Everyone has it wrong about Unusable Fuel

[Aerodon]

23 hours ago, PilotX said:

I'm still not buying your 74 lb weight loss.  A KFC150 autopilot is 27 lbs installed, all my avionics are 56 lbs installed (including the KFC150) (very similar) and I expect to put back about 30 lbs.  Maybe a 25 lb saving.  I've seen Beech guys brag about a 25 lb reduction.

Was it calculated or weighed?

 

Aerodon

[PilotX]

4 minutes ago, Aerodon said:

I'm still not buying your 74 lb weight loss.  A KFC150 autopilot is 27 lbs installed, all my avionics are 56 lbs installed (including the KFC150) (very similar) and I expect to put back about 30 lbs.  Maybe a 25 lb saving.  I've seen Beech guys brag about a 25 lb reduction.

Was it calculated or weighed?

 

Aerodon

I will not be able to sleep because of your doubts.  We weighed 17 lbs of wires. I pulled nearly 10 lbs of antennas (ADF, RA, etc) Believe what you want I was there when it was weighed. How much do you think an EHI40 weighs?

[kortopates]

So after I criticized weighing the plane with full fuel and subtracting - I went and looked at my own paperwork and thats exactly what the factory did. (at least they weighed it). In general I find the Mooney factor W&B poor, it is not very detailed.  Piper and Cessna list every single option along with a weight and arm, so it is pretty easy to do a desktop revision.  And the factory typically did a desktop calculation for the plane before they sold it.
Aerodon

Mooney’s equipment list includes every conceivable piece of equipment with the arm and weight too.
what year did they weight your plane with full fuel?
once the tanks have had maintenance it’s doubtful they hold precisely the same amount of fuel they originally did and it seems folks fill there tanks to different “full” levels.


Sent from my iPhone using Tapatalk

[philiplane]

I looked through more than two dozen re-weighs that I've done after extensive avionics work on customer's planes. Including vacuum system removals.

The average calculated weight loss was 22 pounds. The average actual loss, once on scales, was almost never a loss of weight. Due to previous errors, and due to paint & interior work, heavier tires, etc, that all added to the factory weight without being caught. One or two came in at a net zero weight change, even after having removed 20-30 pounds of old things versus the weight of the new equipment going in.

The highest real weight loss was a Cheyenne 400. We removed over 200 pounds of original equipment & wiring. That was replaced by about 80 pounds of new equipment. So, a 120 pound useful load gain on a 12,000 pound plane. And it moved the CG back over an inch, due to the removal of all the remote mounted avionics and wiring in the nose.

So the lesson is, if you want to see a weight loss after upgrades, calculate it, don't weigh it.

Edited November 18, 2021 by philiplane

[EricJ]

21 minutes ago, kortopates said:

Mooney’s equipment list includes every conceivable piece of equipment with the arm and weight too.
 

My 77 J is like that, and the updates to the Equipment List have just been crossing out stuff on the original factory list and adding new items with the new pages in the W&B.

If and when the TT AP ever comes out I'll reweigh it and make a new list as it's getting pretty ratty.

[philiplane]

One important thing to note- you really can't remove enough weight on a piston single to make any measurable difference. Even 50 pounds doesn't make a real difference. You would need to remove 100-200 pounds to notice any difference in climb rate or cruise speed. It's just not possible, even with the most minimal approach to equipment, lightweight upholstery, carpet, etc. Look at what crazy lengths the Alaskan Super Cub operators go to, to cut weight. And they still have a 2 place airplane that climbs great, but it is slow, VFR only, and it is completely uncomfortable. Great for dropping in on a river sand bar to go fishing, but that's about it.

Worry more about the CG, that is more important than losing 2 pounds by replacing one radio for another.

[Aerodon]

57 minutes ago, kortopates said:

Mooney’s equipment list includes every conceivable piece of equipment with the arm and weight too.
what year did they weight your plane with full fuel?
once the tanks have had maintenance it’s doubtful they hold precisely the same amount of fuel they originally did and it seems folks fill there tanks to different “full” levels.


Sent from my iPhone using Tapatalk

OK, found the detailed Mooney list in the AFM, I was looking at the factory W&B form.  Dealing with a 1986 252.

 

Aerodon

[hammdo]

32 minutes ago, EricJ said:

My 77 J is like that, and the updates to the Equipment List have just been crossing out stuff on the original factory list and adding new items with the new pages in the W&B.

If and when the TT AP ever comes out I'll reweigh it and make a new list as it's getting pretty ratty.

I just went through this - newly reweighed plane and re-did the equipment list with station/arm/moment. That was a lot of work - including all the 337 upgrades (speed mods).

-Don

[jaylw314]

23 minutes ago, philiplane said:

One important thing to note- you really can't remove enough weight on a piston single to make any measurable difference. Even 50 pounds doesn't make a real difference. You would need to remove 100-200 pounds to notice any difference in climb rate or cruise speed. It's just not possible, even with the most minimal approach to equipment, lightweight upholstery, carpet, etc. Look at what crazy lengths the Alaskan Super Cub operators go to, to cut weight. And they still have a 2 place airplane that climbs great, but it is slow, VFR only, and it is completely uncomfortable. Great for dropping in on a river sand bar to go fishing, but that's about it.

Worry more about the CG, that is more important than losing 2 pounds by replacing one radio for another.

And the CG stuff is hard to mess up with fuel since the fuel sits pretty much right in the CG range for Mooneys

[philiplane]

1 hour ago, jaylw314 said:

And the CG stuff is hard to mess up with fuel since the fuel sits pretty much right in the CG range for Mooneys

Actually, weighing it incorrectly with full fuel magnifies CG errors. Failing to level the plane properly can throw the CG off by an inch. All of the gross CG errors that I have found were in planes weighed with full fuel, then calculated out. I did a demonstration of this one time, for a group of A&P students. We pushed an Apache on the scales, did the weight & balance with unusable fuel first. Then fueled the plane (108 gallons), weighed it again, and calculated it out. We came up with a 60 pound error, and I showed them how a minor difference in the leveling would move weight on or off the nose wheel. 

[EricJ]

The main utility of using the full fuel method is that many people/places don't have a practical means of defueling the airplane, either due to equipment/storage limitations or regulatory/rules limitations on the airport.   Done with reasonable care using full fuel is, imho, definitely a suitable option.   If one is practically able to drain the tanks and assure that the quantity remaining in the tanks matches the TCDS unusable quantity, it can reduce one of the many sources of potential errors in weighing the airplane.  

 

[cliffy]

15 hours ago, EricJ said:

You may be confusing measurement units with a calibration standard, I can't tell.  Tool calibration standard examples are published by SAE, ISO, NIST, etc.   The FAA doesn't specify which to use, just that one must be used when one is required to do so, like for Part 145 Repair Stations or 135 or 121 operators

Don't all the "standards" trace back to a US "standard measurement"?

[EricJ]

11 minutes ago, cliffy said:

Don't all the "standards" trace back to a US "standard measurement"?

Do you mean to US (SAE?) or Imperial units?   No, why would they?   Most of the world uses the metric system.

 

Edited November 17, 2021 by EricJ

[Hank]

27 minutes ago, cliffy said:

Don't all the "standards" trace back to a US "standard measurement"?

No. Some trace back to NIST, some to SAE, some to other standards. ISO is pretty much global, based on millimeters and grams.

[Ragsf15e]

7 hours ago, kortopates said:

Mooney’s equipment list includes every conceivable piece of equipment with the arm and weight too.
what year did they weight your plane with full fuel?
once the tanks have had maintenance it’s doubtful they hold precisely the same amount of fuel they originally did and it seems folks fill there tanks to different “full” levels.


Sent from my iPhone using Tapatalk

I wish mine had that kind of weight and balance info… ‘68 F.  Weighed at the factory with full fuel.  First mod is at the factory too (electric gear).  First mistake is also at the factory (subtracted elec gear weight instead of added), caught and corrected in pen.  No equipment list other than what I created.  If I had someone around here to help me re-weigh that I trusted, I’d do it.  There have been lots of changes!

[MikeOH]

Ok, you reweigh your plane and come up with a new weight and CG.  What happens to your W&B sheet?  Does all the listed equipment 'disappear' into a single conglomerate number? How do you assign new weights and arms?  Or, do you 'assume' they are all correct (tee-hee-hee) and just 'fudge' the empty weight and CG?

[PT20J]

1 hour ago, MikeOH said:

Ok, you reweigh your plane and come up with a new weight and CG.  What happens to your W&B sheet?  Does all the listed equipment 'disappear' into a single conglomerate number? How do you assign new weights and arms?  Or, do you 'assume' they are all correct (tee-hee-hee) and just 'fudge' the empty weight and CG?

You are supposed to update the equipment list with weights and location when equipment is added or deleted.

[PT20J]

Here’s my result for a 1994 M20J:

As delivered from the factory, empty weight 1948 lb., CG 46.1”

As weighed after panel/autopilot retrofit: 1895 lb., 46.06”

Skip

[EricJ]

1 hour ago, MikeOH said:

Ok, you reweigh your plane and come up with a new weight and CG.  What happens to your W&B sheet?  Does all the listed equipment 'disappear' into a single conglomerate number? How do you assign new weights and arms?  Or, do you 'assume' they are all correct (tee-hee-hee) and just 'fudge' the empty weight and CG?

You should still have all of the installed equipment on existing lists, and if you don't add, subtract, or move anything those can be re-used.    You can always correct errors if you find them.   The weighing process gives you a new empty weight and CG, which you update to be your new W&B sheet.   So new EW and CG from the scales, equipment list is just whatever it was before but can be re-compiled into a new list using the previous data if desired.    It is the owner's responsibility to maintain the list.

 

[jaylw314]

2 hours ago, PT20J said:

You are supposed to update the equipment list with weights and location when equipment is added or deleted.

Is my understanding correct that the equipment list data does not have to be reconciled with the actual weight and balance?  E.g., it is only there for the factory to calculate the weight and balance, but if you actually weigh and balance the plane, all the previous calculations are superseded?

And today I learned that "superseded" is the correct spelling, not "superceded"  

[Aerodon]

10 hours ago, jaylw314 said:

Is my understanding correct that the equipment list data does not have to be reconciled with the actual weight and balance?  E.g., it is only there for the factory to calculate the weight and balance, but if you actually weigh and balance the plane, all the previous calculations are superseded?

And today I learned that "superseded" is the correct spelling, not "superceded"  

In my 1980 Piper Seneca, the W&B section starts with a 'basic airplane' and then starts listing various standard and optional items, along with a note whether it is A -Required, B - Required or may be replaced with optional, or C- Optional. For example, the engine weight and arm is listed as A (interesting but not really relevant because you cam't change it?), the propeller could be B (2 bladed) or C (optional 3 bladed). The factory stamped an X next to all installed options and then weighed the plane.  This makes it real easy to update the W&B by recalculating instead of reweighing.

My 1986 Mooney has a list of items, weights and arms in the POH.  But the factory W&B form is kinda basic.  My plan is to type up a very detailed spreadsheet showing everything that is installed, and then re-weigh the plane. The more detail (weights and arms) with the equipment the list, the better it is for the next guy.  But they do not form part of the calculation if the plane is reweighed.

Aerodon

[Hank]

Just now, Aerodon said:

The more detail (weights and arms) with the equipment the list, the better it is for the next guy.  But they do not form part of the calculation if the plane is reweighed.

That will make life much easier when any installed equipment is removed or replaced!

[PT20J]

An Airplane Flight Manual that follows the GAMA Pilot's Operating Handbook Specification has a Weight and Balance Section 6 that contains the Equipment List as delivered and a Owner's Weight and Balance Record with the first entry having the Empty Weight, Moment/1000, Arm, and Useful Load as delivered. The idea is to update the Owner's page whenever equipment is added or removed. This form is inconvenient to use if more than one item is removed or installed.

Instead, most IAs use a computerized W&B program that lists equipment added or removed and calculates new weight and CG. The normal practice when a new W&B is calculated is to write "Superseded (date)" on the previous printout and include the new printout. Keeping all the printouts provides a history of all the equipment added or deleted. 

However, if the airplane is reweighed, the programs will not generally include any equipment removed or installed. In this case, you can just manually update the equipment list, or create a new one. I do not believe that there is any regulatory requirement to do this, but I find it satisfying to have a current list of the equipment installed in the airplane.

Skip

[Greg Ellis]

All this talk about re-weighing, weight and balance etc... got me to thinking.  So I went back to the original weight and balance in the AFM of my 1963 C model.  Very interesting and a little confusing.  They did multiple calculations at different CG positions (most forward, full fuel, most rearward, etc...)  Whoever did the calculations transposed the last 2 numbers on his/her multiplication.  For instance, Empty weight of 1575 X Arm of 44.9 should equal a moment of 70717.5, rounded up to 70718.  Well, they put down a moment of 70781.  On the gross weight of 2575 X Arm of 49 should be a moment of 126175.  They put down 126157.  I think I may go back and rework the math and see what happens, unofficially of course.

[Shadrach]

On 11/17/2021 at 8:07 PM, Ragsf15e said:

I wish mine had that kind of weight and balance info… ‘68 F.  Weighed at the factory with full fuel.  First mod is at the factory too (electric gear).  First mistake is also at the factory (subtracted elec gear weight instead of added), caught and corrected in pen.  No equipment list other than what I created.  If I had someone around here to help me re-weigh that I trusted, I’d do it.  There have been lots of changes!

I've always wondered what the difference was.  Can you shed some light on the weight difference between electric and manual gear?