Midair Over The Hudson

The NTSB points out that the FAA Advisory Circular "Pilots' Role in Collision Avoidance" is badly in need of updating because a lot of things have changed since it was put out in March 1983. The Advisory Circular includes guidance on operating within terminal radar service areas, terminal control areas and airport traffic areas, which became obsolete with the 1994 reclassification of North American airspace. It says nothing about air tour operational areas, and nothing about technological advances that may aid in traffic awareness, such as portable or panel-mounted traffic-alerting equipment designed for general aviation aircraft.

Both the Piper and the Eurocopter had Mode S transponders and equipment to receive signals sent out by the FAA's Traffic Information Service (TIS). During each radar scan, which occurs about every five seconds, TIS sends the estimated position, relative altitude, altitude trend and ground track information for a maximum of eight intruder aircraft located within seven nm horizontally and up to 3,500 feet above and 3,000 feet below.

TIS also provides an aural and a visual alert when an intruder is projected to come within ½ nm and 500 feet vertically within the next 34 seconds. Receivers create visual displays of traffic for the pilots, and can issue visual and aural conflict alerts.

The NTSB found that the FAA's TIS system sent the Piper traffic alerts concerning the helicopter beginning 32 seconds before the collision, and sent the helicopter traffic alerts concerning the airplane beginning 37 seconds before the collision.

The NTSB couldn't determine whether the pilots were seeing the traffic displays their equipment could generate or were aware of visual and aural alerts, which intruding aircraft would activate. A video recorded by a ferry boat passenger showed that the Piper appeared to roll to the right just before the collision, as if the pilot was attempting an evasive maneuver.

The Piper had taken off from Wings Field Airport, Philadelphia, Penn., stopped at Teterboro Airport (TEB), N.J., to pick up a passenger, and was destined for Ocean City Municipal Airport, Ocean City, N.J. The helicopter's local sightseeing flight originated at the West 30th Street Heliport in Manhattan.

The Piper pilot radioed the clearance delivery controller at the Teterboro tower and requested departure clearance with a cruise altitude of 3,500 feet and flight-following services. The pilot then contacted the local controller, advising he was ready to taxi.

While the airplane was taxiing, the local controller asked the pilot whether he was "gonna be requesting!VFR down the river to Ocean City or just!southwest bound." The pilot replied that he'd take whichever route was the most direct. The local controller radioed, "Okay just!let me know so I know who [to] coordinate [the] handoff with," to which the pilot responded, "I'll take down the river, [that would] be fine."

A routing over the Hudson River with a climb to 3,500 feet would have required clearance into Class B airspace. The pilot would have to get the clearance from a controller at Newark Liberty International Airport (EWR) after the Teterboro controller executed a handoff.

At the time of the accident, there was a VFR exclusion area in the Class B airspace that allowed uncontrolled VFR flight above the Hudson River up to and including 1,100 feet MSL. The Class B airspace overlying TEB begins at an altitude of 1,800 feet.

At 11:48 a.m., the pilot radioed the TEB tower that he was ready for takeoff. The pilot was told to make a left turn to the southeast (to avoid entering EWR airspace and the final approach course for EWR runway 22) and maintain 1,100 feet or below.

At 11:50:02, the TEB local controller identified the airplane on radar, and executed an electronic radar handoff of the airplane to the EWR Class B airspace controller. The controller didn't transfer radio communications.

An electronic radar handoff transfers a radar data block from one controller to another. A controller initiates this process by "flashing" the radar data block to the receiving controller. When the new controller accepts the handoff, the radar data block no longer flashes and is modified so that both controllers know that the handoff is complete. Only after this is done is the pilot told to change to the new controller's frequency.

At 11:50:32, the TEB controller telephoned a female in Teterboro Airport operations and began a conversation that was unrelated to his work. He also had been on the phone with her earlier. While on the phone, at 11:51:17, the controller told the Piper pilot to start a left turn to join the Hudson River, which the pilot acknowledged. At that time, the Piper had leveled off at 1,100 feet according to radar data.

At 11:52:19, the controller told the pilot to contact the Newark controller on a frequency of 127.85. The pilot responded, but said, "One two seven point eight," an incorrect frequency. This transmission was the last communication between the pilot and ATC. The NTSB concluded that the TEB local controller didn't correct the airplane pilot's readback of the wrong frequency because he was busy on the phone and handling other transmissions. Because the airplane pilot had likely entered an incorrect frequency into his radio, he wouldn't have been able to receive traffic advisories until he returned to the TEB controller or established contact on the correct EWR frequency.

The EWR controller called the TEB controller, asking him to transfer communications for the flight and put the airplane on a heading of 220, to keep it away from other traffic over the Hudson River while remaining clear of the final approach course for runway 22 at EWR. At 11:52:28, while still on the phone with the female in airport operations, the TEB controller asked the EWR controller to repeat the instruction, which he did. Then, the TEB controller twice tried to radio the Piper pilot, but received no response.

The TEB controller's telephone conversation with airport operations ended at 11:53:10. About seven seconds later, the TEB controller asked the EWR controller about the status of the Piper and was told that the pilot had not made contact. It's speculation, but had the pilot contacted EWR, he might have been cleared to climb into the Class B airspace, been given a slightly different heading, or been warned about conflicting traffic.

At 11:52:00, the helicopter had taken off for its planned 12-minute tour. The helicopter appeared on ATC radar at 11:52:28, near the midpoint of the river and climbing through 400 feet. Radar data showed that the helicopter flew to the west side of the river, turned to the south to follow the river, and continued to climb to an altitude of 1,100 feet.

A Liberty Helicopters pilot who was waiting to depart told investigators that the accident helicopter pilot made a position report on the Common Traffic Advisory Frequency (CTAF) used in the VFR exclusion area. The pilot on the ground saw the airplane approaching the helicopter from behind and to the right.

The pilot couldn't transmit a traffic advisory to the accident helicopter pilot on the CTAF until after the accident helicopter pilot completed his position report. The accident helicopter pilot didn't respond to the advisory.

Radar data showed that the collision happened at 11:53:14. The aircraft were at an altitude of 1,100 feet. Both aircraft fell into the Hudson River. Between 11:52:33 and 11:53:24, conflict alerts for the accident airplane and an aircraft squawking 1200 (which the helicopter was using) were generated 11 times to the TEB local controller and the EWR Class B airspace controller. Neither controller recalled seeing or hearing a conflict alert on his radar display during that time.

The Piper pilot, age 60, held a private pilot certificate and was instrument rated. He had logged 1,121 hours, with 834 hours in the Piper PA-32. The helicopter pilot, age 32, held a commercial pilot certificate for rotorcraft/helicopter. He had 2,741 hours, with 781 hours in the AS350.

Sun glare wasn't likely a factor for the Piper pilot. Its angle above the horizon would have placed it near the top of the airplane's windscreen. Any glare caused by the sun's reflection off the river would have been blocked by the airplane's structure. For the helicopter pilot, the sun's position would have been to his left and not in the direction from which the airplane could have been visible.

The Safety Board found that the helicopter would have remained a relatively small and stationary object in the airplane's windscreen until about five seconds before the collision. The helicopter would have appeared below the horizon and against a complex background of buildings until the last second. The helicopter pilot would not have been able to see the airplane because it was above and behind the helicopter.

Exactly just what each pilot was doing in the seconds before the collision couldn't be determined. The airplane pilot may have been focusing on establishing communications with EWR, and the helicopter pilot may have been providing narration for the sightseeing tour. However, under the see-and-avoid concept, both pilots were responsible for avoiding a collision regardless of their workload.

The NTSB determined that the probable cause of this accident was 1) the inherent limitations of the see-and-avoid concept, which made it difficult for the airplane pilot to see the helicopter until the final seconds before the collision, and 2) the Teterboro Airport local controller's nonpertinent telephone conversation, which distracted him from his duties, including correcting the airplane pilot's read-back of the Newark frequency and the timely transfer of communications for the accident airplane to the EWR tower.

Contributing to this accident were 1) both pilots' ineffective use of available electronic traffic information to maintain awareness of nearby aircraft, 2) inadequate FAA procedures for transfer of communications among ATC facilities near the Hudson River Class B exclusion area; and (3) FAA regulations that didn't provide adequate vertical separation for aircraft operating in the Hudson River Class B exclusion area.

Peter Katz is editor and publisher of NTSB Reporter, an independent monthly update on aircraft accident investigations and other news concerning the National Transportation Safety Board. To subscribe, write to: NTSB Reporter, Subscription Dept., P.O. Box 831, White Plains, NY 10602-0831.