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
âringâ when tapped, but if it is cracked it
will be âdeadâ. 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 Â
3">Â Â Â 180 cycles per minute
Metal Â
   192 cycles per minute
Â
Remember -Â 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
