Date: 201603
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Light: Night
Aircraft: Helicopter
Operating under: Part 91
Flight phase: Final Approach
Airspace: Class D ZZZ
ATC / advisory: Tower ZZZ
Second aircraft: Small Aircraft; Low Wing; 2 Eng; Retractable Gear
Reporter organization: Government
Reporter function: Local
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Distraction; Communication Breakdown; Confusion; Situational Awareness
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control
When detected: In-flight
Contributing factors: Procedure; Human Factors
Primary problem: Procedure

Narrative: I was working the LC2 position as OJT Instructor. Training had just been completed and I gave the position to a relieving controller. During my overlap I observed traffic on final approach Runway 3R on the LC1 controller's frequency. Aircraft X using a local call sign; was short final Runway 3R over highway XY. Two miles behind Aircraft X was a much faster aircraft overtaking Aircraft X on short final. While Aircraft X was still on final; now between highway XY and the blast pad for Runway 3R; I heard the LC1 controller issue Aircraft X instructions to 'start your go.' Aircraft Y was now less than a mile behind Aircraft X maneuvering left and right to build space between themselves and Aircraft X. Aircraft X did not initially respond to the LC1 controller's instructions; the controller issued additional instructions to Aircraft X to offset right of the runway then told Aircraft Y; about the Aircraft X going around. The phraseology used by the controller should have been 'Aircraft X go around.' There have been multiple instances similar to this I have observed at ZZZ where controllers are issuing vague instructions to aircraft to 'start your go' when they are still in the landing phase of flight before and after the runway threshold. Compression on final with various aircraft types in the pattern adds to complexity at ZZZ in the VFR traffic pattern; especially with helicopters requesting to fly their approach to the runway at less than 50 knots; being followed by aircraft 2-4x as fast. It is a well known complexity and daily occurrence ZZZ controllers have to deal with in order to maintain runway separation. Another contributing factor is that nearly every controller at ZZZ clears [these types of aircraft] for 'the option' which often leads to spending long amounts of time on the runway that the controller did not expect them to do. It is such a common clearance at ZZZ that when a controller issues a clearance for a 'touch n go' or a landing clearance the pilots will read back 'cleared for the option' or make a request for the option. There are flights schools at ZZZ that operate daily; better knowledge of ATC clearances and what they mean to pilots would benefit daily ops. Teaching them the difference between what the controller expects the helo to do when they are cleared to land; or touch n go; or option; etc. Better use of runway clearances by controllers at ZZZ to ensure runway separation will exist is also a potential way to improve these types of situations.




Synopsis: Local Controller reported that bad phraseology that is becoming too common at the facility. Controllers are not telling the aircraft to go-around; but are telling them to start your go.