The big slip

In general I think the nose up-slow-descend method versus the dive dirty varies by aircraft weight and configuration.

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This is no doubt true, however my buddy (retired Reeve Aleutian captain) told me he's successfully used that technique in a wide variety of planes. But all I know from personal experience is my -12. So my suggestion would be to do some controlled experimentation in one's own plane and go by those results.

Gordon Misch said:

This is no doubt true, however my buddy (retired Reeve Aleutian captain) told me he's successfully used that technique in a wide variety of planes. But all I know from personal experience is my -12. So my suggestion would be to do some controlled experimentation in one's own plane and go by those results.

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I believe the "Dive Dirty to Land" method has been extensively researched and practiced by our very own Overeasy Guy. He has, for years, made extensive use of the this procedure to land his Super Cub. What's more is he often accompanies the maneuver with a healthy does of power to really get hauling in that last few hundred feet of flight. The maneuver is completed following contact with the ground on the mains with a very healthy dose of brakes.

It really is a spectacular method of landing a Super Cub and has provided hours of enjoyment for those fortunate enough to witness his unique technique in action.

Just opinion: Flaps or none can dictate and affect the method. I learned in a 7ECA where slips were preferred to get down now using fuselage profile drag. Then an instructor demonstrated the nose up-slow down-descend method. But for me to be comfortable that takes air that not too disturbed by mechanical turbulence. As mentioned it does take adequate air over the controls to fly with authority particularly when it's gusting.

The revelation that supported the "dive dirty method" were flaps. First in a PA-18, then a Beaver, then a C-185. How nice it was to be able create drag without slips that then required power and nose down to maintain glide path plus chosen airspeed. Point and shoot to the ground. Watch an Otter or Twin Otter with double slotted flaps land....and now the PStol flaps same-o.

Slips have their place (like Taylorcraft or J-3) but if given a choice I'd take the drag of flaps or extended gear instead.

Edit: I might add that diving near Vfe but below Va was preferred in turbulence; if relatively calm I prefer the slow and fly a stabilized an approach near 1.2-1.3 Vso.

Gary

This a great discussion. Now I have a whole bunch of things to try out!

I agree with #63. In Stick and Rudder, Langewische emphasizes low speed to get down at a steep angle, rather than dive. However, that doesn't address using flaps. In my T-Craft, and in my -12 before I installed flaps, slow and maybe a slip was the ticket.

"Dive dirty"....seems like the extra speed would result in a lot of float after getting down into ground effect at the runway.
I see a lot of high speed final approaches ("diving for the runway") at my airport,
generally resulting in a looong float down the runway before touching down.
I often comment "there goes another guy working on his float rating".

"Flying on the edge is safe as long as you know where the edge is."

Sage advice for many things in life. Problem is, the location of "The Edge" was often illusive to me. Closer proximity to "The Edge" often results in the exponential increase in the exhilaration factor.

If you're landing with no obstacles to clear, I would agree that flying as close to stall speed as the wind conditions will allow, and using power to control the last few feet of descent may well produce the shortest landing roll. Steve Henry's recent video for the National STOL competition shows this pretty clearly. You can see him "hovering" along for maybe 30-50 feet, tweaking the throttle to remain airborne. Then, as he arrives at the line, he dumps the power and the plane immediately lands with a VERY short rollout. Thankfully, he's got long-stroke gear to handle the somewhat "stout" landing.

But with more "normal" airplanes, and more "typical" pilot skill (Steve is way more skilled than I), and in a more "typical" short-field situation with obstacles in the approach path, that technique would have me spending a LOT of time in what we helicopter pilots refer to as the "deadman's curve" airspeed/altitude profile. Since I'd be already right at the stalling speed, if the engine quit while I was above the trees, wires, or other obstacles, I'd have no remaining options... I definitely would be going to hit an obstacle, and the odds of damaging the plane (and/or myself) are pretty much 100%.

The so-called "dive dirty" technique is NOT, in my opinion, the "other" true alternative to the "nose high and slow" approach in real-world short-field situations. I've seen a few pilots at some of the STOL competitions try the "dive dirty" technique in the "over a 50-foot obstacle" competitions. They approach just barely above the obstacle height with full flaps. As soon as they clear the obstacle, they drop the nose (dive) to lose that altitude. Every time I've seen it used, it resulted in the airplane accelerating just enough to go floating down the runway in ground effect, with correspondingly increased landing distances. I've never seen a competitive short landing result from that technique. And if it doesn't work in those highly controlled "contest" circumstances, in airplanes typically optimized for STOL contests, flown by some of the most skilled STOL pilots on the planet, what would lead me to think it would work in my airplane out in the "real world"? For me, the "dive dirty" approach is a non-starter.

By contrast, the folks who establish a stabilized descent angle that clears the obstacle at the steepest angle they can maintain to the landing point (flaps, slip, or some combination of the two) have more options available once the clear the obstacle. They could lower the nose, but that will likely increase their landing distance (see above). They are more likely to be already using power to maintain their descent profile, so that they are still flying just above the stall speed as they cross the line, so there is less floating down the runway, and they wind up with shorter landing distances as a result.

For as for me, I'm way more of an "ordinary" (mere mortal) pilot, flying a pretty capable but more "ordinary" airplane – nothing like the specially prepared Carbon Cubs, Huskies, and "one-off" special-purpose STOL contest aircraft. The airplane is probably more capable than I am, if I'm honest with myself. And the main reason I would choose to use the "stabilized descent angle" comes down to preserving more options. If the engine quits, I'm still going to clear the obstacle(s) on my chosen glide path, so an engine failure carries a lower risk. And if it does quit, I have the option to use some of my "zoom reserve" to clear that last tree, then lower the nose to restore the energy for flaring, knowing that it's better to "roll" into an obstacle at the end of my landing (where I'd be going pretty slow) than to hit something while at flying speed.

Just one (average) man's thoughts on the subject...

In my experiments with diving or near-stall, the float distance was not dramatically different. But the distance was shorter diving. However, that was near Vfe (85 in the Cub).

An advantage of the speed is "energy in the bank" as stated. An example - yesterday I landed over a significant obstacle due to winds. By significant, I mean a fairly steep hill 1000 ft or more high right off the end of the strip. In quiet winds I would use slow speed and easily sink as required. But yesterday's winds were gusty and a little extra speed coupled with a slight dive after clearing the last trees had me touching down at the normal spot.

I've done some spot-landing playing with friends, landing over an obstacle (just a few feet high). In that case nice and slow with a little shot of power to flare seemed to be the best.

To me, bottom line is to have more than one tool in one's toolbox, though I've learned that once a tool is chosen to stay with it and not keep changing my mind.

So now that I have pontificated on how great a steep/slow approach and slips I will say sometimes it does not work. If the approach air is extremely turbulent you can get pushed down or lifted up a great example is Skwetna STOL comp. Getting through that last 30 feet is sometimes best done by getting the nose down and sticking the landing. Hitting your spot 5 mph faster is about the same as a 50 ft float over the spot landing. I agree with Gordon more tools the better.
DENNY

Gordon Misch said:

An advantage of the speed is "energy in the bank" as stated. An example - yesterday I landed over a significant obstacle due to winds. By significant, I mean a fairly steep hill 1000 ft or more high right off the end of the strip. In quiet winds I would use slow speed and easily sink as required. But yesterday's winds were gusty and a little extra speed coupled with a slight dive after clearing the last trees had me touching down at the normal spot.

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In gusty conditions as you describe, I find that a steep approach with minimum power minimizes the turbulent ride reducing the manhandling of the controls. Dragging in with power exposes the under side of the wing to the waves of air. Imagine motoring across a lake in a boat with the bow high and the waves slapping the bottom. It a very rough ride. Next imagine skimming across the same waves at a bit higher speed with the angle of the bottom flat to the path over the surface. The ride is smoother. Allowing the plane's nose to seek it's own angle without power minimizes the airwaves turbulence. Thus a smoother descent with less control manipulation and fewer surprises.

oops: DENNY beat me to it.

Guessing he doesn't fly many loads into short mountain strips with that 180.

Gordon Misch said:

Full-rudder slip with full flaps, initiated with a near-knife-edge = drop like an anvil. Love it! On the other hand, a highly experienced buddy sez if you gotta slip you planned poorly. I told him I'd ignore that. I think he's jealous cuz his 180 can't slip as effectively as a Cub:lol:.

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"A slip is the result of poor planning" WTF? When you turn final, with a bit of slip required, you can still make the numbers if your engine quits and you encounter even the slightest bit of sink. Perfect planning, if you ask me, and something to practice. Using power on final teaches nothing but dependence on power.

Question: Gordon points out that drag increases with the square of speed. So why doesn't speeding up in a slip work? The whole fuselage is now getting that square-law drag increase.

I'm in the group that slips almost every landing, I like the visibility and its just how I've gotten comfortable controlling my decent. I also almost always do a left wing low slip, only time I do it other way is for crosswind and I'll admit I'm rusty at it.

this video was in another thread on here somewhere but I'll repost seeing it seems some people think a slip is as bad as a skid when its not and this guy does the best job explaining I've seen yet.

There is more than one slip. For example, you have the slip with the rudder pedal in 25%, 50%, 75% and 100% and then also everything in between. They are all different and they feel different too. I feel like I have limited mental horsepower and muscle memory. I can only be proficient at one type of slip in my lifetime, so I do it with the pedal in 100%.

Getting to center line and staying on glide path and maintaining approach speed is then a matter of stick control and throttle only. After 15 years in a Cirrus, relearning the slip in a SuperCub has been a little challenging, but eliminating the rudder variable has made it a little easier.

My 2 cents.

Skywalker said:

"A slip is the result of poor planning" WTF? When you turn final, with a bit of slip required, you can still make the numbers if your engine quits and you encounter even the slightest bit of sink. Perfect planning, if you ask me, and something to practice. Using power on final teaches nothing but dependence on power.

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He was mostly just razzing me. Though that particular time I WAS way too high and had to slip aggressively.

Skywalker said:

Question: Gordon points out that drag increases with the square of speed. So why doesn't speeding up in a slip work? The whole fuselage is now getting that square-law drag increase.

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Agree. End up going faster than otherwise, but total energy is dissipated faster. Same with diving to max flap extension speed to dump energy.

labrador_cub said:

I'm in the group that slips almost every landing, I like the visibility and its just how I've gotten comfortable controlling my decent. I also almost always do a left wing low slip, only time I do it other way is for crosswind and I'll admit I'm rusty at it.

this video was in another thread on here somewhere but I'll repost seeing it seems some people think a slip is as bad as a skid when its not and this guy does the best job explaining I've seen yet.

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I'm sure the woman in the audience on her cell phone got a lot from the presentation.

I think sometimes the learn-ed don't communicate as effectively with the unlearn-ed as they could. I think it's because they haven't been mentally where the people they are teaching are for some time. Not faulting them for that and great respect for their abilities. Example from the video: The guy on the left makes the point of how screwed you are when you get in the skid-stall but fails to add that relief is just getting the airplane out of it by lowering the nose some. For me, the little things you can remember easily are the life-savers. Unload the wing! Step on the high wing that's coming up! In the critical moment, you have to just have one thought to grab. Understanding the entire situation is great but...you see where I'm going. (Push the mixture back in, the other knob is the carb heat.)
I was taught to slip early and I do it when needed and don't worry about it. One of the tools in the box. (Sometimes helps to let unsuspecting passengers know what's coming tho)

I was out doing a tailwheel sign off in a Citabria the other day and ended up teaching slips to a short field landing. I demonstrated at altitude and we played a bit and the plane would not spin enter without reefing it into it with excessive pitch to wipe the lift off the forward wing. It was a good lesson and never once was the airspeed indicator used to teach; the stick and feel taught it.

We did one "normal" pattern and I noted his altitude in reference to the target and what a normal glidepath looked like.

We went back around and set an airspeed at the perch and held the nose up to hold that (quit looking at the airspeed and tell me what it is by feel was the teaching moment there) and made a constant turn to final. Reaching final we set the amount of sink needed with a slip and kept a sight picture of the target in view. We slipped into the wind and away from the wind to show how drift could be affected by a crosswind. One issue he kept having was the transition to coordinated flight (with crosswind correction) below 100 feet. He had a tendency to round out to arrest the sink rate and push for the spot we were trying to hit and float with the added airspeed. With a couple of tries he got a rhythm and learned to not let the rate build up late but rather start higher and start scrubbing off some sink rate at 500' rather than try to correct it all at once at round out where he scrubbed speed to touchdown. I taught him airspeed is advisory as the slip affects the static system (I was taught that) and if you enter at a speed you likely are going to exit on the speed if you don't let the nose drop or pull on it too much in the slip (we demonstrated this at altitude).

One other interesting thing was the reaction of the stall horn to the slip and his built in muscle memory to immediately power out of any blip from it. That took a little unlearning as in slips that stall warning, like the pitot, can give some blips and blurps as it is designed with a certain relative wind in mind. We had to work on respecting it but not reacting and aborting if it blipped. I am not sure his college rote aviation training program will like the lesson, but he left with a smile and really enjoyed poking around that end of the envelope.

Great lesson and I went out and repeated it in my 180 after by myself. I was a bit rusty but got it right after a few circuits. Never know something until you teach it.

Paul Jackson said:

Never know something until you teach it.

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Totally agree...

sj

Thanks Lab, great video

labrador_cub said:

I'm in the group that slips almost every landing, I like the visibility and its just how I've gotten comfortable controlling my decent. I also almost always do a left wing low slip, only time I do it other way is for crosswind and I'll admit I'm rusty at it.

this video was in another thread on here somewhere but I'll repost seeing it seems some people think a slip is as bad as a skid when its not and this guy does the best job explaining I've seen yet.

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After reading all the comments, I look back at my training. Back seat of a J-3 on skis, my instructor in the front. He looks back, yells at me (no intercom back then, heck no electrical) "Push the stick full left and push full right rudder". Slips were used, like someone has already said, as another tool in the tool box, that was it. Some planes slip nicer (Cubs, Champs, Chiefs, Vagabonds) than others, but you learned that as you progressed with training or practiced on your own.
I'd rather have that tool when that thing that spins on the nose of the airplane stops in the air (or goes bye-bye, true story) and you MUST make that field. Keep it high and when you KNOW you can make it, drop the extra altitude with a slip and land.

Now, if you want to talk about what happens when you tick off your instructor doing full power stalls in an 85 HP Champ with a climb prop and you're letting the nose turn..... Yep, he had me stomp on the right rudder pedal. You go from seeing sky to seeing the ground REALLY quick!

I believe the slip to a landing is a great tool. I use it often in light airplanes to steepen the approach angle if the available "drag" devices won't provide the approach path necessary. Or sometimes just for fun. In our no-flap PA-11, they are a pure joy to execute. Again in light airplanes equipped with flaps, it is rarely required for most runways I land on. In jet equipment, you are restricted to using runways that don't require a slip in addition to flaps and leading edge devices to fly the proper approach path. Stable approach paths in the landing configuration are required from at least 500 feet above touchdown or a go-around is mandated. So with jets, a slip is essentially an emergency maneuver albeit a very good one to have up your sleeve in an actual emergency.

The slip method to a crosswind landing is standard for me in everything I fly. The only exception was in the "stretch" DC-8 days, especially those modified with high bypass fan engines. Those airplanes will drag an outboard engine pod on the runway in the touchdown attitude if past 2.5 degrees of roll. They required the "crab and kick" crosswind landing technique although most of us snuck a very little slip in there as well. I don't know if fly by wire airplanes allow you to cross control in order to use the slip technique in a cross wind. From riding in the back of Airbuses, it doesn't seem so. I would love to hear from FBW pilots on this issue.

Every once in a while, I like to intentionally fly a REALLY tight pattern just to see how steep an approach I can make using a max-effort slip. I'm always amazed at just how well you can scrub off excess altitude in my plane (a somewhat slab-sided RANS S-6ES Coyote II) when you pin the stick to one side and the rudder to the stops the other way. It almost reminds me of the steep angles I used to see when performing power-off autorotations (to the ground) back in my Army instructor pilot days... The joke was to look for your landing spot through the chin bubble - between your feet. (Not too far off, either...)

The other day, we had a crosswind from the right (somewhat unusual around here). I realized I almost never do a slip to the copilot's side, but this was the better way with that right crosswind. It felt a bit weird at first, but after a couple of iterations, it felt more natural. I did, however, find that I tended to let the nose drop a bit when coming out of the slip, which increased my airspeed a bit and caused the plane to float a little – touchdown was about 150-200 ft beyond my target... Took me two more trips around the pattern to get the slip exit to roundout flare right, so that I could nail my pre-selected landing spot. Fun to be at pattern altitude on short final, and still nail the first stripe on the runway! I didn't look much at the VSI, but it had to be well over 1000 fpm down!

PS - There's no stall warning (horn or anything else) in this plane – you just have to "feel" the stall coming. But the airplane talks to you pretty good when it's about to give up! I have to say, I do NOT miss that squawking on approach...

Finding out what the max slip looks like will help when approaching a tiny spot in the woods after a power loss. If you do a circle you may lose sight of the spot, but you have to bring some margin of energy with you. I like to approach my little strip at the same altitude and wait a little longer each time before pulling power and doing a maximum slip. I wouldn't have believed how steep that angle is until I tried it.

Skywalker said:

Finding out what the max slip looks like will help when approaching a tiny spot in the woods after a power loss. If you do a circle you may lose sight of the spot, but you have to bring some margin of energy with you. I like to approach my little strip at the same altitude and wait a little longer each time before pulling power and doing a maximum slip. I wouldn't have believed how steep that angle is until I tried it.

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The Force is strong with this one.

I've done a few slips over the years. Even better on floats

Glenn

i think the ultimate landing for engine out safety is a modified corsair style turning carrier approach with the decent being managed with slip and speed managed with pitch. power is only used for fixing really big screw ups.
i always feel like i potentially came up short of a carrier deck if i had to add power to make it to the runway. and i think of rudder/slip as a % of safety margin. for me a good cub approach will always have about 30% rudder/slip input and the power will be just a touch off the idle stop. if the engine quits the glide should (in theory) be fairly unchanged, and you still have 70% more rudder too help get you down. but even better is that that one can extend your glide by neutralizing rudder. its equivalent to a glider pilots going to half spoiler on downwind.
slipping carrier approach is my favorite back country approach. on down wind when i get abeam the runway #'s i reduce power to 1300ish rpm, enter my slip and base turn at the same time, and carry the slip all the way before flare. adjusting my landing point with slip. if done perfectly the instant you complete your turn to final you also roll leval, exit the slip and touch down all within instants of each other. when it happens all within a nano-instant it can be beyond satisfying.......and if your late hang on for dear life, lol.
using a slipping 180 turn approach with full rudder at idle and i can drop like a rock with almost 90degree bank and full control.... i can easily and comfortably get into places i'd not beable to fly back out of.

Plus, even doing a wings level approach or any approach that your too fast you can throw in a big slip in GE 4' up to lose the extra speed

Glenn