Re: [Aus-soaring] Wing frequency Procedure

Tue, 01 Dec 2015 01:15:13 -0800


My question would be has the wing frequency test ever proved anything?

Within  the GFA at least there should be a record of tests that have been failed: a significant change noted, and more detailed inspecrion been required, beyond that within club innspectors resources.

So GFA, apart from adding to the historic description of how to do wing frequency check, what data is available to prove the effectiveness  of the test.


Alan Wilson 

M_12145
Sent from Samsung Galaxy tab S

PS. Idid a wing frequency test lasr month. And a member pr9duced a device placed it on the wing and counted over 2 minutes, much more accurate than a manual count over 15 seconds


-------- Original message --------
From: Christopher McDonnell <[email protected]>
Date: 01/12/2015 18:25 (GMT+10:00)
To: "Discussion of issues relating to Soaring in Australia." <[email protected]>
Subject: Re: [Aus-soaring] Wing frequency Procedure

Probably the same as arthritis mobility Mike which the members are familiar with. Smile
 
Sent: Tuesday, December 01, 2015 4:41 PM
Subject: Re: [Aus-soaring] Wing frequency Procedure
 
I wonder if/how the frequency varies with temperature with glass gliders????


Mike





At 04:18 PM 12/1/2015, you wrote:

From the old MOSP 50. Section 3 on Form 2sÂ

 ============================================Â

3-2-2

(3) Wing Frequency Check

All new sailplanes delivered now have stated in their airworthiness documentation the natural vibrational frequency of at least the wings.

We all know that a drinking glass will “ring” when tapped, but if it is cracked it will be “dead”. Similarly our sailplane structure will respond to internal damage, loos wing root fittings etc by changing the frequency at which it wants to vibrate.

Clearly it will be important to KNOW the frequency of the structure when new and keep track of any natural lowering of this value with age such that a sudden change can be detected and become meaningful.

Â

WHEN:

At each Form 2 and after any air load or ground load incident particularly heavy landings and ground loops.

HOW:

With the sailplane sitting on its undercarriage, tyres at correct pressure, on a paved surface, empty, wings level, gently grasp one wing tip and shake it up and down. The wing will flex at a steady rate. It will find its own frequency and it is next to impossible for you to change it. Using a suitable watch, time the natural frequency, a complete cycle being UP and DOWN. This value should then be compared to what was found last time or what is specified for that sailplane.

Â

As a guide only, some typical values:-

F.R.P ……  Â   135 cycles per minute

Wood  ……3">    180 cycles per minute

Metal  ……Â    192 cycles per minute

Â

Remember -  excessive heaving and shoving at the wing tip can be quite damaging.

============================================

Regards

SWK

----- Original Message -----
From:
"Discussion of issues relating to Soaring in Australia." <[email protected]>

To:
"Discussion of issues relating to Soaring in Australia." <[email protected]>
Cc:

Sent:
Tue, 1 Dec 2015 15:15:48 +1100
Subject:
Re: [Aus-soaring] Wing frequency Procedure


>>a document on how the GFA would like it performed

Doesn't this vary from manufacturer to manufacturer? Some allow wing
frequency checks while on the wheel while others require the fuselage
to be in a cradle or similar. My guess is that the GFA would say
'follow the manufacturer's recommendations'.

Here's one they prepared earlier:

Wing oscillation frequency:
approx. 160/min 15 m span with winglets
approx. 130/min: 18 m span without parting
approx. 124/min: 18 m span with parting and winglets

Aircraft should rest on both wheels during frequency measurements.

I think the last part is critical for each manufacturer.

D
_______________________________________________
Aus-soaring mailing list
[email protected]
http://lists.base64.com.au/listinfo/aus-soaring

_______________________________________________
Aus-soaring mailing list
[email protected]
http://lists.base64.com.au/listinfo/aus-soaring

Borgelt Instruments - design & manufacture of quality soaring instrumentation since 1978
www.borgeltinstruments.com
tel:   07 4635 5784     overseas: int+61-7-4635 5784
mob: 042835 5784                 :  int+61-42835 5784
P O Box 4607, Toowoomba East, QLD 4350, Australia

_______________________________________________
Aus-soaring mailing list
[email protected]
http://lists.base64.com.au/listinfo/aus-soaring
_______________________________________________
Aus-soaring mailing list
[email protected]
http://lists.base64.com.au/listinfo/aus-soaring

Reply via email to