An important event was also recorded in 1972 in the field of aeronautical engineering. The Air Force had felt for some time, the need to enhance the flight endurance, speed and comfort of its De Havilland Heron MK11D aircraft. The task was entrusted to the Technical Maintenance Depot, Katunayake by Commander Mendis. The Technical Maintenance Depot was headed by Group Captain M. Herbert Marasinghe, who had as his deputy, Flight Lt N. (Jim) Gunaratnam.

At this time a conversion had been successfully effected overseas, by Jack Riley of the USA. Jack Riley was written to; he came to Ceylon, had a look at the workshops and was satisfied that the work could be undertaken. He then sent the blueprints, together with new engines and upholstery etc. - but the main component was the drawings.

The conversion entailed the replacement of the Herons existing four Gypsy Queen MK30 engines, with AVCO Lycoming IO540 s - which were lighter in weight and more fuel efficient. The new engines also significantly increased power from (in approximate terms) 280hp to 340 - 360hp.

The 17-seater cabin was converted into two luxury compartments of four seats each with a jump seat for a steward. Heater cabinets were installed for storage of refreshments and a compact fully equipped toilet was introduced in the rear cabin.

All in all, a super luxury flying machine was produced by the Air Force over a quarter century ago!