Interior weight differences

[Bob_Belville]

5 minutes ago, teejayevans said:

You would have to drain the fuel tanks completely, kinda of a PITA.

Yeah, to do it right (I would think that means log-able) is pretty complicated.

Chapter 3: 

https://www.faa.gov/regulations_policies/handbooks_manuals/aircraft/media/FAA-H-8083-1A.pdf

[Guest]

On September 21, 2011 at 6:37 AM, Skyatty said:

I just came through annual and decided to have my J reweighed.  The IA said, that like most people, most airplanes gain weight as they age.  We reweighed the aircraft largely because he found that five 337s had not been completed and he was concerned that W&B changes had not been updated correctly.  The aircraft was painted in the late 90s and has a relatively recent interior and much of the panel has been replaced.  The bottom line is that the aircraft was that I lost 110 lbs. of useful load based on the new weight - down from about 970 to 860.  Seemed like a huge amount to me and I may not have purchased the aircraft had I know the true empty weight.

I'm not sure how many planes the factory weighed during production, but it should be easy enough to check your paperwork to see if it includes actual scale weights.  

For those who only want to know if the numbers are favourable, have it weighed with full fuel and do the mathematics for remaining useful load.  While not correct you'll at least have some idea.

I reweighed my Comanche only to find I did not have the 1500 pound useful load I thought.  It turned out to be 1490.

Clarence

 

Edited January 25, 2016 by M20Doc

[Bob_Belville]

8 minutes ago, M20Doc said:

I reweighed my Comanche only to fine I did not have the 1500 pound useful load I thought.  It turned out to be 1490.

Clarence

 

Showing off is not nice. Unless you're Cam Newton. 

[Shadrach]

6 hours ago, DXB said:

Ross, I  agree, but unless I'm mistaken, my '68C did appear to have been weighed at the factory.  Useful load per the TCDS is 1050, but my original factory W&B sheet says 1005 after weighing- I don't see any calculation subtracting optional factory equipment from 1050 on the sheet.   I'm not a 100% sure on this- I'll have to recheck tonight, and someone with direct knowledge of the production process may be able to shed more light.

Regardless, I do feel a strong urge to know what my plane actually weighs. The calculated one for a 50 year old plane might be wildly inaccurate in either direction. I assume staying under the official max gross provides a wide margin of safety around most situations in which I would be likely to use it.  If I want to get the max utility out of the plane by loading it up, trying to simply guess exactly how wide that margin is at any particular DA seems too risky without deep aeronautical engineering and test piloting knowledge. Byron's situation where useful load increased for later years of the identical airframe and powerplant seems like a special case where there's clear quantitative indication that the margins built into his year were much wider than necessary.  

As far as the weight on the official document, that is a somewhat distinct issue. I suspect that I have more useful load than calculated, but don't want to give up official useful load on it if I'm wrong - as it may impact the value of the plane.  There is also urge to have the legal option to occasionally use a small amount of load that is not really there based on the actual weight, knowing the wide built in margins, but this is probably not the healthiest mindset.  

Is it unsavory to ask an A&P to "unofficially" weigh the plane, then write up officially only if the result is in my favor?

Having an airplane specific W&B with listed equipment does not mean it was weighed. Mooney claimed 1100lbs for the F model, but mine came with 1041lbs from the factory. I do not believe it was weighed.

Edited January 26, 2016 by Shadrach

[ArtVandelay]

I would assume that any plane that has been repainted has gained weight.

Ditto for any corrosion protection.

Probably any avionics upgrade, I doubt shops weigh the new wiring, connectors, etc, they seem to only weigh the boxes.

[Yetti]

2 hours ago, teejayevans said:

You would have to drain the fuel tanks completely, kinda of a PITA.

I believe the weight and balance from the factory takes into account the fuel in the tanks.  Assuming you knew how much is in there.   My stick is pretty accurate.

[Shadrach]

2 hours ago, teejayevans said:

I would assume that any plane that has been repainted has gained weight.

Ditto for any corrosion protection.

Probably any avionics upgrade, I doubt shops weigh the new wiring, connectors, etc, they seem to only weigh the boxes.

Avionics today are likely lighter than they've ever been, as is the wiring and the connectors. Planes would be getting lighter if it weren't for owners stuffing them with more and more equipment. A GPS/COM and NAV/COM running an Aspen should be lighter than twin KX170Bs, DME and ADF.

Edited January 26, 2016 by Shadrach

[Hank]

2 hours ago, Bob_Belville said:

Showing off is not nice. Unless you're Cam Newton. 

War Eagle!

I have NO plans to reweigh my C. Between the one piece belly and 3-blade prop, I'm happy with the listed 969 lbs.

[Hank]

Just now, Hank said:

War Eagle!

I have NO plans to reweigh my C. Between the one piece belly and 3-blade prop, I'm happy with the listed 969 lbs.

P.S.--why would a repaint increase empty weight? A good paint job starts with stripping the old paint off, right? Or are you saying that my five color paint job weighs more than what was probably a factory 2-tone paint scheme?

[Shadrach]

On 1/25/2016 at 7:34 PM, Hank said:

P.S.--why would a repaint increase empty weight? A good paint job starts with stripping the old paint off, right? Or are you saying that my five color paint job weighs more than what was probably a factory 2-tone paint scheme?

On the 60's birds, the original lacquer from the factory was put on so thin as to barely cover the primer.  A new paint job is going to weigh more. I've been rethinking the notion that a "good" paint job starts with stripping. I have an airframe that has always been hangared and never seen stripper. I'm not sure I want to change that. Stripper is caustic stuff and it will eat your plane if not completely rinsed away.

Edited January 22, 2022 by Shadrach

[kpaul]

12 minutes ago, Shadrach said:

never seen stripper

How are they to pay for their children's college education is no one goes to see them?

[Hank]

47 minutes ago, kpaul said:

How are they to pay for their children's college education is no one goes to see them?

The many make up for the few. One folded dollar at a time . . .  

[Andy95W]

6 hours ago, DXB said:

Could one get an estimate by weighing with the tanks topped off and then subtracting that weight?  This might at least give a sense of whether worth it to reweigh formally.

Absolutely. I would definitely help an owner do an "unofficial" weighing such as this with full fuel and then subtract.  If the actual weight was within 10 pounds of the mathematical, I wouldn't worry about the difference.  If the airplane was significantly heavier than the calculated weight, I would find the error in the calculations at the next annual to cover my ass.

[FlyingDude]

On 1/25/2016 at 1:20 PM, carusoam said:

Expect that Back in the day the factory weighed a sample of the planes coming off the line.  Probably didn't weigh every plane.

Didn't google it to fact-check, but my pre-buy AP, who also worked as test pilot at GA aircraft manufacturers, told me that they used to weigh 20% of the planes, and calculate the average.

 

[FlyingDude]

On 1/25/2016 at 11:00 PM, Andy95W said:

Could one get an estimate by weighing with the tanks topped off and then subtracting that weight?  

 

On 1/25/2016 at 11:00 PM, Andy95W said:

weighing such as this with full fuel and then subtract.

Donuts compress as you load the plane.  Do you level the the empty plane and fill up the tanks and accept the pitch-up or do you level it with the tanks full?

[FlyingDude]

On 1/25/2016 at 4:23 PM, Bob_Belville said:

You would have to drain the fuel tanks completely, kinda of a PITA.

Siphon as much as you can.  The remaining 6-8 gallons of useable can be drained by securing the fuel sampling ring on the fuel selector in open position by using a pencil to keep it up.  Whatever drains, was usable.  Whatever remains, was unusable...  Took me 30min setup, 1 hr siphoning, 1.5 hrs watching it drip.  Of course, I couldn't leave the hangar while fuel was dripping, but I used those 1.5 hrs creatively on facebook and mooneyspace...

The manual calls for disconnecting the booster pump from the injector assy, running the pump and letting it drain all usable fuel.  That should take really little time.  But, #1 I didn't want to f*ck with the fittings, #2 I wasn't sure I could catch fast-squirt fuel without spillages 

[David Lloyd]

My 1975 was weighed at the factory with full fuel. The weight was backed out based on the fuel weight at 80*F. They also measured wheel centers to correct for disc compaction.  Useful load was 936.  Over the years, a lot of stuff was changed, radios, mods. Some showed up on the W&B, others... ?

Two years ago, I put in another leather interior, removed a huge amount of extra foam insulation, installed some new radios and had the plane weighed. Shop disconnected the fuel line and pump all possible from the tanks, then drained the remains from the tank sumps.  They only got out another cup and a half per side.  Put in the unusable fuel, leveled and weighed.  Useful load was now 828. Just for fun I added all the stuff not installed at the factory: bladders, 3 blade prop, wing tips, all the 201 mods, articulating seats, stormscope, HSI system, Stec auto pilot, extra for the leather seats,  powerflow exhaust for a total of 108 pounds. Yep, without all the extra stuff, it would have weighed just what it did leaving Kerrville. Every now and then I do believe in coincidences.