Gentlemen (and Ladies, if present),
All this discussion on CG moment arm made my weekend, an absolute hoot from
start
to finish (is it finished yet?). This is not helped by the rather cack-handed
approach prescribed in the POH.
A reasonably common piece of data in this thread is the location of the datum.
But even that may vary depending on who/how weighed/measured the aircraft -
treat
this as a variable across the fleet, but a constant for your aeroplane.
Any calculation of W&B needs to use the actual mass as measured and the actual
moment arm as measured.
Weigh the item (you, pax, the dog, grannies apple pie or your bag of birdseed).
Use that data in a spreadsheet.
Link:
http://www.lightaircraftassociation.co.uk/engineering/Weight%20and%20balance/w_and_b_main.html
Skydemon also provides a very nice W&B calculator (it is legally necessary to do
this for EVERY flight), which makes it easy-peazy.
The moment arm I use for baggage is a measurement to the centre of the bay.
However,
the Europa Aircraft method of establishing the FS 0.0 datum is a comedy.
A position 29.25" fwd of the "Rear of joggle for cowling in fuselage moulding"
needs to be marked.
This is totally unnecessary - the cowling to fuselage joint is as good a datum
as any. It requires all moment arms forward of it to be given a negative sign
(for the initial W&B calculation and any subsequent firewall forward mods) and
all those aft of it to be positive.
Just measure along the horizontal fuselage datum WL (level sill can be used as
per POH) to the FS of the item to be measured.
Attached is an extract from the POH (note the depicted Trigear also has a
secreted
mainwheel protruding from the fuselage!).
--------
John Wighton
Europa XS trigear G-IPOD
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=501290#501290
Attachments:
http://forums.matronics.com//files/europa_wandb_303.jpg
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