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dvonruden(at)generalequip
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 Posted: Tue Jul 26, 2011 7:37 pm Post subject: Vibrations in Flight |
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I realize this list is directed mostly to the four seat Grumman aircraft, but I have an issue with my AA-1B that I am searching for some insight. Hope someone can help me.
I have a 1974 AA-1B that I purchased new while in college. Stock O235. I’ve owned it since new. I am the only person that flies it. Approximately 850 hours total time. All four cylinders have been topped in recent years. Here’s some additional information:
<![if !supportLists]>1) <![endif]>Just completed a very thorough annual inspection.
<![if !supportLists]>2) <![endif]>New mags approximately 5 years ago.
<![if !supportLists]>3) <![endif]>New ignition harness last year.
<![if !supportLists]>4) <![endif]>New plugs.
<![if !supportLists]>5) <![endif]>Carburetor was rebuilt by a certified shop with the new composite float installation.
<![if !supportLists]>6) <![endif]>Just checked cylinders for excessive valve guide wear or sticking…none detected.
<![if !supportLists]>7) <![endif]>Installed an EDM 700 a few years ago. All cylinders normally run within 20 to 80 degrees F (depending upon OAT and RPM) in terms of cylinder heard and exhaust temps. Number three will run maybe 20 to 40 degrees F higher at times, but later during the flight these temps are “reduced” to the other cylinder values. With proper leaning, all cylinders run very even temperatures.
<![if !supportLists]> <![endif]>Prop was overhauled by a certified shop two years ago.
<![if !supportLists]>9) <![endif]>Engine exhaust is a consistent, light brown.
<![if !supportLists]>10) <![endif]> No abnormal oil consumption.
<![if !supportLists]>11) <![endif]>Burn 100 LL with a little Marvel thrown in from time to time.
<![if !supportLists]>12) <![endif]> New engine mounts two years ago.
I know this aircraft very well, and I am now experiencing a strange set of vibrations from the rudder pedals. Almost a impulse type of force like you would experience while the engine is at low idle speed. Nothing with huge amplitude, but it is noticeable. In the past, you could rest your feet on the rudder pedals and the vibration was constant. Not now…you can feel an “impulse” type of vibration. It’s not constant, as it comes and goes while in flight.
Tonight, I felt an impulse vibration from the pedals right after liftoff. I did not have time to glance at the EDM 700, but it lasted less than a second. It got my attention. The EDM read normal during my local flight.
At the risk of coming across as some type of nut case, I’m wondering what is going on. Is my imagination getting to me? Anyone have any ideas besides seeing shrink? I have a number of aircraft and insist on high maintenance. This aircraft has always been well maintained.
Thank for your help.
Dennis Von Ruden
President
[img]cid:image003.jpg(at)01CC4BE4.3E4BBF40[/img]
620 Alexander Drive S.W.
P.O. Box 334
Owatonna, MN 55060
800.533.0524 voice
+5074515510 voice
877.344.4375 fax
+5074515511 fax
dvonruden(at)generalequip.com (dvonruden(at)generalequip.com)
www.generalequip.com
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teamgrumman(at)yahoo.com
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| Posted: Tue Jul 26, 2011 10:26 pm Post subject: Vibrations in Flight |
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Dennis,
This this is for anything you want to talk about. Corvettes? Direct injection? Vibrations?
Of the 3 AA1s I've worked on, only one had a weird rudder feel. I never did find it. I thought it was the rudder bearings at first. Then I looked at the elevator attachments. Then the bungy set up. Then the flap and aileron bearings.
One thing . . . . . do you have wheel pants? Or the gear leg fairings? Look for something vibrating there.
Look for a cracked engine mount.
Gary
Sent from my iPad
On Jul 26, 2011, at 8:34 PM, "Dennis Von Ruden" <dvonruden(at)generalequip.com (dvonruden(at)generalequip.com)> wrote:
[quote]
I realize this list is directed mostly to the four seat Grumman aircraft, but I have an issue with my AA-1B that I am searching for some insight. Hope someone can help me.
I have a 1974 AA-1B that I purchased new while in college. Stock O235. I’ve owned it since new. I am the only person that flies it. Approximately 850 hours total time. All four cylinders have been topped in recent years. Here’s some additional information:
1) Just completed a very thorough annual inspection.
2) New mags approximately 5 years ago.
3) New ignition harness last year.
4) New plugs.
5) Carburetor was rebuilt by a certified shop with the new composite float installation.
6) Just checked cylinders for excessive valve guide wear or sticking…none detected.
7) Installed an EDM 700 a few years ago. All cylinders normally run within 20 to 80 degrees F (depending upon OAT and RPM) in terms of cylinder heard and exhaust temps. Number three will run maybe 20 to 40 degrees F higher at times, but later during the flight these temps are “reduced” to the other cylinder values. With proper leaning, all cylinders run very even temperatures.
Prop was overhauled by a certified shop two years ago.
9) Engine exhaust is a consistent, light brown.
10) No abnormal oil consumption.
11) Burn 100 LL with a little Marvel thrown in from time to time.
12) New engine mounts two years ago.
I know this aircraft very well, and I am now experiencing a strange set of vibrations from the rudder pedals. Almost a impulse type of force like you would experience while the engine is at low idle speed. Nothing with huge amplitude, but it is noticeable. In the past, you could rest your feet on the rudder pedals and the vibration was constant. Not now…you can feel an “impulse” type of vibration. It’s not constant, as it comes and goes while in flight.
Tonight, I felt an impulse vibration from the pedals right after liftoff. I did not have time to glance at the EDM 700, but it lasted less than a second. It got my attention. The EDM read normal during my local flight.
At the risk of coming across as some type of nut case, I’m wondering what is going on. Is my imagination getting to me? Anyone have any ideas besides seeing shrink? I have a number of aircraft and insist on high maintenance. This aircraft has always been well maintained.
Thank for your help.
Dennis Von Ruden
President
<image003.jpg>
620 Alexander Drive S.W.
P.O. Box 334
Owatonna, MN 55060
800.533.0524 voice
+5074515510 voice
877.344.4375 fax
+5074515511 fax
dvonruden(at)generalequip.com (dvonruden(at)generalequip.com)
www.generalequip.com
--------------------------------------------------------------------------------
ALL INFORMATION IN THIS EMAIL, AND/OR ATTACHMENT(S) IS CONFIDENTIAL. If you received this e mail in error, and are not the recipient(s) or responsible for receiving this e mail for the recipient, please inform the sender immediately, delete the e mail and any attachment(s) associated.
This email has been scanned by Barracuda - Email Security System.
[b]
| | - The Matronics TeamGrumman-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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andy747(at)charter.net
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| Posted: Wed Jul 27, 2011 2:55 am Post subject: Vibrations in Flight |
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My first thought is wheels.....especially since you noticed it right after lift off one time. I have had this issue and stopping the wheel rotation with brakes identified it and solved the problem. If the bearings are too loose the wheels could start to rotate at any point during the flight. Also the tension on the nose wheel could be low letting the nose wheel pivot in flight and disturb the airflow. Also check wheel pant attachment if you have them.
A Minnesota story for you...
Mark Sheerer, who owns PS Engineering and builds the popular PS audio panels learned to fly in college in Mn and later bought the AA1 that he soloed in. I purchased it from him after he had owned it for 19 years....I traded from there to a Tiger. Let me know if you want to sell yours !!!
Good luck....
Andy Thomas, A&P, ATP, CFI
[quote] ---
| | - The Matronics TeamGrumman-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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