Stall in a turn

[raytoews]

We have had fatal accidents in Canada in the last few weeks. They all look like stall spin accidents. WTF.

[Frank Giger]

You don't need a ball for VFR flight. If you pay attention, your butt will tell you everything you need to know.

Best of luck,

Wes

This is dependent on the aircraft as much as it is the pilot.

In the Champ, any slip at all was easy to feel...and if someone was behind me, doubly so.

In my Nieuport, it can be subtle. With the flying tail (no vertical stab), the infamous "sneaky slip" is easy to get into. She just naturally tends to yaw if one isn't really on top of it. Worse, it's not much.

So here's the setup for danger if one doesn't check the ball from time to time in an aircraft with a flying rudder:

Rudder comes off center a little (in the case of VW driven aircraft, to the left). The plane will slowly, bit by bit, begin to roll to the left. It's not sudden, it's very gradual. The pilot arrests this roll with aileron input (if he's not aware of the quirk) to the right.

Again, it's subtle, but it can build from there, and pretty soon the pilot is cross-controlled, thinking he's in something other than a slip.

Dick Starks of the KC Dawn Patrol (who is guilty of many a 7/8ths scale Nieuport 11 being built) sums it up this way:

A bunch of us were sitting around the table in the hangar a few days ago solving the problems of the world and, I might add, doing a heck of a job when the subjects of aircraft instruments and the latest Victoria's Secret Catalog came up . The question was asked as to what we think is the most important instrument in our Nieuport panels and the unanimous choice was..

The skid and slip ball.

Why? We hear you ask... It doesn't even have any gears of actual moving parts.. It's simple... The Nieuport (except for the 24 and it's a tiny little thing.) DOES NOT HAVE A BUILT-IN VERTICAL FIN FOR INHERENT DIRECTIONAL STABILITY. All its got is a full flying rudder which,since it's not fixed and just kinda floats in place, gives you no built-in directional stability at all. What do that mean? It means that if you relax pressure on the rudder bar while flying, the plane can go into a skid or slip without you knowing it. In fact, torque will automagically do it for you if you're not on the bar and ON THE BALL (so to speak.) We all swear that we've been able to hear that "click" when we really get outta whack in a turn and bury the ball on one side or the other of the tube. If you don't pay CONSTANT ATTENTION to that little booger... It'll quickly and without warning, sneak up and bite you right in the ass.

Mark Pierce does a heck of a demo in his air show act showing how the Nieuport can almost be flown sideways with very little rudder input... Or, another way of putting it would be to say.. With very little pilot attention to the ball. We call it the "Pierce Horizontal Knife Edge." While he's doing it on purpose, a little inattention on your part can have it happen to you NOT ON PURPOSE and at a low altitude at low air speed... You ain't gonna like the outcome!! What happens is that as the plane gets more and more screwed up, you start to feed in aileron to try and keep things "feeling right." Then you suddenly end up with a cross-control stall/spin and THAT'S A REAL BAD THING. (I've done this I might add, in my C-120, on purpose, with my instructor on board, at altitude, and when it finally happens, it's a real shorts-staining shocker.)

There's a whole flock of Nieuports getting built out there and a lot of them are going to be flying soon. We can't emphasize enough the importance of that skid/slip ball.

SO....PAY CLOSE ATTENTION TO THAT MOMMA...
IT'S IMPORTANT.
(Or, as Dick Lemons likes to say,)
"You fly with one eye on the ball,
and the other eye on the ball. "
(Or, In other words)
Watch The Damn Ball!!!
(or, as my sainted flight instructor used to yell in my ear.."
"STEP ON THE BALL!!!. STEP ON THE BALL!!!"
(Thus endeth the lesson.)
Now... There is something you can do to help

All of us now have a small length of bungee going from a small sailboat jam cleat attached at the bottom of station 117 on the starboard side going to the extreme starboard end of the rudder bar. After getting in the air, we reach down and adjust the tension of the bungee to attempt to hold the rudder in an approximation of "feet off" so we can fly without the constant attention needed to the ball. It works great BUT any change in rpm will make you have to change the tension on the bungee.

Still... all in all... it's a great help.

(emphasis mine)

http://www.dawnpatrol.org/questions.htm

Now, then, I don't have a rudder bar, but independent pedals, so the bungee trim fix won't work for me. I just have to scan the ball....and yes, I've experienced exactly what Mr. Starks is writing about - but I was forewarned thanks to him and didn't proceed to the spin/stall.

[Bill Greenwood]

I took some acro lessons for legendary pilot Duane Cole many years ago. If you have seen his engine out gliding descent while inverted and doing acro its impressive and he didnt rely on a screaming annoucer nor a whining cavitating prop nor a jet engine blast to make his act. I remember one moment vividly, I was sitting in the rear seat of a Decathlon and flying the landing approach and I asked Duane to lean over to the right so I could see past his shoulder to see the ball on the instrument panel. Duane was a man of strong opinions and sometime strong expressions of those opinions and he left no doubt that I should be able to feel what the plane was doing without having to see the ball. "You dont need that thing, its just something someone invented so they could sell you something." I didnt dispute this but I did lift myself up from the seat enough so I could take a glance at the ball and was reassured to find it was in the middle, and I didnt worry about it anymore. He probably wasnt too good with a smart phone or an ipad, but he could fly.

[Frank Giger]

Well, Bill, I won't disagree, especially when landing.

While I put little flying videos out, the real reason for filming is because I never look at the instruments when taking off or landing, and it's a great troubleshooting tool.

Oddly enough, even though I tend to cruise around a bit uncoordinated, on final that ball just seems to find it's way to the center and stick there the whole way down.

[Ron Blum]

Frank, are you part of the KC Dawn Patrol? If so, when do y’all normally get together to fly? I’ll find time to come up and see the antics. Thanks, (just an average) Ron

[Frank Giger]

Nope, they're just outside of Kansas City, MO, and I'm down here in Alabama.

However, I had a chance to hang out at their aerodrome for a full day, and then for a couple more at the Gardner, KS, airshow (which is now defunct).

I used the very clever method of looking up Dick Starks in the phone book and calling him, asking if they were going to be out at their airfield that weekend. They had planned on it anyway, and I got the royal treatment....hot dogs, coffee, education, flying chase plane to Nieuports in a Champ, etc.

The one of their group you really want to talk to (now that Tom has passed), is Sharon Starks. Not only is she an expert builder, but an Ace pilot, and able to speak in small sentences to explain stuff.

[Ron Blum]

The one of their group you really want to talk to ... and able to speak in small sentences to explain stuff.

Awesome. Thanks!

I’ve heard about it the lack of directional stability in WWI airplanes. Dick Curtis has a Fokker DR-1 here in Wichita, and he says that it’s happy flying sideways. This might be what took many of our early fighter pilots. It would be tempting to get “guns on” by yawing the nose on target.

[Bob Dingley]

This is a great topic. So far, no one has answered my question in #24. "In a shallow COORDINATED TURN, slowing to an accelerated stall, why does the outside wing drop?"
This was shown to me about hour four or five by my instructor, Clyde Davis. Clyde spent WW2 teaching primary to Fleet Air Arm pilots in Stearmans somewhere in Georgia. The maneuver likely was brought over from the UK. Clyde could be a nag if an aileron was sloppily displaced during the maneuver. It works the same in a PA-22 with interconnected controls BTW.

In post #31, we were offered a very good video by Wayne Hadley on the evils of miss using aileron in turns. This was apples and oranges. Not the same thing. It is my hope that someone smarter than me would answer the question: why does the aircraft roll out of the turning stall, banked in the opposite direction?

Bob
EAA 29005
ATP
FAA Master Pilot

[rwanttaja]

This is a great topic. So far, no one has answered my question in #24. "In a shallow COORDINATED TURN, slowing to an accelerated stall, why does the outside wing drop?"

My guess: Due to the dihedral of the wing, the lift vector of the outside wing is at a less advantageous angle to the gravity vector. Thus a very slight amount of additional aileron is needed, and thus it stalls first.

Ron "Space Engineer, not Aero Engineer" Wanttaja

[Ron Blum]

This is a great topic. So far, no one has answered my question in #24. "In a shallow COORDINATED TURN, slowing to an accelerated stall, why does the outside wing drop?" ... It is my hope that someone smarter than me would answer the question: why does the aircraft roll out of the turning stall, banked in the opposite direction?

Bob: I tried to answer your question in paragraph 3 of my reply #36. In a turn there has to be some (although slight) down aileron on the up wing side (and/or up aileron on the down wing side), otherwise (if the controls were let go) the airplane would have a tendency to return to wings level flight ... due to the inherent lateral stability of the airplane. As a result, the up wing stalls first. In addition to this wing now having less lift than the down wing (which is still flying), it also has more drag because it is stalled. Asymmetrical lift (now greater on the down wing) and asymmetric drag (higher on the up wing) will turn the airplane to the direction opposite the original turning direction.

Many people think that a whole (right or left) wing is either lifting or not lifting instantly. This is not true. The stalled or separated portion of the wing will progressively flow/move with changes in angle of attack (both aircraft and local). Even a completely stalled wing is producing (roughly) 50% CL-max.

BTW, yes, I am a degreed Aero/Astro Engineer with 30+ years in the business, but that doesn’t make me smarter than you or anyone else. I am still learning. Please keep asking great questions. I love the challenge.

Ron “solutions@blueontop.com” Blum