Date: 201312
Local time of day: 1201-1800
Location: ZZZ.ARTCC, US
Flight conditions: Mixed
Light: Daylight
Aircraft: B737-700
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Air Data Computer
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; First Officer
Human factors: Training / Qualification; Workload; Human-Machine Interface; Distraction; Confusion
Anomaly: Aircraft Equipment Problem Critical; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Detector: Automation Aircraft Other Automation; Person Flight Crew
When detected: In-flight
Result: Flight Crew Took Evasive Action; Flight Crew Overcame Equipment Problem; Flight Crew Regained Aircraft Control; Flight Crew FLC complied w / Automation / Advisory; General Maintenance Action
Contributing factors: Procedure; Weather; Aircraft
Primary problem: Ambiguous

Narrative: On climbout through approximately FL200; we experienced both EECs switching to 'soft alternate mode.' As I (pilot not flying) was reading and completing the QRH checklist items as the pilot flying continued to fly; I noticed that we were rapidly approaching Vmo and no longer in much of a climb. I informed the pilot flying of this information and the pilot flying said we were about to stall and proceeded to increase power. The Overspeed Warning is going off at this point. I crosschecked with standby ASI and ALT and told pilot flying that the standby and the pilot not flying instruments agreed. I told pilot flying to reduce power. The pilot flying then consulted the HUD and said the HUD showed impending stall as well. I told pilot flying to reduce power again and repeated that pilot not flying instruments and STBY were in agreement. Around FL250; the pilot flying agreed that the pilot flying's instruments were incorrect and the unreliable airspeed appropriate actions taken. We transferred control of the aircraft since I had the instruments we deemed to be correct. We asked ATC if we could level at FL280 due to equipment issues/RVSM restrictions and they agreed and even gave us a block from FL280-283. We leveled at FL280. The following Controller upon check-in queried our altitude at which point we realized that we had not switched our transponder to report altitude from #2. We told ATC; made appropriate switch; and ATC confirmed that we were at FL280. We completed/complied with all appropriate checklists and confirmed all circuit breakers were in. The pilot not flying then contacted Dispatch and Maintenance Control. It seemed that the issue trying to be resolved was that the #1 EEC could not be selected to the 'hard alternate mode;' not the fact that we had lost data inputs; possible computers; instruments and/or their capability. As the pilot not flying tried to resolve this with Dispatch/Maintenance; I (pilot flying now); began to check weather for diversion options. We still had the FMCs' navigation functioning; however; the data portion was obviously not working. Fortunately; we and Dispatch determined that we had enough fuel to continue to our filed destination at FL280. On descent through FL180; all systems began to function normally. We completed the flight uneventfully. We spoke with Maintenance and after 20 minutes or so they were diligently working on finding the problem. I couldn't stay any longer because I had to swap aircraft to fly two more legs. In respect to actions taken to prevent/handle situation; it would be beneficial if we as pilots could find out what actually malfunctioned in a far from normal 'non-normal' situation like this one.




Synopsis: During climb through FL200 both B737-700 engine EEC's transitioned to the Soft Alternate Mode with the Captain's airspeed indicating stall and an inaccurate transponder #1. ADIRU 2 data was functional and indicating an overspeed. Descending out of FL180 all systems returned to normal.