Fear and Loathing in Base to Final

[ussyorktown]

I am a low hour CTSW driver. When I am at about 61K going into base to final and turning left it is my instinct to left rudder too.
But, when I look down the bubble tells me that I should be pressing down the right rudder!
I've heard so much about stalling with cross controls on base to final.
What is up wit dis?

[zaitcev]

Short term, trust the ball and override your instinct.

Long term, get some practice with a shorter-coupled airplane. DC-3 works best, I heard, but basically any old taildragger. You'll see that it's the best to kick the rudder to make her roll and then return to coordination.

Note that if you are slow enough and the AoA is great enough, all the left-turning tendencies multiply and may be greater than the loss of coordination yaw. I only had something like an hour and a half in CTLS, and I do not remember what it does, but in some airplanes it's the case that you turn left with a bit of right rudder if slow. Except Yak-52, of course

[ussyorktown]

I get it. So when I'm so slow that I am getting my propeller to turn me to the left (like on take off) and I have to kick a little right rudder in as I go from base to final (if the ball tells me so).

[Jim Stewart]

My CT stalls at 35 knots indicated at flaps 30. I know it's no substitute for sloppy flying, but you're miles away from a stall at 60 knots. Develop a seat-of-the-pants feeling for where the ball is and always make sure that when you turn, the inside wing is lower than the outside.

What you're seeing is called top rudder. The best book in the world to really understand it is the classic "Stick and Rudder".

[fredg]

This is a little more complicated that it seems.

First, is the ball true? By this I mean, when the airplane is truly level with respect to the horizon, is the ball centered? Many CTsw airplanes (mine included) have less than perfect calibration of the ball. This issue is often covered in books on aircraft rigging. My ball is now true and it helps me fly the airplane.

Second, where is the rudder trim? If the rudder trim is already to the left, then you may need to press the right rudder pedal to neutralize the rudder when making a left turn at low speed. It seems like right rudder, but you may only be taking out some left trim. This is because the CT has a spring return to center the rudder rather than relying on aerodynamic forces.

Third, if you have a Dynon, the "ball" may lag a little bit. So, initially, it will seem like the airplane is in uncoordinated flight, but if held for a second (i.e., less right foot than you might think you need), it may clean up.

Fourth, a small additional consideration is the fact that the CT panel is not square to the long axis of the airplane. This makes the ball misbehave a bit in the direction you observe when turns are made in other than level flight. Given the fact that the panel is angled so that the outer portion is further from the front of the plane that the inner portion, pitching down without any change in bank or yaw will result in the ball deflecting to the right of the gage by gravity alone. A small effect, but still one that may contribute to the observed effect.

Finally, I have about 350 hrs in my 2006 CTsw. I had the same experience you described early in my time and it drove me crazy. I spent a lot of time at altitude simulating base to final turns and fine tuning my use of rudder. It helped a lot.

Good luck!

[fredg]

One more thing... You wrote " So when I'm so slow that I am getting my propeller to turn me to the left (like on take off) and I have to kick a little right rudder in as I go from base to final (if the ball tells me so)."

When taking off, high angle of attack and full engine power create a strong left turning tendency. When descending for landing these forces are weak and the airplane, with no rudder trim change, will have a right turning tendency and will need left rudder for coordinated flight.

I suggest the following drill - at altitude and with an instructor - configure the airplane to simulate take off climb. You should need right rudder input to counteract the left turning tendency resulting from p-factor, "torque", and the corkscrewing nature of the propeller slipstream. This is common in small airplanes.

Next, transition to straight and level cruise flight. If trimmed correctly, the airplane will need no rudder input from the pilot. That doesn't mean that the rudder is perfectly "neutral". The CTsw has rudder trim that will hold the rudder against the slipstream in a position configured by the pilot's use of the trim wheel. It means that the rudder is trimmed for coordinated flight in cruise configuration.

Then, pull all power as if to begin a descent for landing. The airplane will now have insufficient left rudder (or, equivalently, excessive right rudder set on the trim wheel) and will yaw to the right. This is because in level flight, the trim held sufficient right rudder to neutralize the left turning tendency caused by propeller thrust described above. You will likely have to maintain some left rudder through the entire landing sequence.

I find that good practice is to transition from full power (and right foot) to no power (and left foot). The CT is sensitive to yaw effects from power inputs. Practice at altitude until this becomes second nature to you and you will be glad you did.

Remember, have an instructor with you and practice at altitude, first. Finally, note that my comments reflect my personal experience in one CTsw airplane. They are for your intellectual consideration only and are not intended to be a substitute for flight training from a qualified instructor.

[drseti]

you're miles away from a stall at 60 knots.

That's true, Jim, when the wings are level. But put that plane into a 60 degree bank, with enough back pressure to hold altitude, and your load factor now increases to 2. This increases the stall speed significantly, so if you entered the turn in level flight at 60 knots, you just stalled!

I think the reason for many of the fatal stall/spin accidents on the base to final turn is that pilots overshoot, then overbank trying to get back on the centerline, and then haul back on the stick when they find themselves low. A bad situation to get oneself in. I emphasize to my primary students that, if you roll out on final and are not reasonably well lined up with the runway, an automatic go-around is called for.

[Jim Stewart]

Clearly a 60 degree bank on base to final would be wrong and I'm sorry if it looked like I was suggesting that that would be acceptable. Likewise if he pulls back on the stick, he won't be maintaining 60 knots. I was assuming from his description a reasonable flight path and turns.

[RyanShort1]

Does the CT have some very momentary adverse yaw going on there that you are over-reacting to?

Ryan

[drseti]

Clearly a 60 degree bank on base to final would be wrong

Of course, Jim, and I know you realize that (as does everyone here). And yet, these kinds of accidents still happen every year! I think the big killer is not lack of knowledge, but distraction.

[Jack Tyler]

Yourktown, Fred's given you two excellent replies that illustrate the interaction of multiple variables (both mechanical and skill related) that affect the turn in question.

But don't miss out on another key learning that's part of this discussion, the lead-in being:
"My CT stalls at 35 knots indicated at flaps 30.... you're miles away from a stall at 60 knots."

Paul's commented on this in one context (your base to final turn) but the implication for safe & skilled flying is much broader than that. If you aren't really sure what I'm referring to (the relevance of AOA), this would be a great topic to dig into a bit. Perhaps if you're CT is Dynon equipped, you have an AOA digital icon on the display.

In the POH's associated with 'conventional' (Part 23) a/c, there is a required diagram that allows the pilot to accurately determine what stall speed is for a given angle of bank. Does the CT's POH has this diagram? If you aren't sure, you might want to take a look.

Best wishes on your continued flying and learning.

[drseti]

Develop a seat-of-the-pants feeling for where the ball is

Jim's right on target here, guys and gals. The ball is merely confirming what your butt cheeks are telling you as they slide across the seat. If you can learn to feel the G-loads, you can anticipate lack of coordination well before the ball tells you you're slipping or skidding in the turn. Kinesthetic feedback is really great in these light planes.

[drseti]

In the POH's associated with 'conventional' (Part 23) a/c, there is a required diagram that allows the pilot to accurately determine what stall speed is for a given angle of bank. Does the CT's POH has this diagram?

I can't answer this one, Jack, since I've never seen the CT's AOI. But, I would guess not. I've never seen that diagram in the AOI for any LSA. Nor have I seen the one that shows how stall speed varies with gross weight. Sure would be nice if they added these.

Acronym alert: For those confused by the alphabet soup, AOI (Aircraft Operating Instructions) is merely the POH (Pilot's Operating Handbook) for an LSA (Light Sport Aircraft). No matter what you call it, it serves the role of an AFM (Approved Flight Manual).

[zaitcev]

There is no infortmation on accelerated stalls in AOI of CTLS. However, the airplane is equipped with an AoA-sensing pitot probe, which helps performing maximum performance turns, should you ever wish it. Remos GX has the same device.

[designrs]

Great thread!

Solo student here, never flew a CT, but I always drop the nose a bit automatically for any turn in the pattern. More aggressive turn then more aggressive pitch down. It kicks in as a nice automatic safety technique for both airspeed and AOA when multi-tasking and dealing with traffic in the pattern.

Instructor comments?