Load factor in turns

Load factor (n): load wings carry / actual weight (TP 1102).

• n = 3: structure carries 3x gross weight, 3 Gs.
• Rough estimate in a manoeuvre: how hard pressed into the seat (TP 1102).

Level turn load factor by bank (TP 1102):

• Formula: n = 1 / cos φ (φ = bank angle). Steeper bank tilts lift sideways, so more total lift needed to hold weight.
• n depends on bank alone, not airspeed: faster aircraft turns at slower rate at given bank, n unchanged (PHAK).
• Level 90° bank impossible: n goes to infinity as φ approaches 90° (TP 1102).
• Pull-up: abrupt pull-up loads wing above 1 G (TP 1102).
• Push-over or bunt: negative G (TC AIM AIR).

Judging load factor (PHAK):

• Control-column pressure is not a reliable index: control-system leverage (balanced vs. unbalanced control surfaces) differs between aircraft types.
• Most cases: experienced pilot judges by seat pressure.
• Accelerometer measures directly, but uncommon in general aviation training aircraft.

Resultant in coordinated, constant-altitude turn (PHAK): load factor is the resultant of centrifugal force and weight.

• At 60° bank: centrifugal force is 1.73 G, gravity is 1 G, giving resultant load factor 2 Gs.

Steep-turn risk (PHAK, TP 1102):

• Inadvertent stall: rising load factor in steep turn or spiral can stall aircraft well above 1 G stall speed. Intentional stall above design manoeuvring speed (Va) imposes tremendous load factor (TP 1102, line 573).
• Practical max bank: conventional light aircraft, sustained coordinated level turn: approx 60°. Each 10° beyond that adds roughly 1 G, nearing point where structural damage may occur (TP 1102).
• Accident pattern: sudden, unexpected loss of control has caused many accidents, esp. steep turn or abrupt back-elevator near ground, where little height to recover.

Trap: 60° answer is the resultant, 2 Gs, not the 1.73 G centrifugal force alone.

Practice