barrichello72
21st Mar 2020, 23:41
Hi folks, having a senior moment here about the moveable horizontal stabilizer.
as far as i recall the CofP is located about 25% from the leading edge of the MAC, and behind the CofG, its position is affected by a number of factors such as the payload moving around, fuel being transferred, airplane configuration being changed - high lift devices, landing gear, thurst settings - different speeds - transonic/mach tuck-: anyways the overall location of the CofP behind the CofG causes the airplane to be nose heavy which must be compensated for by the tail down force from the horizontal stabilizer. Now the question is how does exactly that work from an aerodynamic point of view? Moving the horizontal stabilizer to a higher angle of incidence then its leading edge up will result in a decrease in the tail down force due to the fact that the camber of the stabilizer is facing downward, ultimately inducing a pitch down moment as the airplane pivots about its CofG; while on the other hand as the angle of incidence is decreased the taildown force increases inducing a pitch up moment compensating for the natural nose heavy design of the airplane, giving it stability - that would explain the larger excursion or travel of the horizontal stabilizer downward as opposed to up, or maybe i have it the other way around! I am a bit confused... also when on the trim scale the index shows 0, is that actually 4 degrees up due to the rigging of the stabilizer?
many thanks for your willingness and replies.
as far as i recall the CofP is located about 25% from the leading edge of the MAC, and behind the CofG, its position is affected by a number of factors such as the payload moving around, fuel being transferred, airplane configuration being changed - high lift devices, landing gear, thurst settings - different speeds - transonic/mach tuck-: anyways the overall location of the CofP behind the CofG causes the airplane to be nose heavy which must be compensated for by the tail down force from the horizontal stabilizer. Now the question is how does exactly that work from an aerodynamic point of view? Moving the horizontal stabilizer to a higher angle of incidence then its leading edge up will result in a decrease in the tail down force due to the fact that the camber of the stabilizer is facing downward, ultimately inducing a pitch down moment as the airplane pivots about its CofG; while on the other hand as the angle of incidence is decreased the taildown force increases inducing a pitch up moment compensating for the natural nose heavy design of the airplane, giving it stability - that would explain the larger excursion or travel of the horizontal stabilizer downward as opposed to up, or maybe i have it the other way around! I am a bit confused... also when on the trim scale the index shows 0, is that actually 4 degrees up due to the rigging of the stabilizer?
many thanks for your willingness and replies.