Icing tests completed on a modified CFM International (CFMI) CFM56-3 in the US Air Force's McKinley Climatic Laboratory at Eglin AFB, Florida, have cleared the way for deliveries in July of core upgrade, or time on wing (TOW), kits to launch customer Southwest Airlines for its Boeing 737 Classics.

Warm winter weather had prevented CFMI from completing the icing tests as scheduled by January at General Electric's Peebles site in Ohio.

To avoid looming delivery delays, CFMI contacted the McKinley Climatic Laboratory, and test engineers worked to develop a portable test rig that would generate the appropriate amount of icing.

Peebles test engineers rigged a portable icing system in under three months that was transported to Eglin by road. The system included a spare wind generator from Peebles and a spray rig to produce a ground fog of 1g/m3 and a particle size of 15µm at temperatures down to -12°C (10°F) or lower. "We have never run an icing cloud this heavy and this fast in this facility," says McKinley test engineer Dwayne Bell.

Using data from the tests, CFMI now plans to have the kit certificated by early June and to "be in a position by July to deliver the first kits", says CFM56 upgrades model engineer Kirk Montgomery.

Production of initial kits is set to begin next month. Deliveries of up to eight a month are scheduled, with 50 kits due for handover this year. Southwest, which so far is the only customer for the TOW kits, has ordered 300 at a cost of around $1 million each. CFMI, which says the upgrade saves up to 1% specific fuel consumption per engine per year, estimates a market for around 1,000 CFM56-3 engines, or around 25% of the world fleet.

The kit, which is fitted into the engine core during major overhaul, increases exhaust gas temperature margins by an average of 15°C and results in up to 1,400 additional cycles or "an extra year on wing", says Montgomery. CFMI hopes to use the certification test work on the -3 TOW to help smooth the way for the forthcoming CFM56-5C/P upgrade for the Airbus A340 Enhanced.

Source: Flight International