner backing plate cracked/broken.
2. Propeller spinner misaligned.
3. Propeller bolts loss of torque or uneven torque.
4. Improper overhaul.
5. Loose retaining nut.
6. Propeller out of track (bent) or missing tracking shim.
7. Propeller out of balance.
8. Forward crankshaft bearing and seal worn out.
9. Improper installation position in relation to the crankshaft (this happens).
10. Check all the engine mounts for cracks or broken.


Some people use the propeller as a handhold to pull the aircraft around with on the ground. This will cause out of track and may damage the front nose seal. If a propeller has be repitched it may of returned to the original pitch check your records. This problem cannot be fixed so replace the prop,

If vibration persist after checking all of the above causes listed above, there may be a problem with an interaction between the propeller and the engine cowling. This can be reduced by removing the propeller from the hub or flange and shifting its position one bolt hole. Reinstall the propeller and perform an operational check to determine if the vibration level has decreased. This procedure may be repeated until the position of least vibration is determined. Remember to consult the appropriate repair manual to determine if a specific propeller position is called for before attempting this procedure.

Stache

 

[flyingcheesehead]

Some people use the propeller as a handhold to pull the aircraft around with on the ground. This will cause out of track and may damage the front nose seal.

Stache,

Can you elaborate? I've wondered why some props have a Do Not Push/Pull type sticker on or near them, considering how they are pulling the airplane for the entire duration of the flight... Is it OK (or at least more so) if you're applying symmetric pressure (ie hands equidistant from center)?

How else can someone move an average Piper without a tow bar? Cessnas at least have struts to push on.

Thanks,

Kent

 

[Joe B]

How else can someone move an average Piper without a tow bar? Cessnas at least have struts to push on.

To go forward push with your palms on the upper surface of one of the wings, from behind. If solo push on the wing walk, if dual push on the wing over the mains. For reverse push on the leading edge. When I have helpers that's where I always send them. I'm up front with the tow bar steering <g>.

Regards,
Joe

 

[corjulo]

To go forward push with your palms on the upper surface of one of the wings, from behind. If solo push on the wing walk, if dual push on the wing over the mains. For reverse push on the leading edge. When I have helpers that's where I always send them. I'm up front with the tow bar steering <g>.

Regards,
Joe

Anywhere on the leading edge?

 

[gismo]

Anywhere on the leading edge?

When pushing my plane backwards I try to line hands up with ribs so the pusher doesn't dent the leading edge. On the Baron there's a perfect spot to push between the nacelle and fuselage on either wing. It's an especially good spot as there's no de-ice boot there. For going forward, I have no choice besides the props (and towbar of course). There is simply no place on the trailing edge of the wing that you can apply much force.

I do believe that as long as you pull from a point on the prop right next to the spinner, you can't really damage the engine or prop as the force a human can exert there is pretty small compared to the forces in flight. And if anyone thinks the prop load on the crankshaft is always longitudinal (in line with the shaft) I suggest they consider what happens when they pitch the airplane up or down with the prop turning high RPM. The gyroscopic force is significant. In addition everytime you feel a 1+G bump the weight of the prop is applying a lot of force perpendicular to the shaft.

OTOH, pulling on the tip or even the middle of a blade does give a person a pretty good lever arm and should be avoided.

 

[jason]

in towards the wing root is always better, but I can't imagine pushing anywhere on the leading edge would damage anything (in a piper single that is, I can't speak for other low-wing planes).

Just make sure you're not pushing on plastic wing tips or the stall warning tab.

 

[AirBaker]

Since when does Piper make a camera?


shutter (n)

A mechanical device of a camera that controls the duration of a photographic exposure, as by opening and closing to allow light coming through the lens to expose a plate or film.

shudder (v)

To vibrate; quiver

"She's starting to shimmy..."

"She's starting to... "