Originally Posted by
Teddy Robinson
"Several posts states - NTSB is cited as the source - that the crew of CO3407 flew ONLY 134 knots when selecting gear and initial flaps."
What I was trying to get at a few pages back with a question re the static ports .. their position and ice protection was this
A static blockage at altitude will lead to an IAS higher than the TAS .. because the environmental dynamic & static pressure is being measured against a (lower) static pressure that existed at a higher level, that at which the blockage occurred.
On my type we have 3 static sources for the ADC, which are well protected and a comparator warning to back it up, BUT failure of any of the ice protection systems will only generate an amber caution.
So, whats the score with the Dash 8 ?
TR
The problem with the scenario of false IAS indication is this:
Any fault in (say) deicing of the statics or pitots which leads to the ADCs overreading and the crew not realising how slow they are will
also cause the FDR to record the same erroneously high speeds. It's a pound to a penny that the speeds the NTSB is quoting based on the FDR are from the same source(s) as the crew relied on.
I believe the static system on the dash is pretty well protected - and if it were in fact in error it would have been obvious to the NTSB because all the altitude data they've been releasing - 1800ft to 1000ft in 5 secs, etc., would have also been compromised by the static error. So if there were a static source problem I'm sure (1) they'd know and (2) they'd have already said something to that effect. Nothing released to date indicates a static source, or airspeed system of any kind, error.