Thanks for the heads-up on the main problems caused by ash inside turbines.
It's still not clear to me what the RELATIVE risks are.
For example:
- anyone know what maxima are specified by engine suppliers for particles in the airflow (ie. number and size - I'd assumed there'd be datasheet items for a number of different combinations of size, characteristics such as melting point, abrasiveness, ..., and number per cubic metre of atmosphere. However, no-one so far (?) has identified such info.)
- Clearly, if there's any risk of significant build-up of melted and recongealed particles downstream from the combusters (on fixed OR moving surfaces), then the decision to fly or not should be risk-based, considering the particles per cube likely to be encountered on the flight, taking account of the different areas of ash that will be encountered, and therefore how much build-up could occur, depending on specific turbine characteristics.
- what about turbine cooling?Although it's not practical to filter ALL the air going through a large bypass turbine, what about the air that goes into the plenums feeding the turbine cooling system? Are there any filters already? Is it feasible to fit any (centrifugal type?)? (Please excuse my lack of turbine internals knowledge.)
If sensible maxima for volcanic ash particle density along routes is specified (anywhere, already?), and turbine cooling issues can be resolved, then what OTHER risks from low densities of ash also exist? (AirCon / pressurisation, instrumentation (pitots, etc.),...?