Follow us behind the scenes of another engine heavy maintenance task, this time on a Williams engine.

As such, our engine team recently completed a carbon seal replacement on the No. 1 bearing of a FJ44-1A – a heavy maintenance task that Prince Aviation is authorized to perform as an authorized Williams International service center.

The first assumption people make is that serious engine work means the hot section. This is the opposite end of the engine.

The No. 1 bearing sits in the cold section, at the very front, where the low-pressure compressor is. To reach it, our technicians removed the spinner, the fan, the stator and the booster stage – opening up the engine layer by layer until the bearing was accessible.

Every bearing sump on a turbofan is oil-lubricated and pressurized, and it is sealed by a carbon seal. Over time that seal wears. When it does, it starts showing oil leakage, and the engine maintenance manual calls for replacement.

Routine in principle, but the access path, the tooling and the reassembly tolerances are anything but.

“It is a two-man job, and it has to be,” says Miroslav Branković, lead engine mechanic at Prince Aviation. “Disassembly and reassembly of that section is done with hydraulic pumps running up to 4,500 psi. There is no improvising with that kind of pressure.”

The work takes roughly two days: day one for removal and inspection, day two for reassembly – followed by an engine run-up and a high power check before the aircraft goes back to its owner.

The clearest measure of how rare this task is comes down to the tooling. Williams International does not distribute it.

The manufacturer keeps the tool sets in-house, tracks them by part number, and ships a dedicated AOG kit to the approved facility handling the job – wherever in Europe that engine happens to be.

The tools arrive for that specific task, and only that task. That is how specialized, and how infrequent, this work is.

It also means the OEM knows where every engine in the fleet is. When a seal fails, the call comes to one of few addresses in Europe.

We are proud that one of them is Prince Aviation – and prouder still of the people who have earned and kept that approval.

See the video of the process on our YouTube channel!