Slip With Flaps

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Rich
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Re: Slip With Flaps

Post by Rich »

Soareyes wrote: Sun Oct 02, 2022 10:55 am 1. It's hard (but not impossible) to stall with the nose pointed down
2. a slip is not a skid.
#1 is absolutely untrue. This is a dangerous myth that is often at the root of stall/spin during turn to final.
#2 is only partly true. Aerodynamically they are identical. The difference is that, in a slip, the break to a spin would be over the top and is therefore more easily recoverable.
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dant
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Re: Slip With Flaps

Post by dant »

#1 is absolutely untrue. This is a dangerous myth that is often at the root of stall/spin during turn to final.
I often idly wonder about this. You certainly can get a high AOA while pointed down, but I do I wonder how many of such spins in actuality have the nose pointed down vs up.
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Soareyes
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Re: Slip With Flaps

Post by Soareyes »

Rich, Thanks for the feedback.

Responding to your comments:

1. Yep, you got me on that one. Of course you can stall with the nose pointed down. You can stall at any airspeed. You can stall with the nose pointed up, down and in a 90 degree bank. You can stall inverted at the top of a loop and the stall breaks upward. You can cause an accelerated stall with the nose pointed straight down by pulling too hard.

My comment that it is hard to stall with the nose pointed down was not necessary to make the point anyway, I should have left it out. But you won't spin without a stall however likely or unlikely it is in the descending phase of flight. It was hoped that this would be reassuring to the OP.

Slips and spins are a different matter.

2. Slips and skids, as the terms are usually used in practice, have quite different meanings. Limiting the discussion to the risk of spinning, Boldmethod does a good job with the subject, as usual: "Why Skids Are More Dangerous Than Slips"

https://www.boldmethod.com/learn-to-fly ... kid-stall/

Regardless, I still maintain that the risk of a spin from a slipping with full flaps is small.
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Rich
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Re: Slip With Flaps

Post by Rich »

Too many pilots literally believe the statement that you can’t stall with the nose below the horizon. I once had a guy I was checking out in a Bonanza execute an incomplete recovery from a plain old straight ahead power off, flaps/gear up stall. The plane entered a secondary stall with the nose slightly down. He then pulls the yoke all the way back and the nose drops further. We’re sitting in a nice stable deep stall plummeting toward the earth and he’s frozen, literally asking “what do I do?” I push the yoke forward and it recovers quite nicely. He asks what that was and i tell him he re-stalled it. He states with complete bewilderment “But the nose was below the Horizon.” This incident is why I never let statements like this pass. I’m convinced he’d have held that stick back until he hit the ground, wondering what happened.

The turn to final is the perfect situation for this to happen in an overshoot. There have been numerous fatal accidents in this maneuver. Skid at this point and pull back on the yoke and it’s all over.

When I was working on my CFI, among other things we’d intentionally enter a spin from a slip. But it would rotate toward level, so you could either keep it developing or arrest it before it rolled over and fly out of it. But the position of the yoke/stick is really the best indicator of whether you are at risk for a stall and hence a spin.
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Re: Slip With Flaps

Post by CFIDave »

The ability to conduct forward slips in a DA40 (at any flap setting) is something that every DA40 pilot should have in their "toolbox."

Where this is particularly useful is when using a DA40 to get your single-engine Commercial rating -- when practicing the required 180-degree power-off spot landing. With zero thrust, you have 3 tools to adjust where you're going to spot land:
1. Where/when to turn towards the runway (i.e., adjusting your path)
2. Where/when to put in full flaps
3. Use of a forward slip

For the DA40, the easiest way to perform this maneuver is to come in high and fast with excess energy, and then use a forward slip (as needed to dissipate energy) when on short final, to hit your desired spot on the runway.

For DA40 pilots NOT working towards their Commercial rating, this maneuver with use of a forward slip is an excellent skill to have if you ever lose your engine. It'll give you greater confidence that you can put the plane down within a small landing area.
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Re: Slip With Flaps

Post by Lou »

erchegyia wrote: Fri Sep 30, 2022 4:44 pm couldn't a slip with full flaps negatively affect the airflow over the control surfaces resulting in the risk of unintended spin?
I believe a big distinction is that Cessna stabilizer and elevators are located below the trailing edge and closer to the wing “wake” and therefore more likely to suffer blanketing. T-tails have a big advantage here because they fly in undisturbed air, although they lack control authority at very low speeds (I would say under about 25 kts) and can’t use propwash to compensate. There was some debate I read once about whether a T-tail could be blanketed in a very deep stall. I don’t know if that is a theoretical debate or whether it is based on experience. (I learned this from aerodynamics articles written by Andy Lennon in model airplane magazines).

I do forward and side slips with full flaps all the time - often for fun and handling practice - and have never had the slightest issue with power or controllability.
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