Originally Posted by
gearlever
That's what the DGCA reported (from AvH)
" At Lucknow while 17nm from the runway ATC informed the crew that the runway visibility had dropped to 475 meters RVR (600 meters required) and was further reducing to 275 meters, the crew discontinued the approach and climbed to 4000 feet. When the fuel remaining reached 1260kg/2775lbs the crew declared minimum fuel and at 1100kg/2423lbs declared emergency. The crew decided to divert to Kanpur but subsequently decided to divert to Allahabad due to enroute weather. The aircraft climbed to FL100 when ATC informed the crew Lucknow was now showing 600 meters RVR and a few seconds later the RVR had increased to 1000 meters. The aircraft was 37nm from Lucknow and 58nm from Allahabad at that time, the crew decided to return to Lucknow and landed on runway 27. The aircraft landed with 260kg/572lbs of fuel remaining on board. "
1.100kg fuel at 4.000ft and divert to Allahabad....!?
Technically speaking, if you start the diversion right at minimum diversion fuel, when reaching the alternate you are left with final reserve (single alternate scenario). If we add to that a possible extra fuel burn to reach the alternate due to some weather avoidance, we can easily end up with even less than reserve. This is why I have always thought that legal fuel planning must take into account some contingency even for the alternate routing, as it does for the destination trip fuel. The right amount of fuel to start the diversion is often left to crew assessment / experience and, in case some elements are not fully considered (ie. enroute weather, extra track miles, etc..) there is no safety net but infringing the reserve and therefore ending up in a mayday fuel.
If the crew started the diversion right at MDF with a pretty decent weather report for VILK, they were legally covered, only to find out that from an operational point of view they would be trapped shortly afterwards. We could also imagine a CAVOK weather at VILK and the crew having to go around because the preceding traffic went off the runway, hence ending up very close or at final reserve.
I believe we all put our personal safety nets in those kind of scenarios, to cope with a lack of regulation, like diverting at, let's say, minimum + 500 kg or so depending on the circumstances / experience, but a misjudgement in such a situation can very quickly end up in big problem.
Edit : we do not know how long it would have taken to change the runway in VIDP and re-accomodate all the traffic.