Mid-Air Collision: A Comparative Study

This is a comparative study of mid-air collision involving helicopter - aeroplane and the analysis of causal factors contributing to the accidents.

A mid-air collision, according to Wikipedia, is an aviation accident in which two or more aircraft come into contact during flight. Although, the odds are fantastically slim that two aircrafts could collide in a large and virtually empty three dimensional space, the potential for a mid-air collision is increased by miscommunication, error in navigation, and deviations from flight plans.[1]


2009 Hudson River Mid-Air Collision

Date : 8 August 2009
Location : Hudson River, Hoboken, New Jersey
Aircraft Type : Eurocopter AS350 N401LH and Piper PA32 N71MC

The Piper Cherokee Lance took off from Teterboro, New Jersey and was heading for Ocean City, New Jersey when it collided at approximately 1,100 feet (340 m) MSL altitude with the helicopter on a sightseeing trip from the West 30th Street heliport.

Shortly after taking off, the plane was instructed to contact Newark Liberty International Airport, and the pilot acknowledged the instruction. However, he did not contact the tower at Newark. Soon after, a controller at Newark who was concerned about aircraft in the plane's path contacted the Teterboro controller and asked the Teterboro controller to attempt to re-establish contact. Attempts to contact the plane and change its heading were unsuccessful.

While heading south down river, the plane was seen to be behind the sightseeing helicopter, which was going about half as fast. The pilot of another helicopter (refueling at the heliport) saw the impending accident and attempted to warn both the airborne helicopter and the plane by radio but received no response. At 11:53 am, the Piper's right wing crashed into the Eurocopter, severing the right wing of the airplane and multiple rotor blades from the helicopter.[2]

(Image embedded from Wordpress on 18 Sep 2009)

1993 Auckland Mid-Air Collision

Date : 26 Nov 1993
Location : Auckland, New Zealand
Aircraft Type : Aerospatiale AS355 ZK-HIT and Piper PA28 ZK-ENX

An Aerospatiale TwinStar (ZK-HIT), performing ad-hoc missions around the city of Auckland for the New Zealand Police, collided with a Piper Archer (ZK-ENX), conducting a regular weekly traffic patrol. Discussions with other pilots of the aircraft and police crew found they were familiar with the normal operating altitudes of 1,000 feet for the Police Eagle (Aerospatiale helicopter) and 1,500 feet AMSL for the Police Traffic Patrol (Piper aircraft).

The helicopter was operating out of Mechanics Bay heliport and was climbing to a southwest heading before making a 30 degree turn to the left, continuing to climb through 1,200 feet until the accident 18 seconds later. Meanwhile, the aeroplane left Ardmore Aerodrome flying southeast reporting several traffic accidents and was turning to a southwest heading when the collision occurred.[3]

(Image embedded from Wordpress on 18 Sep 2009)

Comparative Analysis of Causal Factors

2009 Hudson River Mid-Air Collision
Weather was sunny, visual meteorological conditions prevailed
Both aircraft operate under visual flight rules in an area known as “Hudson River VFR Corridor”
Collision occurred at approximately 1,100 feet ……………………………………………….
Authorities said the Piper's "low wing" design made it difficult to see below the aircraft and the helicopter's rotors make it difficult to see above
Because of the accident airplane's intended flight path, the NTSB believes that the pilot may have wanted to climb out of the uncontrolled VFR corridor into the controlled Class B airspace above. However, for reasons unknown as yet, he was not in communication with any air traffic controllers after he switched frequencies from Teterboro tower. He also apparently was not communicating on the Corridor's self-announce frequency
1993 Auckland Mid-Air Collision
Accident occurred in daylight with excellent visibility
Both aircraft flying under visual flight rules in an uncontrolled airspace (Class G)
Collision occurred at an altitude of about 1,400 feet
Transport Accident Investigation Commission cited the inherent limitations with the "see and avoid" method as a causal factor
Contributing factors were the helicopter not leveling at the agreed altitude, the helicopter did not establish mutual position by radio, and the helicopter crewmembers did not see the traffic in time


In the latest development on the Hudson River mid-air collision, an NTSB official told a congressional committee that shortly after the single-engine Piper took off from Teterboro Airport in New Jersey, a Teterboro controller handed off the plane to nearby Newark Liberty International. During the handoff, the controller instructed the Piper pilot to contact Newark and gave him the radio frequency.

However, air traffic control recordings show the frequency the pilot read back was incorrect. There is no indication that any controller heard the incorrect readback or attempted to correct it. Less than a minute after the incorrect readback, the plane collided with the air tour helicopter, sending both aircraft hurtling into the river.

The Federal Aviation Administration has placed the Teterboro controller on administrative leave pending an investigation. The controller made a personal phone call after clearing the private plane for takeoff. His supervisor was also suspended for not being at the control center in Teterboro, New Jersey, as required. The FAA said that while they have "no reason to believe the actions of both men contributed to the accident, this kind of conduct is inappropriate and unacceptable." [4]

(Video embedded from YouTube on 18 Sep 2009)
1. Mid-Air Collision Retrieved on 18 Sep 2009 from Wikipedia
2. 2009 Hudson River Mid-Air Collision Retrieved on 18 Sep 2009 from Wikipedia
3. 1993 Auckland Mid-Air Collision Retrieved on 18 Sep 2009 from Wikipedia

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