I'm not being argumentative, I'm trying to study up. Could you please cite the FAR that requires this in the case removing a removable seat?
I didn't take it that you were. The rules are confusing for a&p's too.
There is no specific far requiring it. You are required to operate the aircraft within limitations of the type certificate. You cannot comply with that without knowing the true and current weight an cg. Here is a good post from another forum discussing it.
There is no blanket requirement in the regs that this information be carried aboard the airplane. However, under the section "AIRPLANE FLIGHT MANUAL AND APPROVED MANUAL MATERIAL"
§ 23.1589 Loading information.
The following loading information must be furnished:
(a) The
weight and location of each item of equipment that can be easily removed, relocated, or replaced and that is installed when the airplane was weighed under the requirement of § 23.25.
(b) Appropriate loading instructions for each possible loading condition between the maximum and minimum weights established under § 23.25, to facilitate the center of gravity remaining within the limits established under
§ 23.23.
Combine the above with 14 CFR 21.5, which says
21.5 Airplane or Rotorcraft Flight Manual.
(a) With each airplane or rotorcraft that was not type certificated with an
Airplane or Rotorcraft Flight Manual and that has had no flight time prior to
March 1, 1979, the holder of a Type Certificate (including a Supplemental
Type Certificate) or the licensee of a Type Certificate
shall make available to the owner at the time of delivery of the aircraft a current approved Airplane or Rotorcraft Flight Manual.
and combine that with 14 CFR 91.1 which says
§ 91.9 Civil aircraft flight manual, marking, and placard requirements.
(a) Except as provided in paragraph (d) of this section, no person may operate a civil aircraft without complying with the operating limitations specified in the approved Airplane or Rotorcraft Flight Manual, markings, and placards, or as otherwise prescribed by the certificating authority of the country of registry.
(b) No person may operate a U.S.-registered civil aircraft—
(1) For which an Airplane or Rotorcraft Flight Manual is required by § 21.5
of this chapter
unless there is available in the aircraft a current, approved Airplane or Rotorcraft Flight Manual or the manual provided for in § 21.141(b);
All of the above applies to aircraft with no flight time prior to March 1, 1979. Prior to that, some aircraft had as part of their type certificate that current weight and balance information be carried aboard the aircraft, or had a requirement for an AFM.
Bob