Slip while hangin' on the prop and VG's

Theoretical question for you aviation gurus out there...

Suppose you are flying along at MCA, you know, approach speed for a super cub with VG's. We know that when you bank the plane, the stall speed will increase and the plane will stall (with VG's, this is usually just a gentle wobble to warn you), but now imagine you are coming straight in with power just above the stall and you decide to slip - with VGs. I am going to test this at altitude some time, but I just wondered if this would also have a significant effect on the stall speed.

By doing this, I was thinking that you would avoid the huge descent rate which occurs when you pull the power..

sj

!!

Before I got flaps all of my short approaches were done in a near full slip with power. Poor mans flaps are the side of the fuselage. Do the same thing now when needed, even with full flaps. Jerry.

Slips

Steve,

Yeah, saw your post earlier this afternoon, but only now have time to reply. I concur with Jerry, especially with no flaps.

Full rudder, full flap slips can be done to sluff airspeed or dump altitude or to steepen the decent up to the very last seconds just prior to landing. If hot - like 50 near the fence, a full slip can be entered (usually nosing toward any crosswind will be most effective) and held until final roundout at or just below 40 mph at 8 inches agl. There is no reason a full slip can't be entered and held until just below 40, and the 8 inches is because when you kick out of the slip that is right where you want to be in the last bit of the flare for the wheels to hit straight with your path of flight. With a crosswind, say from the right, as you transition from left wing low in the slip to right wing low in a yaw correction slip 8 inches is enough to keep the tires off as you swing through and ultimately land on the upwind wheel first.

On a steep approach, at idle, slipping at 40 over an obstacle is safe, presuming you are straight again just at the beginning of the flare to give the wing a full bite and to be rid of the drag for the flare. If you are over 40, the slip can be held into the flare until you hit 40 or otherwise you need the momentum for flare.

Slapping in full rudder when crossing a tree line and then straightening out just as quickly at the ground dumps tons of altitude in a hurry and leaves you in the same profile for flare, and much closer to the approach end of the strip.

There is not much greater of a stall speed for the full slip in non-turning flight - just the drag - and dumping the drag by straightening out is a 1 second affair so that is why it can be held so long and late near the ground. You do mention MCA - so the slip you mean is real nose high. It does seem that I nose over when entering a slip to keep the AOA constant with the new descent profile and also pulling the nose up simultaneous with kicking out of the slip in the flare. Speed control and AOA control is everything. Nice that all of this can happen well above the stall with vg's.

I have one strip that I go into that can only be entered from one direction. A gusty NW breeze means a quartering tailwind on final. But at the ground the tailwind goes to half, so suddenly I have extra airspeed - like airspeed shaking around 45 suddenly is steady at 55. A slip dissipates that fast.

Also, keeping the engine warm and increasing the descent profile with a slip is safe because if the motor quits you can just kick out of the slip and make the runway.

Steve, I know you know all this stuff already. I look forward to the next time we can all get together and enjoy our company and airplanes.

Bob Breeden

Bob,

A very thorough discourse on slips, thanks.

Since I use slips all the time in my flapless wonder, I was particlarly interested in a slip when flying like I was today, in a friends top cub at zero indicated airspeed, full flaps, and VGs. I had a 10mph ground speed according to the gps, but a decent (probably at least 20mph) headwind.

sj

Steve, I do the same with the L18C (90 hp flapless SC). Best way I have found to get it in short. I used this technique in the Clipper I learned to fly in. After more than 1400 hrs. in that plane I could hang it on the prop and slip it all the way down the runway much slower than normal stall speed. Like Jerry said with the nose into a head wind even slower. I stopped traffic on the highway that crosses the approach to runway 17 at Graham by doing this. People always want to see a plane wreck. It's a little harder in the SC because of the longer wing, the Clipper has the same aileron with a shorter wing and fuselage. A real sweet slipping airplane. I'll be glad when the rebuild is done I'm going through withdrawl. Flew the Husky over the weekend to cope.

Steve,

With my first airplane , a PA-11 with a C-90, I used to come tight into airstrips, slipping " all the way", and making very short landings. Mostly this was not with any heavy loads, besides you couldn't carry them anyway in the 11. With my later PA-18 and the Bushmaster, I am not sure that I could do any better and I must admit that I do not use the slip anymore. Have to try next time I go out - flaps make you "lazy".

Hans