Date: 201503
Local time of day: 0601-1200
Location: DEN.Airport, CO
Flight conditions: IMC
Weather elements / visibility: Icing; 4
Light: Daylight
Aircraft: B737-700
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class B DEN
ATC / advisory: TRACON D01
Reporter organization: Air Carrier
Reporter function: Captain
Human factors: Situational Awareness
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: General None Reported / Taken
Contributing factors: Weather; Human Factors
Primary problem: Weather

Narrative: [Inbound to DEN] we checked ATIS to see if the forecast snow had started and it said SVR Rime in DEN area; report from 737. We sent an ACARS message to Dispatch asking if aircraft were landing.  I wrote down his response: 'That PIREP is almost an hour old; last report I heard was MOD Rime.' But at that time it was still on the current ATIS.  In the next ATIS any mention of SVR Rime was gone. [Later a] special ATIS said SVR Rime 7000 feet to 9000 feet; 10 miles south of DEN (we landed 35R; obviously approaching from south).  In the [current] ATIS SVR Rime was gone. [During arrival] the DEN Center Controller mentioned SVR Rime in DEN to all on the frequency. We missed the details so we asked her to repeat it. In a hurry she said '30 miles around DEN airport SVR Rime at 12;000'reported by an Airbus' (the altitude was probably wrong because the cloud layer was not that high).  A few minutes later we checked in with DEN Approach; asked him about the report Center gave us and he said he had not heard of it.  He asked two aircraft ahead of us and they said they were getting 'MOD Rime'.  We decided based on that report to continue on to land.  We started getting heavy icing but could not see the wings because of buildup on the side windows. So in our case; we could not tell if was severe. We had reviewed that severe icing is ice that the aircraft's systems can't keep up with and shed. On my commute home a gut feeling got worse; so I reread [the regulations] which we had reviewed after the first ATIS report. Paraphrasing--'Do not continue toward any airport...Landing is not authorized... '(Looking at a combination of PIREPs; we had three of them; aircraft type 737 and Airbus; times and locations; and altitudes; considered (1630 feet above ground and in our case at the FAF for 35R)...  'no aircraft will be Dispatched; enroute Ops continued or landing attempted which might affect safety if conditions exist or are anticipated...'  We had on and off again SVR Rime for several hours prior. The wind was howling and pushing the system through and conditions were changing by the minute. When we decided to continue to land we were relying on two aircraft ahead of us that did not see severe rime. We seem to have had an obvious trend or pattern for several hours of occasional severe rime conditions. It seems that severe rime could be 'anticipated'. We received nothing from Dispatch on the icing other than the one response after our query.In hindsight; I am sure the Crews that said 'severe' weighed their assessment carefully (like the Crew that says 'nil braking') knowing that it will shut down the operation. Should we have continued? I am still not sure. Should the operation have been shut down? When is it OK to continue after severe rime has been reported? Is it OK if the reporting aircraft was three ahead of you; 15 minutes ago?




Synopsis: A B737-700 Captain reported he was not sure he was legal to continue on his approach to DEN when severe rime ice might have been in the area.