Weight and Balance revision

[Joe Larussa]

Do you guys update your weight and balance when there is a change of maybe two pounds? I'm pulling my

power supplies after installing LED's.

[Igor_U]

yes.

similar weight delta happened to me with battery change and was reflected in W&B.

[DonMuncy]

My understanding is that legally, the A&P making any change to the equipment on the plane is required to update the W&B. My experience is that if it is less than a pound, they will often enter the change as negligible, with no recalculation. 

[kortopates]

^+1 Its a requirement, unless negligible. Besides, you want to get every pound you are entitled to of useful load.

[carusoam]

Joe,

Realistically, the POH gets updated with the change... the math isn’t that hard... but it is Engineering 101 level... 

Modern POHs use decimal points in the weight section...

+1 for getting the update... the trim will always work in the range... as designed...

There is plenty of unknowns already in the system... lots of dirt acquired over the years, and left over wire...

PP thoughts only, not a mechanic...

Best regards,

-a-

[EricJ]

 

8 minutes ago, DonMuncy said:

My understanding is that legally, the A&P making any change to the equipment on the plane is required to update the W&B. My experience is that if it is less than a pound, they will often enter the change as negligible, with no recalculation. 

Yup.   FWIW, this is in AC 43.13-1, Par 10-2.c.    Aircraft less than 5000 lb empty weight have a negligible change for anything that is one pound or less.

[cliffy]

Going from a Gill 35 battery to a Concord sealed is a 2+ pound weight difference. Ask me how I know:-)  W&B recalc required. 

[RLCarter]

On 9/11/2019 at 4:36 PM, EricJ said:

Yup.   FWIW, this is in AC 43.13-1, Par 10-2.c.    Aircraft less than 5000 lb empty weight have a negligible change for anything that is one pound or less.

how many "negligible" entries can you have?...lol. I did a full weight and balance when I got the plane (didnt trust the one in it), now I know its correct and the few things removed/added have been added to the weight & balance..we need all the useful load we can get (i'm over gross with 3 male adults and full fuel)

[GeeBee]

I have taken to doing a reweigh about every 5 years on my airplanes. I have found it worthwhile, all those "negligible" have a way of adding up.

 

 

 

[jetdriven]

They never add up in your favor. Its legal to continue to do math.

[Niko182]

I will ask for a new W&B anytime I can gain a couple pounds of useful load. Every additional pound I gain just means more fuel. More fuel is more margin of safety. My plane isn't getting near a scale anytime soon, It least for the time I own it.

[Shadrach]

On 9/11/2019 at 5:31 PM, carusoam said:

Joe,

Realistically, the POH gets updated with the change... the math isn’t that hard... but it is Engineering 101 level... 

Modern POHs use decimal points in the weight section...

+1 for getting the update... the trim will always work in the range... as designed...

There is plenty of unknowns already in the system... lots of dirt acquired over the years, and left over wire...

PP thoughts only, not a mechanic...

Best regards,

-a-

I have never seen an updated POH but then mine only has raw numbers for MGW AND 2300lbs at several key altitude/temp combinations, no graph to amend. I have seen and have a weight and balance folder with all revisions starting with the factory numbers for my plane when delivered. We’ve lost nearly 20lbs of empty weight since 1967.

i think the FAA defines weight changes under 2lbs as negligible. 15 of those done over a 50 year period might stack up a bit but would still  still be less than 2% of the aircraft’s MGW. Probably not noticeable in the cockpit.

Edited September 15, 2019 by Shadrach

[carusoam]

Ross,

The POH for the M20R contains the history of equipment added... or removed...

Both WnB updates in chart form and key pages of user manual updates for equipment...

 

Lots of details for things like speed brakes and their ops...

Near useless data for complex items like a GPS...

Best regards,

-a-

[Shadrach]

28 minutes ago, carusoam said:

Ross,

The POH for the M20R contains the history of equipment added... or removed...

Both WnB updates in chart form and key pages of user manual updates for equipment...

 

Lots of details for things like speed brakes and their ops...

Near useless data for complex items like a GPS...

Best regards,

-a-

Thanks. I have something like 14 revisions in my W&B binder. There is no where to add them to our manual. I think the difference is that GAMA standerdised what should be in the AFM sometime in the 70s. Prior to that a simple make/model POH was what came with the plane. Newer birds like yours probably information specific to your S/N.

[ArtVandelay]

I put all my line items in a spreadsheet, found about 10% error rate: omissions, math errors, numbers transposed, etc. In the end, it amounted to a 2 lb difference.


Tom

[HIghpockets]

I just had two G5s and a GFC 500 installed. The vacuum system, the BK HSI, AI, a WX1000 and some cable for a Garmin 396 were removed. I flew the airplane until we had about 8m gallons left, drained the tanks, added unusable. fuel and did a new W&B. Gained about 40 lbs in useful load.

[RLCarter]

12 hours ago, Niko182 said:

My plane isn't getting near a scale anytime soon, It least for the time I own it.

Why wouldn't you want to weigh your aircraft? Just curious 

[ArtVandelay]

Why wouldn't you want to weigh your aircraft? Just curious 

Because they’re not accurate, or at least the APs methods are suspect.
1. MSC didn’t drain the tanks, just used my inaccurate fuel gauges to determine fuel weight.
2. AP wanted to weigh my plane, he was going to fill my fuel tanks and subtract spec capacity. I said no way. Found out later doing JPI fuel calibration my tanks hold ~67 gallons. So I would have been 18 lbs heavier.

And then there is the scale which may or may not be accurate.


Tom

[Hank]

44 minutes ago, ArtVandelay said:

Because they’re not accurate, or at least the APs methods are suspect.
1. MSC didn’t drain the tanks, just used my inaccurate fuel gauges to determine fuel weight.
2. AP wanted to weigh my plane, he was going to fill my fuel tanks and subtract spec capacity. I said no way. Found out later doing JPI fuel calibration my tanks hold ~67 gallons. So I would have been 18 lbs heavier.

And then there is the scale which may or may not be accurate.


Tom

And whatever dirt, grease and grime has accumulated in wheel wells, tail cone and other inaccessible areas. Need to wash the plane, then let all water evaporate. And remove absolutely everything from inside, vacuum the carpets, etc.

[ArtVandelay]

And whatever dirt, grease and grime has accumulated in wheel wells, tail cone and other inaccessible areas. Need to wash the plane, then let all water evaporate. And remove absolutely everything from inside, vacuum the carpets, etc.

Replace the air in the tires with helium, remove CO2 detector from panel, remove the lightbulbs in the glare shield and overhead light, empty your oxygen tank if you one.... ;-)


Tom

[Jerry 5TJ]

10 hours ago, ArtVandelay said:

I put all my line items in a spreadsheet, found about 10% error rate: omissions, math errors, numbers transposed, etc. In the end, it amounted to a 2 lb difference.


Tom

Ditto. 

Around 1990 I went through the W&B entries for my E all the way back to its 1964 Kerrville origin & found numerous errors from pre-spreadsheet days.  

The plane also had “numerous” equipment changes not in the W&B history.   

I know folks who advise never weigh your plane.  But I ask: Why trust 40+ years of vague entries and errors when you can get a clean start with a good weight & balance?  

If you don’t want to know about the real figures why bother to do a W&B calculation for a flight at all?  

Me, I’d rather know the true W&B and perhaps deliberately overload the plane rather than use suspect data.  

[GeeBee]

We once had a Piper Aztec on a Part 135 certificate. Because Part 135 and 121 require a reweigh every 3 years. We found the airplane 50 pounds heavier and the CG was way off of the AFM numbers. Upon investigation we found a tool box full of tools way back in the tail area. Along the same lines we found production tools in Beech Duchess that made it heavier than the AFM said since they perform a calculated W&B, not an actual weighing at the factory. As to scale inaccuracy, there are easy an cheap ways to calibrate a scale. A few barbell weights which you can use as tail weights for jacking anyway can calibrate a scale quickly. Bottom line, weighing works and it picks up bad things.

 

 

[ArtVandelay]

Ditto. 
Around 1990 I went through the W&B entries for my E all the way back to its 1964 Kerrville origin & found numerous errors from pre-spreadsheet days.  
The plane also had “numerous” equipment changes not in the W&B history.   
I know folks who advise never weigh your plane.  But I ask: Why trust 40+ years of vague entries and errors when you can get a clean start with a good weight & balance?  
If you don’t want to know about the real figures why bother to do a W&B calculation for a flight at all?  
Me, I’d rather know the true W&B and perhaps deliberately overload the plane rather than use suspect data.  

I know what there are now, they’re no longer vague or erroneous.
It costs money, I figure draining tanks, weighing...is a 2 hour job.
How do you know the scales are accurate? You’re trading years of suspect data for a single source of suspect data. You have more faith in a scale that even if off by 1% can cost you 20lbs of useful load.


Tom

[cliffy]

Let's take another look-

First the scales are required be certified for accuracy In FACT, ALL your A&Ps tools are supposed to be certified every year for accuracy  (torque wrenches and compression gauges especially). 

There is a procedure  to follow when weighing an airplane. It's all contained in Pt 43.13 and/or the FAA Weight & Balance Handbook

https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/media/faa-h-8083-1.pdf

While many just top the tanks and subtract the fuel weight down to the unusable (allowed BTW)  the real way is to weight it with only unusable fuel in the tanks.

BTW, did you know that CAR3 airplanes have a different "Empty Weight" than Part 23? It deals with engine oil. One has no oil included in the empty weight and the other has it included in the empty weight. How much does oil weigh again?  See page 3-4 in the above manual for both answers. (ALL fluids change weight with temperature so if you do this in a cold winter in an unheated hangar make the adjustments)

SO if you are afraid to weight your airplane you are accepting of being over weight on TO if your airplane has gained weight over the years? Just askin'

When I weighed my airplane the first time after the factory weight I gained 90 pounds of useful load as they had made a mistake on the original W&B sheet from the factory and all the computed changes over the years were wrong as a result. 

 

[ArtVandelay]

I’m surprised if they bothered to weigh each early J, they came out pretty standardized, I expect they weighed the first, and just rubber stamped the next 1000. I can be 159lbs overweight and still be legal if my J was manufactured in a different year. Of all the things to worry about, being little overweight in my early J is at the bottom of the list.


Tom