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Author Topic: Secondary Wing Spar  (Read 897 times)

Offline earl1937

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Secondary Wing Spar
« on: December 10, 2013, 01:08:35 PM »
 :airplane: Asked a question about wing spars the other night and was surprised to find that most guys didn't know what the secondary wing spar on a B-17, F4U, P-51, T6, P-47 or a B-29 was far! All of these aircraft had one, as most other aircraft, do you know what its for?
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Offline Valkyrie

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Re: Secondary Wing Spar
« Reply #1 on: December 10, 2013, 02:18:14 PM »
Landing gear and twisting loads. The P-47 I believe has three, the auxilliary spar is to carry the landing gear loads.
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Offline MK-84

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Re: Secondary Wing Spar
« Reply #2 on: December 10, 2013, 08:43:47 PM »
I always assumed it was to make sure the wings stay firmly attached to the fuselage.
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Offline J.A.W.

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Re: Secondary Wing Spar
« Reply #3 on: December 10, 2013, 09:44:52 PM »
Unless folded, like when parked on a CV..
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Offline Charge

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Re: Secondary Wing Spar
« Reply #4 on: December 11, 2013, 01:50:32 AM »
Torsional stiffness.

-C+
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Offline asterix

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Re: Secondary Wing Spar
« Reply #5 on: December 11, 2013, 09:43:35 AM »
Quote from: earl1937 on December 10, 2013, 01:08:35 PM
:airplane: Asked a question about wing spars the other night and was surprised to find that most guys didn't know what the secondary wing spar on a B-17, F4U, P-51, T6, P-47 or a B-29 was far! All of these aircraft had one, as most other aircraft, do you know what its for?
How dare they come online without knowing the purpose of a secondary wing spar. Looks like someone has been sleeping during their 6th grade aeronautical engineering lesson in middle school.
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Offline earl1937

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Re: Secondary Wing Spar
« Reply #6 on: December 12, 2013, 05:28:16 PM »
Quote from: asterix on December 11, 2013, 09:43:35 AM
How dare they come online without knowing the purpose of a secondary wing spar. Looks like someone has been sleeping during their 6th grade aeronautical engineering lesson in middle school.
:airplane: The Secondary Spar plays an important part in the structural integrity of the wing! It is installed in the rear section of the wing edge, to protect the wing from "flexing" during operation of the flaps during flight.
Unlike the main spar, the secondary spar usually doesn't go through the fuseledge to connect both sides. Where the wing flaps,, engine mounts and landing gear transition area, there are extra strong wing ribs, extra gussets to strengthen the whole assy.
The VFe of any aircraft is usually based on stress tests during development to see where the maximum speed load is before the rear or secondary spar fails.
Ran across this the other day and thought it might be interesting to some:



Associate Editor taking a break!
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Offline J.A.W.

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Re: Secondary Wing Spar
« Reply #7 on: December 12, 2013, 05:55:20 PM »
Dang! & no wonder those `38 jocks were complainin' 'bout it being like ridin' in a freezer..
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Offline drgondog

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Re: Secondary Wing Spar
« Reply #8 on: January 09, 2014, 11:27:03 AM »
Wing spars are placed to a.) absorb bending and torsion loads, and b.) transmit bending and torsion loads to the Fuselage.

The structures team looks at aero lift loading, loads from external stores,torsion from aileron and flap deflections and landing gear loads.

Usually, the primary spar is near the Center of Pressure, as a function of chord location, then look to flap hanging structure.  The landing gear is usually placed as close as possible to main spar.

Secondary spars also included stiff structure at leading edge of the wing.  The Spit had all three for example.

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Offline Arlo

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Re: Secondary Wing Spar
« Reply #9 on: January 09, 2014, 01:37:07 PM »
That dog is obviously missing it's secondary spar.  ;)
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Offline GScholz

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Re: Secondary Wing Spar
« Reply #10 on: January 09, 2014, 03:14:57 PM »
Good post Earl!  :aok
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