19990807041891A

(.4)A pair of float equipped, twin engine airplanes were each parked parallel to a dock. The airplanes were separated by about eight feet, one in front of the other. Both airplanes, operated by the same company, were preparing to depart on sightseeing flights. The crew of first airplane, N288SA, was beginning a passenger briefing. The passengers were on board the airplane, but the engines had not been started. The crew of the second airplane, N224SA, had completed a briefing to their passengers, and had started the engines. N224SA was tethered to the dock by ropes attached to the floats at the forward and aft end of the airplane. Each rope was tended by a company dock handler. Due to a slight change in the manner the passengers arrived from a cruise ship, the passengers had not received a briefing booklet before boarding the airplane. A company representative approached the forward dock handler to hand the briefing booklets to the airplane crew. The aft dock handler observed this activity and mistook its meaning as a 'thumbs up' signal. He released the docking rope, allowing N224SA to begin moving forward under idle power. The nose of N224SA collided with the tail of N28 8SA. N288SA received damage to the rudder and trom tab assembly. N224SA received minor damage to the left pilot tube, and the left side of the nose.(-23) with engines running, dock personnel untied the aircraft without receiving release signal from the captain. N224 moved forward colliding with N288. N224 received minor damage to radome and pitot tube.