Slip Speeds

[JoeRuscito]

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!

[Shadowrider]

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.

[JoeRuscito]

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.

[Shadowrider]

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.

[JoeRuscito]

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. :confused: My plane, at least with the standard wing, just seems to want to keep flying!

[Shadowrider]

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.

[JoeRuscito]

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.

[Shadowrider]

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.

[Hawkertech]

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/no-stall-no-spin-why-angle-of-attack-is-essential/

[Dave S]

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.

[JoeRuscito]

Thanks for that Dave. It's helpful to understand the margin you are using above stall. If I understand correctly when you are over the numbers you are hovering about 5-8 mph above your stall. As I currently come over the numbers Im carrying about 10-12 mph above stall and likely why Im not sinking and floating. Agreed I don't want to get anywhere near 1 mph above with any height under me, and really thats why I started the post to gauge where everyone is at compared to my practice.

[Dave S]

Joe,

In my response, I intentionally used 1.3 times Vs/Vso & minus 5 rather than my ASI indications because each of our airplanes is likely to have airspeed indicators that read a little different - and V speeds change with loading also.

Actually it works out to 10 MPH above stall in my case over the numbers; and, the procedures I indicated are out the window if conditions are windy/turbulent at all - I consider this is only for short field/obstacle precision work under ideal wind conditions.

In my early flights with our kitfox, I stayed with Vs/Vso + 5mph for final down to 10 feet above the runway then bled off the speed gradually - still landed way shorter than any aircraft I had ever flown before so it was a new era anyway.

For normal landings I currently stick with 1.3 times Vs/Vso on final down to the threshold.

FWIW - once I adjusted the idle speed - that made a noticeable difference with the same airspeeds.

[kitfoxnick]

I’ve been gone a long while but this seams as good a place to step in as any. Get VGs! At my strip 900’ with trees 400’ from the threshold. My preference is to come in over the trees with a lot of flaps and a full slip to ground effect. Pop it out and almost three point it. Dump the flaps full brakes and stick forward. When the tail starts to feel light you can let it down. Never once do you get a chance to look at airspeed. My advice is to go slip your plane in landing configuration keep slowing down listening and feeling what your plane is saying. In a slip mine starts a little hum then a slight high vibration feeling right before it breaks. A little stick forward and it goes away. Practice falling leaf. Cover your airspeed up for a month. Best thing I did was fly whole summer with an airspeed indicator covered. The absolute shortest landing with out an obstacle is to enter a wings almost level mush and arrest your decent (flair) with the engine. Hopes this helps.

[Flybyjim]

Hi Nick,
What part of northeast Md? Where do you hangar? I fly into Clairmont from time to time on my way down to see Ted Bryant at Cambridge.

Jim

[kitfoxnick]

Hi Nick,
What part of northeast Md? Where do you hangar? I fly into Clairmont from time to time on my way down to see Ted Bryant at Cambridge.

Jim

I have a farm strip 1 mile south of the mason dixon line. Nearest airport is 0p2 shoestring

[Flybyjim]

Shoestring is where I first learned to fly with Larry Johnson. My farm airfield is 0PA2 just north of Carlisle, Pa. N94 My field is 1200 long 100 foot wide turf. I am flying a Rans S7 at this time building the Kitfox SS7.
Does your airfield have a # to locate?

[JoeRuscito]

Thanks for all the input guys. I did some practice this weekend (calm winds). 1.3 over stall speed in that configuration feels good and reducing to 5 mph below makes my decent rate feel much more like I remember at stick and rudder, these speeds are similar to what I had found was my best sink rate with no slip. For reference my speeds are: 1 notch of flaps stall=44, 1.3x=57, over the threshold = 52 --- full flaps stall = 39, 1.3x=51, over threshold = 45. These numbers give me plenty of flare authority but little to no float. This was similar to my experience at S&R, where they taught to fly right down to the runway, little to no round out and right into a flare/touchdown. This worked great for calm winds for me, but Im still hesitant to be so slow... Still lots to learn...

I may order up some VGs to see how they do.

[fastfred]

Those speeds sound pretty similar to my 7. Although I had the 45 over the numbers bite me hard one calm day .I would rather have some head wind and below 50 is out of my comfort zone anymore without some power. good info

[fastfred]

Personally I rarely seem to need a slip. Like S and R taught us fly the fox down to the approach as slow as you can then ease back on the stick to slow down to stall on the numbers . I usually don't below 60.

[Shadowrider]

Joe I have found that VG'S help a ton, but can make it worse if you don't fly slower, as far as landing distance goes.

[redbowen]

Dave said a lot of what I am thinking on this issue. 1.3 Vs0 is a slow as you should make your approaches safely. I suggest going up to altitude and set up the same configuration you have as you come over your obstacle, and get slow enough to stall it, many times until you can recognize the onset signs. Without VG’s you will get more notification buffeting. Note your attitude and indicated airspeed, cross check with ground speed by doing it in multiple directions. I recommend this because in a slip your airspeed indicator is unreliable so if you pay attention to your airspeed vs ground speed on approach you can determine your winds to some degree and then you can cross check your speeds. Now I am not going to tell you that I don’t go below 1.3, because I do, but I usually do it at the very end of the approach. I use 50 mph down to just shy of the flare. That gives you the energy to flare to stall without adding power, but you can flare to 45 add power and get a bit slower as you do a full stall landing. With my so called heavy Lycoming Kitfox 5 that will give me a consistent 200’ landing with no wind. Add some wind and it gets nice and short. The best thing you can do is every time you fly go up to altitude and do some stalls in landing configuration. Stall numbers one day will vary from another based on density altitude and aircraft loading, winds, turbulence, etc. So the more you practice the stalls the better you get at recognizing the onset and learn how to avoid pushing past that point.
Great question. Fly safe, practice often.


Project Kitfox

[redbowen]

This is very true with the VG’s, they absolutely work and lower your stall speeds but they also remove the onset signs. It was one of the first things I noticed about the VG’s, Stalls slower with little warning.




Project Kitfox

[n85ae]

Take it up to altitude and try. I have slowed mine down and slipped all the way until it stops flying. I get
a really hard buffeting rattle in the turtledeck right before stall, and if you're trimmed to require holding
some back pressure it flies right out of it with relaxing the controls.

I kick in slip very frequently for glidepath control, even on very short final. I think it's a natural thing
in these airplanes to use.

I can't speak for other people's planes, but mine gives plenty of warning when it is unhappy while slow
and cross controlled.

Actually my airplane unless you pull the nose up hard with power and intentionally stall it with a lot of
attitude, never does anything very surprising.

The only time my airplane misbehaved is with 22 degrees flaperons, and since then I mechanically
blocked the slot for maximum 11 degrees.

Jeff

[JoeRuscito]

Jeff, your plane sounds like it behaves similarly to mine when testing aggressive slips at altitude. As long as I approach stall in a less than super aggressive fashion, even in a full rudder deflection slip, the plane gives plenty of warning and barely drops a wing if at all. Reducing back pressure recovers and I can even stay un coordinated through the recovery right back into a slip. I haven't done any very aggressive pull ups but Im sure those might get more exciting. Ive done these with both full flaps and half flaps. I do notice with full flaps the break is more defined.

[fastfred]

Hey Bryan

Project Kitfox[/ Maybe we should clarify where to use the 1.3 figure? Where does the approach start? Some guys tell me get down to approach speed turning a base others define approach as the final or short final. Personally I don't like to turn to final at 55 or even 60 as the kitfox slows down very quickly. I would also slip at a higher speed for this same reason. 50 or below on final is out of my comfort level until I am into the flare. I don't plan on winning any STOL competitions either.
Anyway when on approach do you get to that 1.3 or below?

[Rodney]

Joe - If your thinking of putting VG's on - Alex Di Sessi has an excellent youtube video on the subject of VG's.

He presents some pretty convincing information regarding placement of the VG's. You might find it interesting.

Regards
Rodney

[TRegli]

Bringing this thread back to life....

Wondering if others have had this phenomenon and/or could help me understand it better:
I took my model V up to 5000' to practice deep slips. (My V is setup up like a model 7 with the larger elevator, speedster tail, and longer nose) My CG was at 11.2, weight at 1123#. I applied full flaps, full right rudder, and dropped the left wing.. all seemed like a normal slip. However after about 5 seconds in this configuration, the rudder pedal lightened up and the control stick lightened up, a control reversal I believe? The plane seemed to be getting deeper into the slip after this happened- Yawing further to the right, left wing dropping more. I immediately took it out of the slip which took some force on both the pedal and and stick.

I repeated the test again with the same results. Essentially I could let go of the controls and the plane would stay/deepen into the slip. I did not see how far it would continue to go into the slip like this.

Is this common on the kitfox? Has anyone else had this happen? Maybe my procedures are wrong? Thanks!

[Dave S]

T,

What was your airspeed before initiating the slip?

Assuming engine at Idle or did you have some power in?

[jiott]

I always do my slips with 1/2 flaps and have never had the issue you describe. Can go very aggressive with full rudder and drastically dropped opposite wing. For some reason have never tried with full flaps; guess I have never found the need.

[TRegli]

Dave,

I entered the slip at 60 MPH (simulating high on final, slightly overspeed). Full flaps.

Jim, thats a good point. I have been landing with half flaps. I just figured I would try full flaps.