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Vibration I Can't Identify

Steve Pierce

Steve Pierce

BENEFACTOR
Graham, TX
I have a vibration in my Pacer that I can't identify. Seems to be smoother at a higher rpm but it also seems to come and go in the same flight. My trip to New Holstein it was very evident. I found out when I got home I had a cracked cylinder. Pulled all 4 and replaced with some 700 hr. Millineums I had after going through them. I swapped the prop with Cathy's Tri-Pacer which is the smae prop and pitch, stayed the same. I duct tapped everything that felt it could possibly be loose on the airframe and no change. I feel it in my feet more than anything. I have been over the engine mount, baffles, etc. with no luck. My next step is to pull her firewall forward off and install on mine and see what happens. :eek:
 
Ehaust touching cowl when loaded in flight?

Stiff hose or ground or start cable?

Mount rubber wore threw bolt tapping?
 
Control cable tensions?
Streamlined tail wires and not lined up quite right?
Try trimming off neutral and hold control pressure. Does it make any difference?
Screw missing in tail inspection plate?
 
Steve, do you know why a pilot/mechanic and a new puppy are different?
I'll tell you, the puppy stops whining after 6 weeks :)

Tim
 
Steve,

Have you looked out at the tires? My 850's on the 180 vibrate like crazy at certain speeds....

sj
 
No certain speed or flight attitude. Very random. I have been over the entire airframe and can't find anything loose or missing. Muffler was just off and inspected. I did consider removing the Bushwheels momentarily to see if that makes a difference. I can't see them from inside the airplane. If that doesn't change anything I am going to replace the engine mount rubbers which look good and then see what happens. Very aggravating problem. I have flown lots of airplanes and this just doesn't feel right.
 
Steve,

I know a mechanic here in Kansas City who might could look at it for you... :lol:

It might take a while...

sj
 
Don't remove them, just lock them up with the parking brake or equal. Don't forget to undo them prior to landing. Make a big note on the dash just in case. they would be closer to the prop wash than on other planes? If not them I'd stick to the rotating assembles.
 
Steve Pierce said:
And SJ reminds me of taxing 994CC with the parking brake on. Takes an aweful lot of power. :oops:
Click to expand...

Fortunately, with 180hp you can pull it off...

sj
 
when its vibrating does changing power settings make it go away or change the frequency? Is it a hi or low frequency vibration or Do you feel it in the rudder pedals or with feet flat on the floor? Does kicking the rudder or pulling on the yoke make it change?
 
All kidding aside (for now) maybe an in flight tail wheel woogety-woogety? I have had mine vibrate after landing out and it felt really strange...it quit when I landed and pulled the grass out of it. I have also seen others vibrating in the slip stream in flight, so maybe time for a close formation/inspection flight, I'll send SteveE :eek: right down.
 
Steve,

Years ago, one of the company C 185s developed a slight vibration. Seemed to be coming from the engine, but was intermittent, and pretty subtle at that.

Turned out that one leg of the engine mount was broken, completely through. Amazingly, it was REALLY hard to see the break.

I would uncowl and take a REALLY close look at the engine mount and all associated pieces.

MTV
 
What MTV said!!! I just found the same thing as we were doing my annual today. A vib that was very hard to define, it wasn't always the same strength. I'll post pictures when I get the mount off the engine.

Steve
 
I've been over the mount with a mirror but will look again. Talked to Clyde Smith today about something else and mentioned my problem. He said Piper had a vibration problem they finally narrowed down to a bad batch of alternator belts. I'm gonna look at that as well. Thanks and keep them coming.
 
In a Comanche I had the tailpipe brace was touching the motor mount. It would come and go. I checked a lot of stuff before I found it.

As an aside, it turned up on the flight home from Vermont where I had to leave the airplane on 9/11. When GA was openned to IFR about a week or so later, I went and got it. But once I go home to LI, VFR was still prohibited, so everytime I thought I found something I had to file an IFR, go up and when I still had the vibration, I would tell them I wanted to go back. Tracon got a little tired of me after the second or third try.

Rich
 
Take a good look at the clusters on the airframe where your engine bolts to the airframe. Top left is most common to crack.
 
bearsnack said:
Take a good look at the clusters on the airframe where your engine bolts to the airframe. Top left is most common to crack.
Click to expand...

Seen 3 there, at firewall or at window top left.....
 
Steve, if the airframe checks out good, check the insides of your knees. :)
 
Same thing just happened to me. My wife and I flew out of Midland yesterday and just after leveling off, our 1953 super cub (150 horse) started to vibrate. She was in the back and weighs 110, had about 30 lbs in the cargo area so I don't think it was the loading. Prop seems fine, exterior seems fine. Have not been able to look at the motor mounts yet but it was coming from in front of the firewall.
We did a normal takeoff with only slight angle turns and very slow acceleration on roll due to plenty of runway. The serious vibration seemed to ease but was still abnormal when we Landed in Lubbock, seems I might have a serious (expensive) problem....!?
 
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