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Flashcards in Seminole Aircraft Systems Deck (14)
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Tell me about the engines.

The Seminole is equipped with two Lycoming, 4-cylinder, O-360 (opposed, 360 cubic inch) engines rated at 180 horsepower at 2700 RPM. The right engine is designated as an LO-360 due to the fact that it rotates to the left. The engines are direct drive (crankshaft connected directly to the propeller), horizontally opposed (pistons oppose each other), piston driven, carbureted and normally aspirated (no turbo or supercharging). Engine ignition is provided through the use of engine-driven magnetos which are independent of the aircraft's electrical system and each other. 

L — Lycoming

H — Horizontally Opposed

A — Air Cooled

N — Normally Aspirated

D — Direct Drive


Tell me about carburetor icing.

Under certain moist atmosspheric conditions at temperatures of 20° to 70° F (-5° to 20° C), it is possible for ice to form in the induction system, even in summer weather. This is due to the high air velocity through the carburetor venturi and the absorption of heat from this air by vaporization of the fuel. To avoid this, the carburetor heat is provided to replace the heat lost by vaporization. The initial signs of carburetor ice can include engine toughness and a drop in manifold pressure. Carburetor heat should be selected on if carburetor ice is encountered. Adjust mixture for maximum smoothness.

Only apply full carburetor heat—never partial carburetor heat!


Tell me about the propellers.

The Seminole is equipped with Hartzell two-bladed, controllable pitch, constant speed, full feathering metal propellers.

Controllable Pitch

Controllable pitch is the ability to control engine RPM by varying the pitch of the propeller blades. When the blue propeller control handle is moved forward, oil pressure, regulated by a propeller governor, drives a piston, which moves the blades ot a low pitch, high RPM (unfeathered) position. When the blue propeller control handle is moved aft, oil pressure is reduced by the propeller governor. This allows a nitrogen-charged cylinder, spring, and centrifugal counterweights to drive the blades to a high pitch, low RPM (feathered) position.

Constant Speed

After RPM setting is selected with the blue propeller control handles, the propeller governor will automatically vary oil pressure inside the propeller hub to change the propeller blade pitch in order to maintain a constant engine RPM. Because of this, changes in power setting (manifold pressure) and flight attitude will not cause a change in RPM. 

Full Feathering

When the propeller blades are in alignment with the relative wind, they are feathered. Feathered propeller blades reduce the drag caused by the blade area exposed to the relative wind. Feathering the propeller blade on the Seminole is accomplished y moving the blue propeller control handle fully aft past the low RPM detent, into the "FEATHER" position. The propeller takes approximately six seconds to feather. When feathering the propeller, the mixture should be placed to cutoff to stop engine combustion and power production.

The Seminole is equipped with a centrifugal stop pin that prevents propeller feathering below 950 RPM. The purpose of this is to allow the propeller blades to remain in a low pitch upon engine shutdown. This will prevent excessive loads on the engine starter during the enxt engine start.

Regardless of the Prop level prosition, if oil pressure is lost, the propeller will feather when the RPM is above 950 RPM. Typically, RPM will be above 950 in flight and on takeoff roll and landing roll due to airflow over the propeller.

Propeller Overspeed

Propeller overspeed is usually caused by a malfunction in the propeller governor which allows the propeller blades to rotate to full low pitch. If propeller overspeed should occur, retart the throttle. The propeller control should be moved to full "DECREASE RPM" and then set if any control is avilable. Airspeed should be reduced and throttle used to maintain a maximum of 2700 RPM.


Tell me about the landing gear.

The Seminole is equipped with hydraulically actuated, electrically activated, fully retractable, tricycle-type landing gear. Hydraulic pressure for gear operation is provided by an electrically powered, reversible hydraulic pump. The gear is held in the up posiiton solely by hydraulic pressure. Springs assist in gear extension and in locking the gear in the down position. After the gear is down and the downlock hooks engage, springs maintain force on each hook to keep it locked until it is released by applying hydraulic pressure with the gear selector.

A gear warning system is activated under any of the following conditions:

  1. The gear is not locked down with the throttle lever positioned below approximately 15" manifold pressure (MP) on one or both engines.
  2. The gear is not locked down with wing flaps selected to 25 degrees or 40 degrees.
  3. The gear handle is in the up position on the ground (tested only by authorized maintenance personnel).

Gear retraction on the ground is prevented by a squat switch located on the left main landing gear. On the ground, the switch is open, preventing electrical current from reaching the hydraulic pump. Once airborne, the strut becomes fully extended, closing the switch that allows current to reach the hydraulic pump.

In the event of a hydraulic malfunction, the landing gear may be extended by the use of the red emergency gear extension knob. After placing the gear selector in the down position, pulling the red emergency gear extension knob releases the hydraulic pressure which is holding the gear in the up position and allows the gear to free-fall down. The positive gear down indication is 3 green lights. Emergency gear extension is limited to a maximum of 100 KIAS due to air-load on the nose gear. When dealing with a suspected landing gear problem, it is important to verify the position of the navigation light switch. This switch will cause the green lights to be dimmed and, in some cases, make them impossible to see during the day. As with any emergency or abnormality, always refer to the appropriate checklist.

The nose wheel is steered through the use of the rudder pedals and is steerable 30 degrees either side of center.


Tell me about the brakes.

The seminole is equipped with hydraulically actuated disk brakes on the main landing gear wheels. Braking is accomplished by depressing the tops of the rudder pedals. The hydraulic system for the brakes is independent of that for the landing gear. The brake fluid reservoir for servicing is located in the nose cone. To set the parking brake, hold the brakes and pull the black parking brake knob. (The parking brake is not to be used in training or flight checks with ATP.)

All ATP Seminoles are equipped with heavy duty brakes. Refer to the POH to make the required adjustment to performance calculations.


Tell me about the flaps.

The Seminole is equipped with a manual flap system. The flaps are extended with a lever located between the two pilot seats. Flap settings are 0, 10, 25, and 40 and are spring-loaded to return to the 0 position.

Flaps 25 causes a gear warning indication if the gear is not down.


Tell me about the vacuum pumps.

The Seminole is equipped with two engine-driven vacuum pumps, which are located on the back of both engines. The vacuum system operates the attitude gyro and, on aircraft without slaving mechanisms installed, the HSI. Suction limits are 4.8 to 5.2 inches of mercury at 2000 RPM. The failure of a vacuum pump is indicated by an annunciator panel light and a red, pump inoperative indicator on the vacuum gauge. In most circumstances, the failure of one pump alone will not cause the loss of any instruments because the remaining pump should handle the entire vacuum demand.


Tell me about the pitot static system.

The heated pitot tube and static port are located underneath the left wing. An alternate static source is located inside the cabin under the left side of the instrument panel for use in the event of static port blockage. When using the alternate static source, the storm window and cabin vents must be closed and the heater and defroster must be turned on. This will reduce the pressure differential between the cockpit and the atmosphere, reducing pitot static error. The pitot static instrument are the airspeed indicator, altimeter, and VSI.


Tell me about the fuel system.

The Seminole, which uses 100 low lead avgas (blue), is equipped with two 55-gallon bladder nacelle tanks. One gallon is unsuable in each tank. There are two engine-driven and two electrically driven fuel pumps. The electric fuel pumps are used for engine state, takeoff, landing, and fuel selector changes. ATP uses the electric fuel pumps for in-flight maneuvers, except for steep turns.

The aircraft is equipped with a three-position fuel selector for each engine. The positions are "ON", "OFF", and "X-FEED" (cross feed). The fuel selectors remain in the "ON" position during normal operations, and each engine draws fuel from the tank on the same side as the engine. When "X-FEED" is selected, the engine draws fuelk from the tank on the opposite side. Fuel cannot be transferred from tank to tank. Crossfeed operation is limited to straight and level flight only.

The correct procedure for crossfeed operations to supply the left engine with fuel from the right tank is:

  1. Left engine electric boost pump on.
  2. Left fuel selector selected to "X-FEED."
  3. Check left fuel pressure.
  4. Left engine electric boost pump off.
  5. Check fuel pressure.



Tell me about the electrical system.

The Seminole is equipped with a 14-volt electrical direct current system which utilizes push-pull type circuit breakers; a 12-volt, 35 amp hour battery; and two 70-amp, engine-driven alternators. Voltage regulators maintain constant 14-volt output from each alternator at varying engine RPMs, effectively sharing the electrical load. Loss of one alternator is indicated by an annunciator light and a zero indication on the loadmeter. The remaining alternator will normally provide adequate electrical power. 

An over-voltage relay in each alternator circuit provides system protection by taking an alternator offline if its output exceeds 17-volts. If this occurs, the ALT annunciator will illuminate. The battery is used as a source of emergency electrical power and for engine starts. High drain items include the lights, vent fan, heater, gear hydraulic pump, radios, and PFM/MFD (if applicable). If an electrical problem arises, always check circuit breakers. If a circuit breaker is propped, reset only one time.


Tell me about the heater.

Hat to the cabin is supplied by a Janitrol gas combustion heater located in the nose compartment. Air from the heater is distributed by a manifold to the ducts along the cabin floor to outlets at each seat and to the defroster outlet. Operation of the heater is controlled by a three-position switch located on the instrument panel labeled "CABIN HEAT", "OFF", AND "FAN." Airflow and temperature are regulated by the right of the switch: "AIR INTAKE", "TEMP", and "DEF."
For cabin heat, the "AIR INTAKE" lever must be fully open and the "CABIN HEAT" switch on. This simultaneously starts fuel flow and ignites heater. During ground operation, it also activates the ventilation blower. When cabin air reaches the temperature selected on the "TEMP" lever, ignition of the heater cycles automatically to maintain the selected temperature.

Two safety switches located on the front of the heater unit prevents both fan and heater operation when the air intake lever is in the closed position. When the heater is on, a ventilation blower actuates any time the landing gear is extended. In flight, a micro switch, which actuates when the gear is retracted, turns off the ventilation blower so that the cabin air is circulated by ram air pressure only.

An overheat switch in the heater acts as a safety device to render the heater inoperative if a malfunction should occur. Should the switch deactivate the heater, the red "HEATER OVER TEMP" annunciator light on the instrument panel will illuminate. The overheat switch is located on the aft inboard end of the heater vent jacket. A red reset button is located on the heater shroud in the nose cone compartment.

To prevent activation of the overheat switch upon normal heater shutdown during ground operation, turn the three-position switch to "FAN" for two minutes with the air intake lever in the open position before turning the switch off. During flight, leave the air intake open for a minimum of 15 seconds after turning the switch to off.

Fuel is supplied to the heater at a rate of 1/2 gallon per hour from downstream of the left fuel selector and filter.

To introdduce outside, unheated air into the cabin during flight, the "AIR INTAKE" lever should be open and the "CABIN HEAT" off. A fresh air blower is installed to provide airflow during ground operation. It is operated by a high/low blower fan switch.


Tell me about the stall warning horn.

The Seminole is equipped with two electric stall detectors located on the left wing. The inboard detector provides stall warning at flaps 25 or 40 and the outboard at flaps 0 or 10. The purpose of the two tabs is to provide adequate stall warning at varied angles of attack. The electric stall tabs are deactivated on the ground through the use of the squat switch on the left main landing gear.


Tell me about the emergency exit.

The emergency exit is the pilot's left side window. Use the emergency exit when on the ground and the main entry door is unavailable due to fire, ect. The emergency exit release handle is located beneath the thermoplastic cover on the vertical post between the first and second left side windows. To exit the aircraft, remove the thermoplastic cover, pull the release handle forward and then push the window out. The window then will fall free from the fuselage.


Tell me about the navigation system.

The 2012 and later model Piper Seminoles are equipped with the (dual) Garmin G500 electronic flight deck. There are also two G430s.