Multi-Engine Aircraft Notes

→ Review

→ VMCA (Air Minimum Control Speed)

Min flight speed at which the airplane is directionally controllable (per FARs).
Certification: one engine inop & windmilling; ≤5° bank towards operative engine; take-off power; gear up; flaps take-off; most aft C.G.
Below VMCA: rolling forces exceed roll control authority.
Coordination: 5° bank into operating engine; ball not centered in turn coordinator but centered to earth — “split the ball.”

→ P-Factor

Relative wind not aligned with prop; descending blade gets larger AoA; thrust line moves from center.
Critical engine: left engine on clockwise prop (right thrust line moves furthest from center).
Engine quit → airplane moves sideways; rudder counteracts; bank raises dead engine.
50% power loss ≈ 70% performance loss. Slower = more yaw. P-factor ↑ with AoA; rudder effectiveness ↓ with speed.
High perf small tail: rudder can snap away → flat spin risk.

→ VMCA Factors

→ Flat Spin

Relative airflow from below; no flow to elevator & rudder.
Centrifugal force: engine mass (~200 kg) + fuel at extremity → large force; small tail cannot counteract; stall at tail.
Mitigation: fwd C.G. — full fuel / shift weight fwd.
VMC training close to VMC is dangerous; VMC near stall = spin risk. High VMC = bad; Low VMC = good (may be below stall).
Altitude ↑ → VMCA ↓. Test pilot region: VMCA < stall speed.
Corrective action: NOSE DOWN — NO AILERON — NO POWER.

→ C.G. Envelope