Aircraft Performance
Understand density altitude, weight & balance, takeoff and landing distances, and performance chart interpretation.
Overview
Aircraft performance determines what your aircraft can do under specific conditions. This area covers the factors that affect performance (density altitude, weight, temperature, wind), weight and balance calculations, takeoff and landing distance computations, and how to read performance charts from the POH.
Why This Matters
Performance calculations are used before every flight. Incorrectly calculating takeoff distance or ignoring density altitude has caused numerous accidents. The FAA tests this to ensure pilots can determine whether a flight is safe under the given conditions.
Exam Weight
Expected Questions
5-8 questions
Difficulty
Moderate to High
Notes
Expect weight and balance problems, takeoff/landing distance calculations from charts, and density altitude effects. Bring your calculator and E6B.
Key Concepts
The 6 essential concepts you need to understand for this topic.
Density Altitude
Density altitude is pressure altitude corrected for non-standard temperature. High density altitude = reduced performance. Hot, high, and humid all increase density altitude. A 7,000-foot airport on a hot day could have a density altitude of 10,000+ feet, drastically increasing takeoff distance.
Weight and Balance Calculations
Weight and balance ensures the aircraft is within its operating limits. Calculate total weight (must not exceed max gross) and CG position (must be within forward and aft limits). Moment = weight × arm. CG = total moment / total weight.
CG Effects on Performance
Forward CG increases stability but requires more elevator authority, increases stall speed, and increases fuel consumption. Aft CG decreases stability (potentially dangerously), reduces stall speed, and improves fuel efficiency. Outside CG limits can make the aircraft uncontrollable.
Takeoff Distance Factors
Takeoff distance increases with: higher density altitude, higher gross weight, tailwind, uphill runway gradient, and soft/wet runway surfaces. A headwind reduces takeoff distance. Always use the POH performance charts for the specific conditions.
Landing Distance Factors
Landing distance increases with: higher density altitude, higher approach speed, tailwind, downhill runway gradient, and wet/contaminated surfaces. Higher weight increases both approach speed and stopping distance.
Performance Chart Interpretation
POH performance charts give takeoff/landing distance, climb rate, and cruise performance for specific conditions. You must interpolate between values and apply all corrections. The FAA expects precise chart reading — no shortcuts or estimates.
Common Mistakes
Confusing pressure altitude with density altitude — pressure altitude doesn't account for temperature; density altitude does.
Making weight and balance arithmetic errors — double-check every calculation, especially moment computations.
Forgetting to add the 50-foot obstacle clearance distance to takeoff and landing rolls when the chart provides separate values.
Underestimating the compounding effect of multiple adverse conditions (hot + high + heavy + tailwind).
Using sea-level performance numbers at a high-altitude airport — always use the chart for actual conditions.
Study Tips
Practice weight and balance problems until the process is automatic — these are guaranteed exam questions.
Learn to use the E6B for density altitude calculations — it's faster and more reliable than mental math.
Work through POH-style performance charts with different input conditions to build speed and accuracy.
Remember the rule of thumb: for every 1,000 feet of density altitude increase, takeoff distance increases roughly 10%.
Practice converting between pressure altitude and density altitude — both directions.
FAA References
Pilot's Handbook of Aeronautical Knowledge (PHAK)
Chapter 11 — Aircraft Performance
Pilot's Handbook of Aeronautical Knowledge (PHAK)
Chapter 10 — Weight and Balance
Sample Questions
Test your knowledge with these representative questions from the FAA exam.
1. What effect does high density altitude have on aircraft takeoff performance?
Explanation: High density altitude means thinner air, which reduces engine power output and lift production. Both effects increase the takeoff distance required.
2. If the CG is located aft of the aft limit, the aircraft will:
Explanation: An aft CG beyond limits reduces longitudinal stability. The aircraft may become difficult or impossible to recover from unusual attitudes. This is a dangerous condition that must be avoided.
3. When calculating weight and balance, the moment is equal to:
Explanation: Moment = Weight × Arm. The CG is then calculated as Total Moment / Total Weight. This is the fundamental formula for all weight and balance computations.
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