APR N2 limit value is?

APR N2 limit value is?

• A. 99.4%
• B. 99.5%
• C. 98.0%
• D. 100.0%

Answer: (A)

The main idea here is the protective limit for the N2 (high‑pressure compressor) speed when APR mode is active. N2 is the speed of the engine’s core spool, shown as a percentage of its maximum speed. The APR limit is the highest N2 value the system allows before it trims back power or intervenes to protect the engine. Why 99.4% is the best answer: the engine’s protection margin is set just below 100% to account for instrument tolerance, transients, and potential measurement errors. Setting the APR limit at 99.4% provides a safe buffer so the FADEC can respond before N2 actually reaches the true maximum. While 100.0% is the theoretical limit, using it as the APR limit would leave no margin for safe operation. The other values (much lower or essentially 100%) don’t align with the built‑in protection margin that keeps the engine safe from overspeed or surge.

The main idea here is the protective limit for the N2 (high‑pressure compressor) speed when APR mode is active. N2 is the speed of the engine’s core spool, shown as a percentage of its maximum speed. The APR limit is the highest N2 value the system allows before it trims back power or intervenes to protect the engine.

Why 99.4% is the best answer: the engine’s protection margin is set just below 100% to account for instrument tolerance, transients, and potential measurement errors. Setting the APR limit at 99.4% provides a safe buffer so the FADEC can respond before N2 actually reaches the true maximum. While 100.0% is the theoretical limit, using it as the APR limit would leave no margin for safe operation. The other values (much lower or essentially 100%) don’t align with the built‑in protection margin that keeps the engine safe from overspeed or surge.