Sul numero 20-26 February 2018 della rivista Flight International David Kaminski-Morrow pubblica.
Unheated sensors led to An-148 crash
Data from Saratov Airlines flight that came down near Moscow suggests there was problem with pitot-static equipment.
Preliminary analysis of flight-data recordings from the Saratov Airlines Antonov An-148 that crashed shortly after taking off from Moscow Domodedovo airport on 11 February indicate that the heating system for the jet's pitot-static pressure sensors was not operating at any point.
Data from 16 flights has been downloaded from the recorder, and the Interstate Aviation Committee says that the heating system had been switched on before take-off for all 15 flights prior to the ill-fated service to Orsk.
Investigators state the aircraft took off at 14:21 local time.
At a height of 130-150m (430-490ft) the autopilot was engaged, and the flaps were retracted at 550m.
Some 2min 30s into the flight - as the aircraft reached 1,300m - differences in the airspeed readings, between the captain's air data system and that of the back-up system, began to appear at about 250kt (460km/h).
…
After about 25s the captain's system was reading some 16kt higher than the back-up, and the crew received a comparison alert lasting 10s.
As the aircraft reached 2,000m there was another comparison alert - but in this instance the back-up system showed the higher speed, which was increasing, while the captain's was declining.
In response, the crew disengaged the autopilot and flew the jet manually.
…the captain's speed reading continued to deteriorate until it reached zero, 34s after the autopilot was switched off, while the reading from the back-up showed 290-300kt.
For some 50s after the autopilot was disengaged the aircraft flew at heights varying from 1,700-1,900m and experienced changes in vertical loading. The captain's speed reading remained at zero while that of the back-up system started to fall sharply, and the aircraft began to pitch by some 30-35° nose-down.
As the An-148 dived its back-up speed reading increased rapidly, reaching some 430kt, before the aircraft struck the ground just after 14:27, having been airborne for only around 6min. The aircraft was 30° nose-down at impact and, in the final seconds of flight, had entered a 25° right bank. The speed reading on the captain's system had remained at zero.
The inquiry … points to incorrect data on the crew's airspeed indicators, apparently the result of pitot-static sensor icing.
https://finreader.flightglobal.com/p...3/article.html
EI-PAUL
Per intenderci, anche quello dell'AN-148 di cui stiamo discutendo potrebbe essere considerato a tutti gli effetti un assetto inusuale, pur essendo in tutto e per tutto ancora all'interno dell'inviluppo di volo per quel che concerne assetto / spinta / velocità reale.
Se questo:
non è l’esito di un assetto inusuale?
Sciavo
Romano