Limitations and flight envelope
Overview
Limitations and the flight envelope tests certification limits, V speeds and the structural envelope.
Core rules
- Key V speeds: V_S, V_S0, V_A, V_NO, V_NE, V_FE, V_LE, V_LO, V_MC and V_MO/M_MO.
- The V-n diagram shows the manoeuvre envelope: stall boundary, limit load factors and ultimate load factors (1.5 × limit).
- Certification categories: normal +3.8/−1.52 g; utility +4.4/−1.76 g; aerobatic +6.0/−3.0 g.
- V_A is the design manoeuvring speed; it decreases with weight, so it is not a constant.
- V_NE is an IAS limit and should not be exceeded in any operation; M_MO limits high-altitude flight.
- Flutter, fatigue and gust loads define margins beyond the steady envelope.
Worked example
A normal-category aircraft has limit load +3.8 g and ultimate +5.7 g. At 1,200 kg, limit lift = 3.8 × 11,772 = 44,734 N. At V_A, full elevator deflection reaches this limit without structural damage.
Traps
- V_A does not protect against gusts above the design gust speed.
- Exceeding V_NE even briefly can cause flutter or structural failure.
- V speeds are IAS unless stated otherwise.