Russian authorities have discovered that at least one other Boeing 737 operator has encountered engine instability arising from blade contamination during winter operations.

Federal air transport regulator Rosaviatsia states that a 737-800 of Smartavia was involved in an occurrence on 16 January while undergoing maintenance.

It says the aircraft (RA-73654) experienced alternate surges in both CFM International CFM56 engines during tests. Inspection found a “white coating” on the low- and high-pressure compressors.

The problem was resolved with engine wash procedures.

Rosaviatsia had previously indicated issues with CFM56 engines on 737s operated by S7 Airlines, and it has disclosed details of four incidents, all involving S7 737-800s.

Smartavia 737-800-c-Anna Zvereva Creative Commons

Source: Anna Zvereva/Creative Commons

Rosaviatsia has disclosed that a Smartavia 737-800 experienced engine instability during maintenance

After take-off from Novosibirsk on 8 December last year, the crew of an aircraft registered RA-73665 reported surges in both engines, and opted to return to the airport.

Rosaviatsia says the probable cause was unstable operation of the high-pressure compressors in each powerplant, owing to contamination of the compressors’ blades from “intensive” use of de-icing fluid while the engines were running.

The regulator also refers to ingestion of salts from the runway during taxiing. Under certain conditions, it says, this can lead to disruption of the airflow through the compressor blades.

Another S7 aircraft, RA-73665, aborted take-off from Ulan-Ude on 27 January this year when the crew noticed “popping noises” from both engines, says Rosaviatsia.

On the same date a similar incident occurred at Moscow Domodedovo with S7’s RA-73411, the crew of which halted the departure after a surge in the left-hand engine.

Rosaviatsia adds that a further abort event, at Ulan-Ude, took place on 30 January when, after a left-hand engine surge, the crew of RA-73489 stopped the take-off run at 70kt.

In a 14 February bulletin the regulator has instructed regional authorities to alert aircraft crews, and ground-handling organisations providing de-icing services, to the issue.

Rosaviatsia states that special attention should be paid to the possible presence of snow, ice or frost on the engine inlets and fan blades during pre-flight inspection.

De-icing fluid should be used in accordance with the manufacturer’s instructions, and de-icing areas should be cleaned to avoid formation of puddles.

Crews should monitor engine parameters to identify possible trends of degradation in performance, the regulator adds, while operators should consider unscheduled engine flushes.