Contenido

El "pompaje" o "pérdida del compresor" son pérdidas aerodinámicas durante las cuales los álabes del compresor exceden sus posibilidades de sustentación. Este puede ocurrir por varias razones y trae como consecuencia que el compresor pierda su potencia o se pase de los límites para los que fue diseñado.

Factors affecting compressor performance

• - Damage to compressor components caused by ingestion of foreign objects. One of the most common cases in commercial aviation is a collision with birds in flight, which occurs during takeoff or on the approach to landing, even when taxiing on the ground. When sucked into engines, these animals cause great damage to the compressor blades, which causes pumping. Other cases of ingestion occur on the runways with pieces of rubber or metal parts that fell from other planes. For this reason the tracks must be continually inspected to remove all objects that could be sucked into the engines.

• - Compressor elements with the presence of corrosion or contamination of other types. Ingestion of dust in extreme quantities or sand.

• - The flow reaching the air inlet intakes under large angles of attack.

Factors that increase loads on the compressor

• - When the airplane exceeds its operating limits by performing extreme maneuvers that separate the air flow from the air inlet channels to the engine.

• - Flight in very low temperatures that forms layers of ice on the edges of the air intake channel to the engine.

• - Engine operation outside the established regimes: Sudden increase in thrust that causes desynchronization of the engine components.

• - Turbulent and hot air that bathes the air inlet channel to the engine: Use of the thrust reverser at very low speed, which results in the ingestion of turbulent hot air and in the case of military aircraft, the ingestion of gases from the firing of missiles and rockets.

Engine pomp is immediately recognizable because it produces a very loud explosion coming from the engine, which can be repeated continuously as long as the conditions that create it are maintained. Reports of flares ejecting from the engine are common during these stall phenomena. These phenomena may be accompanied by an increase in temperature and revolutions due to the reduction in compressor work, and in the case of airplanes with multiple engines, they may cause slippage in the direction of the affected engine, as thrust is lost. Large stress forces can affect the engine and structure, due to the high aerodynamic resistance created by the compressor of the affected engine.

The measures taken to avoid pumping vary depending on the type of engine and the situation created. The fundamental measure in almost all turbojet engines is the immediate reduction of the fuel supply to the affected engine. However, there are a whole series of constructive measures that manufacturers have added to avoid this phenomenon:

• - The creation of special valves in the compressor stage that drain excess air in case of overload.

• - Incorporation of windows in the air intake channels to the engine that guarantee that it receives the necessary amount at all times.

• - Automatic devices that regulate the angle of attack of the compressor stator blades, thus increasing their resistance to enter the stall phenomenon.

In aircraft development

The engine of the SR-71 Black Bird supersonic reconnaissance aircraft, the P&W J58, was known for its tendency toward spectacular sputtering, known as "hard unstart." These compressor losses were so violent that they caused the pilot to bang his head against the canopy of the aircraft.

This behavior occurs because the deflection of the supersonic shock waves moved beyond the correct positions at the limits of the engine air intake channels, all during supersonic flight. When this happens, a large air loss is created in the specific intake where the phenomenon occurs, which thins the gas that penetrates to the engines, resulting in compressor pumping and a drop in thrust of the affected engine. The loss of thrust causes a violent slip in the direction of the affected engine that requires rapid action by the crew to prevent the structure from being damaged by the large loads it experiences at these speeds. Jumps were the bane of SR-71 pilots until the advent of computer control of the engines, which significantly reduced the occurrence of such unwanted phenomena.

During the development process of the Concorde commercial supersonic airliner, the occurrence of engine pomp was recognized as a potential problem. Because the Concorde needed very high performance to fly over the Atlantic, the engines had to be pushed very close to their overload limit. During one of the test programs, it was the case that a bubble appeared in one of the motors caused a violent expulsion of air that destroyed the adjustable ramp at the inlet of the air channel, this despite the fact that in most cases the motor was physically capable of withstanding the overload. The problem was solved when a digital air intake control system was developed that calculated the appropriate speed of the compressor rotor to keep it below the overload limit and transmitted this information to the engine controls. Since then, air overload has not been a problem on routine flights.

Aviation accidents as a result of pompom

The loss in 1977 of the DC-9 of Southern Airways Flight 242 while entering a storm cloud was attributed to the appearance of pompom, caused by the ingestion of a large amount of water and hail that blocked the expulsion of turbulence by the mechanisms of its two JT8D-9 engines. The accident occurred over the state of Georgia "Georgia (United States)") in the United States. The noise in the engines was so severe as to cause their destruction, forcing the crew to make a forced landing on a public road; 62 passengers and 8 people on the ground were killed in the accident.

On November 6, 1967, TWA Flight 159, a Boeing 707, while accelerating for takeoff sucked hot gases from the engines of Flight 379, a Delta Air Lines DC-9. The first officer on the TWA flight heard an explosion and, believing they had collided with the Delta Air Lines DC-9, canceled takeoff. Due to the high speed of the aircraft, it left the runway, injuring 11 of the 29 passengers who boarded the plane. This explosion was the result of engine noise due to ingestion of Delta DC-9 gases.

On January 15, 2009, US Airways Flight 1549, an Airbus 320, landed in the Hudson River just 5 minutes after takeoff. The apparent cause was the appearance of noise in both engines when passing through a flock of birds 90 seconds after takeoff. This same plane may have suffered a leak in the right engine two days before.[3][4]​.

Following an incident during which an Airbus 321-200 experienced a surge in both engines during initial climb on December 5, 2008, an emergency airworthiness directive issued by EADS, 2008-228, requested operators of the CFM56-5B" engine (also mounted on the aircraft that landed in the Hudson River) to monitor engine temperatures and ensure that these temperatures were not exceed 80 °C deterioration. The FAA has established the same requirement in airworthiness directive AD 2009-01-01 with immediate effect.[5]​.

Literature

• - video of compressor stall, following bird ingestion.

Contenido

El "pompaje" o "pérdida del compresor" son pérdidas aerodinámicas durante las cuales los álabes del compresor exceden sus posibilidades de sustentación. Este puede ocurrir por varias razones y trae como consecuencia que el compresor pierda su potencia o se pase de los límites para los que fue diseñado.

Factors affecting compressor performance

• - Damage to compressor components caused by ingestion of foreign objects. One of the most common cases in commercial aviation is a collision with birds in flight, which occurs during takeoff or on the approach to landing, even when taxiing on the ground. When sucked into engines, these animals cause great damage to the compressor blades, which causes pumping. Other cases of ingestion occur on the runways with pieces of rubber or metal parts that fell from other planes. For this reason the tracks must be continually inspected to remove all objects that could be sucked into the engines.

• - Compressor elements with the presence of corrosion or contamination of other types. Ingestion of dust in extreme quantities or sand.

• - The flow reaching the air inlet intakes under large angles of attack.

Factors that increase loads on the compressor

• - When the airplane exceeds its operating limits by performing extreme maneuvers that separate the air flow from the air inlet channels to the engine.

• - Flight in very low temperatures that forms layers of ice on the edges of the air intake channel to the engine.

• - Engine operation outside the established regimes: Sudden increase in thrust that causes desynchronization of the engine components.

• - Turbulent and hot air that bathes the air inlet channel to the engine: Use of the thrust reverser at very low speed, which results in the ingestion of turbulent hot air and in the case of military aircraft, the ingestion of gases from the firing of missiles and rockets.

Engine pomp is immediately recognizable because it produces a very loud explosion coming from the engine, which can be repeated continuously as long as the conditions that create it are maintained. Reports of flares ejecting from the engine are common during these stall phenomena. These phenomena may be accompanied by an increase in temperature and revolutions due to the reduction in compressor work, and in the case of airplanes with multiple engines, they may cause slippage in the direction of the affected engine, as thrust is lost. Large stress forces can affect the engine and structure, due to the high aerodynamic resistance created by the compressor of the affected engine.

The measures taken to avoid pumping vary depending on the type of engine and the situation created. The fundamental measure in almost all turbojet engines is the immediate reduction of the fuel supply to the affected engine. However, there are a whole series of constructive measures that manufacturers have added to avoid this phenomenon:

• - The creation of special valves in the compressor stage that drain excess air in case of overload.

• - Incorporation of windows in the air intake channels to the engine that guarantee that it receives the necessary amount at all times.

• - Automatic devices that regulate the angle of attack of the compressor stator blades, thus increasing their resistance to enter the stall phenomenon.

In aircraft development

The engine of the SR-71 Black Bird supersonic reconnaissance aircraft, the P&W J58, was known for its tendency toward spectacular sputtering, known as "hard unstart." These compressor losses were so violent that they caused the pilot to bang his head against the canopy of the aircraft.

This behavior occurs because the deflection of the supersonic shock waves moved beyond the correct positions at the limits of the engine air intake channels, all during supersonic flight. When this happens, a large air loss is created in the specific intake where the phenomenon occurs, which thins the gas that penetrates to the engines, resulting in compressor pumping and a drop in thrust of the affected engine. The loss of thrust causes a violent slip in the direction of the affected engine that requires rapid action by the crew to prevent the structure from being damaged by the large loads it experiences at these speeds. Jumps were the bane of SR-71 pilots until the advent of computer control of the engines, which significantly reduced the occurrence of such unwanted phenomena.

During the development process of the Concorde commercial supersonic airliner, the occurrence of engine pomp was recognized as a potential problem. Because the Concorde needed very high performance to fly over the Atlantic, the engines had to be pushed very close to their overload limit. During one of the test programs, it was the case that a bubble appeared in one of the motors caused a violent expulsion of air that destroyed the adjustable ramp at the inlet of the air channel, this despite the fact that in most cases the motor was physically capable of withstanding the overload. The problem was solved when a digital air intake control system was developed that calculated the appropriate speed of the compressor rotor to keep it below the overload limit and transmitted this information to the engine controls. Since then, air overload has not been a problem on routine flights.

Aviation accidents as a result of pompom

The loss in 1977 of the DC-9 of Southern Airways Flight 242 while entering a storm cloud was attributed to the appearance of pompom, caused by the ingestion of a large amount of water and hail that blocked the expulsion of turbulence by the mechanisms of its two JT8D-9 engines. The accident occurred over the state of Georgia "Georgia (United States)") in the United States. The noise in the engines was so severe as to cause their destruction, forcing the crew to make a forced landing on a public road; 62 passengers and 8 people on the ground were killed in the accident.

On November 6, 1967, TWA Flight 159, a Boeing 707, while accelerating for takeoff sucked hot gases from the engines of Flight 379, a Delta Air Lines DC-9. The first officer on the TWA flight heard an explosion and, believing they had collided with the Delta Air Lines DC-9, canceled takeoff. Due to the high speed of the aircraft, it left the runway, injuring 11 of the 29 passengers who boarded the plane. This explosion was the result of engine noise due to ingestion of Delta DC-9 gases.

On January 15, 2009, US Airways Flight 1549, an Airbus 320, landed in the Hudson River just 5 minutes after takeoff. The apparent cause was the appearance of noise in both engines when passing through a flock of birds 90 seconds after takeoff. This same plane may have suffered a leak in the right engine two days before.[3][4]​.

Following an incident during which an Airbus 321-200 experienced a surge in both engines during initial climb on December 5, 2008, an emergency airworthiness directive issued by EADS, 2008-228, requested operators of the CFM56-5B" engine (also mounted on the aircraft that landed in the Hudson River) to monitor engine temperatures and ensure that these temperatures were not exceed 80 °C deterioration. The FAA has established the same requirement in airworthiness directive AD 2009-01-01 with immediate effect.[5]​.

Literature

• - video of compressor stall, following bird ingestion.