"I was taught..."

[FastEddieB]

I Opposite aileron during hammerheads is done purely to control engine torque. It's also done at zero AOA, and is not a stall, so aileron use during stalls and hammerheads is apples/oranges.

It's been forever, but...

I thought that without opposite aileron the outer wing, going through the air faster, would tend to roll you slightly towards inverted as the nose fell through.

Was that incorrect?

 

[Stevel]

I hope this doesn't spark more controversy, but the ball in center coordinated 'Dutch roll' will cause small S-turns moving the nose back and forth rather than keep the nose on a point. The nose on point 'Dutch roll' requires x-controlling and is definitely not a ball in center exercise. The ball in center exercise is the best for learning to fly the airplane realistically. The nose on point dutch roll is a pure 'helluvit' exercise in a different type of precision, more relevant to aerobatic pilots. FYI- I will flame anyone who tries to claim the x-controlled nose on point dutch roll helps with x-wind technique.

THAT'S WHAT I ALWAYS THOUGHT!

It seemed like what was said/taught had NOTHING to do with what was actually being demonstrated, so I had no clue WTF he really wanted me to do. Am I supposed to hold it on a point OR stay coordinated? Everything else he had already taught me told me that I had to choose one OR the other. I wasn't supposed to be able to do both, and he sure wasn't demonstrating both at once, but those were the words coming out of his mouth when he was telling ME what he wanted ME to do.

 

[denverpilot]

I hope this doesn't spark more controversy, but the ball in center coordinated 'Dutch roll' will cause small S-turns moving the nose back and forth rather than keep the nose on a point. The nose on point 'Dutch roll' requires x-controlling and is definitely not a ball in center exercise. The ball in center exercise is the best for learning to fly the airplane realistically. The nose on point dutch roll is a pure 'helluvit' exercise in a different type of precision, more relevant to aerobatic pilots. FYI- I will flame anyone who tries to claim the x-controlled nose on point dutch roll helps with x-wind technique.

All true and there are both options. My point was that folks sometimes need a reference for "how hard to push" and either maneuver will give you large muscle hints in just a couple minutes of doing them that'll show ya how a particular airplane's control forces are and a feel for that airplane's ratio of forces between rudder and aileron.

Obviously somewhat limited to flights by oneself so you don't make friends and family hurl. Haha. But a quick and dirty way to feel out a new type and you can do both types slow and gentle and have that "feel" of the inter operating aileron and rudder pressure needed in just three or four banks...

Or just do them for fun. Switching between types without stopping will mess with your head.

 

[RoscoeT]

It's been forever, but...

I thought that without opposite aileron the outer wing, going through the air faster, would tend to roll you slightly towards inverted as the nose fell through.

Was that incorrect?

Hammerheads are intended to be done with the airplane in a perfectly vertical attitude throughout. Perfectly vertical means the zero lift axis (zero G, zero AOA). If both wings are at zero AOA during the pivot, the faster moving outer wing creates the same amount of lift as the inside wing - zero. Gliders do hammerheads with none of this rolling force requiring aileron to control. It's engine torque only, unless you have some positive AOA during the pivot, in which case what you describe could cause a small amount of additional torquing. The higher the power/weight ratio the more noticeable the torque effect. Running a metal prop vs. a light wood or composite prop also makes a difference in the amount of torque effect.

 

[FastEddieB]

Thanks for the explanation, and I won't argue.

I will, however, say that my misconception appears to be fairly common.

Googling "hammerhead stall" produced this from 2 out of 3 top hits:

"First, as the aircraft pivots in an arc to the left, the right wing is on the outside of the arc and is traveling faster than the left wing – which means it will be producing more lift than the left wing and will therefore try to roll you onto your back. SO… when you hammer that left rudder, feed in a right aileron to counter this tendency."

...and...

"Another problem in this maneuver is that higher lift from the faster moving outside wing will roll the airplane to the left. Most pilots find holding forward right stick necessary throughout the pivot."

Like I said, if wrong it appears to be a fairly common misconception.

 

[Henning]

Not that high of an AOA....being on the threshold of a stall is not what I'm talking about. I never get that slow in the ag plane. That just begs for an oh **** moment way to close to the ground.

In the Ag Cat the top of my turns would be really slow. The thing about the Cat is it likes working steep and tight. By the time I'm slow, I'm already unloading the wing and stall & spin aren't concerns. That's why you can outwork a 402 with a 1340 Cat, and on smaller fields and rice work, I could outwork a 502.

 

[RoscoeT]

Thanks for the explanation, and I won't argue.

I will, however, say that my misconception appears to be fairly common.

Googling "hammerhead stall" produced this from 2 out of 3 top hits:

"First, as the aircraft pivots in an arc to the left, the right wing is on the outside of the arc and is traveling faster than the left wing – which means it will be producing more lift than the left wing and will therefore try to roll you onto your back. SO… when you hammer that left rudder, feed in a right aileron to counter this tendency."

...and...

"Another problem in this maneuver is that higher lift from the faster moving outside wing will roll the airplane to the left. Most pilots find holding forward right stick necessary throughout the pivot."

Like I said, if wrong it appears to be a fairly common misconception.

It's a common misconception, even repeated in a popular aerobatic book. It stems from thinking in terms of yaw/roll coupling. Well, that scenario is always thought of in terms of positive G upright flight. For a hammerhead, where the objective is to be at zero AOA/zero G, why would this apply? If you're aiming for zero G, you're just as likely to end up slightly on the negative G side as the positive G side. Under negative G, yaw/roll coupling would cause a roll in the opposite direction, so during an attempted zero G hammer, you'd be just as likely to produce roll reaction to the right as you would to the left if you're considering yaw/roll coupling. Engine torque is the real reason you use aileron, unless you really are in a significantly positive G attitude when the pivot is started.

Also, the forward stick during a hammerhead is only to control the gyroscopic precession from the prop, which attempts to pitch the nose away from the wheels as the airplane is pivoting. This effect is also greatly reduced with a light weight prop.

Gliders don't need aileron during a proper zero G hammerhead (no propeller torque). Glider hammer at 2:10 in the video below. No aileron use. If this 'faster wing producing more lift and roll' theory was real, gliders with their long wings would be especially susceptible.

http://www.youtube.com/watch?v=nNuBw8Isihk

 

[Tarheelpilot]

In the Ag Cat the top of my turns would be really slow. The thing about the Cat is it likes working steep and tight. By the time I'm slow, I'm already unloading the wing and stall & spin aren't concerns. That's why you can outwork a 402 with a 1340 Cat, and on smaller fields and rice work, I could outwork a 502.

Yep. The air tractors will fall out of the sky at speeds very comfortable in the cat. the thrushes seem to be somewhere in between. I found in the thrush/AT comparison the thrush can stay tighter to the field but is slower doing it so the time invested in each turn is not that much different between the two.....generally. They both have their pros and cons, just depends on the job.

I have just enough time in the cat to discover they made them for someone way smaller than me and that I don't like having a wing sitting in my field of vision.