B737-800
Workload; Distraction; Human-Machine Interface
Aircraft Equipment Problem Less Severe; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
General None Reported / Taken
Aircraft; Weather
Normal approach on a clear day.  Crossed SILER at 210 KTS and 11;000 FT as per BOWIE STAR landing north.  After passing SILER I selected 202 KTS. (+/- 10 KTS is the max airspeed deviation allowed by ATC). A mile or two after SILER we were given a descent to 6;000 FT then 4;000 FT.  I selected level change; asked for and got Flaps 10.  The aircraft was stable and descending normally at 202 KTS.  Passing 9;000 FT in descent we began to encounter light to moderate chop.  I made a nice landing; however; at 6;300 FT the airspeed indicator read 215 KTS for 3 seconds. Due to the turbulence and my dependence on the autopilot to maintain airspeed I did not notice the airspeed infraction; but was told about it later. The airspeed indicator on our 737's is like no other airspeed indicator I have ever seen.  In 30+ years of flying jet aircraft no other airplane has such a sensitive airspeed indicator.  It appears to be very sensitive to fluctuations in temperature.  At cruise; I've seen the IAS jump 20+ KTS in less than a second without the throttles moving; a pitch change; and in smooth air.  The autopilot is unwilling; in level change; to make the same aggressive pitch changes necessary to maintain airspeed as the airspeed indicator is willing to fluctuate.  Until the fluctuations in temperature sensitivity are dampened this sort of over speed will continue.
A B737-800 pilot was notified of a flap overspeed and commented that this aircraft type is sensitive to environmental changes and additionally the autopilot does not aggressively respond to airspeed fluctuations.