Many years ago I was flying a 737-200 to Manila. Due noise abatement we were kept high at 4000 feet until localiser intercept which was around 8 miles where the glide slope should have been on slope at 2400 ft. We expected full scale fly down at LLZ intercept but instead the glide slope indicator on both captain and F/O ILS showed only slightly high by less thah half a dot. Cloud tops were 3000 ft and base 1200ft. Despite full flap and idle thrust we stayed on the apparent glide slope which gave a well over 1000 fpm rate of descent. Ground speed showed no wind. We broke visual around 1500 ft and the runway perspective showed we were definately high with glide slope indication just slightly high. The T-VASIS was useless with red and white lights in unlikely combinations.
Landed Ok and sent report to Manila ATC. A year or so earlier, an Air Manila (?) Boeing 707 from Guam had crashed short of the runway in perfect weather. A couple of fatalities I think, and the captain swore he was on the ILS glide slope right down to impact. In other words he blindly followed his instruments (even though the sink rate was out of this world).
The ILs was tested shortly after we had complained, and the calibration aircraft reported a perfectly flyable glide slope around seven degrees as well as three degrees. This was the result of poor maintenance and it was just by luck we picked it up because of the initial high vectoring. If other aircraft had had similar experience they did not report it. It also explained that the 707 pilot was probably telling the truth a year earlier when he said he followed a steady glide slope to impact.
Asked by the investigators why he didn't go around from the obviously unstable approach, he replied he thought the noise of all engines spooling up from idle thrust would only frighten the passengers! At the time of impact the 707 had full flap, speed brakes extended and idle thrust with a sink rate of around 2000 ft per min. Obviously the captain was a proponent of the saying "Real Men don't go around."
The T-VASIS? The all over the place T-VASIS was caused by severe earth tremors a few days earlier which moved the light boxes. When asked why the T-VASIS was not turned off when it was obvious that damage to the boxes had occurred, ATC advised they were abiding by a standing directive that the T-VASIS must be switched on for all jet arrivals. The Directive omitted to say the VASIS must also be serviceable.. .