Commercial Fixed Wing
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Aircraft; Human Factors
After boarding; the gate agent (who had already been inside the aircraft several times before boarding yet had said nothing) stated that the outboard left main gear tire might look low. I asked the First Officer how it looked during the preflight; and he said fine. We decided to check it out again anyway. The aircraft was sitting in some slush and it looked like that tire was fine but appeared flat on the bottom due to the slush/snow around the tire.We decided to go ahead; but also keep a close eye on the tire for the remainder of the legs. We flew four uneventful legs and although we did carefully check the tires on the left side each time; they appeared equivalent to each other and not unduly flat on the bottom. Neither did they appear to bulge on the side or crack or show any damage associated with repeated legs on an underinflated tire. However; we don't have a 'calibrated eyeball;' so perhaps one or both were a little low. It is impossible to say at this point.Each leg went without incident and even the landings made by both pilots were what I would consider above average (the conditions were not challenging; other than contaminated runways). There were frozen ice chunks and snow (which could have been sharp) at each destination and some sliding on packed snow off on to pavement (which could cause scuffing) but nothing out of the ordinary for this time of year. The left tires--as well as the rest of the aircraft--were of course carefully checked before and after each flight.Upon landing in Denver; we took the first high speed taxiway off the runway. While approaching the next high speed exit from the runway; we were asked to keep our speed up to make way for a flight exiting the second high speed. Upon rounding the next (less than 90 degree turn) corner; I was a little off centerline in order to minimize the side loading yet still comply with the request to keep our speed up (apex turn). There may have been FOD on the edge of the taxiway but of course that is just speculation.The flight attendant later confirmed that it did not feel to her as if we were rounding the corner at an untoward speed. At this point we heard a high pitched noise and a slight settling of the aircraft. This was after the after landing checklist was completed; and the number one engine had been shut down; so it was a while after landing. The flight attendant also later stated that she was finished with her announcement; thus confirming that it was not immediately after landing.The aircraft was still taxiing straight and was not exhibiting vibrations or control difficulties. We elected to continue the taxi rather than strand all our passenger way out away from the terminal while awaiting rescue. We advised ground control we would taxi slowly; at which point the flight behind volunteered that it looked like our inboard tire was flat; but we should be OK to continue. Feeling that we were making the right decision; we pressed on.After reaching the ramp; a few miles away; the aircraft did start to shake a little and it was taking quite a bit of power to taxi. At this point I was very concerned that we were doing further damage to the landing gear other than the tire; but we were so close to the gate and I suppose I had 'get there itis.' When we told ramp control that we would taxi slowly; a passing flight volunteered that both tires were flat but the treads were still on the rim and in their words 'nothing looked dangerous.' So once again; we elected to press on; since it was only a few hundred meters to the gate at this point.When we finally did park; as the passengers expressed their gratitude for making it to the gate rather than stopping for hours on the taxiways; all I could think about was if I had further damaged the aircraft by taxiing on what at this point were two flat tires. Luckily this was not the case but it certainly could have been. After exiting the aircraft the situation was indeed far worse than I had expected and I still question that decision to continue even though damage other than to the tires did not occur--so far as I know.What was learned? First; if we take a delay every time a gate agent; ramper; or really any non-mechanic or non-flight crew member says something 'looks funny;' we would take a lot of unnecessary delays. However; this may have been the first opportunity to break a link in this chain of events. Everyone out there is responsible for safety; together; and in hindsight maybe we should have taken a delay and had the left tire or tires checked even though they appeared fine. It is also frankly unknown if this was the root cause but I can't help but think what if?The second thing that bears discussion is whether or not continuing the taxi was a good idea. One very senior member of management I spoke to says he would have done the same thing; but what if extensive damage had been caused? I wonder if there needs to be a clear policy in place.In the final analysis; letting other people influence decision making--concerns of the passengers; listening to the opinions of other airline's pilots on what they see from their lofty perch; and allowing company culture and 'get-there-itis' to put pressure on oneself--is all too easy. When the decisions come hard and fast; will the crew do the right thing or stay in the 'get the job done [almost] no matter what' mindset? What mode do you revert to when the pressure is on?
Air carrier Captain reported operating with what may have been an under-inflated tire; and by the time they parked the aircraft they had two flat main landing gear tires.