Utilisateur:Aerophile5390/Traduction/1955 MacArthur Airport United Airlines Crash

Crash de la United Airlines à l'aéroport MarArthur
Caractéristiques de l'accident
Date	4 avril 195
Type	Erreur de pilotage
Site	Long Island MacArthur Airport, Ronkonkoma, Islip, New York, États-Unis
Caractéristiques de l'appareil
Type d'appareil	Douglas DC-6 Mainliner Idaho
Compagnie	United Airlines
No  d'identification	N37512
Phase	A United Airlines Douglas DC-6, similar to Mainliner Idaho, the aircraft involved in the accident
Équipage	3
Morts	3 (tous)
Blessés	0
Survivants	0

destination = LaGuardia Airport, New York City, New York, United States

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 aircraft, registration number N37512, was performing an instrument rating check flight, when, shortly after taking off, it began banking to the right. Seconds after climbing through 150 pieds ( ), the aircraft turned through 90 degrees, causing the nose to drop suddenly, before it impacted with the ground.

Le 4 avril 1955, un Douglas DC-6 de la United Airlines nommé Mainliner Idaho s'est écrasé peu après le décollage de l'aéroport Long Island MacArthur, à Ronkonkoma, Islip, New York, États-Unis. L'avion, numéro d'identification N37512, faisait un vol de qualification de vol aux instruments, quand, peu après le décollage, il commença soudain à pencher vers la droite. Quelques secondes après être monté en altitude à 150 pieds, l'avion a fait une rotation de 90 degrés, faisant chuter soudainement le nez de l'appareil, avant qu'il s'écrase sur le sol.

A subsequent investigation found that the flight crew were simulating an engine failure, which involved a member of the crew pulling back the throttle lever for engine No. 4 prior to taking off. Investigators found that if the throttle lever was pulled back too far, however, 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. Investigators from the Civil Aeronautics Board (CAB) concluded that one of the flight crew applied full power to No. 4 engine, thinking this would bring the aircraft out of the increasing bank. But because the blades were reversed and the flag was not raised, the dramatically increased reverse thrust caused the DC-6 to spiral out of control. The investigators also concluded that the suddenness of the bank and dive meant the flight crew had little chance to recover the aircraft before impact.

Une recherche subséquente a trouvé que le personnel naviguant technique étaient en train de simuler une panne moteur, qui incluait qu'un membre du personnel de bord tire en arrière le levier (throttle?) pour l'engin n°4 avant le décollage. Les enquêteurs ont trouvé que si le levier était tiré trop en arrière, cependantl, il causerait à un inversion d'hélice, une manoeuvre permettant de ralentir l'avoin à l'atterrissage. Une fois que le train d'atterrissage était levé, le personnel de bord aurait levé un drapeau en métal dans le cockpit pour ramener les hélices dans le position correcte, puisque un système de sécurité empêchait le système électrique d'opérer sur le mécanisme rotatif au pied des hélices sauf si l'avion était sur le sol ou le drapeau manuellement levé. Les enquêteurs du Civil Aeronautics Board (CAB) ont conclus que quelqu'un du personnel naviguant a appliqué la puissance maximale sur l'engin n°4, pensnat que cela ramènerait l'vion hors de (increasing bank ?). Mais à cause du fait que les pales de l'hélice avaient été inversé et que le drapeau n'était pas levé, l'augmentation dramatique de la puissance de l'hélice causa au DC-6 une spirale hors de contrôle. Les enquêteurs ont conclus que la rapidité du retour et chute signifiant que le personnel de bord avait peu de chances de récupérer l'avion avant l'impact.

In the aftermath of the accident, the Civil Aeronautics Administration (CAA) issued an Airworthiness Directive ordering all DC-6 and DC-6B aircraft 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.

À la suite de cet accident, l'Administration aéronautique civile (CAA) publia une directive ordonnant que tous les DC-6 et DC-6B soient complétés avec un système manuel empêchant le renversement inopiné des pales d'hélice. United Airlins déclara aussi qu'ils avaient commencé à installer des voyants indicateur d'une inverse moteur dans les cockpits de leur appareils DC-6, qui signalerait aux pilots qu'une hélice a été inversée.

History

On April 4, 1955, a United Airlines check captain, Stanley C. Hoyt, age 45, was carrying out instrument rating checks on two of the airline's pilots. Hoyt had been employed by United Airlines in 1937, and had 9,763 flying hours experience, 549 of which were in a DC-6. He was training the two pilots, Henry M. Dozier, age 40, and Vernis H. Webb, age 35, so they would be able to retain an instrument rating qualification, allowing them to fly under instrument flight rules. The aircraft was a Douglas DC-6, registration N37512, serial number 43001. The airframe had flown 22,068 flying hours, and had undergone an inspection 105 hours before the accident. The aircraft was powered by four Pratt & Whitney R2800-CB16 engines, fitted with Hamilton Standard 43E60-317 propellers.

Le 4 avril 1955, un capitaine de vérification de la United Airlines, Stanley C. Hoyt, âgé de 45 ans, effectuait une vérification de quatification de vol aux instruments sur deux des pilotes de la compagnie. Hoyt a été employé par United Airlines en 1937, et avait 9763 heures d'expérience de vol, 549 desquelles était dans un DC-6. Il entraînant les deux pilotes, Henry M. Dozier, âgé de 40 ans, et Vernis H. Webb, âgè de 35 ans, pour qu'ils soient capables d'obtenir une qualification de vol aux instruments, leur permettant de voler sous les règles d'instruments de vol. L'avion étiat un Douglas DC-6, numéro d'identification N37512, numéro de série 43001. La carlingue avait volé 22068 heures de vol, et subit une inspection 105 heures avant l'accident. L'avion était constitué de 4 moteurs Pratt & Whitner R2800-CB16, complétés avec des propulseurs Hamilton Standard 43E60-317.

The weather on the day of the accident was clear, although there was a strong wind of about 20  ( ) hitting the airfield from the southwest, with occasional gusts of wind as fast as 30  ( ). 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. Loaded with around 61,000 livres (27,66913457 kg), the aircraft was far below its maximum permissible weight and the center of gravity was within the prescribed limits for the model of aircraft.

Les conditions météo le jour de l'accident étaient claires, bien qu'il y avait un fort vent d'envirion 20 noeuds touchant l'espace aérien depuis le Sud-Ouest, avec des poussées occasionnelles de vent de près de 30 noeuds. L'appareil fit plusieurs circuits, décollage et atterissage, avant que des témoins observèrent l'avion se tenant à l'extrémité de la piste et alors décolle à environ 15:50 Eastern Standard Time. Chargé avec environ 61000 livres, l'avion était bien en-dessous du poids maaximal permis et le centre de gravité se trouvait à l'intérieur des limites prescrites pour le modèle d'avion.

Between 1 500 pieds (457,2 m) and 1 800 pieds (548,64 m) down the runway, the aircraft reached take-off speed, lifted off the ground, and began climbing normally as the crew retracted the landing gear. Upon climbing through 50 pieds (15,24 m), however, the aircraft began banking right. The climbing bank continued to increase at a rate which alarmed witnesses, and soon after the aircraft rotated through 90° (at which point the wings were vertical to the ground). At a height of around 150 pieds (45,72 m), with all four engines producing take-off thrust, the nose began to fall, and the aircraft stalled. The right wing and nose impacted with the ground, causing the fuselage to cartwheel over, before the aircraft came to rest the correct side up and was engulfed in flames. Though emergency services at Long Island MacArthur responded to the crash, all three members of the flight crew had been killed on impact. The aircraft was destroyed by the post-crash fire.

Entre 1500 pieds et 1800 pieds en bas de la piste, l'avion atteignit la vitesse de désollage, se souleva du sol et commença à grimper normalement tandis le personnel de bord remontait le train d'atterissage. L'angle de montée continua à augmenter à un rythme qui alarma les témoins, et peu après que l'appareil ait rotaté de 90 degrés (à ce point, les ailes étaient verticales au sol). À une hauteur d'environ 150 pieds avec tout les quatre engins produisant une poussée de décollage, le nez commença à tomber, et l'avion décrocha. L'aile droite et le nez impacta le sol, forçant le fuselage à rouler autout, avant que l'avion se pose sur le bon côté et soit entouré de flammes. Bien que les services d'urgence à Long Island MacArthur aient répondu au crash, tout les trois membres d'équipage ont été tués à l'impact. L'appareil fut détruit par le feu post-crash.

Investigation

Wreckage examination

A Pratt & Whitney R-2800 engine, the type of engine installed on Douglas DC-6 aircraft

The Civil Aeronautics Board (CAB), the organization charged with investigating the accident, went to Long Island MacArthur Airport to examine the wreckage. Upon hearing reports from witnesses of the crash that the aircraft appeared to have rotated and begun climbing normally before it began banking sharply to the right, investigators examined the four charred engines. While they had all been severely damaged by the impact and subsequent fire, it was concluded that all four were producing power at the point of impact. The CAB could not conclusively determine the amount of power being produced, but investigators stated there was no evidence found in the wreckage that suggested the engines might have suffered an operational failure.

Investigators were also able to determine all of the flight control surfaces, including the elevators, ailerons and rudder, were functioning correctly at the point of the crash, and it was also found there were no faults in the flight control system of the aircraft. The flaps, it was found, were extended to between 15° and 20°, the standard setting for take-off. Investigators did discover, however, that the propeller blades of No. 4 engine—the engine on the far right side of the aircraft—were reversed. While the blades of Nos. 1, 2 and 3 engines were at 34° positive pitch (also standard for take-off), the blades of No. 4 engine were set at full reverse pitch—minus 8°.

Reversed thrust

A video of a Douglas DC-6. From 00:04–00:10, the propeller blades rotate; this is the feature that led to the accident.

The propellers of a DC-6 are designed to provide reverse thrust when the aircraft touches down. When this feature is activated, the propellers begin producing thrust in the opposite direction, propelling the aircraft backwards to slow it down. When the crew then retards the throttle levers, electric mechanisms in the propeller hub rotate the blades to a position in which they will provide reverse thrust. Should a crew need to perform a go-around, they could restore the thrust levers to a positive position and again produce forward thrust, allowing them to execute the maneuver.

The Douglas Aircraft Company, however, 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.

Flight tests

The nose gear of a Douglas DC-6

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.

If full left aileron was applied, the aircraft could be recovered for a short period of time, but a violent turn to the right would continue, and the competing forces would cause the aircraft to 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. 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

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. Therefore, it was concluded that the only way the propeller could have been reversed was through an unintentional crew action. Although there was no formal evidence that a simulated 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.

The propellers of a Douglas DC-6 engine, similar to those installed on the engines of Mainliner Idaho

The investigation concluded that 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 the aircraft. 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.

The final accident report concluded that there was no time for the crew to react, since the dive began so suddenly, and there was no way for the crew to recover the aircraft. "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." On October 4, 1955, the CAB released the final accident report, which concluded the reversal of the propellers and subsequent increase in power to No. 4 engine had caused the accident.

« "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

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."

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. 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.

Similar accidents

A Lauda Air Boeing 767, similar to the aircraft which crashed in 1991 after one of the thrust reversers deployed in-flight.

Since the crash, there have been several other accidents involving reverse thrust. A Douglas DC-8 operating 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 18 of the 122 people aboard. 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. In 1991, Lauda Air Flight 004, operated by a Boeing 767, crashed after the left engine thrust reverser deployed in-flight for reasons that could not be determined. The crash of a 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. In 2009, a Boeing 707 operated by Azza Transport crashed shortly after taking off; upon examining the wreckage of the aircraft, investigators found the No. 4 engine thrust reverser had deployed.

See also

• Air safety
• List of accidents and incidents involving commercial aircraft
• 1955 in aviation

References

Notes

Bibliography

Category:Accidents and incidents involving the Douglas DC-6 Category:Airliner accidents and incidents in New York Category:Aviation accidents and incidents in 1955 Category:Airliner accidents and incidents caused by pilot error Category:Islip (town), New York Category:Transportation accidents in New York City Category:United Airlines accidents and incidents Macarthur Airport United Airlines Crash, 1955