The carburetor measures the fuel/air mixture to deliver the mix to cylinders by weight and not by volume.
The throttle valve measures the fuel/air mixture in volume and delivers to the intake manifold.
Carburetor measures fuel/ air mixture by weight.
Throttle valve measures fuel/air mixture by volume.
It is important of warm up the eng before T/o since some portion of the gasoline in fuel/air mix does not vaporize and is still in liquid form when it enters the engine. It is vaporized by the engine. It is important to warm up the engine before T/o. This is done so that there is sufficient engine heat to vaporize all the fuel and develop full power during T/o.
On applying Carburetor heat mixture becomes rich because of the low density of hot air, therefore you must decrease the fuel/air mix to lean the mixture.
Min 50% Relative humidity is required for icing to occur (In Carburetor) and the icing hazards increasing as the Rel humidity increases.
Danger of Carb using – 50c to 300c. No Carb usnig below –50c because of no water vapors present in air, any small amount of moisture if present is frozen and is therefore harmless. Extremely low temperature causes the engine to run lean because density of air is low in hot air and the fuel flow is constant therefore normally ISA conditions Air density: 10, Fuel Flow: 5, cold temp Air density: 12, Fuel Flow: 5, because of high density of air. Mixture because lean. (More air less fuel)
In high temperature conditions (summer etc.) Air density decreases Fuel Flow remains constant and normal Air density: 10, Fuel Flow: 5, In Summer Air density: 8, Fuel Flow: 5, because of low density of air, mixture because rich (Less air more fuel)
Important point to remember while using Carburetor Heat – Hot Air supplied to Carburetor for Carburetor de-icing is not filtered therefore avoid ground usage. When a hot engine (with fuel injection system) is shutdown the heat inside the cowling may cause the fuel in the lines to vaporize. Therefore at the next start, the vapour present may cause the fuel in the lines to vaporize, therefore at the next engine start, the vapour in the lines can prevent the engine from getting enough fuel to start the engine.
Tappet clearance/Valve Clearance- gap between Valve Stem and the Rocker pad.
V2 is greates than 1.2 of Vs or 1.1 of YMCA.
TORA = R/w Length
TODA= R/w length + Clearway
ASDA = R/w length + Stopway
Balanced full length is when Take Off dist required = Accelerate Stop Distance Required
Balance Field Length is when TODR-T/o Dist Required = ASDR Accelerate Stop Dist Required
Climb Gradient
1st Segment- V2 at 35 ft to gear up with the ROC.
2nd Segment-V2 @ 2.4% gross to min 400 feets.
3rd Segment- Accelerate, retract flaps to VBG (Best Climb Speed) Max Continous power and 1.2% ROC available.
4th Segment- Climb to 1500 ft above ground level @ 1.2% minimum
RTOW takes accounts of all 4 Flight Segments.
General chart takes accounts of only up to 2nd Flight Segment of fit path.
Magnetos- when breaker points open the flow of current in the primary winding is arrested, the magnetic field around the primary winding collapses falling inward on itself and cutting the secondary winding.
Impulse Coupling- Momentarily rotates the magnetos to assist short.
Pitch- Distance (feet) a Propeller travels forward in one revolution.
Theoretical pitch/Geometric pitch- distance traveled by a propeller if it was working in a perfect fluid.
Practical Pitch/Effective Pitch- Distance a propeller travels forward in the medium as air.
Prop SLIP-Dist between theoretical & Practical Pitch or Dist between Geometric & Effective Pitch.
OAT usually over reads temperature (show more than actual) because the air passing through the a/c body gets heated due to the air friction.
Example- OAT over reads upto 10C at speeds of 90kls. and 40c at speed of around 200 kts and 300 c at 500 kts. Therefore, true air temperature can be calculated approximately by OAT.
Tachometer shows the speed of engine crankshaft in hundreds of rpm. On fixed pitch propeller tachometer shows rpm of engine crankshaft and propeller, if the Propeller is not fitted with the reduction gearing.
For every one Power Stroke the Crankshaft rotates twice, therefore in a four stroke engine, four strokes are used to produce two revolutions of the Crankshaft.
In a Four Stroke Engine, producing maximum rpm of 2500 rpm E.G. Cessna 152, the no. of Power strokes occurring in a minute is 1250 or the number of total Strokes in a minute is 5000.
. In a Constant speed propeller unit, Propeller rpm is on tachometer and Engine Power setting on manifold press gauge.
Manifold pressure gauge indicates press of fuel/air mixture in the engine intake manifold in inches of mercury. 14.7 psi is equal to 29.92 hg. Therefore, a manifold reading of 26” Hg indicates a pressure of about 13 pounds per squire inches (Psi).
When propeller pitch control is moved backward (Fine to coarse) without changing the power settings the manifold press will increase.
When propeller is moved forward (Coarse to Fine) without changing the power setting the manifold press will decrease.
Therefore, when propeller is moved backward (Fine to coarse Pitch) without changing the power setting the rpm decreases, therefore, engine revolution decreases, since the fuel/air mix flow also decreases ( As per Bernoulli’s principle- As the velocity decreases pressure increases).
Therefore, the manifold pressure gauge shows press decreasing.
When propeller is moved forward (Coarse to Fine) the rpm increases, therefore, engine revolution increases, since the fuel/air mix also increases, therefore (As per Bernoulli’s principle again- As the velocity increases pressure decreases).
Therefore the manifold pressure gauge shows pressure decreasing.
When propeller rpm increases manifold pressure decreases in a CSU unit.
When propeller rpm decreases manifold pressure increases in a CSU unit
When increasing power increase rpm first by moving propeller lever forward and then manifold press in a CSU unit.
When decreasing power, decrease manifold press first and than decrease rpm by moving propeller lever backward in a CSU unit.
With fixed pitch propeller unit on increasing rpm increases manifold pressure as well.
EPR- Engine Pressure Ratio means the pumping pressure ratio of the whole gas generator.
EPR is ratio of press at exit up the Compressor drive to the pressure at the Compressor inlet.
E.g. 66÷100= 0.66%, 200÷100= 2
Pressure ratio of a gas generator is the ratio of pressure at the compressor exit to that at the compressor inlet.
Press ratio is at maximum rpm 6 to 1.
Thrust Reversers
Clamshell type doors- operates pneumatically, reverse the exhaust gas-stream. The ducts are opened to deflect exhaust gases.
Bucket Target System- operates through conventional pushrod system or is hydraulically powered, it uses bucket type doors to reverse the hot gas stream.
Cold Stream Reversor System- operates by air motor or by hydraulic rams. The movable cowling moves rearward, the blocker doors fold and blank off the cold stream nozzle, diverting the airflow through the cascade vanes.
Cascade- are Baffles, which when the pilot selects the reverse thrust by putting the throttle control into reverse thrust detent, deflects the jet blast forward to achieve the reverse thrust.
Pilotage- Navigation by reference to landmarks only.
Dead Reckoning- Navigation by use of pre-determined vectors of wind and TAS and pre-calculated headings Groundspeed and on the basis of these information calculated estimated time of arrival.
Radio Navigation- Navigation by Radio aids.
Celestial Navigation– Navigation by measuring angle to heavenly bodies, (Sun, Moon and Stars) to determine the position on the Earth.
Inertial Navigation- Navigation by self-contained airborne gyroscopic equipment or Electronic computer that gives a continuous display of A/c position.
Dip- The earth’s magnetic lines of forces are horizontal at the equator but becomes vertical towards the poles. This causes the compass to tend to DIP or bend or go vertical in higher latitudes.
Dip must be corrected or compensated for in a compass during construction.
Magnetic Variation/Magnetic Declination –Angle between Mag and true North or meridian.
Agonic lines- No variation/Zero Variation.
Isogonics lines/ISOGONALS lines means Equal Variation
Deviation- Magnet mounted in simple direct reading compass do not point directly in the direction of magnetic North, but, due to the influence of magnetic fields associated with the airframe metal and engine, deflects slightly to what is known is COMPASS NORTH.
DEVIATION- is the Angle through which the compass needle is deflected from the mag meridian/ NORTH.
(GHA) Greenwich hour Angle- of a hevenly body is the angular distance between the Greenwich Meridian and the meridian of the body. It is measured westward through 3600.
The Declination of a heavenly body is its angular distance between North or South of the Celestial equator (hence it corresponds to latitude), in degrees and minutes North or South of the celestial equator, it is same as latitude.
SHA
Sidereal Hour Angle of a star is the angular distance between the First point of the Aries and the meridian of the star measured westward from Aries through 3600.
First Point of the Aries (Y) Also called Vernal Equinox, is a point on the celestial equator arbitrarily chosen as a reference point from which to measure the hour angles of the stars.
(LHA) Local Hour Angle- of a heavenly body is the angular distance between your meridian and the meridian of the body, measured westward.
It is the algebraic sum of GHA of body and your longitude.
Sub Stellar Point is bringing (thinking/assuming) the heavenly body from the sky to earth. Since it is easier to measure the hour angle of the heavenly bodies, when they are assumed to be on the Earth.
Therefore we can say that the Sub Stellar Point is a point on the surface of the earth directly beneath the heavenly body.
Convergency- Angle which one meridian makes with the other on the Earth near either poles. At equator there is no convergency between meridians.
On VFR Navigation Charts and VFR terminal charts a elevation legend is printed to show what color are used for different locations. It is also called HYPSOMETRIC Tint Scale.
Relief is used to represent the elevation above sea level. It is shown by contour lines, layer tinting and spot lights.
Contour lines are used to show equal elevation above mean sea level. The closure the contours, the steeper is the slope of a hill or valley. The highest spot (elevation of hill etc) on a particular map is represented by the largest size of numerals and the numerals is boxed with the layer tinting removed with in the box.
The highest elevation is also indicated on the white border of the chart, with its geographical co-ordinates.
ISOGONIC lines – – – – – – – – – – – REPRESENT Equal Variation
Albedo- is the refraction of the light due to the clouds reflecting light in the sky.
In DME slant ranges are given. When the slant range is double the altitude, the error between the slant range and the ground distance is O.
Encoding Altimeter
Prenmatic type Altimeter is a conventionally barometric altimeter with an encoding device that converts altitude into digitally coded electoral signals in 100 foot increments.
It uses evacuated capsules called aneroids to sense altitude, by expanding and contracting with static pressure.
The movement of the aneroid walls drives the altimeter pointers for visual display via gearing.
At the some time the pressure of the moving aneroid drives a small glass disc providing the elev signal to activate the encoding device.
Encoding Altimeter
Servo type altimeter uses the aneroid system to sense altitude but the power to drive the encoding and display mechanism is derived from the airplane’s electrical system.
The servo type altimeter having an outside source of power drives pointers and encoders at the same time provide ancillary output for an altitude alerter, rate of climb indicator, vertical navigation system and Autopilot.
The servo altimeter is very accurate and very reliable. It’s disadvantage is that it is completely dependent on electric power (A/c electrical system) to operate.