Couple of Arrow questions

E_Dawg

Moderator
1) Can someone please explain exactly how the rudder trim works in the Arrow?

2) What is the mechanism that -disconnects the nosewheel from the steering linkage upon liftoff? -centers the nosewheel upon liftoff?

Thanks in advance
 

stuckingfk

Well-Known Member
1) I believe it is a spring that holds the rudder in the direction you spin the rudder trim wheel inside the cockpit.

2) I know the arrow has these, but I am not sure what it is called.
 

cime_sp

Well-Known Member
[ QUOTE ]
1) Can someone please explain exactly how the rudder trim works in the Arrow?

2) What is the mechanism that -disconnects the nosewheel from the steering linkage upon liftoff? -centers the nosewheel upon liftoff?

Thanks in advance

[/ QUOTE ]

Take a look at the nosewheel the next time you are under there....it is not directly attached to the rudders but there are points on the nosewheel where "bars" (for lack of a better word) attached to the rudder pedals press against corresponding "bars" on the nosewheel assembly in order to steer it. It will be way at the top of everything. When you retract the gear these "bars" no longer make contact. As far as centering goes there is a "guide" on the nosewheel that looks sort of like a funnel cut in half attached to the nosewheel assembly. As the gear goes up this "guide" comes into contact with a "pin" in the wheelwell that centers the wheel.

Hope this helps and sorry about the word usage I know it's not technical!
 

E_Dawg

Moderator
For 1) I finally found it in an AOPA article; it is just a spring loaded mechanism that connects directly to the rudder torque arms, which sets the neutral position of the pedals. It has no connection to the actual rudder.

Go figure, my CFI didn't know this either and on my Comm ride I guessed 'bungee tension' when asked and the examiner was happy with that.
 

CaliforniaSurfer

Well-Known Member
[ QUOTE ]
Go figure, my CFI didn't know this either and on my Comm ride I guessed 'bungee tension' when asked and the examiner was happy with that.

[/ QUOTE ]

Because it probably isn't that important.

Surf
 

cime_sp

Well-Known Member
I love some the stupid questions that people get asked on checkrides or that are being taught. They are found nowhere in the POH, FAA pubs etc... but some examiners want you to know them and some CFI's teach some pretty obscure crap.

On my IFR checkride I was asked what the black ball in the TC is made of....and also what the height of the GPS constellation is.

In NO way is knowing either of these things going to make any difference in an airplane or will it affect my abilities as a pilot, but for some assanine reason they wanted to see if I know them...which for some reason I did


These ?'s also came from the same guy though that thought the pushrod tubes helped to hold the head onto the top of the cylinders!!!
 

E_Dawg

Moderator
Here's another one - why is the RPM limited from 2100 - 2350? I was told it is because of vibration problems between the engine and airframe - the POH only limits it for 'extended operation' though.

That's pretty vague - and I have noticed that sometimes on final or while setting up for it the RPMs are near or in the red with the MP set for a good descent rate. I don't consider that 'extended operation' but I do try to avoid it when possible.

Does anyone have more info on why it's limited and what 'extended operation' is?
 

RiddlePilot

New Member
I've wondered the same thing about another plane I've flown. Extended ops between the limits aren't recommended, and there's even a red section of the tach to show it (dunno if the Arrow is like that). Couldn't tell ya the reason, other than I avoid it.
 

ananoman

New Member
[ QUOTE ]
Here's another one - why is the RPM limited from 2100 - 2350? I was told it is because of vibration problems between the engine and airframe - the POH only limits it for 'extended operation' though.


[/ QUOTE ]

Most everything has a frequency that it naturally wants to resonate or vibrate at. Usually when you design a piece of machinery you make sure that this does not occur in normal operation. If this happens it can range from annoying (having some piece of interior trim vibrate like a tuning fork) to very, very bad (having a critical part break due to fatigue).

The parts of an engine are also subject to this. When you look at a crankshaft it looks massive and you think that it must be very strong. In reality it is constantly being twisted in torsion as each cylinder fires and that crank throw is pushed slightly ahead of where it should be while others are pushed slightly behind during the compression stroke. To counter this it is common to attach movable counter weights to the crankshaft. The swinging weight helps damp vibration and their mass helps smooth out the power pulses in the engine. The weights are roughly half moon shaped and hang on the crankshaft by two pins that pass through holes in the crankcheeks. There is a certain amount of play between the mounting pins and the holes they ride in, as it is necessary for the weights to move back and forth to function, but under certain combinations of engine load and rpm, these weights can start to 'chatter' or vibrate, causing damage. This can sometimes happen if rapid throttle movements are made. If you remember back to the private and commercial written, there are some questions that deal with 'detuning' an engine and this is what they are referring to. It can also happen during operations outside the normal range of RPM.

It is common now to develop a new propeller to best match the performance characteristics of an engine/airframe combination when certifying new aircraft. In the past what was usually done was to just find something that was servicable and call it 'good enough'. It was cheaper to put a limitation in the POH than do some more Research and Development. Now it is possible to replace the prop on the Arrow and remove the limitation.

As far as 'extended ops', the goal here is not to spend an extended time in the prohibited range. It is not possible to avoid the prohibited range all together, as you will go throught this range during initial throttle application for takeoff or when pulling the throttle to idle during landing. Just don't stay there.
 
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