DGCA has also permitted the airline to deploy newly-inducted planes for capacity expansion.
The Directorate General of Civil Aviation (DGCA) has given IndiGo time till May 31 to replace unmodified Pratt & Whitney (P&W) engines on its Airbus A320Neo aircraft.
It has also permitted the airline to deploy newly-inducted planes for capacity expansion.
In November, the regulator had set January end as the deadline for replacing the unmodified engines following repeated incidents of mid air engine shutdowns and aircraft returning to the departing airport.
The deadline has now been relaxed and restrictions on use of new planes for new routes or additional frequencies has been eased.
The airline had cut down its capacity expansion outlook in the fourth quarter as well as the full year following the earlier directive.
IndiGo operates over 257 aircraft, including 106 Airbus A320/321Neos.
While latest batches of the aircraft have modified engines, the older ones in the fleet require changes to address failure of low pressure turbine blades.
Initially, the number of engines requiring replacement was estimated at 120 but now that has increased to 135, following additional inspections and inquiry to find the cause of failure.
“The process of placement of at least one modified engine on the entire fleet has been accomplished by IndiGo well before the timeline of March 31, given by European Aviation Safety Agency Airworthiness Directive. Moreover, about 70 per cent of the total Neo engines of the IndiGo fleet is likely to be modified by January 31,” the DGCA said in its update on Monday.
It added that procurement of modified engines was impacted due to Christmas and New Year holidays.
In their action plan, Airbus and P&W submitted that the replacement of all 135 engines will be completed by June.
DGCA has, however, asked them to complete the task by May end.
No aircraft with unmodified engine in the IndiGo fleet will be allowed to fly after that date, it said.
“Mitigation measures put in place such as introduction of inspections of mid turbine frame (MTF) piston seal in addition to existing inspections and aircraft climb procedures, will help in containing engine failure on the wing,” said the DGCA.
P&W had identified fracture of the MTF piston seal as the cause of 50 per cent of engine failures.
The DGCA order is likely to have an impact on future capacity, IndiGo said last month. It expects a year-on-year capacity increase of 15-20 per cent in Q4FY20 and 22-23 per cent in FY20.
The previous forecast was 22 per cent for the third quarter of FY20 and 25 per cent for FY20.
However, that will not harm the airline’s profitability, it said, while retaining its profit forecast.
Photograph: Vivek Prakash/Reuters