Date: 201901
Local time of day: 1801-2400
Location: SDL.Airport, AZ
Light: Night
Aircraft: Super King Air 300
Operating under: Part 91
Flight plan: IFR
Flight phase: Initial Approach
Airspace: Class D SDL
ATC / advisory: TRACON P50
Second aircraft: BAe 125 Series 800
Reporter organization: Government
Reporter function: Local
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Communication Breakdown; Situational Awareness
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Executed Go Around / Missed Approach; Flight Crew Took Evasive Action
Contributing factors: Human Factors; Procedure
Primary problem: Human Factors

Narrative: P50 flashed 2 IFR inbound aircraft to me at SDL. Aircraft Y was inbound from the NW and Aircraft X was inbound from the North on a straight in. When Aircraft Y called me; he was on a 5 mile right base to Runway 21. Aircraft X was about an 8 mile final; but wasn't on my frequency. I told Aircraft Y to enter a right base and proceed direct to the airport. I call P50 to find out what their intentions were with Aircraft X but no-one answered the landline. I gave traffic to Aircraft Y and told him to continue turning toward the runway. Aircraft Y said he had Aircraft X insight. Aircraft X was still not on frequency and when P50 finally called us back; they said Aircraft X wasn't on their frequency either. I continued to reach out to Aircraft X; but he still wasn't on frequency and was descending on final. We also got out the light gun and flashed the red light to Aircraft X in case they were NORDO. Aircraft Y was Number 1 and the runway was clear but pilot sent self around because he was concerned about Aircraft X in trail. At the same time; P50 figured out that Aircraft X was on their frequency and also sent the Aircraft X around too. Aircraft Y was about 1/2 mile final and Aircraft X was about 2 mile final. P50 gave me a heading and altitude for Aircraft Y and I issued it and shipped him back to Approach to vector back to the approach.Communication between the 2 facilities is at an all-time low. It's typical for P50 on not answer the shout line when we call to try and coordinate something. This needs to be address [at] this the facility.Also; this whole situation could have been solved if the controller at P50 checked their frequency for the missing Aircraft X rather than just assuming Aircraft X switched. P50 is required to provide a sequence for all IFR traffic and this was clearly not done in this situation. If both aircraft had actually checked in; I still didn't have any sequence. Both aircraft were a tie and I had to turn aircraft towards the runway and issue traffic. P50 needs to ship aircraft in a timely manner. The LOA (Letter of Agreement) states that they need to be [switched] prior to enter the Delta and that clearly didn't happen.I should have sent Aircraft Y around when P50 said Aircraft X wasn't on their frequency. That way we could have gotten him out of the way of a possible NORDO aircraft.




Synopsis: SDL Tower Controller reported an unsafe situation between two arrivals where both aircraft executed a different sequence.