FARNBOROUGH, England, July 22 (Reuters) - U.S.

aero-engine maker Pratt & Whitney is set to announce on Tuesday

that aircraft leasing company Avolon will select its GTF engines

to power 80 Airbus A320neo aircraft, an industry source

familiar with the matter told Reuters.

The order comes as Pratt, a unit of RTX, contends

with problems with its GTF engine that have grounded aircraft.

RTX declined to comment.

The order would be one of Pratt's largest transactions with

a lessor for its GTF engines.