Date: 201603
Local time of day: 1201-1800
Location: BJC.Tower, CO
Flight conditions: Marginal
Weather elements / visibility: Snow
Light: Daylight
Aircraft: Light Transport; Low Wing; 2 Turboprop Eng
Operator: Air Taxi
Operating under: Part 135
Flight plan: IFR
Mission: Cargo / Freight / Delivery
Flight phase: Final Approach
Airspace: Class D BJC
ATC / advisory: Tower BJC
Reporter organization: Government
Reporter function: Supervisor / CIC
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Situational Awareness; Training / Qualification
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Detector: Automation Air Traffic Control; Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert
Contributing factors: Airspace Structure; Human Factors; ATC Equipment / Nav Facility / Buildings; Procedure
Primary problem: Procedure

Narrative: I was working as the Controller In Charge (CIC) and had reminded Local Control to adjust the lighting due to rapidly deteriorating visibility due to snow. I turned my attention to completing the new METAR observation and ATIS and was aware that Aircraft X was inbound near the FAF. Shortly after checking on; the LA alert began sounding. I turned toward Local Control to see what was happening and started to remind Local Control to issue the low altitude alert to the pilot; while TRACON simultaneously called on the shout line. After an initial pause; the controller coordinated first; and then issued the alert to Aircraft X (the phraseology for the alert did not include 'check your altitude immediately' phraseology).I was glad that I was working CIC de-combined because it allowed me to be in a position to provide maximum assistance to Local Control if needed. In hindsight; I am concerned because I believe the highest priority needed to be issuing the safety alert to Aircraft X first; with complete phraseology; prior to responding to coordination from the radar controller. I feel this event reveals some important concerns about the issuance of safety alerts that need to be urgently addressed at our facility; and perhaps other towers like ours as well. This is not the first time I have observed a tower controller seem unsure or hesitant to remember the actions and phraseology needed when the LA alert sounded during low visibility conditions. I worry that complacency may set in because these alerts are not regularly issued to pilots during VMC conditions; as we are looking out the window and can visibly determine that the aircraft is in a position that in our judgment; is not in unsafe proximity to the ground or obstacles. Further; I am concerned that there is a lack of understanding among some controllers about why the MSAW/LA alarm sounds (predicted flight path or descent rate I believe?) and why it is essential that we distinguish between how to handle a nuisance alarm during VMC and an alert that goes off during IMC when there is no way we can possibly observe what the aircraft is doing!I feel there needs to be prompt action to address the issue again. My suggestion is a face to face briefing and discussion with all facility personnel to review procedures for handling safety alerts; including a review of complete and proper phraseology. I think there should also be tabletop exercises of real-life scenarios that could be encountered at our facility that include having the controller simulate the actions they need to take and the phraseology they need to issue during the LA alert. The phraseology should be ingrained and said without hesitation during a critical situation. In the event of a pilot error or equipment malfunction; the action we take as controllers when a LA alert is received may be the last line of defense to warn a pilot of a dangerous situation and prevent a potential accident.




Synopsis: BJC Controller in Charge had to prompt the Local Controller to take appropriate action when a low altitude alert sounded in the Tower. The CIC reported the Controller did not issue the advisory to the aircraft in a timely or appropriate manner.