* Pratt to outline fix for combustor liner - source
* New liner design expected to go into production this year - source
* Problem more acute in India due to pollution, weather extremes
By Aditi Shah
NEW DELHI, Oct 17 (Reuters) - U.S. airplane engine maker Pratt & Whitney is close to outlining a fix for problems with the combustion chamber lining in its new Geared Turbofan (GTF) engines, which have hit deliveries of Airbus A320neo planes, a person aware of the issue told Reuters.
Pratt & Whitney, owned by United Technologies, has had three teething issues with its GTF engines for the Airbus planes. It has fixed problems with the fan blade and an oil seal, but now faces production backlogs.
A third issue, with the combustion chamber lining, has been particularly problematic in India due to pollution and extreme weather conditions.
Indian airlines IndiGo and privately-owned GoAir are among the biggest customers for the A320neo planes, with about 30 between them today and around 500 on order.
A new design for the combustion chamber liner, to specifically address Indian conditions, is being tested, the person said, and is expected to go into production later this year. Once approved it will be fitted on all GTF engines, added the person, who asked not to be named as the tests are ongoing.
Pratt & Whitney said it is working with airline operators to fix the issues, noting that new and overhauled engines have incorporated improvements since March.
The issues with the GTF engines have grounded several of the revamped A320neo planes. In India alone, IndiGo and GoAir have grounded as many as 12 planes at one point, and cancelled dozens of flights.
A lack of spare engines kept some planes out of action for long periods, the person said. Pratt & Whitney said it has increased the supply of spares and speeded up overhauls.
"The engines have yet to go through a full life-cycle, so while Pratt has developed fixes for the fan blade and oil seal and is close on the combustor, there's no saying what may give next as the engines go through more wear and tear," an aviation industry source said.
Airbus CEO Tom Enders told the engine maker in July to "work harder" to address the problems and bring the situation back to normal.
United Technologies - whose engines compete with those from CFM International, a tie-up between General Electric and France's Safran - has invested $10 billion in developing the GTF engines. It reports third-quarter results next week.
IndiGo parent InterGlobe Aviation warned in July that new plane delivery delays were affecting profit margins, adding it was having to lease planes to make up the shortfall.
India's aviation regulator has stepped up inspections of A320neos using Pratt & Whitney engines after the issues faced by IndiGo and GoAir. (Additional reporting by Euan Rocha in Mumbai; Editing by Ian Geoghegan)