banner
banner

05 Aug 2021, 04:48 [ UTC - 5; DST ]


Stevens Aerospace (Banner)



Reply to topic  [ 12 posts ] 
Username Protected Message
 Post subject: Twin Cessna airframe shakes in flight
PostPosted: 07 Jul 2020, 16:11 
Offline


 Profile

Joined: 04/07/13
Posts: 420
Post Likes: +255
I am trying to find the cause of a longitudinal airframe shake that occurs in cruise flight in my Cessna 310. You can feel the cabin floor and see it in the panel.

It is not engine or prop related as far as I can tell. I've done mag checks, varied the prop speeds and even shut down each engine with no effect. The props have been dynamically balanced.

It appears to be related to airspeed and loading. When flying with my 200+ lb CFI it never happened and it seem to also not happen with full fuel (100gal) in the tip tanks. I've been told a loose gear door or flap could cause this, but I've had the plane on jacks and all doors are tight when the gear is retracted. Similarly, the elevator and aileron cable tensions have been checked and are within spec.

I am at my wits end (I know, I should have bought a Baron :) ). Does anyone have any ideas what could be causing this?


Top

 Post subject: Re: Twin Cessna airframe shakes in flight
PostPosted: 07 Jul 2020, 16:14 
Offline


User avatar
 WWW  Profile

Joined: 01/23/13
Posts: 4704
Post Likes: +2654
Company: Kokotele Guitar Works
Location: Albany, NY
Aircraft: C-182RG, C-172, PA28
Do you know anyone you trust to fly close formation to observe while in flight?

Do you feel it in the controls, too? I've heard of flutter occurring if something is broken or out of balance.

I wonder if the gear are sagging a bit in flight and causing this?


Top

 Post subject: Re: Twin Cessna airframe shakes in flight
PostPosted: 07 Jul 2020, 16:24 
Offline


 Profile

Joined: 04/07/13
Posts: 420
Post Likes: +255
Username Protected wrote:
Do you know anyone you trust to fly close formation to observe while in flight?

Do you feel it in the controls, too? I've heard of flutter occurring if something is broken or out of balance.

I wonder if the gear are sagging a bit in flight and causing this?

I have not flown in formation or tried a go-pro camera in flight yet. I plan on trying a camera next once I can figure out a safe and secure way to mount it.

The shake cannot be felt in the controls beyond that imparted on the yoke by the panel shake.

I can attest to the gear not sagging, as all three gear legs sit on hooks when retracted. Being fully mechanical, the gear up light would never illuminate unless the bell-crank completed its rotation and that would require the hooks transiting to and the legs lowered into their final retracted position. I am the AP/IA that annuals and checks the gear rigging each year.


Top

 Post subject: Re: Twin Cessna airframe shakes in flight
PostPosted: 07 Jul 2020, 16:27 
Offline


 Profile

Joined: 11/30/10
Posts: 2553
Post Likes: +2197
check the security of your bob weight. The elevator is counterbalanced with a bob weight in the nose.


Also. what is the frequency of this vibration. 1/sec? a hum? 10/sec.?


Top

 Post subject: Re: Twin Cessna airframe shakes in flight
PostPosted: 07 Jul 2020, 16:53 
Offline


User avatar
 Profile

Joined: 07/27/09
Posts: 1034
Post Likes: +478
Location: Chicago
Aircraft: E55
Check your wing root seals

_________________
-Tim Anderson

The only time you have too much fuel is when you're on fire


Top

 Post subject: Re: Twin Cessna airframe shakes in flight
PostPosted: 07 Jul 2020, 17:37 
Offline


 Profile

Joined: 10/07/18
Posts: 1375
Post Likes: +821
Location: Columbus, Ohio
Aircraft: Baron 58, Lear 35
The wing root panels will give a vibration if they don’t fit tight to the fuselage just aft of the wing leading edge. If you have the retractable landing lights in the tip, have you tried extending them in flight and see if the vibration changes? If you have boots, check that a section of boot isn’t loose along it’s trailing edge.


Top

 Post subject: Re: Twin Cessna airframe shakes in flight
PostPosted: 07 Jul 2020, 18:30 
Offline


 Profile

Joined: 04/07/13
Posts: 420
Post Likes: +255
Username Protected wrote:
check the security of your bob weight. The elevator is counterbalanced with a bob weight in the nose.


Also. what is the frequency of this vibration. 1/sec? a hum? 10/sec.?

No bob weight on the F model. This doesn't show up until the J model (see below)

The frequency is about 5 or so cycles per second. If I push the nose over or pull back into a climb the vibration stops until I once again enter straight and level flight.

Attachment:
BobWeight1.jpg
Attachment:
BobWeight2.jpg


Please login or Register for a free account via the link in the red bar above to download files.


Top

 Post subject: Re: Twin Cessna airframe shakes in flight
PostPosted: 07 Jul 2020, 18:43 
Offline



User avatar
 Profile

Joined: 07/22/14
Posts: 7099
Post Likes: +10289
Company: Mountain Airframe LLC
Location: Mena, Arkansas
I would check out the attachment of the horizontal stabilizer forward spar to the fuselage bulkhead.


Top

 Post subject: Re: Twin Cessna airframe shakes in flight
PostPosted: 07 Jul 2020, 19:43 
Offline


User avatar
 Profile

Joined: 01/19/16
Posts: 1556
Post Likes: +2065
Location: 13FA Earle Airpark FL/0A7 Hville NC
Aircraft: E33/152A/OV10/23-180
I had a strange shudder that affected the rudder on a nearly new Lake 200EP that I rebuilt after a T hangar crushed the tail during a tornado. Couldn’t figure it out. The rudder would sometimes randomly walk a bit. I finally fixed it with a couple finger loads of RTV at the horizontal stab seals. They looked fine but that fixed it.


Top

 Post subject: Re: Twin Cessna airframe shakes in flight
PostPosted: 07 Jul 2020, 20:15 
Offline



User avatar
 Profile

Joined: 07/22/14
Posts: 7099
Post Likes: +10289
Company: Mountain Airframe LLC
Location: Mena, Arkansas
Username Protected wrote:
I had a strange shudder that affected the rudder on a nearly new Lake 200EP that I rebuilt after a T hangar crushed the tail during a tornado. Couldn’t figure it out. The rudder would sometimes randomly walk a bit. I finally fixed it with a couple finger loads of RTV at the horizontal stab seals. They looked fine but that fixed it.

Fairings are important and there for more than one reason. I had a customer that had two damaged 58 Barons. One of them was a clean gear up, no wing damage, but fuselage damage and prop strikes. The other was a weird hi speed turn event that caused one main gear to fold inboard and the other outboard, and the nose gear didn't fold and no prop strikes.
I was hired to make one out of two. They were only 19 serial numbers apart, so all went very well until he got home and called me to mention the severe vibration and airframe shuddering on landing.
Turns out, those plastic fairings on each side of the nacelles do make a difference.


Top

 Post subject: Re: Twin Cessna airframe shakes in flight
PostPosted: 07 Jul 2020, 21:34 
Offline


 Profile

Joined: 11/30/10
Posts: 2553
Post Likes: +2197
Username Protected wrote:
check the security of your bob weight. The elevator is counterbalanced with a bob weight in the nose.


Also. what is the frequency of this vibration. 1/sec? a hum? 10/sec.?

No bob weight on the F model. This doesn't show up until the J model (see below)

The frequency is about 5 or so cycles per second. If I push the nose over or pull back into a climb the vibration stops until I once again enter straight and level flight.

Attachment:
BobWeight1.jpg
Attachment:
BobWeight2.jpg


Good to know. Thanks.

I wonder if the F "needs" a bob weight or if it was a cure for something.

Have you mentioned this to the Twin Cessna forum?

Top

 Post subject: Re: Twin Cessna airframe shakes in flight
PostPosted: 07 Jul 2020, 23:49 
Offline


 Profile

Joined: 04/07/13
Posts: 420
Post Likes: +255
Username Protected wrote:
I would check out the attachment of the horizontal stabilizer forward spar to the fuselage bulkhead.

Thanks Del! Will do. I was hoping you would chime in, as you are probably one of the most experience airframe experts on BeechTalk, and I believe you also own a 310. :cheers:


Top

Display posts from previous:  Sort by  
Reply to topic  [ 12 posts ] 




You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  

Terms of Service | Forum FAQ | Contact Us

BeechTalk, LLC is the quintessential Beechcraft Owners & Pilots Group providing a forum for the discussion of technical, practical, and entertaining issues relating to all Beech aircraft. These include the Bonanza (both V-tail and straight-tail models), Baron, Debonair, Duke, Twin Bonanza, King Air, Sierra, Skipper, Sport, Sundowner, Musketeer, Travel Air, Starship, Queen Air, BeechJet, and Premier lines of airplanes, turboprops, and turbojets.

BeechTalk, LLC is not affiliated or endorsed by the Beechcraft Corporation, its subsidiaries, or affiliates. Beechcraft™, King Air™, and Travel Air™ are the registered trademarks of the Beechcraft Corporation.

Copyright© BeechTalk, LLC 2007-2021

.McPeck_85x50.jpg.
.Rocky-Mountain-Turbine-85x100.jpg.
.jandsaviation-85x50.jpg.
.Marsh.jpg.
.ABS-85x100.jpg.
.chairmanaviation-85x50.jpg.
.blackhawk-85x100-2019-09-25.jpg.
.bkool-85x50-2014-08-04.jpg.
.priori-85x50.jpg.
.avidyne-85x50-2017-11-22.jpg.
.westsky.jpg.
.airmart-85x150.png.
.jaair-85x100.jpg.
.truecourse.jpg.
.Microkit_85x50.png.
.echelon-85x50.png.
.planelogix-85x100-2015-04-15.jpg.
.komn-85x50.png.
.greenwich-85x50-2020-08-10.jpg.
.Expert_Aircraft_Solution_85x50.jpg.
.MountainAirframe.jpg.
.kingairacademy-85x100.png.
.geebee-85x50.jpg.
.centex-85x50.jpg.
.southseas-85x50-2021.png.
.carpenter-85x50.png.
.avionwealth-85x50.png.
.cav-85x50.jpg.
.dshannon.jpg.
.temple-85x100-2015-02-23.jpg.
.Davis_Aviation_85x50.jpg.
.SCA.jpg.
.kingairdom.jpg.
.wilco-85x100.png.
.methodseven-85x50.jpg.
.dbm.jpg.
.airpower-85x50.jpg.
.SierraTrax_85x50.jpeg.
.midwest2.jpg.
.stanmusikame-85x50.jpg.
.heartlandsm.jpg.
.kadex-85x50.jpg.
.tempest.jpg.
.pdi-85x50.jpg.
.gallagher_85x50.jpg.
.instar.jpg.
.daytona.jpg.
.avionicssource-85x50.jpg.
.Foreflight_85x50_color.png.
.camguard.jpg.
.STLAir_85x50.jpg.
.avfab-85x50-2018-12-04.png.
.tat-85x100.png.
.aircraftassociates-85x50.png.
.Flaremeter_85x50_v2.png.
.wat-85x50.jpg.
.dynon-85x50.jpg.
.bpt-85x50-2019-07-27.jpg.
.garmin-85x200-2021-07-26.jpg.
.saint-85x50.jpg.
.aviationdesigndouble.jpg.
.Wentworth_85x100.JPG.
.Latitude.jpg.
.ei-85x150.jpg.
.aspen-85x100.jpg.
.AAI.jpg.
.rtc-85x200.jpg.
.concorde.jpg.
.KalAir_Black.jpg.
.Genesys_85x50.jpg.
.EagleFuelCellsTriple.jpg.
.jetacq-85x50.jpg.
.traceaviation-85x150.png.
.CiESVer2.jpg.
.ps_engineering.gif.