Flight issues, plane decends regardless of power setting.

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Flight issues, plane decends regardless of power setting.

New postby Madwood on Wed Apr 13, 2011 12:41 pm

I am having an issue with my Mini Pulse, despite it being a very good aircraft in the past.

With the plane properly balenced as per manufacturers specs, the plane will dive/decend regardless of power setting, resulting it having to be flown with up pressure on the stick. I am sure this can be dialed out with the elevator but it was not like this in the past as the elevator was set even with the fixed horizontal stab.

I fact even with the plane balanced slightly tail heavy it still dives. I have not tried it yet but I have just "shimmed" the motor mount to point the motor up slightly, not sure if this resolve the issue or not.

Athough there is no apparent damage to the airframe it has nosed in a couple times, costing me motor.

Any suggestions?
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Re: Flight issues, plane decends regardless of power setting.

New postby steve on Wed Apr 13, 2011 1:32 pm

A bit hard to say Mike without looking at the plane....but......assuming nothing has changed, and the plane had just started this issue "out of the blue", I would run it up on the ground , with throttle and prop (safely) and confirm the controls especially the elevator moves only as directed and neutral stays exactly where it is. Have you added any throttle to elevator mixes lately or programmed anything?

The plane flies well and even on mine, my elevator is neutral with surface but my CG changes the whole plane when adjusted.

It is odd that it has just started happening given no previous issue.

- Motor power still good?
- elevator neutral correct, even when WOT and no stick input
- Everything looks good to you, nothing changed on the plane or radio, no mixes or other featres added in the model programming.

Perhaps someone else can chime in with some advice.


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Re: Flight issues, plane decends regardless of power setting.

New postby astroflyer on Wed Apr 13, 2011 1:41 pm

what kind of control rods does it have. Is there any way the clevis or whatever method is used could have slipped on the elevator rod itself?
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Re: Flight issues, plane decends regardless of power setting.

New postby Madwood on Wed Apr 13, 2011 4:20 pm

Just checked things all out, elevator moves freely as do all the surfaces there appears to be no mixing with the throttle and elevator at all. All linkages are those supplied as this is a BNF, metal rods that are very short in length (longest one is only about 4 inches).

Looked again for any deformities in the fuse nothing, although one hold down screw for the wing was backed off slightly, but there was no apparent movement in the wing.

This decent was first noticed a few months back when I handed t he transmitter to another HEFA pilot who could not control the plane, I guess I just got used to it as I tend to like to fly with a little up pressure on the elevator. But while flying a week or so ago it became apparent that it was excessive, and so my concern.
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Re: Flight issues, plane decends regardless of power setting.

New postby steve on Wed Apr 13, 2011 5:38 pm

Well if you cannot find anything wrong, then you could easily adjust yor trim to fly properly. Land the plane, measure the neutral deflection on the elevator (no stick movement) and then reset your trim to 0 or where it was. You can then adjust your elevator sub trim or move the linkages to achieve this deflection so it becomers your new "neutral point. you will now have full movement of your main trim again and the elevator will be trimmed somewhat. You dont have to do this sub trim but it is simply the way I was taught and it makes sense overall

Surely, motor shimming and other techniques can work but figuring out what is causing the problem is the best approach however, this method gets you back in the air without having to hold pressure on the elevator.

I strongly suggest however that you restrain the plane, run it up, and watch for aileron movements with and without stick input to confirm all is steady if not already confirmed

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Re: Flight issues, plane decends regardless of power setting.

New postby steve on Wed Apr 13, 2011 5:46 pm

how about adding a washer or 2 at the wing trailing edge at the wiing hold down bolts. Do you think that may help the pitchiness (?)

Im not sure... :?:

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Re: Flight issues, plane decends regardless of power setting.

New postby saboo on Wed Apr 13, 2011 6:11 pm

There are several situations that will possibly cause this. Check the security of the wing hold down at the leading edge. Has the position changed from the nose overs it may have taken? Did the bulkhead or former that supports the leading or trailing edge get moved?

Check the ailerons. Do you have reflex in them? If they are both trimmed up slightly it has the same effect as lowering the wings angle of attack, requiring up elevator. Depending on the radio, you could have induced some up trim on both servos. If you can't find a setting in the radio use the pushrod clevis' to take out any aileron reflex and if necessary put a slight down trim in each of them. Also check the aileron hinges. If they have become loose the aileron may slide back slightly in flight. This has the effect of changing the pushrod length and thus the aileron trim.

My suspicion is that something has moved due to a glue failure or slight crack or compression of material. If the wing is held with a bolt at the trailing edge and a tongue or other fixture at the leading edge, compression of the aft part of the wings surface that contacts the fuse could effectively change the angle of attack.

To see if you have down or up thrust of the motor, check with a builders square or extend the propellor length with a ruler or yardstick to see if the thrust angle has moved. Pull on the motor to see when the prop is pulling, if the motor moves. Hold the plane by the wing tips, rightside up and then upside down to see if the weight of the fuse causes the wing to reposition.

That is all I can think of now.

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Re: Flight issues, plane decends regardless of power setting.

New postby steve on Wed Apr 13, 2011 7:01 pm

Sounds like a fine candidate for your combat entry ....

lol

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Re: Flight issues, plane decends regardless of power setting.

New postby Madwood on Wed Apr 13, 2011 8:19 pm

Keep your combat away from my pulse :evil: I have been considering the combat fighters though, and i think i have all the electronics here already. :D
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Re: Flight issues, plane decends regardless of power setting.

New postby CF Av8or on Tue Apr 19, 2011 12:15 pm

Mike,

As alluded to by Saboo, I believe your issue could be with the wing's angle of incidence. This is the angle between the chord centre-lines (or zero-lift lines) of the wing and the tail. This angle should be zero or slightly positive, depending upon the type of aircraft. Positive incidence means that the wing has a slightly higher angle of attack compared to the tail-plane. For a fully aerobatic aircraft with a symetrical airfoil, zero incidence is ideal, as this permits inverted flight with no trim adjustment. For a sport plane or trainer, some positive incidence is preferable as this adds some inherent stability to the plane.

My guess is that if you were to measure this incidence angle, you would find that you have some negative incidence. This could happen if the wing saddle and/or hold-down system has been disturbed at some point (hard landing, etc).

Vic
Last edited by CF Av8or on Tue Apr 19, 2011 3:04 pm, edited 2 times in total.
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