One number too big: how 32,767 destroyed Ariane 5

On 4 June 1996, Flight 501 tried to squeeze a 64-bit horizontal bias value (BH) into a 16-bit signed integer. Try it yourself.

BH conversion simulator

The 16-bit signed range is -32,768 to 32,767. Press convert.

float64 (sign, exponent, mantissa):

int16:

SRI 2: nominal SRI 1: nominal

Ariane 4 vs Ariane 5 horizontal bias

Illustrative curves. Dashed red line: int16 ceiling 32,767.

Verified facts

    Get the full post-mortem PDF