WelshZeCorgi Posted June 20, 2022 Posted June 20, 2022 When the nose pitches down when the wings are swept back, due to approaching supersonic flight, is that mainly due to the center of lift being pushed back by the swept wings, or mach tuck, or both?
bones1014 Posted June 20, 2022 Posted June 20, 2022 Not that I've noticed. The Viggen has the worst mach tuck. The F-16 doesn't but that could be due to the fly by wire compensating.
draconus Posted June 20, 2022 Posted June 20, 2022 Yeah, about those glove vanes... Win10 i7-10700KF 32GB RTX4070S Quest 3 T16000M VPC CDT-VMAX TFRP FC3 F-14A/B F-15E CA SC NTTR PG Syria
DD_Fenrir Posted June 20, 2022 Posted June 20, 2022 It’s cog, not Mach tuck. The wings are fully aft a good ways before you hit the number. Glove vanes were there to bring a measure of instability to help maintain the aircrafts pitch rate at supersonic airspeeds.
=475FG= Dawger Posted June 20, 2022 Posted June 20, 2022 1 hour ago, DD_Fenrir said: It’s cog, not Mach tuck. The wings are fully aft a good ways before you hit the number. Glove vanes were there to bring a measure of instability to help maintain the aircrafts pitch rate at supersonic airspeeds. Mach Tuck occurs prior to the aircraft going supersonic and can occur well below Mach 1. Mach tuck happens when local airflow over the airfoil exceeds Mach 1, no matter how fast the aircraft may be going.
WelshZeCorgi Posted June 20, 2022 Author Posted June 20, 2022 I don't think it's center of gravity, if center of gravity was shifting backward with wingsweep, it would go tail heavy and go nose up, wouldn't it?
TLTeo Posted June 20, 2022 Posted June 20, 2022 I would expect the center of lift would also move with wing sweep.
DD_Fenrir Posted June 21, 2022 Posted June 21, 2022 (edited) Yeah it’s the shift of both the CoG and the CoP - even when you manually sweep the wings aft at lower air speeds it gets nose heavy as the wings go aft. It depends on where the CoP is in relation to the CoG; CoG must move aft as the mass of the wings is transferring aft. CoP must also move aft but you get a nett reduction of the total lift generated by the wings (wings forward = more lift, wings aft = less lift). If the CoG is forward of the CoP, wings lifting moment around the CoG must increase to justify the requirement to increase in downward force provided by the horizontal tail is to maintain nose attitude, meaning the centre of Pressure must be travelling a greater amount then the CoG. If the CoG is aft of the CoP, wings lifting moment around the CoG must decrease, meaning the centre of Pressure must be travelling a greater amount then the CoG. Edited June 21, 2022 by DD_Fenrir
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