Honeywell Delivers 10 Percent More Thrust For Learjet 40/45 Replacements
Honeywell has shipped the first two new TFE731-40BR engines to Bombardier for the airframer’s new Learjet 70/75 program. The new engine adds 10 percent more takeoff thrust by replacing the -20AR or -20BR engines in the Learjet 40/45 with the -40BR. “We’re turning up the wick, and putting more power to it,” said Michael Bevans, Honeywell director of technical sales, Business and General Aviation.
The engine maker expects certification of the 3,850-pound thrust TFE731-40BR by the end of this year. The added engine performance and other Learjet 70/75 features will improve hot-and-high field performance by up to 9 percent and fuel efficiency up to 4 percent.
The key difference between the TFE731-20AR and the -20BR or -40BR is addition of an yttria-stabilized zirconia (YSZ) oxide ceramic coating on the high-pressure turbine shrouds and on the duct between the high- and low-pressure turbine (other applications for YSZ ceramics include tooth crowns, because of their hardness).
“The main trick for us was [the customer] wanted 10 percent more thrust without changing the length, weight, plumbing, bleed-air and electrical components,” said Bevans. The -40BR requires no changes in the nacelle or engine/airframe interfaces.
Other changes include improvements to the high-pressure turbine and first-stage low-pressure turbine, he explained. “We left the compressor and fan alone.” The -40BR will have an improved TBO and hot-section interval, to 6,000 and 3,000 hours, respectively, similar to the -20BR.