Chapter 3 - Flight Performance and Planning

Chapter 3

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).

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.

3.13 Formula Pack and Graphics

Core formulas

\[\text{Time (hr)} = \frac{\text{Distance (NM)}}{\text{GS (kt)}}\] \[\text{Fuel Used} = \text{Fuel Flow} \times \text{Time}\] \[\text{Groundspeed} = \frac{\text{Distance}}{\text{Time}}\] \[\text{Moment} = \text{Weight} \times \text{Arm}\] \[\text{CG} = \frac{\sum \text{Moments}}{\sum \text{Weights}}\]

Useful conversion and planning formulas

\[\text{Fuel Mass (kg)} \approx \text{Fuel Volume (L)} \times \text{SG}\]

For CASA workbook style AVGAS assumptions:

\[\text{Fuel Mass (kg)} \approx \text{Fuel Volume (L)} \times 0.72\]

Graphic: performance planning flow

flowchart LR
    A[Weather and runway data] --> B[Takeoff and climb check]
    B --> C[En route TAS, GS, fuel flow]
    C --> D[Landing performance check]
    D --> E{Margins acceptable?}
    E -- Yes --> F[Dispatch]
    E -- No --> G[Reduce weight, delay, or reroute]

Performance sensitivity table

Parameter change	Takeoff roll	Climb rate	Landing distance
Higher temperature	Increases	Decreases	Usually increases
Higher pressure altitude	Increases	Decreases	Usually increases
Higher weight	Increases	Decreases	Increases
Tailwind	Increases significantly	N/A climb after takeoff	Increases significantly
Wet/soft runway	Increases	N/A	Increases

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
ICAO Doc 8168 (PANS-OPS, procedural context): https://www.icao.int/
EASA Easy Access Rules (Air Operations): https://www.easa.europa.eu/en/document-library/easy-access-rules

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