One of the methods used to train astronauts for the effects of "zero gravity" in space is to put them in a specially equipped plane which has been stripped of seats and fitted with padded walls. The pilot then takes the plane up to an altitude of typically 8600 meters and, at a speed of 870 km/hr, puts it into a sudden steep climb. He then pilots the plane so that it follows the parabolic trajectory of free fall until it is falling at the maximum allowable rate for safety. He can do this by flying the plane so that he is in continuous free fall himself. (He is trained to do this.)

Question

One of the methods used to train astronauts for the effects of "zero gravity" in space is to put them in a specially equipped plane which has been stripped of seats and fitted with padded walls. The pilot then takes the plane up to an altitude of typically 8600 meters and, at a speed of 870 km/hr, puts it into a sudden steep climb. He then pilots the plane so that it follows the parabolic trajectory of free fall until it is falling at the maximum allowable rate for safety. He can do this by flying the plane so that he is in continuous free fall himself. (He is trained to do this.)
If the maximum angle of elevation that can be achieved in his initial rise is 21.5 degrees (with respect to the horizontal) and likewise the maximum angle of descent for safety is 21.5 degrees, how long (in seconds) will the astronaut trainees experience zero gravity?