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Thread: Slip Speeds

  1. #1
    Senior Member JoeRuscito's Avatar
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    Default Slip Speeds

    Ive been working on getting my approaches steeper. As others have said it seems the best way to do this is by slipping. Otherwise with full flaps and at 50-55 mph over the trees (obstacle) my glide is pretty shallow. I want to make sure Im going about this safely so I want to know what others are using for a min slipping speed and/or slowest approach speeds. For reference My stall speed indicated is 44 mph with half flaps and 39 with full flaps. Ive practiced full rudder deflection slips at altitude in both directions and I can fly at or well below my normal indicated stall speed in both flap configurations and remain in control (granted indicate is probably unreliable in these attitudes). Even when the stall breaks (fully cross controlled) Im yet to have a wing drop in either direction. Lots of weird buffeting though. I even tried entering and recovering quickly from the slip to make sure I did not induce a sudden wing drop by swinging the wings fwd/aft.

    Id love to hear that everyone else is doing. And if you could call out your stall speeds when referencing your own approach speeds so I can understand the typical % above stall in your aircraft. Thanks!

  2. #2
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    Default Re: Slip Speeds

    Joe do you have vgs? I recommend VGs. You can lower you approach speed 5mph right off with them. That’s about 25’ shortened landing distance.
    Dustin Dickerson

    Building 7ss STI x 2
    Oratex
    29" shock monster
    EP912STI 155hp
    Garmin
    N33TF......FLYING!
    N53TF......FLYING!

  3. #3
    Senior Member JoeRuscito's Avatar
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    Default Re: Slip Speeds

    I don't have vgs yet but I will likely put them on at some point. I've been reading all of those posts. However I can land pretty short when there are no obstacles. <400 ft pretty consistent, but when there are trees, sometimes 100 ft trees, Im 1/3 down the runway before Im near the ground.

  4. #4
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    Default Re: Slip Speeds

    Are you using full flaps? I know some don’t land with full flaps because they don’t like how it feels at full flaps. The difference between us is my plane is pretty draggy so I can come in very steep at idle power because of all the drag.
    Dustin Dickerson

    Building 7ss STI x 2
    Oratex
    29" shock monster
    EP912STI 155hp
    Garmin
    N33TF......FLYING!
    N53TF......FLYING!

  5. #5
    Senior Member JoeRuscito's Avatar
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    Default Re: Slip Speeds

    Yes I'm using full flaps. At 45-50 its starts to steepen with full flaps but I'm getting awful close to stall, it makes me somewhat nervous to be doing that still a couple hundred feet up but maybe that's what I need to get comfortable with. My plane, at least with the standard wing, just seems to want to keep flying!

  6. #6
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    Default Re: Slip Speeds

    You have AOA on the G3x correct? I find it to be very helpful and the best tool. I am focusing more on the AOA and not the speed. Being nervous at the slow speeds is what you should be. Coming in steep, your speeds can be less because your AOA is less but you will run out of airspeed quicker on the flare. I think this is where most blip the throttle to help you arrest the decent??? I am no means an expert and trying to get the landings short also. Coming in over an obstacle adds significant landing distance. I have a field by my house that is 600' long. (641' according to google) I have a adjacent field to that, that I can use for an approach. There is a 4' fence separating the two. I can consistently land sub 300' but I am nervous about landing in that field. So for safety I am calling my landing distance 300' for no obstacle. Best I have done so far is 200' hard braking. First unknown is its grass so I will have reduced braking. (Don't want to land with it wet or frozen) Second, I have to clear the 4' fence on the one end. I figure I will be 10' agl coming in over the fence for safety. If I do the math on that, 3 degree standard approach and cross the fence at 10' that ups my landing distance 190'. If I cross the fence at 10' and fly a steeper approach at lets say 5 degrees my landing distance goes up 100'. I don't know what factor landing on grass will have compared to the landing distances I am getting on dirt, but I am getting close to 600' now.

    So doing the math on yours.......crossing obstacle at 100' and 3degree approach angle you are adding 1908' to your landing distance.(I guess high-school math is useful?) If you go twice as steep and come in at 6 degrees 100' over the trees you landing distance increase is 951'. So even coming in steep crossing a obstacle adds significant distance.

    I feel like when I slip I need to double my approach angle to keep the same AOA. (This is power at idle. I like landing with power at idle so anytime if I lose an engine I will make the landing. Maybe this is not the best way to land short though? May need to be under power to get the slower stall speed??) I find if I get setup on the AOA I want, then slip, I must push forward fairly hard about doubling my approach angle, then when coming out of the slip I will have the energy needed to flare.
    Last edited by Shadowrider; 02-05-2020 at 09:32 AM.
    Dustin Dickerson

    Building 7ss STI x 2
    Oratex
    29" shock monster
    EP912STI 155hp
    Garmin
    N33TF......FLYING!
    N53TF......FLYING!

  7. #7
    Senior Member JoeRuscito's Avatar
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    Default Re: Slip Speeds

    Dustin I really appreciate you thinking on this and the time your taking to explain your methods.

    I do have AOA and I certainly use it in all cases to make sure I still have lift available, although I imagine like airspeed it is less reliable in a slip when the wing shadowed by the fuselage no?

    I have noticed when I slip, if I keep my airspeed consistent to a normal approach (50-55) which seems to be a similar sight picture angle, When I remove the slip at around 10ft I find I seem to have even more energy causing my float to extend. Im also at idle.

    Its interesting to fly with my friends (in a pacer and a clipper) and watch them come over obstacles, they drop like rocks! Almost vertical. The kitfox glide puts me at least a couple hundred feet past their touchdown (without a slip). Hence why I want to get better at slips.

  8. #8
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    Default Re: Slip Speeds

    No worries as I am trying to figure it out also. Yeah I think AOA has errors when slipping. Maybe others with chime in, but sounds like you just need to reduce speed when in the slip. Maybe focus on what your speed (AOA) before and after the slips? Maybe you need to slip harder? I have just been trying to baby step slowly reducing speeds. Our aircraft drag is much different so others running grove gear and 7ss wing will probably be the most helpful. I feel like I drop like a rock if I want.
    Dustin Dickerson

    Building 7ss STI x 2
    Oratex
    29" shock monster
    EP912STI 155hp
    Garmin
    N33TF......FLYING!
    N53TF......FLYING!

  9. #9

    Join Date
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    Default Re: Slip Speeds

    How about trying to get Trent Palmer or Bryan (Project kitfox) to chime in since they have quite a bit of experience in bush landings.
    Interesting talking about slips here and I go to twitter and this appears.
    https://airfactsjournal.com/2020/02/...-is-essential/
    Last edited by Hawkertech; 02-05-2020 at 01:56 PM.

  10. #10
    Senior Member Dave S's Avatar
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    Default Re: Slip Speeds

    Hi Joe,

    A couple thoughts.

    1) I use 1.3 times the no flap indicated stall speed as well as 1.3 times the full flap stall speed for approach in each of those configurations and 5 mph less @ crossing the threshold. If I use a slip, I hold the pitch established at the stabilized approach speed and DO NOT refer to the ASI when applying the slip. If I am doing an obstacle clearance, I establish my 1.3 less 5 MPH, then apply the slip - so I already have my minus 5 when going over the obstacle.

    2) Personally, I feel that if a person goes out and does spins in a spin certificated aircraft with an instructor, they will know all the reasons why doing an approach at one MPH above the stall might not be the best idea.

    3) You may have considered this; but, it might pay to look at all the whats about controlling altitude and glide slope at low speeds. Each aircraft prop/engine combo will be different; however, a person could determine what their zero thrust RPM is at approach speeds. Some props, particularly if they are are set on the coarse side, might be still be providing thrust at the RPM used for approach. If the prop is creating thrust during approach, the slope will be more shallow; and, if the prop is not providing thrust or better yet if it is providing drag at the approach speed your glide will be steeper. Drag increases the descent slope and comes from flaps, the side of the airplane in a slip and also the prop if the RPM is low enough and prop pitch is fine enough.

    While I can't afford one, I'd love to have an adjustable prop that could be put in a fine pitch on approach as that essentially makes drag somewhat like the flat side of a plywood disk on your nose. More than a few kitfoxers have set the ldle of their 912 low enough on the ground (1400 or so) so it will stay at 1800 on approach rather than creeping higher than necessary.
    Dave S
    Kitfox 7 Trigear (Flying since 2009)
    912ULS Warp Drive

    St Paul, MN

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