Date: 201704
Local time of day: 1801-2400
Location: IND.Airport, IN
Flight conditions: VMC
Light: Night
Aircraft: Medium Large Transport; Low Wing; 2 Turbojet Eng
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Final Approach
Airspace: Class C IND
ATC / advisory: Tower IND
Second aircraft: Large Transport; Low Wing; 2 Turbojet Eng
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness
Second reporter function: Captain; Check Pilot
Anomaly: Inflight Event / Encounter Unstabilized Approach
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew FLC Overrode Automation
Contributing factors: ATC Equipment / Nav Facility / Buildings; Human Factors
Primary problem: Human Factors

Narrative: We were in the process of flying an uneventful approach at the end of an uneventful flight. The approach was the visual approach to runway 32 in IND. We were following an aircraft and another aircraft was about to depart and we assume that one of these aircraft; perhaps both; interfered with the glideslope signal. As is usual; we were backing up the visual approach with the ILS and on autopilot as well.When the interference occurred; it was sudden and surprising in intensity. I have seen this occur many times throughout the years; and without question this was the worst I've seen. As the glideslope deviated upward; the aircraft of course went with it and initiated a steep pitch attitude and almost full power. The first officer (FO)was caught unaware as this was new to him; and in the moment's indecision; I assumed the controls and stabilized the aircraft. I was able to return to a stable configured flight path at about 1;100-1;200 ft; and decided to maintain controls for the remainder of the approach; as I didn't feel it appropriate to transfer controls at that point of the approach. We then landed without further incident.A check airman was on the jumpseat and was able to provide some added and informed insight to a discussion we all had upon reaching the parking point. The FO seemed slightly shaken; and we veterans were surprised as well; at how quickly the aircraft reacted to a disrupted glideslope indication. The pitch and power inputs were drastic; personally; I'd like a download of the data to see just what it did. It was a vivid demonstration to the FO of what this particular situation can do to a pilot in that you can have a pristine day that suddenly goes wrong. Without intervention; I'm not sure what state the aircraft would have achieved with the oscillation that followed. The downward pitch and excessive power input would probably have resulted in a potential CFIT threat.As well; indecision as to what action to take can create issues hazardous to a positive outcome of the flight. Absent a decision to correct the flight path or to call for a go-around; I needed to intervene; which provided a vivid and excellent teaching moment for the FO who now has seen an authentic representation of how quickly scenarios can change in this environment. We decided to report this since we do believe it was an upset. There may be an issue with the glideslope itself and may need to be addressed by the airport authority as this scenario is easily repeated. The only way to get experience is to get experience. The FO needed it; and now he has some more. Because I have some; we corrected it to an uneventful outcome.


Second narrative: While on final approach to IND RWY 32 at approximately the FAF; IND Tower cleared an aircraft onto RWY 32. The aircraft passed through and interrupted the RWY 32 Glide Slope transmission. The FO had the FMS coupled to the ILS 32. The disruption caused a GS indication that was nose high (estimated 10 degrees) which the autopilot (AP) tracked and the autothrottle advanced to takeoff thrust. FO's reaction to this inflight upset was delayed; (fixation/confusion on the abrupt pitch/thrust change); prompting the CA to announce; and take the flight controls. The CA immediately and smoothly returned the aircraft to the ILS glide path and because being in a critical phase of flight; landed the aircraft.Several contributing factors.1) FO was on a line check with a check airman jumpseat observing him. He was a little nervous. 2) Weather was clear with light to moderate winds. This crew was performing well and were literally minutes away from landing.3) FO was a recent new hire. Because of that; I am assuming he had low time in CFR Part 121 operations.4) FO described that he had never encountered this kind of GS anomaly before and was unfamiliar with ground GS aircraft disruptions.Crew knowledge and experience are the only way to prevent this event.Conclusion: Excellent rapid control by the CA. Excellent learning experience for the FO.


Synopsis: Air carrier flight crew reported an interrupted glideslope signal at IND caused the aircraft to pitch up while on autopilot. The Captain took control from the First Officer and landed the aircraft.