Management and control of the fuel system. Fuel system Layout of fuel tanks on an aircraft

The engine fuel system is designed to supply the engine with fuel during startup and in all operating modes. The engine fuel system consists of a main fuel system and a starting fuel system.

The fuel on the aircraft is placed in interconnected fuel tanks under an excess pressure of 0.1 kg. per cm sq.

The aircraft fuel system ensures the supply of fuel from the tanks to the engines in a given sequence in all operating modes of the aircraft and at any position in the air. The fuel system includes tanks that hold the fuel; units, devices and fuel lines for refueling tanks on the ground; units, devices and pipelines that supply fuel from tanks to engines; motor power supply system under zero and negative overloads; instruments and devices for monitoring work fuel system on the ground and in the air; units, devices and pipelines for pressurization and drainage of fuel tanks.

fuel is located in two fuselage tank compartments - tank No. 1 (front) and tank No. 2 (rear), in the tank in the center section, located above tank No. 2, in the wing tanks (one in each console). There are a total of 5 fuel tanks in the Su-25 aircraft. Four outboard fuel tanks can be installed under the aircraft wing consoles, two under each console. The total operational capacity of the fuel tanks is 3660 liters, including the capacity of the fuselage fuel tanks is 2386 liters, the capacity of the tank compartment of each console is 637 liters. Fuel from the outboard fuel tanks is squeezed into tank No. 1 by air with an excess pressure of 0.65 kg. per cm sq. Each tank has a capacity of 80 liters.

The supply tank is tank No. 2, located at the center of gravity of the aircraft.

Fuselage and wing tanks are sealed compartment tanks that are structural elements of the fuselage and wing of an aircraft.

A protector is installed on the side surfaces of tanks No. 1 and No. 2, separated from the air channel by a layout gap, and on the lower surfaces of the tank in the center section and tank No. 1, which significantly reduces fuel losses due to breakdowns of the tank walls and reduces the possibility of a fire. Double-layer design elements have a thickness of up to 20 mm.

To ensure explosion safety of the fuel tanks of the fuselage, wing, center section and outboard tanks, their internal volumes are filled with porous filler - polyurethane foam. To ensure fire protection, adjacent compartments located next to the first and second fuel channels and tanks are also filled with polyurethane foam.

Polyurethane foam liners are placed into tanks through installation hatches.

Polyurethane foam liners are pinned into outboard fuel tanks when the tank is disassembled along the butt frames. Fastening of the liners in the tank is carried out by tensioning them using tapes, and also due to the fact that the liners are cut along the outer contour of the tanks with an allowance.

The drainage and pressurization system provides excess pressure in the wing and fuselage tanks in all flight modes; for this purpose, all tanks are connected by drainage pipelines into which air is supplied from the high-speed pressure intake and the pressurization system.

Filling tanks with fuel is carried out in two ways: - open centralized; - open through the filler necks of each container. With the open centralized method, refueling of the fuselage and wing tanks is carried out through the filling neck of tank No. 1.

The sequence of fuel depletion from the tanks is determined by the requirement to maintain the aircraft alignment within specified limits in all flight modes. Since tank No. 2 is a consumable tank, it is used last and is kept full at all engine operating modes by pumping fuel from the fuselage and wing tanks. Fuel supply to the engines is provided in three ways:

• - booster pump from tank No. 2 in all flight modes in the absence of zero and negative overloads;
• - displacement from the storage tank under the action of zero and negative overloads;
• - by gravity through check valves in case of pump failure. Fuel is supplied to the pumps, installed one on each engine, from the supply tank by a booster pump.

The capacity of the battery tank ensures that the engines operate at zero or negative overloads for 15 seconds. During normal operation of the fuel system, the accumulator tank is completely filled with fuel.

Fuel is pumped from the wing tanks to the supply tanks by jet pumps.

Fuel is produced from external fuel tanks under the influence of boost pressure. Outboard fuel tanks are produced first. Structurally suspended fuel tank made in the form of a cylindrical shell, reinforced with frames welded to it by electric welding. To improve transportability and storage conditions, the outboard tank is made of detachable parts, consisting of three parts: bow, middle and tail, connected at the joint with bolts. Tightness is ensured by installing butt rings along the connectors. A stabilizer consisting of two horizontally located consoles is installed on the tail part of the outboard fuel tank. The middle part of the outboard fuel tank is the power part, on it are located the suspension units of the tank to the beam holder; A pipe is installed in the middle part of the suspended tank, which serves to extract fuel from the tank.

The fuel system is designed to carry fuel on the aircraft and deliver it to the engines and auxiliary power unit under all possible operating conditions of the aircraft.

The purpose of the fuel system is to ensure the supply of fuel to the engines in all possible flight modes for a given aircraft (altitude, speed and overload) in the required quantity and with the required pressure. In addition, by pumping fuel (forward and backward), you can change the alignment of the aircraft.

The BOEING 767 fuel system includes; three fuel tanks, two expansion tanks, a ventilation system, a fuel supply system for the engines and APU, a filling and draining system, an emergency fuel dump system, and a fuel quantity indication system.

Fuel tanks.

Fuel tanks are located between ribs 3 and 31 of both wings. Tanks of caisson design. Dry cavities are located in the leading edge of the wing above the pylon to prevent fuel leakage. Ribs 5 and 18 are sealed and have valves at the bottom of the baffle. These baffles are necessary to distribute fuel evenly throughout the fuel tanks and prevent vapor buildup.

Fig2.1..

The main tanks can be heated using slats heating. The fuel tanks have 59 oval access holes located at the bottom of the wing. There are drain valves at the bottom of the tanks to drain sludge.

Rice. 2.2.

The central tank is located in the center section, between ribs 3. The central tank is divided into three parts - left, right, and central. Like the wing tanks, the center tank also has a dry compartment located at the front of the tank. The three sections are connected to each other by pipes for the flow of liquid and vapor. The central tank has two booster pumps installed in the left and right sections. Sludge drain valves are installed at the bottom of each tank.

The power supply system supplies pressurized fuel to the engines and auxiliary power unit. The power system is divided into two subsystems. Subsystems operate independently of each other. They have loop valves for uniform production of fuel from tanks and pumping. Typically, each engine is powered by its own tank. If the loopback valve is open, then each engine will be powered from either fuel tank. Stop valve controls the flow of fuel to the engine.

Fig.2.3.

The pressure in the fuel system is provided by two 115V electric booster pumps. 400Hz. 3 phases installed in one housing. The pumps are located one in each wing tank. Two 115V booster pumps. 400Hz. 3 phases, installed in the central tank, left and right sections. Pump capacity is 13,600 kilograms per hour, minimum pressure is 15psi. The booster pumps of the central tank feed the left and right subsystems, respectively, and create a pressure higher than the pressure of the booster pumps of the wing tanks. This allows the central tank to produce fuel first.

Automatic jet pumps, installed two in each tank, designed to collect various contaminants and water from the bottom of the tanks. They operate due to the vacuum created by booster pumps.

Auxiliary Power Unit power system.

The left side of the center tank houses the components of the Auxiliary Power Unit power system. With the exception of the pipe casing and receiver.

The components include;

Booster pump direct current 28V.

Stop valve,

Pipeline,

isolation valve,

Pipe casing.

The booster pump consists of a housing, a receiver, an electric motor, a pressure sensor, a pressure valve, a temperature valve, a discharge valve, a check valve,

The check valve prevents fuel from flowing in the opposite direction. The pressure valve regulates the pump pressure. Fuel passing through the pump cools it and lubricates the moving parts. The electric motor is located on the outside of the tank. The engine rotates at 6600 rpm and produces 18 psi. Capacity 3.1 gallons per minute. The temperature fuse prevents the motor from overheating. The fuse turns off the pump if the temperature exceeds 3508F ±148F (1778C ±88C). The isolation valve operates on 28V DC. Installed in the central fuel supply line. Prevents elements of the fuel system of the auxiliary unit from destruction.

Rice. 2.4. APU power system

A fuel tank is a container in which liquid fuel is stored and is located directly on board the aircraft. Fuel wires go from the fuel tanks to the power plant, which supplies it with fuel. Also on board the aircraft can be placed tanks to supply fuel to heating systems.

Turboprop and turbojet aircraft engines use aviation kerosene with additional additives in their operation. Light-engine aircraft equipped with piston power plants use high-octane gasoline as fuel.

Fuel tank in an airplane wing

In modern aircraft construction, caisson tanks are used; they look like sealed cavities. They are mainly installed in the wings, stabilizer and fin. These are soft tanks made from rubber materials, this allows you to maintain their integrity during overloads and impacts. In addition, such material is very reliable and effectively occupies the allotted space.

Sometimes they use compartment tanks that act as fuel tank, and the role of the power element. To prevent fuel from spilling from the caisson tanks, fighter aircraft use a sponge filler like foam rubber.

Large airliners, which are designed for long-distance flights, have several fuel tanks, which are additionally equipped with pumps. All fuel tanks are connected to each other by a system of fuel wires that allow the use of fuel from any tank or its transfer. Transferring fuel from one tank to another is possible thanks to more efficient alignment aircraft. Fuel is pumped from consumable tanks to spare tanks according to the developed in-flight fuel consumption program.

Fuel tanks made from standard aluminum cans

It should be noted that the process of filling fuel into the aircraft tanks also occurs in accordance with the alignment plan. Fuel is supplied to the tanks of the device under pressure from a special tanker through the neck, after which it is distributed between the tanks.

Every fuel tank on an airplane has what is called a drain port through which all the fuel can be drained. After each refueling, this neck is opened, which allows condensate or water that has settled at the bottom of the tank to be drained. Naturally, there should be no impurities in the tank, otherwise this may cause engine failure and an accident.

Airplanes also have emergency fuel dump systems in the air. This system necessary when performing emergency landings immediately after takeoff, because permissible weight The landing of the aircraft is significantly less than the take-off weight.

Fuel tank in side member

Combat aircraft that need to carry out combat operations at a great distance from the base can be equipped with additional drop tanks. They are streamlined to improve overall aerodynamics and are suspended from the fuselage or wing of the aircraft. After all the fuel has been used up, they are dumped. Also, similar devices are used to ferry aircraft to other airfields; they are usually installed in the middle of the hull.

Outboard fuel tanks

Fuel tank safety

Combat aircraft and some passenger cars use neutral gas to fill their tanks, which is supplied as fuel is consumed. The gas used is carbon dioxide or nitrogen. This helps prevent a fire on board or a fuel tank explosion due to mechanical damage. A similar scheme for filling a fuel tank with gases was used back in World War II, only cooled exhaust from the engine manifold was used as gas.

(a) Each fuel system must be designed and constructed to deliver fuel at the flow rate and pressure specified for normal operation of the main and auxiliary engines under all expected operating conditions, including all maneuvers for which certification is sought and during which the operation of the main and auxiliary engines is permitted.

(b) Each fuel system must be configured so that air entering the system cannot cause:

(1) To loss of power for more than 20 s for piston engines.

(2) To failure of combustion in a gas turbine engine.

(c) Each turbine engine fuel system must be capable of continuous operation over the full range of flow rates and pressures of fuel containing the maximum amount of dissolved and free water possible under expected operating conditions and cooled to the most critical icing temperature that may be encountered in the operating conditions. operation.

(d) Each turbine engine airplane fuel system must comply with the applicable requirements of Part 34 of the Aviation Regulations for the release of fuel from drainage systems.

(a) Normal operation of the fuel system under all expected operating conditions shall be demonstrated by analysis and such tests as are deemed necessary by the Competent Authority. Tests, if required, must be performed on the aircraft fuel system or on a test bench that simulates the performance characteristics of the section of the fuel system being tested.

(b) The potential failure of any heat exchanger using fuel as one of the working fluids shall not cause hazardous consequences.

Each fuel system must satisfy the requirements of 25.903(b) by:

(a) Supplying fuel to each engine in a system independent of any portion of the system providing fuel to another engine; or

(b) Any other acceptable method.

The fuel system must be designed and located to prevent ignition of fuel vapors within the system as a result of:

(a) A direct lightning strike to those areas of the aircraft that have a high probability of being struck by lightning.

(b) Sliding lightning strikes into areas where the probability of gliding strikes is high.

(c) Corona discharge and lightning current flow in the area of ​​fuel drain outlets.

(a) Each fuel system must be capable of delivering fuel at a rate of at least 100% of the fuel flow required by the engine under each expected operating condition and maneuver. The following should be shown:

(1) Fuel must be supplied to each engine at the pressure and temperature within the limits specified on the engine type certificate.

(2) When tested, the amount of fuel in the tank in question must not exceed the amount of fuel remaining for that tank as required by CS 25.959, plus the amount of fuel required to demonstrate compliance with this section.

(3) Each main fuel pump must provide each airplane mode and attitude for which compliance with this paragraph is demonstrated, and the associated emergency pump must be capable of replacing the primary pump so used.

(4) If a flow meter is installed, fuel must flow freely through the flow meter if it is blocked, or through the bypass passages.

(b) If the engine can be supplied with fuel from more than one tank, the fuel system must:

(1) For each reciprocating engine, ensure that full fuel pressure is restored to that engine within 20 seconds of switching to any other fuel tank containing the fuel in use if it becomes apparent that the engine malfunction is caused by insufficient fuel in the tank. , from which the engine was previously powered; And

(2) For each gas turbine engine, in addition to the appropriate manual switching, a device must be provided to prevent interruption of the fuel supply to that engine without crew intervention in the event that the fuel in any tank supplying that engine is exhausted during normal operation, and in any The other tank, which normally supplies fuel only to that engine, contains the usable fuel supply.

(a*) Fuel delivery must be demonstrated under the airplane's worst-case fuel supply conditions, with respect to flight altitude, airplane attitude, and other conditions, when:

(1) Inoperative tank booster pumps.

(2) Supplying fuel to two engines from one tank with the ring valve open.

If in flight it is possible to transfer fuel from one tank to another, then the tank drainage system and fuel transfer system must not allow damage to the tank structure in the event of overfilling.

For each fuel tank with its associated fuel system components, the unused fuel balance must be set to no less than the amount at which the first sign of engine malfunction is observed under the most unfavorable fuel supply conditions in all intended operating conditions and flight maneuvers in which fuel is withdrawn from of this tank. There is no need to consider fuel system component failures.

25.961. Fuel system operation at high temperatures

(a) The airplane fuel system must function satisfactorily in hot climates. To do this, it must be demonstrated that the fuel system from the tank to each engine has such a pressure under all specified operating conditions as to prevent vaporization, or this must be shown in the climb from the level of the aerodrome selected by the Applicant to the maximum altitude specified operating restrictions 25.1527.

If a climb test is selected, there should be no evidence of vapor lock or other system malfunction when performing a climb test under the following conditions:

(1) For aircraft with piston engines All engines must operate at maximum continuous power, except that at altitudes from 300 m below critical altitude up to and including critical altitude, takeoff power must be used.

The operating time in take-off mode should not be less than the permissible duration of take-off mode.

(2) For turbine-powered airplanes, the engines must be operated at takeoff power for the time selected to demonstrate the takeoff climb path and at maximum continuous power for the remainder of the climb.

(3) The mass of the aircraft must be the sum of the mass of the aircraft with full fuel tanks and the minimum number of crew members and the mass of ballast necessary to maintain the center of gravity within acceptable limits.

(4) The rate of climb must not exceed:

(i) for piston engine airplanes, the maximum airspeed specified for climb from takeoff to maximum operating altitude in the following airplane configuration:

(A) landing gear retracted;

(B) flaps in the most favorable position;

(C) hood flaps (or other engine cooling controls) in a position that provides adequate cooling during hot day conditions;

(D) engines are operated within maximum continuous power limits;

(E) the weight corresponds to the maximum take-off weight; And

(ii) for turbine-powered airplanes, the maximum airspeed specified for the climb from takeoff to maximum operating altitude.

(5) The fuel temperature before takeoff must be at least 45°C. In addition, the fuel must have a saturated vapor pressure that is the maximum possible for the grades on which the aircraft can be operated.

(b) The tests specified in paragraph (a) of this section may be conducted in flight or on the ground under conditions closely simulating flight conditions. If flight tests are carried out in cold weather which may interfere with proper testing, fuel tank surfaces, piping, and other fuel system components exposed to cold air must be insulated to simulate (to the extent possible) hot weather flight.

(a) Each fuel tank must be able to withstand, without damage or loss of specified integrity, the vibration, inertial forces, mass of fuel, and structural loads to which it may be subjected on the airplane during operation.

(b) Flexible fuel tank linings must be of an approved type or must be demonstrated to be fit for purpose.

(c) Fuel compartment tanks (caisson tanks) must have provisions for internal inspection and repair.

(d) Fuel tanks located in the fuselage must not rupture or become leak-tight when subjected to the inertial forces specified in CS 25.561 for an emergency landing. In addition, these tanks must be protected in such a way that friction of the tanks on the ground is impossible.

(e) Fuel tank hatch covers must meet the following criteria to prevent the leakage of hazardous quantities of fuel:

(1) It must be shown by analysis or testing that all covers located in an area in which impact is expected, based on experience or analysis, to be minimally susceptible to penetration or deformation by tire pieces, low energy engine debris, or other similar debris. .

(2) All manhole covers must be fire resistant.

(f) For pressurized fuel tanks, safe means must be provided to prevent excessive differential pressure between the inside and outside of the tank.

(a) When testing fuel tanks, it must be demonstrated that tanks installed on the airplane can withstand, without damage or leakage, the most critical pressures under the conditions specified in paragraphs (a)(1) and (a)(2) of this section. In addition, the surfaces of tanks exposed to the most critical pressures encountered under the conditions specified in paragraphs (a)(3) and (a)(4) of this section must be demonstrated to withstand the following pressures:

(1) Internal pressure 0.25 kg/cm2.

(2) 125% of the maximum air pressure created in the tank by the velocity head.

(3) Hydraulic pressures arising during maximum overloads and aircraft maneuvers with full tanks.

(4) Hydraulic pressures occurring under the most unfavorable combination of aircraft roll and fuel load.

(b) Each metal tank with large unsupported or unreinforced flat surfaces whose damage or deformation could cause fuel to leak must withstand the following tests (or equivalent) without leakage or excessive deformation of the tank walls:

(1) Each fully assembled tank, together with its mountings, must be subjected to vibration testing in a configuration that simulates the actual installation on the aircraft.

(2) Except as provided in paragraph (b)(4) of this section, a tank assembly filled 2/3 full with water or any other suitable test liquid must be subjected to vibration testing for 25 hours at a vibration amplitude not exceeding less than 0.8 mm, unless another sufficiently justified amplitude is indicated.

(3) The test vibration frequency shall be as follows:

(i) if there is no critical tank vibration frequency within the normal operating speed range of the engine rotors, the test vibration frequency shall be 2000 vibrations per minute (33.3 Hz);

(ii) if there is only one critical tank oscillation frequency within the normal operating range of engine speeds, then the tests shall be carried out at that frequency;

(iii) If more than one frequency is found to be critical in the normal operating range of engine rotor speeds, the tests shall be carried out at the most critical frequency.

(4) When performing tests in accordance with paragraphs (b)(3)(ii) and (iii) of this section, the test duration must be modified to obtain the same number of vibration cycles as during 25 hours of testing at the frequency specified in point

(b)(3)(i) of this paragraph.

(5) During testing, the tank assembly must be subjected to vibration testing for 25 hours at a frequency of 16 to 20 complete cycles per minute at an angle of 15° on either side of the horizontal position (30° total) about the most critical axis.

If movement about more than one axis is critical, then the tank must swing about each critical axis for 12.5 hours.

(c) Nonmetallic tanks must withstand the tests specified in paragraph (b)(5) of this section with fuel at 45°C unless there is sufficient experience with a similar tank in a similar installation. During these tests, this type of tank must be mounted on supports simulating its installation in an aircraft.

(d) For pressurized fuel tanks, it must be shown by calculation or testing that the fuel tanks can withstand the maximum pressure that may be experienced on the ground or in flight.

(a) The support of each fuel tank must not allow loads from the weight of the fuel to concentrate on the unsupported surfaces of the tanks. In addition, the following provisions must be taken into account:

(1) Gaskets must be installed between the tank and its supporting structure to prevent friction.

(2) Gaskets must be made from non-absorbent materials or from materials suitably treated to prevent the absorption of liquids.

(3) When flexible tanks are used, their shells must be secured in such a way that they are not subject to hydraulic loads.

(4) Each interior surface of the tank installation compartment must be smooth and free of protrusions that could cause damage to the shell unless:

(i) measures are taken to protect the enclosure at such points; or

(ii) the design of the shell itself provides such protection.

(b) Cavities adjacent to tank surfaces must be ventilated to prevent the accumulation of vapors in the event of a minor leak. If the tank is in a pressurized compartment, ventilation can be achieved using adequately sized drain holes to prevent overpressure as flight altitude changes.

(c) The location of each tank must meet the requirements of 25.1185(a).

(d) No portion of the engine nacelle skin immediately aft of the main air outlet of the engine compartment shall serve as a tank compartment wall.

(e) Each fuel tank must be isolated from personnel and passenger compartments by means of a design that does not permit the passage of vapors or fuel.

Each fuel tank must have an expansion space of at least 2% of the tank capacity. It must be impossible for this space to be unintentionally filled in the normal parking position. For pressurized fueling systems, compliance with this paragraph may be demonstrated by the presence of devices used to establish compliance with 25.979(b).

25.971. Fuel tank sump

(a) Each fuel tank must have a sump whose operating capacity when parked is not less than 0.1% of the tank's capacity or 0.3 L, whichever is greater, unless specified operating limitations guarantee that during operation the accumulation of condensate will not exceed the capacity of the sump.

(b) Each fuel tank must be designed to drain hazardous quantities of condensate from any part of the tank into a sump when the airplane is parked.

(c) Each fuel tank sump must have an accessible drainage device that:

(1) Provides drainage of sludge onto the ground.

(2) Prevents discharged fuel from reaching other parts of the airplane; And

(3) Has a manual or automatic device to securely lock in the closed position.

Each fuel tank filler neck must be designed to prevent fuel from entering any part of the airplane other than the tank itself. Besides:

(a) [Reserved].

(b) Each recessed fuel tank filler neck in which a significant amount of fuel may accumulate must be equipped with a drain device to prevent discharged fuel from reaching other parts of the airplane.

(c) Each fuel filler cap must provide a tight seal to prevent fuel leakage.

(d) Each refueling point must have metallized means for electrical connection to ground-based refueling equipment.

(a) Fuel tank drainage. Each fuel tank must be exposed to the atmosphere through the top of the expansion space to ensure effective drainage under all normal flight conditions. Besides:

(1) Each drainage hole must be located so as not to become clogged or clogged with ice.

(2) The drainage design must not allow fuel to siphon under normal operating conditions.

(3) Bandwidth drainage system and its pressure level must be sufficient to withstand acceptable pressure differences inside and outside the tank when:

(i) normal flight conditions;

(ii) maximum speed climb and descent; And

(iii) filling and draining of fuel.

(4) Air cavities of tanks with interconnected fuel outlet channels must also communicate with each other.

(5) The drainage system must not have any places where moisture can accumulate when the aircraft is on the ground or in level flight, otherwise it must be possible to drain it.

(6) Drains and discharge devices shall not terminate at:

(i) where fuel escaping from the drain hole could create a fire hazard; or

(ii) from where fuel vapors can enter the cabins of personnel and passengers.

(b) Carburetor drain. Each carburetor with a vapor vent fitting must have a line to vent the vapors back to one of the fuel tanks. Besides:

(1) Each drainage system must be done so that the drainage is not blocked by ice.

(2) If there is more than one fuel tank and fuel from the tanks must be discharged in a specific sequence, each vapor return line must be connected to the tank from which fuel is consumed during takeoff and landing.

25.977. Fuel intake from the tank

(a) The fuel intake from the tank or the inlet to the tank pump must have a protective mesh - a filter. The filter mesh should:

(1) For aircraft with piston engines, have 3 - 6 cells per 1 cm; And

(2) Prevent the passage of particles that could limit fuel flow or damage any component of the aircraft fuel system with gas turbine engines.

(b) [Reserved].

(c) The flow area of ​​each filter on the intake or tank pump inlet must be at least 5 times the flow area of ​​the fuel supply pipe from the tank to the engine.

(d) The diameter of each filter must be no less than the diameter of the fuel tank intake.

(e) Each filter (filter element) must be accessible for inspection and cleaning.

Pressurized fuel tank filling systems include the following:

(a) Each fuel system piping connection must have a means to prevent hazardous quantities of fuel from leaking from the system in the event of intake valve failure.

(b) An automatic closing means must be provided to prevent each tank from being filled with more fuel than is specified for that tank. These funds should:

(1) Allow for proper closure to be checked before each tank is filled with fuel; And

(2) At each fueling location, provide an indication of failure of the closing means to stop the fuel supply at the maximum fuel quantity specified for that tank.

(c) There must be a means to prevent damage to the fuel system in the event of failure of the automatic shut-off means prescribed in paragraph (b) of this section.

(d) The airplane pressurized fueling system (excluding fuel tanks and tank drains) must withstand a load that is twice that of the maximum pressures, including pulsations that may occur during refueling. The maximum pulsation pressure for any combination of accidental or intentional closure of fuel valves must be determined.

(e) The aircraft fuel bleed system (excluding fuel tanks and fuel tank drains) must be capable of supporting a load that is twice that of the maximum allowable bleed pressure (positive or negative) at the aircraft fuel connection fitting.

(a) The highest temperature that is a specified margin below the minimum expected autoignition temperature of the fuel in the airplane tanks must be determined.

(b) The temperature at any point within each fuel tank where fuel ignition is possible must not exceed the temperature determined in accordance with paragraph (a) of this section. This must be demonstrated under all possible operating conditions, failures and malfunctions of any element that could lead to an increase in temperature inside the tank.

Imagine that, sitting in the center of the Tu-154M cabin, there is at least 3 tons, or even 8 tons, of kerosene below you. It looks something like this:

Can you imagine 8 tons of kerosene? I agree, it's difficult. I assure you that in the wings of the aircraft there is much more room under the passenger seats than in the center section. Moreover, there is fuel on the plane Always, drains completely only in cases of special maintenance. On the Tu-154M with installed engines It is forbidden to drain all the fuel at all, otherwise it will sit on its tail. This happens, photo below ;).

Shall we refuel?

The story in this article will be about fuel on an airplane. Very much and detailed ;).

The cost of kerosene today varies from 17 to 35 thousand rubles per ton. A simple Google search gives the following sites:
http://www.riccom.ru/sale_market_r_np_12.htm
http://distoplivo.ru/prais/
You'll figure it out without me =).

At Pulkovo we fuel two types of aviation kerosene, which are considered interchangeable and can be mixed in any proportions: TS-1 and RT. Abroad they use Jet Fuel A, Jet Fuel A-1 (freezing point -47°C) and something else. You can also pour and mix in any proportions. The main thing is what is written in the aircraft documentation. If the crew encounters some unfamiliar brand, they need to consult with the base.

In winter, an additive, liquid “I”, is added to kerosene so that it does not freeze at higher temperatures. low temperatures(exactly -60°C). They add very little, 0.05% of the total. More liquid "I" Prevents thickening and waxing diesel fuel at low temperatures. prevents icing fuel filter. Promotes complete combustion of fuel. Removes water from the fuel system. Increases torque. Provides easy engine starting in cold weather.
http://www.masla.su/?Produkciya:Tehnicheskie_%0Azhidkosti

They say that pure kerosene can be drunk, and it helps cure diseases (blood, gastrointestinal tract, genitourinary system). BUT! You can’t drink kerosene with liquid “I”!. I don’t know why or how, but the only thing I ask is, don’t try to ask your familiar technicians or pilots to pour a jar of kerosene in winter, spring or fall. It may contain this dangerous additive. I don’t know what exactly is dangerous, but it’s better not to risk it.

So, the fuel tanks are mostly caisson tanks. This means that kerosene is simply poured into the wing cavity, there are no special containers, everything is located in a sealed compartment of the structure.

Let's see where the fuel is stored and how it is used on board? On different aircraft, the tanks are located differently, but in general the trend is the same - three tanks (the central one, which is also consumable, from which fuel is taken to the engines, and the wing ones).

Let's take a look at the A-320:

Boeing 737 Classic (the most popular type of 737 in Russia, produced in the 90s).

Well, now the highlight of the Tu-154M issue:

The "fifty kopeck" tanks are located quite cleverly. The supply tank is called: “First”, and is located in the middle, at the back. The fourth tank is filled first and is very often used to maintain alignment.

What is a supply tank? This is a fuel tank from which fuel goes directly to consumers - engines. From all other tanks, fuel is pumped into the supply tank and only then sent to the engines.

On some aircraft (for example, the A330, in my opinion, it is also allowed to be used on the latest modifications of the Tu-204) there is an additional tail fuel tank to adjust the alignment of the aircraft in flight. They can be located both in the fin (Tu-204) and in the stabilizers (A330).

Any tank must communicate with the atmosphere, in other words, be “leaky.” For what? Try drinking Duchess (Coca-Cola, whatever you like) from a glass bottle without lifting your lips (so that air does not pass inside). You won't last long. The pressure inside the bottle will drop sharply, and you will not be able to drink.

Therefore, instead of fuel leaving, air should enter the tank in its place from outside the aircraft. For this purpose, it is common practice to create drainage tanks on foreign aircraft. They are located at the end of the wing. And their exit into the atmosphere looks like this:

Such a tricky entrance (often used) so that the incoming air flow presses the kerosene in the tanks.

In the case of the Tu-154M there are no drainage tanks. They are connected directly to the atmosphere through cunning pipelines encircling the fuselage. The pipes first go up, then go around the contour of the fuselage and have an outlet at the bottom. This is done so that when the aircraft tilts (rolls), fuel does not spill out. The picture is complex, I recommend enlarging it.

I already wrote once in a magazine about refueling an airplane before a flight. I'll try not to repeat myself.

So, before refueling the plane, it is necessary to drain the fuel sediment to check for the presence of water in the tanks of the plane. It is precisely intended for draining sediment into it in the field.

The drainage of sludge by a technician is often controlled by a flight engineer (in the photo the drainage of sludge from an IL-76):

Then a fuel tanker arrives.

The technician must tell the tanker driver how much fuel needs to be filled, so while the tanker connects the hose (sometimes he connects two at once to speed up the process), the technician goes to look at the remaining fuel:

The remainder is determined by the aircraft's instruments and is also recorded in the logbook. As you can imagine, these data sometimes do not add up. The temperature outside has changed - the fuel density has changed, the instrument readings have changed. The thing is that on an airplane it is measured in kilograms, and in a tanker in liters. The arrow division price is 1 ton. Depending on the voltage in the aircraft's electrical network, the needle readings may fluctuate. The photo shows the control panel of the Tu-154M fuel system ( pointer indicators show the amount of fuel in each group of tanks):

A bunch of lights and switches help control the in-flight kerosene flow from the various tanks. The lights indicate whether the pump for each tank is currently on or off. In general, it took me a long time to get used to this system; at first it was difficult to figure it out =). At the beginning of the operation of the Tu-154 aircraft, there was a disaster when the engines turned off during flight due to the fact that the fuel tank ran out, and the flight engineer forgot to turn on the pumping from others to the supply tank. The engines stopped, the plane fell =(. After this, changes were made and when a certain level in the supply tank drops, fuel begins to flow from others automatically.

If the fuel gauge readings and the entries in the logbook match at least +/- 200 kg, then refueling can begin. The main thing at this stage is not to forget to check the refueling driver so that he connects his car to the aircraft with a grounding cable (the electrical potentials must be equalized through it, and not through the refueling hose, because this can cause a strong spark of static electricity). And also another grounding cable must be connected from the machine to the grounding point on the apron (usually a piece of pipe buried in the ground).

Open the filler neck (usually in the wing):

And connect the hose:

Or hoses (photo Boeing-767):

The neck differs from a car neck in that there are check valves there. You don't have to worry about fuel spilling out. The whole process is “dry”, the valves open only when pressure is applied:

Fortunately, both on the Tu-154 and on foreign aircraft, this connection is unified everywhere and no adapters are needed. The spring presses the plate so that the fuel does not flow back.

The fuel meter at the gas station is in liters. Therefore, before refueling, we need to calculate how many liters we need. The density of the fuel depends on the ambient temperature and varies from 0.779 to 0.791 (the numbers may not be accurate, I forgot everything) and is written on the control card, which confirms the condition of the fuel. The last check must have been completed no more than six hours ago, otherwise fuel cannot be refueled. All required signatures and verification hours are indicated on the ticket. If everything is in order, we count the liters and tell them to the gas station attendant.

But before you say “let’s go,” you need to perform one more procedure: checking the fuel in the fuel tank for the presence of water. We kindly ask the refiller to provide a sample in a jar. If no water is detected (in my lifetime I have never seen water in the TZ), then you can refuel.

We open the taps of the tanks we need (where we will refuel at the moment). All is ready.

Go!

Kerosene rushes into the aircraft tanks at great speed. This all happens before the passengers arrive. In Russia there are special procedures for refueling an aircraft with passengers, but everyone tries not to do this. Why take the risk?

Of course, the tanks have overpressure protection to prevent them from bursting when refueling. The protection is a small valve that opens when the pressure is exceeded and releases the air. A simple and common mechanism.

You can control refueling on foreign aircraft right next to the hose connection point, and you can also control the taps there (to select the filling of the tanks we need):

The A330 refueling panel is located on the fuselage at the rear:

A320x family:

Sometimes the panel is located directly on the wing, sometimes on the fuselage, at the request of the aircraft customer.

On the Tu-154M, you can only control the cranes from the outside, while all the indications are inside, in the cockpit. Only. This always irritated me; I had to run from the cockpit under the wing and back.

You can, of course, use measuring rulers from the outside, but their minimum value is sometimes not sufficient to show the desired level. Pulled straight out of the wing:

It turns out that a magnet floats in the tank, which at the right moment picks up the ruler and does not allow it to fall below the kerosene level. This way you can determine how full the tank is without any electronics. To be honest, I have never used this method. It was always safer for me to look in the cockpit.

Is it possible to refill the tank, fill too much? It is forbidden. The automation will close the taps and prevent you from filling the plane with more than is allowed. But automation tends to fail. The mechanics work for this case:

There are valves in the wing that at a certain point begin to drain excess kerosene directly onto the ground. They open during refueling from the pressure of incoming kerosene:

Aviation has everything covered ;).

In the cockpit, pilots always have the opportunity to view instrument readings about the fuel level. For example in 737:

Pump control in flight:

On Airbuses everything is simpler; fuel information is generally displayed on one of the pages of the multifunction display:

Compare with the fuel system control panel 154 =). That's where the power is =).

Actually I'm kidding. Of course, this is why a flight engineer does not fly on new foreign aircraft as part of the crew. It's simply not needed there. The plane does everything itself.

Especially on larger aircraft, refueling must be carefully monitored to ensure that one wing does not end up with much more fuel being pumped into it than the other. This is called a "fork". You understand that if there is several tons more fuel in one wing, this can not only affect the pilot’s comfort (the plane will pull to the side), but also flight safety.

The worst part is that the situation is very difficult to correct. If you end up with a large fork, you need to drain the excess fuel and refill it in the other wing. And this is at least an hour (if everything coincides successfully and the necessary ground equipment is at hand, which never happens) of time. Accordingly there is a delay. And for delays due to personal fault, the technical staff will not be patted on the back... Drained fuel is no longer refilled into airplanes. It goes to airfield equipment, tractors and something else.

So, the refueling is complete. The TK driver issues a request, which states the liters of kerosene on the meter. This is a very crucial moment when all the calculations need to come together, otherwise there will be problems. We convert the liters in the requirement into kilograms and add them to the balance before refueling. If this value is equal to the one required for the flight, then everything is fine, we put the necessary markings (and as you thought, everyone answers with their head, especially in the matter of fuel).

How much kerosene does a plane take? I will not give specific numbers for flights, because I have already begun to forget them. I can say that the Tu-154M usually filled 25-35 tons. B-737-500 no more than 15 tons. A320 approximately 15-25 tons. These data are given for approximately the same routes. It’s better to ask the pilots how fuel is calculated; I’ve never done this and wasn’t particularly interested. I know that the refueling includes an aeronautical reserve that allows the aircraft to fly for several more hours and is calculated differently for each type.

15 minutes after refueling, you need to drain the fuel sediment from the aircraft again. During this time, possible water should have sunk to the bottom of the tanks, where we check it through the drain points:

We bring the jar and check the condition of the kerosene. Everything is fine?

And now I’d better say a few words about how it is consumed in flight. So, fuel is supplied from the supply tank by pumps. Typically these pumps are centrifugal:

This type of pump is simpler than others and allows you to work at Idling, even if there is nowhere to pump fuel (the fuel supply valves to the engines are closed). There are transfer and booster pumps. Some help move fuel through the tanks, while others send it to the engine power supply line.

But to start the engine, it is not enough to turn on the pumps. It is also necessary to open the “fire valves” (as they are called on domestic equipment, because they are closed first in the event of an engine fire). When the taps are opened, fuel enters the engine, where it is filtered and heated (usually there is a radiator that cools the oil circulating in the engine and at the same time heats the fuel) and is supplied to the injectors. This is already the motor part, so we will talk about it in detail in the following posts. I can only say that there are several degrees of filtration and even if all the filters become clogged, the fuel will bypass. The main thing is to maintain smooth operation so that the plane can be landed.

Finally, I would like to show you what happens when mistakes are made with refueling on the Tu-154:

Photos from the Internet

Yes, yes, the plane can just land on its tail!

Photos from the Internet

In fact, this is the worst dream of every Tu-154 technician and flight engineer. The tail of the plane is very heavy. Passengers should preferably exit in order - the second cabin, the first cabin, especially if there is little fuel left in the fourth tank.

Photos from the Internet

They recently wrote about how fuel is stored at the airport here: http://community.livejournal.com/sky_hope/180444.html#cutid1
I highly recommend watching it.