MSP Tower Controller reported aircraft are executing go-arounds due to newly implemented Converging Runway Operations (CRO) procedures at MSP. The Tower Controller stated the new procedures introduce unnecessary collision risk and force ATC to use procedures which do not permit a controller to ensure positive separation of aircraft.

Narrative

MSP Airport has turned back on Converging Runway Operations (CRO) with NO operational need to turn on an operation that has NOT been fully vetted. It is being turned on for training. CRO is arguably the most complex operation an airport can run because of the increased risk for go-around or balked landing aircraft conflicting with runways that they intersect with. The NTSB sent out a national memo years ago. In that memo; the National Transportation Safety Board made the following recommendation to the Federal Aviation Administration. Amend Federal Aviation Administration Order 7110.65; 'Air Traffic Control;' to establish separation standards similar to the provisions of paragraph 3-9-8 between an arriving aircraft that goes around and any combination of arriving or departing aircraft operating on runways where flightpaths may intersect (A-13-024). They further clarified that when the pilot of a landing aircraft executes a go-around maneuver; as in the examples provided; air traffic controllers may be left with no viable options to ensure that safe separation exists between the go-around aircraft and aircraft operating to or from converging runways. In these events; the ATC tower controllers attempted to use Tower visual separation rules to ensure the aircraft did not collide at the point where the flightpaths intersected. The FAA's Pilot-Controller Glossary contains the following definition of visual separation. VISUAL SEPARATION - a means employed by ATC to separate aircraft in terminal areas and en route airspace in the NAS; National Airspace System. There are two ways to effect this separation: The Tower Controller sees the aircraft involved and issues instructions; as necessary; to ensure that the aircraft avoid each other; a pilot sees the other aircraft involved and upon instructions from the controller provides his/her own separation by maneuvering his/her aircraft as necessary to avoid it. This may involve following another aircraft or keeping it in sight until it is no longer a factor. Because of the nature of the geometry of the encounters and the unexpected nature of the go-arounds; it was not possible for the ATC tower controllers to issue effective control instructions to ensure that the airplanes avoided each other. Therefore; visual separation procedures could not be successfully applied or asserted as an adequate means of resolving the conflicts. The NTSB is concerned that in these events; ATC was not able to ensure the safe separation of aircraft. Instead; separation was established by resorting to impromptu evasive maneuvers by pilots during critical phases of flight. The NTSB concludes that the lack of specific separation standards; similar to those defined in paragraph 3-9-8 of FAA Order 7110.65; 'Air Traffic Control;' applicable to departing aircraft and aircraft conducting a go-around from non-intersecting runways where flightpaths intersect; facilitates hazardous conflicts and introduces unnecessary collision risk. Therefore; if a controller cannot successfully provide visual separation due to the geometry or provide adequate means of resolving the conflicts; what separation are controllers at Minneapolis Tower; MSP; using when aircraft go around on their own or are sent around due to an aircraft departing in the Arrival/Departure Window (ADW)? The answer is; Minneapolis Tower is requiring controllers to use visual separation. However; this NTSB recommendation clearly gave numerous examples and of how relying on visual separation alone for departing aircraft and aircraft conducting a go-around from non-intersecting runways where flightpaths intersect; facilitates hazardous conflicts and introduces unnecessary collision risk. Minneapolis Tower is very unique due to the fact that arrivals are also trying to land; while departures are departing the same runway that need to be airborne before the ADW. If a pilot delays takeoff roll for 10 seconds or more; a violation of the ADW can exist. Therefore; controllers are being instructed to 'try' to abort a takeoff roll. If that fails; then the arrival to Runway 35 should be sent around. This creates the exact situation the NTSB is talking about. The potential to have 4 or more aircraft in the air at one time in an area of less than 2 miles highly increases. The only form of separation that will exist would be visual separation; but we are not supposed to rely on that according to this NTSB recommendation.Having an ADW tells controllers the area that aircraft have the highest likelihood of collision. Not departing in the ADW decreases the risk of collision. MSP does have two separate ADWs. However; MSP does NOT have dedicated departure runways. What is being asked of controllers at MSP - due to the pressure of arrivals trying to land on the same runway - that a controller must depart in a small window of time to safely separate aircraft; does not have room built in for human factors or mechanical factors. If MSP had dedicated departure runways it would be possible to safely perform CRO as the NTSB is addressing in the memo.One must ask the questions the NTSB asked. Does this operation facilitate hazardous conflicts and introduces unnecessary collision risk? Answer: Yes. If an aircraft goes around or is sent around due to non-compliance of the ADW they are going around at the exact point where the greatest risk of collision exists. When an aircraft goes around or is sent around due to non-compliance of the ADW what separation exists? Answer: The only separation that exists is visual separation. However; according to the NTSB; 'Because of the nature of the geometry of the encounters and the unexpected nature of the go-arounds; it was not possible for the ATC tower controllers to issue effective control instructions to ensure that the airplanes avoided each other. Therefore; visual separation procedures could not be successfully applied or asserted as an adequate means of resolving the conflicts'. Therefore; controllers at MSP are left with no alternative form of separation when an aircraft goes around or is sent around in an ADW.Over the past two days that CRO has been turned on I personally know of two aircraft that were either sent around or went around their own. This operation is adding unnecessary risk to a fragile safety system when there is no demand to perform CRO. Important safety recommendation have flat out been cherry-picked on which items the FAA will follow.