Controls, Systems, Instrumentation 2 February 2005.

Controls, Systems, Instrumentation

2 February 2005

Primary Flight Controls

Ailerons

Control bank Use of ailerons requires increased

(up) elevator…why? Create adverse yaw

Adverse Yaw What happens when an airplane is banking? Left-bank: left aileron up, left wing down.

Right wing has more lift more drag! Airplane tends to yaw in opposite direction

of desired turn. Primary function of the rudder is to control

yaw. Use rudder in the direction of the deflection

of the ailerons while banking, but not while just banked.

Adverse Yaw Primary means of controlling yaw: rudder Engineering factors:

Differential ailerons Frise-type ailerons Coupled ailerons and rudder

Elevator

Controls angle of attack Controls pitch about the lateral axis Aft-movement of elevator = “up

elevator”

Miscellany

Other (less common) airplane designs T-tail Stabilator Canard V-tail

Secondary Flight Controls

Primarily: Flaps Trim systems

But also… Slots Slats Spoilers

Flaps Increase lift by increasing camber Decrease stall speed Increase drag Can be deployed in increments Used to “get down &

slow down” at the sametime

Trim systems Trim tabs

Reduce workload Elevator trim can

maintain a constant angle of attack (read: airspeed)

Rudder/aileron trims available on more advanced aircraft

Aircraft Systems Powerplant Propeller Induction Ignition Fuel Landing Gear Etc.

Powerplant Converts chemical

energy (fuel) to mechanical energy (torque)

Powers propeller and other aircraft systems

Reciprocating engines: four strokes – intake, compression, power, exhaust (“suck, squeeze, bang, blow.”)

Powerplant – Four Strokes Intake

Intake valve opens Piston moves away from top

of cylinder and takes in fuel/air mixture

Powerplant – Four Strokes Compression

Intake valve closes Piston returns to the top

of the cylinder Fuel/air mixture is

compressed

Powerplant – Four Strokes Power

Spark plugs spark Combustion of the

compressed fuel-air mixture forces piston down

(This stage provides the power for all four strokes)

Powerplant – Four Strokes Exhaust

Exhaust valve opens Burned gases are forced

out Cycle complete! (Repeat

~500-2500 times a minute)

Ignition Systems

Magnetos Powered by the engine Electrical failures do not cause ignition failures Most airplanes have “dual mags” – redundancy &

engine performance Two spark plugs ignite

fuel from both sides ofthe cylinder, creatingmore even combustion

Induction Systems

Induction systems bring in fuel and air Two principal types:

Carburetor induction Fuel injection

Carburetor Induction Air moves in through a restriction (venturi) Smaller area increases airspeed and

decreases air pressure (Bernoulli!) Decreased pressure draws fuel into

airstream; circulation mixes the two Manifold distributes mixture to the cylinders

Fuel injection systems

Found on newer aircraft Fuel and air are mixed immediately

prior to entering the cylinder

Induction – “Mixture Control” Both systems must compensate for changes in

the atmosphere. As altitude increases (or air gets warmer), air

density decreases (Geek alert: PV = NRT) A given fuel/air mixture at sea level will have

too much fuel (be too “rich”) at 10,000 feet. A separate mixture control controls the ratio

of fuel to air. As altitude increases, the pilot “leans” the mixture.

Engine Troubles

Carburetor Ice Detonation Preignition

Carburetor Ice As air flows through the neck of the

carburetor it expands and fuel evaporates – the “heat of evaporation” cools the air

Solution: carburetor heat!Air is preheated prior toentering carburetor, eithermelting or preventing ice

Carb ice can occur between20 and 70 deg. F when relative humidity is high.

Carburetor Ice Carb heat causes intake air to be warmer, thus

less dense. Mixture will need to be adjusted Fuel-injected systems have

no carburetor, thus nocarb ice.

Temperature-Related Problems

Detonation Uncontrolled & explosive ignition (rather than

combustion) during the power stroke Caused by:

Too-low grade of fuel Too lean of a mixture Insufficient cooling

Temperature-Related Problems General temperature concerns

Engine oil – not only lubricates, but dissipates heat Aviation fuel – also acts as an internal coolant Airflow – primary method for cooling air-cooled

engines When temperature is a concern:

Reduce power Ensure there is extra oil for greater heat dissipation Enrich mixture (more fuel = more cooling) Increase airflow over engine by

lowering nose during climbs avoiding lengthy ground operations on hot days

Fuel systems Engine-driven fuel pumps

operate constantly (as long as engine is running)

Electric fuel pumps are pilot-controlled – used for priming/starting, critical phases of flight (takeoff / landing) and emergency operations.

Gravity-feed systems use gravity alone to drive fuel

Propellers – Fixed Pitch Propellers have “twist”

to maintain a constantangle of attack acrossthe blade

A given RPM creates different(linear) velocities along prop.

Lift = airspeed x AOA and constant lift is desired… therefore: twist!

Propellers – Constant Speed

Pilot controls separately power (via manifold pressure) and RPMs.

Avoid high MP with low RPMs When increasing power, advance

propeller before advancing throttle When decreasing power, retard throttle

before decreasing propeller

Other Systems: Generally airplane-specific (not on FAA

knowledge test): Environmental Landing gear Electrical Starting Hydraulics

Advanced aircraft: Pressurization Oxygen Deicing

Next Week…

- Instrumentation- (PHAK chap. 6)

- Regulations- (FAR/AIM & Test Prep)