Re:Boeing CEO Dennis Muilenburg Addresses the Ethiopian Airl...
by salawat on Saturday April 06, 2019 @10:15PM
(#19594369)
Okay. So after a bit of chewing on the screw jack equations, I settled on using an M24 screw as the basis just for convenience. Eyeballed a video of jackscrew of a 737NG, and figured a 6 inch lever arm. In the form of a pulley of some sort as the input for the screw jack from the trim wheel in the cockpit.
Dropping in the previously calculated wind load of 1015087 N, we end up with an effort force of 3182 N, which through a 6 in pulley would be 485Nm (357 ft-lbs) of torque,
Note, we're in automobile engine levels of torque output to actuate this screw jack against the wind load on the horizontal stabilizer.
Give me a bit to come up with some estimates on the trim wheel and play around with some gear trains to see if I can come up with an arrangement that does the trick.
It should be doable, but with the gear ratios I'm thinking will be required to generate the requisite torque, the actual rate of actuation is going to be pretty slow.
737-800 has a 32.776m^2 horizontal stabilizer area. Let's double that to 65.556 to accomodate both airfoils.
Wing load is 1/2p(v^2)A Where A=65.556m^2 (352.8 ft^2) v=180.556m/s (350 knots) And we'll guess our air density around .95ish kg/m^3 given our altitude of 2334m (7625 ft plus change) asl
Barring any flawed fundamental assumptions, that gives us a wind load of 1015087 N (228200.636 pounds-force (lbf)), and a dynamic pressure of 15485 N/m^2
I'll leave this out there to offend any actual aerospace engineers that might be reading so they'll tell us I'm doing it all wrong while I try to work out whether I can use the screw jack equations and what we've calculated thusfar in the hopes of figuring out something that even remotely makes sense.
I have a feeling I'm oversimplifying or misapplying the wind load equation. But hey, it's the internet. I'm allowed to be wrong.