Incident Overview
On August 26, 2008, at approximately 0635 coordinated universal time (0135 local time), a Boeing 747-209B, registration N715CK, operated by Kalitta Air as Centurion Air Cargo flight 164, experienced a power loss from the number 3 engine shortly after takeoff from Eldorado International Airport (SKBO), Bogota, Colombia. The flight was destined for Miami International Airport (KMIA), Miami, Florida, under Title 14 Code of Federal Regulations Part 121. Night visual meteorological conditions prevailed, and the flight was operated under an instrument flight rules flight plan. None of the five crewmembers were injured, and the airplane sustained no damage.
Flight Crew Actions
According to flight crew statements, just after departure, as the landing gear were being retracted, a loud bang was heard from the vicinity of the number 3 engine, followed by an excessive exhaust gas temperature (EGT) indication and three or four additional bangs. The crew secured the engine in accordance with the checklist procedure, dumped fuel, and returned to the airport without further incident.
Post-Flight Inspection
A post-flight walk-around inspection of the number 3 engine revealed no visible damage. The airplane was powered by four Pratt and Whitney (P&W) JT9D-7Q engines. The operator reported that the number 3 engine, serial number P702121, had operated 210 hours since its last overhaul.
Engine Examination and Testing
The Colombian government delegated the incident investigation to the United States under Annex 13 to the Convention on International Civil Aviation. A Powerplants Group was formed. The number 3 engine was removed from the airplane and shipped to the Kalitta Air engine facility in Oscoda, Michigan, for on-wing testing on a Boeing 747-200 test bed.
Before testing, a borescope inspection was conducted. It revealed no mechanical failures within the engine and no thermal distress in the combustion or turbine sections beyond serviceable limits. Several high pressure compressor blades were found to be nicked or torn beyond engine manual limits and were repaired (blended in-situ) before the engine was run. Fan blade leading edge impressions were also made to evaluate leading edge contour and profile.
The engine was tested in accordance with P&W "Test Number 12" performance evaluation from the JT9D-7Q engine maintenance manual. Initial baseline testing showed no surge or engine exceedences. An engine vane control trim check indicated that most parameters were within limits except above 90% corrected N2 speed, where the vane angle was slightly below minimum. It was determined that this did not significantly impact testing, so the engine was not re-trimmed prior to testing with new fan blades and a new fan case.
Test Results
Based on the range of hardware conditions tested, the tests revealed that fan blade contour and shape had a greater influence on the engine’s surge margin and low pressure compressor (LPC) operating line than fan blade-to-fan case clearance variations within the test conditions. Fan blades within engine manual limits—with rounder leading edges, little to no erosion, and proper chord length—improved LPC efficiency and engine stability. The final test was conducted with the compressor variable vanes re-trimmed open and within limits at the high speed range, resulting in further improvements in LPC efficiency and stability.