Full version In short
ICAO (a United Nations Agency) Annex 6 to the Convention on International Civil Aviation, Part 1 states in paragraph 18.104.22.168:
"An instrument approach shall not be continued below 300 m (1 000 ft) above the aerodrome elevation or into the final approach segment unless the reported visibility or controlling RVR* is at or above the aerodrome operating minima."
The above paragraph has been enshrined in Polish law by the ministerial decree on the subject of aviation safety dated 5th November 2004 (Dz. U. z dnia 10 grudnia 2004 r.):
"…the approach shall not be continued beyond the outer marker, or equivalent position, if the reported RVR*/visibility is less than the applicable minima... "
"... the pilot to whom conduct of the flight has been delegated shall make the decision to continue or abandon the approach before descending below 1 000 ft above the aerodrome..."
The minimum required visibility for the approach available in Smoleńsk on that day:
The actual visibility reported to the pilots that morning:
In accordance with the above regulations and law, descending below 1,000 feet (300 metres) was forbidden.
(C) 2012-2016 Jan Chmielewski, all rights reserved.
* RVR = Runway Visual Range