Piper vs Cessna steering

BigBadLou

BigBadLou

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This might sound like a silly question to some but since I have owned only two airplanes so far, I don't have much expertise in how others do it.
So I resort to asking the experts (and trolls) here.
In my old Piper, the nose wheel steering was pretty tightly linked to the rudder pedals so it was easy to steer (you depress a pedal and the airplane turns as you expect it to).
In my newer Cessna, the nose wheel steering is very loosely linked to the rudder pedals. If feels almost like somebody used just bungee cords. It then requires differential braking to make the airplane taxi where you need it to taxi. That, of course, is effective but less efficient. And while flying other Cessna's out there, the steering felt pretty much the same between all of them.

So I guess my brain is producing multiple questions here:
1. Why did Cessna engineers design the linkage this loose? (IOW: what might be the secret benefit of bad steering?)
2. How did they actually implement loose steering? (of course not bungee cords but maybe springs?)
3. How do people normally deal with the horrible shimmy this can produce on taxi?

Or am I just looking too deep? Will I just hear "that's how it's been the past 50 years, get used to it"?

Thanks in advance for any meaningful and useful responses.
 
Every airplane has a different steering feel. It is just one of those things to get used to when transitioning to a new type.
 
I don't put up with shimmy on Cessna. Never have had to change the nose steering bungee to fix it.
 
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Thinking back trike pipers have always been a little tighter compared to trike cessnas, never enough to really cause me to think too much about it though.

As for the shimmy, unless you're taxing super fast it shouldn't shimmy.
 
The nosewheel steering on all my Pipers, including my current Aztec sounds more like your Cessna description.

The rudder pedal steering on a nosewheel aircraft cannot be too tightly linked. Right after the nosewheel touches down the rudder is still being used to steer the airplane so there has to be some "freeplay" between the rudder pedals and the nosewheel or you're gonna be trying to steer with both ends of the airplane at the same time. :)

You should not have a shimmy, and that should be checked. It could be the shimmy dampener, not the pedal to nosewheel linkage that is the issue.
 
bnt83 said:
I don't put up with shimmy on Cessna. Never have had to change the nose steering bungee to fix it.
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My book says service the shimmy dampener every 100hrs, which is around the point where I notice a landing shimmy. Never had one during taxi, I think I'd be looking for another cause if I did.
 
thomasdr72 said:
My book says service the shimmy dampener every 100hrs, which is around the point where I notice a landing shimmy. Never had one during taxi, I think I'd be looking for another cause if I did.
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I know of a Cessna 177 that was pranged on the front (all of the 177s have been at some point) and they did everything they could think of before they brought it to me. I not only did I fix it but also would up inducing it again a few years later. I had just pulled the bearing and repacked them at annual when I discovered that even though the axle was tight, it needs to be tighter because she simmyed like a *****. Can't recall if they replaced the nose fork when they replaced the firewall after a botch landing, long before I ever saw that airplane.
 
There are bungees (springs inside tubes) in the Cessna steering gear. You need to see if they are broken.
 
thomasdr72 said:
My book says service the shimmy dampener every 100hrs, which is around the point where I notice a landing shimmy. Never had one during taxi, I think I'd be looking for another cause if I did.
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The 150 steering collar was really loose, replacing the torque link bushings couldn't stop that from shimmy. A $15 shim did tho.
 
On landing, also depends on how you land and what speeds you allow the nose wheel to be on the ground.
 
Norman said:
There are bungees (springs inside tubes) in the Cessna steering gear.
Click to expand...

If steering is direct as on earlier Cherokees, Tri-Pacers, etc., then the nosewheel will turn in flight and be a rudder in the front of the airplane, like so ...

pa-28-180_1970_slip.jpg


That in itself is not a problem, unless you're landing in a crosswind. For example in a crosswind from the left, on touchdown aileron will be to the left and rudder will be to the right. If you don't consciously remember to center the rudder before the nosewheel touches, you could be surprised by a sudden veer toward the weeds to the right of the runway.

Cessna solved the problem by putting a centering cam in the nosewheel shock strut, so that regardless of rudder deflection, the nosewheel is always centered when the shock strut is fully extended. (Downside to that is if the strut is pumped up too high, or if the airplane is heavily loaded toward the rear, pushing the tail down, it can be hard to turn while taxiing.) So the linkage has to be loose enough to allow full rudder deflection even while the nosewheel is locked in center.

Piper never used the centering mechanism, but to lighten steering pressures some especially in slow-speed taxi, they did incorporate a bungee into the nosewheel steering linkage in fixed-gear PA-28s and PA-32s, beginning with the 1974 model year. It's not as "loose" as a Cessna bungee, though.
 
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Older Pipers have direct rods to the nose wheel, which is why you don't check the rudder during run up like you should in the Cessna's.
 
Those bungee rods in the Cessna are part of the rudder control system, and the centering of the system is achieved by adjusting those bungee clevises with the nosewheel off the ground and centered.

You wouldn't believe how many of those systems we find way out of rig. Seems like nobody reads a manual anymore.

Nosewheel shimmy is due, first and foremost, by a dynamically imbalanced nosewheel. Dynamic, not static. Static balance will do little or nothing for it.
 
My opinion as to why cessna uses the bungee/spring system is they started producing 172 which were essentially a C-170 with a nosewheel. They were really trying to convince pilots that a nosewheel airplane was a good idea. As a result they designed the nose wheel steering to feel as much like the tailwheel steering of the C-170, i.e. squishy and often requiring brakes to steer.

Brian
 
brcase said:
My opinion as to why cessna uses the bungee/spring system is they started producing 172 which were essentially a C-170 with a nosewheel. They were really trying to convince pilots that a nosewheel airplane was a good idea. As a result they designed the nose wheel steering to feel as much like the tailwheel steering of the C-170, i.e. squishy and often requiring brakes to steer.

Brian
Click to expand...

BTW: they also managed to duplicate tailwheel shimmy.
 
brcase said:
My opinion as to why cessna uses the bungee/spring system is they started producing 172 which were essentially a C-170 with a nosewheel. They were really trying to convince pilots that a nosewheel airplane was a good idea. As a result they designed the nose wheel steering to feel as much like the tailwheel steering of the C-170, i.e. squishy and often requiring brakes to steer.
Click to expand...
Fritz Feutz, the Cessna engineer who first test-flew the 172, explained it (quoted in Cessna - Wings for The World: The Single-Engine Development Story by Bill Thompson, p. 37):

"[O]ur first weeks were spent in the 'barn' with the nose jacked up while we experimented with various combinations of linkages and springs. I was against the Tri-Pacer system where the nosewheel tied in directly to the rudder system and, therefore, it turned in flight and never fully centered. The C-310, which had to have a centering cam to prevent retracting with a cocked nosewheel, offered a possible solution. However, this sacrificed some ground steering authority, which on the other hand, could be overcome with differential braking. This solution proved to be workable, and subsequent ground taxi and takeoff runs enabled us to fine-tune the linkage and spring ratios."​
 
I have Cessna,s and one Piper. I've always hated th ground steering on the Piper. It's so sensitive I have to have to basically stand on the petals to keep it going straight. Just a hair lets it swerve. Wish I could make it more like the Cessna steering.
 
brcase said:
BTW: they also managed to duplicate tailwheel shimmy.
Click to expand...

Only time I've seen shimmy, ether tailwheel or trike, was in WAAY out of adjustment planes, or with students who kept the 3rd wheel on the ground at way to high a speed, or slammed it down.

First flight in my current plane with the old owner he did the first landing, plopped the nose down hard enough that the free steering nose wheels shimmed so bad (plus he wasn't centerline to start with) we almost ended up in the grass, "oh man I'll check the dampers for you", the next landing I did, being extra careful, it was just fine, in his defense the one on the right did need a little love, but smacking it down on the pavement going warp speed didn't help ether lol
 
While there is always some play in the steering bungee system by design, I just had the steering collar bushings replaced on my Cardinal, it made an enormous difference. Take a look up at where the bungee (and damper) connect to the steering collar on the nosegear. There shouldn't be excessive play in those pins.
 
On a 172, there are 30 degrees of travel on either side of nosewheel center. Using only the rudder pedals, you can only get 10 degrees on either side. You need to use differential braking to utilize the other 20 degrees.

On a Piper, you can utilize the whole range by only using the pedals. The brakes aren't needed.
 
Cpt_Kirk said:
On a 172, there are 30 degrees of travel on either side of nosewheel center. Using only the rudder pedals, you can only get 10 degrees on either side. You need to use differential braking to utilize the other 20 degrees.

On a Piper, you can utilize the whole range by only using the pedals. The brakes aren't needed.
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Even I can understand THAT explanation!
 
How many know the Cessna nose strut has a centering device that will lock the wheel centered when the strut is fully extended?
So that is why the cessna system has bungees in the rudder controls. when the system is working correctly it will steer just as well as a piper.
The OP's problem was his cessna was not working as intended, and he should have had it fixed.
 
Tom-D said:
How many know the Cessna nose strut has a centering device that will lock the wheel centered when the strut is fully extended?
So that is why the cessna system has bungees in the rudder controls. when the system is working correctly it will steer just as well as a piper.
The OP's problem was his cessna was not working as intended, and he should have had it fixed.
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A Cessna system that works properly steers fine, but it doesn't ever steer like a Piper. The response is slower, in particular at very slow speeds. The ground resistance precludes the springs introducing a large slip angle. The Piper system can do that. With a Cessna-type system, you must preload the steering and wait for the smaller slip angle to eventually get the plane to the radius of turn you're looking for. Of course, most Cessna drivers (myself included) aren't that patient, so differential braking and engine power is the rule of the day during tight maneuvers. Not to say the OP's system is in rig; I'll bet it isn't and can be made better.

I personally like the Piper system better. I know why Cessna put the system in: so that the nose wheel was always locked straight on touchdown. But, to be honest, I've never been surprised by a veer on a Piper, even in a crosswind. I'm fairly certain it's a high-wing/low-wing difference. The low Piper wing will be in a slower moving crosswind to the high wing Cessna, resulting in less need for a locking system.

Hmmm...thinking about that... How nasty are crosswinds in amphib 182's that are miles off the ground? Way up there, up at the height of the windsock, the crosswind is probably at full strength!
 
Tom-D said:
How many know the Cessna nose strut has a centering device that will lock the wheel centered when the strut is fully extended?............
Click to expand...

Not many - including many mechanics that ignore roll clearance motion in the steering collar (or whatever it is called) and instead look only at the damper.

I think the Cessna steer system also allows a sharper turn radius for parking etc than the Piper.
 
nrpetersen said:
Not many - including many mechanics that ignore roll clearance motion in the steering collar (or whatever it is called) and instead look only at the damper.
Click to expand...

They also ignore the slop in the torque links and that, together with the steering collar rocking, the nosewheel has lots of angular freedom before the shimmy damper has anything to do with it.
 
Dan is right. I should have included that.

I have found that letting all the strut charge out, tying the tail down, & then lowering the collapsed strut by allowing a small amount of air back in allows one to evaluate where the motion is lost as the nosewheel is yawed looking at the damper.
 
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It's also interesting to note that many of the Piper nose wheel pants have a fin on them.
 
Lots of great information here, gentlemen, thank you.

To clarify a few points:
- I only experienced the nose shimmy on taxi and it was not fast, nor sloped or over rough surface. That is why it surprised me. And had it happened on landing, I don't think I'd be speaking to you in the same underwear. :)
- the "slop" in the Cessna steering is not unique to mine, I have experienced it on all Cessnas I have flown but granted, all the others were school airplanes, none privately owned so then again, I might be performing an unfair comparison
- yes, my Cherokee had that fin on the nose gear fairing - awesome rudder helper :)
- I did not notice any play in the nose gear dampener and I will look at it with my mechanic later - now that I know what to look for/at - I am still learning all the bungee cords on this plane :)
- yes, my old Cherokee had the direct linkage to the steering and I enjoyed it immensely due to its tight coupling and precision steering - I drive sports cars and like/love/seek/demand precision handling - and as I can see, this a very hot religious topics among pilots so please let's not allow the thread to devolve into fighting over loose/tight steering

Again, thank you for the great responses.
I flew her for about 3 hours this weekend and had a blast.
Now let's go fly some more! *nod* :)
 
Dan Thomas said:
...Nosewheel shimmy is due, first and foremost, by a dynamically imbalanced nosewheel. Dynamic, not static. Static balance will do little or nothing for it.
Click to expand...

Can you explain the difference in the two?

<----- dumb Arkansas country boy
 
A dynamic balance is done on a moving propeller. A static balance is done on a still propeller.

With a static balance, we're using the force of gravity as a stand-in for the forces on the spinning propeller. It's simple and cheap...just lay the propeller on the balance stand and file off material from the heavy end until the propeller is perfectly level.

Unfortunately, gravity is an imperfect model of the real forces on a propeller. In particular, gravity pulls straight down from all points. But the spinning propeller, the forces radiate from the hub. So gravity would be a great model if the blades were just a straight line. They're not: they have a complex shape with ever changing width and depth. That means that where you file or add material matters to any vibrations produced. So, instead, mount the propeller to an engine, stick accelerometers on the engine, and an optical tach on the propeller. Pipe all that data into a small computer in the dynamic balance device and it'll tell you where to work the prop. Rinse and repeat.

Crap...I just wrote all this and realized we're talking about the wheels, just like on a car. Same thing: a round wheel has depth to it, so a static balance is never going to be perfect. Instead, a dynamic balance machine spins the wheel and determines the forces applied to the shaft that spins it. It then instructs you where to put the balance weights, which include instructions on which side of the wheel they go on. That's something a static balance can't tell you.
 
arnoha said:
A dynamic balance is done on a moving propeller. A static balance is done on a still propeller.

With a static balance, we're using the force of gravity as a stand-in for the forces on the spinning propeller. It's simple and cheap...just lay the propeller on the balance stand and file off material from the heavy end until the propeller is perfectly level.

Unfortunately, gravity is an imperfect model of the real forces on a propeller. In particular, gravity pulls straight down from all points. But the spinning propeller, the forces radiate from the hub. So gravity would be a great model if the blades were just a straight line. They're not: they have a complex shape with ever changing width and depth. That means that where you file or add material matters to any vibrations produced. So, instead, mount the propeller to an engine, stick accelerometers on the engine, and an optical tach on the propeller. Pipe all that data into a small computer in the dynamic balance device and it'll tell you where to work the prop. Rinse and repeat.

Crap...I just wrote all this and realized we're talking about the wheels, just like on a car. Same thing: a round wheel has depth to it, so a static balance is never going to be perfect. Instead, a dynamic balance machine spins the wheel and determines the forces applied to the shaft that spins it. It then instructs you where to put the balance weights, which include instructions on which side of the wheel they go on. That's something a static balance can't tell you.
Click to expand...
------

Crap indeed! I was reading that, and thinking, "Wow, I had NO IDEA an unbalanced prop could caus a wheel shimmy," lol.
 
Theboys said:
I have Cessna,s and one Piper. I've always hated th ground steering on the Piper. It's so sensitive I have to have to basically stand on the petals to keep it going straight. Just a hair lets it swerve. Wish I could make it more like the Cessna steering.
Click to expand...

Funny, I trained on Pipers and _hated_ the Cessna ground handling. (Still do, but I deal with it!)

It always felt a little bit more "out of control" than the pipers. In fact, transitioning Piper -> Cessna, I'd say it was the biggest change I had to get used to.
 
Theboys said:
I have Cessna,s and one Piper. I've always hated th ground steering on the Piper. It's so sensitive I have to have to basically stand on the petals to keep it going straight. Just a hair lets it swerve. Wish I could make it more like the Cessna steering.
Click to expand...

What he^ said.

I find a crosswind annoying in a piper when I taxi.
 
dans2992 said:
Funny, I trained on Pipers and _hated_ the Cessna ground handling. (Still do, but I deal with it!)

It always felt a little bit more "out of control" than the pipers. In fact, transitioning Piper -> Cessna, I'd say it was the biggest change I had to get used to.
Click to expand...

That's called Primacy: First impressions are the strongest. What you train in is what you will think an airplane should be. I did my early training in a 172, then later on did some in a Cherokee 180. Thought the Cherokee was clunky. It had the single-lever brake, too.

When someone learns to fly in a taildragger, he thinks trikes are for sissies.
 
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