weight and balance

Post-War Aeronca Champ airplanes
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jackshulerdds
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weight and balance

Post by jackshulerdds » Wed Jul 15, 2009 18:24

I have an aeronca champ 7AC. It was rebuilt in l996. The airplane, according to FAA records, has not been "weight and balanced" since l969, and these figures have been lost.
My mechanic will borrow scales, but needs to know two things:
l. How is "level flight attitude" determined? Where do you put the level when the tail is picked up.
2. Where is the datum located?
Anybody know anything about this? Apparently this is supposed to be in the airplane to make it legal.
Thanks
Doc

Mnflyer
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Post by Mnflyer » Wed Jul 15, 2009 18:47

Hi Doc, your A&P needs to get familiar with a number of important documents, one of the most important being the Aircraft Type Certificate Data Sheets they have all the information on leveling the aircraft and where the datum is located, another very good document to have would be the FAA CD of historical records for the aircraft, and last a maintenance manual is needed.
I believe the maintenance manual can be purchase here at this site, the TCDS and the aircraft records CD are available here:
http://www.faa.gov/aircraft/
GB MN.Flyer
Flying a Champ 7DC and a HKS Kitfox III

Dennis
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Post by Dennis » Wed Jul 15, 2009 21:34

Here is one I did today for a 7AC converted to a 7ECA. I would appreciate input. Even though it is converted to an ECA, the STC requires that the specs for a 7CCM be used. Notice I had to load one gal of fuel in the wing tank to get the aft CG at full load within the envelope. Sorry about the way the columns screwed up.

W/B done in accordance with STC-SA3-372
Brought up to Model 7CCM - 90 HP configuration


CG Range: +16.8 to 20.0 @ 1300 lbs
CG Range: +10.0 to 20.0 @ 1087 lbs or less
Straight Line variation between points

Max weight: 1300 Lbs
Two seats @ +11.5" and +42"; Solo front seat
Max baggage: 50 lbs @ 64"

_______________________________________________________________________
EMPTY WEIGHT CG

WEIGHT ARM MOMENT

L WHEEL 411 -0.25 - 102.8
R WHEEL 420 -0.25 - 105.0
T WHEEL 68 198.5 13498.0
_____ ________

899 13,290.2

EMPTY CG: 13,290.2 / 899 = 14.78
=====
USEFULL LOAD: 1300 - 899 = 401 LBS.
=======

_____________________________________________________________________________
MAXIMUM FORWARD CG

WEIGHT ARM MOMENT

EMPTY WEIGHT 899 14.78 13,290.2
SOLO FT. SEAT 170 11.5 1940.0
FUEL, 13 GAL @ NOSE 78 -15.0 -1170.0
_____ ________

1147 14,060.2

MAXIMUM FORWARD CG: 14,060.2 / 1147 = 12.25
=====

__________________________________________________________________________________
MAXIMUM AFT CG

WEIGHT ARM MOMENT

EMPTY WEIGHT 899 14.78 13,290.2
SOLO FT. SEAT 170 11.5 1940.0
PASSENGER 170 42.0 7140.0
FUEL, 9 GAL @ NOSE 54 -15.0 - 810.0
FUEL, 1 GAL @ WING 6 58.0 348.0
_____ ________

1299 21,908.2

MAXIMUM AFT CG: 21,908.2 / 1299 = 16.9
=====



Dennis

Roger Anderson
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Post by Roger Anderson » Thu Jul 16, 2009 06:01

Yes. The W & B is a required document to be carried on the aircraft. When you go to the FAA web site, The Aeronca ownership now is by American Champion. That's where you will locate Champs, etc. Here's a direct link. Click on "by make" then look for American Champion.

http://www.airweb.faa.gov/Regulatory_an ... enFrameSet


The type certificate also says that for leveling, "any portion of the cabin floor to level....."
Last edited by Roger Anderson on Thu Jul 16, 2009 12:53, edited 1 time in total.

Dennis
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Post by Dennis » Thu Jul 16, 2009 08:12

Doc,

Sorry not to answer your main questions. The datum is the wing leading edge and all weight measurements are to be made with the plane as in level flight. The mains are located at -0.25". In other words, in front of the datum. I have seen several examples where the location of the mains are rounded off 0.0".

Dennis

gusc
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Post by gusc » Fri Jul 17, 2009 22:21

As I remember level is measured at the floor board or the window ledge.
Gus Causbie
Ash Flat, AR
N83564, 7AC-2235, A65-8

jkvincent
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Re: weight and balance

Post by jkvincent » Sun Aug 23, 2009 20:15

Hello Dennis,
I'm doing my Weight & Balance (as we speak), I believe I've seen it before but can't seem to find specifily
where (you identify)the wheels as being forward, in other words -.25", The TCDS shows the gear, all taildragger models at "0".
With my Champ level, my wheels are actually aft of datum, in other words "+"
Jim
PS: how's that "good lookin" Red Champ comin' along?

Image

Dennis
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Re: weight and balance

Post by Dennis » Mon Aug 24, 2009 10:05

Hey Jim

Good to hear from you. Looking at my TCDS on the CD for my plane, the wheels are clearly shown as 0.25" in front of the Datum and calculations are made using the negative distance of 0.25". However, if I recall correctly, in Buzz Wagners calculations, he rounded it off to 0.0. I also saw other examples where it was rounded to zero.

I am sorry to report that work is not progressing on the wings. I am one lazy SOB.

Dennis

flyingfool
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Re: weight and balance

Post by flyingfool » Mon Aug 24, 2009 14:06

Just speculating. Are you sure you're measuring level from the correct reference. I would think it is possible to change the location of the point measured perpendicular from this reference and your leading edge quite a little bit as it rotates around the axle.

You're probably doing it right but just thought I'd throw in my 1 cent.

On a chief there is some discussion about where to level from. The TCDS says to measure from the floorboard. However mine and others are in two peices that are meet at an angle. So measure from which one? Others state that the bottom of the door frame is the level reference.

I'll have to try this some day!

ablight
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Re:

Post by ablight » Tue Jan 12, 2010 13:24

Dennis wrote:Here is one I did today for a 7AC converted to a 7ECA. I would appreciate input. Even though it is converted to an ECA, the STC requires that the specs for a 7CCM be used. Notice I had to load one gal of fuel in the wing tank to get the aft CG at full load within the envelope. Sorry about the way the columns screwed up.

W/B done in accordance with STC-SA3-372
Brought up to Model 7CCM - 90 HP configuration


CG Range: +16.8 to 20.0 @ 1300 lbs
CG Range: +10.0 to 20.0 @ 1087 lbs or less
Straight Line variation between points

Max weight: 1300 Lbs
Two seats @ +11.5" and +42"; Solo front seat
Max baggage: 50 lbs @ 64"

_______________________________________________________________________
EMPTY WEIGHT CG

WEIGHT ARM MOMENT

L WHEEL 411 -0.25 - 102.8
R WHEEL 420 -0.25 - 105.0
T WHEEL 68 198.5 13498.0
_____ ________

899 13,290.2

EMPTY CG: 13,290.2 / 899 = 14.78
=====
USEFULL LOAD: 1300 - 899 = 401 LBS.
=======

_____________________________________________________________________________
MAXIMUM FORWARD CG

WEIGHT ARM MOMENT

EMPTY WEIGHT 899 14.78 13,290.2
SOLO FT. SEAT 170 11.5 1940.0
FUEL, 13 GAL @ NOSE 78 -15.0 -1170.0
_____ ________

1147 14,060.2

MAXIMUM FORWARD CG: 14,060.2 / 1147 = 12.25
=====

__________________________________________________________________________________
MAXIMUM AFT CG

WEIGHT ARM MOMENT

EMPTY WEIGHT 899 14.78 13,290.2
SOLO FT. SEAT 170 11.5 1940.0
PASSENGER 170 42.0 7140.0
FUEL, 9 GAL @ NOSE 54 -15.0 - 810.0
FUEL, 1 GAL @ WING 6 58.0 348.0
_____ ________

1299 21,908.2

MAXIMUM AFT CG: 21,908.2 / 1299 = 16.9
=====



Dennis


Dennis, what equipment does this airplane have installed? Electrical system, engine model, etc.... I am trying to reduce weight in my airplane. Andy

Dennis
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Re: weight and balance

Post by Dennis » Tue Jan 12, 2010 15:26

Andy,

The plane I did the W&B for belongs to a friend. It is equipped with an 0200A with a metal prop, starter, alternator and a battery plus some avionics.

Dennis

ablight
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Re: weight and balance

Post by ablight » Wed Jan 13, 2010 07:05

Dennis wrote:Andy,

The plane I did the W&B for belongs to a friend. It is equipped with an 0200A with a metal prop, starter, alternator and a battery plus some avionics.

Dennis
Dennis what model starter, alternator, and battery did they use? Thanks Andy

Dennis
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Re: weight and balance

Post by Dennis » Wed Jan 13, 2010 10:58

Andy,

Gee, I don't know. I will find out the next time I see him.

Dennis

ablight
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Re: weight and balance

Post by ablight » Thu Jan 14, 2010 06:57

Thanks Dennis :D , Andy

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