Now Comes Theodora

Piper Cub weight & balance calculation

If you should take your check flight in a Piper Cub, you may get thrown a curve IF the check pilot asks for a weight & balance calculation. Not many FBOs make this information available. But here's the table I worked out for N7006H, a 1946 J-3 rebuilt as an L-4 lookalike:

Max weight ..... 1,200.0 lb
Empty weight .... 766.5 lb w/ 4 quarts oil
Useful weight ... 453.5 lb (with a full tank of gas, that leaves 381.5 lb for the pilot, crew, and their gear)

Datum: leading edge of wing

Allowable c.g. range: 10.6" to 22.7"

Weight Arm Moment
Aircraft empty 766.5 16.52 12,659.25
Oil (included) 0.0 -29.00 0.00
Fuel: 12 gallons 72.0 -18.00 (1,296.00)
Front seat 9.00
Back seat 36.00
Baggage (max 20 lb) 49.00
1. Weight & balance sheet in 06H baggage compartment
2. 06H records at Dunn Aviation, Hampton NH

Some specs for J-3 Cubs with 3C-65 engine

I acquired the following sheet when I had to make that weight & balance calculation for Zero Six Hotel. I have tried to reproduce it as close to the original as possible.


Revision 32
October 1, 1997

The New Piper Aircraft, Inc.
2926 Piper Drive
Vero Beach, Florida 32960

IV. - Model J3C-65 (Army L-4, L-4A, L-4B (Navy NE-1), L-4H, L-4J (Navy NE-2)),2 POLM, Approved July 6,1939.

See NOTE 7 regarding conversion to 2 PCLM.

Army L-4 (previously Army 0-59) is the same as Model J3C-65. Army L-4A (previously Army 0-59A) and Army L-4B are the same as Model J3C-65 except for transparent turtledeck enclosure, revised rear seat with seat back belts, addition of rear shelf and rear floorboard. Army L-4H is same as L-4A except for G.F. radio equipment and revised method of installing the transparent cockpit enclosure. Army L-4J (Navy NE-2) same as any L-4, L-4A, L-4B and L-4H except for installation of propeller, Item 1.

Continental A-65-1 (See Item 311C for optional engines)

73 minimum octane aviation gasoline

Engine Limits
For all operations, 2350 r.p.m. (65 hp)

Airspeed Limits (CAS)

Level flight or climb ... 90 mph ( 78 knots)

Glide or dive ... 122 mph (106 knots)

Propeller Limits
Static r.p.m. at maximum permissible throttle setting (No additional tolerance permitted):
(a) With A-65-1 engine: Not over 2300, not under 2000.
(b) With optional engines (Item 311C) and propeller Item 2 or 101:
Not over 2300, not under 1950.
Diameter: Not over 81 inches, not under 69.7 inches (with fixed pitch wood propeller).
Not over 74 inches, not under 72 inches (with propeller Item 2).

C.G. Range
(+10.6) to (+22.7)
See NOTE 3 for restricted limits on certain Serial Nos. below 4502.

Empty Weight C.G. Range
If placard "Solo flying in rear seat only" is installed (See NOTE 2):
(+8.5) to (+20.3)
When empty weight C.G. falls within range given, computafion of critical fore and aft C.G. positions is unnecessary. Range is not valid for non-standard arrangements.

Maximum Weight
Serial Nos. 7842, 7845 through 7883, and 7912 and up are eligible for 1170 lb. These airplanes are also eligible for 1220 lb. maximum weight provided the landing gear is revised in accordance with Piper Dwgs. 31472 and 31423.
Serial Nos. prior to 7912, and not listed above, are eligible for 1100 lb. maximum weight. These airplanes are also eligible for 1170 lb. maximum weight provided the lift struts and attachments are revised in accordance with Piper Dwgs. No. 12352, 13233 and 21642 and for further increase to 1220 lb, upon revision of the landing gear in accordance with Piper Dwgs. No. 31472 and 31423.
Serial Nos. 10339 and up and 2356-A and up of Model J3C-65 eligible for 1220 lb. maximum weight.

Number of Seats
2 (one at +9 and one at +36)

Maximum Baggage
20 lb. (+49)

Fuel Capacity
12 gallons (-18)

Oil Capacity
1 gallon (-29)

Control Surface Movements

Elevator34° Up 29° Down
Rudder 30° Left 30° Right
Aileron 18° up 18° Down
Stabilizer 2.5° Up 4° Down

Serial Numbers Eligible
2325, 2327, 2339, 2340, 2342, 2344, 2345, 2347, 2349, 2351, 2355 and up; 2356-A and up; and 8277-1 through 8277-40.

Required Equipment
In addition to the pertinent required basic equipment specified in CAR 4a, the following items of equipment must be installed:
Items 101. 102, 103 and 104(a).

Specifications Pertinent to All Models

Question? Comment? Newsletter? Send me an email. Blue skies! -- Dan Ford

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