A Question About Slats
- Thread starter stewartb
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B
Barnstormer
Vx 50mph
Vy 70mph
MacKey slats "pivot" open/closed. The amount they pivot varies with the wing's angle of attack. So yes, they are open during Vy, but not fully.
You can see the slats partially open just from the wind on the ground.
Attachments
Thanks for that. Another question. Aside from STOL advantages.....
Do you slat guys think slats always improve the airplane's overall utility or are there conditions where you wished you didn't have slats? Crosswinds? I assume landings are less a nuisance but what about launching into a stiff crosswind? The majority of slat discussion comes with pictures of the tailwheel 2' below the mains on short final. That isn't important to me. I'd like to hear opinions about slats from guys who use their planes year round for transportation rather than blue sky hobby flying. Utility pros and cons are what I'm interested in.
Do you slat guys think slats always improve the airplane's overall utility or are there conditions where you wished you didn't have slats? Crosswinds? I assume landings are less a nuisance but what about launching into a stiff crosswind? The majority of slat discussion comes with pictures of the tailwheel 2' below the mains on short final. That isn't important to me. I'd like to hear opinions about slats from guys who use their planes year round for transportation rather than blue sky hobby flying. Utility pros and cons are what I'm interested in.
B
Barnstormer
In the year and a half I've had the SQ2 I've put 350 hours on her, nearly all of it off-airport in all kinds of weight configurations from full fuel two persons and gear, to just me and light on fuel. In that same time period I've put a couple hundred hours on the 185. If I could put slats on the 185 I would, although they would be of a design I could lock down from within the cockpit for cruise.
Cruise is the only flight envelope that Mackey slats don't improve, in fact they slow the aircraft. Some guys drill holes in the slats/brackets so they can "pin" the slats closed for long cross country flights. I'm considering that for my trip back to Alaska in May. Bruce at Backcountry Super Cubs is working on a manually deployable slat system with a lever similar to a flap handle. The prototype I saw had two positions, closed and fully open. It will obviously weigh more then the Mackey slats.
More important to me then the STOL improvement with Mackey slats, is the safety improvement. I can rudder turn as much as I want, as slow as she'll fly, without risk of stalling a wing or spinning in. When I'm close to the ground, say following a river, where I don't have the height to safely bank in turns I just step on the rudder as much as I need to make the turn while keeping the wings level.
Or if I'm higher and I've got side canyons coming in on a turn with high winds that could flip me over on my back again I just step on the rudder, keeping the wing down so I don't get flipped.
There is no portion of a flight where I feel the slats working or not working, meaning what they do and when they do it is imperceptible to the pilot. As far as takeoffs or landings with gusty winds, crosswinds, or gusty crosswinds, what the slats will or won't do for that aspect of the flight is not a consideration for me. What is a consideration, and the major one, is how much wing underside I'm willing to expose.
Because my SQ2 stall speed is 26mph if I've got a crosswind landing and have the runway width then of course I going to land as much as I can into the wind. If the runway is narrow then I'm landing just like I would in the 185, wing down on one wheel, tail as high as needed to keep from being gusted back into the air.
Mackey slats keep the wind on the wing (so to speak), which does allow crazy high angle of attack landings and takeoffs, but the plane can takeoff and land with the same profile as a Super Cub as well. It's up to the pilot and of course more importantly up to the specific situation. But even here the slats provide a huge margin of safety cause if suddenly you were inadvertently gusted up or the wind dropped out from under you and you pulled back on the stick to try and catch the plane before it dropped in, the slats open and keep what wind you have over the wing.
Cruise is the only flight envelope that Mackey slats don't improve, in fact they slow the aircraft. Some guys drill holes in the slats/brackets so they can "pin" the slats closed for long cross country flights. I'm considering that for my trip back to Alaska in May. Bruce at Backcountry Super Cubs is working on a manually deployable slat system with a lever similar to a flap handle. The prototype I saw had two positions, closed and fully open. It will obviously weigh more then the Mackey slats.
More important to me then the STOL improvement with Mackey slats, is the safety improvement. I can rudder turn as much as I want, as slow as she'll fly, without risk of stalling a wing or spinning in. When I'm close to the ground, say following a river, where I don't have the height to safely bank in turns I just step on the rudder as much as I need to make the turn while keeping the wings level.
Or if I'm higher and I've got side canyons coming in on a turn with high winds that could flip me over on my back again I just step on the rudder, keeping the wing down so I don't get flipped.
There is no portion of a flight where I feel the slats working or not working, meaning what they do and when they do it is imperceptible to the pilot. As far as takeoffs or landings with gusty winds, crosswinds, or gusty crosswinds, what the slats will or won't do for that aspect of the flight is not a consideration for me. What is a consideration, and the major one, is how much wing underside I'm willing to expose.
Because my SQ2 stall speed is 26mph if I've got a crosswind landing and have the runway width then of course I going to land as much as I can into the wind. If the runway is narrow then I'm landing just like I would in the 185, wing down on one wheel, tail as high as needed to keep from being gusted back into the air.
Mackey slats keep the wind on the wing (so to speak), which does allow crazy high angle of attack landings and takeoffs, but the plane can takeoff and land with the same profile as a Super Cub as well. It's up to the pilot and of course more importantly up to the specific situation. But even here the slats provide a huge margin of safety cause if suddenly you were inadvertently gusted up or the wind dropped out from under you and you pulled back on the stick to try and catch the plane before it dropped in, the slats open and keep what wind you have over the wing.
B
Barnstormer
Oh, takeoffs into a crosswind or gusting crosswind is less of an event then a wing without slats, again because if the wind all of a sudden lessens the slats do there job keeping what wind there is on the wing.
L18C-95
FRIEND
Oxford UK
The fully castoring tailwheel Helio Courier had spoilers, and a pilot who flies it has mentioned that the cross wind technique is to land in the crab to avoid asymmetric slat deployment. Understanding how the slats work in a cross wind for Super Cubs and the Courier, and why they need a special technique, if they do, would be great - hopefully someone familiar with the Courier comes along on this thread.
Southern Aero
SPONSOR
kcco/1ga2
Actually the Helio tailwheel IS a steerable tailwheel. It has the bellcrank or steering arms above the oleo in the fuselage. Only reason for landing in a "crab" would be it had crosswind gear. ...... flew that a couple of times, is strange to taxi sideways! With out it normal crosswind techniques are used .... just slower. Slats are automatic and aerodynamically controlled. There are no springs or deploying devices. There is nothing violent about them, smooth and seamless. If you land a Helio and a slat is not out, you didn't land it you flew it into the ground or runway. A lot of pilots try to fly the Helio like they would a C180 and don't take advantage of the full potential of its capabilities. Slats out means high lift which means high drag....... has to be flown accordingly. If you could lock the slats in, it would probably fly a lot like the C180/185. There are spoilers, or interrupters, that work continuously but progressively with the ailerons. They are only used for roll control and help with adverse yaw, cannot be deployed together for rapid descents as some think. If you remember on the side of the Helio you see C/STOL . the C is for Control. With power the Helio would not stall and you had roll control at near zero airspeed.
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Superchub
Registered User
Brighton, CO
How about do they effect climb. I have head you loose some climb from the drag?
cruise speed loss? ##'s 5%, 5 MPH @ 100?
I have a new set for the Chub and have been pondering putting them on. I was going to sell them, but now I may consider giving them a try.
Brandon
cruise speed loss? ##'s 5%, 5 MPH @ 100?
I have a new set for the Chub and have been pondering putting them on. I was going to sell them, but now I may consider giving them a try.
Brandon
ER Upgrade
Registered User
Eagle River
You might ask the Argentine guy about his restored cub, LV-GBR. He may provide the Randy side of your question. Maybe/maybe not on a comparison tho.
bob turner
Registered User
What about a comparison with the Dakota slots?
I am not a Helio expert, or even a high time Helio guy, but I always approached with the slats out. They go "boom" and the first time is a surprise. Our biggest problem was the 295 flew like a truck, and the tailwheel shimmied. Good riddance. They do land short - like a J-3.
I am not a Helio expert, or even a high time Helio guy, but I always approached with the slats out. They go "boom" and the first time is a surprise. Our biggest problem was the 295 flew like a truck, and the tailwheel shimmied. Good riddance. They do land short - like a J-3.
L18C-95
FRIEND
Oxford UK
On the OP question wouldn't slats, which are designed to increase Clmax, ideally only extend at around Vx? The wing is pretty/most efficient at Vy with around 4 degrees AofA, so slats would be expected to be retracted?
Because of the jump in Clmax, presumably Va is lower for a SC with slats?
The Stinson has slots which aid low speed good behaviour.
Because of the jump in Clmax, presumably Va is lower for a SC with slats?
The Stinson has slots which aid low speed good behaviour.
B
Barnstormer
Full disclosure: the only slatted wing plane I've flown to date is my SQ2. The only Dakota slotted wing plane that's flown with me at the same time under the same wx/wind conditions was Grizzly Cub at this year's Texas STOL Roundup. Grizzly Cub sports an IO-409, my SQ2 has an O-375 (25hp less). I have no idea what Grizzly Cub's empty weight is.
Having said that, Grizzly Cub was flown by two excellent STOL drivers, and its takeoff and landing distances were 3 to 4 airplane lengths longer then my SQ2 with me at the controls (even more with Goza flying my SQ2), both in the Traditional STOL™ and Obstacle STOL™ competition.
If you are not a religious man a Vx climb in a SQ2 will help you become one!
And if you really want an adrenaline rush climb steeper. You'll learn what the fuel boost pump is for and what the red area is in a Dynon Skyview AHRS. And it will do that with two people aboard and 24 gallons of fuel (perhaps more). Scary as hell and more fun then you can imagine.
Can't speak for any other slatted plane, just the SQ2.
Damn I want to go flying!
Southern Aero
SPONSOR
kcco/1ga2
Bob
They might go "boom" if in turbulence at low speed or not operating smoothly on the bearing rollers. ............. abrupt maneuvering can cause that too......... It kinda WAS a truck.... at over twice the the gross weight of a SC it could just about haul anything you could get in it or on it. Tailwheel shimmy was caused like any other ....... damage or lack of maintenance, oleo, pivot angle of the caster. It was an airplane with a little different mission.
As far as comparing to the slots.......... no real comparison, different designs. Dakota capitalized on the Piper L14 design from 1945, I think it was......... only a few were built, only a couple exist. And my hat is off to them for that! They made it possible for a lot of pilots to have a lot of fun, But the L14 lost out militarily to the L19. The L14 wing was designed to get the airplane out of ground fire climbing as quick as possible after take off. It was a modified J5 which is pretty much already "STOL" with the USA35B section. With the slots. the air would stay attached at about 45 degrees AOA. Slots are usually placed in front of the ailerons to ensure roll control at or near stall speeds. To land an airplane at near 45 degrees AOA may work best on a tri geared airplane......... you need to be on your toes in a tailwheel. A true "slatted" wing can more than double the lift coefficient without the high AOA.
Cubus Maximus
Registered User
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B
Barnstormer
Yes, right behind the slats. And on the vertical and horizontals.
68Papa
FRIEND
Chugiak, Alaska
I don't have VG's - I got talked out of them by folks that have much more knowledge of these things than me. In a nutshell, there argument was, "with slats, what's the point"? They could be wrong, but who am I to argue with someone with 50 years experience? I would certainly be interested in Wayne Mackeys thoughts.
