What is a V-n diagram and what does it illustrate for flight safety?

• A. A V-n diagram shows velocity profiles during takeoff and landing.
• B. A V-n diagram shows limit load factors versus airspeed, including stall and structural limits, outlining the safe flight envelope.
• C. A V-n diagram shows engine thrust versus altitude.
• D. A V-n diagram shows fuel consumption versus airspeed.

Answer: (B)

A V-n diagram maps how much load the airframe can carry (load factor, n) across the range of airspeeds (V). The vertical axis is load factor, showing positive and negative g limits, while the horizontal axis is airspeed. The diagram contains curves for the positive and negative structural limits, which define the maximum stresses the airplane can safely withstand at each speed. It also includes a stall boundary at the low-speed end, showing that as you slow down you reach stall before you can reach higher load factors. The safe flight envelope is the region inside these boundaries, so staying within it keeps you away from structural overstress and stall even in gusts or during maneuvering. This is what makes the V-n diagram a key safety tool: it translates limits on speed and load into a single map of permissible flight conditions. The other options refer to aspects not shown on a V-n diagram—engine thrust versus altitude, fuel consumption versus airspeed, or velocity profiles during takeoff and landing.