Performance and Limitations

Q: Takeoff Distance Factors

FactorChangeEffect on T/O dist Headwind +10 ktsTypical↓ ~10% Tailwind +2 ktsTypical↑ ~10% Altitude +1,000 ft DA—↑ ~3–4% Temperature +18°F—↑ ~3–4% Weight +10%—↑ ~20% Grass runwayShort/firm↑ ~7% Grass runwayLong/wet↑ 25–50% Uphill 2° slope—↑ ~10% POH charts assume: paved, level, dry runway; sea level; standard temperature; perfect technique; maximum certified gross weight. Add safety margins for real-world conditions.

Q: Airspeed Markings — Full Reference

SpeedMeaningASI color Vs0Stall, gear/flaps downBottom of white arc Vs1Stall, clean configBottom of green arc VfeMax flap extensionTop of white arc VnoMax structural cruiseTop of green arc VneNever exceedRed radial VaManeuvering speedNot marked VxBest angle of climbNot marked VyBest rate of climbNot marked Vg/VbgBest glideNot marked Va decreases as weight decreases. A lighter aircraft needs less protection — it stalls sooner before structural limits are reached. Always use POH Va for current weight.

Q: Load Factor & Accelerated Stall

LF = 1/cos(bank angle). New stall speed = Vs × √(LF). BankLoad FactorStall speed increase 0°1.00g0% 30°1.15g+7% 45°1.41g+19% 60°2.00g+41% 75°3.86g+97% 80°5.76g+140% A stall at 60° of bank occurs at 41% above the wings-level stall speed. This is why base-to-final stalls are so deadly — the pilot is already at low speed, low altitude, and then adds back pressure in a steep bank.

Private Pilot ACS · Area I · Task F · 14 CFR 61, 14 CFR 91, FAA-H-8083-25

Everything you need to know about Performance and Limitations for your private pilot checkride. Aligned to FAA-S-ACS-6C Task I-F, covering weight & balance, performance charts.

Weight & Balance PHAK Ch.10 §

W&B Calculation — Worked Example §

Formula: Weight × Arm = Moment. Sum all moments ÷ total weight = CG location.

Item	Weight (lbs)	Arm (in)	Moment (in-lbs)
Empty weight	1,620	38.7	62,694
Pilot + front pax	340	37.0	12,580
Rear passengers	160	73.0	11,680
Fuel (40 gal × 6)	240	48.0	11,520
Baggage	40	95.0	3,800
Total	2,400	—	102,274

CG = 102,274 ÷ 2,400 = 42.6 inches from datum
Verify both weight (2,400 lbs ≤ MGW) and CG (42.6 in within envelope) are within limits.

PHAK Ch.10; POH Section 6

CG Effects on Aircraft §

Forward CG: Aircraft nose-heavy. Requires more up-elevator to maintain level flight and to flare for landing. Reduces stall speed slightly (more stable). May be unable to flare in extreme cases — check POH forward limit.

Aft CG (most dangerous): Reduces longitudinal (pitch) stability. Aircraft becomes very sensitive to pitch inputs. Stall recovery may be impossible in extreme cases. Aft of the CG envelope = do not fly under any circumstances.

Fuel burn effect: As fuel burns, CG shifts toward the location of the fuel tanks. If tanks are aft of the loaded CG, CG moves aft during flight. Must verify CG remains in limits at landing weight.

Weight Terms §

Basic Empty Weight (BEW): Airframe + engines + permanently installed equipment + unusable fuel + full operating fluids including full oil. Established at manufacture or after modification.

Maximum Gross Weight (MGW): Maximum total weight certified for the aircraft. Exceeding MGW violates the type certificate and may cause structural failure during landing.

Useful load: MGW − BEW. The total weight available for people, cargo, and fuel.

Payload: Useful load − fuel weight. The people and cargo only.

Ramp weight / Takeoff weight: Some aircraft have separate limits. Ramp weight includes taxi fuel burned before takeoff.

POH; PHAK Ch.10

Performance Charts PHAK Ch.11; POH Ch.5 §

Density Altitude — Why It Matters §

Density altitude (DA) = Pressure altitude corrected for non-standard temperature.

Quick formula: DA ≈ PA + [120 × (OAT°C − ISA°C)]
ISA temperature at sea level = 15°C; lapse rate = 2°C per 1,000 ft.

Example: Airport elevation 5,000 ft MSL. Altimeter 30.12 → PA = 5,000 − 120 = 4,880 ft. OAT = 30°C. ISA at 5,000 ft = 15 − 10 = 5°C. DA = 4,880 + (120 × (30 − 5)) = 4,880 + 3,000 = 7,880 ft DA.

At 7,880 ft DA: the aircraft performs as if it were at 7,880 ft MSL — significantly degraded power, propeller efficiency, and lift. On a hot day at a high-elevation airport, DA can exceed 10,000 ft.

PHAK Ch.11

Takeoff Distance Factors §

Factor	Change	Effect on T/O dist
Headwind +10 kts	Typical	↓ ~10%
Tailwind +2 kts	Typical	↑ ~10%
Altitude +1,000 ft DA	—	↑ ~3–4%
Temperature +18°F	—	↑ ~3–4%
Weight +10%	—	↑ ~20%
Grass runway	Short/firm	↑ ~7%
Grass runway	Long/wet	↑ 25–50%
Uphill 2° slope	—	↑ ~10%

POH charts assume: paved, level, dry runway; sea level; standard temperature; perfect technique; maximum certified gross weight. Add safety margins for real-world conditions.

POH Section 5; PHAK Ch.11

Airspeed Markings — Full Reference §

Speed	Meaning	ASI color
Vs0	Stall, gear/flaps down	Bottom of white arc
Vs1	Stall, clean config	Bottom of green arc
Vfe	Max flap extension	Top of white arc
Vno	Max structural cruise	Top of green arc
Vne	Never exceed	Red radial
Va	Maneuvering speed	Not marked
Vx	Best angle of climb	Not marked
Vy	Best rate of climb	Not marked
Vg/Vbg	Best glide	Not marked

Va decreases as weight decreases. A lighter aircraft needs less protection — it stalls sooner before structural limits are reached. Always use POH Va for current weight.

PHAK Ch.8, Ch.11

Load Factor & Accelerated Stall §

LF = 1/cos(bank angle). New stall speed = Vs × √(LF).

Bank	Load Factor	Stall speed increase
0°	1.00g	0%
30°	1.15g	+7%
45°	1.41g	+19%
60°	2.00g	+41%
75°	3.86g	+97%
80°	5.76g	+140%

A stall at 60° of bank occurs at 41% above the wings-level stall speed. This is why base-to-final stalls are so deadly — the pilot is already at low speed, low altitude, and then adds back pressure in a steep bank.

PHAK Ch.4