1955 MacArthur Airport United Air Lines crash

Coordinates: 40°47′43″N 073°06′01″W / 40.79528°N 73.10028°W / 40.79528; -73.10028
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1955 MacArthur Airport United Air Lines crash
A photograph of an aircraft with four propellers in the air
A United Airlines Douglas DC-6, similar to Mainliner Idaho, the aircraft involved
in the accident
Accident
DateApril 4, 1955
Islip, New York, United States[2]
DestinationLaGuardia Airport, New York City, New York, United States[2]
Crew3[4]
Fatalities3[4]
Survivors0

On April 4, 1955, a United Airlines Douglas DC-6 named Mainliner Idaho crashed shortly after taking off from Long Island MacArthur Airport, in Ronkonkoma, Islip, New York, United States.

The flight was operated for the purpose of maintaining the currency of the instrument rating of two of the airline's pilots. Shortly after takeoff and only seconds after climbing through 150 feet (46 m), the plane began banking to the right. It continued to roll through 90 degrees; the nose then dropped suddenly and moments later it struck the ground. All three members of the flight crew were killed upon impact.

An investigation found a simulated

engine No. 4 prior to taking off. Investigators found that if the throttle lever was pulled back too far, it would cause the propeller to reverse—a feature designed to slow the aircraft upon landing. Once the landing gear was raised, the crew would have to raise a metal flag in the cockpit to bring the propeller blades back into the correct position, since a safety device prevented electric power from operating the rotating mechanism at the roots of the blades unless the aircraft was on the ground or the flag was manually raised. The Civil Aeronautics Board
(CAB) concluded one of the flight crew applied full power to No. 4 engine, thinking this would bring the aircraft out of the increasing bank. Because the blades were reversed and the flag was not raised, that increased the reverse thrust from No. 4 engine, causing the DC-6 to spiral out of control. Since the plane was so close to the ground, the suddenness of the bank and dive meant the flight crew had no chance to recover the aircraft before impact.

In the aftermath of the accident, the

Civil Aeronautics Administration (CAA) issued an Airworthiness Directive
ordering all DC-6 and DC-6B aircraft to be fitted with a manual device which could prevent the inadvertent reversal of the propeller blades. United Airlines also stated they had begun installing reverse thrust indicator lights in the cockpits of their DC-6 aircraft, which would warn pilots when a propeller had reversed.

History

On April 4, 1955, a United Airlines check captain, Stanley C. Hoyt, age 45, was carrying out

Pratt & Whitney R2800-CB16 engines, fitted with Hamilton Standard 43E60-317 propellers.[5]

The weather on the day of the accident was clear, although there was a strong wind of about 20 knots (37 km/h) hitting the airfield from the southwest, with occasional gusts of wind as fast as 30 knots (56 km/h).[3] The aircraft made several circuits, taking off and landing again, before eyewitnesses observed the aircraft standing at the end of the runway and then taking off at about 15:50 Eastern Standard Time.[3][4] The takeoff weight was around 61,000 pounds (28,000 kg), far below the aircraft's maximum permissible weight and the center of gravity was within the prescribed limits for the model of aircraft.[3][5]

Between 1,500 feet (460 m) and 1,800 feet (550 m) down the runway, the aircraft reached

emergency services at Long Island MacArthur promptly responded to the crash, the aircraft was destroyed by the post-crash fire.[3][5]

Investigation

Wreckage examination

The Civil Aeronautics Board (CAB), charged with investigating the accident, examined the wreckage at Long Island MacArthur Airport. Reports from witnesses of the crash indicated the aircraft appeared to have made a normal takeoff and began climbing normally. But, moments later it began banking sharply to the right. Investigators examined the four charred engines and concluded all were producing power at the point of impact.[3][5] They could not conclusively determine the amount of power being produced, but stated there was no evidence found in the wreckage that suggested the engines might have suffered an operational failure.[5][6]

They were also able to determine all of the flight control surfaces, including the elevators, ailerons and rudder, were functioning properly at the point of the crash, and there were no faults in the flight control system. The flaps were extended to between 15° and 20°, the standard setting for take-off. The propeller blades of No. 4 engine— on the far right side of the aircraft—were reversed—minus 8°, while the blades of Nos. 1, 2 and 3 engines were at 34° positive pitch (also standard for take-off).[5][6]

Reversed thrust

A video of a Douglas DC-6.

The propellers of a DC-6 are designed to provide reverse thrust after the aircraft touches down. The pilot then retards the throttle levers to a point below idle speed and that directs the electric mechanisms in the propeller hub to rotate the blades to a position in which they will provide reverse thrust.[6] Should the pilot need to perform a go-around, he moves the thrust levers forward to a positive position again and that will produce forward thrust, enabling the pilot to execute a go-around maneuver.[6]

The Douglas Aircraft Company designed a system that would prevent the accidental reversal of propeller blades in-flight. During development of the DC-6, the company installed a system that cut electrical power to the mechanisms which rotated the blades while the airplane was in the air. When there was enough weight on the landing gear (which would only be the case when the aircraft was on the ground), a switch which supplied electrical power to the mechanisms was closed—meaning that when the aircraft touched down the blades could be reversed and thus the airplane could be slowed. When the switch was closed, a red flag would swing into view in the cockpit of the aircraft, warning the crew that the blades could be reversed. Should the switch fail to close upon landing, the flag could be raised manually and electrical power to the mechanisms would be restored. When the aircraft took off, electrical power would be cut to the mechanisms so that the propeller blades could not be inadvertently reversed, and the red flag swung out of sight. Reverse thrust warning lamps, which would have warned the crew if the propellers were reversed, were not fitted on Mainliner Idaho.[6]

Flight tests

The CAB carried out flight tests using a DC-6. They found that if the propellers were reversed prior to take-off they would not, if the flag was not raised, be rotated automatically again in the air to produce forward thrust if full power was applied. Tests performed by United Airlines showed that, if the propellers of just one engine were reversed and full power was applied to all four engines, then the aircraft would spiral into a dive. If METO (maximum except take-off) power was applied to Nos. 1, 2 and 3 engines, and full reverse thrust was applied to engine No. 4, then the aircraft would become uncontrollable.[5][7]

If full left

stall, and violently roll and pitch down. Flight tests, investigators said, accurately reproduced what happened to Mainliner Idaho during the accident sequence. The tests performed by United and by the investigators showed that if, after the aircraft became airborne, full power was applied to an engine whose propellers were reversed, the propellers would produce not positive thrust, but increased reverse thrust.[5][7]
One aviation author wrote of the crash,

"The flight tests showed conclusively that, at take-off configuration, a DC-6 becomes uncontrollable with an outboard engine at full power with its propeller in reverse pitch. Control is lost so quickly that there is little the crew can do at low altitude. In the case of this accident, it was doubtful if there would have been time for forward thrust to be restored before control was lost."

— Macarthur Job, Air Disaster Vol. 4, 2001[7]

Conclusions

While the wreckage was being examined, investigators found that all four engines were producing thrust at the time of impact. There were only two ways that the propeller could be reversed during the take-off sequence. Investigators ruled out electrical malfunction since, after detailed examination of the engine hub, there was no evidence found of this happening.

engine failure was being performed, statements submitted by witnesses suggested that it was likely this was the case. United Airlines procedure calls for No. 4 engine to be shut down in a simulated engine failure—the same engine which was found at the crash site with its propellers reversed.[5][8]

A set of propeller blades, unattached from an aircraft mounting.
The propellers of a Douglas DC-6 engine, similar to those installed on the engines of Mainliner Idaho

The investigation concluded the accident sequence began when the check pilot, while the aircraft was on the ground, retarded the throttle lever for No. 4 engine past the idle position, and therefore reversed the propellers of that engine. Once the airplane took off and started banking to the right, it would have been a natural reaction for one of the flight crew to increase power to No. 4 engine, thinking that by doing so the engine would start producing positive thrust and the aircraft could be recovered. However, since the metal flag was not raised, there was no electrical power to the rotating mechanisms—and increasing power to No. 4 engine would only have created more reverse thrust.[5][8]

The final accident report concluded there wasn't sufficient time for the crew to react, since the dive began suddenly while the plane was so close to the ground. "Control will be lost so quickly that there is little, if anything, that the pilot can do if it occurs at low altitude," the report stated. "He must recognize what is occurring, analyze it, and take action to unreverse in a very limited amount of time. It is doubtful that unreversing could have been accomplished in this instance before control was lost."[5]

On October 4, 1955, the CAB released the final accident report, which concluded the reversal of the propellers and subsequent increase in power of the No. 4 engine had caused the accident.[5]

"The Board determines that the probable cause of this accident was unintentional movement of No. 4 throttle into the reverse range just before breaking ground, with the other three engines operating at high power output, which resulted in the aircraft very quickly becoming uncontrollable once airborne."

— Civil Aeronautics Board, Accident Investigation Report; United Air Lines, Inc., MacArthur Field, Islip, New York, 1955[5]

Aftermath

Technological advances

Following the accident, the

Civil Aeronautics Administration (CAA) issued an Airworthiness Directive ordering all DC-6 and DC-6B aircraft to be fitted with a sequence gate latch, known as a Martin bar. The device is a metal bar which a crew would manually swing in front of the thrust levers over the idle line, physically preventing the thrust levers from being retarded into the reverse position. According to the CAB report, a United Airlines engineer told investigators the Martin bar should make propeller reversal "a more reliable and safer device [than the system fitted to Mainliner Idaho] ... with its numerous switches, relays, and automatic operation."[5]

United Airlines issued a statement saying it had begun installing the device on its fleet of DC-6 and DC-6B aircraft one week before the accident, having used it successfully in service on their fleet of Douglas DC-7 aircraft. A Martin bar had not yet been fitted on Mainliner Idaho.[7] United Airlines also said a program had begun to install reverse thrust indicator lights on all their DC-6 and DC-6B aircraft. The signals, fitted in the cockpit of the aircraft, would have warned the flight crew that the thrust lever had been pulled back too far, and the propellers had been reversed.[5]

Similar accidents

thrust reversers
deployed in-flight.

Since the crash, there have been several

United Airlines Flight 859 crashed in 1961 when the first officer attempted to reverse all four engines during the landing roll. The left engines remained in forward thrust, while the right engines went into reverse, causing the aircraft to veer rapidly to the right and collide with airport construction vehicles, killing 17 of the 122 people aboard and 1 person on the ground.[9]
Japan Airlines Flight 350, a DC-8, crashed in 1982 short of the runway in Tokyo, after the mentally ill captain attempted suicide during the final approach phase of the flight, by putting the inboard engines into reverse thrust. Of the 174 people aboard, 24 died.[10][11][12][13]
In 1991,
TAM Airlines Fokker 100 in 1996 was attributed to the deployment of the thrust reverser on No. 2 engine. The aircraft rolled to the right and crashed in a populated area of São Paulo, Brazil.[15]

See also

References

Notes
  1. ^ a b "Archives 1955 Jan-Jun". Aircraft Crashes Record Office. Archived from the original on September 1, 2011. Retrieved December 26, 2010.
  2. ^
    Aviation Safety Network. Archived
    from the original on June 6, 2011. Retrieved October 22, 2010.
  3. ^ a b c d e f g h Job 2001, p. 45.
  4. ^ a b c "L. I. Crash Kills 3 Veteran Airline Pilots On Take-Off During Routine Check Hop". New York Times. April 5, 1955. Archived from the original on July 23, 2018. Retrieved December 26, 2010.(subscription required)
  5. ^ a b c d e f g h i j k l m n o p q r s "Accident Investigation Report; United Air Lines, Inc., MacArthur Field, Islip, New York, April 4, 1955". Civil Aeronautics Board. October 4, 1955. Retrieved June 1, 2021. – PDF
  6. ^ a b c d e Job 2001, p. 46.
  7. ^ a b c d Job 2001, p. 47.
  8. ^ a b c Job 2001, p. 49.
  9. ^ "Aircraft Accident Report: United Airlines Flight 859". Civil Aeronautics Board. July 16, 1962. Retrieved January 28, 2016.
  10. ^ "Accident Database: Accident Synopsis 02091982". Archived from the original on 2015-03-30. Retrieved 2011-07-11.{{cite web}}: CS1 maint: unfit URL (link)
  11. ^ COCKPIT FIGHT REPORTED ON JET THAT CRASHED IN TOKYO Archived 2008-05-02 at the Wayback Machine", The New York Times. February 14, 1982. Retrieved on June 24, 2011.
  12. ^ "Troubled Pilot". Time. 1982-03-01. Archived from the original on 2008-05-02. Retrieved 2007-04-20.
  13. ^ "Final Accident Report". Archived from the original on 2011-07-22. Retrieved 2011-07-11.
  14. ^ "Lauda Air B767 Accident Report". Aircraft Accident Investigation Committee of Thailand. Archived from the original on June 7, 2011. Retrieved January 23, 2011.
  15. Aviation Safety Network. Archived
    from the original on January 23, 2009. Retrieved January 23, 2010.
Bibliography

External links

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