What happens to boost pressure as an aircraft climbs in altitude?

As an aircraft climbs in altitude, the atmospheric pressure decreases, which directly affects the boost pressure generated by the engine's supercharger. Without any corrective measures, boost pressure will decrease because the supercharger relies on ambient air pressure to compress the intake charge.

The A.B.C. (Automatic Boost Control) system is designed to maintain optimal boost pressure as altitude increases. If the A.B.C. is functioning properly, it can compensate for the loss of ambient pressure, thus preventing a drop in boost pressure that would negatively impact engine performance. Therefore, the accurate statement is that boost pressure decreases with altitude unless corrected by the A.B.C., which actively adjusts the supercharger's output to maintain performance levels.