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Private pilot · ACS PA.I.F · lesson pack

Performance and Limitations

Why this one matters

Many takeoff accidents happen in airplanes that were overweight, out of balance, or asked to perform at a hot, high field beyond what the numbers allowed. Doing the weight and balance and the performance calculations honestly, with margin, is how you find out on the ground, not at the end of the runway.

1 · Know these cold

  • •Before flight you must know the runway lengths and the takeoff and landing distances: from the approved AFM where one is required, otherwise other reliable information for the airplane, corrected for elevation, runway slope, weight, wind and temperature.(14 CFR 91.103(b)(1)-(2))
  • •Density altitude is pressure altitude corrected for nonstandard temperature. High, hot and humid means less lift, less power and longer takeoff and landing.(PHAK (FAA-H-8083-25C), Aircraft Performance)
  • •CG = total moment / total weight, and moment = weight × arm. The CG must stay within limits for takeoff, en route and landing.(Aircraft Weight and Balance Handbook (FAA-H-8083-1B))
  • •A forward CG raises the stall speed and makes the flare harder; an aft CG makes the airplane less stable and stall/spin recovery harder.(Aircraft Weight and Balance Handbook (FAA-H-8083-1B))
  • •Performance charts come from a new airplane in good condition flown with average piloting skill. Below-average technique or a tired airplane does worse, so set a written personal margin.(PHAK (FAA-H-8083-25C), Aircraft Performance)
  • •Know the V-speeds and the airspeed indicator markings: white arc (flaps), green arc (normal), yellow arc (caution), red line (never exceed).(PHAK (FAA-H-8083-25C), Aerodynamics of Flight)
  • •Maneuvering speed decreases as weight decreases.(PHAK (FAA-H-8083-25C), Aerodynamics of Flight)

2 · The lesson

Using the charts
  • The POH has charts and tables for takeoff and landing distance (ground roll and over a 50-foot obstacle), climb, cruise, fuel and density altitude.(PHAK (FAA-H-8083-25C), Aircraft Performance)
  • Read them with the right inputs: pressure altitude, temperature, weight, wind and runway surface. Interpolate between lines; don't round in your favor.(PHAK (FAA-H-8083-25C), Aircraft Performance)
  • Apply the notes on the chart: headwind and tailwind corrections, grass runways, flap settings and technique assumptions.(PHAK (FAA-H-8083-25C), Aircraft Performance)
What changes performance
  • Density altitude: pressure altitude (altimeter set to 29.92) corrected for temperature. Standard is 15°C at sea level, decreasing about 2°C per 1,000 feet. Humidity makes it worse.(PHAK (FAA-H-8083-25C), Aircraft Performance)
  • Weight: heavier means longer takeoff and landing, slower climb and higher stall speed.(PHAK (FAA-H-8083-25C), Aircraft Performance)
  • Wind: a headwind shortens takeoff and landing distances; a tailwind lengthens them a lot.(PHAK (FAA-H-8083-25C), Aircraft Performance)
  • Runway: grass, soft, wet or upsloping runways lengthen takeoff; downslope lengthens landing.(PHAK (FAA-H-8083-25C), Aircraft Performance)
  • Pilot technique and configuration: the charts assume the POH technique and flap setting. Different technique gives different numbers.(PHAK (FAA-H-8083-25C), Aircraft Performance)
  • The book numbers come from a new airplane in good working order flown with average piloting skill. A worn engine, a dirty airframe or below-average technique does worse.(PHAK (FAA-H-8083-25C), Aircraft Performance)
  • Make the margin a rule, not a feeling: for example, the factored takeoff or landing distance must fit well inside the runway available (a written personal minimum). Apply the POH wind corrections as published: tailwind penalties are larger than headwind credits and often capped, so never assume they are symmetric.(PHAK (FAA-H-8083-25C), Aircraft Performance)
  • Configuration is a performance factor too: flaps and gear change lift, drag and stall speed, and each chart is valid only for the configuration and technique it states. VX (best angle), VY (best rate) and best glide come from the same performance data.(PHAK (FAA-H-8083-25C), Aircraft Performance)
Weight and balance
  • Moment = weight × arm. Add up the weights and moments, then CG = total moment / total weight.(Aircraft Weight and Balance Handbook (FAA-H-8083-1B))
  • Check against the CG envelope at takeoff and landing; burning fuel moves the CG.(Aircraft Weight and Balance Handbook (FAA-H-8083-1B))
  • Out of limits? Move weight (baggage forward, a heavier passenger in front), offload weight, or carry less fuel if the trip allows.(Aircraft Weight and Balance Handbook (FAA-H-8083-1B))
  • Shifting weight: weight moved / total weight = change in CG / distance moved.(Aircraft Weight and Balance Handbook (FAA-H-8083-1B))
  • Forward CG: more stable, higher stall speed, heavier elevator, harder flare. Aft CG: less stable, lighter elevator, harder stall and spin recovery.(Aircraft Weight and Balance Handbook (FAA-H-8083-1B))
Limitations and aerodynamics
  • Airspeed markings: white arc from VS0 to VFE (flap range); green arc from VS1 to VNO (normal); yellow arc from VNO to VNE (smooth air only); red line at VNE.(PHAK (FAA-H-8083-25C), Aerodynamics of Flight)
  • Maneuvering speed (VA): at or below it, a single flight control moved once to full deflection, in one axis, in smooth air, won't overstress the airplane. It doesn't protect against repeated or reversing inputs, several axes at once, or inputs combined with gusts. It decreases with weight (VA × √(actual weight ÷ maximum weight)) and isn't marked on the airspeed indicator.(PHAK (FAA-H-8083-25C), Aerodynamics of Flight)
  • Load factor is lift divided by weight: 2 G in a level 60° bank, and the stall speed rises with its square root (about 41% at 2 G). Typical limit load factors are +3.8/-1.52 G (normal) and +4.4/-1.76 G (utility), but your POH/AFM governs, and utility limits apply only when loaded and flown in the utility envelope.(PHAK (FAA-H-8083-25C), Aerodynamics of Flight; 14 CFR 91.9)
  • Ground effect within about one wingspan of the runway reduces induced drag: the airplane can lift off before it can climb, or float on landing.(PHAK (FAA-H-8083-25C), Aerodynamics of Flight)
  • Operating limitations in the POH, placards and markings are mandatory.(14 CFR 91.9)
Worked examples
  • Density altitude, step by step: get pressure altitude (set 29.92 and read the altimeter, or correct field elevation for the altimeter setting), then use the POH chart, or estimate about 120 feet per °C above standard. At a 4,000-foot field (pressure altitude about 4,000) and 35°C, standard is about 7°C, so it is 28°C hotter: about 4,000 + 28 × 120 ≈ 7,400 feet density altitude.(PHAK (FAA-H-8083-25C), Aircraft Performance)
  • What that means: the same indicated airspeeds, but higher true airspeed and groundspeed on takeoff and landing, a longer roll and a poor climb gradient; lean for best power per the POH. POH charts make no humidity correction, so on a humid day the numbers are optimistic.(PHAK (FAA-H-8083-25C), Aircraft Performance)
  • Reading a takeoff chart (example numbers, not for any specific airplane): at 4,000 feet pressure altitude the table gives 1,400 feet to clear 50 feet at 20°C and 1,550 at 30°C, so at 25°C interpolate to about 1,475. Then apply the chart's own wind note, for example minus 10% for each 9 knots of headwind (about 1,330), or plus 10% for each 2 knots of tailwind, and compare with the runway and your personal minimum.(PHAK (FAA-H-8083-25C), Aircraft Performance)
  • Weight and balance terms: the datum is the reference point; an arm (station) is the distance from it; moment = weight × arm; basic empty weight includes unusable fuel and full oil; useful load is what you can add (people, bags, usable fuel). POHs give the CG by computation, a loading graph, or a table.(Aircraft Weight and Balance Handbook (FAA-H-8083-1B))
  • A worked computation (example numbers): empty 1,450 lb at 39.0 in (56,550 lb-in); front seats 340 lb at 37 (12,580); rear seat 150 lb at 73 (10,950); baggage 50 lb at 95 (4,750); fuel 40 gal = 240 lb at 48 (11,520). Takeoff: 2,230 lb, 96,350 lb-in, CG 43.2 in. Burn 20 gal (120 lb, 5,760 lb-in) for landing: 2,110 lb, 90,590 lb-in, CG 42.9 in. Plot both points on the POH envelope.(Aircraft Weight and Balance Handbook (FAA-H-8083-1B))
  • Changing the load: adding or removing weight, new CG = (total moment ± weight × its arm) ÷ new total weight. Shifting weight inside the airplane: weight moved ÷ total weight = CG change ÷ distance moved.(Aircraft Weight and Balance Handbook (FAA-H-8083-1B))
  • Why CG matters: a forward CG needs more tail-down force, so the wing lifts the weight plus that force, raising stall speed and drag and slowing cruise. An aft CG lowers stall speed and speeds cruise, but reduces stability and makes stall and spin recovery harder.(Aircraft Weight and Balance Handbook (FAA-H-8083-1B))
  • Don't trade fuel for payload down to the 91.151 minimum (30 minutes by day), and treat every split load or "two trips" plan as a new weight-and-balance and performance calculation.(14 CFR 91.151; PHAK (FAA-H-8083-25C), Weight and Balance)

Want it all on one page, with scenarios? Read the full lesson.

3 · Say it out loud

Answer each one out loud, then check yourself and mark how it went.

  1. Remember Recall it

    “What is density altitude?”

  2. Understand Explain why

    “Why does a forward CG raise the stall speed?”

  3. Apply Use it on a flight

    “It's 35°C at a field 4,000 feet high, with a 2,500-foot runway. What do you do before deciding to go?”

4 · Common mistakes

  • Checking weight and balance only at takeoff.

    Fuel burn moves the CG, sometimes out of limits.

    Instead: Check the landing CG too.

  • Taking chart numbers at face value.

    They assume a new airplane in good condition and average technique.

    Instead: Set a written personal minimum, such as factored distance well inside the runway available.

  • Using indicated altitude for performance.

    Performance depends on density altitude.

    Instead: Get pressure altitude (set 29.92) and correct for temperature.

5 · Quick check

Answer, then reveal. Flag anything you want to see again.

  1. 1. How do you find the CG?

  2. 2. What three conditions make density altitude high?

  3. 3. What does the yellow arc mean?

  4. 4. Does VA go up or down as the airplane gets lighter?

  5. Scenario5. With a 10-knot tailwind, would you expect takeoff distance to be longer or shorter than the no-wind chart value?

  6. 6. What are the limit load factors for a normal category airplane?

Trained it? Now prove it: practice performance and limitations out loud with our examiner.

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Connect it

One situation that runs across this lesson and its neighbors in the same ACS area. Decide first, then check.

Connect it · Preflight Preparation

A July afternoon. You plan a 90 NM trip from a 2,800-foot runway at 1,500 feet elevation; it's 33 °C. The destination TAF has a TEMPO for thunderstorms starting about when you'd arrive.

How do the weather, the airplane's performance and your fuel plan change one another, and what do you decide? Decide, then see the worked answer

Work the density altitude first. Standard temperature at 1,500 feet is about 12 °C, so 33 °C is about ISA +21 °C and the density altitude is roughly 4,000 feet (more if the pressure is low). Enter the POH takeoff and climb charts at the actual pressure altitude and temperature, never the field elevation, and compare the ground roll, the distance over a 50-foot obstacle and the climb with the 2,800 feet and the obstacles, with a margin. If it's tight, cut payload and baggage first. Never cut fuel below trip fuel plus fuel to divert to an alternate plus the 91.151(a)(1) day VFR reserve of 30 minutes at normal cruise. After any load change, recompute the weight and balance and the CG, and check the landing distance at the destination too. The TEMPO puts thunderstorms over the destination at your arrival. Don't plan to beat the TEMPO window or to divert closely around cells: avoid thunderstorms with severe or intense radar echoes by at least 20 miles, never take off or land in the face of an approaching thunderstorm, and wait storms out on the ground. With thin performance margins and storms at the far end, the better answer is the cooler, calmer morning.

PHAK (FAA-H-8083-25C), Aircraft Performance and Weather Theory; AC 00-24C, Thunderstorms; 14 CFR 91.103, 91.151

Brings together: Weather Information · Cross-Country Flight Planning · Performance and Limitations

Teaching this? The instructor lesson plan →

Study aid, not FAA guidance. Sources: Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C); Aircraft Weight and Balance Handbook (FAA-H-8083-1B); 14 CFR 91.9, 91.103; Your airplane's POH/AFM. Checked against current sources 2026-11-12.