直升机飞行手册 Helicopter Flying Handbook

时间：2014-11-09 12:30来源：FAA 作者：直升机翻译 点击：次

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Fuel.quantityFue
LOW.FUEL.LEVEL.MIX.WARNING.LIGHT.PULL.LEAN.
FUEL.SHOT.OFF.
Primer.nozzle.at.cylinder
Primer
Fuel.strainer
Throttle Carburetor
Figure 4-20. A typical gravity feed fuel system, in a helicopter with a reciprocating engine, contains the components shown here.
The fuel travels from the fuel tank through a shut-off valve, which provides a means to completely stop fuel flow to the engine in the event of an emergency or fire. The shut-off valve remains in the open position for all normal operations.
Most non-gravity feed fuel systems contain both an electric pump and a mechanical engine driven pump. The electrical pump is used to maintain positive fuel pressure to the engine pump and may also serve as a backup in the event of mechanical pump failure. The electrical pump is controlled by a switch in the cockpit. The engine driven pump is the primary pump that supplies fuel to the engine and operates any time the engine is running. A fuel filter removes moisture and other sediment from the fuel before it reaches the engine. These contaminants are usually heavier than fuel and settle to the bottom of the fuel filter sump where they can be drained out by the pilot.
Some fuel systems contain a small hand-operated pump called a primer. A primer allows fuel to be pumped directly into the intake port of the cylinders prior to engine start. The primer is useful in cold weather when fuel in the carburetor is difficult to vaporize.
A fuel quantity gauge located on the pilot’s instrument panel shows the amount of fuel measured by a sensing unit inside the tank. Most fuel gauges will indicate in gallons or pounds, and must be accurate only when empty.
It is worth noting that in accordance with Title 14 of the Code of Federal Regulations (14 CFR) section 27.1337(b)(1), fuel quantity indicators “must be calibrated to read ‘zero’ during level flight when the quantity of fuel remaining in the tank is equal to the unusable fuel supply.” Therefore, it is of the utmost importance that the pilot or operator determines an accurate means of verifying partial or full fuel loads. It is always a good habit, if possible, to visually verify the fuel on board prior to flight and determine if adequate fuel is present for the duration of the flight.
Additionally, 14 CFR section 27.1305(l)(1) requires newer helicopters to have warning systems “provide a warning to the flight crew when approximately 10 minutes of usable fuel remains in the tank.” Caution should be used to eliminate unnecessary or erratic maneuvering that could cause interruption of fuel flow to the engine. Although these systems must be calibrated, never assume the entire amount is available. Many pilots have not reached their destinations due to poor fuel planning or faulty fuel indications.
Engine Fuel Control System
Regardless of the device, the reciprocating engine and the turbine engine both use the ignition and combustion of the fuel/air mix to provide the source of their power. Engine fuel control systems utilize several components to meter the proper amount of fuel necessary to produce the required amount of power. The fuel control system in concert with the air induction components combine the proper amount of fuel and air to be ignited in the combustion chamber. Refer to the Pilot’s Handbook of Aeronautical Knowledge for a detailed explanation and illustration.
Carburetor Ice
The effect of fuel vaporization and decreasing air pressure in the venturi causes a sharp drop in temperature in the carburetor. If the air is moist, the water vapor in the air may condense. Pilots should refer to the FAA-approved Rotorcraft Flying Manual (RFM) for when and how to apply carburetor heat. In most cases, the needle should be kept out of the yellow arc or in the green arc. This is accomplished by using a carburetor heat system, which eliminates the ice by routing air across a heat source, such as an exhaust manifold, before it enters the carburetor. [Figure 4-21] If ice is allowed to form inside the carburetor, engine failure is a very real possibility and the ability to restart the engine is greatly reduced.

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