Can I slip with flaps?

Salty said:
I'm still trying to get my head around how you can control a plane with full flaps if they "blank out" air over the tail.
Click to expand...
Do you like “disrupts the airflow over the tail” better? That is probably a more descriptive explanation of what happens.
 
Salty said:
I'm still trying to get my head around how you can control a plane with full flaps if they "blank out" air over the tail.
Click to expand...

Ask a long body pilot. They don't slip with flaps out. I fly a short body, which slips just fine; I just try to fly in such a way that I don't need to, because it's inefficient (like riding the brakes down one hill before accelerating up the next one). If you're still confused, ask Don Kaye.
 
I was probing for more factual information regarding long body mooneys. It sounded more like like a folk tale as it was stated. And, trying to get at specifics. Does having flaps down really cause pitch control issues? That seems dubious. Or slipping with flaps down can cause pitch control issues? It was stated as though full flaps alone causes pitch control issues.
 
Just don’t slip a swept wing canard...with or without flaps. Could end up on your back. :(
 
My DPE for my private checkride was a C140 buff with thousands of hours in them and tens of thousands total time. He encouraged me to slip full flaps and I have done it many times since. A full flap slip will bring it done like an elevator. I have slipped the Mooney with flaps, but I don’t remember using full flaps. Full flap slipping is a great tool to have in the box. I am sure that anyone reading this knows that they should check into this scenario being safe with their specific aircraft type,
 
Velocity173 said:
Just don’t slip a swept wing canard...with or without flaps. Could end up on your back. :(
Click to expand...


It would be interesting to understand the aerodynamics of that. Is it from shading part of the canard with the forward fuselage? Or is there more going on there?
 
GRG55 said:
It would be interesting to understand the aerodynamics of that. Is it from shading part of the canard with the forward fuselage? Or is there more going on there?
Click to expand...

The Velocity flight manual mentions 3 possibilities during a forward slip. You can stall a winglet causing departure from controlled flight. The main wing due to its sweep can stall on the trailing side (away from the slip) much more easily than an unswept wing. Lastly, with so much fuselage ahead of the trailing wing, the wing can get blanked out from the relative wind and result in lack of lift / aileron control.

The VariEze flight manual just has a caution to avoid full control side slips at low altitudes because a winglet can stall, resulting in departure and a possible loss of 1,500 ft of altitude in the recovery.
 
Kansas Flyer said:
my Cardinal's manual says not to do it with more than half flaps so check your POH.
Click to expand...

luvflyin said:
What year and Model Cardinal? I’m looking at a 1977 C177B POH right now and it says “Slips are permitted with any flap setting.”
Click to expand...

The 1968 C-177 Owners Manual says, "Slips are prohibited in full flap approaches because of a downward pitch encountered under certain combinations of airspeed, sideslip angle and center of gravity loadings."

The current TCDS, though, has somewhat less restrictive language. On the original Model 177 a placard on the flap control must read, "Avoid slips with flaps extended." No such placard is required for the Models 177A and 177B.

The C-177 was originally designed to have a max 40° flap deflection. Cessna engineer and test pilot Bill Thompson wrote,

With the large, powerful flaps giving more than enough drag for a steep power-off descent, we had envisioned no need for forward slips for proper descents. Crosswind landing approaches in sideslips were typically performed with only one-half flaps for better rudder control. However, we were disturbed with control in a sideslip [...].​

A nose-down pitch was encountered during sideslips with 40° flaps, which as a result of tuft studies was attributed to stall of about 40% of the stabilator semi-span on the pro-slip (wing-low) side, and some loss of lift due to reduction of angle of attack on the wing-high side of the stabilator. Thompson quoted from an SAE report on the flight tests:

"The nose-down pitch characteristic was eliminated with 25° or lesser flap settings. It was considered mild with 30° flaps and, at this flap setting, it is felt in the controls as a heavy buffet at extreme sideslip angles and is easily controllable.
"In addition to this characteristic, the advantages of only 30° flaps (instead of 40°) were considered to:
"1. Improve the handling characteristics because of excessively high sink rates with full flaps as discussed previously.
"2. Provide easier flare-out capability.
"3. Improve the rate-of-climb in the balked landing go-around."
​
For all of these reasons, the maximum flap setting was established as 30-degrees for initial production.

[...]

Occasionally, an airplane in Mort Brown's production flight test activity would exhibit the previously-described pitch-down motion in flaps-down sideslips. Some of our customers would experience this in a crosswind landing flare where the pitch-down would bang the nosewheel hard enough to deform the firewall. We were unable to duplicate this fault on the prototype.
​
Ultimately the factory decided to incorporate slots in the leading edge of the stabilator so it could "tolerate a steeper downflow of air without stalling the under-surface of the stabilator." All Cardinals already in the field were retrofitted with the slots, at no cost to the customers. Pending the modification, a service bulletin called for a temporary physical limitation of flap travel to 15°.
 
Last edited:
Pilawt said:
The 1968 C-177 Owners Manual says, "Slips are prohibited in full flap approaches because of a downward pitch encountered under certain combinations of airspeed, sideslip angle and center of gravity loadings."

The current TCDS, though, has somewhat less restrictive language. On the original Model 177 a placard on the flap control must read, "Avoid slips with flaps extended." No such placard is required for the Models 177A and 177B.

The C-177 was originally designed to have a max 40° flap deflection. Cessna engineer and test pilot Bill Thompson wrote,

With the large, powerful flaps giving more than enough drag for a steep power-off descent, we had envisioned no need for forward slips for proper descents. Crosswind landing approaches in sideslips were typically performed with only one-half flaps for better rudder control. However, we were disturbed with control in a sideslip [...].​

A nose-down pitch was encountered during sideslips with 40° flaps, which as a result of tuft studies was attributed to stall of about 40% of the stabilator semi-span on the pro-slip (wing-low) side, and some loss of lift due to reduction of angle of attack on the wing-high side of the stabilator. Thompson quoted from an SAE report on the flight tests:

"The nose-down pitch characteristic was eliminated with 25° or lesser flap settings. It was considered mild with 30° flaps and, at this flap setting, it is felt in the controls as a heavy buffet at extreme sideslip angles and is easily controllable.
"In addition to this characteristic, the advantages of only 30° flaps (instead of 40°) were considered to:
"1. Improve the handling characteristics because of excessively high sink rates with full flaps as discussed previously.
"2. Provide easier flare-out capability.
"3. Improve the rate-of-climb in the balked landing go-around."
​
For all of these reasons, the maximum flap setting was established as 30-degrees for initial production.

[...]

Occasionally, an airplane in Mort Brown's production flight test activity would exhibit the previously-described pitch-down motion in flaps-down sideslips. Some of our customers would experience this in a crosswind landing flare where the pitch-down would bang the nosewheel hard enough to deform the firewall. We were unable to duplicate this fault on the prototype.​
Ultimately the factory decided to incorporate slots in the leading edge of the stabilator so it could "tolerate a steeper downflow of air without stalling the under-surface of the stabilator." All Cardinals already in the field were retrofitted with the slots, at no cost to the customers. Pending the modification, a service bulletin called for a temporary physical limitation of flap travel to 15°.
Click to expand...

Thanks for the info
 
What's wrong with you people? If you slip an airplane with full flaps you'll immediate overload the airframe past its design limits! The whole thing will come from together, catch fire, fall over, disappear down a black hole and be eaten by space monsters!
 
steingar said:
What's wrong with you people? If you slip an airplane with full flaps you'll immediate overload the airframe past its design limits! The whole thing will come from together, catch fire, fall over, disappear down a black hole and be eaten by space monsters!
Click to expand...
Unless you filed a flight plan.
 
Just go out and slip it up at stall elevation and find out for yourself how it behaves which will be ok.
 
mscard88 said:
I get the pitching motion in the flight school's 172N, no biggie. The flaps are limited to 30* in ours, small plate screwed under the flap handle to prevent going past 30*, I assume. Anyone know why that is? I keep meaning to ask the owner but never seem to get around to it.
Click to expand...
Interesting. 16 years ago as a student pilot I took a 172N up to about 6000 feet and experimented with this. That particular 172 had not been limited to 30* so this was at the full 40*. I tried and tried to get something scary to happen, but it never did. The worst I got was a very mild "bumping" oscillation feeling in the yoke from the elevator. It left me both disappointed, and relieved that I wasn't going to crash because I slipped to a landing with full flaps, and indeed the DPE asked me to do just that on my PPL checkride.

Today I slip The Branded Bird with full flaps, regularly, landing from the pattern on rwy 35 @KMPV, because I'm always a bit skittish about the ridge south of the field and turn base and final earlier, and higher, than I normally would. Depending on conditions, sometimes I find I have to slip fairly aggressively. TBB is a Cardinal not a 172, of course, and flaps are limited to 30*, but I've never encountered any weird aerodynamic effects when doing it.
 
MBDiagMan said:
My DPE for my private checkride was a C140 buff with thousands of hours in them and tens of thousands total time. He encouraged me to slip full flaps and I have done it many times since. A full flap slip will bring it done like an elevator.
Click to expand...

I don't think I ever slipped with flaps in the 140. In fact, I rarely used flaps at all. I don't think slipping with flaps would be an issue in this plane though since the flaps are so small. Are they placarded against it? Can't remember.

For those who don't think it could be a problem, I tend to go with what is recommended for the plane. A friend of mine had very little experience in his Cessna 170B and we were going into a short runway with trees at one end. On final, he decided he wasn't up to it and asked me to land the plane. We were high and he had maybe two notches of flaps in. I slipped it pretty hard and suddenly had the nose drop out and point very steeply down. It happened with no warning and very quickly. I added power and pulled out, flying down the runway. After landing, a lot of people told me it was a nice low pass. They had no idea it was unplanned.

It got my attention and in a Cessna with 40 degrees of flaps, there should be very little reason to slip with flaps anyway... they come down like a rock with just the flaps.
 
Lowflynjack said:
I don't think I ever slipped with flaps in the 140. In fact, I rarely used flaps at all. I don't think slipping with flaps would be an issue in this plane though since the flaps are so small. Are they placarded against it? Can't remember.
Click to expand...
I don’t believe so. The 1948 170 has pretty much the same itty bitty flaps and it slips just fine. You pretty much need to slip since the flaps don’t do much.

The 170B on the other hand has the same wing and flaps as the early 172s, so slipping with full flaps can be an issue.
 
Slipping with 25-40 flaps is practically a mandatory checkout/checkride item on a Cherokee
 
Many years ago I owned a C-177. N35152. So many years later I’m not sure whether it was an A or B but I do recall that the elevator had a slotted leading edge. I did indeed slip it in with full flaps, not ever recall having any handling issues with it. Might have something to do with the slots


Sent from my iPad using Tapatalk
 
Polarisguy said:
Many years ago I owned a C-177. N35152. So many years later I’m not sure whether it was an A or B but I do recall that the elevator had a slotted leading edge.
Click to expand...
With that registration number it was likely a 1975 C-177B.

The slotted stabilators were on all new Cardinals beginning with the 1969 177A. Cardinals built during the debut 1968 model year (Model 177, no suffix letter) were not built with the slots, but virtually all were eventually retrofitted under Cessna's recall program (dubbed "Cardinal Rule") at no cost to the owners.
 
Pilawt said:
The 1968 C-177 Owners Manual says, "Slips are prohibited in full flap approaches because of a downward pitch encountered under certain combinations of airspeed, sideslip angle and center of gravity loadings."

The current TCDS, though, has somewhat less restrictive language. On the original Model 177 a placard on the flap control must read, "Avoid slips with flaps extended." No such placard is required for the Models 177A and 177B.

The C-177 was originally designed to have a max 40° flap deflection. Cessna engineer and test pilot Bill Thompson wrote,

With the large, powerful flaps giving more than enough drag for a steep power-off descent, we had envisioned no need for forward slips for proper descents. Crosswind landing approaches in sideslips were typically performed with only one-half flaps for better rudder control. However, we were disturbed with control in a sideslip [...].​

A nose-down pitch was encountered during sideslips with 40° flaps, which as a result of tuft studies was attributed to stall of about 40% of the stabilator semi-span on the pro-slip (wing-low) side, and some loss of lift due to reduction of angle of attack on the wing-high side of the stabilator. Thompson quoted from an SAE report on the flight tests:

"The nose-down pitch characteristic was eliminated with 25° or lesser flap settings. It was considered mild with 30° flaps and, at this flap setting, it is felt in the controls as a heavy buffet at extreme sideslip angles and is easily controllable.
"In addition to this characteristic, the advantages of only 30° flaps (instead of 40°) were considered to:
"1. Improve the handling characteristics because of excessively high sink rates with full flaps as discussed previously.
"2. Provide easier flare-out capability.
"3. Improve the rate-of-climb in the balked landing go-around."
​
For all of these reasons, the maximum flap setting was established as 30-degrees for initial production.

[...]

Occasionally, an airplane in Mort Brown's production flight test activity would exhibit the previously-described pitch-down motion in flaps-down sideslips. Some of our customers would experience this in a crosswind landing flare where the pitch-down would bang the nosewheel hard enough to deform the firewall. We were unable to duplicate this fault on the prototype.​
Ultimately the factory decided to incorporate slots in the leading edge of the stabilator so it could "tolerate a steeper downflow of air without stalling the under-surface of the stabilator." All Cardinals already in the field were retrofitted with the slots, at no cost to the customers. Pending the modification, a service bulletin called for a temporary physical limitation of flap travel to 15°.
Click to expand...


I knew that sounded familiar. A couple of years ago, I used this post to help bolster my opinion that fwd slips with full flaps in a 172R was perfectly safe. The young CFI doing my club checkout eventually thanked me for the info. But, I'm not sure I ever convinced him: http://www.cessna172club.com/forum/ubbthreads.php?ubb=showflat&Number=67547
 
wilkersk said:
I knew that sounded familiar. A couple of years ago, I used this post to help bolster my opinion that fwd slips with full flaps in a 172R was perfectly safe. The young CFI doing my club checkout eventually thanked me for the info. But, I'm not sure I ever convinced him: http://www.cessna172club.com/forum/ubbthreads.php?ubb=showflat&Number=67547
Click to expand...

CFI's really differ. The place I got my ppl my original cfi was completely fine with slipping 172s with full flaps.

Couple years later I go do a checkout so I could rent one of their 172s and the cfi pulls the power and tells me to put it on the runway. In my opinion we weren't all that far off and I was quite sure we could make the runway so I start reaching for the flaps. He dissented...says wait until you are sure. I tried to fly a bit of a base to reduce the angle of approach to the runway. He's like nope. Make straight to it until you are sure.

That's great, so we come in quite high and 20* (guessing) off centerline. So I get in full flaps and a slip. Then he started whining about how we shouldn't be slipping in full flaps.

That was the single most uncomfortable landing I've made, and it certainly wouldn't qualify for any POA awards. I wasn't happy with his input as I would rather have tried my own idea on getting a more stabilized approach. Anyways it was still a good learning experience imo. I just think instructors need to let pilots and students make their own decisions within reason and if successful then great, if not then reset the exercise and try again.
 
azure said:
The worst I got was a very mild "bumping" oscillation feeling in the yoke from the elevator.
Click to expand...

This is all I’ve ever gotten out of any Cessna and even at that, it isn’t consistent or very repeatable.

I’m not completely dismissing the stories of the rapid nose down pitches a few people have seen.

I’m just saying I’ve never gotten one to do it at altitude or down low.

As someone else points out here though, you’re drag profile and sink rate are plenty high in any Cessna with 40 degrees of flaps that if you’re slipping one, you were WAY too high or too fast.

I’ve done it a few times to bleed off excess speed and rarely would I do it at slowest approach speed just to get a steeper angle out of it. Most obstacles just aren’t that tall.

Put it in for a few seconds to increase drag massively beyond the flaps themselves, and then take it back out and let the flaps do their thing.

There’s rarely much reason to crank in a massive slip with flaps 40 and HOLD it for long periods of time while slow. And at certain angles of attack, I could see the buffeting turn into a loss of lift on the horizontal stab resulting in pitching down.
 
I had a passenger step up on the wing wrong, stepped on the flaps and slipped. It messed up my wing and he got a pretty good cut on his forehead so I wouldn't recommend slipping on flaps.
 
Stevea621j said:
I had a passenger step up on the wing wrong, stepped on the flaps and slipped. It messed up my wing and he got a pretty good cut on his forehead so I wouldn't recommend slipping on flaps.
Click to expand...
Yup....that's dangerous. :yikes::ohsnap:
 
You can tell the Cessna pilots as they have the row of diamonds on their foreheads.
Navion pilots just have hydraulic fluid on their right knee.
 
Stevea621j said:
I had a passenger step up on the wing wrong, stepped on the flaps and slipped. It messed up my wing and he got a pretty good cut on his forehead so I wouldn't recommend slipping on flaps.
Click to expand...

One DPE and a local instructor tell the story of an instructor who trusted a student had locked the flap handle on a Piper properly, stepped on the flap deplaning, it dropped him, and many surgeries later he still has a permanent disability. Friend of theirs. Told in hushed tones and in that feel like they lost said friend. Apparently it really screwed him up bad.
 
You must log in or register to reply here.
Back
Top