Understanding Primary and Secondary Flight Controls: Ailerons, Rudder, and Trim Systems

1. Controls, Systems, Instrumentation 2 February 2005

2. Primary Flight Controls

3. Ailerons • Control bank • Use of ailerons requires increased (up) elevator…why? • Create adverse yaw

4. 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.

5. Adverse Yaw • Primary means of controlling yaw: rudder • Engineering factors: • Differential ailerons • Frise-type ailerons • Coupled ailerons and rudder

6. Elevator • Controls angle of attack • Controls pitch about the lateral axis • Aft-movement of elevator = “up elevator”

7. Miscellany • Other (less common) airplane designs • T-tail • Stabilator • Canard • V-tail

8. Secondary Flight Controls • Primarily: • Flaps • Trim systems • But also… • Slots • Slats • Spoilers

9. 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

10. Trim tabs Reduce workload Elevator trim can maintain a constant angle of attack (read: airspeed) Rudder/aileron trims available on more advanced aircraft Trim systems

11. Aircraft Systems • Powerplant • Propeller • Induction • Ignition • Fuel • Landing Gear • Etc.

12. 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

13. Intake Intake valve opens Piston moves away from top of cylinder and takes in fuel/air mixture Powerplant – Four Strokes

14. Compression Intake valve closes Piston returns to the top of the cylinder Fuel/air mixture is compressed Powerplant – Four Strokes

15. 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

16. Exhaust Exhaust valve opens Burned gases are forced out Cycle complete! (Repeat ~500-2500 times a minute) Powerplant – Four Strokes

17. 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 ignitefuel from both sides ofthe cylinder, creatingmore even combustion

18. Induction Systems • Induction systems bring in fuel and air • Two principal types: • Carburetor induction • Fuel injection

19. 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

20. Fuel injection systems • Found on newer aircraft • Fuel and air are mixed immediately prior to entering the cylinder

21. 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.

22. Engine Troubles • Carburetor Ice • Detonation • Preignition

23. 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.

24. Carburetor Ice • Carb heat causes intake air to be warmer, thus less dense. • Mixture will need to be adjusted • Fuel-injected systems haveno carburetor, thus nocarb ice.

25. 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

26. 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

27. 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 Fuel systems

28. 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!

29. 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

30. Other Systems: • Generally airplane-specific (not on FAA knowledge test): • Environmental • Landing gear • Electrical • Starting • Hydraulics • Advanced aircraft: • Pressurization • Oxygen • Deicing

31. Next Week… • Instrumentation • (PHAK chap. 6) • Regulations • (FAR/AIM & Test Prep)