Static Wing Load Testing of Old Wooden Glider Wings

Jeff, Austrailian Alan Patching is an world renowed expert on the
effect of aging on both wood and fiberglass glider structures.

Alan has been performing long term fatique testing for fiberglass
gliders since the early 70's. My recollection is that they had not
discovered any finite lifetime limits to date for fiberglass
construction.

Alan received the 2006 Lilienthal Gliding Medal for, among many other
contributions, his long study of lifetime limits in FGRP structures.

If you have access to Technical Soaring you can find a number of
Alan's articles. You may find something useful there on wood
structures.

[BTW, we do have access at TSA to past issues of Technical Soaring.]

=================
Volume I, Number 2, October, 1971
C.A. Patching, Establishing the Structure Integrity of Aging Gliders
[Construction], page 17

Volume VI, Number 3, March, 1981
JG.P. Esson and C.A. Patching, Fatigue Life Considerations for Gliders
Operated in Australia, page 10

Volume 15, Number 4, October, 1991
C.A. Patching and L.A. Wood, Fatigue Testing of A GFRP Glider
[Construction], page 100

Volume 22, Number 1, January, 1998
C.A. Patching and L.A. Wood, Further Fatigue Testing of a Glass Fiber
Reinforced Plastic Glider Wing [Aerodynamics\Testing], page 11
=============================

On Sun, 18 Dec 2016 17:51:36 -0800 (PST), LongJourney
wrote:

I'm restoring a 1963 Std Austria and trying to decide the risks and merits of load testing the wings. I can't find anything definitive on the web, at least nothing that doesn't get contradicted by some other source.

My concern is that load testing may damage the wings in an undetected way. OTOH, I don't want to find out that the spar already has some undetected damage by spotting one wing departing the aircraft while I'm flying it.

Opinions are welcome, but if anyone knows of an AC or other documentation that may shed light on this topic, I would greatly appreciate that information.

Thanks!

Jeff

On Sunday, December 18, 2016 at 7:51:39 PM UTC-6, LongJourney wrote:
I'm restoring a 1963 Std Austria and trying to decide the risks and merits of load testing the wings. I can't find anything definitive on the web, at least nothing that doesn't get contradicted by some other source.

My concern is that load testing may damage the wings in an undetected way. OTOH, I don't want to find out that the spar already has some undetected damage by spotting one wing departing the aircraft while I'm flying it.

Opinions are welcome, but if anyone knows of an AC or other documentation that may shed light on this topic, I would greatly appreciate that information.

Thanks!

Jeff

Thanks for all of the great information. I'll get with my AI and see what he wants to do.

Jeff

On Tuesday, December 20, 2016
On one last note you might find useful,
The wing construction of the Austria including my SHK-1 did not use a conventional spar design. they employ a typical main spar to about two thirds out from the root, transitioning loads to multiple 'skin' longerons with rib structures almost every 4-6 inches resulting in a structure which may not respond to Bob K's "ladder" device protecting the wing from point loads. I.e.. No doubt a wing blueprint would reveal a tactic to safely load the wing.

Good luck,
Scott, N8915, formerly restored N1521

On Tuesday, December 20, 2016 at 9:49:22 AM UTC-6, Scott Williams wrote:
On Tuesday, December 20, 2016
On one last note you might find useful,
The wing construction of the Austria including my SHK-1 did not use a conventional spar design. they employ a typical main spar to about two thirds out from the root, transitioning loads to multiple 'skin' longerons with rib structures almost every 4-6 inches resulting in a structure which may not respond to Bob K's "ladder" device protecting the wing from point loads. I..e. No doubt a wing blueprint would reveal a tactic to safely load the wing..

Good luck,
Scott, N8915, formerly restored N1521

Thanks, Scott!

On Monday, December 19, 2016 at 7:04:54 PM UTC-7, Bob Gibbons wrote:
Jeff, Austrailian Alan Patching is an world renowed expert on the
effect of aging on both wood and fiberglass glider structures.

Alan has been performing long term fatique testing for fiberglass
gliders since the early 70's. My recollection is that they had not
discovered any finite lifetime limits to date for fiberglass
construction.

Alan received the 2006 Lilienthal Gliding Medal for, among many other
contributions, his long study of lifetime limits in FGRP structures.

If you have access to Technical Soaring you can find a number of
Alan's articles. You may find something useful there on wood
structures.

[BTW, we do have access at TSA to past issues of Technical Soaring.]

=================
Volume I, Number 2, October, 1971
C.A. Patching, Establishing the Structure Integrity of Aging Gliders
[Construction], page 17

Volume VI, Number 3, March, 1981
JG.P. Esson and C.A. Patching, Fatigue Life Considerations for Gliders
Operated in Australia, page 10

Volume 15, Number 4, October, 1991
C.A. Patching and L.A. Wood, Fatigue Testing of A GFRP Glider
[Construction], page 100

Volume 22, Number 1, January, 1998
C.A. Patching and L.A. Wood, Further Fatigue Testing of a Glass Fiber
Reinforced Plastic Glider Wing [Aerodynamics\Testing], page 11
=============================

On Sun, 18 Dec 2016 17:51:36 -0800 (PST), LongJourney
wrote:

I'm restoring a 1963 Std Austria and trying to decide the risks and merits of load testing the wings. I can't find anything definitive on the web, at least nothing that doesn't get contradicted by some other source.

My concern is that load testing may damage the wings in an undetected way. OTOH, I don't want to find out that the spar already has some undetected damage by spotting one wing departing the aircraft while I'm flying it.

Opinions are welcome, but if anyone knows of an AC or other documentation that may shed light on this topic, I would greatly appreciate that information.

Thanks!

Jeff

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Frank Whiteley