Originally Posted by FAR 23
23.25 Weight limits.
(a) Maximum weight. The maximum weight is the highest weight at
which compliance with each applicable requirement of this part (other
than those complied with at the design landing weight) is shown. The
maximum weight must be established so that it is--
(1) Not more than the least of--
(i) The highest weight selected by the applicant; or
(ii) The design maximum weight, which is the highest weight at which
compliance with each applicable structural loading condition of this
part (other than those complied with at the design landing weight) is
shown; or
(iii) The highest weight at which compliance with each applicable
flight requirement is shown, and
(2) Not less than the weight with--
(i) Each seat occupied, assuming a weight of 170 pounds for each
occupant for normal and commuter category airplanes, and 190 pounds for
utility and acrobatic category airplanes, except that seats other than
pilot seats may be placarded for a lesser weight; and
(A) Oil at full capacity, and
(B) At least enough fuel for maximum continuous power operation of
at least 30 minutes for day-VFR approved airplanes and at least 45
minutes for night-VFR and IFR approved airplanes; or
(ii) The required minimum crew, and fuel and oil to full tank
capacity.
(b) Minimum weight. The minimum weight (the lowest weight at which
compliance with each applicable requirement of this part is shown) must
be established so that it is not more than the sum of--
(1) The empty weight determined under Sec. 23.29;
(2) The weight of the required minimum crew (assuming a weight of
170 pounds for each crewmember); and
(3) The weight of--
(i) For turbojet powered airplanes, 5 percent of the total fuel
capacity of that particular fuel tank arrangement under investigation,
and
(ii) For other airplanes, the fuel necessary for one-half hour of
operation at maximum continuous power.
And later:
23.562 Emergency landing dynamic conditions.
(a) Each seat/restraint system for use in a normal, utility, or
acrobatic category airplane must be designed to protect each occupant
during an emergency landing when--
(1) Proper use is made of seats, safety belts, and shoulder
harnesses provided for in the design; and
(2) The occupant is exposed to the loads resulting from the
conditions prescribed in this section.
(b) Except for those seat/restraint systems that are required to
meet paragraph (d) of this section, each seat/restraint system for crew
or passenger occupancy in a normal, utility, or acrobatic category
airplane, must successfully complete dynamic tests or be demonstrated by
rational analysis supported by dynamic tests, in accordance with each of
the following conditions. These tests must be conducted with an occupant
simulated by an anthropomorphic test dummy (ATD) defined by 49 CFR Part
572, Subpart B, or an FAA-approved equivalent, with a nominal weight of
170 pounds and seated in the normal upright position.
170lb = 77kg
190lb = 86kg.
The wording in CS.23, which is the equivalent European document, is for all reasonable purposes identical.
So there you have it, anybody weighing more than 77kg (12 stone 2lb)
clothed is heavier than most light aircraft were designed for. (Me included!).
By comparison, microlights use a minimum of 86kg and a bit of "one-upmanship" in the microlight community means that most are designed for 100kg+, whilst gliders use 110kg for a single-seater, or 180kg (again, or more) for a 2-seater, although to be fair that includes their parachute.
G