Ancillary controls/operation of Aircraft systems Flashcards
Primary flight controls and trim system
Ailerons
- Equipped with counterweights to help with use
- The counterweights also reduce flutter
The phenomenon of flutter is an effect due to over-speed of an airplane in flight. In this case, ailerons vibrate or beat rapidly or erratically
Rudder
- Equipped with a SERVO-TAB (moves in the opposite direction)
- Helps the pilot to deflect the rudder
- Used as the trim tab
- Pedals control the nose wheel 30º arc
Stabilizer
Equipped with an ANTI SERVO TAB: (moves in the same direction)
Increases resistance on the controls (more precision)
Used as the trim tab
Left seat pilot electrical trim on the yoke
Alternate air
Induction air for the engine enters a large air duct at the rear of the bottom cowl.
The air is directed through a filter, and on to the servo regulator.
A heated alternate air source is incorporated is used to provide airflow to the engine in case the normal flow of air through the filter is restricted.
The alternate air door is spring
loaded, and will remain closed
during normal operation.
The alternate air door will operate automatically, as the normal induction airflow through the filter is restricted, or when the push-pull control, located on the control pedestal, is placed in the FULL ON position.
Cowl flaps
The cowl flaps, located on the bottom of the engine nacelles provide additional cooling for ground operation or high temperature conditions.
They are manually operated by push-pull controls located in the cabin, on the fuel control panel located between the front seats.
Mixture
The mixture control valve gives fuel rich mixture on one stop and a progressively leaner mixture as it is moved toward the idle cut-off stop. The setting incorporated in the fuel control system is worked out to meet the engine requirement for all power settings without compromise. The full rich stop defines sea level requirements, and the mixture control provides altitude leaning.
Propeller
The “Compact” propellers on the Aztec are Hartzell HC-E2YR-2RB/8465-7R constant speed, full-feathering units which represent new concepts in basic design.
They combine low weight with simplicity in design and rugged construction.
These are controlled entirely by use of the propeller control levers located in the center of the control quadrant.
Feathering of the propellers is accomplished by moving the controls fully aft through the low RPM detent into the feathering position. Feathering takes approximately three to ten seconds. A propeller is unfeathered by moving the prop control ahead and engaging the starter. (See Section III, for complete feathering and unfeathering instructions.)
FUEL AND OIL REQUIREMENTS
Aviation grade 91/96 (minimum) octane should be used in the Aztec. The use of lower grades of fuel can cause serious engine damage in a very short period of time, and is considered of such importance that the engine warranty is invalidated by such use.
The oil capacity of the Lycoming IO540 engine is 12 quarts. It is recommended that engine oil and oil filter element be changed every 50 flying hours, sooner under unfavourable conditions. Engine oil is normally changed with the filter. However, if the full flow (cartridge type) oil filter is used and changed every 50 hours of operation, the intervaintervals between oil changes may be increased as much as 100 percent. The minimum safe quantity of oil required is 3 quarts.
FUEL SYSTEM
Four thirty-six gallon flexible fuel cells located outboard of the engines provides fuel storage in the Aztec.
The cells should be kept full of fuel during storage of the airplane to prevent accumulation of moisture, and to prevent deterioration of the cells. For storage of more than ten days without fuel, the cells should be coated with light engine oil to keep from drying out.
The fuel system in the Aztec is simple, but completely effective. Fuel can be pumped from any tank to both engines, through use of the engine-driven and electric fuel pumps.
For normal operation, fuel is pumped by the engine-driven pumps from the tanks directly to the adjacent fuel injector. The fuel valves can be left on at all times and the crossfeed left in the off position. Electric auxiliary fuel pumps, located in the engine nacelles, are installed in by-pass fuel lines between the tanks and the engine-driven pumps. The electric pumps can be used to provide pressure in the event of failure of the engine-driven pumps. They are normally turned on to check their operation before starting the engines, turned off after starting, to check engine-driven pumps and left on during take-off and landing, to preclude the possibility of fuel pressure loss due to pump failure at critical times.
If one of the engine-driven pumps fails, the electric pump to that engine can be turned on to supply the fuel. However, if desired, the fuel can be pumped by the operating engine-driven pump to the failed pump engine simply by turning on the cross-feed. The good pump will then be supplying both engines from its tank. If this tank runs low on fuel, fuel can be drawn from the opposite tank by turning on the electric pump on the failed pump side, leaving the crossfeed on, and turning the fuel valve on the empty side off. Then the electric pump on the failed pump side will be supplying both engines from its tank.
Fuel can thus be used from one tank or the other, by shutting off one main valve and turning on the crossfeed, to balance fuel loads or for other purposes. For all normal operation, it is recommended that fuel be pumped directly from the tanks to their respective engines, with the crossfeed off.
The fuel valve controls and crossfeed control are located in the fuel control panel between the front seats. Two electric fuel gauges in the engine gauge cluster on the instrument panel indicate the fuel quantity in each tank. The electric fuel gauges indicate the fuel quantity in the tank selected by the fuel selector handle, located in the fuel control box. The electric fuel pump switches are on the lower left side sub-panel.
A crossfeed line drain valve control is mounted on the front face of the fuel control panel box. This valve should be opened occasionally, with the crossfeed on, the left electric fuel pump on, and then the right electric fuel pump on to allow any water that might accumulate at that point to be drained out. The heater fuel control is also placed on the fuel control panel, so that fuel to the heater can be turned off if necessary.
The fuel strainers and fuel line drain valves are located in the inboard sides of the main wheel wells. They are fitted with quick drains and should be drained regularly through their small access ports. In order to check the fuel system for possible moisture content, each fuel cell quick drain valve should be opened and drained and the quick drain valve on the fuel strainer should be opened and drained. This procedure should be accomplished at the three quick drain valves located in each main wheel well. Fuel screens are provided at the tank outlets, in the injectors and in the fuel filter bowls.
Idle cut-offs arc incorporated in the injectors and should always be used to stop the engines. This is accomplished by pulling the mixture control levers to the rearmost position.
Oil flow through a typical Lycoming engine
Operating pressure
The normal oil pressure range for most Lycoming engines is between 60 to 90 pounds per square inch (psi). This range is indicated by the green arc on the oil pressure gauge. The maximum oil pressure allowed for short durations is 115 psi on most models. The maximum allowable pressure has increased over the years from 100 to 115 psi. The top red line on most oil pressure gauges is 100 psi. The lowest allowable limit for oil pressure with the engine operating at idle with hot oil is 25 psi, which is indicated by the lower red line on most oil pressure gauges.
Oil flow through a typical Lycoming engine
Lycoming engines use a “wet sump” oil system. This simply means that the oil sump is mounted under the engine and oil flows by means of gravity back to the sump after it has been pumped through the engine. The sump is completely open on the top so that all areas of the engine can drain back into it, and it functions like a large drain pan. “Dry sump” systems have a separate dedicated oil tank. Oil is routed to the tank once it has completed its course through the engine.
The Lycoming oil pump is located in the accessory housing. It consists of an aluminum outer body and two steel impellers, one of which is gear-driven off the crankshaft. (See photos 01, 02 and 03 on this page.) It produces oil pressure in direct proportion to how fast the gears spin. At higher engine rpm, the pump produces more oil pressure than at low engine rpm.
Oil is drawn up through the suction screen in the sump and through the oil pump impellers. The oil is then routed to the thermostatic bypass valve (also called a vernatherm valve).
Oil continues to flow to the oil filter adapter on the accessory case and through the oil filter (or screen if the engine is not equipped with an oil filter). From the filter, oil is routed to the oil pressure relief valve. The oil pressure relief valve is located on the top right side of the crankcase. It relieves excessive oil pressure by opening a drain port to the sump to bypass some of the oil flow if oil pressure gets too high.
Oil then travels to the crankshaft bearings and through predrilled passageways in the case to lubricate the internal engine parts through either pressure or splash lubrication. After completing its course, the oil drains back to the sump.
Turbo Charger
At higher altitudes air is thinner, resulting in decreasing engine performance due to lowered air density as a plane climbs.
A turbocharger supplies the engine with denser, compressed air to compensate for the thinner outside air, allowing the aircraft to perform more efficiently even at high altitudes.
The turbocharger will provide the engine with near sea level performance up to a certain altitude, the critical altitude, at which point the turbocharger is at maximum capacity and any further climb will result in lowered engine performance
Supercharger
While turbochargers are powered by exhaust gasses exiting the engine, and thus do not require engine power, superchargers are powered directly by the engine’s power output.
Superchargers compress the fuel/air mixture after it leaves the carburetor, whereas turbochargers compress the air before it is mixed with fuel.
When engine power is increased at low altitudes using a supercharger, it’s called boost. At high altitudes it’s called supercharging.
Hydraulic System
The hydraulic system is used for the extension and retraction of both the landing gear and flaps. The operation of these units is accomplished by the landing gear and flap selectors of the hydraulic control unit which is housed within the control pedestal under the engine controls. Pressure is supplied to the control unit from an engine-driven pump mounted on the left engine.
To effect extension or retraction of the gear and flaps, the controls which protrude through the face of the pedestal are moved from the center “OFF” in the desired direction. When the selected component is fully extended or retracted, hydraulic pressure within the control unit forces the control back to a “Neutral” or “Off” position, which allows the hydraulic fluid to circulate freely between the pump and the control unit. Also, it isolates the activating cylinders and associated lines from the hydraulic fluid supply. This prevents complete loss of fluid in the event of a leak in the lines between the control unit and the component or at the actuating cylinders. The return of the control handle to the “OFF” position is also a secondary indication that the components have reached full extension or retraction. The landing gear position lights and the flap indication should be used as primary indications while the mirror on the right side of the left nacelle shows the position of the nose gear.
Gear retraction and extension will occur normally in 9 to 12 seconds. Flap operation requires about 3 seconds.
The emergency hydraulic hand pump, which is integral with the control unit, is used to obtain hydraulic pressure in event of failure of the hydraulic pump on the left engine. To operate the emergency pump, the handle should be extended to its full length by pulling it aft and positioning the gear control as desired. Approximately fifty strokes are required to raise or lower the landing gear.
For emergency extension of the landing gear, if failure of the hydraulic system should occur due to line breakage or hydraulic control unit malfunction, an independent CC»2 system is available to extend the landing gear.
Included on the left main gear is an oleo actuated by-pass valve which makes it impossible to retract the landing gear while the weight of the airplane is on the gear. This valve is open when the oleo strut is compressed and by-passes all hydraulic fluid, on the pressure side of the system, to the return side, preventing any pressure build-up in the retraction system. When the oleo strut is extended as in flight, or when the aircraft is on jacks, the valve is closed permitting the system to operate in the normal manner.
Electrical System
The electrical system for the Aztec includes a 12 volt 35 ampere hour battery, enclosed in a sealed stainless steel battery box. (See Section V, for battery service.) Two 12 volt 70 ampere alternators are installed as standard equipment. They are paralleled by the use of one voltage regulator to control field voltage of both units. Also incorporated in the system is an overvoltage relay. Its function is to open and remove field voltage to the unregulated alternators in the event of a failure of the voltage regulator, thus preventing an overvoltage condition which could damage the electrical equipment.
As an added safety feature, to provide for complete dual system reliability, an auxiliary voltage regulator and overvoltage relay has been installed. Each set of regulators and relays is controlled by a switch located on the left sub-panel next to the master switch. The switch is placarded “Voltage Regulator Selector”, “Main”, and “Auxiliary”. The switch should normally be in the “Main” position. The operation of the alternators may be checked by an ammeter switch located directly under the ammeter. If the battery is completely discharged, charge it before take-off as three volts are needed to excite the alternator.
Electrical switches for the various systems are located on both sub-panels of the instrument panel. The circuit breakers are on the right side sub-panel. To reset the circuit breakers simply push in the reset button. Reduce the electrical load to minimum and allow two minutes before resetting the breakers. Corrective action should be taken in event of continual circuit breaker popping. The alternator circuit breakers, mounted on the same panel, are of the switch type and should not be turned off while the engines are running.
Instrument lighting is provided by two spotlights installed in the center of the cabin ceiling. These lights are operated by a rheostat switch which is located directly aft of the lights. The lights are turned on with the first movement of the rheostat knob and the light intensity increased by further rotation of the control. Provided as optional equipment are individual post lamps mounted on the panel adjacent to each instrument. These lights are controlled by a rheostat switch located on the panel with the other electrical switches. Operation of the rheostat is the same as for the spotlights. Located in the cabin ceiling just aft of the windshield, on both the right and left sides, are two map lights equipped with clear lenses. Each light is operated by the switch located adjacent to the unit. For the passengers, reading lights are installed over each seat as well as a cabin dome light located in the center of the cabin ceiling. A separate switch is used for each of these units.
There are overhead lights in both the forward and aft baggage compartments. They will turn on and off with the opening and closing of the baggage doors. On the upper right side of the instrument panel is a red warning light labelled “Door Ajar”. It will light if the master switch is on and either the forward baggage door or main cabin door are not completely closed and latched.
CAUTION
Do not leave either baggage compartment door open for extended periods.
The starter and magneto switches are on the left side panel near the instrument panel. The starter switch is of the momentary rocker type.
An external power receptacle, located in the lower right side of the nose, is available as optional equipment. Turn the master switch off before inserting or removing a plug at this receptacle. Leave the master switch off while using external power.
Flaps
The camber can be modified by variable sections operated by the pilot.
Those sections, located at the trailing edge of each wing, are called FLAPS.
Flaps are used for different phase of the flight.
Position up:
Cuise
10 degrees.
Lift increases
For take-off
Full flaps.
High Lift And High drag For Landing
Lift increases
Drag increases
Approach
The angle of attack increases when the flaps are lowered.
The aerodynamic controls are using the same principle.
Flaps increase the angle of attack, angle of the wing is decreased.
To restore angle of attack, camber is increased: lift is increased.
Flaps cause turbulent air filets.
A slot between flaps and wings will restores the laminar layer.
Near the stall, air fillets brake away, slat creates an opening that redirects the air fillets to a more laminar circulation.
Landing Gear
All three landing gear units on the Aztec incorporate the same soft acting air-oil struts, and contain many directly interchangeable parts. (See Section V, for gear maintenance.)
Main wheels are 600 x 6 Cleveland Aircraft Products units with disc type brakes with metallic lining and 700 x 6 tires with an eight ply rating. The nose wheel is a Cleveland 600 x 6 model fitted with a 600 x 6 tire with a four ply rating. All tires have tubes. (See Section V, for tire service.)
Main gear brakes are actuated by toe brake pedals on the left set of rudder pedals. Hydraulic brake cylinders located in front of the left rudder pedals are readily accessible in the cockpit for servicing. Toe brakes for the right side are available as optional equipment. A brake fluid reservoir, which is connected to the brake cylinders with flexible lines provides a reserve of fluid for the brake system, and is mounted on the fuselage structure inside the left nose access panel. (See Section V, for brake service.)
Parking brake valves, operated by a control on the left side of the instrument panel, are installed ahead of the forward cabin bulkhead and are also serviced through the left nose access panel.
The nose wheel is steer-able through a 30 degree arc, through use of the rudder pedals. As the nose gear retracts, the steering linkage becomes disconnected from the gear so that the rudder pedal action with the gear retracted is not impeded by nose gear operation.
The position of the landing gear is indicated by four light bulbs located on the pedestal. When the three green lights are on, all three legs of the gear are down and locked; when the amber light is on, the gear is entirely up and enclosed by the gear doors. When no light is on, the gear is in an intermediate position. GEAR INDICATION LIGHTS ARE AUTOMATICALLY DIMMED WHEN THE POST LIGHT CONTROL IS TURNED ON.
A red light in the landing gear control knob flashes when the gear is up and either one of the throttles is pulled back. When both throttles are closed beyond a given power setting, approximately 12 inches of manifold pressure with wheels not down, the landing gear warning horn sounds.
To guard against inadvertent retraction of the landing gear on the ground, a mechanical latch, which must be operated before the landing gear control can be moved upward, is positioned just above the control lever. The control knob is in the shape of a wheel to differentiate from the flap control knob, which has an air-foil shape. There is also an anti-retraction valve located on the left main gear which prevents a build-up of hydraulic pressure in the retraction system while the weight of the airplane is resting on its wheels.
A tow bar is provided with each airplane. When not in use, it is stowed in the forward baggage compartment.
When towing with power equipment, caution should be used not to turn the nose gear beyond its 30 degree arc as this may cause damage to the nose gear and steering mechanism.
Brakes
The brake system is filled with MIL-H-5606 (Petroleum base, red) hydraulic brake fluid. This should be checked at every 100 hours inspection and replenished when necessary. Do not use vegetable base brake fluids (blue) when refilling the system. When it is necessary to add fluid, open the left nose access panel, exposing the brake reservoir. Then add fluid to the reservoir, bringing the fluid to the indicated level.
If it is necessary to bleed the brake system to get air out of the lines, fluid should be added under pressure at the bleeder attachment on the brake unit.
No adjustment of brake clearances is necessary on the Aztec brakes. If after extended service, braking action requires
too much movement of the toe pedal, new brake linings can easily be installed by removing the four bolts which attach the brake units, then replacing the brake linings held in place by brass rivets.
Main wheels are quickly removed by first cutting the safety wire and removing eight bolts to drop the brake lining. Remove the dust cover, hub cap, cotter pin and axle nut. The wheel will slip off the axle. The nose wheel is removed by taking off the hub nut and withdrawing the axle bolt, the axle retainer cups, and the axle from the nose wheel fork.
Tires are dismounted from the wheels by deflating the tube, then removing the wheel through-bolts, allowing the wheel halves to be separated. In reassembling the wheels, care should be taken to torque the bolts properly, according to instruction on the wheels and reassembling for proper balance.
