A resposta para as duas perguntas é "sim". A FAA ordenou, com efeito, a instalação do "Cooper Vanes" e o fez no 1972.
O motivo pelo qual você não conseguiu encontrar a resposta pode ter sido o fato de as modificações não terem sido chamadas de "Cooper Vanes" pela FAA e nem a FAA estava visando o 727 especificamente. Em vez disso, abordaram saídas ventrais e de cauda em qualquer aeronave.
CFR 14, Parte 25 (Normas de aeronavegabilidade: Aviões da categoria Transporte), Subparte D (Projeto e construção, Disposições de emergência) contém, desde o 31st de dezembro de 1972, o seguinte texto (grifo meu):
Sec. 25.809
Emergency exit arrangement.
...
(j) When required by the operating rules for any large passenger-carrying turbojet powered airplane, each ventral exit and tailcone exit must be--
(1) Designed and constructed so that it cannot be opened during flight; and
(2) Marked with a placard readable from a distance of 30 inches and installed at a conspicuous location near the means of opening the exit, stating that the exit has been designed and constructed so that it cannot be opened during flight
Esta regra foi anunciada no Aviso de Proposta de Regulamentação. Número da Nota 72-15, Publicado em junho 6th, 1972.
Refere claramente os seqüestros como o motivo dessa alteração.
....
In spite of concerted efforts made by the FAA and the air carriers,
incidents continue to occur wherein the safety of the flight of
aircraft engaged in passenger-carrying operations under Part 121 of
the Federal Aviation Regulations has been jeopardized by persons
intending to harm the crew or take command of the airplane. On a
number of occasions in recent hijackings, the ventral exit of an
airplane has been opened and a hijacker aboard has parachuted from the
airplane through that exit. The agency recognizes that every possible
step must be taken to deter persons from boarding aircraft for such a
hijacking purpose. Accordingly, the FAA deems it appropriate to
propose certain amendments to Parts 25 and 121.
Specifically, it is proposed to amend Sec 25.809 to provide that, when
required by the operating rules, for any large passenger carrying
turbojet powered air-plane an approved means must be provided so that:
(1) takeoff cannot be started if either the ventral exit or tail cone
exit is not locked; and
(2) neither the ventral exit nor the tail cone
exit can be opened in flight.
A similar amendment is proposed to be made to Sec 121.310, to become
effective with respect to persons conducting operations under Part 121
six months following its adoption.
However, it is to be noted that to achieve compliance with the
proposed regulation both the ventral exit and tail cone exit would
have to continue to meet all of the requirements applicable to their
approval as emergency exits. Specifically, to achieve compliance, the
conditions that would have to be met to obtain approval of
modification to the locking mechanisms of these two exits are as
follows:
(1) The mechanism must be locked while the airplane is
aloft;
(2) Takeoff of the airplane cannot be started if either ventral
or tail cone is not locked; and
(3) The exit must be available for use
in the event of an emergency.
Como a Parte 25 é para certificação de aeronavegabilidade de novas aeronaves, foi proposta uma alteração adicional à Parte 121, de modo que o operador de aeronave existente recebesse meses do 6 para aplicar as novas regras a aeronaves já certificadas.
De alguma forma, a alteração no Sec 121.310 não pode ser encontrada no diretório Biblioteca de Regulamentação e Orientação da FAA (pelo menos não datado do 1972), mesmo que o regra final de 30 em novembro, o 1972 o inclui.
A revisão do 121.310 a partir do 1997 inclui o texto
Agradecimentos especiais à FAA por tornar os arquivos de regulamentação da era pré-Internet facilmente acessíveis através da Internet.