Empty Weight

birdus said:
As part of trying to solve this mystery, I've been reading the FAA Weight and Balance Handbook, and just got to this part in the section: Preparing for Weighing

"Drain fuel from the tanks in the manner specified by the aircraft manufacturer. If there are no specific instructions, drain the fuel until the fuel quantity gauges read empty when the aircraft is in level-flight attitude. Any fuel remaining in the system is considered residual or unusable fuel and is part of the aircraft empty weight."

So you guys are right on the money. Now I just need to figure out how the plane could weigh 860 pounds empty when new, and weighs 950 pounds now with full fuel. It just doesn't make any sense (2 x 12.5 gallon tanks). The only way it could add up is if the empty weight when new was calculated with full fuel and 90 pounds of other crap have been added to the plane over the years. The plane is very simple and I've been poking around getting to know my new plane and I would bet a hundred bucks right now there's no way 90 pounds of equipment have been added to it. So, I'll keep trying to figure it out.

Thanks.
Click to expand...

I’m having trouble getting my head wrapped around ”...drain the fuel until the fuel quantity gauges read empty when the aircraft is in level-flight attitude. Any fuel remaining in the system is considered residual or unusable fuel and is part of the aircraft empty weight." I would drain the tanks until ‘usable’ fuel is gone regardless of what the ‘gauges’ say.
 
Salty said:
But they can't change the W&B without an A&P
Click to expand...
They can’t log the change in the airframe log or official W&B record. They certainly can, and should, use the most recent and accurate information when flight planning. Doesn’t matter whether it’s “official” or not.
 
luvflyin said:
I’m having trouble getting my head wrapped around ”...drain the fuel until the fuel quantity gauges read empty when the aircraft is in level-flight attitude. Any fuel remaining in the system is considered residual or unusable fuel and is part of the aircraft empty weight." I would drain the tanks until ‘usable’ fuel is gone regardless of what the ‘gauges’ say.
Click to expand...
because some aircraft specify a certain amount to be in the tank
 
MooneyDriver78 said:
aren’t you supposed to not drain the unusable fuel?
Click to expand...
Depends on the manufacture and how it's stated in the TCDS. If no requirements from OEM/TCDS then you follow whatever FAA guidance you prefer which will dictate what is drained or serviced.
 
If I recall, aircraft cerified before 1978 were weighed without engine oil...so you would have to add the oil to the empty weight when you compute your weight and balance.

Check in TCDS.
 
Doug Reid said:
If I recall, aircraft cerified before 1978 were weighed without engine oil...so you would have to add the oil to the empty weight when you compute your weight and balance.

Check in TCDS.
Click to expand...
The maintenance manual is the place to see that.

and of course any STC s
 
DaleB said:
use the most recent and accurate information when flight planning. Doesn’t matter whether it’s “official” or not.
Click to expand...
Not quite. The current empty weight and balance and equipment list is part of the aircraft type design/type certificate as stated in the TCDS and is the basis for all subsequent flight calculations. There are a number of guidance docs on this.
 
I’m going to do a reweigh as I’ve put her on a weight loss program but no way can misc. extra wiring, pulled nasty old carpet, the gravel I shop vacked out of the belly, etc.be calculated accurately. my calculations are I’ve removed or had removed about 50lbs but the scales will tell the whole story
 
Last edited:
DaleB said: ↑
They can’t log the change in the airframe log or official W&B record.
Tom-D said:
Show me ?
Click to expand...

Is it on the list of preventive maintenance items an owner/operator is allowed to do?
 
luvflyin said:
I’m having trouble getting my head wrapped around ”...drain the fuel until the fuel quantity gauges read empty when the aircraft is in level-flight attitude. Any fuel remaining in the system is considered residual or unusable fuel and is part of the aircraft empty weight." I would drain the tanks until ‘usable’ fuel is gone regardless of what the ‘gauges’ say.
Click to expand...

That would work if your fuel gauges were accurate. As we know, most are not.

My understanding is that unusable fuel is determined by the factory as follows: Test pilot flys on one tank, yanking and banking into multiple unusual attitudes. When the engine stumbles for lack of fuel, the test pilot levels off, switches to the other tank(s) and lands. Tank being tested is then filled full, and that amount is subtracted from the tank's capacity. That amount is unusable fuel. -Skip
 
Witmo said:
DaleB said: ↑
They can’t log the change in the airframe log or official W&B record.


Is it on the list of preventive maintenance items an owner/operator is allowed to do?
Click to expand...
that 32 items are not the only things.

They are the owners property.

show in 43 or 91 that the entry must have a certificate to make an entry.

I will conceded that a weight and balance that is a part of flight manual is mandatory.
 
Bell206 said:
Not quite. The current empty weight and balance and equipment list is part of the aircraft type design/type certificate as stated in the TCDS and is the basis for all subsequent flight calculations. There are a number of guidance docs on this.
Click to expand...
You must have misunderstood what I wrote. Let me try to be a little more clear in my intent by asking a question. The old (possibly original) W&B sheet that came with the airplane says one thing. You weight the airplane yourself, following al the correct procedures, and come up with a completely different result.

Which numbers will YOU use when flight planning? I"m using the ones I know to be correct. But hey, that's just me. It'll probably fly OK either way, right?
 
Tom-D said:
Show me ?
Click to expand...
I assumed. I could very well be wrong. Since I don't own an airplane for which I don't hold the repairman certificate, I really don't care about what's allowed or not allowed for airplanes with a TC.
 
DaleB said:
You must have misunderstood what I wrote.
Click to expand...
No misunderstanding. It's really quite simple. If YOU know your current certified (signed) empty weight and balance record is not correct the aircraft is not airworthy as it doesn't meet it's TCDS conditions. In other words its not legal to fly. So are you stating YOU would fly a known unairworthy aircraft?
 
Skip Miller said:
That would work if your fuel gauges were accurate. As we know, most are not.
Click to expand...
How do you know that? Most of the airplanes I’ve flown were accurate to the certification requirements, which specifically include the condition specified for doing the weight and balance.
 
Bell206 said:
No misunderstanding. It's really quite simple. If YOU know your current certified (signed) empty weight and balance record is not correct the aircraft is not airworthy as it doesn't meet it's TCDS conditions. In other words its not legal to fly. So are you stating YOU would fly a known unairworthy aircraft?
Click to expand...
In MY case, there IS no TCDS, so as long as I have some degree of confidence that the W&B is correct, both I and the airplane are fine. But an airplane with a TCDS might have some other requirement. Where is that requirement? I haven't found it yet. In what way would it be it unairworthy, exactly, if I have a known weight and balance sheet, regardless of who may or may not have signed it? If I have an empty weight and balance sheet from measurements I performed, what regulation says it's not valid? I'm not saying there isn't one, I'm just not enough of a jailhouse lawyer to have found it yet.
 
DaleB said:
Where is that requirement?...what regulation says it's not valid?
Click to expand...
No regulation. Here's the long version: as I mentioned above a current (certified) Empty Weight and Balance Record and Equipment List is a condition of the aircraft's type certification. Most "Note 1" in every TCDS states this as shown in the OPs Luscombe A-694:
upload_2020-1-20_16-52-24.png

A current EWBR/EL is also required for issuance of a AWC. The AWC only remains effective provided the aircraft is maintained per Part 21, 43, 91 as stated in AWC Block 6:
upload_2020-1-20_17-3-9.png

So if any aircraft repair or alteration is performed that causes over a +/- 1lb change, the EWBR must to be recomputed/re-certified for the aircraft to remain within its TC/TCDS condition in Note 1, i.e., airworthy condition. Also, if mx is not performed in accordance with Part 21, 43, 91 then the AWC is no longer "effective" which is a separate airworthiness issue.

EWBR/EL are one of the least understood airworthiness issues, yet one of the easiest to fix. If I'm not mistaken, even your E/AB required a current EWBR when it was issued a AWC? It's also one of the top 3 FAA ramp check items that ASIs love to check.
 
Skip Miller said:
My understanding is that unusable fuel is determined by the factory as follows: Test pilot flys on one tank, yanking and banking into multiple unusual attitudes. When the engine stumbles for lack of fuel, the test pilot levels off, switches to the other tank(s) and lands. Tank being tested is then filled full, and that amount is subtracted from the tank's capacity. That amount is unusable fuel. -Skip
Click to expand...

That would get the unusable at around 3/4 of a tank when he went into a hard slip. The requirement says that unusable fuel is that which will not drain from the tank to the engine in the attitude most critical for flight, and yanking/banking doesn't do much to the fuel unless you're really unccordinated. The intent is more the steep Vx climb or full-flap, power-off approach. If the fuel outlets are midway between the front and back of the inboard wall of the tank, there will be significant unusable fuel as it sloshes forward or back and unports the outlet. Some airplanes, like Citabrias and later 172s and a lot of larger Cessnas had outlets at the front and back, with the lines running down the doorposts and teeing together down low. Not much fuel unable to leave the tank in that setup. Low-wing airplanes won't have two outlets, as a pump is drawing the fuel out and if the pump gets air out of an unported outlet, no fuel gets moved.

The TCDS will often state the unusable fuel. If not, the required placards section will imply it. The placard at the fuel filler will show total fuel, and the placard at the selector will show usable. The difference is the unusable.

If the OP's Luscombe has wing tanks, I'd bet there's unusable fuel. The TCDS is silent on it.
 
Bell206 said:
No regulation. Here's the long version: as I mentioned above a current (certified) Empty Weight and Balance Record and Equipment List is a condition of the aircraft's type certification. Most "Note 1" in every TCDS states this as shown in the OPs Luscombe A-694:
View attachment 82084

A current EWBR/EL is also required for issuance of a AWC. The AWC only remains effective provided the aircraft is maintained per Part 21, 43, 91 as stated in AWC Block 6:
View attachment 82085

So if any aircraft repair or alteration is performed that causes over a +/- 1lb change, the EWBR must to be recomputed/re-certified for the aircraft to remain within its TC/TCDS condition in Note 1, i.e., airworthy condition. Also, if mx is not performed in accordance with Part 21, 43, 91 then the AWC is no longer "effective" which is a separate airworthiness issue.

EWBR/EL are one of the least understood airworthiness issues, yet one of the easiest to fix. If I'm not mistaken, even your E/AB required a current EWBR when it was issued a AWC? It's also one of the top 3 FAA ramp check items that ASIs love to check.
Click to expand...
My operating limitations require the W&B, yes. And there is one in the plane, and if I decide to re-weigh and create a new one, it replaces the one in the plane. I am quite well aware of the requirements for documentation, and it's all there.

I never once suggested not having a W&B sheet in the plane, and I'm not sure how we got onto that track. What I said was that, if the one in the plane was proven inaccurate when you weighted the plane yourself and calculated a new one, that you would want to use the W&B that you knew to be correct when flight planning. Now, if there is a requirement for the "official" W&B paperwork in the plane to be signed off by an A&P -- and I haven't found anything that says there is, but I'm not ruling out the possibility -- then I'd still use the numbers I knew to be correct. Period.

I note with interest that nowhere in the text you posted do the words "accurate" or "correct" appear. Only "current". My point is that if you suspect the current W&B is not correct, it might be a good ideal to create and use a new one that is both current and correct.
 
Anybody can determine (or make) an airplane UNairworthy. If you determine that there's a significant difference between the current W&B paperwork and reality, you'd best not fly the plane and consult an A&P.

I actually did all the math on my last W&B, but I had two A&Ps hanging around to sign off on it.
 
All auto-gas STCs must have a signed copy carried in the aircraft. when you look at the sheet it is the STC, It better be signed by a A&P-IA

but that is a different chapter :)

I have not seen a new W&B and equipment sheet that was not signed by a A&P, But it isn't mandatory.

when we do maintenance, aren't we required to sign it off. is writing in a log, are we doing maintenance

That would be a long discussion for a the FAA
 
Last edited:
Most single engine Cessna airplanes include unusable fuel and do not include engine oil.
 
DaleB said:
I never once suggested not having a W&B sheet in the plane, and I'm not sure how we got onto that track.
Click to expand...
I never was on that track? The only track I'm on is there is only one certified EWBR/EL for a TC'd aircraft which is issued by the OEM and altered by an A&P when necessary.
DaleB said:
Now, if there is a requirement for the "official" W&B paperwork in the plane to be signed off by an A&P
Click to expand...
Yes. As stated above it is a type certificate condition, i.e., the certification of the aircraft. It don't get any more important than that. To change that W&B certification it is considered a minor alteration which requires an A&P sign off. Plenty of FAA guidance on this.
DaleB said:
I note with interest that nowhere in the text you posted do the words "accurate" or "correct" appear. Only "current".
Click to expand...
No need. In FAA legal lingo... current means "accurate" and "correct." And as above there is plenty of FAA guidance on this also. ;)
 
So are we then to just assume that any W&B done by an A&P is correct? That would require somewhat more faith in the universal competence of mechanics than some of us have. So I'll say it again... if I weigh the airplane and calculate the W&B, using the correct methods and resulting in accurate numbers, and those numbers don't agree with the most recent numbers in the aircraft log (or the original, if it's never been superseded), then the one I just did is the current one. N'est-ce pas?
 
luvflyin said:
I’m having trouble getting my head wrapped around ”...drain the fuel until the fuel quantity gauges read empty when the aircraft is in level-flight attitude. Any fuel remaining in the system is considered residual or unusable fuel and is part of the aircraft empty weight." I would drain the tanks until ‘usable’ fuel is gone regardless of what the ‘gauges’ say.
Click to expand...

Just fly circles over the airport till it runs out of gas. Then weigh it....
Your unusable weight will be correct....
 
DaleB said:
So are we then to just assume that any W&B done by an A&P is correct?
Click to expand...
No.
DaleB said:
if I weigh the airplane and calculate the W&B, using the correct methods and resulting in accurate numbers, and those numbers don't agree with the most recent numbers in the aircraft log (or the original, if it's never been superseded), then the one I just did is the current one. N'est-ce pas?
Click to expand...
Ha. Key word above is "I." Your forgetting we're talking about the FAA. Legally, yours only counts in horseshoes, hand grenades and if you are an A&P and sign off/certify your "current" numbers in the aircraft weight and balance record. C'est la vie mon ami.;)
 
DaleB said:
So are we then to just assume that any W&B done by an A&P is correct? That would require somewhat more faith in the universal competence of mechanics than some of us have. So I'll say it again... if I weigh the airplane and calculate the W&B, using the correct methods and resulting in accurate numbers, and those numbers don't agree with the most recent numbers in the aircraft log (or the original, if it's never been superseded), then the one I just did is the current one. N'est-ce pas?
Click to expand...

Is weighing the airplane preventive maintenance? It isn't. Weighing an aircraft is a maintenance procedure and the manufacturer specifies procedures to weigh an aircraft correctly. An A&P is trained to accomplish a weighing of the aircraft, most owners aren't. Can an owner rig an aircraft's control cables? Can he balance a control surface? Now I'll admit that calculating a change in a weight and balance entry for the maintenance record might be a slightly gray area if all it is a math change but if it is as a result of a change in the equipment list such as legally uninstalling a radio, an A&P has to sign it off anyway.

As for what to do if the A&P does it incorrectly, find a better A&P.
 
Skip Miller said:
That would work if your fuel gauges were accurate. As we know, most are not.

My understanding is that unusable fuel is determined by the factory as follows: Test pilot flys on one tank, yanking and banking into multiple unusual attitudes. When the engine stumbles for lack of fuel, the test pilot levels off, switches to the other tank(s) and lands. Tank being tested is then filled full, and that amount is subtracted from the tank's capacity. That amount is unusable fuel. -Skip
Click to expand...

Yeah, most aren’t. And I ain’t about to be draining fuel from the tanks with the Master Switch turned on watching the gauge work it’s way down to empty.
 
My Cessna 175 says 52 gallons of fuel and 42 is usable. Kinda strange 5 gallons per side is unusable!
 
luvflyin said:
And your going to do that by looking at the fuel gauge???
Click to expand...
This isn't an issue of how much gas is in the tank. it is an issue of what the manual says to do.

do you know how to get every of gas your tanks. I will bet getting all the gas out isn't how you do W&B.
 
Bell206 said:
Yet the go-to FAA guidance on W&B changes (https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/media/FAA-H-8083-1.pdf) states this:
View attachment 82086
and...
View attachment 82087

While it may not be "mandatory" it is part of completing any repair or alteration that changes the aircraft weight more than a pound depending on aircraft type. Right?
Click to expand...

You are talking two different issues.
making entries of repairs and what a owner can enter in their logs.
43. make the rules when we sign maintenance entries.
There are no rules when the owners are making entries.
 
There is no positive way to know how much fuel is in any tank, except when full/empty. any other time it is a guess.
 
You must log in or register to reply here.
Back
Top