Large Transport
Flight Crew Air Transport Pilot (ATP)
Situational Awareness; Human-Machine Interface; Confusion; Distraction
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Other / Unknown; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented
Aircraft; Human Factors
We were cleared to track the localizer to [Runway] 5R; descend to 3;100 FT MSL; maintain 180 KIAS until NURVE (glideslope intercept). [We were] cleared for the ILS contact Tower. The First Officer 'bowtied' the 180 KIAS while the hollow magenta ball was still up above 200 KIAS and he was using 'vert speed' down that was getting us to 3;100 FT somewhat early but we were told to carry the high speed so it was not a big concern. Slats were extended and we had flaps 15 by the time we hit NURVE. NURVE was a point where a lot of things were going to happen. (i.e. further configuration and start slowing to approach speed). We were also just getting through the cloud deck at that point and because of the low (both angle and lumens) light and generally grey lighting it was not easy to see all the details of the airport. We intercepted the glideslope; and started slowing and configuring. I was watching the speed closely because I wanted to back the First Officer up if the hollow magenta ball became active and he missed that event--he caught it and everything looked normal while we worked toward a stable approach speed. As I was accomplishing the configuration changes I was pretty much heads down to make sure we were getting the speed right and were on the ILS guidance. Did not know anything was abnormal until Tower called and said we had tripped their altitude alerting system. I think we had just passed 1;000 FT AGL. Sure enough it was 4 red lights on the PAPI! but the glideslope still showed us on glideslope. The First Officer; flying manually; quickly broke the descent rate to get on the PAPI; stabilized by 500 FT and we continued for a safe landing. The whole time the glideslope indicator in the cockpit did not show much deviation at all; never more than 1/3 of a dot. And we confirmed that we still had a good lock on I-OQV. As we landed we noted that there was an MD-11 holding short of Runway 5R; and I think it is very likely that interfered with the ILS guidance. Departing aircraft have to tune I-OQV for departure. I wrote the event up in the logbook so Maintenance could see if there had been a problem with our equipment but I don't know if they found anything. I called Indy Tower to thank them and see if there had been any problems with their systems to which they advised their systems all showed normal. We never got any aural warnings from onboard systems; glideslope; terrain; etc. I suspect that the aircraft at the hold line (which we noted on our subsequent departure was well past the ILS hold line) interfered somehow with the ILS guidance. From a CRM/Human Factors standpoint I am very concerned about this event especially in light of recent training cycle and a conversation with one of our check airmen who is deeply involved with CRM training. We both discussed the advisability of being fully configured much sooner than 'the feather' so the pilot not flying can monitor all available inputs as opposed to being 'heads down' configuring and running checklists and changing radio frequencies; etc. at this crucial point. If those actions are paced more evenly the pilot not flying will have a better chance of noting deviations. It also makes the bio feedback of multiple speed and configuration changes a better indicator of 'something not right' if they are not all happening at once. We all try to fly as efficiently as possible but the additional gas spent by configuring a little further out is a cheap insurance policy so the pilot not flying can perform the duties required.
At NURVE I Speed Selected 160 KTS and asked for flaps 22. The jet started its descent on the glideslope at NURVE as normal. I stated I had the runway in sight; but the PAPI was not visible due to the hazy condition. Shortly thereafter I noticed the speed increasing back to 180 KTS after we had slowed. The ILS raw data showed just slightly below the glideslope with the Flight Director bars centered. I didn't like how the autopilot was following the glideslope and unusual increasing airspeed. I disconnected the autopilot and said it wasn't following the glideslope correctly. I called for the gear down and Landing Checklist. I raised the aircraft's pitch slightly. The airspeed was slowing now. I had also selected FMS speed for the Vapp at 145 KIAS. Tower called with a low altitude warning. I estimate the altitude on the approach at that time was 1;680 FT MSL. Just then the PAPI came into view and showed four red. I also disconnected the autothrottles; added power; and raised the pitch attitude to stop the descent. Immediately the PAPI then showed slightly low. I continued to correct the aircraft's flight path via the PAPI and we made an uneventful landing. All this time the raw glideslope data showed on glide path. There were never any aural or visual warnings in our cockpit. I wish the ILS approaches still had the markers. They are being decommissioned. They were great to cross check your altitude on the ILS glideslope. Always back up the automation.
When ATC advised the flight crew of Widebodied cargo jet of a low altitude alert while flying the ILS to visual conditions at IND the jet descended below the overcast and the crew noted four red PAPI lights although their glideslope indicator showed them within acceptable limits. When they corrected their path per the PAPI the glideslope indicator failed to reflect their altered vertical path. Although the reporters' noted an MD11 parked in the vicinity of the glideslope transmitter they opted to write up the anomalous glideslope indication.