Aircraft General Knowledge (Basic Aircraft Instruments) PDF

**[AIRCRAFT GENERAL KNOWLEDGE]** (Basic Aircraft Instruments) **Aircraft instruments** are an *aid* to enable pilots to operate the aircraft *more precisely*, and therefore obtain *maximum performance* and *enhanced safety*. **[A. PRESSURE INSTRUMENTS (Pitot-Static System)]** \- Pitot-static ins...

**[AIRCRAFT GENERAL KNOWLEDGE]** (Basic Aircraft Instruments) **Aircraft instruments** are an *aid* to enable pilots to operate the aircraft *more precisely*, and therefore obtain *maximum performance* and *enhanced safety*. **[A. PRESSURE INSTRUMENTS (Pitot-Static System)]** \- Pitot-static instruments rely on air pressure differences to measure speed and altitude. \- Uses a combination of **impact/ram air** pressure and **static** pressure. \***[Pitot tube]** -- supplies ram air pressure; mounted on the wing or nose section so the opening is exposed to the relative wind; an increase in airspeed increases ram air pressure. (Pitot tubes are susceptible to icing, that's why most airplanes are equipped with *pitot heater*.) \***[Static port]** -- allows static pressure to enter the system; mounted on the side of the fuselage in the area of relatively undisturbed air **(1)** **Airspeed Indicator (ASI)** \- Indicates the speed at which the airplane is moving through the air. \- Only instrument to operate using both pitot and static pressure. \- Speed is determined by comparing ram air with static air pressure: the greater the differential, the greater the speed. \- Divided into color-coded arcs that define speed ranges for different phases of flight: Green arc -- normal operating range White arc -- flap-operating range Yellow arc -- caution range; only in smooth air and with caution Red line -- never-exceed speed **[Kinds of airspeed:]** \(1) **Indicated airspeed** (IAS) -- actual airspeed reading \(2) **Calibrated airspeed** (CAS) -- IAS corrected for installation and instrument errors \(3) **True airspeed** (TAS) -- airspeed corrected for non-standard pressure and temperature \(4) **Groundspeed** -- speed of aircraft relative to the earth's surface [**V-speeds** (speed limitations)]: 1. V~SO~ -- stalling speed or minimum flight speed in the landing configuration (flaps and gear down) 2. V~S1~ -- stalling speed or minimum steady flight speed obtained in a specified configuration ("clean") 3. V~FE~ -- maximum speed with flaps extended 4. V~NO~ -- maximum structural cruising speed 5. V~NE~ -- never exceed speed 6. V~LO~ -- maximum speed you can safely lower or extend/raise your landing gear 7. V~LE~ -- maximum speed with landing gear extended 8. V~A~ -- maneuvering speed; maximum speed at which you can apply abrupt control movement without causing structural damage (no indication in the ASI) **(2)** **Altimeter** \- Measures the vertical elevation above a given reference point. \- Senses pressure changes and displays altitude in *feet*. \- Has 3 pointers/hands to indicate altitude: longest -- hundreds of feet; middle sized -- thousands of feet; shortest -- tens of thousands of feet. \- Contains aneroid wafers -- expand and contract as atmosphere pressure from the static source changes; a mechanical linkage translates these changes into pointer movements on the indicator. **[Types of altitude:]** \(1) **Indicated** -- altitude read *directly* from the altimeter \(2) **Pressure** -- altitude when barometric scale is adjusted/set to *29.92 inHg* \(3) **True** -- actual height above *mean* *sea level* \(4) **Density** -- pressure altitude corrected for non-standard temperature; used to determine airplane performance \(5) **Absolute** -- actual height of an aircraft above the earth's surface \*"From high to low, look out below" **Q~NH~** -- local/station pressure **Q~NE~** -- standard pressure **Q~FE~** -- field elevation **(3)** **Vertical Speed Indicator** (VSI) \- Gives the *rate* at which the aircraft is climbing/descending in fpm (feet per minute). \*Almost useless in turbulent condition because it has a lag of 6-9 seconds. **[Pitot-static system blockage]:** \*If pitot tube is blocked -- [ASI] reads high in climb, low in descent \*If static port is blocked -- [ASI] reads low in climb, high in descent; [ALT] freezes; [VSI] reads zero **[B. GYROSCOPIC INSTRUMENTS]** **Gyroscope** -- rapidly spinning wheel with its weight concentrated about its rim **[Characteristics:]** \(1) ***Rigidity in space*** -- the spinning wheel remains in a fixed position in a plane in which it is spinning \(2) ***Precession*** -- tilting or turning of a gyro in response to pressure; gyro reacts to an applied force as though it was applied at 90 degrees in the direction of the rotation from the actual point of application \***[Vacuum (suction) system]** (engine-driven/electrically driven) -- controls the vacuum pump to create a partial vacuum in the system to supply rapid air to spin the gyros \***[Suction gauge]** -- monitors the available vacuum pressure in the system **(1)** **Attitude Indicator (AI)** \- Displays the actual attitude of the aircraft relative to the earth's horizon. \- Sometimes referred to as the "master instrument". **(2)** **Turn Coordinator (TC)** \- Commonly used in airplanes to indicate *rate* and *quality* of turn and to serve as an emergency source of bank information if the Attitude Indicator fails. \- Is actually a combination of 2 instruments: a *miniature airplane* and an *inclinometer* (ball). \- Allows the pilot to establish and maintain *constant rate turns* (standard rate turn: 3 degrees per second). \- No pitch information. \- Modern version of the Turn and Slip Indicator. ***[Skid]***: the rate of turn is too great for the angle of bank; ball is outside the turn; excessive rudder pressure. ***[Slip]***: the rate of turn is too slow for the angle of bank; ball is inside the turn; insufficient rudder pressure. \*In all cases, apply rudder pressure on the side that the ball is exposed, i.e., "*step on the ball*". **(3) Heading Indicator (HI)** \- Senses airplane movement and displays heading based on a 360 degrees azimuth, with the final zero omitted (e.g., 9 -- 90degrees; 27 -- 270 degrees). \- When set, it is the primary source of heading information. \- Indirectly indicates bank. \- No automatic north-seeking system. \- Align with magnetic compass every 15 minutes due to precession (during straight and level, unaccelerated flight). **[C. MAGNETIC INSTRUMENTS]** **Magnetic Compass** \- The only direction-seeking instrument in the airplane. It is used primarily to set the Heading Indicator prior to flight and to verify its continued accuracy during flight. The readings are accurate only when the aircraft is in straight and level, unaccelerated flight. \- The magnet on the compass aligns itself with the earth's magnetic fields. **[Compass errors:]** \(a) ***Variation*** -- the angular difference between the true and magnetic north \(b) ***Deviation*** -- difference between the indicated magnetic heading and the actual heading, due to other magnetic fields in the airplane \(c) ***Magnetic dip*** -- the tendency of the compass needle to point down as well as to the magnetic pole; this error is greatest at the poles and zero at the magnetic equator **[Acceleration errors]** -- an acceleration in the northern hemisphere shows a turn to the north, deceleration shows a turn to the south; more pronounced on headings of east and west; error does not occur when flying directly north or south ("ANDS -- accelerate north, decelerate south") **[Turning errors]** -- causes the compass to lead or lag the actual magnetic heading of the airplane during turns; in the northern hemisphere, it will indicate a turn to the west if a right turn is entered from a heading of north, a left turn will indicate a turn to the east; most pronounced when turning from headings of north or south ("UNOS -- undershoot north, overshoot south") \(d) ***Compass card oscillation*** -- error results from the erratic movement of the compass card, which may be caused by turbulence or rough control technique [ENGINE INSTRUMENTS]: 1. Tachometer 2. Oil temperature gauge 3. Oil pressure gauge 4. Fuel quantity gauge 5. Fuel flow indicator 6. Exhaust gas temperature gauge 7. Manifold pressure gauge 8. Cylinder head temperature gauge