Blanik L-13 Weight and Balance

We need to get a weight and balance done for our Blanik L-13. The
manuals are not really helpful referring to percentage of MAC (mean
aerodynamic chord) for the CG range without saying how much MAC is
nor where the reference plane/datum is (probably the wing root rib).

I dug up the FAA type certificate that actually uses the "most forward
point on fuselage nose" as the datum and specifies the arm for front
and back pilot plus the C/G range relative to that datum which should
give me all the info needed to do the calculations for minimum single
pilot weight etc. Only problem is that the FAA type certificate states
that the leveling means for weighing the glider are "between points
marked on side of fuselage". Now that is not very helpful either since
ours has been painted several times and the manual doesn't make you
any wiser either as to where those points are.

Does anyone out there know how to establish the proper leveling of the
Blanik L-13 when weighing it or has a better method for doing the
weight and balance for that glider?

Thanks in advance for any help you can provide,

Markus Graeber
Aeroclub de Colombia

I do not have our old copy of the L-13 Manuals handy.. they are out at the
club. I only have my L-23 manuals here.

If I remember correctly there should be two "set screws" or larger than
standard rivets along the horizontal rivet line of the fuselage aft of the
wing. These reference points should be easily noticed and not trusting to
staying with paint.
The maintenance manual should have explicit instructions for weighing the
L-13.

BT

"Markus Graeber" wrote in message
...
We need to get a weight and balance done for our Blanik L-13. The
manuals are not really helpful referring to percentage of MAC (mean
aerodynamic chord) for the CG range without saying how much MAC is
nor where the reference plane/datum is (probably the wing root rib).

I dug up the FAA type certificate that actually uses the "most forward
point on fuselage nose" as the datum and specifies the arm for front
and back pilot plus the C/G range relative to that datum which should
give me all the info needed to do the calculations for minimum single
pilot weight etc. Only problem is that the FAA type certificate states
that the leveling means for weighing the glider are "between points
marked on side of fuselage". Now that is not very helpful either since
ours has been painted several times and the manual doesn't make you
any wiser either as to where those points are.

Does anyone out there know how to establish the proper leveling of the
Blanik L-13 when weighing it or has a better method for doing the
weight and balance for that glider?

Thanks in advance for any help you can provide,

Markus Graeber
Aeroclub de Colombia

At 03:36 22 January 2008, Bt wrote:
I do not have our old copy of the L-13 Manuals handy..
they are out at the
club. I only have my L-23 manuals here.

If I remember correctly there should be two 'set screws'
or larger than
standard rivets along the horizontal rivet line of
the fuselage aft of the
wing. These reference points should be easily noticed
and not trusting to
staying with paint.
The maintenance manual should have explicit instructions
for weighing the
L-13.

BT

'Markus Graeber' wrote in message
.
com...
We need to get a weight and balance done for our Blanik
L-13. The
manuals are not really helpful referring to percentage
of MAC (mean
aerodynamic chord) for the CG range without saying
how much MAC is
nor where the reference plane/datum is (probably the
wing root rib).

I dug up the FAA type certificate that actually uses
the 'most forward
point on fuselage nose' as the datum and specifies
the arm for front
and back pilot plus the C/G range relative to that
datum which should
give me all the info needed to do the calculations
for minimum single
pilot weight etc. Only problem is that the FAA type
certificate states
that the leveling means for weighing the glider are
'between points
marked on side of fuselage'. Now that is not very
helpful either since
ours has been painted several times and the manual
doesn't make you
any wiser either as to where those points are.

Does anyone out there know how to establish the proper
leveling of the
Blanik L-13 when weighing it or has a better method
for doing the
weight and balance for that glider?

Thanks in advance for any help you can provide,

Markus Graeber
Aeroclub de Colombia



These set screws must be the datum points. See the
BGA datasheet for the Blanik L-13
http://www.gliding.co.uk/bgainfo/tec...ets/blanik.pdf


Gavin
Std Cirrus, CNN now G-SCNN, #173

Use the "Top of rear fuselage tail down 1000:51". It is a good idea to
cut this angle out of cardboard or plywood and keep it for future W&B
purposes. The Standard Jantar manual tells us to "level the cord
line". OK, fine, now how do we do that? The only way I could figure
was to make a full template from a large piece of cardboard, made to
fit the root rib with wing removed, then scribe the cord line (exact
leading edge to trailing edge).Then raise this cord line 8" and mark a
"raised" cord on top of the template. Then cut along the raised cord
line, so's I had a place to put my bubble level. Assemble the bird,
slip on the template, raise the tail to achieve bubble level on the
"raised" cord line. Wow, thanks for making it sooooo easy PZL. After
going through all this........................make a simple triangle
to go on the top aft boom, that shows bubble level when the ship is in
the proper position.
JJ

On Jan 22, 1:05*am, Gavin Short
wrote:
At 03:36 22 January 2008, Bt wrote:



I do not have our old copy of the L-13 Manuals handy..
they are out at the
club. I only have my L-23 manuals here.

If I remember correctly there should be two 'set screws'
or larger than
standard rivets along the horizontal rivet line of
the fuselage aft of the
wing. These reference points should be easily noticed
and not trusting to
staying with paint.
The maintenance manual should have explicit instructions
for weighing the
L-13.

BT

'Markus Graeber' *wrote in message
.
com...
We need to get a weight and balance done for our Blanik
L-13. The
manuals are not really helpful referring to percentage
of MAC (mean
aerodynamic chord) *for the CG range without saying
how much MAC is
nor where the reference plane/datum is (probably the
wing root rib).

I dug up the FAA type certificate that actually uses
the 'most forward
point on fuselage nose' as the datum and specifies
the arm for front
and back pilot plus the C/G range relative to that
datum which should
give me all the info needed to do the calculations
for minimum single
pilot weight etc. Only problem is that the FAA type
certificate states
that the leveling means for weighing the glider are
'between points
marked on side of fuselage'. Now that is not very
helpful either since
ours has been painted several times and the manual
doesn't make you
any wiser either as to where those points are.

Does anyone out there know how to establish the proper
leveling of the
Blanik L-13 when weighing it or has a better method
for doing the
weight and balance for that glider?

Thanks in advance for any help you can provide,

Markus Graeber
Aeroclub de Colombia

These set screws must be the datum points. *See the
BGA datasheet for the Blanik L-13
*http://www.gliding.co.uk/bgainfo/tec...ets/blanik.pdf

Gavin
Std Cirrus, CNN now G-SCNN, #173- Hide quoted text -

- Show quoted text -

I love it... "1000:51 at top of aft fuselage". Not 20:1 or anything
simple like that. "Okay George, up on the tail about 2MM. Wait...
no, down a 1MM. Nope, nope back up 1MM... "

Actually, it doesn't make any difference. Just put a mark on the fufelage,
and put a 5.1mm drill 100mm aft the mark. Place bubble level on the drill,
with one edge resting on the mark.

Oh, only got drills sized in inches in your workshop ?...

Bert

"Papa3" wrote in message
...
- Show quoted text -

I love it... "1000:51 at top of aft fuselage". Not 20:1 or anything
simple like that. "Okay George, up on the tail about 2MM. Wait...
no, down a 1MM. Nope, nope back up 1MM... "

On Jan 22, 7:24 am, Papa3 wrote:
I love it... "1000:51 at top of aft fuselage". Not 20:1 or anything
simple like that. "Okay George, up on the tail about 2MM. Wait...
no, down a 1MM. Nope, nope back up 1MM... "

Um... Get a 1 meter long stick (metric yardstick?), set it on top if
the fuselage, raise rear end 51mm and viola!

-Tom

On Jan 22, 9:42*am, "Bert Willing" bw_no_spam_ple...@tango-
whisky.com wrote:
Actually, it doesn't make any difference. Just put a mark on the fufelage,
and put a 5.1mm drill 100mm aft the mark. Place bubble level on the drill,
with one edge resting on the mark.

Oh, only got drills sized in inches in your workshop ?...

Bert

"Papa3" wrote in message

...

- Show quoted text -

I love it... "1000:51 at top of aft fuselage". * *Not 20:1 or anything
simple like that. * *"Okay George, up on the tail about 2MM. *Wait....
no, down a 1MM. * Nope, nope back up 1MM... "

Okay, maybe should have included the :-) But, since we're all so
serious, someone with a Blanik go calculate the difference that .1MM
makes given the mass of the beast. Then, eliminate the calibaration
errors in scales, location of the seat belt buckles, inflation of the
oleo (which will change the angle with the tail wheel) yadda yadda
yadda. I think the point was the level of precision implied by
1000:51 is laughable given the realities of conducting a W&B

Cheers,
Erik

Thanks for everybody who has responded, especially Dick and Tim who
sent me photos and a W&B sheet. I wasn't able to actually find the
dimples that mark the level plane on either side of the fuselage so I
ended up using the info in the BGA data sheet and leveled the aft
fuselage to 1000:51 downwards (1000mm:51mm level - and yeah, it was
exactly 5.1 mm down as in the diameter of a twig ;-) using the tip of
the nose cone as the reference datum (to hell with the MAC, wherever
it is supposed to be...) and the data for the arms contained in the US
Type Certificate (which specifies the arm for front & back pilot as
well as for the baggage compartment).

Turns out that our min single pilot weight went up from the original
68 kg to now 72 kg to stay within the CG range, probably largely to
the sturdy tail wheel with aluminum fairing the club had mounted on
the tail a long time ago in lieu of the joke that came from the
factory.

Thanks again everybody for helping to get this sorted out quickly.

Markus

El lunes, 21 de enero de 2008, 20:26:45 (UTC-3), Markus Graeber escribió:
We need to get a weight and balance done for our Blanik L-13. The
manuals are not really helpful referring to percentage of MAC (mean
aerodynamic chord) for the CG range without saying how much MAC is
nor where the reference plane/datum is (probably the wing root rib).

I dug up the FAA type certificate that actually uses the "most forward
point on fuselage nose" as the datum and specifies the arm for front
and back pilot plus the C/G range relative to that datum which should
give me all the info needed to do the calculations for minimum single
pilot weight etc. Only problem is that the FAA type certificate states
that the leveling means for weighing the glider are "between points
marked on side of fuselage". Now that is not very helpful either since
ours has been painted several times and the manual doesn't make you
any wiser either as to where those points are.

Does anyone out there know how to establish the proper leveling of the
Blanik L-13 when weighing it or has a better method for doing the
weight and balance for that glider?

Thanks in advance for any help you can provide,

Markus Graeber
Aeroclub de Colombia


Do you have a data for L23 weight and balance?
thanks!!