B737 Undifferentiated or Other Model
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Situational Awareness; Human-Machine Interface
Deviation - Altitude Overshoot; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented
Human Factors
Altitude report deviation. Doing the approach ILS [Runway] XX; we were cleared by ATC to descend to 3;500 ft. We set 2;500 ft. by mistake in the altitude window during instructions. While descending ATC contacted us due to the mistake. We realized we began to correct the altitude again to 3;500 ft.; so ATC gave us again a clearance to stay at 2;500 ft. We continue the approach without any incident from present position.Instruction were for the approach to maintain heading and altitude; after that we were cleared for the approach for ILS [Runway] XX. At that time the wrong altitude was set in the altitude window and we didn't realize the error until ATC notified for the deviation.We started to climb immediately climbing to the correct altitude; but ATC asked to stay at the altitude we were of 2;500 ft. without any problem.
On approach for ILS [Runway] XX; ATC cleared us to descend to 3;500 ft. 2;500 ft. was mistakenly set in the altitude window when given our instructions. We descended to 2;500 ft. and ATC contacted us regarding the error. We started to correct our altitude to 3;500 ft. when ATC gave us a new clearance to remain at 2;500 ft. The ILS approach to [Runway] XX was executed without further incident.We received our instructions for the approach to maintain heading; altitude; and were cleared for the ILS [Runway] XX. During that moment the wrong altitude was placed in the altitude window and was not caught until ATC notified us of the deviation.As stated our reaction was to correct immediately by climbing to the appropriate altitude of 3;500 ft.; but we were given a new clearance to stay where we were at 2;500 ft.
B737 flight crew reported an excursion from assigned altitude occurred during the approach because they set the wrong altitude in the window.