Originally Posted by
Vendee
The stator stages on a gas turbine hot section always look completely knackered on strip down. The RB199 was no exception. The M07 HPNGV module would be full of cracks and burning but it wasn't rotating and could handle the damage. I remember visiting Ruston Gas Turbines in Lincoln in the early 80's. The made industrial gas turbines that would run continuously for 12 years without shutting down, and on poor quality fuel too. The turbine blades eroded to something resembling thick needles when they were finally stripped down.
The HPNGV's as you say suffered from burning and cracking as they sat at the exit of the combustor and saw gas temperatures of over 1600k.
Because of the high spares cost, a wide gap braze repair that had been developed for civil engines was embodied on the RB199.
The problem was that the HPNGV's structurally support their inner components.
And widescale braze repair resulted in loss of structural support and eventually led to a catastrophic failure.
This was resolved by a modified HPNGV in a material that was more temperature tolerant.