HISTORY OF FLIGHTOn April 3, 2014 about 1230 eastern daylight time (EDT), an experimental amateur-built Vans RV-12, N409FM, and a DeHavilland DHC-1"Chipmunk,"N12BH collided over the runway at the Bayport Aerodrome (23N), Bayport, New York. The Chipmunk received substantial damage and the RV-12 received minor damage. The private pilot in the RV-12 and the airline transport pilot in the Chipmunk were not injured. Visual meteorological conditions prevailed and no flight plans were filed for either flight. The RV-12 departed the Cherry Ridge Airport (N30) in Honesdale, Pennsylvania. The Chipmunk was departing Bayport Aerodrome for Long Island MacArthur Airport (ISP) in Islip, New York. Both airplanes were being operated as personal flights in accordance with Title 14 Code of Federal Regulations Part 91. According to the pilot of the RV-12, he stated that he made a radio call at the "mid bay" position announcing his intentions to land at 23N. The pilot also stated that he made subsequent radio calls while crossing the shoreline, when on 45-degree left base leg for runway 36, and on the turn onto the final. During the approach, the pilot of the RV-12 stated that he did not see any traffic on the runway. When the pilot of the RV-12 began his flare for landing, he stated that the "forward half of a departing aircraft came into view." One of the propeller blades of the RV-12 then struck the upper aft portion of the vertical stabilizer and rudder of the Chipmunk. The RV-12 then landed without power, while the Chipmunk departed to the north and continued to ISP. A portion of the propeller blade tip from the RV-12 and a lead rudder balance weight from the Chipmunk, were later discovered on the west half of runway. According to the pilot of the Chipmunk, after taxing to the south end of runway 36 he did an engine run-up and transmitted his intentions to depart on runway 36 on the traffic advisory frequency. The pilot said that he did not see anyone in the traffic pattern or hear them on the radio when he conducted a 360-degree turn to look for traffic prior to departing on the runway. At rotation the pilot of the Chipmunk stated that he "thought something in the tail or in the back had broken or let go or even possibly was hit by a bird." The pilot of the Chipmunk also stated that he thought his airplane was "controllable and flyable" and so he continued to ISP for landing on runway 33L. PERSONNEL INFORMATIONThe pilot of the RV-12 held a Federal Aviation Administration (FAA) private pilot certificate with a rating for airplane single-engine land. He reported on that he had accrued approximately 740 total flight hours. The pilot of the Chipmunk held a Federal Aviation Administration (FAA) airline transport pilot certificate with a rating for airplane single-engine land, multi-engine land. He also held a flight instructor certificate for airplane single-engine land, multi-engine land, and instrument airplane. His most recent FAA first-class medical certificate was issued on April 4, 2014. He reported on that date that he had accrued approximately 36,000 total flight hours. AIRCRAFT INFORMATIONAccording to FAA and airplane maintenance records, the RV-12 was issued its special airworthiness certificate in 2010. The airplane's most recent conditional inspection was completed on October 1, 2013. At the time of accident, the airplane had accrued approximately 338 total hours of operation. According to FAA and airplane maintenance records, the Chipmunk was manufactured in 1956. The airplane's most recent annual inspection was completed on March 11, 2014. At the time of accident, the airplane had accrued approximately 2,500 total hours of operation. METEOROLOGICAL INFORMATIONRecorded weather obtained from ISP's automated weather observation system located approximately 3 miles northwest of the accident site revealed that visual flight rules weather existed around the time of the accident. At 1156 the reported weather included: wind 320 degrees at 9 knots, visibility 10 statute miles, scattered clouds at 25,000 feet, temperature 14 C, dewpoint -4 C, altimeter 30.09 inches of mercury. AIRPORT INFORMATIONAccording to FAA and airplane maintenance records, the RV-12 was issued its special airworthiness certificate in 2010. The airplane's most recent conditional inspection was completed on October 1, 2013. At the time of accident, the airplane had accrued approximately 338 total hours of operation. According to FAA and airplane maintenance records, the Chipmunk was manufactured in 1956. The airplane's most recent annual inspection was completed on March 11, 2014. At the time of accident, the airplane had accrued approximately 2,500 total hours of operation. ADDITIONAL INFORMATIONAs a result of this accident, in order to improve safety, the New York Department of Transportation added the following comments to the Airport/Facility Directory: "PILOTS BE ADVISED: DUE TO PATTERN PROCEDURES, AIRCRAFT IN THE RUN-UP AREA OR STARTING TAKEOFF ROLL ON RWY 36, AND AIRCRAFT ON FINAL APPROACH TO RWY 36, MAY NOT BE ABLE TO SEE EACH OTHER DUE TO TREES." TESTS AND RESEARCHA review of satellite imagery and aerial photos of the airport indicated that portions of the approach end of runway 36 would be blocked from view due to trees, when using the published traffic pattern entry for runway 36. It was also noted that aircraft entering the traffic pattern for runway 36 would not be visible by aircraft on the ground holding short at the approach end of runway 36.