Originally Posted by
safetypee
fdr, … yes
The stick shaker comment is also very interesting. Such a change in normal operation should have been justified by a discoverable a certification deviation.
An alternative might be a misinterpretation of changes required by retrospective inflight icing requirements; advanced, re-datumed alerting.
Any ATR operators able to confirm the stick shaker operation in these circumstances.
The Roselawn ATR42 bingle certainly added to the knowledge base on icing, and there have been some excellent advances in modelling, particularly north of the border of the US of A. The USA however, in spite of having an excellent National Resource for Icing, (Bond, "not James" Bond) has not moved out of the dark ages. The LEWICE code is no longer supported, by NASA Lewis, and was of marginal benefit. The ANSYS Canada FENSAP-ICE provides excellent solutions for ice accretion, that a number of us that have to deal with SCLD, Runback and just everyday icing issues really would appreciate the FAA updating their calendar to the 20th century. Even the boys from Seattle, last time I spoke with them, would appreciate acceptance of the code validation that has been given for years. Havent looked at this for a couple of years, so hopefully sanity prevailed.
In this event, there is no direct indication of icing being a factor, based on the video evidence, but that is not to say that the plane had encountered icing previously and was carrying a load, that would be very consistent with the event. A spectral analysis of the SPL of the video in the cabin might be interesting, the CVR spectral and the FDR should give very good indication if the wing was clean or not. If it was contaminated, particularly the tail plane, then the flight dynamics would be very close to that in the video. I doubt that is the case, but it can only be excluded by the FDR or the CVR spectral. The crew comments may be pertinent, but historically the crew are the last to be aware of the effects of ice in spite of being first to the accident scene.
JD used to do an excellent presentation on icing, including SCLD, and tail icing. The latter is a niche field that is starting to get lean on expertise remaining in the field, and the history of development is that it can bite. FENSAP-ICE is at least a tool to help teams from getting out of sorts.
refer §25.1419, App C to §25, App O to §25...
