Weight & Balance

[skippydiesel]

Just heard a rumour - RAA L2's are no longer able to perform an authorised weight & balance.

 

Got to fined/use a CASA approved person (do hens have teeth?).

 

Please tell me this is not true.

[facthunter]

Back a while you were required to renew the qualification each 12 months. Even people who were regularly doing them.  Nev

[RFguy]

The absurd thing is- it is extremely simple.   I mean it is addition and multiplication.....

And then there is this BS  that you have to do it with the hangar doors closed., cant do outside in case of wind. 

Well I know lots of hangars that have windy drafts through them with the doors closed-- and they would certainly cause unstable weighing !

 

The spec should be "that the readings be stable with x % or x kg etc ....." not some d*** telling me I have to have the doors shut without further qualification. what a load of crap.

Oh and then there was the crap I got told about the aircraft being completely level and the bubble in the exact middle .. exact... 

Well the bubble was about 1mm out of the middle and that  was about a 1 degree out. ...Well there is such a thing as trignometry...

And the error that that would have incurred was  MANY TIMES LESS than the scales uncertainty and MANY  TIMES LESS THAN  the resolution of the system  because the nosewheel weight was only ~ 40kg and the scales only read in 0.5kg increments...FFS

WHat a load of BS.  but, the other person didnt seem to understand this fundamental measurement limitation.

Dont get me started now.....

The rules and guide to weighing should be written with math based pactical limiations in mind, and written around required number uncertainties, not some *** *** on the end of the phone telling me '  hangar doors must be shut no exceptions'

 

 

Edited October 17, 2022 by RFguy

[spacesailor]

Like Iv,e said so many times ! .

Bureaucracy 

Give a ' clerk ' a stick & your getting another dictator. 

spacesailor

 

[facthunter]

CASA's run by Lawyers and people who know little about aviation.. Bureaucracy is too simple to cover it..   being dumb and pedantic doesn't contribute to SAFETY and that's the "S". Nev

[turboplanner]

1 hour ago, RFguy said:

The absurd thing is- it is extremely simple.   I mean it is addition and multiplication.....

And then there is this BS  that you have to do it with the hangar doors closed., cant do outside in case of wind. 

Well I know lots of hangars that have windy drafts through them with the doors closed-- and they would certainly cause unstable weighing !

 

The spec should be "that the readings be stable with x % or x kg etc ....." not some d*** telling me I have to have the doors shut without further qualification. what a load of crap.

Oh and then there was the crap I got told about the aircraft being completely level and the bubble in the exact middle .. exact... 

Well the bubble was about 1mm out of the middle and that  was about a 1 degree out. ...Well there is such a thing as trignometry...

And the error that that would have incurred was  MANY TIMES LESS than the scales uncertainty and MANY  TIMES LESS THAN  the resolution of the system  because the nosewheel weight was only ~ 40kg and the scales only read in 0.5kg increments...FFS

WHat a load of BS.  but, the other person didnt seem to understand this fundamental measurement limitation.

Dont get me started now.....

The rules and guide to weighing should be written with math based pactical limiations in mind, and written around required number uncertainties, not some *** *** on the end of the phone telling me '  hangar doors must be shut no exceptions'

 

 

If you're weighing the aircraft wind can be taken out of the equation by weighing it pointed at the doors, then a second weight pointed away from the doors and if there's any variation, start taping up the cracks and gaps. (Because in one direction the wind is blowing on the leading edges, and the other direction, blowing on the trailing edges you can't just average the readings, but withour aerofoils you (a) would not expect any difference and (b) if there was and you hadn't changed anything on the airframe you could.

Also sometimes one set of scales will be off, so all three should be zeroed in.

As you say the equations are very simple, but understanding them is not.

[RFguy]

yeah it's pretty easy to see the readout walking around of course  on digital scales. the numbers roll....

 

On analog readout scales, I think the airflow induced variation would be less obvious.

 

if there is airflow, come back at 6am when it is calm....

[skippydiesel]

Gentlefolk - IS THE RUMOUR TRUE??

Or

Are we just getting or underwear uncomfortably contorted, for no good reason

[Blueadventures]

11 minutes ago, skippydiesel said:

Gentlefolk - IS THE RUMOUR TRUE??

Or

Are we just getting or underwear uncomfortably contorted, for no good reason

Your best to phone RAAus Tech in the morning;  keen to hear what they tell you.

[skippydiesel]

10 minutes ago, Blueadventures said:

Your best to phone RAAus Tech in the morning;  keen to hear what they tell you.

Will do.

[kgwilson]

I used a set of aircraft scales I borrowed. I did a follow up later using 3 digital bathroom scales & the difference was f*#ck all. Surely the rumour can't be true. Determine the datum, specify the level reference, determine the CoG & fore and aft limits & do the measurements & calculations. Before you do anything at all download & read the FAA Weight & Balance handbook. It has every minute detail you ever need to know in its 97 pages. Once you have figured it out the process is easy. Mind you I have met some pretty dumb L2s so there may be something in the rumour..

[facthunter]

They DID have big trouble a while back from  SOME very dodgy details provided that  caused considerable embarrassment. In all this I wonder WHO  assesses the assessors? . FFS they have the best (for them) penalty regime imaginable ( Strict liability).  The fact the FAA handbook has 97 pages indicates there IS a bit in it.. W&B was always a 100% pass required subject any time I sat it. IF you muck it up your plane is NOT AIRWORTHY and may be uncontrollable.  Nev

[Blueadventures]

I see on RAAus Webb w&b training suspended.  I have w&b and not been advised of training suspended. Also had it under GFA for the 10 yearly glider surveys. Be keen to hear what Skippy finds out.  

[Yenn]

I have done the course to allow me to do W & B and it is not difficult but I don't think I can do it now legally because I have not renewed.

Why renewal is necessary I don't know. Those who think wind doesn't affect the weighing are in for a shock when they do the job. I tried to weigh my RV4 with only one leaf of the doors open and the numbers just would not stabilize. I shut that door and perfect stability. The wind was very slight, but you can work it out for yourself using the usual theory for lift.

Those who think it doesn't matter about levelling the plane just don't understand what they are trying to do.

I consider CASA aree over the top requiring you to renew every year. Those who disregard the levelling will not get it right even if they do the theory every year or even monthly.

[turboplanner]

44 minutes ago, Yenn said:

Those who disregard the levelling will not get it right even if they do the theory every year or even monthly.

Important point because the higher the structure and equipment level the more inaccurate the datums are, throwing mass toward the low end.

[facthunter]

The actual pitch is important as the CofG is above the position of the wheels contact point  If you pick the tail of a Tiger moth up and lift it high enough and let it go the plane will tip on it's nose .  Nev

[skippydiesel]

From RAA today - If I understood correctly;

 

RAA L2's have not had automatic W&B testing privileges since 2016.

RAA has a submission in with CASA, right now, to restart W&B testing (if you have done the course)

The submission is a step by step methodology for anyone whishing to do a W&B the CASA/RAA approved way - I don't quite understand if this allows an owner to actually do a pre first flight W&B (doubt it)

Proper scales are required (not your bathroom jobs).

 

I suspect that W&B for a first flight will still have to be signed of by an authorised (?) person

[Blueadventures]

6 minutes ago, skippydiesel said:

From RAA today - If I understood correctly;

 

RAA L2's have not had automatic W&B testing privileges since 2016.

RAA has a submission in with CASA, right now, to restart W&B testing (if you have done the course)

The submission is a step by step methodology for anyone whishing to do a W&B the CASA/RAA approved way - I don't quite understand if this allows an owner to actually do a pre first flight W&B (doubt it)

Proper scales are required (not your bathroom jobs).

 

I suspect that W&B for a first flight will still have to be signed of by an authorised (?) person

A way forward in near future would be to track down a SAAA w&b person near you; should be someone close by.

Edited October 18, 2022 by Blueadventures

[skippydiesel]

8 minutes ago, Blueadventures said:

A way forward in near future would be to track down a SAAA w&b person near you; should be someone close by.

Done! 30 seconds ago. My thanks.

[kgwilson]

When I did the W&B on my build I had to get it signed off not with a L2 but a L4 (a highly skilled and qualified (old retired) LAME who also signed off my final inspection. That was in 2015. I did have proper electronic aircraft load cells but at the time I could have used bathroom scales. As mentioned earlier I did another W&B a bit later on with bathroom scales I got from a bloke who had the hangar next door & the result was very close to the original.

[RFguy]

Bathroom scales are fine, and often have more resolution (0.1kg instead of the 0.5kg resolution weighing setups I have come across) however I feel the calibration must be verified before use- at least two points (like near expected weights, and 50% of that)  to determine absolute calibration and linearity .

The levelling is doesnt have to be controversial. On the most recent system I looked at, the RAAUS scales, which I might add- the system is VERY NICE , nice it, have 0.5kg resolution, and given they'll likely round to nearest, is an uncertainty of 1kg.. So for 30kg on the nosewheel, that is a 3% uncertainty error.....  This has to be understood.  I determined that the error due to the remaining inclination (imperfect levelling) amounted to a bias of 0.3kg.... Bubble gauges do have mm versus degrees, you can look it up. Then it's a simple sine table lookup to calculate whether the error due to levelling is less than the intrinsic uncertainty of the weighing system.

[onetrack]

To ensure verifiable accuracy in weighing, you really need "trade-certified", or "trade-approved" scales - which simply means bathroom scales don't cut it. Certified or approved scales are readily available from professional scales retailers.

 

https://www.instrumentchoice.com.au/news/what-are-trade-approved-scales

[skippydiesel]

Any measuring devise that has repeatability, within an accepted range, must by definition be appropriate. (repeatability in this context simply means that the devise will give the same result every time it is used). 

This is not the issue - we live in an era where society (& authority) seem to require third part endorsement (certification) of almost everything we experience, including the use of scales to weigh  whatever.

[turboplanner]

35 minutes ago, skippydiesel said:

Any measuring devise that has repeatability, within an accepted range, must by definition be appropriate. (repeatability in this context simply means that the devise will give the same result every time it is used). 

This is not the issue - we live in an era where society (& authority) seem to require third part endorsement (certification) of almost everything we experience, including the use of scales to weigh  whatever.

That's because 30% of the population think that their measuring device is just as good.

[Yenn]

What use is repeatability if the repeat is incorrect each time.

For scales to be usable they need to be correct. If they are incorrect by for example 15% they should I think still give a correct C of G, but the weight will be incorrect.

If they are incorrect by different percentages at the ends of the scale, they will be incorrect on C of G as well as weight. In both cases not acceptable for safe flying.