Date: 202002
Local time of day: 1201-1800
Location: DFW.Airport, TX
Flight conditions: VMC
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Final Approach
Airspace: Class B DFW
ATC / advisory: Tower DFW
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Not Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Second reporter function: Pilot Flying; Captain
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Returned To Clearance
Contributing factors: Environment - Non Weather Related; Human Factors; Procedure
Primary problem: Human Factors

Narrative: I checked in with the first DFW Regional Controller while on the VKTRY STAR. We were assigned RWY 18R. Shortly thereafter the same controller changed our runway assignment to Runway 18L and proceed direct UDALL. We were switched to the final DFW Regional Controller. That controller was asking other aircraft if they could switch back to Runway 18R. We were not asked to switch by the final DFW Regional Controller. As we neared UDALL we were assigned heading 150 and asked if we had DFW in sight. We complied with the heading clearance; called the field; and we were cleared for the Visual Approach 18L. This last instruction had us joining the extended centerline closer to FAF HASTY. HASTY is charted as 5 miles from the threshold. We were told to contact Tower. Upon checking in with Tower; we were told to switch runway assignment back to Runway 18R. With the Captain's consent I replied 'unable.' We were asked why we couldn't switch. I replied 'operational restriction. We can't switch runway assignments this low to the ground (1;500 [feet AGL] by my recollection) without the risk of the aircraft notifying the company of some deviation.' While not explicitly saying so in my statement; I was referencing our SMS (Safety Management) and FOQA (Quality Assurance) parameters. I am aware FOQA sets the standard at 1;000 [feet AGL]; but neither the Captain or I want to risk a deviation while reloading the FMS. The Tower told us to continue. We continued our configuration of the aircraft and we were eventually given clearance to land 18L. We were told to clear the runway and join Taxiway F southbound and to remain with Tower. At the southern end of Taxiway F we were told to copy a phone number and call the Tower upon reaching the gate.The Captain made the phone call at the gate and while I was only aware of his half of the conversation; it seems that the Tower's position is that in VFR conditions:1. Side steps are to be complied with immediately; even if inside the FAF.2. Statements of 'Unable' are not allowed.3. We can do these maneuvers without fear of safety violation.We have the AIM and Title 14 of the CFR. On top of that we have Manufacturer's POH. On top of that we have our manuals. We fly the top of that stack and we certainly don't fly generic passages in FAA JO 7110 without questioning how they might conflict with SMS. It is the position of both myself and the Captain; that my 'unable' should only have had two outcomes.1. Clearance to land and taxi to the gate without further harassment.2. Instructions to go-around and expect Runway 18R after the go-around procedure.Factors which may lead to unstable approaches include: Late clearances or runway changes. Right now I have no idea if there's a Controller in DFW Tower kicking this event up the chain to the FSDO so I receive certificate action.


Second narrative: We checked in with the first DFW Regional Controller while on the VKTRY STAR. We were assigned RWY 18R.  Shortly there after the same controller changed our runway assignment to Runway 18L and proceed direct UDALL. We were switched to the Final DFW Regional Controller. That Controller was asking other aircraft if they could switch back to Runway 18R. We were not asked to switch by the final DFW Regional Controller. As we neared UDALL we were assigned heading 150 and asked if we had DFW in sight. We complied with the heading clearance; called the field; and we were cleared for the Visual Approach 18L. This last instruction had us joining the localizer closer to FAF HASTY. HASTY is charted as 5 miles from the thresh hold.  We were told to contact Tower.Upon checking in with Tower; we were told to switch runway assignment back to Runway 18R. Since we were approaching the FAF to 18L I told the FO (First Officer) to tell the controller we are 'Unable.'  As a company and crew we have emphasized the importance of a stable approach and the leading causes of unstable approaches; the Controller's action would have led us toward a potentially unstable approach. We were asked why we couldn't switch.  The FO replied 'Operational restriction. We can't switch runway assignments this low to the ground (1;500 [feet AGL] by my recollection) without the risk of the aircraft notifying the company of some deviation.' I have been 'asked' on extended final if I could accept a transition to the parallel runway; but never just cleared to transition as we check in approaching the FAF. The Tower told us to continue. We continued our configuration of the aircraft and we were eventually given clearance to land 18L.  We were told to clear the runway and join Taxiway F southbound and to remain with Tower. At the southern end of Taxiway F we were told to copy a phone number and call the Tower upon reaching the gate.The Captain made the phone call at the gate and while I was only aware of his half of the conversation; it seems that the Tower's position is that in VFR conditions; side steps are to be complied with immediately; even if inside the FAF. Statements of 'Unable' are not allowed. We can do these maneuvers without fear of safety violation. After we secured the aircraft at the gate I called the Tower phone number; as directed; and spoke to an individual that stated he was observing our approach. I do not know if he was a Supervisor or a controller. He asked why we would not accept the transition and I stated we were approaching the FAF after being changed from 18R to 18L and now at the last minute the controller just clears us to transition back to 18R. To configure and change or remove the localizer frequency and update FMS sets us up for an unstable approach. The individual on the phone then stated we are the first aircraft that would not accept the clearance and that they do it all the time. He stated that it was approach that flipped us from 18R to 18L due to a runway inspection and now we are delaying his departures by not accepting the Controller's last minute change. He stated we are VFR and should not have any reason why we could not accept their clearance to transition to 18R as we check in with Tower approaching the FAF to 18L. The safety of the aircraft; passengers and crew are my responsibility; if we state 'unable' the controller could do the following: Ask our intentions; clear us to land or have us go around and set up for 18R.


Synopsis: Flight crew reported that they were unable to change runways on short final to DFW; and the Tower Controller had issues with them not changing.