What happened
On February 10, 2016, at approximately 22:45 UTC, a Boeing 777-200ER, registration VP-BHB, was performing a commercial flight from Punta Cana International Airport (MDPC) to Moscow Domodedovo (UUDD). While climbing through 12,000 feet, the number one Pratt & Whitney PW4090 engine experienced a malfunction characterized by high temperatures and visible smoke in the cabin.
The flight crew responded by shutting down the affected engine and declaring an emergency to perform a return to the departure airfield. During the subsequent landing and taxiing phase, the main landing gear braking system overheated, leading to a tire deflation and a fire in the main gear assembly. All 370 persons on board (347 passengers and 23 crew members) were evacuated safely and sustained no injuries.
The investigation
The CIAA investigation focused on the mechanical failure of the engine and the subsequent braking event. Digital Flight Data Recorder (DFDR) analysis revealed a sudden, massive increase in vibration levels on the N2 shaft, exceeding 5.0 on the EICAS scale.
Subsequent borescope inspections of the number one engine revealed significant internal damage. Investigators found that the high-pressure turbine (HPT) second-stage blades had fractured. This breakage caused a severe imbalance, leading to high-friction rotation within the high-pressure compressor (HPC). The inspection also identified material loss from the tips of the compressor blades in stages 6, 7, and 8, as well as damage to the low-pressure turbine (LPT) stages due to impact from debris.
Regarding the landing gear, the investigation established that the overheating of the brakes during taxiing triggered the tire deflation system and resulted in the fire.
Findings
- Multiple fractures in the second-stage high-pressure turbine (HPT) blades caused a significant rotational imbalance.
- This imbalance led to unrecoverable compressor surge and high-friction contact between rotating components in the high-pressure compressor (HPC).
- The loss of material from the HPC blade tips was a primary factor in the engine's malfunction.
- The overheating of the main landing gear brakes acted as a contributing factor to the secondary emergency involving the tire deflation and fire.