Commercial Fixed Wing
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 121; Flight Crew Total 3907; Flight Crew Type 1889
Time Pressure; Workload; Situational Awareness; Confusion; Communication Breakdown
ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
General None Reported / Taken
Chart Or Publication; Environment - Non Weather Related; Procedure
New Captain was PM; LCA (Line Check Airman) was flying from right seat on arrival into IAH. Approach kept us so high the entire time we had to get approval to miss the altitudes. Aircraft on other arrivals were holding and we were expecting the same. We were cleared to descend via the GUSHR arrival; and had to use full speed brakes the whole time but we made 10;000 at 250kts; and were able to make the bottom altitude at GUSHR at 6000 and 210 kts. Big rain shower at 15 miles out on the final of 8L. By the time we went by the rain shower it was mostly north of our course but there was rain and lightning coming out of the shower. TCAS showed traffic on 8R behind and above us. We could see him out of our window.  We were told to hold 200 knots till about 10 mile final. At this time; traffic somewhere; behind us we think; said they needed to go around because of rain and lightning. Approach gave us a frequency and switched us to tower and told us to tell them our speed.  We switched to the Tower frequency but must have put it in wrong; and when we tried to check on to what we thought was tower; another approach told us it was the wrong frequency. To go to the Tower; we looked up on the Jepp chart and the Tower frequency for 8L was 120.725. We called Tower on 120.725 and they cleared us to land. On final after that; a monitor came on and told us to change to 119.82. We switched to 119.82 and it was the same Tower Controller as 120.725 and she cleared us to land a second time. After landing we were told to contact ATC for possible pilot deviation. We had no idea why. We contacted the ATC Ops Manager who said there was a possible conflict with the traffic on 8R as that traffic was so close that had he not seen the airport and been given a visual we would have been too close and had a separation issue.1. We were cleared for an ILS. There was no PRM operations being used or advertised.2. The tower frequency they were using; 119.82 is nowhere on the IAH 70-9 page; dated 16APR21; effective 22APR21. ATC Ops Manager said Houston has been using frequency 119.82 as Tower for a few weeks because coverage was poor on the other frequency in some areas; but that frequency (119.82) is not published anywhere. 3. After talking with ATC Ops Manager; we verified in the NOTAMs there was nothing about 119.82 being used anywhere.4. Why is approach cramming the planes on approach so close that a momentary loss of communication results in loss of separation?
Air Carrier Captain reported IAH is using an unpublished Tower frequency.