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Center of Gravity while Solo


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Hey Guys, I recently got my private a few months ago and currently have about 50 hours. I learned to fly in an Enstrom 280FX. Overall it is a great helicopter and when flying with an instructor I feel very comfortable with my flying abilities. It's a different story when I'm flying it solo though. I still feel comfortable flying it in general but I feel like I need a lot of work with my hovering. It almost feels like a completely different helicopter which makes hovering a lot harder and I feel like I'm always using a lot of aft cyclic as it constantly wants to move forward.

 

I know this is expected, but I just am not able to be as precise with the helicopter as I am with an instructor and am having trouble getting used to it. The trim system doesn't help as it took me hours to get used to it in the beginning. If the cyclic is just a little out of trim you're constantly fighting it. Are there any tips you guys might have to help get me used to that change when flying it solo?

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When I first started flying solo, I would put a 25lbs weight under the passenger seat, but after a while I just said f*ckit and got used to the different feel of an empty ship.

 

...or you could just find a chick to take up with you!

 

As for the trim when I flew an Enstrom he had me just move the trim hat instead of the cyclic. It was kind of weird, but it helped me understand just how the trim worked.

Edited by eagle5
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I still feel comfortable flying it in general but I feel like I need a lot of work with my hovering. It almost feels like a completely different helicopter which makes hovering a lot harder and I feel like I'm always using a lot of aft cyclic as it constantly wants to move forward.

 

I know this is expected, but I just am not able to be as precise with the helicopter as I am with an instructor and am having trouble getting used to it. The trim system doesn't help as it took me hours to get used to it in the beginning. If the cyclic is just a little out of trim you're constantly fighting it. Are there any tips you guys might have to help get me used to that change when flying it solo?

 

Flying a helicopter with an electric cyclic trim is very simple provided you understand the system. The cyclic trim system is simply two electrically driven motors that are activated by a switch located on the top of the cyclic. This switch is commonly known as a "Chinese hat”. The Chinese hat is self-centering and can only move forward, aft, left and right.

 

Manipulating the cyclic trim switch powers up either one of the two motors. One motor positions the cyclic control in the fore and aft position and the other motor positions the cyclic control left and right.

 

So, the basic function of the cyclic trim system in a helicopter is simply to positions the cyclic control in a desired position therefore alleviating forces on the cyclic stick. This is also called a force trim system.

 

The basic principle of flying with a trim system is to make a change then check, adjust and trim. For example, if the speed of the helicopter needs to be increased from say 60 knots to 90 knots the first action will be to make an attitude change with the cyclic control alone by selecting a new attitude. This change of attitude has to be checked at some stage when the pilot perceives the attitude for the new speed has been attained. After the airspeed indicator has settled, minor adjustments can be made to the attitude to refine the actual speed that needs to be flown. Only now does the trim system come into play by manipulating the Chinese hat until no forces can be felt on the cyclic control. In other words the trim system should not be used to make the initial attitude change.

 

Most small helicopters with this type of trim system can be flown without using the trim; however, increased counter forces will be felt on the cyclic control depending on the phase of flight. The trim system can reduce the pilot's workload, but if used incorrectly it will greatly increase your workload in so far as you trimming the helicopter completely out of the desired attitude. That is likely why you are having problems.

 

After you become accustom to the trim system, you’ll be able to make cyclic movements and follow-up with trim adjustments almost simultaneously and end up with almost zero stick forces when you reach the desired cyclic position. It becomes seamless.

 

You only have 50 hours in helicopters, keep practicing. If it were easy everyone would be doing it. Don’t under estimate the task of becoming a good helicopter pilot. After 200 more hours you’ll still be weak in many areas.

 

Also see the 2011 post below:

 

Cyclic trim Post - Started by r22butters , Oct 03 2011 18:03

 

Scan-1-1.jpg

Edited by iChris
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So if you have it trimmed up for that 90kt attitude and the engine fails, what are you supposed to do? Seems like messing with the trim in such a crucial phase of flight wouldn't be ideal, but at the same time, I wouldn't want to fight major forces to flare.

 

Also, read that butters thread. How is centering the trim accomplished? By feel? Or is there a button/switch that will center it up automatically?

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The helicopter is trimmed out by feel, at least in the 300. As for autos, I couldn't find anything in my Schweizer POH about the trim, and my R44 POH only mentions trim failure (land as soon as practical) so I'm guessing its a non issue to be "trimmed for 90kts" when its time to flare after the engine fails.

 

I personally never noticed any major stick force fighting against me when I flared a 300, or Enstrom while practicing autos, but I have pretty limited experience in helicopters with adjustable cyclic trim.

Edited by eagle5
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ridethisbike, on 31 May 2013 - 00:53, said:

 

So if you have it trimmed up for that 90kt attitude and the engine fails, what are you supposed to do? Seems like messing with the trim in such a crucial phase of flight wouldn't be ideal, but at the same time, I wouldn't want to fight major forces to flare.

Once you become accustom to the trim system, you'll be able to make cyclic movements and follow-up with trim adjustments almost simultaneously and end up with almost zero stick forces when you reach the desired cyclic position. It becomes seamless.

 

As you can see from the photo, the trim control switch (Chinese hat #5) is atop the cyclic and in easy reach of your thumb. The thumb is normally used to manipulate the Chinese hat, so there is no need to remove your hands from the cyclic stick. In an emergency the pilot make the required cyclic input as normal and follow-up with trim if needed.

 

If the pilot doesn't readjust the trim from the 90-knot setting, the force required to move the cyclic aft will be higher than normal; however, the helicopter will still respond normally to all cyclic inputs by the pilot. The forces remain within the ability of the average pilot.

 

In the case of the MD500 the emergency procedures for a cyclic trim runaway quotes an approximate stick force of 30-pounds in the direction of the runaway. In the case of an Enstrom at the 90-knot trim setting; I would guess you'd need no more than 9-pounds of force at the most. In fact there may not even be an emergency procedures for a cyclic trim runaway in a 300/269 or Enstrom since the forces are so low.

Quote

Also, read that butters thread. How is centering the trim accomplished? By feel? Or is there a button/switch that will center it up automatically?

These types of trim system on non-hydraulic boosted helicopters like the 300/269, Enstrom, or MD500 are centered by feel, trimmed until cyclic forces are relieved.

 

Helicopters with hydraulic boosted controls like the Bell 412 have a Force Gradient Trim System that is used along with an AFCS, not to relive control forces but to hold the cyclic in a desired position in order to hold a desired attitude and provide an artificial feel. No need to manipulate any Chinese hat with this system.

 

Since the hydraulic boosted controls provide such a lightweight feel the Force Gradient Trim System adds feel and allows the trim system to be centered by depressing-holding-and-releasing the trim switch on the cyclic. The pilot depresses and holds down the trim switch, then moves the cyclic to the desired position and releases the switch. The trim centers at that point and any cyclic movement thereafter will be felt as an increasing stick force proportional to the distance from the trim point. The pilot repeats the depress-hold-and-release process to establish a new trim position.

 

There are also AFCS systems with automatic trimming that sense the movement of the cyclic and automatically centers trim.

 

Also, most of these force gradient system have an enable switch (on/off) so the aircraft can be flown without stick trim (Even older ships i.e. UH-1, B205, S-58)

 

 

Huey-18_zpsec574a92.jpg

Edited by iChris
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As for the trim when I flew an Enstrom he had me just move the trim hat instead of the cyclic.

 

 

I couldn't find anything in my Schweizer POH about the trim,

 

 

269C-1 RFM, Sec 4-6, pg 4-14,

 

NOTE: Do not use trim controls to move cyclic stick into position; this practice induces strain on the trim control system and may burn out the trim motors.

Edited by iChris
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269C-1 RFM, Sec 4-6, pg 4-14,

 

NOTE: Do not use trim controls to move cyclic stick into position; this practice induces strain on the trim control system and may burn out the trim motors.

 

We must have different manuals for the Schweizer?

 

The guy who told me to move the hat to move the ship was an Enstrom CFI. I only flew it once, so I don't know if that's how he instructs his students to fly all the time, or if he was just showing me something cool?

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P. 3-7 just above the hydraulics system failure. Its only in my R44 POH, maybe you have the R44 II one?

 

Yea. That's what I thought. That we have different POH's. My understanding is that the early 44s didn't have hydraulics so a trim system would make sense. Is it the same style trim as the 22? Pull the knob to relieve the pressure by tensioning a bungee cord?

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Yea. That's what I thought. That we have different POH's. My understanding is that the early 44s didn't have hydraulics so a trim system would make sense. Is it the same style trim as the 22? Pull the knob to relieve the pressure by tensioning a bungee cord?

 

That was the Astro. Most of them have been converted to hydraulics by now, but I'm sure there's still one or two lurking about somewhere? The trim was adjustable, more like the 300 and Enstrom, intead of just pulling a knob like the 22.

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That was the Astro. Most of them have been converted to hydraulics by now, but I'm sure there's still one or two lurking about somewhere? The trim was adjustable, more like the 300 and Enstrom, intead of just pulling a knob like the 22.

 

 

The older R44’s without hydraulic were equipped with an automatic (so to speak) electric trim system. The system includes strain gages mounted to the cyclic stick to sense control force and electric trim motors at the base of the cyclic, which automatically minimize these forces based on the outputs of the strain gages.

 

It allowed for fine adjustments via a trim control on the cyclic.

Edited by iChris
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