On Learjets we use boundary layer energizers on the wings, but not for help at low speeds. It’s to give aileron authority at greater than .77 mach. Otherwise the airflow would separate, creating a boundary layer envelope on the top side of the aileron, and the controls would feel really numb. If we are missing even just 1, our max speed is limited from .81 to .77
I did accurate testing before and after I put vortex generators on blue suede shoes. I documented this, tests were done at similar weights temperatures and humidity. I found anywhere from a seven to a 10% decrease install speed. That was What could be proven, What couldn't be proven but definitely holds true is the control ability at lower speeds. Eeler on effectiveness increased along with elevator effectiveness. It made the aircraft significantly shorter on both takeoff and landing.
Good stuff. I plan to get VGs at some point, but I want to get my Sundowner painted first, and that is going to be a while. Getting some avionics upgrades at the moment, so I'll have to build my funds back up for the paint.
The VG creates a situation where the boundary layer does not separate from the surface of the wing, there is no TRICKING the wing involved, she has no idea how they work. The position is critical, they only perform their function at low speeds when they are still exposed to the airflow, in the case of high AOA they must be able to SEE the incoming air, thus ,they must not be mounted too far back from the leading edge, 5 to7% of the chord is typically correct. They do induce drag at all speeds so there is a tradeoff on having them and not having them.
Well, in aerodynamics nothing comes for “free”. What are the disbenefits of installing them? You emphasize the slow speed benefits, which are important to your operations. But where is the aerodynamic cost? Is it extra drag and fuel consumption at high speeds? Not trying to be argumentative just trying to grasp the whole “cost vs. benefit” picture of the modification. Seems that I’d there was absolutely no disbenefit or cost then the manufacturer would put them on all planes at the factory. Thanks for yet another educational and interesting video!
They are a rather new development as aerodynamics with the help of CAD has been advanced in the recent decades. I would think as a layman it depends on when (on which AoA) they start to generate the vortexes and if that correlates with increased drag on normal operations. On fighter-jets such devices and design are use to improve maneuverability by not having stream separation on high AoA and a delta wing produces its on vortex on high AoA.
I can't speak for any other aircraft type, but those I know that have them installed on their Cessna 150s report a 3-4 knot increase (true airspeed) in cruise. On a 150 specifically, every knot counts as a pro, but the con of installing them is the additional weight. While marginal, pounds are also expensive on a 150, so every one counts.
I have a bit of a negative attitude, when it comes to Vortex generators. My question is why are they sitting out there on the wing. I have studied tailplane design and there are quite a lot of good reason to have them down that end of the aircraft. Even ducks and fowls come equipped. The good Lord wasn't an amateur designer!!! retired CPL.
A must if you're doing short field landings/takeoffs or STOL competitions. Noticed the difference the first flight after installing them on my 172. Lowered my stall speed and more authority on approaches. Skip a couple of steak dinners with the wife & get them installed on your plane! Shhhhh don't tell my wife.
