With reference to this article:
Quiet revolution-25/04/2000-Flight International
Could the reason for the addition of the lower fuselage ventral strakes have been a factor? The ref. article explains the reason the strakes were added:
"During the Q400's development testing the six bladed propeller slipstream was found, during side-slips at V2, to wrap round the fuselage and impinge on the opposite side of the fin and rudder. This tendency was cured by fitting the two long ventral strakes under the fuselage's rear half."
The same article also describes maximum rudder deflection is restricted to 12 degrees with flaps up, but with flaps 5 or greater it increases to 18 degrees.
The side-slip at V2 most likely relates to single engine operation when reading the article but would the ventral fins have any effectiveness with the engines/propellers at high power settings with the aircraft at low speed and a pitch of 31 degrees? The accident aircraft had 10 degrees of flap which would result in 18 degrees of maximum rudder deflection. Any flow wrapping around the opposite side of the rudder may have resulted in the aircraft to yaw in the opposite direction than anticipated by the crew?
One more question related to this article: "All Q400 take-offs have to be brakes-off, rolling start." No explanation is given as to why, do any Q400 drivers know why this is the case?
Thanks,
Green-dot