PUB Tower Controller reported issuing a low altitude alert to a night VFR arrival that entered the pattern below minimum safe altitude, resulted in a CFTT event.

ACN 2085583 2024-02 Small Aircraft, High Wing, 1 Eng, Fixed Gear Air Traffic Controller Reports

Initial Approach

What is ASRS?

The Aviation Safety Reporting System is NASA's voluntary, confidential, non- punitive incident-reporting system, established 1976. Pilots, controllers, dispatchers, and maintenance technicians file reports describing safety- relevant events. NASA de-identifies every report before adding it to the public database. Reports are not investigated by NASA, the FAA, or the NTSB — they represent the reporter's perspective.

Pilot narrative

Verbatim from the de-identified NASA record. First-person account by the reporter. NASA strips identifying details (names, company, specific time); anonymization placeholders are ZZZ, X, Y.

Aircraft X called up VFR from the north and requested a full stop taxi back. I instructed Aircraft X to enter a left downwind for Runway 8R. Aircraft X continued inbound. As Aircraft X was approaching the PUB radar and turning to join the downwind I noticed that the aircraft appeared very low. I checked the tower radar display and observed the aircraft at 4,900 ft. I issued a low altitude alert to Aircraft X and issued the PUB Altimeter and traffic pattern altitude. Aircraft X climbed back to a safe altitude and landed safely. The ATIS was out of service when this happened but I don't believe it played into this incident. MSAW did not activate because the aircraft was VFR. Suggestion: Pilots should be aware of their altitude and the different hazards associated with night flight.

NASA classification — Anomalies

Deviation / Discrepancy - Procedural
Inflight Event / Encounter

NASA classification — Assessments

Contributing Factors / Situations: Human Factors
Primary Problem: Human Factors

ASRS reports are voluntarily submitted, de-identified by NASA, and represent the reporter's perspective. The presence of reports on a topic cannot be used to infer prevalence in the National Airspace System. The authoritative source is the NASA ASRS Database Online at asrs.arc.nasa.gov ↗.