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jamesgrieco(at)yahoo.com
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 Posted: Sat Jan 28, 2012 5:51 am Post subject: Aileron weight missing |
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I think there is a misconception about the weight. Its specific job is as a mass balance about the hinge line. If you draw a free body diagram of the aileron with the weight and a chord wise cut of the aileron, the two masses balance around the hinge bracket. When you apply a vertical gust, the inertia load on both sides of the hinge is the same, and in the same direction, so the hinge bracket gets wacked with combined load of the aileron mass + the counter weight mass X the vertical gust factor. This means the aileron wouldn't rotate, but there would be a large bending moment at the junction of the weight to tube welded joint. With rust and continuous fatigue loading it could break. Since no aileron rotation occurs, the rod would not hit the stop.
An estimate of the Max load and rod stress seen can be found by determining the ultimate capability of the hinge bracket. Since I gather it did not fail, the bending moment applied to the rod would be 1/2 the bracket ultimate load capability X the length of the rod to the CG of the mass. The gust factor would be 1/2 the bracket ultimate load divided by the weight of the counter weight up to the weld.
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BARRY CHECK 6
Joined: 15 Mar 2011
Posts: 738
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| Posted: Sun Jan 29, 2012 8:28 am Post subject: Aileron weight missing |
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Hello James:
GREAT explanation.
The only exception to this would be that:
1 - If the plane is flying S&L the Weight would be inside the wing tip.
2 - The gust would have to be perpendicular to the bottom of the wing going straight up.
3 - And would have to enter the weight hole without any difference in pressure or speed when compared to the aileron the weight is attached to.
4 - Your explanation only accounts for One Wing & One Aileron... What about all the counter forces created by the other wing & aileron? As one aileron goes up the other is forced to go down.
But, YES, the force would be perpendicular to the torque tube and with a huge amount of rust the bracket may fail. I have never seen a bracket that bad... Rust - yes, worn bushings - yes, worn torque tube - yes, bent stops - yes, incorrectly installed stops - yes and RUSTED counter balance weights and mounting bolts - Most diffidently yes.
Barry
"Chop'd Liver"
On Sat, Jan 28, 2012 at 8:49 AM, James Grieco <jamesgrieco(at)yahoo.com (jamesgrieco(at)yahoo.com)> wrote:
[quote]--> TeamGrumman-List message posted by: James Grieco <jamesgrieco(at)yahoo.com (jamesgrieco(at)yahoo.com)>
I think there is a misconception about the weight. Its specific job is as a mass balance about the hinge line. If you draw a free body diagram of the aileron with the weight and a chord wise cut of the aileron, the two masses balance around the hinge bracket. When you apply a vertical gust, the inertia load on both sides of the hinge is the same, and in the same direction, so the hinge bracket gets wacked with combined load of the aileron mass + the counter weight mass X the vertical gust factor. This means the aileron wouldn't rotate, but there would be a large bending moment at the junction of the weight to tube welded joint. With rust and continuous fatigue loading it could break. Since no aileron rotation occurs, the rod would not hit the stop.
An estimate of the Max load and rod stress seen can be found by determining the ultimate capability of the hinge bracket. Since I gather it did not fail, the bending moment applied to the rod would be 1/2 the bracket ultimate load capability X the length of the rod to the CG of the mass. The gust factor would be 1/2 the bracket ultimate load divided by the weight of the counter weight up to the weld.
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teamgrumman(at)yahoo.com
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| Posted: Sun Jan 29, 2012 10:59 am Post subject: Aileron weight missing |
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Right, and the guy never added any inputs to the controls after the turbulence upset his attitude. Go fly behind another plane in its wake and try not to move the yoke. It can't be done.
"huge amount of rust the bracket may fail." --- aluminum doesn't rust.
From: FLYaDIVE <flyadive(at)gmail.com>
To: teamgrumman-list(at)matronics.com
Sent: Sunday, January 29, 2012 8:25 AM
Subject: Re: Aileron weight missing
Hello James:
GREAT explanation.
The only exception to this would be that:
1 - If the plane is flying S&L the Weight would be inside the wing tip.
2 - The gust would have to be perpendicular to the bottom of the wing going straight up.
3 - And would have to enter the weight hole without any difference in pressure or speed when compared to the aileron the weight is attached to.
4 - Your explanation only accounts for One Wing & One Aileron... What about all the counter forces created by the other wing & aileron? As one aileron goes up the other is forced to go down.
But, YES, the force would be perpendicular to the torque tube and with a huge amount of rust the bracket may fail. I have never seen a bracket that bad... Rust - yes, worn bushings - yes, worn torque tube - yes, bent stops - yes, incorrectly installed stops - yes and RUSTED counter balance weights and mounting bolts - Most diffidently yes.
Barry
"Chop'd Liver"
On Sat, Jan 28, 2012 at 8:49 AM, James Grieco <jamesgrieco(at)yahoo.com (jamesgrieco(at)yahoo.com)> wrote:
| Quote: | --> TeamGrumman-List message posted by: James Grieco <jamesgrieco(at)yahoo.com (jamesgrieco(at)yahoo.com)>
I think there is a misconception about the weight. Its specific job is as a mass balance about the hinge line. If you draw a free body diagram of the aileron with the weight and a chord wise cut of the aileron, the two masses balance around the hinge bracket. When you apply a vertical gust, the inertia load on both sides of the hinge is the same, and in the same direction, so the hinge bracket gets wacked with combined load of the aileron mass + the counter weight mass X the vertical gust factor. This means the aileron wouldn't rotate, but there would be a large bending moment at the junction of the weight to tube welded joint. With rust and continuous fatigue loading it could break. Since no aileron rotation occurs, the rod would not hit the stop.
An estimate of the Max load and rod stress seen can be found by determining the ultimate capability of the hinge bracket. Since I gather it did not fail, the bending moment applied to the rod would be 1/2 the bracket ultimate load capability X the length of the rod to the CG of the mass. The gust factor would be 1/2 the bracket ultimate load divided by the weight of the counter weight up to the weld.
===========
List" target="_blank">http://www.matronics.com/Navigator?TeamGrumman-List
===========
http://forums.matronics.com
===========
le, List Admin.
="_blank">http://www.matronics.com/contribution
===========
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