Yaw/twist issues Airborne Classic

[flyingfooty28]

Hoping to get some advice on an issue I have noticed with my 2003 270hrs Airborne Classic with Streak 2 wing.

 

I bought this aircraft at 190hrs and for the first 50 hrs found the wing and aircraft to fly very true and straight. After some particularly advanced and turbulent flying conducted in Townsville I started to notice a minor yaw/twist motion with the control bar -i.e my right hand position felt and looked like it was closer to my chest then the left and did not look perpendicular to the front mast brace and pod. This was more exaggerated on full power on takeoff. What I have also noticed is the aircraft wing has a very slight/mild right turn now and the right wire wire running from the control bar to the keel seems looser then the right. Inspection of the airframe does not indicate any major bends or twists but I have not done any in depth measurements or testing as I don't have the knowledge or procedure to do.

 

I am really hoping some one may have already experienced this issue and maybe able to send me in the right direction. The aircraft remains safe for flight but i would really like to know what has happened and a way ahead.

 

Regards Footy

 

 

[jsg022]

Footy Cant help with a answer but if it was mine i would not fly till rectified play safe Regards John.

 

 

[Guest davidh10]

From what you describe, how can you determine it is save for flight if you have not done a thorough examination? I wouldn't be flying it until checked in detail.

 

A change in tension of the wires can only mean one of two things:-

 

- wires have stretched.

 

- frame has bent.

 

I'd be sending the wing to Airborne for breakdown, checking and repair.

 

 

[alf jessup]

Hoping to get some advice on an issue I have noticed with my 2003 270hrs Airborne Classic with Streak 2 wing.I bought this aircraft at 190hrs and for the first 50 hrs found the wing and aircraft to fly very true and straight. After some particularly advanced and turbulent flying conducted in Townsville I started to notice a minor yaw/twist motion with the control bar -i.e my right hand position felt and looked like it was closer to my chest then the left and did not look perpendicular to the front mast brace and pod. This was more exaggerated on full power on takeoff. What I have also noticed is the aircraft wing has a very slight/mild right turn now and the right wire wire running from the control bar to the keel seems looser then the right. Inspection of the airframe does not indicate any major bends or twists but I have not done any in depth measurements or testing as I don't have the knowledge or procedure to do.

I am really hoping some one may have already experienced this issue and maybe able to send me in the right direction. The aircraft remains safe for flight but i would really like to know what has happened and a way ahead.

 

Regards Footy

G'day Footy.

 

I would be giving Airborne a call and explaining what you have said on here to them, I agree with JSG022 and would not fly it until you have at the least spoken to Airborne about your concerns.

 

Even if you have to take the wing to them for them to inspect it it would be better than the outcome if it failed in the future.

 

The wing is the only thing that keeps you up there and your priority now should be at the least to ease your concerns and ill feeling you may be showing.

 

Aviation is awesomely fun but very unforgiving and unless you are 100% sure it is safe you should ground the craft for the time being.

 

Cheers

 

Alf

 

 

[eastmeg2]

I've seen that before and it was elongation of bolts holes in the top of the mast.

 

While on the ground with the engine off, get someone to yaw the wing from left to right and back so that the wing is starting to bounce back by itself but don't be too rough.

 

If you can see any rotational movement in your black nylon hang block in the top of the mast relative to the mast, then you need to replace the mast due to hole elongation around the top most bolt of the powder-coated aluminium section of the mast.

 

If you've had an Airborne trike apart before and know what you're doing and have all the tools (including a tensioner for the steel cable inside the mast) you might be able to do it in a day, otherwise get Airborne to do it.

 

Cheers,

 

Glen

 

 

[XC-Buzzard]

Hoping to get some advice on an issue I have noticed with my 2003 270hrs Airborne Classic with Streak 2 wing.I bought this aircraft at 190hrs and for the first 50 hrs found the wing and aircraft to fly very true and straight. After some particularly advanced and turbulent flying conducted in Townsville I started to notice a minor yaw/twist motion with the control bar -i.e my right hand position felt and looked like it was closer to my chest then the left and did not look perpendicular to the front mast brace and pod. This was more exaggerated on full power on takeoff. What I have also noticed is the aircraft wing has a very slight/mild right turn now and the right wire wire running from the control bar to the keel seems looser then the right. Inspection of the airframe does not indicate any major bends or twists but I have not done any in depth measurements or testing as I don't have the knowledge or procedure to do.

I am really hoping some one may have already experienced this issue and maybe able to send me in the right direction. The aircraft remains safe for flight but i would really like to know what has happened and a way ahead.

 

Regards Footy

After Enduring turbulent conditions that knock you around quite a bit, and usually followed up with a rougher, than we'd like landing, Its often the case that our wing tip battons get extra stressed and can be bent out of profile, this can be the cause of one wing slightely lifting and Turning you, needing some countering input to keep a straight heading. Try checking the Batton profile (atleast the last three) on the wing that doesnt lift as much as the other, you will probably find it out considerably. This will need the wing to be colapsed naturally. So take a look at this first before taking further , more drastic action Footy,,, Regards Lance

 

 

[Guest davidh10]

Hoping to get some advice on an issue ...After some particularly advanced and turbulent flying conducted in Townsville I started to notice a minor yaw/twist motion with the control bar...

Ok, now I'm on the PC not the phone, lets do some simple analysis:-

 

...my right hand position felt and looked like it was closer to my chest then the left and did not look perpendicular to the front mast brace and pod. This was more exaggerated on full power on takeoff.

Problem number one. Your keel is likely now not parallel to the trike base bar... more exagerated when flying.

 

I think Eastmeg has answered the most likely cause. Elongated bolt holes for the hang bolt, allowing the keel to twist more that normal in one direction with respect to being parallel with the base bar. This means the metal has been stretched and weakened.

 

Suggested action: Trike Grounded until keel and mast hang point area is fully checked and repaired.

 

What I have also noticed is the aircraft wing has a very slight/mild right turn now...

This could have multiple causes:-

 

• The wing is now not quite aligned with the pod (reported in your first point) and that creates a small yaw force, which will cause the trike to have a tendency to turn.
   
   
  
• XC-Buzzard has identified another two possible causees:-
   
  Wingtip batten has been bent.
   
   
  
• Pocketed wing battens have been bent.
   
   
  

 

 

 

 

 

 

Suggested action: Trike Grounded until wing has been fully checked and repaired.

 

...and the right wire wire running from the control bar to the keel seems looser then the right.

Now think about that. The control bar is a triangle, which is the strongest structure from a bracing perspective, and it is under compression based on the brace wires. If one wire is looser, then the other wire on the same side must also be looser, as it forms another side of a triangle, of which the keel is the third side.

 

If it is now loose, it is very unlikely that the control bar has compressed longitudinally, so the next cause would be either a cable has stretched or the keel is bent.

 

Suggested action: Trike Grounded until cause is determined and repaired.

 

Inspection of the airframe does not indicate any major bends or twists but I have not done any in depth measurements or testing as I don't have the knowledge or procedure to do.

What you describe could be caused by bends that are not obvious to the eye. On a recent SST upgrade with which I assisted the owner and L2, it was discovered after replacing the mast (part of an SST upgrade), that the mast was actually bent. When laid out on the flat concrete floor, there was about 1cm gap under it if rolled to a point where the bend was in the vertical plane.

 

From the wing manual for Cruze / Streak-3... I know it isn't your wing, but check your manual... I bet it is the same procedure..

 

5.50.20 Inspection after heavy turbulence.

 

The main areas of wing structure that require attention after severe turbulence are the attachment

 

points for structures. These include the front and rear wires, the side wires and the main hang point.

 

The sail should also be inspected for any strain or tearing that may have occurred – though this is very

 

unlikely. All of the tubing should be inspected for bending, including the battens against the supplied

 

batten profiles. The opportunity should be taken to inspect the batten fittings at the same time.

 

If the base bar has made contact with the mast brace at any time during flight then they should both be

 

checked.

 

5.50.50 Sail removal

 

The sail should be removed for close inspection of the airframe if the frame is suspected of suffering

 

any damage for example, having bent tubes following a heavy landing, blow over or crash. If the wing

 

suddenly develops a turn after severe turbulence it is possible that some tubes may be bent, therefore

 

close inspection of all the tubes is necessary. It is suggested that the sail should be removed from the

 

frame every 500 hours to check for any signs of fatigue or damage from general wear and tear.

 

The main points to check are

 

-Cross bar hinge joint

 

-Cross bar /leading edge joint (deformation in the bushes)

 

-Leading edge nose joint (deformation in the bushes)

 

-Nose plates

 

-Straightness of the tubes

 

-Elongation of boltholes

 

-Damaged wires

 

-Damage to bolts

 

-Damage to sail

 

NOTE

 

If any part of the aircraft has any signs of damage the part should be replaced prior to re-installing the

 

frame.

 

Call Airborne and take their advice. Damage could be to more than the wing, so depending on their advice and the availability to you of a qualified L2 maintainer, you may have to get more than the wing to them for checking and repair.

 

I have not done any in depth measurements or testing as I don't have the knowledge or procedure to do....

The aircraft remains safe for flight but i would really like to know what has happened and a way ahead.

Footy; with respect, I'd suggest that you know the aircraft is damaged, and if you lack the skills to identify the damage, then stating that the aircraft is "safe to fly" would seem like a leap of faith.

 

Here is a real "Human Factors" situation. You want to fly it, but I think you really know deep inside that you shouldn't. The risk isn't worth it.

 

Get Airborne's assistance. For our interest, post back their advice.

 

P.S. I have been told by a L2 that any time you remove the sail, the wing has to be test flown again.

 

 

[Bandit12]

Now that, David, is why I like being involved in a forum. I know little about trikes (or even less than little) but I really enjoyed reading your analysis and advice.

 

 

[goflying]

Hi Footy, I had a similar experience with the yawing effect, it happened after a very bad landing and the wing would twist left to right when in flight. The damage in my case was an elongated bolt hole at the top of the mast where the bolt goes through where you've got the safety strap attached. Although i also suspected damage to the wing, after a complete strip down the only thing i found was a twisted hang bracket and hang bolt. Hope this helps.

 

 

[flyingfooty28]

Thank you to all for your honest input, in particular David. Eastmeg my initial thoughts were similar to yours and I have done some informal checks some time ago by gently twisting the wing similar to what you suggested and think I did have some movement in the upper part of the mast. I will investigate more and appreciate the advice. For the record I did contact Airborne and my original CFI some time ago about this issue but got no reply from one and Airborne were very vague on the information back with regard to yaw movement with the wing. This may have been an off day for the team at Airborne as they have done great work for me in the past but left a huge hole in my wallet:big_grin:.

 

Anyway my plan of attack is this:

 

1. Inspection of wing battons. With regard to the wing batton profiles is there a template I should have?

 

2. Inspection of upper hang bolt/ mast section for elongation of bolt holes in the top of the mast. (will contact Airborne to clarify movement tolerance)

 

3. Worst case scenario take the trike to Redhead for further inspection and possible replacement of mast.

 

Oh and by the way the aircraft is grounded.

 

Cheers guys

 

 

[Guest davidh10]

You are welcome FF28.

 

Yes. New wings come with a full size paper template for the battens. The template seems to get lost between owners though, so you either need to borrow one from someone with the same wing or order another one from Airborne.

 

 

[Guest Crezzi]

The control bar is a triangle, which is the strongest structure from a bracing perspective, and it is under compression based on the brace wires. If one wire is looser, then the other wire on the same side must also be looser, as it forms another side of a triangle, of which the keel is the third side.

If I may make just a small clarification to your otherwise excellent post David -

 

"control bar" (aka base bar) usually refers to just the horizontal part of the "control frame" (aka A-frame). Using this nomenclature, the control bar is actually in tension rather than compression (for non-strutted wings).

 

<Pedant mode off>

 

Good luck with the inspection & (possible) repair FF28.

 

Cheers

 

John

 

 

[Guest Andys@coffs]

.....Using this nomenclature, the control bar is actually in tension rather than compression (for non-strutted wings).<Pedant mode off>

My turn now, in the air strutted or non strutted its all the same, on the ground, i agree strutted will tend to place the control bar under compression becuae the struts are rigid and wire isnt in compression....

 

<Picky Picky squared Off>

 

Andy

 

 

[Guest Crezzi]

Correct Andy - the control bar on a strutted wing is in compression when the plane is on the ground. Hence its a larger diameter on the SST wing than on Streak, Cruze etc.

 

Cheers

 

John

 

 

[winsor68]

How do I like a whole thread?... this has been fascinating and educational to follow the replies and the outcome. Good work all.

 

Is there a thread of the year award? lol

 

 

[Guest davidh10]

Thanks John & Andy.

 

I was picturing the other two sides of the triangle, but incorrectly referred to the control frame as the control bar.

 

That is one of the good things about the forum. There's always others to correct inaccuracies or misinterpretation. :-)

 

 

[flyingfooty28]

Hello all,

 

Just a quick update. Carried out inspections as indicated by various posts and called Airborne for advice on original fault. I didn't find any standout issues but did however find some minor play in right rotation (around 1/2 to 1 Millimeter) on the top black section of the mast. This right rotation made sense as the original issue was a twist moment to the right. I called Airborne and they suggested to back off the forward and aft bolt (front mast support) and the back up strap bolt to put the top mast section in place and re-tighten. After torquing these bolts up the top part of the mast had nil movement.

 

I will be carrying out a test flight tomorrow morning to check full range/freedom and to hopefully have my original fault sorted. I have included photos for those interested. Thanks to all and will let you know how the flight tomorrow goes.

 

Regards Footy

 

 

 

 

 

 

[flyingfooty28]

Test flight was carried out but there was still some yaw moment to the right present on takeoff.

 

May plan now is to re-inspect the top section of the mast for movement as I found previously. I suspect due to wear in the bolt holes which secure the top section as soon as there is a huge load applied like taking off the top section of the mast is slipping due to this wear. Therefore most likely a mast replacement.

 

Will keep plugging away!

 

Jon

 

 

[Guest Andys@coffs]

John

 

Does your wing use bungees at the end of each batten (Actually you said it was a ST2 so the answer is yes)? If so are the bungees in good condition and have the same tension across both sides of the wing? If it does use Bungee I seem to recall its really only good for a few years and then should be replaced before the individual rubber threads perish.....Readily available at ship chandlers (sp?)

 

What about the reflex bridal? in good condition and applying the same amount of back edge of wing lift to each side? As the trim is wound on and off does the back edge get affected the same on both sides. Does trim position make any difference, not asking at takeoff cause it shouldnt be played with then...

 

My suggestion is to get an instructor (usually also a Trike Lev 2, but check first) to have a look at it if you havent already done so. Get them to do the sail integrity test at the same time.... I seem to recall you could induce or counter turns with the velco tensioning that affected top surface to bottom surface distance etc, but in general you needed to know what you were doing before randomly playing with that aspect of the wing. Seem to recall stories of individual wings that could be made to cruse hands off at faster or slower speeds by adjusting the same thing....Crezzi may know more about this that I do now.

 

Andy

 

 

[Guest Crezzi]

I don't have a lot of experience on the earlier Airborne wings but most wings have a variety of means to affect the handling. If the adjustment isn't described in the POH I think its probably best not to tinker with it TBH.

 

I did have a case similar to FF28's years ago on a British trike which turned out to be that the mounting of the seat frame by the monopole wasn't symmetrical. This particular model allowed, by design, a relatively large amount of yaw movement of the trike relative to the wing which exacerbated the problem at high power settings. IIRC we only identified the problem after putting the "bad" wing onto a different where it worked fine. I've never heard of this happening on an Airborne trike but if you have a mate with a suitable wing (Streak, Streak 2 or Wizard) swapping them over might be a useful experiment.

 

Cheers

 

John

 

 

[flyingfooty28]

John, my Streak 11 doesn't have the bungies, it has the internal spring batterns. Either way I am not to sure if the wing is at fault as the wing flies quite true with power at cruise or below.

 

Crezzi you have given me a great and simple check which I can C/O which I will endeavour to do. The only prob is my two fellow trikers in my area fly Pegasus. I have a CFI about an hour from me so I think a check by the CFI is needed.

 

Thanks guys

 

 

[Guest pembs]

So footy how did you finish off mate

 

 

[flyingfooty28]

Hello there old mate Pembo!

 

Good timing my friend - I am flying the aircraft up to the CFI on Friday for a look. I am confident I have some minor wear/play on the 2 bolt holes which secure the top part of the mast on. This probably happened from flying in the 'washing machine' with an Airborne aircraft. The easiest and probably my only option is to replace the mast - unfortunate this isn't due replacement for another 200afhrs.

 

Mate- missing all you guys up there and cant wait to catch up in Mt Isa next year.

 

Cheers Matlow

 

 

[Guest pembs]

Hey Matlow....glad to see you still going strong, it will be a bugger if it has to be replaced, but remember when I flew Russ's it has the same problem so I think it may be just a characteristic of the airborne did you not get a definitive answer from them? Mt Isa should be good maybe we should drum up some more support on this forum?

 

 

[flyingfooty28]

If your talking about Airborne - they didn't seem to concerned about the issue, I will see a CFI tomorrow who has plenty of experience.

 

Mate as far as 'Flight for Cancer' it maybe a good move especially with insight into the trip itself, i.e planning, route, stops, accommodation etc

 

Say hi to all