CG and baggage compartment
have no professional or expert qualifications of any kind.
It's fully up to you to check any information you
find here with
standard aviation industry sources such as
manuals, flying instruction books and, above all,
I am by no means a specialist in approval
But I understand that
original parts do not need approval , since the plane was licensed that
A logbook entry would be sufficient here.
If you think about using parts from a Forney , that was using the flat
shelf, then it is for the officials, similar to using parts from a Cessna,
or a Harley - NOT APPROVED! And in need of a 337 at least.
So who ever that idiot was, that was
cutting out those windows needs to be spanked first and then you might
think about a way to live with the approved baggage compartment.
The tilting hat shelf was in there with a
It disallows storage of items further aft
CG than the canvas bag does.
The CG calculations of a Stock coupe allow
to neglect any further CG calculations for flight when the empty CG of
the plane falls into a certain range.
Clearly spoken, as long as you do not
overload the Coupe, you can not load it out of the proper CG range for
flight. The canvas bag is close enough to the CG that even loaded up to
the allowed maximum will not bring the CG out of range.
This is another safety feature of the
Coupe. The large baggage compartment zeros all these thoughts of course
and theoretically, ones you have it, you should calculate W&B before any
flight. And a flat hat shelf should have a similar effect. Of course you
could label it with a sign. No load here or so.
Bill Bayne responded:
With regard to luggage C.G., what you say is true for an Ercoupe with a wooden
prop. BUT, there aren't many around.
A McCauley metal prop places 11 additional lbs. at the farthest forward moment
(-32), which gives a measure of flexibility.
Those who choose to lug around a 35 amp battery add 5.3-8 lbs. at +55 (or so)
which cancels this out ;<)
Let's look at this loading subject a little more thoroughly.
The 415-C "canvas bag" does concentrate baggage at +57. The (calculated) C.G.
range of +26.4 to 30.3 remains the same for all models up to and including the
M10 Cadet. The M10 allows up to 90 lbs. in its "large" baggage compartment, and
the center of that load is still presumed located (by the pilot) at the same +57
arm. (no loose bowling balls in back ;<)
Ercoupe Models 415-C and CD dispense with the necessity to calculate C.G. when
the "Empty wt. C.G. is between 25.2" and 26.6" with 40 lbs. baggage, and between
25.2" and 25.8" with the maximum 65 lbs. baggage and gross wt. of 1260 lbs.
For the 415-D, "Empty wt. C.G. is between 26.2" and 27.2" with the maximum 65
lbs. baggage, gross wt. of 1400 lbs., and 9º "up" elevator. For the 415-E,
"Empty wt. C.G. is between 25.7" and 26.9" with the maximum 65 lbs. baggage,
gross wt. of 1400 lbs., and 20º "up" (split) elevator.
For the 415-G, "Empty wt. C.G. is between 25.9 and 26.7" with the maximum 75
lbs. on "Kiddy Seat", gross wt. of 1400 lbs., and 20º "up" (split) elevator.
Forney Models F-1 and F-1A retain the same "Empty wt. C.G." values as the 415-G.
Neither Alon nor Mooney lists a "Empty wt. C.G. range", probably because of the
greater loading options in their larger baggage compartments. At the forward
limit the plane is less responsive and slower. At the rearward limit the plane
is faster and more responsive, but still stable and safe. The various STCs
issued for large baggage compartments in Ercoupes are obviously the very sort of
"non-standard arrangements" that nullify "Empty wt. C.G." ranges for each model.
Exceed these limits enough and the plane can become uncontrollable, as perhaps
with two unsecured bowling balls in a "large" baggage compartment rotating
rapidly upon liftoff. So, even an Ercoupe can not be considered "foolproof" in
the hands of a genuinely determined fool.
I once calculated how much the C.G. varied from takeoff to landing at full gross
starting with full fuel and landing with 1/2 hr. reserve, two occupants who each
ate a sandwich with a soda, and burning a quart of oil. It's a real tribute to
Fred Weick how very little the Ercoupe's C.G. changes without any action
required on the part of pilot or passenger.