Chapter 3 - Flight Performance and Planning

These notes are exam-focused for CASA PPL performance/planning. Use aircraft-specific POH/AFM charts and CASA regulatory assumptions exactly as stated in each scenario.

3.1 Performance Fundamentals

• Aircraft performance depends on four main groups:
  • Aerodynamics (lift/drag)
  • Propulsion (engine/propeller efficiency)
  • Environment (pressure altitude, temperature, wind, runway condition)
  • Mass/configuration (weight, CG, flap/gear state)
• Never use rule-of-thumb when a chart/table is provided.

3.2 Density Altitude and Why It Matters

• High density altitude reduces:
  • Engine power
  • Propeller thrust
  • Wing lift at a given IAS (longer takeoff/landing distance due to TAS/ground speed effects)
• Typical causes: high temperature, high elevation, low pressure.
• Operational result:
  • Longer takeoff roll
  • Poorer climb rate and climb gradient
  • Reduced obstacle clearance margin.

3.3 Takeoff Performance

• Inputs to chart calculations commonly include:
  • Pressure altitude
  • OAT
  • Aircraft weight
  • Wind component
  • Runway slope/surface
  • Flap setting and obstacle requirement
• Distinguish:
  • Ground roll
  • Distance to 50 ft obstacle
• Apply corrections in required sequence per POH.

High-yield planning checks

• Accelerate-stop and reject decision awareness (conceptual for PPL).
• Crosswind component compared against demonstrated or operational limits.
• Abort criteria before takeoff briefing.

3.4 Climb and En Route Performance

• Best angle (VX) vs best rate (VY) purpose and trade-offs.
• Climb performance degrades with:
  • Altitude and temperature
  • Higher weight
  • Incorrect speed/mixture settings.
• Cruise planning:
  • TAS from performance chart
  • Fuel flow at selected power setting
  • Endurance and range computation.

3.5 Landing Performance

• Inputs similar to takeoff charts:
  • Weight
  • Pressure altitude
  • Temperature
  • Wind
  • Surface/slope
  • Flap/configuration
• Distinguish:
  • Landing ground roll
  • Distance over threshold obstacle.
• Add practical margins for runway condition, approach stability, and pilot technique variation.

3.6 Weight and Balance (W&B)

• Core formulas:
  • Moment = Weight x Arm
  • CG = Total Moment / Total Weight
• Verify:
  • MTOW and landing weight limits
  • Baggage/compartment limits
  • CG within envelope at each stage (takeoff/landing)
• Fuel burn shifts CG; check both departure and arrival conditions.

CASA workbook exam convention

• AVGAS specific gravity commonly assumed as 0.72 kg/L in exam workbook contexts.

3.7 Fuel Planning and Reserves

• Fuel planning combines:
  • Taxi/start allowance
  • Trip fuel
  • Reserve/legal minima
  • Contingency/diversion as required by scenario
• Differentiate:
  • Fuel required by regulation
  • Operationally prudent uplift.
• For exam questions, apply stated policy basis (e.g., Part 91 assumptions if specified).

3.8 Navigation Log and Time/Fuel Management

• Standard nav log workflow:
  • Leg distances/tracks
  • Wind correction and groundspeed
  • ETE/ETA
  • Fuel burn per leg
  • Cumulative fuel and reserves
• In-flight updates:
  • Revise ETA/fuel on actual groundspeed
  • Decide early on diversions using updated endurance.

3.9 ETP/PNR and Diversion Concepts (PPL level)

• PNR: point where continuing and returning have equivalent limiting resource outcome (often fuel/time logic).
• ETP: equal-time point between two alternates or destinations.
• These are planning/risk tools that help trigger timely diversion decisions.

3.10 Key Definitions and Practical Examples

• Density altitude: pressure altitude corrected for non-standard temperature; indicates “how the aircraft feels” aerodynamically.
  • Example: hot day at inland aerodrome can create DA much higher than field elevation, degrading climb.
• Takeoff distance over 50 ft: total distance from brake release to crossing 50 ft.
  • Example: runway that appears long enough for ground roll may still be insufficient for obstacle-clearance requirement.
• CG envelope: approved center-of-gravity range for safe controllability/stability.
  • Example: aft-loaded aircraft may rotate easily but become unstable and harder to recover near stall.
• Reserve fuel: legally required minimum fuel carried beyond trip fuel.
  • Example: if forecast headwind increases en route, reserve may be eroded and diversion should be made early.
• Crosswind component: wind component perpendicular to runway heading.
  • Example: runway headwind may still include high crosswind that exceeds pilot or aircraft limits.

Scenario: high DA departure decision

• Planned departure at midday, high temperature, near-max weight, rising terrain ahead.
• Safer action: reduce weight and/or depart in cooler period, then recompute takeoff and climb gradient using POH charts.

3.11 Common Exam Traps

• Mixing units (kg/lb, L/gal, kt/km/h, ft/m).
• Using IAS when TAS/GS is required for timing.
• Applying wind correction sign incorrectly (headwind/tailwind).
• Forgetting slope/surface corrections.
• Checking CG only at departure, not at landing.
• Confusing legal reserve with target reserve.

3.12 Rapid Revision Checklist (Pre-Exam)

• Can compute takeoff and landing distance from a multi-step chart.
• Can explain density altitude impact without memorized myths.
• Can complete W&B and verify CG at all stages.
• Can produce a full nav log with fuel/endurance checks.
• Can apply stated legal fuel policy assumptions in scenario questions.

References (Primary)

• FAA PHAK (especially performance and W&B chapters): https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak
• CASA RPL/PPL/CPL Aeroplane Workbook: https://www.casa.gov.au/rpl-ppl-and-cpl-aeroplane-workbook