What Is The Lowest AGL You Will Slip Prior To Landing

Sinistar

Sinistar

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Brad
Well first I should clarify. This is not a crosswind landing slip but a slip to reduce altitude prior to landing and/or knock down some speed. We were flying last night and Kari wanted to practice a simulated engine fire. We setup at 3500agl directly over our sleepy airport. No planes in the pattern. Nobody on the ground. Wind was down the runway at 5kts. Announced on final time. Go time.

She got it into a nice steep spiral descent right away, airspeed indicating around 125mph and way pegged the VSI. I think she knocked out just shy of 3000ft of the descent in just over a minute. I gave her **** for ears popping. It ended with us coming in pretty hot just prior to the numbers at just around 100mph with flaps 10. We did not turn off the master so we did use flaps. At this point she was maybe 40ft above the numbers and she laid on a pretty gnarly slip to kill off a ton of speed and get it down right now to about 10ft or so. All of a sudden airspeed is about 80mph and ended like a power off 180 (well, it was a power off 180).

I guess I never even thought of doing an aggressive slip like that so close to the ground (excluding crosswind landing slips). Then again it was something more urgent (simulated) so makes a lot of sense. Definitely not something I have ever been taught. Is this just a comfort level thing?
 
I've never thought about it like that... but my, well, approach (sorry) to this is if I'm not established on final then I'm going around. My simple cherokee 140 is easy to get established on final (kind of hard to get behind that slow bird), so, I don't know, maybe the last 200' or 300' feet AGL.

Again, I don't want to pursue a bad approach. If I'm so high that I need an aggressive slip, then I've messed up and I'm just going to go around.
 
I’ve done just a few feet over the runway surface on several occasions. I’m comfortable with it to 10ft or so.
 
Sinistar said:
Well first I should clarify. This is not a crosswind landing slip but a slip to reduce altitude prior to landing and/or knock down some speed. We were flying last night and Kari wanted to practice a simulated engine fire. We setup at 3500agl directly over our sleepy airport. No planes in the pattern. Nobody on the ground. Wind was down the runway at 5kts. Announced on final time. Go time.

She got it into a nice steep spiral descent right away, airspeed indicating around 125mph and way pegged the VSI. I think she knocked out just shy of 3000ft of the descent in just over a minute. I gave her **** for ears popping. It ended with us coming in pretty hot just prior to the numbers at just around 100mph with flaps 10. We did not turn off the master so we did use flaps. At this point she was maybe 40ft above the numbers and she laid on a pretty gnarly slip to kill off a ton of speed and get it down right now to about 10ft or so. All of a sudden airspeed is about 80mph and ended like a power off 180 (well, it was a power off 180).

I guess I never even thought of doing an aggressive slip like that so close to the ground (excluding crosswind landing slips). Then again it was something more urgent (simulated) so makes a lot of sense. Definitely not something I have ever been taught. Is this just a comfort level thing?
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I've done very low like that. I slip a lot so it's no big thang to me. A ya so low ya better be watchin the wingtips over the runway slip probably wouldn't be a good idea for someone to who slips are not routine.
 
A slip can be a very well controlled maneuver. In gliders often performed very close to the ground - maybe 10’.
 
I’ve slipped the Mooney in ground effect for a few hundred feet more than once. Only for fun though. Normally, if I really need to be slipping at that point I’ll go around.

In gliders I’ve slipped all the way down the runway in ground effect. I’m notorious for coming in too high, but I’ll be damned if Im going to land out.

I’d say a couple feet.
 
Never really thought about it. I'll slip nearly to the ground if needed. If you are smooth and in control, it's still a stabilized approach. Watch guys land a Pitts, they use a slip just so they can see!
 
Touch the wheel before the wingtip.

When I used to fly my Maule into KMSP, I’d fly cruise+5 mph to the numbers, kick into a slip right over the ground for about 3 seconds, check airspeed, add flaps, and slip for another few seconds so I could land.
 
No flaps on my plane, I'll modulate the slip to control the glide path all the way into the flare if necessary.
 
Aerodynamically, the airplane doesn't know if you're 3 feet or 3000 feet about the runway in a slip...if you're doing it right, you're slipping the airplane onto the pavement in a crosswind. Even if it's not a crosswind, in some aircraft it's common procedure to slip the thing to the ground, as mentioned above. What I'm getting at is, I think this is just a psychological thing for you. Slip away in good conscience!
 
In the Champ slip to about the flare but as mentioned not looking at the altimeter. In the '57 Cessna 172 with 40 degrees of flaps your not supposed to slip it with full flaps you certainly don't need to. I swear if you pull 40 degrees at pattern altitude on short final you will still hit the numbers. :) It is a lot of drag.
 
In a side slip almost to the ground. For a forward slip, IDK, sometimes you have to do what you have to do, but as a general rule I would like to be stabilized at least 100' AGL...
 
DFH65 said:
In the Champ slip to about the flare but as mentioned not looking at the altimeter. In the '57 Cessna 172 with 40 degrees of flaps your not supposed to slip it with full flaps you certainly don't need to. I swear if you pull 40 degrees at pattern altitude on short final you will still hit the numbers. :) It is a lot of drag.
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Doesn't get much better than a full rudder deflection slip in a Champ
 
PeterNSteinmetz said:
gliders
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my first few flights were with my brother in law in a glider (he was a glider pilot)

to the OP.. 10' seems fine.. if it's a plane you are comfortable with and proficient in you can slip pretty damn close
 
All the way to the rudder kick if I truly need the drag. Trick is to know if you have long low wingtips, which as someone else said... Often is taught best in gliders...

And I dragged the number one engine nacelle in the 747-400 sim apparently. Lol. Don't do that. Guy was demoing to me that it was possible to land it well above the max crosswind allowed, but there's a reason for that number... Haha.
 
As others have said, as long as is needed for a safe landing. If you can't assure a safe landing, go around. A forward slip to touchdown is no different than any x-wind landing, the plane doesn't care where the runway is
 
drummer4468 said:
As others have said, as long as is needed for a safe landing. If you can't assure a safe landing, go around. A forward slip to touchdown is no different than any x-wind landing, the plane doesn't care where the runway is
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Not quite. The sole purpose of a forward slip is rapid altitude loss. In an aircraft with full flaps extended, the sink rate can be very high. In a forward slip with no cross wind, the longitudinal axis is not aligned with the ground track of the plane. The plane is slipping forward, with power off with a purposefully high sink rate. To land the pilot will find himself having to align the longitudinal axis with the ground track and reducing the sink rate for a landing. Most pilots use the entry into ground effect as zone to make those corrections.

The purpose of the side slip is to allow landing with the longitudinal axis aligned with ground track and a near normal descent rate for landing. The airplanes ground track in a calm wind is to a side with the nose aligned with the runway. In a xwind, the force of the xwind stops the side motion. The during the approach power is on providing a slower descent rate than the forward slip allowing for landing. The pilot does not need to change the descent rate or the realign the longitudinal axis for landing.
 
midlifeflyer said:
I don't have a number. After all, I'm not looking at the altimeter on final. So my answer is the equivalent of knowing when something's pornographic.
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Lawyer jokes. :rolleyes::rolleyes:

I don’t know the lowest I’ve done this. Like Mark, I was looking outside. High enough that catching the wing on the ground was not even a remote concern.
 
After rereading the OP I want to throw this in. Since you are asking the question, maybe you are not highly experienced with slipping. If that’s the case, don’t get focused on how close you can get to the ground before straightening out for the touchdown. As you get more and more comfortable slipping, you can straighten out later and later, but this is no race. Take your time and develop proficiency and comfort.

My $0.02,
 
Clip4 said:
Not quite. The sole purpose of a forward slip is rapid altitude loss. In an aircraft with full flaps extended, the sink rate can be very high. In a forward slip with no cross wind, the longitudinal axis is not aligned with the ground track of the plane. The plane is slipping forward, with power off with a purposefully high sink rate. To land the pilot will find himself having to align the longitudinal axis with the ground track and reducing the sink rate for a landing. Most pilots use the entry into ground effect as zone to make those corrections.

The purpose of the side slip is to allow landing with the longitudinal axis aligned with ground track and a near normal descent rate for landing. The airplanes ground track in a calm wind is to a side with the nose aligned with the runway. In a xwind, the force of the xwind stops the side motion. The during the approach power is on providing a slower descent rate than the forward slip allowing for landing. The pilot does not need to change the descent rate or the realign the longitudinal axis for landing.
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I understand what you're saying, but aerodynamically they're the same thing. It's about aligning the plane in a direction different than the relative wind. The forward slip only results in rapid descent because we allow it to, taking advantage of the added drag to keep speed under control. This is amplified by the fact they're always done without power to maximize descent and minimize forward speed. The only difference is just before the actual touchdown, when the control inputs need to be changed to align longitudinally, which is something that should happen naturally already.
 
For steady lightish cross winds I tend to crab, so I am fine with kicking the rudder to straighten the nose just before mains touch. In Gusty or strong cross winds I side slip to wheels on the runway.
So, I am comfortable having the slip to the runway, and also comfortable with the kick to align the plane just before mains touch.
With that said, I pretty much only forward slip for practice or when practicing emergency/urgent descendants and landing (urgent = bio induced emergency). Otherwise I consider needing a slip a sign of a go around required.

Tim

Sent from my HD1907 using Tapatalk
 
My kid will tell you all my landings are all power off 180’s...I do tend to fly tight patterns...hard to break old Helicopter habits but no problem taking a slip to the flare but would rather plan better than that.
 
MauleSkinner said:
So what kind of slip am I doing in ground effect to bleed off the 50-60 mph so I can land?
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Fools slip. If you need to bleed off that much speed, do it before the plane experiences a drag reduction in ground effect.
 
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