Stall strips
- Thread starter bLizZuE
- Start date
tgrayson
New Member
There isn't a whole lot to it. They create a sharp leading edge (tiny radius) which causes the airflow to separate at a lower AoA. The purpose is to control where the separation happens so that it doesn't happen first at some undesirable location, such as the wingtip.
tgrayson
New Member
Perhaps this is enough for credibility:
http://cafefoundation.org/v2/pdf_cafe_reports/localflow2.pdf
I noticed that the article references a book that I have, so I'll see if it has more info when I get home.
ProudPilot
Aeronautics Geek
Just point out that it forces a stagnation point higher with a higher AOA. How does this help? Well that means it forces more air below the wing that otherwise would have gone above. This "starves" the upper surface of air making it turbulent (detached airflow, stall) along that portion of the wing. Therefore you can feel a buffet sooner in whatever is aft of it. On a PA28 it's over the flaps. On a PA28R over the ailerons. Depends on the design.
I just say that and hand draw it with some hands on show and tell.
I just say that and hand draw it with some hands on show and tell.
Mike H
Well-Known Member
The stall strip is ahead of the flaps on the PA28R too- definitely not over the ailerons. You can also notice that the inboard portion of the wing has a higher angle of incidence than the outboard portion does.
USMCmech
Well-Known Member
The stall strip makes the stall occur "early" in the area directly behind where it was installed.
In most cases it is better for the root or mid span of the wing to stall before the tips.
nagylyk
Well-Known Member
They are Vortex Generators, not Stall Strips.
AviatorGator
Well-Known Member
That link didn't work for me tgray....says it's "forbidden". :dunno:
tgrayson
New Member
I noticed that, but the link does work; after you get to the "forbidden" page, put the cursor in the address bar and hit enter, and it will load. Maybe the page doesn't like being linked to.
AviatorGator
Well-Known Member
Ah ha....very good. Thanks!
Cessnaflyer
Wooooooooooooooooooooooooooooooo
I also noticed on the F33A Bonanzas that the stall strips are not in the same place on either wing. The left wing is well inboard of the one on the right wing.
http://www.airliners.net/photo/Beech-F33A-Bonanza/0855543/L/
http://www.airliners.net/photo/Beech-F33A-Bonanza/0855543/L/
Crockrocket94
Well-Known Member
Bliz, in the AFM and FSI Books (The Pilot Training Manual for my Excel, VII, Bravo, Ultra and Encore) state they are to create turbulent air as to warn to an impending stall.
Ill get the exact phraseology in a sec.
Ill get the exact phraseology in a sec.
Crockrocket94
Well-Known Member
Ok, here is the reference from the FSI Pilot Training Manual for the Citation XL/XLS Page 15-12 under Stall Warning Systems.
Aerodynamic Stall warning consists of a stall strip on the leading edge of each wing., and stick shaker operated by the angle-of-attack (AOA) system. The stall strips create turbulent airflow at high angles of attack, causing a buffet to warn of approaching stall conditions if the AOA is inoperative.
Hope thats what you're looking for.
Aerodynamic Stall warning consists of a stall strip on the leading edge of each wing., and stick shaker operated by the angle-of-attack (AOA) system. The stall strips create turbulent airflow at high angles of attack, causing a buffet to warn of approaching stall conditions if the AOA is inoperative.
Hope thats what you're looking for.
Crockrocket94
Well-Known Member
I ve HEARD of the root stall purpose as well, but you know, ive never read about it.
NJA_Capt
Well-Known Member
Both of the above arguments are accomplishing the same thing. Stall strips are there to insure control is available to recover from a stall, ie...the root needs to stall first. If a stall strip was added to "create turbulent air/buffet," you can surmise that you needed that buffet because if it were not present you would lose aileron effectiveness. It is the turbulent air at the wing tip that is the problem. By causing this turbulence (air flow separation) at the root first, aileron authority is maintained.
I would say the Dept of the Navy trumps FSI. (Page 56-57)
"The stall strip is usually a small angular strip attached to the root leading-edge of the wing as depicted in figure 52. By using a stall strip the flow is disturbed near the root such that root area stall is induced first. This method is not preferred because it limits rather than improves CLmax It turns out that the use of stall strips is usually a design "after-thought" to improve stall warning cue characteristics found to be unsatisfactory during flight testing."
http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA235994&Location=U2&doc=GetTRDoc.pdf
http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA235994&Location=U2&doc=GetTRDoc.pdf
STALL STRIPS
Leading edge stall strips are small, sharp edged, triangular shaped flow trippers that are attached to the front of the wing leading edge close to its stagnation point. (N). These shed a vortex at high angles of attack so as to both selectively initiate stall at that wing station and to send a buffeting vortex aftward to tremble the tail control surfaces and thus provide a stall warning to the pilot.
NJA_Capt
Well-Known Member
I would imagine it would have something to do with the slipstream of the propeller being on the right side of the plane in high AoAs. The right strip was probably placed farther out to get it in undisturbed air.
tgrayson
New Member
What sort of evidence would they find acceptable? (You may have to ask them.)
Here's some FAA stuff:
Airplane Flying Handbook, Glossary
STALL STRIPS - Aspoiler attached to the inboard leading edge of some wings to cause the center section of the wing to stall before the tips. This assures lateral control throughout the stall.
Pilot's Handbook of Aeronautical Knowledge
In most straight-wing aircraft, the wing is designed to stall the wing root first. The wing root reaches its critical AOA first making the stall progress outward toward the wingtip. By having the wing root stall first, aileron effectiveness is maintained at the wingtips, maintaining controllability of the aircraft. Various design methods are used to achieve the stalling of the wing root first. In one design, the wing is “twisted” to a higher AOA at the wing root. Installing stall strips on the first 20–25 percent of the wing’s leading edge is another method to introduce a stall prematurely.
Aerodynamics for Naval Aviators
addition of leading edge slots or slats toward the tip increase the local clmax and stall angle of attack and are useful in allaying tip stall and loss of aileron effectiveness. Another device for improving the stall pattern would be the forcing of stall in the desired location by decreasing the section clmax; in this vicinity. The use of sharp leading edges or "stall strips" is a powerful device to control the stall pattern.
