How does the EEC prevent rotor overspeed and what are the maximum N1 and N2 values?

How does the EEC prevent rotor overspeed and what are the maximum N1 and N2 values?

• A. The EEC ignores rotor speed and applies no limits.
• B. The EEC reduces fuel flow only after N1 exceeds 110%; N1 max 110.0, N2 max 120.0.
• C. The EEC uses a mechanical limiter with no explicit numbers.
• D. The EEC monitors N1 and N2 and reduces fuel flow to keep rotor speed within limits; maximum N1 106.7 and N2 117.5.

Answer: (D)

Rotor overspeed protection comes from the engine electronic control by continuously watching both rotor speeds, N1 and N2. When either spool approaches its allowable limit, the EEC actively trims fuel flow to reduce or hold speed, keeping the rotors within the safe operating envelope. This approach protects rotating components from excessive stress and potential failure, and it uses both N1 (the low‑pressure/air‑frame spool) and N2 (the high‑pressure spool) because each spool has its own critical limit that must be respected. The explicit limits used here are N1 limited to 106.7% and N2 limited to 117.5%. These values define the maximum speeds the system aims to stay under, with the EEC intervening to prevent reaching them. The other options are inaccurate because they describe no-fuel-control situations, delayed or partial limiting, or a purely mechanical limiter with no specified values, whereas the actual setup relies on monitored feedback from both spools and proactive fuel reduction to maintain rotor speeds within the safe range.

Rotor overspeed protection comes from the engine electronic control by continuously watching both rotor speeds, N1 and N2. When either spool approaches its allowable limit, the EEC actively trims fuel flow to reduce or hold speed, keeping the rotors within the safe operating envelope. This approach protects rotating components from excessive stress and potential failure, and it uses both N1 (the low‑pressure/air‑frame spool) and N2 (the high‑pressure spool) because each spool has its own critical limit that must be respected.

The explicit limits used here are N1 limited to 106.7% and N2 limited to 117.5%. These values define the maximum speeds the system aims to stay under, with the EEC intervening to prevent reaching them. The other options are inaccurate because they describe no-fuel-control situations, delayed or partial limiting, or a purely mechanical limiter with no specified values, whereas the actual setup relies on monitored feedback from both spools and proactive fuel reduction to maintain rotor speeds within the safe range.