Originally Posted by
Tee Emm
Back in the 1980's I was flying a 737-200 radar vectored for Manila ILS 24. If I recall we were initially coming from Guam (PGUM) and over a VOR called Jomalig. The radar vector kept us at 4000 ft until intercepting the Localiser. We were above low cloud. We did not get established on the localiser until around 8 miles and were fully configured at VREF+5 in anticipation of having to descend quite steeply to intercept the glide slope from above.
At 8 DME ILS we should have been around 2400 ft but were at around 1000 feet higher due poor radar vectoring. Yet the ILS glide slope indication showed half a dot high instead of full deflection too high.
The DME versus height simply wasn't working out. We broke visual about 4 miles out and obviously very high yet the glide slope showed on slope. The TVASIS was all over the place and displayed obviously erroneous light signals. We landed safely and I reported to ATC I thought there was a false but flyable glide slope at about five degrees. I also reported the TVASIS lights were useless for guidance.
A few weeks earlier a Air Manila (?) Boeing 707 had crashed short of the runway at a high rate of descent. I think everyone survived but the crew swore they were on glide slope all the way to impact. I wondered if they had followed a false but flyable glide slope to impact. On my return through Manila from Hong Kong a couple of weeks later my inquiries revealed that a calibration flight test on the 24 ILS did indeed find a flyable glide slope at 5.5 degrees. Also the reason for the TVASIS being useless was that there had been earth tremors which displaced the TVASIS installation. I asked in that case why was the TVASIS left switched on when it was obvious erroneous indications were likely and why no NOTAM? The answer came back that it was policy to have the TVASIS on for all jet aircraft landings. Words failed me.
interesting report. Obviously still vivid in your memory. False G/S capture from above us a very real and present danger. Cross check of fix altitudes is vital once established to mitigate.