Investigations into repeated slat-jamming problems on Sukhoi Superjet 100s have identified moisture accumulation in actuators as a possible source.
Analysis of a number of slatless landings by the type found that under certain ﬂight load conditions the slats could be skewed during extension.
Sukhoi developed a modification for the slat tracks on in-service airframes and implemented the design change in production from aircraft 95039 onwards.
But the Russian Interstate Aviation Committee says that the problem recurred on three Aeroﬂot Superjets in June, September and October last year.
Examination by Sukhoi and Liebherr Aerospace, the manufacturer of the control system, showed that high atmospheric humidity, characteristic of the time of year, could result in accumulated moisture that froze at cruise altitudes.
This could subsequently affect geared rotary actuators in the slat-control system. The Interstate Aviation Committee says corrective measures have been taken to prevent the moisture problem and ensure slat operability.
It adds that Sukhoi has developed a revised landing procedure which allows a reduced landing speed and short runway requirement under certain configurations.
See the original IAC document [Russian]
See the discussion of the SSJ100 slats problem on superjet.wikidot.com [Russian]
15 Jan 2014 20:35
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