General Electric TF39 Turbofan The General Electric TF39 was the first high-bypass turbofan engine. Very fuel efficient, turbofan engines are useful for military and civilian transport aircraft where high speed is not a priority. General Electric developed the TF39 in the mid-1960s to power the Lockheed Martin C-5 Galaxy. Beginning in 2006, the U.S. Air Force initiated the Reliability Enhancement and Re-engining Program (RERP) to replace the TF39 with the more powerful General Electric F138 turbofan engine. This upgrade will allow the enhanced C-5M Super Galaxy to perform reliability long into the 21st century. TECHNICAL NOTES (General Electric TF39-GE-1C): Compressor: Two-spool high-bypass axial flow Turbine: 1.5 stage fan Thrust: 43,000 lbs. Weight: 8,000 lbs. Bypass ratio: 8:1 Click here to return to the Global Reach Gallery.