B737 flight crew reported discrepancy with airspeed indicators and associated avionics. Flight crew diverted back to departure airport.
Synopsis
B737 flight crew reported discrepancy with airspeed indicators and associated avionics. Flight crew diverted back to departure airport.
Narrative
Immediately after departure; as the pilot monitoring (PM) I noticed my SPD LIM amber flag on the Primary Flight Display (PFD) speed tape. I mentioned it to my First Officer (FO); saw no speed irregularities; and saw her side was normal and stated to continue flying normal ops". I noticed that the stall bands on the bottom of the speed tape were gone at this point as well. No caution lights were illuminated at any point during the flight (aside from OFF SCHD DES).We continued climbing and ran the after takeoff checklist. Around 10;000 my pitch guidance on my Flight Director (FD) became intermittent. At this point I got into the FM and saw the SPD LIM flag was an indication of Airspeed Unreliable. I took a look at both PFDs and the standby and all 3 were showing identical airspeeds. Still; we performed the immediate action items for the condition and then ran the QRH. Shortly after and around 18;000 we started getting an intermittent stick shaker. I made the decision at this point to stop the climb and request hold from ATC. At this point the Autopilot was engaged again and I initiated a call with Dispatch and Maintenance Control.During the call and after having verbalized our situation; the Maintenance Control rep stated "we'll take a look at it in ZZZ1." I was taken aback and said "did you just say you want us to fly this thing to ZZZ1 with an intermittent stick shaker?". They then stated to "do what you deem the best course of action; but if you do divert we would appreciate a Maintenance base" and even mentioned ZZZ2. I then stated we wouldn't be flying anywhere other than back to ZZZ. Dispatch agreed and the decision was made with my FO to return to ZZZ.Priority handling was requested. We reconfigured the aircraft for a ZZZ diversion; and proceeded back to the airport. Neither the FO or I recall getting the stick shaker once below 18;000; but the rest of the anomalies remained until touchdown; at which point the SPD LIM flag was no longer present.At no point during any phase of flight were the airspeeds on the speed tape or standby indicator different.We taxied to the gate without further issues."
Second reporter narrative
On departure off of Runway XX in ZZZ I was pilot flying. The Captain stated that he had a speed limit indicator flag on his speed tape. He crosscheck our instruments and his speed; my speed; and the standby indicator all indicated the same air speed. The Captain stated that he lost vertical guidance on his flight director he ran the QRH for the speed limit indicator; and we also ran immediate action items for airspeed unreliable. We continued to climb and after 18;000 we got a stick shaker at which point we leveled off at FL200 and requested a present position hold. I flew and talked on the radios. The Captain contacted Dispatch and Maintenance Control. We had another stick shaker while in the hold. We requested priority handling and made the decision to return to ZZZ and told the flight attendant passengers what was happening. We set ourselves up for diversion back in ZZZ and had the stick shaker indication one more time before18;000. We also got the off schedule decent light and ran the checklist for that. We landed back into ZZZ roughly 2000 pounds overweight on Runway XXL. The Captain stated that when we landed his speed limit indicator flag had disappeared. We taxied to the gate as normal.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.