Straight and Level The Flight Training Manual - Section 6

Objectives To establish and maintain straight and level flight at: a constant airspeed; constant altitude; in a constant direction; and, in balance. To regain straight and level flight; and, To maintain straight and level flight at selected airspeeds or power settings.

Principles of Flight Straight and Level - Definition Flying Attitude The Four Forces Lift Performance

Straight and Level - Definition For Straight and Level Flight, the aircraft is travelling: in a Constant Direction (straight), at a Constant Altitude (level) and at a Constant Speed i.e. not climbing or descending, and not accelerating. The aircraft is in a state of Equilibrium. Therefore the opposing forces acting on the aircraft must be equal to, and opposite to each other.

Flying Attitude The Horizon All VFR flight references the aircraft’s nose to the horizon The apparent line where the sky meets the sea

The Four Forces LIFT (L) acts upwards through the Centre Of Pressure (CP), perpendicular to the Relative Airflow. LIFT is equal to, and opposite WEIGHT. THRUST (T) acts forwards through the longitudinal axis, and is a result of the engine pulling/pushing the aircraft forwards. WEIGHT (W) acts towards the centre of the earth, through the Centre Of Gravity (CoG). DRAG (D) acts rearwards through the longitudinal axis and is equal to and opposite THRUST.

The Four Forces In comparison: Lift = Weight Lift and Weight are about 10 times greater than Thrust and Drag Thrust = Drag

The Four Forces Centre of Pressure (CP) is usually rearward of CofG. This creates a ‘Pitch Down’ couple. Drag is normally designed to be above the engine Thrust line. This creates a ‘Pitch Up’ couple. Desirable: Any decrease in power will create a pitch down LIFT Pitch Down Pitch Up DRAG THRUST The tailplane is used to balance out any difference in the pitching couples. Usually a small Downward force WEIGHT

Pressure Distribution and Total Resultant Lift Pressure Distribution and Total Resultant Drag Lift Chord Line AOA  RAF

A change in CL, ρ, or V = a change in Lift L = CL½ρV2S CL Coefficient of Lift For a given wing shape and AoA ρ Rho The density of the air V Speed True Airspeed (TAS) S Wing Area - generally constant A change in CL, ρ, or V = a change in Lift

Lift L = CL½ρV2S L  AoA x IAS In Straight and Level for Lift to remain constant: Any change in AoA will have to be counted with a change in IAS, and vice versa. CL equates to AoA () Elevator ½ρV2 equates to IAS

Power + Attitude = Performance 2300 RPM 2/3:1/3 4 Fingers Fist Straight and Level (90kt)

Airmanship LOOKOUT Left to Right (2 seconds per 20°) (90% Outside) VFR (Visual Flight Rules) Class G Airspace, below 3000ft AMSL/1000ft AGL In sight of land / water Remain clear of cloud Visibility 5000m or more Orientation Look for landmarks Training Area boundaries, Airfield?

Aeroplane Management Throttle Positive and smooth movements Mixture Full Rich (significant power changes) Lean below 75% Power Carburettor (Carb) Heat Used for Carburettor Icing – drop in RPM Apply when needed – RPM below 2000RPM Causes a further drop in RPM Temperatures and Pressures (T’s & P’s ) In the Normal Range (Green)

Carburettor Icing Evaporation Temperature Pressure Aeroplane Management Carburettor Icing Evaporation Temperature Pressure

Used to confirm Performance Aeroplane Management Flight Instruments Used to confirm Performance Airspeed Indicator Artificial Horizon Altimeter Turn Coordinator Direction Indicator Vertical Speed Indicator

Human Factors Lookout: Blind spots Pillars, Door frames, Instructor, etc. Lesson Structure: A lot of information Mastery of skills with time and practice

Air Exercise – Horizon Level with: Equidistant with The nose, and The wingtips Instrument Panel

Air Exercise – Establish S & L LOOKOUT Select reference point Nominate altitude Nominate power setting

Air Exercise – Establish S & L P A T Power Attitude Trim Cruise Elevator Relieve Pressure Level attitude C152/PA38 Trim is Your Friend Ailerons (2300 RPM) Wings level Rudder Balance Check Power, Attitude, Trim

Air Exercise – Maintain S &L L A I Lookout Left to Right Attitude Correct Instruments Right to Left Confirmation Change – Hold – Trim – Check

Air Exercise – Regaining S & L Variables Cause Correction Changing Altitude Incorrect Power/Attitude Correct Power Setting and Correct Attitude Incorrect Speed Incorrect Power/Attitude Correct Power Setting & small change to attitude Changing Direction Wings not Level Wings Level plus Constant Direction = In Balance Out of Balance

Air Exercise – Regaining S & L Check Airspeed and Power Setting Set Correct Power Airspeed Decreasing = Increase Power & vice versa Check Nose Attitude Set for Straight and Level Check Wings Level and Balance Ball Centred Level Wings Stand on the Ball Reset Power Check PAT Small altitude adjustment (150ft) use Elevator

Air Exercise – Different Power/Airspeed Power + Attitude = Performance Power Attitude Performance 2300 RPM Normal AoA (4°) 90 knots 1800 RPM High AoA (8°) 70 knots 2500 RPM Low AoA (2°) 110 knots When Changing Power – Counteract Pitch and Yaw