Thanks Jimmy !

Ed's link on the spirals article wouldn't download for me, but I got to thinking about the Cherokee that Fred Weick also designed. It was very difficult to stall in any configuration, but impossible in the accelerated stall practice until the bank was increased. And we instructors had to find a bank sufficiently steep to stall the wing while not so steep that graveyard spiral was entered. Because the elevator travel was not limited, as on the Ercoupe, enough elevator could be pulled to spiral when the banked wing would no longer maintain altitude. I think the airplane spiraled at that bank angle because enough air was being blasted across the short wing to keep it from stalling but not enough to maintain altitude.

I remember the Cherokee 235 accident in the high Colorado mountains that killed an entire family. The FAA called it a stall spin accident. I bet Ed is right on that one being a spiral accident. I commented on this forum that he had adequate vertical space available to allow the nose to go down as designed for safety in the turn back. In light of what Ed is saying, I would again have to emphasize that we don't pull back on the yoke except to take extreme nose down tuck out of a very steep turn. I expect he was making a very shallow turn but was pulling back hard trying to maintain altitude. With his weight and density altitude problems, lots of back pressure was increasing his rate of turn but going to ground so quickly in the spiral probably caused upset type LOC.

In most airplanes, back pressure on the elevator increases rate of turn until it doesn't because we stall. In this airplane, maybe we enter the graveyard spiral instead.

I agree Ed's spiral point may have been overlooked in many stall spin designated accidents, but in some of the video's you can see the wing go over the top (slip spin) or drop (skid spin).

Jim,

This might be a better link to the Spins & Spirals article in Flying.

https://www.planeandpilotmag.com/articl ... r-spirals/

Best,

Tom

I haven't had much problem with pilots trying to bring the nose back up before leveling the wing, but I have emphasized the need and the spiral problem if not done. That is because of the increase in airspeed as we are coming onto target. The 180 course reversal or return to target is going to be a steeply banked turn. After the pull up wings level, if we have zoom reserve in the form of airspeed, we need to bank more than necessary as we start the turn. We let the nose go down naturally and past 45 degrees of bank the rudder really helps get the nose down. We want to remove excess nose down pitch (the tuck is greater the slower we get in the zoom up and the steeper the bank) here while slow as well. Ed's slow airspeed spiral problem is at faster than we are here and with significant back pressure (see gs on his chart.) And we are pushing the nose around with rudder. Getting to where the dihedral increases bank is not a problem because we stay at near 1 g even if we take some of this nose tuck out. We have to stay with the rudder, however. We push the nose around until on target or we level the wing to bail out of the energy management turn.

The small airplanes we fly have pretty slow Vne so we have to get around while slow and prevent too much pitch down. And we need to level the wing before pull up whether we have acquired target laterally and dive angle. In aerial gunnery, we want as much wings level gun target time as possible. Cobras start around 40 knots and Vne at 190. Jet fighter bombers have very high Vne so target fixation is the greater problem.

Nose tuck problem is not ten degrees pitch down, it is greater than 30 degrees pitch down. We do not have a stall problem. We do not have a skid problem. The only problem would be a slip problem...not enough rudder in the direction of bank. We need to push the nose around until on target. We are not doing 720s here.

Jim wrote, “ Nose tuck problem is not ten degrees pitch down, it is greater than 30 degrees pitch down. We do not have a stall problem. We do not have a skid problem. The only problem would be a slip problem...not enough rudder in the direction of bank. We need to push the nose around until on target. We are not doing 720s here.”

Curious, just what causes the nose tuck? How do you best limit it to less than 30:degrees when you notice it building? Thanks

Best,

Tommy

Dynamic neutral stability causes the nose to go down when the elevator is released after slowing more than trimmed or turning. Pitch up slowing, wings level or in a bank, causes less relative wind over the camber of the wing that pushes down off the trailing edge causing lift. Bank causes less percentage of the wing lift to be deployed against the weight of the airplane. Together, zoom up to slow down and bank to turn, causes the nose to go down replacing lost relative wind and lost percentage of lift. This makes tractor airplanes extremely safe.

The problem with the nose being pitched down is both the amount of pitch down and the time the nose is pitched down. The amount of pitch down, sans pulling back on the stick, is greater the slower we are and the greater the bank. Since we don't need to return to the same relative wind as before the pull up to start the energy management turn quickly, we can (ONCE the NOSE GOES BELOW the HORIZON) pull some slack but not a lot of pressure out of the elevator to prevent the nose from going past 15 degrees or so down. This will delay gaining near Vne until on target. Concerning the time the nose is pitched down, the problem starts with poor rudder usage. First we lose rate of turn and increase time the nose is down, actually first yawing the wrong way, if we do not lead rudder. Second we lose rate of turn and increase time the nose is down if we slip at any time during the turn. And finally we lose rate of turn and increase the time the nose is down if we do not continue pushing the nose around with rudder in the direction of the bank throughout the turn. In shallow level turns, we relax rudder pressure and aileron pressure when the bank is established. In energy management turns of greater than 45 degrees of bank, wing dihedral will increase bank. We do not fight that increase in bank, but allow the extra rate of turn along with extra rudder in the direction of bank. Fighting that bank increase will delay getting on target an thus increase the time the nose is pitched down.

Shallow energy management turns are completed, with proper ruder lead and usage, before there is much nose tuck. There is far less pitch up, much greater airspeed throughout, and little difference than a level turn except we still have to anticipate the slight pitch up before the bank and we allow the nose to pitch down naturally. In steep energy management turns, while not acrobatic requiring full deflection of the controls, time of nose down is the essence given limited time available and Vne. Poor rudder usage, both not leading rudder and not pushing the nose around throughout, will result in possibly accelerating to Vne before the wing is rolled level prior to pull up over the target. The wing must be leveled prior to pull up to avoid Ed's spiral danger. If we are not on target before near Vne, we have to level the wing and bail out of the energy management turn.

In the process of teaching Commercial pilots Ag turns to a crop row 36 feet horizontal from where we zoomed up out of the field, pilots who have not mastered proper rudder usage, pilots who do not push the nose around, will have to bail every time. Moving from where they are, having to level the wing prior to getting the nose around onto target, to where they want to be, getting the nose around onto target, is a process that involves the instructor yelling, "lead rudder" and "let the nose go down," and "push the nose around," a lot. A lot. lot, lot, lot, lot, lot. They are Commercial pilots. They know how to fly. They just mostly don't know how to use the rudder properly.

And finally these Commercial pilots could just pull back on the stick in the turn, pull gs, like Tom Cruise in "Top Gun" until the airplane stalled. That would get the nose around onto target timely...in a spin. In this spin i guarantee the low wing would go over the top because of the slip. So actually the nose would go back the other way to get around onto target. A real mess.

I am not trying to teach crop dusters here, Tommy. If we keep the targets away from us a bit and are able to get onto target with less than 50 degree of bank or so, we will have very controllable nose tuck. We can either just relax back pressure completely or just be sure the nose is below the horizon when we use a small amount of back pressure. In the steep return to target, 180 reversal, canyon turn, gun run, crop duster swath or whatever, the stick will be light when we pull back with the nose down because we first pitched up to almost stall. When we make shallow energy management turns the stick pressure will be near what if would be if we turned level. Or just leave it alone in normal turns around the pattern, let the nose go down, totally prevent stall, totally prevent fatalities. I don't think the passengers will mind.

Hey Contact, the Stinson has the same principle that the Ercoupe used to keep the wing from stalling, though by limiting elevator travel (without flaps). I’m sure you knew that, but it does work the same. Would you mind touching on throttle usage throughout the turn. Just wondering if reducing it would hinder the turn yet help with the approach to Vne. Thanks

In the normal descent we reduce throttle and use elevator to set a pitch attitude reduce airspeed until we sink or mush. Now we can use the throttle as a rate of descent and glide angle control. Since we don't want to land on the target, we don't do that in the energy management turn. Yes, reduction of throttle would increase time on target if and only if we limited pitch down attitude to near level. And at the bottom of the descent we would have given away the zoom reserve both potential in gravity and kinetic in airspeed. This is a dangerous place to be in maneuvering flight, without money in the bank or money in our pocket.

So what we end up with in the cruise throttle, cruise trim, energy management turn is the law of the roller coaster. We get to use the extra altitude of the zoom up to slow down to get the best rate of turn for bank and we get to use the return of zoom reserve in the form of airspeed, kinetic energy. Rudder usage, both lead rudder and push the nose around throughout, is the trick to get on target before Vne.

Let's go back to Wolfgang's roller coaster. In Butch Washtock's and MTV's slow level turns in the bathtub type mountains, zoom reserve in the form of airspeed may be dangerous. Getting the altitude wings level to slow to begin the turn there would be fine. It is the return to high airspeed in the bottom of the turn before pull up that would be dangerous.

So they put themselves in a somewhat dangerous maneuvering flight situation of having no money in the bank and no money in their pocket. Those are tough mountains with maze like slots that require this, so we do what we must. It sure makes Butch's "rudder pulls aileron" emphasis very important. At slow airspeed the ailerons are not effective but the rudder and elevator still get prop blast.

In the Continental US Rockies and Appalachian mountains, we have steps, alluvial plains, volcanic, fold and fault, moderately steep ridge and valley systems that constrict only going up to the pass. Down drainage is almost always evident and will lead either to the Atlantic, the Gulf of Mexico, the Gulf of Baja, or the Pacific. There is no reason here, except in true canyons that could be overflown to begin with, to give up zoom reserve both in the form of airspeed and in the form of altitude. Starting the energy management turn, we trade airspeed for altitude in order to store money in the bank and to increase the rate of turn with slower airspeed. However, returning to very low altitude in the bottom of the dive out of the turn, we regain zoom reserve in the form of airspeed for maximum maneuverability near the ground. Energy management turns make use of money in the bank and money in our pockets. Win, win.

Looking at Ed spiral theory in accidents called stall spin, the accelerated stall maneuver in the ACS can easily become an accelerated spiral with the low powered airplanes we fly. Consider the Ercoupe. which won't stall, and the Cherokee, which is hard to stall with cruise power. The Ercoupe will enter a spiral down with the limited elevator control. The Cherokee, with its short wings getting prop blast on a good percentage of the wing, may refuse to stall and just enter a spiral instead. DA and limited engine thrust could be a factor.

If we are dead set on a level turn with no altitude loss, accelerated stall or graveyard spiral will result from the strong armed attempt to use elevator to increase bank to miss something like the other canyon wall. We need to either slow down and pull aileron with rudder using Mike and Butch's technique or if you are keeping some money (kinetic energy airspeed) in your pocket, pitch up wings level to slow down while gaining some money in the bank (potential energy of altitude,) and then turn at any bank while allowing the nose to go down and regain airspeed in the turn.

If at high DA and already slow to maintain altitude, just turn at any bank while allowing the nose to go down and regain maneuvering airspeed.

I copied Ed's long presentation over to the cognitive awareness thread and I will go over how the energy management turn could contribute Sunday with my fortnight original post.