-13-
In summary, the Board belleves that CAL 290 accumulated lee durlng 1ts descent to Kansas Clty. The alrf01l antl—lclng system was not turned on and the crew was unaware of the 1c1ng accumulat1on because the wlndshleld ant1—1c1ng system was used contlnuously. In thls 1nstance the alrcraft dld not reach the angle of attack crit- 1cal for the horn type 1ce formatlon belng carrled on the horlzontal stablllzer leadlng edge, untll 1t passed over the south end of the runway and the alrSpeed 1n- creased to approximately 138 knots. At thls pelnt a combinatlon of alrspeed and flap peeltlon resulted 1n an angle of attack at whlch the tallplane down loadlng was lost and the aircraft pitched over. Although the ev1dence 1ndlcates the pllot was attempting recovery when the alrcraft struck the blast mound, the pltch over started 1n an altitude too low to render such actlon effectlve.
Probable Cause
The Board determlnes that the probable cause of this acoldent was an undetected accretlon of ice on the horlzontal stablllzer whlch, 1n conJunctlon wlth a SpBlelC airspeed and configuratlon, caused a loss of pltch control.
Correctlve Actlon Taken
As a result of thls acoldent the Federal AV1at10n Agency has taken the followlng correctlve actlons.
1. Issued an alert bulletln to all domestlc Vlscount operators and FAA reglonal offlces adv1sang that both alrframe ant1-1c1ng heat exchangers should be turned on whenever the 1nd1cated out51de alr temperature 13 10°C or below, 1f there 15 any p0551b111ty of encounterlng alrframe 101mg.
2. Proposed amendlng all Vlscount alrplane fllght manuals as follows'
a. Requirement to use both heat exchangers whenever OAT ls 10°C or below.
b. A recommendatlon to carry hlgher power on 1nboard englnes durlng descent to 1ncrease hot alr mass flow to wlng and tall surfaces. (Airframe antl— 1Clng heat exchanger on the 1nboard engine)
Addltlonal correctlve actlon taken by the manufacturer 1ncluded a fllght manual change that required both heat exchangers to be on at all tlmes when the 1nd1cated outS1de alr temperature 13 { 10°C or below unless 1t 18 certaln that no icing condi— tlons Wlll be encountered.
