Description

On 5 January 2014, a Boeing 737-800 (VT-SGU) being operated by SpiceJet on a scheduled domestic passenger flight from Goa to Dehli SG 256 was unable to land at its destination due to visibility below applicable approach minima and diverted to Jaipur. Whilst on approach there, the A320 aircraft ahead was "substantially damaged" during landing and blocked the only available runway. The 737 crew declared a MAYDAY and returned to Dehli where a priority below-minima landing was made in night IMC.

Investigation

An Investigation was carried out by an Indian AAIB Committee of Inquiry. The SSFDR and 2-hour SSCVR were removed and their data downloaded. The SSCVR data covered the period from the hold prior to initial approach vectoring at Delhi onwards.

The Captain was Cat II qualified and had 6,410 hours total flying hours which included 2,003 hours in command on type. The First Officer was Cat III qualified and had 1,996 total flying hours, of which 1,743 hours were on type.

It was established that the 2½ hour flight from Goa to Dehli was scheduled to arrive at Dehli at 2015 local time. The TAFs provided prior to departure from Goa indicated that a deterioration in visibility from 800 metres in fog to 400 metres visibility in fog at Delhi was expected to occur soon after the STA. The pre-departure forecast visibility at both alternates, Lucknow and Jaipur, was the same - 2000 metres. Departure was almost on schedule and an extra 500 kg of fuel was carried for expected holding at Dehli. Nearing Delhi, ATC instructed a speed reduction and advised that the aircraft was No 13 to land. The ATIS at this time was giving landing runway RVRs well above Cat II, the prevailing crew qualification. However, subsequently, as the aircraft was being radar vectored towards an ILS approach to runway 28 at 7,000 feet, the roll out RVR for that runway dropped below Cat II limits and a hold was resumed. This was continued for almost half an hour but the RVR for both runway 28 and runway 29 remained below Cat II limits and the Captain decided, following a request from his Company flight dispatch, to divert to Jaipur. The aircraft still had 3,100kg of fuel on board and Jaipur, a half hour flight away, required 2,573 kg. The other FPL alternate, Lucknow, was further away but the aircraft was not below its corresponding Minimum Diversion Fuel (MDF). However, given the request from flight despatch (based on the fact that it would be easier to recover the aircraft from Jaipur but also in the knowledge that visibility was expected to deteriorate), the weather for Lucknow was not checked. The crew had themselves obtained the Jaipur weather whilst holding and had learned that the visibility was 900 metres in fog patches with the relevant RVR 1,500 metres.

By the time the aircraft was descending into Jaipur, ATC advised that the visibility had dropped to 50 metres and the relevant RVR was 200 metres. By this time there were no other suitable alternates with MDF available and so despite not yet being short of fuel, the crew were committed to landing at Jaipur. Then, with the aircraft at 5nm finals, ATC advised that the aircraft ahead had crash landed and blocked the runway, and the Captain immediately began the return to Dehli having estimated that there was just enough fuel remaining for an immediate approach there whatever the visibility. On contact with Dehli, and with 1,200kg of fuel remaining, a MAYDAY was declared and the flight was cleared to make an emergency landing. A priority dual channel auto ILS to runway 28 was successfully accomplished with the reported RVRs 375 metres/900 metres/50 metres. It was found by the Investigation that "the visibility at the time of landing was almost nil". There was sufficient fuel remaining after landing (400 kg) to taxi to the assigned parking gate where it was found to be down to 150 kg.

The Investigation found that the Jaipur TAFs during the period prior to the series of Jaipur diversions, which had included the flight under investigation, could not be correlated with the weather conditions subsequently experienced. It was also found that on the day of the event, Jaipur was not appending TREND reports to their METARs and SPECIs, but it was noted that these had begun to appear on their METARs the following day. It was found that when the flight had been inbound to Delhi the first time shortly after sunset, although both Lucknow and Dehli were reporting 2,000 metres visibility, the former had an Air Temperature / Dew Point split of 4° whereas at Jaipur, both were already the same.

It was considered that given the considerable prevalence of winter diversions from Dehli, most of which show the same two (single runway) FPL alternates - Lucknow and Jaipur - as in this case, lessons about risk management of these diversions could be derived from an analysis of experience across all the airlines involved which does not presently happen.

It was noted that Spicejet had a winter 'Fog Plan' which required all flights inbound to Dehli between 2000 and 0930 local time to be operated by Cat IIIa qualified crews, but it had not been followed in the investigated case since only the First Officer was so qualified.

It was concluded that it was "the timely diversion from Delhi to Jaipur i.e. with fuel on board above the MDF required for Lucknow (the safer alternate) which had made it possible for the aircraft to reach Delhi after the diversion (back) from Jaipur". It was also accepted that "carrying out a direct auto land into Delhi in visibility which was below that for which the crew was qualified was the safest (available) action".

The formal determination of the Investigation in respect of Probable Cause was that the emergency landing due to low fuel occurred because:

• The aircraft had to carry out a second diversion with low fuel on board from the chosen alternate airport to the original destination airport due to blockage of the runway by another aircraft (VT-ESH) which had been substantially damaged during landing at the alternate airport.
• There was a lack of operational supervision and desirable ground support to the in-flight aircraft crew.
• There was a lack of effective oversight of flight operations.
• A more appropriate initial diversion from the destination airport due to low visibility conditions there would have been Lucknow instead of Jaipur.

A total of 5 Safety Recommendations "additional to those made as a result of the separate Investigation into the landing accident to the aircraft ahead of this one at Jaipur", which had been identified as "generic in nature", were made directly as a result of this Investigation as follows:

• that the Flight Operations Departments of All Scheduled Airlines must ensure that suitable airports with relatively better forecasted weather conditions are planned as alternates during the fog season.
• that the Flight Operations Departments of All Scheduled Airlines must increase the comfort level of flight crew during fog season by encouraging them to uplift additional fuel under their discretionary powers.
• that the Flight Operations Departments of All Scheduled Airlines must ensure that crew scheduling strictly follows the instructions documented in the Fog Plan regarding crew qualifications.
• that the Flight Operations Departments of All Scheduled Airlines must ensure that safety audits of flight operations verify that alternates are filed as per the criteria defined in DGCA CAR Section 8, Series C, Part 1.
• that the Flight Operations Departments of All Scheduled Airlines must ensure that Flight Dispatchers and Operations Controllers provide regular updates of weather which will assist aircraft commanders in making diversion decisions which keep the safety of aircraft and passengers in mind.

The Final Report was completed on 29 August 2016 and released without restriction on 28 February 2017.

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• A320, Jaipur India, 2014