Today's Message Index:
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1. 12:37 AM - Re: CJ6A: stations for CG calculation (mgdimarco)
2. 06:24 AM - Blitz vid (Russ)
3. 07:22 AM - Re: Re: CJ6A: stations for CG calculation (cjpilot710@aol.com)
4. 08:52 AM - Re: Re: CJ6A: stations for CG calculation (dabear)
5. 09:22 AM - Re: This is serious flying..... (Dave \)
6. 02:58 PM - Re: Re: CJ6A: stations for CG calculation (Walter Lannon)
7. 05:24 PM - Re: CJ6A: stations for CG calculation (mgdimarco)
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| Subject: | Re: CJ6A: stations for CG calculation |
I have to admit some confusion on this issue. The w/b I had done has most of the
station numbers matching the 70" from firewall datum. However the oil my guy
used is at 48". The pilot station seems a bit aft when using 114.3. Seems to
measure out at around 104. Etc., Etc. and none of this matches the CJ manual
which seems to use the nose gear axle or the Leading edge of MAC.
What is the real answer on stations?
What is the MAC?
What is the LE of MAC station?
And what are the % LE of MAC limits really?
Thanks in advance
Mike
--------
Michael Di Marco
China Blue
407-348-4798
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=221448#221448
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Link might be incomplete?
http://vimeo.com/moogaloop.swf?clip_id=1778399&server=vimeo.com&
...Blitz
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| Subject: | Re: CJ6A: stations for CG calculation |
Mike,
I am away from home right now and not near my books. But the 70"
measurement is from the vertical (or second) firewall. IF my memory services
me right
the oil tank is about the 48" mark. The Chinese used a different method of
figuring C/G. I get home on the 1st or 2nd and will be able to help you. But
I'm sure others on this list have gone though this before.
Jim "Pappy" Goolsby
In a message dated 12/28/2008 3:38:24 A.M. Eastern Standard Time,
mgdimarco@yahoo.com writes:
--> Yak-List message posted by: "mgdimarco" <mgdimarco@yahoo.com>
I have to admit some confusion on this issue. The w/b I had done has most of
the station numbers matching the 70" from firewall datum. However the oil
my guy used is at 48". The pilot station seems a bit aft when using 114.3.
Seems to measure out at around 104. Etc., Etc. and none of this matches the
CJ manual which seems to use the nose gear axle or the Leading edge of MAC.
What is the real answer on stations?
What is the MAC?
What is the LE of MAC station?
And what are the % LE of MAC limits really?
Thanks in advance
Mike
--------
Michael Di Marco
China Blue
407-348-4798
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=221448#221448
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Gmail, and Yahoo Mail. Try it now.
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| Subject: | Re: CJ6A: stations for CG calculation |
Michael,
There is some discussion on the stations. However the MAC location, LE of
MAC, and limits really provided. I did a spreadsheet and put it on the RSPA
website if you want to down load it (and are a member). I built that after
gathering W/B information from 10 CJ pilots and a few A/Ps. I also did some
more measurements on the scales with known weights and positions. The
Spreadsheet also allows you to calculate the w/b of your aircraft from scale
points. Call me to discuss the process if you want.
Randy "DaBear" DeVere
571.213.4344
----- Original Message -----
From: "mgdimarco" <mgdimarco@yahoo.com>
Sent: Sunday, December 28, 2008 3:37 AM
Subject: Yak-List: Re: CJ6A: stations for CG calculation
>
> I have to admit some confusion on this issue. The w/b I had done has most
> of the station numbers matching the 70" from firewall datum. However the
> oil my guy used is at 48". The pilot station seems a bit aft when using
> 114.3. Seems to measure out at around 104. Etc., Etc. and none of this
> matches the CJ manual which seems to use the nose gear axle or the Leading
> edge of MAC.
>
> What is the real answer on stations?
>
> What is the MAC?
>
> What is the LE of MAC station?
>
> And what are the % LE of MAC limits really?
>
> Thanks in advance
> Mike
>
> --------
> Michael Di Marco
> China Blue
>
> 407-348-4798
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=221448#221448
>
>
>
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| Subject: | Re: This is serious flying..... |
Blitz: Who says we are a pack of ...????
http://www.youtube.com/watch?v=ppO3ilVeBFM
----- Original Message -----
From: ByronMFox@aol.com
To: yak-list@matronics.com
Sent: Saturday, December 27, 2008 1:51 PM
Subject: Yak-List: This is serious flying.....
By comparison, we're a pack of pussies.
http://vimeo.com/moogaloop.swf?clip_id=1778399&server=vimeo.com&
...Blitz
**************
One site keeps you connected to all your email: AOL Mail, Gmail, and
Yahoo Mail. Try it now.
lcom00000025)
Message 6
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| Subject: | Re: CJ6A: stations for CG calculation |
Mike:
MAC is the "mean aerodynamic chord" of the wing. If the wing has no taper,
no sweep and no variation in airfoil properties over the span the MAC and
the measured chord are one and the same. If the same plank wing is swept
the effective chord length is increased (relative to airflow direction). The
MAC is therefore longer and the position of the MAC leading edge has moved
aft. Taper also changes position and length of the MAC.
In the plan view the MAC location of a tapered and/or swept wing will be
located somewhere around the mid half-span point. This is of no interest for
weight and balance. We are concerned only with it's location in the
elevation view.
That location is shown by fig. 1.3, pg. 6 of the CJ6 Tech. Specs. manual.
The MAC leading edge is located 769 mm (30.27") forward of the main wheel
center line. It's length is 1747 mm (68.78").
The MW center is the primary reference point. It is not convenient to use as
the DATUM point for W&B which can be at the reference or at any point
established from it.
I use 125" forward of the MW center line as the DATUM. That keeps all
moments positive and greatly simplifies the math.
With that DATUM the LE of the MAC is at + 94.73" (125-30.27)
The forward limit (17% of MAC or 11.69") is at + 106.4" with the landing
gear DOWN
The aft limit ( 24.1% MAC or 16.57") is at + 111.3" " "
" " UP
With the gear UP the CG moves aft by 0.48".
As noted you can use any datum point but you MUST determine the MAC L/E
point from that datum.
The aircraft must be level (canopy rails). Should be levelled by jacking
NOT by deflating the nose oleo. That changes the MW to NW dimension which
you need for calculation. That dimension is given in Fig. 1.3 as 2233 mm
(87.9")
Use a clean floor, chalk line, masking tape and plumb bob, etc. Transfer MW
C/L to the aircraft C/L on the floor and establish DATUM from there.
Transfer cg of all load items to the floor for accurate measurement.
Cheers;
Walt
----- Original Message -----
From: "mgdimarco" <mgdimarco@yahoo.com>
Sent: Sunday, December 28, 2008 12:37 AM
Subject: Yak-List: Re: CJ6A: stations for CG calculation
>
> I have to admit some confusion on this issue. The w/b I had done has most
> of the station numbers matching the 70" from firewall datum. However the
> oil my guy used is at 48". The pilot station seems a bit aft when using
> 114.3. Seems to measure out at around 104. Etc., Etc. and none of this
> matches the CJ manual which seems to use the nose gear axle or the Leading
> edge of MAC.
>
> What is the real answer on stations?
>
> What is the MAC?
>
> What is the LE of MAC station?
>
> And what are the % LE of MAC limits really?
>
> Thanks in advance
> Mike
>
> --------
> Michael Di Marco
> China Blue
>
> 407-348-4798
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=221448#221448
>
>
>
Message 7
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| Subject: | Re: CJ6A: stations for CG calculation |
My understanding is making real progress. Thanks for the definition of MAC, but
I was looking for a value and the best I could determine was 68.8 which is right
in line with the 68.78 answer.
Is the 94.7 LE of MAC the same as the datum of 70" forward of the firewall?
Anyone see the Pilot station as being closer to 104" than 114.3" from that datum?
Thanks for the confirmation of the oil tank at 48" on the 70" datum.
How about the "cargo" compartment. Would you use the battery location or just
aft of it as the center?
In case anyone is interested, what started this was my head scratching as to why
I could not but a 240# pilot and a 280# co-pilot in a 2412# airplane with only
140# of gas and 25# of oil. I kept getting a 116.7" C.G. (out of limit aft).
It is not the case if the pilot station is at 104 (as I measure it) vs. 114.3
which seems to be the standard answer.
Thanks again in advance for the help and your replies.
Mike
--------
Michael Di Marco
China Blue
407-348-4798
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=221528#221528
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