Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Flight Crew Last 90 Days 110; Flight Crew Total 8500; Flight Crew Type 1635
Troubleshooting
Aircraft Equipment Problem Less Severe
Flight Crew Landed in Emergency Condition
Aircraft
Captain noticed heavy aileron control descending into Denver upon disconnecting the autopilot descending through approximately 20;000 feet. [The Captain] transferred controls to me briefly to verify. Our speed was still around 280 knots and we were set up for an RNAV Z approach to XYR. Initially the only concern was maintaining the RNP (Required Navigation Performance) arc so we informed ATC that we would need a visual approach. As the airplane slowed controllability primarily along the roll axis worsened. The controls were briefly transferred to me several times - I would describe it as driving an old car without power steering. Perhaps not nearly as hard as full manual reversion as duplicated by a simulator; but definitely abnormal. Hydraulics indicated normal. At this time we [advised ATC] and ultimately made an uneventful landing on XYR and upon determining operable brakes and steering taxied to the gate. On base leg we got a quick call to the flight attendants advising them that we had an abnormal situation and as a precaution fire trucks would likely follow us to the gate. On final a rear Flight Attendant called the flight deck as she hadn't heard the initial conversation. Repeated it to her. [ATC was advised] roughly abeam the airport on the downwind leg; perhaps 5 minutes before landing. A large weather reroute had left us landing with about 5000 lbs of fuel. The weather was great in ZZZ; although LLWS (Low Level Wind Shear) advisories existed. No wind shear was encountered.
B737 Captain reported stiff feel to the roll mode after disengaging the autopilot.