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Flight Control issues...

18 posts in this topic

Posted

Hey Guys,

I have logged about 15 hours on my Magnum...it has been a lot of fun figuring everything out, but I am at the point that I think I need to make adjustments and need your advice.

First, I believe the tail is flying too low and that the horizontal stabilizer leading edge needs to be raised up.  The reasons I think this is needed is the fact that I am flying around with full "up" trim (Trim tab all the way down), I also am experiencing strange rudder flight characteristics with yaw and no roll with rudder deflection.  I think this is due to the rudder authority being washed out by the prop.

So do you think lifting the leading edge of the horizontal stabilizer is a move in the right direction?

 

Thanks,

Ron

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Posted

Where'd you rig your flaperons with no flaps on? I ended up at around neg 5 degrees (uprigged) 

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Posted

Where is your CG at and at what speeds are you flying?  If I am just cruising around at 70 or so the tail is always low.  If I get it up to around 90 the tail comes up and it feels more "solid"

Believe it or not, a more aft CG helps as you can get rid of all that up trim and she flys much better all the way around.

 

:BC:

 

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Posted

Where is your CG at and at what speeds are you flying?  If I am just cruising around at 70 or so the tail is always low.  If I get it up to around 90 the tail comes up and it feels more "solid"

Believe it or not, a more aft CG helps as you can get rid of all that up trim and she flys much better all the way around.

 

:BC:

 

I pitched my prop for speed and all my tail low issues were gone . I was constantly holding the stick back and trim to keep the nose up . A little playing with my prop I now climb out around 6200rpm and my plane definitely flies better . 

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Posted

Ahhh...this is making more sense to me now.

No Flap setting is -3

The CG is in the forward envelope because of the heavy engine/pilot :)

I noticed the higher speed was making the tail work like I thought it would...slow operations are strange...there is almost a delay to the input which made me put more in, then it is way too much, and the natural reaction is a bunch the other way!  One of those and I was thinking what the Hell!

I was also trying to 3 point my landings which is not working well with the drastic nose up position...So I have been wheeling them on and I have those down pat.

The prop thing is interesting too, because I have an extreme climb prop on it now.  So from what you are saying, that might also be causing the tail sag.

 

Thanks guys, you gave me some things to think about...

Ron

 

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Posted (edited)

I had two beers for my 75th birthday, and soon will have another - Questions like this make me think I should have a couple before answering!  However, just to put my 2c in, while agreeing with the others, and trying to figure out the answers to your questions:   I wonder about the "yaw but no roll" for the rudder:  Could it be that with the longer wings on your bird than most Avids that the rudder wont produce as much roll?  

Also, if you are using full trim to bring the elevator up, then you are trying to push the tail down, moving the front of the stabilizer up would seem to aggravate the problem by raising the tail higher, so you would try to push down more and you already are using full trim. 

Maybe like most birds with heavy noses, you need to enlarge all the tailfeathers / Get the CG farther aft?

Now, if I am completely off the grid, and no one agrees with me, maybe I should have a couple of Bud Lites before writing?  Hope you get it figured out.  EDMO

Edited by EDMO

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Posted

couple of Bud Lites before writing? 

Does sound pretty good, Come to think of it, I haven't had a beer since labor day last year, Maybe that's why I don't post much anymore.

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Posted

I could use a case after today...

I have one wing tank (Left side) that likes to stay full until the right Tank is empty even though the piping is identical on both sides.  I was concerned that the finger strainer was clogged in the left tank, so I did a flow test and both sides drained at equal paces.

I had flown for 2.5 hours and the right tank was empty, I was watching the left tank closely and it was beginning to decrease.  I was about 2 miles from the pattern and the engine began to sputter, I went full rich and the engine came back to life then died.  I then suspected an obstruction and flipped on my fuel boost pump, the engine kicked back on but I could only get low rpms.  It continued to sputter on and off.

The only thing that saved me was that I had been up at 11,500 MSL with a field elevation of 4,700 MSL and luckily was still pretty high when this all happened.

I landed safely and almost cleared the runway but had to get out and push it past the hold short line...aka the push of shame.

I drained the rest of the fuel and found the infamous fiberglass particle around the finger strainer issue!  I had read about it on here, but hoped it wouldn't happen...

I took it back up again and it ran fine and the left tank still doesn't drain equally, but it is better than before!

All I can say is thank God for altitude and fuel boost pumps!

I know this is not inline with the original thread, but Ed brought up another beer being needed :)

I totally agree with your thoughts Ed and I think I will be building larger surfaces.  I did try shimming the leading edge of the horizontal stab and about the only outcome I noticed was that I was able to fly the tail sooner on takeoff...but that could have been wind related too...so many variables that it is hard to tell.

I remember Chris B talking about having to adjust the horizontal stab...I might give him another shout too...

keep the thoughts coming...I'll keep cheating death! :biker2:

Ron

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Posted

Ron,  Glad that you and SuperBird are still OK.  Did you read the posts that Akflyer made about the clear, cleanable filters in his fuel lines?  EDMO

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Posted

Fuel cap not venting properly? My Mark 4 would do the same thing draining one tank faster than the other. Maybe some valves at the tank outlet to control flow?

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Posted

I do like separate valves on each tank myself.  If a guy had a low level warning light on his header tank, he would get a warning that he was about to have trouble.  At that point, it would be easy to switch over to the other tank if it still has some fuel in it.   JImChuk

PS  not to hijack this thread, but does anyone have a good idea for a low fuel level warning with the standard Avid Flyer header tank?

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Posted

Glad it turned out OK!  One thing I have really noticed on these birds.  One tends to slip just a tad one way or the other, or fly slightly wing low on one side.  I use valves on each tank and keep them both on for take off and landing or when I am maneuvering at low altitudes.  In cruise I will burn of one tank for a bit then swap to the other.  This lets me know at plenty of altitude if I have an issue with one tank feeding or not.  I have the clear header tank behind my seat so I can always see if the tank is full and I can watch the flow through the fuel lines going to the header tank as well.  The electric boost pump has saved my ass a few times now when filters start to clog as I will be keeping mine on all my birds now.

 

:BC:

 

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Posted

PS  not to hijack this thread, but does anyone have a good idea for a low fuel level warning with the standard Avid Flyer header tank?

I have a Bad one that came with my header tank from Murl, I can measure it for you to see if it will fit in an avid header tank, It would require you to weld a bung on the side of the tank, with 1/2 inch NPT

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Posted (edited)

PS  not to hijack this thread, but does anyone have a good idea for a low fuel level warning with the standard Avid Flyer header tank?

I have a Bad one that came with my header tank from Murl, I can measure it for you to see if it will fit in an avid header tank, It would require you to weld a bung on the side of the tank, with 1/2 inch NPT

TJay,  How about a photo and price on it too?  I will have to check to see if it fits my plastic Kitfox rectangular header tank.  Thanks,  EDMO

Edited by EDMO

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Posted

Thanks for the input guys...I do have valves on each header tank and could manipulate those valves to correct an imbalance.  I have them safety wired on because another guy on the forum said the DAR made him do that.

I do have clearish fuel lines where I can see fuel moving through.

I believe the fuel caps are non venting, but I do have tank vent lines and one of them could easily be clogged.  I will clean those out.

Leni, I was thinking it was one wing low as well.  It is feeding much more equally now and I'll just plan on checking those filters every time I get the fuel low for the first 100 hours or so...

Ed, luckily I had read his posts and the problems with putting a clear filter too close to the tanks and not having enough fuel pressure to push the fuel through a clogged filter.  When it happened I knew exactly what was wrong, just had no way to fix it.

As far as the low fuel warning goes, if you have a single header tank you could use the "red cube" by flow scan...It has been right on when calculating fuel flow, burn and remaining fuel...you need something for it to interface with like the GRT 4000 EIS.  But I think you are looking for a low cost sensor, I had looked, but never found one.  I wonder if motorcycles/ATVs might have one?

 

Thanks again,

Ron

 

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Posted (edited)

Thanks for the input guys...I do have valves on each header tank and could manipulate those valves to correct an imbalance.  I have them safety wired on because another guy on the forum said the DAR made him do that.

I do have clearish fuel lines where I can see fuel moving through.

I believe the fuel caps are non venting, but I do have tank vent lines and one of them could easily be clogged.  I will clean those out.

Leni, I was thinking it was one wing low as well.  It is feeding much more equally now and I'll just plan on checking those filters every time I get the fuel low for the first 100 hours or so...

Ed, luckily I had read his posts and the problems with putting a clear filter too close to the tanks and not having enough fuel pressure to push the fuel through a clogged filter.  When it happened I knew exactly what was wrong, just had no way to fix it.

As far as the low fuel warning goes, if you have a single header tank you could use the "red cube" by flow scan...It has been right on when calculating fuel flow, burn and remaining fuel...you need something for it to interface with like the GRT 4000 EIS.  But I think you are looking for a low cost sensor, I had looked, but never found one.  I wonder if motorcycles/ATVs might have one?

 

Thanks again,

Ron

 

Ron,  I would un-wire those valves.  You don't want to fight the wire to shut off a line leak in flight.  The DAR was ignorant IMO - What would happen in the event of a crash, or impending crash, and you couldn't turn them off quickly? 

Most of the Avid, and all of the Kitfox tank caps I have seen have the ram-pressure tubes on them - Not to just vent tanks, but to add pressure to the tanks to help fuel flow.   But, I would need Einstein's help to tell me how much pressure increase comes thru that 1/4" OD tube, and if you have other vents I think that might negate the pressure!  Kitfoxes vent the header back to the wing tank, so any ram pressure would not be negated.   I guess Mr. Piper and Mr. Taylor knew, because they used the cap tubes too.   EDMO

Edited by EDMO

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Posted

Avid had one of their owners make a forced landing when the fuel pump quit working.  After that they recommended using the ram air tubes on the fuel tanks.  Supposedly, it gave enough pressure to run a 582 after going though a nonworking fuel pump.  I would use the tubes myself.  I just was looking on the net to see if I could find how flow rates increase with pressure.  Didn't really find anything I could understand.  Something related though, calabrating an ASI with a water column.  According to what I found, 100 MPH equaled about 5" of water column.  Not sure what that relates to in pressure, but Avid thought the tubes were a help.....Hope I didn't wander to far off topic. :-)  JImChuk

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Posted

Nope Jim...spot on!  I do have the ram air tubes going to each wing tank and the also have a tube running to each other.  I think all of that is working, I think it was just my screen being blocked and one tank being empty.

Ed, I had outsmarted the DAR and safety wired the switches with very thin wire so I could break it easily.  I have a fuel master switch 3 feet forward of that for an emergency shutoff.  I think the thin safety wire is actually not a bad idea, it will help inadvertently flipping the valve shut, otherwise your point is valid.

One thing I thought about doing, but I really ran out of room, is running a parallel, unfiltered fuel line with a facet pump inline...It would help in most fuel issues, but not in my situation because it was blocked in the tank itself.

Anyway, thanks for the ideas, I'm looking at all of them.  I wish the Magnum was closer to the other Avids...I sure have some Magnum specific questions.

 

Thanks,

Ron

 

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