However there are some planes like the Piper Seminole that was tested before the 23.149 came out.
The Seminole is a Part 23 airplane, and, according to the TCDS, was certified under the 1978 Part 23 regulations, which contained an earlier version of 23.149. I've attached a timeline of the changes to 23.149 below. Weight wasn't mentioned until 1978 and it's not clear whether the Seminole was operating under this definition or not, since it occurred the same year the Seminole was certified. The addition read:
The maximum sea level takeoff weight (or any lesser weight necessary to show <st1:stockticker>VMC</st1:stockticker>)
According to a conversation I had with a certification guy at the FAA's Small Airplane Directorate, the "maximum seal level takeoff weight" was essentially irrelevant, since "the lesser weight necessary to show Vmc" was normally the determining factor in establishing the weight at which the tests were done.
Plus, every
credible article and book I've read on the subject said that testing was done at light weight, even before the change in regulations. In fact, the change in regulations came about, according to the guy at the Small Airplane Directorate, to reflect how the testing was actually done.
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S<o></o>ec. 23.149
<o></o>Minimum control speed.
<o></o>(a) <st1:stockticker>VMC</st1:stockticker> is the minimum calibrated airspeed at which, when any engine is suddenly made inoperative, it is possible to recover control of the airplane with that engine still inoperative and maintain straight flight, either with zero yaw, or, at the option of the applicant, with an angle of bank of not more than five degrees. <st1:stockticker>VMC</st1:stockticker> may not exceed 1.2 with--
(1) Takeoff or maximum available power on each engine;
(2) The rearmost allowable center of gravity;
(3) The flaps in the takeoff position; and
(4) The landing gear retracted.
(b) At <st1:stockticker>VMC</st1:stockticker>, the rudder forces required to maintain control may not exceed the limitations set forth in Sec. 23.143, and it may not be necessary to throttle the remaining engines. During recovery, the airplane may not assume any dangerous attitude or require exceptional piloting skill, alertness, or strength, to prevent a heading change of more than 20 degrees.
<o></o>
1968
<o></o>Sec. 23.149 Minimum control speed.
(a) <st1:stockticker>VMC</st1:stockticker> is the minimum calibrated airspeed at which, when any engine is suddenly made inoperative, it is possible to recover control of the airplane with that engine still inoperative and maintain straight flight, either with zero yaw, or, at the option of the applicant, with an angle of bank of not more than 5°. <st1:stockticker>VMC</st1:stockticker> may not exceed 1.2 with--
(1) Takeoff or maximum available power on each engine;
(2) The rearmost allowable center of gravity;
(3) The flaps in the takeoff position;
(4) The landing gear retracted; and
[(5) The propeller of the inoperative engine--
(i) Windmilling, with the propeller speed or pitch control in the takeoff position; or
(ii) Feathered, if the airplane has an automatic feathering device.]
(b) At <st1:stockticker>VMC</st1:stockticker>, the rudder forces required to maintain control may not exceed the limitations set forth in Sec. 23.143, and it may not be necessary to throttle the remaining engines. During recovery, the airplane may not assume any dangerous attitude or require exceptional piloting skill, alertness, or strength, to prevent a heading change of more than 20°.
<o></o>
1978<o></o>
Sec. 23.149
Minimum control speed.
(a) <st1:stockticker>VMC</st1:stockticker> is the calibrated airspeed, at which, when the critical engine is suddenly made inoperative, it is possible to recover control of the airplane with that engine still inoperative, and maintain straight flight either with zero yaw or, at the option of the applicant, with an angle of bank of not more than five degrees. The method used to simulate critical engine failure must represent the most critical mode of powerplant failure with respect to controllability expected in service.
(b) For reciprocating engine-powered airplanes, <st1:stockticker>VMC</st1:stockticker> may not exceed 1.2 (where is determined at the maximum takeoff weight) with--
(1) Takeoff or maximum available power on the engines;
(2) The most unfavorable center of gravity;
(3) The airplane trimmed for takeoff;
(4) The maximum sea level takeoff weight (or any lesser weight necessary to show <st1:stockticker>VMC</st1:stockticker>);
(5) Flaps in the takeoff position;
(6) Landing gear retracted;
(7) Cowl flaps in the normal takeoff position;
(8) The propeller of the inoperative engine--
(i) Windmilling;
(ii) In the most probable position for the specific design of the propeller control; or
(iii) Feathered, if the airplane has an automatic feathering device: and
(9) The airplane airborne and the ground effect negligible.
<o></o>
1993
Minimum control speed.
<st1:stockticker>VMC</st1:stockticker> is the calibrated airspeed at which, when the critical engine is suddenly made inoperative, it is possible to maintain control of the airplane with that engine still inoperative and then maintain straight flight at the same speed with an angle of bank of not more than 5 degrees. The ability to maintain straight and level flight at <st1:stockticker>VMC</st1:stockticker> in a static condition with a bank angle of not more than 5 degrees must also be demonstrated. The method used to simulate critical engine failure must represent the most critical mode of powerplant failure, with respect to controllability expected in service.
(b) <st1:stockticker>VMC</st1:stockticker> may not exceed 1.2 , where is determined at the maximum takeoff weight, with--
(1) Maximum available takeoff power or thrust on the engines;
(2) The most unfavorable center of gravity;
(3) The airplane trimmed for takeoff;
(4) The maximum sea level takeoff weight, or any lesser weight necessary to show <st1:stockticker>VMC</st1:stockticker>;
(5) The airplane in the most critical takeoff configuration, with the propeller controls in the recommended takeoff position and the landing gear retracted; and
(6) The airplane airborne and the ground effect negligible.
(c) A minimum speed to intentionally render the critical engine inoperative must be established and designated as the safe, intentional, one-engine-inoperative speed, VSSE.]
(d) At <st1:stockticker>VMC</st1:stockticker>, the rudder pedal force required to maintain control may not exceed 150 pounds, and it may not be necessary to reduce power or thrust of the operative engines. During [the
maneuver,] the airplane may not assume any dangerous attitude and it must be possible to prevent a heading change of more than 20°.
<o></o>
1996
<o></o>Sec. 23.149
<o></o>Minimum control speed.
(a) <st1:stockticker>VMC</st1:stockticker> is the calibrated airspeed at which, when the critical engine is suddenly made inoperative, it is possible to maintain control of the airplane with that engine still inoperative, and thereafter maintain straight flight at the same speed with an angle of bank of not more than 5 degrees. The method used to simulate critical engine failure must represent the most critical mode of powerplant failure expected in service with respect to controllability.
(b) <st1:stockticker>VMC</st1:stockticker> for takeoff must not exceed 1.2 , where is determined at the maximum takeoff weight. <st1:stockticker>VMC</st1:stockticker> must be determined with the
most unfavorable weight and center of gravity position and with the airplane airborne and the ground effect negligible, for the takeoff configuration(s) with--
(1) Maximum available takeoff power initially on each engine;
(2) The airplane trimmed for takeoff;
(3) Flaps in the takeoff position(s);
(4) Landing gear retracted; and
(5) All propeller controls in the recommended takeoff position throughout.
<o></o><o></o> (e) At <st1:stockticker>VMC</st1:stockticker>, the rudder pedal force required to maintain control must not exceed 150 pounds and it must not be necessary to reduce power of the operative engine(s). During the maneuver, the airplane must not assume any dangerous attitude and it must be possible to prevent a heading change of more than 20°.