Aircraft fuel tanks are a major component of aircraft fuel systems. They can be classified into internal or external fuel tanks and can be further classified by method of construction or intended use. Safety aspects of aircraft fuel tanks were examined during the investigation of the 1996 TWA Flight 800 in-flight explosion accident.
Integral tanks are areas inside the aircraft structure that have been sealed to allow fuel storage. An example of this type is the "wet wing", commonly used in larger aircraft. Since these tanks are part of the aircraft structure, they cannot be removed for service or inspection. Inspection panels must be provided to allow internal inspection, repair, and overall servicing of the tank. Most large transport aircraft use this system to store fuel in the wings, fuselage and empennage of the aircraft. [1]
Rigid removable tanks are installed in a compartment designed to accommodate the tank. They are typically made of metal, plastic or fibreglass construction, and may be removed for inspection, replacement, or repair. [2] Rigid removable tanks are not relied on for the aircraft's structural integrity. These tanks are commonly found in smaller general aviation aircraft, such as the Cessna 172. Combat aircraft and helicopters generally use self-sealing fuel tanks. [1]
Bladder tanks, bag tanks or fuel cells, are reinforced rubberised bags installed in a section of aircraft structure designed to accommodate fuel. The bladder is rolled up and installed into the compartment through the fuel filler neck or access panel, and is secured by means of snap fasteners or cord and loops inside the compartment. Many high-performance light aircraft, helicopters and some smaller turboprop aircraft use bladder tanks. [1]
Many aircraft designs feature fixed tip tanks mounted at the end of each wing. The weight of the tanks and fuel counteract wing bending loads during manoeuvres and reduce fatigue on the spar structure.[ citation needed ]
Conformal fuel tanks (CFTs) or "fast packs" are additional fuel tanks fitted closely to the profile of an aircraft which extend either the range or endurance of the aircraft, with a reduced aerodynamic penalty compared to external drop tanks. [3]
Drop tanks, external tanks, wing tanks, pylon tanks or belly tanks are all terms used to describe auxiliary externally mounted fuel tanks. Drop tanks are generally expendable and often jettisonable. External tanks are commonplace on modern military aircraft and occasionally found in civilian ones, although the latter are less likely to be discarded except in the event of emergency. [1]
Drop tanks were originally designed to be jettisoned when empty or in the event of combat or emergency in order to reduce drag and weight, increasing manoeuvrability and range. Modern external tanks may be retained in combat, to be dropped in an emergency and are often not designed for the stresses of supersonic flight. [1]
Fuel tanks have been implicated in aviation disasters, being the cause of the accident or worsening it (fuel tank explosion).
The official explanation for the explosion and subsequent crash of TWA Flight 800 is that an explosive fuel/air mixture was created in one of the aircraft's fuel tanks. Faulty wiring then provided an ignition source within the tank, destroying the airliner. [4] While the accuracy of the official findings is still questioned in this case, similar explosions have occurred in other aircraft. It is possible to reduce the chance of fuel tank explosions by a fuel tank inerting system or fire fighting foam in the tanks. [5]
The Boeing 737, for example, has two systems that reduce the chance of a fuel tank ignition. One shuts off fuel pumps when fuel output pressure is low, to prevent them from heating (since they rely on the fuel itself for cooling). The other enriches the nitrogen levels in the air in the fuel tank, so there is insufficient oxygen there for burning. [6] The aircraft engines are also capable of getting fuel via suction in the result of a failure in the backup pumps, though this produces less reliable thrust. [6]
On passenger planes, fuel tanks are often integrated into the wings, and when there are also tanks inside the body of the aircraft, the wing tanks are used preferentially. [7] [6] The placement reduces the stress on the wings during takeoff and flight, by putting the heavy fuel directly inside the source of lift. [7] Putting tanks in the main wings rather than near the tail or nose also reduces the amount of weight that is off-center from the plane's center of gravity, and which changes as it flies [7] and which would make the aircraft less efficient by requiring increased use of elevators. [6] Given their irregular shape and lack of windows, wings are often unusable for storage of cargo or seating of passengers. But their hollow structure makes in-wing fuel storage feasible and an efficient use of space; the presence of structural spars in "wet wing" tanks reduces sloshing. [6] Placement of fuel tanks in the wings also moves them further from passengers and crew in the event of a leak or explosion.[ citation needed ]
Trans World Airlines Flight 800 was a Boeing 747-100 that exploded and crashed into the Atlantic Ocean near East Moriches, New York, on July 17, 1996, at about 8:31 p.m. EDT, 12 minutes after takeoff from John F. Kennedy International Airport on a scheduled international passenger flight to Rome, with a stopover in Paris. All 230 people on board died in the crash; it is the third-deadliest aviation accident in U.S. history. Accident investigators from the National Transportation Safety Board (NTSB) traveled to the scene, arriving the following morning amid speculation that a terrorist attack was the cause of the crash. Consequently, the Federal Bureau of Investigation (FBI) and New York Police Department Joint Terrorism Task Force (JTTF) initiated a parallel criminal investigation. Sixteen months later, the JTTF announced that no evidence of a criminal act had been found and closed its active investigation.
An inerting system decreases the probability of combustion of flammable materials stored in a confined space. The most common such system is a fuel tank containing a combustable liquid, such as gasoline, diesel fuel, aviation fuel, jet fuel, or rocket propellant. After being fully filled, and during use, there is a space above the fuel, called the ullage, that contains evaporated fuel mixed with air, which contains the oxygen necessary for combustion. Under the right conditions this mixture can ignite. An inerting system replaces the air with an inert gas, such as nitrogen, which can not support combustion.
The Apollo spacecraft was composed of three parts designed to accomplish the American Apollo program's goal of landing astronauts on the Moon by the end of the 1960s and returning them safely to Earth. The expendable (single-use) spacecraft consisted of a combined command and service module (CSM) and an Apollo Lunar Module (LM). Two additional components complemented the spacecraft stack for space vehicle assembly: a spacecraft–LM adapter (SLA) designed to shield the LM from the aerodynamic stress of launch and to connect the CSM to the Saturn launch vehicle and a launch escape system (LES) to carry the crew in the command module safely away from the launch vehicle in the event of a launch emergency.
The Apollo command and service module (CSM) was one of two principal components of the United States Apollo spacecraft, used for the Apollo program, which landed astronauts on the Moon between 1969 and 1972. The CSM functioned as a mother ship, which carried a crew of three astronauts and the second Apollo spacecraft, the Apollo Lunar Module, to lunar orbit, and brought the astronauts back to Earth. It consisted of two parts: the conical command module, a cabin that housed the crew and carried equipment needed for atmospheric reentry and splashdown; and the cylindrical service module which provided propulsion, electrical power and storage for various consumables required during a mission. An umbilical connection transferred power and consumables between the two modules. Just before reentry of the command module on the return home, the umbilical connection was severed and the service module was cast off and allowed to burn up in the atmosphere.
In aviation, a drop tank is used to describe auxiliary fuel tanks externally carried by aircraft. A drop tank is expendable and often jettisonable. External tanks are commonplace on modern military aircraft and occasionally found in civilian ones, although the latter are less likely to be discarded except in the event of emergency.
A fuel tank is a safe container for flammable fluids. Though any storage tank for fuel may be so called, the term is typically applied to part of an engine system in which the fuel is stored and propelled or released into an engine. Fuel tanks range in size and complexity from the small plastic tank of a butane lighter to the multi-chambered cryogenic Space Shuttle external tank.
Pan Am Flight 214 was a scheduled flight of Pan American World Airways from San Juan, Puerto Rico, to Baltimore, Maryland, and Philadelphia, Pennsylvania. On December 8, 1963, the Boeing 707 serving the flight crashed near Elkton, Maryland, while flying from Baltimore to Philadelphia, after being hit by lightning. All 81 occupants of the plane were killed. The crash was Pan Am's first fatal accident with the 707, which it had introduced to its fleet five years earlier.
The Boeing Model 307 Stratoliner was an American commercial transport aircraft that entered commercial service in July 1940. It was the first to offer a pressurized cabin, allowing it to cruise at an altitude of 20,000 ft (6,000 m), well above many weather disturbances. The pressure differential was 2.5 psi (17 kPa), so at 14,700 ft (4,480 m) the cabin air pressure was equivalent to an altitude of 8,000 ft (2,440 m). The Model 307 had capacity for a crew of six and 33 passengers. The cabin was nearly 12 ft (3.6 m) across. It was the first land-based aircraft to include a flight engineer as a crew member. In addition to its civilian service it was also flown as the Boeing C-75 Stratoliner by the United States Army Air Forces, who used it as a long-range cargolift aircraft.
A hardpoint is a location on an airframe designed to carry an external or internal load. This includes a station on the wing or fuselage of a civilian aircraft or military aircraft where external jet engine, ordnance, countermeasures, gun pods, targeting pods or drop tanks can be mounted.
Chalk's Ocean Airways Flight 101 was an aircraft crash that occurred off Miami Beach, Florida, in the United States on December 19, 2005. All 20 passengers and crew on board the 1947 Grumman G-73T Turbine Mallard died in the crash, which was attributed to metal fatigue on the starboard wing resulting in separation of the wing from the fuselage.
Fuel dumping is a procedure used by aircraft in certain emergency situations before a return to the airport shortly after takeoff, or before landing short of the intended destination to reduce the aircraft's weight.
In a fixed-wing aircraft, the spar is often the main structural member of the wing, running spanwise at right angles to the fuselage. The spar carries flight loads and the weight of the wings while on the ground. Other structural and forming members such as ribs may be attached to the spar or spars, with stressed skin construction also sharing the loads where it is used. There may be more than one spar in a wing or none at all. However, where a single spar carries most of the force, it is known as the main spar.
The bomb bay or weapons bay on some military aircraft is a compartment to carry bombs, usually in the aircraft's fuselage, with "bomb bay doors" which open at the bottom. The bomb bay doors are opened and the bombs are dropped when over the target or at a specified launching point.
A wet wing is an aerospace engineering technique where an aircraft's wing structure is sealed and used as a fuel tank.
In 2002, two large airtankers – a Lockheed C-130 Hercules and a Consolidated PB4Y-2 Privateer – crashed about a month apart while performing aerial firefighting operations. These crashes prompted a review of the maintenance and use of the entire U.S. large airtanker fleet. Ultimately, the whole fleet was grounded, dramatically reducing the resources available to fight major wildfires. Both aircraft were owned by Hawkins & Powers Aviation of Greybull, Wyoming and operated under contract to the United States Forest Service (USFS). The crashes occurred in one of the worst fire seasons in the last half century, one in which 73,000 fires burned 7.2 million acres (29,000 km2) of land.
The Curtiss XBT2C was a prototype two-seat, single-engined dive/torpedo bomber developed during World War II for the United States Navy. Derived from the Curtiss SB2C Helldiver dive bomber, it was an unsuccessful competitor to meet a 1945 Navy specification for an aircraft to combine the roles that previously required separate types. Unlike the other competitors, the XBT2C was designed to accommodate a radar operator.
Philippine Airlines Flight 143 (PR143) was a domestic flight from the Manila Ninoy Aquino Airport, Manila, Philippines to Mandurriao Airport, Iloilo City. On May 11, 1990, at Manila Ninoy Aquino International Airport the Boeing 737-300 assigned to the route suffered an explosion in the central fuel tank and was consumed by fire in as little as four minutes.
The Kamov V-80 was a design study designation for an attack helicopter that eventually evolved into the single seat Kamov Ka-50 family of aircraft.
An aircraft fuel system allows the crew to pump, manage, and deliver aviation fuel to the propulsion system and auxiliary power unit (APU) of an aircraft. Fuel systems differ greatly due to different performance of the aircraft in which they are installed. A single-engine piston aircraft has a simple fuel system; a tanker, in addition to managing its own fuel, can also provide fuel to other aircraft.
Fuel bladders, fuel storage bladders, or Flexi-bags are collapsible, flexible storage bladders that provide temporary or long term storage for industrial liquids. These pillow shaped tanks are designed for large volume liquid transport, industrial chemicals, potable water, sludge, and fuel storage. Standard fuel bladder tanks sizes range from 100 US gallons (380 L) to 200,000 US gallons (760,000 L) capacities and larger and custom fuel storage bladders and cells are available, although at sizes exceeding 50,000 US gallons (190,000 L) there is an increased spill risk. To minimize the risk of leakage, and for the sake of containing a catastrophic spill, all fuel bladders should be housed in secondary containment (bunding). The use of fuel bladders without precautionary measures is risky and should not be undertaken. The fines involved with fuel spills are well known and the EPA has set clear guidelines for the use of secondary containment concerning fuel bladders.
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