Do the vibration limit gauges alert the pilot for both N1 and N2, only N1, or only N2?

• A. N1 only
• B. Both N1 and N2
• C. N2 only
• D. Neither

Answer: (B)

Vibration limit gauges are there to monitor engine vibration and warn the crew when that vibration exceeds permitted levels. Since an engine can develop excessive vibration on either the low-pressure spool (N1) or the high-pressure spool (N2), the system is designed to alert for both. This ensures the pilot hears a warning and can take appropriate action regardless of which spool is affected, protecting the engine from damage and maintaining airframe safety. So the gauge alerts for both N1 and N2.