I think this would be worth moving to the GFA Forum, where you have a chance of alerting those who can make changes to the training regime and the BSE.
From: Aus-soaring [mailto:[email protected]] On Behalf Of Christopher McDonnell Sent: Tuesday, 1 December 2015 5:02 PM To: [email protected]; Discussion of issues relating to Soaring in Australia. <[email protected]> Subject: Re: [Aus-soaring] Wing frequency Procedure Thanks Stephen. Thorough as usual are you. Chris From: [email protected] <mailto:[email protected]> Sent: Tuesday, December 01, 2015 4:18 PM To: Discussion of issues relating to Soaring in Australia. <mailto:[email protected]> Subject: Re: [Aus-soaring] Wing frequency Procedure >From the old MOSP 50. Section 3 on Form 2s ============================================ 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. 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. As a guide only, some typical values:- F.R.P …… 135 cycles per minute Wood …… 180 cycles per minute Metal …… 192 cycles per minute 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] <mailto:[email protected]> > To: "Discussion of issues relating to Soaring in Australia." <[email protected] <mailto:[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] <mailto:[email protected]> http://lists.base64.com.au/listinfo/aus-soaring _____ _______________________________________________ Aus-soaring mailing list [email protected] <mailto:[email protected]> http://lists.base64.com.au/listinfo/aus-soaring
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