I recognise that many airports in the world have a “skin-tight” adherence to obstacle zoning restrictions. This is too frequently due to the lack of “Officials’ ” willingness (balls$) to enforce or legislate restrictions.
I realise that it is sometimes due to a question of topography . . . where else can you put the airport given the mountains, valleys, buildings, etc.!? This was not the case in Halifax
I don’t accept that citing the failures of others is justification or a rationale for taking the cheapest or easiest way out of a design problem.
I also recognise that frangibility and zoning restrictions have had very little impact on reducing the number of recorded incidences of accidents. These restrictions have however, (when properly observed) been significant in reducing the “consequences” of accidents (sort-of the whole idea?).
In this particular incident, the previous antenna was mounted on a structure deemed frangible. The replacement (upgraded) antenna was not placed on a comparably frangible structure. Why? ($$$$$?). Better yet, why not the frangible structure that existed (with some refurbishing)?
There remains some 400 feet plus, of clearway/stopway behind the structure in question, (still on airport property) followed by a hundred feet plus of rather scraggly trees (still on airport property).
(for scale;
- the antennae/concrete slab is ~ 130-ft. wide.
- also, frame centre high, a little right of runway extended centre-line, is the entire tail section of the 747).
(Hmmm . . seems either TSB or PPRune don't like linking their photos?? . . . ASP's a problem? . . . you've got the link . . . take a look)
Looking closely at the 16 antennae sitting on the concrete (the little orange things sitting on the grey slab), it appears that only 9 antennae are missing. The width of the structure that impacted the antennae would appear to be something about 65-ft. or less . . . too small for the wings . . . too big for just the fuselage?
Also note that there appears to be “orange confetti” behind the antennae. The confetti is actually what is left of the antennae (post-impact). Nice that the 10-ft tall antennae were frangible . . . unfortunately, the 20-ft. high mound isn’t.
Zoom in on the centre of the antennae mound. The stuff sticking out in front of the concrete slab (just left of centre-line) is a/c fuselage from the tail impact on the concrete/mound.
If someone is installing or refurbishing an airport facility (ILS), within the airport property, with 400-500 plus feet of airport property clearway/stopway behind you, the antennae facility is fully frangible (in accordance with ICAO’s latest requirements), the existing structure is deemed frangible, all the approach lights around you are required to be frangible (ICAO), why would anyone choose to replace a frangible gantry with a 20-ft. high concrete, rock, and earth mound to elevate the antennae?$?$?$?