AIRBORNE OBSERVATIONS OF ICE ACCRETION　AND AIRCRAFT PERFORMANCE IN ARTIFICIAL AND　NATURAL SUPERCOOLED ICE CLOUDS ON　DORNIER 228- AND 328 AIRCRAFT

摘要

Results from two airborne experimentsrninvestigating aircraft icing, aircraftrnperformance and cloud microphysicsrnassociated with supercooled large dropsrn(SLD) are presented. Dornier-Luftfahrtrnperformed in-flight tests, where externalrnsurfaces of a DO-328 turboprop aircraftrnwere exposed to artificially generated SLDrnwith 180 μm mean volume diameter (MVD).rnHigh liquid water content (LWC) up to 0.65rng m-3 caused substantial ice accretionrnbehind boot-protected regions of the wings.rnVisual cues associated with SLD arerndescribed. Limitations for flights in severernicing conditions and exiting proceduresrnhave been derived.rnDLR performed several research flightsrnwithin natural icing conditions on a Do-228rnaircraft equipped with cloud microphysicalandrnicing documentation instrumentation.rnSpecified weather-forecasts helped to findrnatmospheric regions that wererncharacterized by at least moderate icingrnconditions and temporarily by thernoccurrence of SLD. Two cases with severernicing and ice accretion rates exceeding 3rnmm min-1, temporarily associated with SLD,rnhave been met. SLD did not dominate, butrnsignificantly contributed to LWC duringrnicing incidents. Back-running ice has beenrnobserved in the presence of SLDs. Heavyrnicing was experienced in stratiform cloudsrnwith embedded convection, average LWCrnbelow 0.3 g m-3 and within a -10 to -7 oCrntemperature interval.