Allegheny Airlines Flight 853
|Date||September 9, 1969|
|Site||Moral Township, Shelby County, near Fairland, Indiana|
An Allegheny Airlines DC-9-30, c.1970
|Type||McDonnell Douglas DC-9-31|
|Flight origin||Boston Logan Airport|
|Destination||St. Louis International Airport|
Piper PA-28 similar to accident aircraft
Allegheny Airlines Flight 853, a McDonnell Douglas DC-9-31, collided in mid-air with a Piper PA-28 at approximately 3,550 feet on September 9, 1969, near Fairland, Indiana. The DC-9 carried 78 passengers and 4 crew members. The Piper was leased to a student pilot making a solo cross-country flight. The occupants of both aircraft were killed in the accident and the aircraft were destroyed by the collision and ground impact.
Allegheny 853 (N988VJ), a DC-9-30, was a regularly scheduled flight departing Boston, Massachusetts, for St. Louis, Missouri, with stops in Baltimore, Cincinnati and Indianapolis. The flight departed Cincinnati at 3:15pm en route to Indianapolis. Allegheny 853, flying under Instrument Flight Rules (IFR) clearance to Indianapolis, was instructed by Indianapolis Approach Control to descend to 2500 feet after passing the Shelbyville VOR at 6000 feet. The flight was then vectored to a 280 degree heading.
Meanwhile, the private Piper PA-28 (N7374J) was on a southeasterly heading. It was operating under a filed visual flight rules (VFR) flight plan which indicated a cruising altitude of 3500 feet. The PA-28 was not in communication with Air Traffic Control, and was not transponder equipped, and there was no evidence it appeared as a primary radar target on the radarscope.
Eight witnesses saw the aircraft collide. They reported broken to scattered cloud cover in the area, but both aircraft were below the clouds and could be seen clearly at the time of the collision. According to the witnesses, neither aircraft attempted a collision avoidance maneuver, however the captain in the DC-9 saw the Piper at least two seconds before the collision, as is evident from the cockpit voice recorder, as he is heard saying "I'm going down", and he started the sentence before the impact sound is heard. Wreckage analysis later concluded the PA-28's left forward side just forward of the left wing root clipped the DC-9's upper right vertical tail just below the horizontal stabilizer.
The PA-28 was struck by the DC-9 at a speed of roughly 350 mph (560 kph) and was sliced in half by the vertical stabilizer, which ripped straight through the cabin and killed the small plane's pilot instantly. Most of the PA-28 immediately plummeted to earth along with the airliner's vertical stabilizer, but the other third of it still had some momentum left and landed a few hundred feet further away. Meanwhile, the crippled DC-9 rolled over on its back and dove nose-first into a soybean field at speeds exceeding 400 mph (640 kph). Some witnesses claimed it was spinning as it went, but the NTSB investigators disputed these assertions. Flight 853 was shattered to pieces, the wreckage scattered over half a mile. The passengers and crew were dismembered by the forces of impact, with no intact bodies found (although the PA-28 pilot's body was intact) Despite all this, there was no fire or explosion because impact speeds were so great that the DC-9's fuel load dispersed quickly and did not ignite.
The Board determines the probable cause of this accident to be the deficiencies in the collision avoidance capability of the Air Traffic Control system of the Federal Aviation Administration in a terminal area wherein there was mixed instrument flight rules (IFR) and visual flight rules (VFR) traffic. The deficiencies included the inadequacy of the see-and-avoid concept under the circumstances of this case; the technical limitations of radar in detecting all aircraft; and the absence of Federal Aviation Regulations which would provide a system of adequate separation of mixed VFR and IFR traffic in terminal areas.
After this and similar mid-air collisions or near collisions, both the NTSB and FAA realized the inherent limitations of the "see and be seen" principle of air traffic separation in visual meteorological conditions, especially when aircraft of dissimilar speeds or cloud layers and other restrictions to visibility are involved. The following mitigating steps have since been taken:
- Transponders are now installed in most general aviation aircraft and all commercial/air-carrier aircraft, dramatically increasing radar visibility of lower and slower flying smaller aircraft, especially near atmospheric disturbances or other clutter (see Air Traffic Control Radar Beacon System and Secondary Surveillance Radar)
- Most airports with scheduled airline service now have a surrounding controlled airspace (ICAO designation Class B or Class C) for improved IFR/VFR traffic separation - all aircraft must be transponder equipped and in communication with ATC to operate within this controlled airspace
- Most commercial/air-carrier aircraft (and some general aviation) now have an airborne collision avoidance or TCAS device on board, that can detect and warn about nearby transponder-equipped traffic
- ATC radar systems now have "conflict alert" - automated ground based collision avoidance software that sounds an alarm when aircraft come within less than a minimum safe separation distance
- Accident description at the Aviation Safety Network
- From www.mcglaun.com site:
- Denied Appeal of Lawsuit Filed by Allegheny against United States of America et al. in 1974