SpiceJet flight SG-8956 departed Srinagar airport on 23 May 2019. While approaching New Delhi airport that evening, there was a thunderstorm in the vicinity of the airport. The aircraft was cleared for an ILS approach for runway 27.
The approach to this runway is in close proximity of the prohibited area VIP-89. Once the aircraft is established on the approach, there are two runways and their approaches to the left and the prohibited area to the right. The only escape is the missed approach procedure straight ahead.
Sandwiched between the approach for other 2 runways on the left and prohibited area on the right, the SpiceJet aircraft probably detected a hazard in the form of a thunderstorm ahead. The choice is limited to either the devil or the deep blue sea. SG decided to turn right thereby infringing the prohibited airspace.
As reported in the media, the deviation was detected by the controllers and an immediate left turn was directed. It was too late to prevent infringement.
Annex 10 defines the term “distress”. Distress: a condition of being threatened by serious and/or imminent danger and of requiring immediate assistance. A “Mayday” call is given for this purpose.
Is a “Mayday” appropriate in this context?
The definition can be broken down to have a better understanding.
Encountering a thunderstorm at low level can be a serious environmental threat. The risk could range from injuries from turbulence to structural damage to the aircraft structure. Avoidance procedures would entail circumnavigating the thunderstorm. The conundrum would be to either turn left and encounter/avoid other aircraft on the approach to parallel runways or turn right into a prohibited airspace.
The crew in this scenario turned right and infringed the prohibited airspace. In my opinion, a “mayday” call is appropriate in this scenario. There was a conditioned of being threatened by serious danger and immediate assistance was required.
The general perception that a “Mayday” call is required to be given only when the aircraft is affected structurally or due to a system failure. The intent is to seek immediate assistance for something that is likely to pose a serious and/or imminent danger.