Oddments:
- It's known that in the last decade or so, there have been 100ish incidents of engine rollback in conditions which are consistent with high IWC (iced water content).
- High IWC is different to icing conditions.
- Experience says that high IWC is not readily visible from a cockpit, and that the instrumentation to detect it is only fitted to a handful of specialist research aeroplanes around the world.
- NASA is currently pursuing a research programme into this. It's in several parts but will include flying one or more research aeroplanes to look into what conditions exist where. An out of date news article
here suggests use of a modified S3 Viking, although I have a little inside knowledge which suggests that it'll now be something else - as yet undecided.
- NASA is working with FAA and the Australian Bureau of Meteorology of the programme. This is because they want to look at flying in the vicinity of Darwin where they've got a good combination of ground facilities and weather.
- The concern is about core and compressor stator icing due to partial melting then congealing of iced water crystals. The mechanism isn't well understood but it's believed that where it occurs it takes some time (15 minutes has been quoted to me) to start to get an appreciable power loss. So, you'd have to stay in those conditions for some time.
- They aren't worried about airframe or intake icing - those are well understood, and all airliners have adequate information about their avoidance and treatment. This is something quite new.
G