Wing Frequency measuring app

[[email protected]]

I have written an app that measures wing frequency - currently available for Android on the Play Store here: https://play.google.com/store/apps/details?id=com.controlj.ios.wingfreq.

An IOS version will be available once I jump through the various hoops Apple places in the way.

Video of it in action here: https://youtu.be/dBJOBxGWtCQ.

Clyde.

[Glidingstuff[_2_]]

Awesome. Thanks

[POPS]

Could you explain what information, useful or otherwise you getting from doing this.

Thanks



I have written an app that measures wing frequency - currently available for Android on the Play Store he https://play.google.com/store/apps/details?id=com.controlj.ios.wingfreq.

An IOS version will be available once I jump through the various hoops Apple places in the way.

Video of it in action he https://youtu.be/dBJOBxGWtCQ.

Clyde.

[[email protected]]

The wing frequency is measured by rocking one wingtip up and down, so that the opposite tip moves up and down in unison. There is a natural frequency this will occur at determined mainly by the mass of the wings and their stiffness.

It's standard practice to measure the wing frequency of a glider at each annual inspection (or after events such as a hard landing) and compare it with the measurement from the previous year (which would be recorded in the logbook.) If there is a significant change, especially if it reduces, that suggests that there is some structural damage to the wing. A cracked spar for example will reduce the stiffness and therefore the resonant frequency.

On Sunday, 6 March 2016 05:43:03 UTC+10, POPS wrote:
> Could you explain what information, useful or otherwise you getting from
> doing this.
>
> Thanks
>
>
>
> clyde@.........;922414 Wrote:
> > I have written an app that measures wing frequency - currently available
> > for Android on the Play Store he http://tinyurl.com/z4vztzn.
> >
> > An IOS version will be available once I jump through the various hoops
> > Apple places in the way.
> >
> > Video of it in action he https://youtu.be/dBJOBxGWtCQ.
> >
> > Clyde.
>
>
>
>
> --
> POPS

[Charlie M. (UH & 002 owner/pilot)]

On Saturday, March 5, 2016 at 2:43:03 PM UTC-5, POPS wrote:
> Could you explain what information, useful or otherwise you getting from
> doing this.
>
> Thanks
>
>
>
> clyde;922414 Wrote:
> > I have written an app that measures wing frequency - currently available
> > for Android on the Play Store he http://tinyurl.com/z4vztzn.
> >
> > An IOS version will be available once I jump through the various hoops
> > Apple places in the way.
> >
> > Video of it in action he https://youtu.be/dBJOBxGWtCQ.
> >
> > Clyde.
>
>
>
>
> --
> POPS

Thanks for asking, I wasn't sure myself...... Now we all know!
;-)

[IA DPE]

In order for this to be recorded in the aircraft logbook, it would have to be a FAA approved measuring device, right?

While I can see some value in knowing this reading, there would have to be standardization in the measuring device and technique I would think.

[Steve Leonard[_2_]]

On Saturday, March 5, 2016 at 8:01:24 PM UTC-6, IA DPE wrote:
> In order for this to be recorded in the aircraft logbook, it would have to be a FAA approved measuring device, right?
>
> While I can see some value in knowing this reading, there would have to be standardization in the measuring device and technique I would think.

The FAA does not approve of the ruler or protractor you use to measure control travels. They don't approve the spring scale you use to check the force required to lock or unlock the dive brakes. They don't approve the gauge you use to check your tire pressure. Why do you think they would have to approve a device that can be used to measure 1st mode symmetric wing bending? Not everything that gets written in the log book needs to have been measured with some FAA Approved Device.

And, yes. There is a standard procedure for doing this. And it is measured by many manufacturers, and is recorded in the data for the airplane. If you have any German manufactured glider, and have data back to the factory weight and balance and initial flight test, this number is probably recorded there.

Steve Leonard

[JS]

Thanks, Clyde. I know that this measurement is done at every Form Two inspection where you live.

Until this app, the device was a mark one eyeball, and counting "one, two, three, (etc) while looking at some cheap watch. Then doing it again because you're sure you lost count! The last bit probably won't change until you believe the app can count.
Jim


On Saturday, March 5, 2016 at 6:01:24 PM UTC-8, IA DPE wrote:
> In order for this to be recorded in the aircraft logbook, it would have to be a FAA approved measuring device, right?
>
> While I can see some value in knowing this reading, there would have to be standardization in the measuring device and technique I would think.

[[email protected]]

And remember to do this while the fuselage is in a cradle resting firmly on the ground. The tire and suspension will affect the frequency.

-Tom

On Saturday, March 5, 2016 at 6:42:49 PM UTC-8, JS wrote:
> Thanks, Clyde. I know that this measurement is done at every Form Two inspection where you live.
>
> Until this app, the device was a mark one eyeball, and counting "one, two, three, (etc) while looking at some cheap watch. Then doing it again because you're sure you lost count! The last bit probably won't change until you believe the app can count.
> Jim
>
>
> On Saturday, March 5, 2016 at 6:01:24 PM UTC-8, IA DPE wrote:
> > In order for this to be recorded in the aircraft logbook, it would have to be a FAA approved measuring device, right?
> >
> > While I can see some value in knowing this reading, there would have to be standardization in the measuring device and technique I would think.

[[email protected]]

Yes, in the weight and balance of my ASH30mi it's write;

- Flügel-Biegeschw.-Zahl: 72 pro Minute

- Stehwellenmessung: 118MHz; 1,7, 126MHz; 1,1, 135MHz; 1,2

François

[Eric Munk]

>And remember to do this while the fuselage is in a cradle resting firmly
on
>the ground. The tire and suspension will affect the frequency.
>
>-Tom

I would check the manual for the method used. Some manufacturers
specifically state the aircraft to be on wheel and tail skid, with tyre
pressures checked to be in a certain range. Using cradles will result in
deviations from previous methods used.

[Soarin Again[_2_]]

At 02:42 06 March 2016, JS wrote:
>Thanks, Clyde. I know that this measurement is done at every Form Two
>inspection where you live.
>
>Until this app, the device was a mark one eyeball, and counting "one,
two,
>three, (etc) while looking at some cheap watch. Then doing it again
because
>you're sure you lost count! The last bit probably won't change until you
>believe the app can count.
>Jim
>
>
>On Saturday, March 5, 2016 at 6:01:24 PM UTC-8, IA DPE wrote:
>> In order for this to be recorded in the aircraft logbook, it would have
>to be a FAA approved measuring device, right?
>>
>> While I can see some value in knowing this reading, there would have to
>be standardization in the measuring device and technique I would think.
>
20 years ago we could take a video (including a stop watch) at the wing tip

then play it back, in slow motion if preferred. Worked perfectly and it
didn't even require a computer.

[[email protected]]

Soarin, thats a brilliant idea and so dang easy to set up and measure. All it takes is a gopro mounted to the tip with a digital clock in the background. Simply brilliant.
Dan

[[email protected]]

Eric the issue would not be in specifics but in consistence, The actual freq number isnt that important unless it is radically diff than that given for the glider as delivered. To me, its the fact that a guy should decide a method of measurment and make a measure, then repeat that exact method to see if there is change over time or after a landing or high G event.
Dan

[Mark628CA]

Clyde-

Handy little App. Thanks. One suggestion: Put a 10 or 15 second delay from the time the "Start" button is pressed before counting cycles. This will allow the frequency to stabilize before starting the count.

Also, a summary page would be cool. Test time, number of beats.

Definitely worth the $0.99.

[son_of_flubber]

Has anyone set up their glider, then measured L and R wingtips, say 10 repetitions from dead stop and looked at the results for consistency?

Can it ever be 'normal' for the L and R wingtips to yield different measurements? How much deviation in successive measurements is acceptable?

Does temperature of the glider affect the measurement?

[Eric Munk]

At 14:17 06 March 2016, wrote:
>Eric the issue would not be in specifics but in consistence, The actual
>fre=
>q number isnt that important unless it is radically diff than that given
>fo=
>r the glider as delivered. To me, its the fact that a guy should decide a
>m=
>ethod of measurment and make a measure, then repeat that exact method to
>se=
>e if there is change over time or after a landing or high G event.
>Dan
>

I think we agree on this one. That is why it is important to check which
method the manufacturer used when doing his initial measurement. Saves you
a lot of hassle...

[[email protected]]

On Saturday, 5 March 2016 08:39:05 UTC+11, wrote:
> I have written an app that measures wing frequency - currently available for Android on the Play Store here: https://play.google.com/store/apps/details?id=com.controlj.ios.wingfreq.
>
> An IOS version will be available once I jump through the various hoops Apple places in the way.
>
> Video of it in action here: https://youtu.be/dBJOBxGWtCQ.
>
> Clyde.

There is absolutely no difference in measured wing frequency whether done on a cradle or main / tail wheel skid or wheel. Try it out before you write otherwise. - Rolf
Rolf

[jfitch]

On Sunday, March 6, 2016 at 2:03:36 PM UTC-8, wrote:
> On Saturday, 5 March 2016 08:39:05 UTC+11, wrote:
> > I have written an app that measures wing frequency - currently available for Android on the Play Store here: https://play.google.com/store/apps/details?id=com.controlj.ios.wingfreq.
> >
> > An IOS version will be available once I jump through the various hoops Apple places in the way.
> >
> > Video of it in action here: https://youtu.be/dBJOBxGWtCQ.
> >
> > Clyde.
>
> There is absolutely no difference in measured wing frequency whether done on a cradle or main / tail wheel skid or wheel. Try it out before you write otherwise. - Rolf
> Rolf

So can I assume before you posted that you checked every glider in existence, on every cradle imaginable, and at every tire pressure?

On my Schleicher at least, the builder has called out some very specific jacking points for this procedure.

[[email protected]]

On Monday, 7 March 2016 02:55:35 UTC+11, Mark628CA wrote:
> Clyde-
>
> Handy little App. Thanks. One suggestion: Put a 10 or 15 second delay from the time the "Start" button is pressed before counting cycles. This will allow the frequency to stabilize before starting the count.
>
> Also, a summary page would be cool. Test time, number of beats.
>
> Definitely worth the $0.99.

Thanks for the suggestions; I don't think the delay is necessary since it only averages over the last 20 beats. I am going to change that to a time, rather than a number of beats, since that means a wing at 100 bpm takes twice as long as one at 200 to measure. So I think I'll change it to counting the last 10 seconds or so. It calculates the standard deviation of the beat interval and announces success when that is below .02 for the sample time.

I have some other optimisation ideas to improve the performance on gliders with very flexible wings, which sometimes have a second order vibration going on at the same time.

Clyde

[[email protected]]

On Monday, 7 March 2016 09:03:36 UTC+11, wrote:

>
> There is absolutely no difference in measured wing frequency whether done on a cradle or main / tail wheel skid or wheel. Try it out before you write otherwise. - Rolf
> Rolf

I have tried it out - and have seen differences. One in particular was 135 on the wheel and 141 on the cradle. That's not a huge difference, but enough to warrant a closer look, so consistency in technique will help avoid false alarms.

Clyde

[Steve Thompson[_2_]]

02:27 07 March 2016, wrote:
>On Monday, 7 March 2016 09:03:36 UTC+11, wrote:
>
>>
>> There is absolutely no difference in measured wing frequency whether
done
>on a cradle or main / tail wheel skid or wheel. Try it out before you
write
>otherwise. - Rolf
>> Rolf
>
>I have tried it out - and have seen differences. One in particular was
135
>on the wheel and 141 on the cradle. That's not a huge difference, but
>enough to warrant a closer look, so consistency in technique will help
>avoid false alarms.
>
>Clyde
>
>
Suggest instead of opinion - just use the MM for the glider. e.g. ASG29 MM
para
3.2 gives the support points. MFG data sheet at build gives original
frequency,
MM7.1 requires annual check, MM7.2 requires it after hard landing, gives
tolerance.

Good clear info from Schleicher, which all ties together nicely imho.

And a very nice app from Clyde, thanks. Like a lot of great ideas it seems
obvious
now but you thought of it.

[Eric Munk]

At 07:23 07 March 2016, Steve Thompson wrote:

>Suggest instead of opinion - just use the MM for the glider.

A very good suggestion. Did a Twin Astir wing frequency check the other
week, and that was off by 5 compared to the last measurements. Turns out it
somewhat unusually should sit on its wheel and skid (12th item of the
annual checklist in the mainenance manual) not on threstles, with a
specified tyre pressure of 2.5-2.8 bar. Remeasured and it now was bang on.
The way you measure DOES matter.

[firsys]

On Friday, March 4, 2016 at 4:39:05 PM UTC-5, wrote:
> I have written an app that measures wing frequency - currently available for Android on the Play Store here: https://play.google.com/store/apps/details?id=com.controlj.ios.wingfreq.
>
> An IOS version will be available once I jump through the various hoops Apple places in the way.
>
> Video of it in action here: https://youtu.be/dBJOBxGWtCQ.
>
> Clyde.

The easy and revealing part of the test, is to observe the wing tip
phase; in the first bending mode they should be synchronised within inches of each other. A wing lagging in phase would indicated spar or skin damage.
This is probably more accurate than the frequency test.
JMF

[[email protected]]

This is a useful thread. Checking the wing resonant frequency annually, and after a bad landing, does sound a good idea, although I'm not aware that it is required at annual inspections in the USA, unless the manufacturer has specified it. My glider documentation has the factory measurement (110 per minute) resting on main wheel and tailwheel. On my check out, I was instructed to set the wings vibrating at every daily inspection, but only told to look for crinkles appearing in the wing surface, or unusual squeaking noises. I hadn't heard that the tip phase was good to look at. I'd probably buy an app for $1 if it was for the iPhone, but also I think it would be pretty easy to do accurately with a normal digital watch.