The letter of the law versus the spirit of the law is an idiomatic antithesis. When one obeys the letter of the law but not the spirit, one is obeying the literal interpretation of the words (the “letter”) of the law, but not necessarily the intent of those who wrote the law. Conversely, when one obeys the spirit of the law but not the letter, one is doing what the authors of the law intended, though not necessarily adhering to the literal wording.

Question

Why did the crew divert to Lucknow instead of Jaipur and end up in a messy situation where they had to declare MAYDAY? Jaipur was closer and as seen there was no weather but Lucknow was full of weather enroute and went below the required visibility on arrival overhead.

Did the company policy play a role in crew decision making?

How did the company dispatch/IOCC and ATC assist the flight?

Before the critics go on a rampage, let me state that the final authority for the safe disposition of the aircraft rests with the commander of the flight. The intention is to highlight contributory causes.

Facts

The weather image superimposed on the aircraft flight path shows:

1. The crew held over Rewari, close to Delhi before proceeding to Delhi for the approach and landing.
2. Apparently the landing could not be successfully carried out due to tail winds for the westerly runway. That was a good decision.
3. A diversion was immediately carried out to Lucknow.
4. The direct track to Lucknow would have been the shortest but as the weather picture shows, was full of widespread weather.
5. The crew elected to fly south towards Agra, depicted in the yellow coloured path.
6. They flew past Jaipur on their right and south of Agra turning left towards Lucknow.

The company statement

The company concluded even prior to an enquiry that the reason for ending up low on fuel was due to unexpected drop in visibility at the designated alternate.

For the Vistara flight, Lucknow was suitable alternate whereas Jaipur was an acceptable alternate.

mindFly analysis

It is clear from the policy for choice of alternates that a suitable airport, in this case Lucknow will be chosen as an alternate over Jaipur which was an acceptable alternate. The reason being if there is marginal weather at destination, an acceptable alternate (Jaipur) cannot be chosen as the alternate.

Despite the availability of Jaipur and no weather activity reported except haze, the crew persisted with tracking to the suitable alternate after negotiating enroute weather.

The crew was so policy driven and did not divert to the obvious choice of Jaipur as alternate. The crew went by the rule and not the spirit of the rule.What the policy did not address in the matrix is if the suitable alternate weather is marginal, then which alternate can be chosen. The logical answer would be Jaipur and in this scenario the crew should have diverted to Jaipur and could have avoided the tense few moments.

It is the responsibility of the company flight dispatch to assist the commander by tracking the flight and providing weather and alternate advisories.

ATC could also have coordinated with Lucknow ATC and advised the flight crew that there is a possibility of a reduction in visibility due oncoming weather.

Since there were so many agencies who could have prevented this situation of low fuel, the regulator decided to allow the crew to return to active flying after a brief period of suspension in an unprecedented letter written justifying their actions.

It is therefore imperative to explain the spirit of the rule prior to writing the rule.