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craigL

T500 Empennage Failure, LOC-I

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This is an accident report of a failure to a Thruster T500 with registration 25-0780. The fault occurred around 1100 on 22 July 2017 i the Lockyer Valley, QLD. It was reported to both ATSB and RAAus.

 

The flight was a training flight with the instructor as pilot in command (very experienced) and myself as the student.

 

We taxied the aircraft several hundred meters to the end of the airfield and I snaked the path a bit by rudder to practice rudder control while taxiing. At this point the rudder was functioning OK. Then we increased the throttle and the aircraft accelerated. When it left the ground, however, it veered widely to the left and then to the right and we could not control it. LOC-I. Hence we cut the power and were fortunate that it landed softly, right way up and without

 

collision with terrain or trees before the end of the runway. We had only reached a height of somewhere between

 

10 and 20 feet. I tried to steer it around to taxi back to the start of the runway, but found that there was no right

 

rudder control, and the attitude was high. We stopped the aircraft and got out to discover three structural

 

faulures at the base of the rear tail strut. This had prevented use of the rudder to control the aircraft, and the tail

 

wheel, which was also structurally supported under the broken piece, but now hung sideways dragging on the

 

ground and supported by its side springs.

 

There were three failures. Two lower breaks separated the rudder support. The higher break was fully detached but

 

held in place by an inner metal sleeve, since it no longer held anything. Both the higher break and the inner break

 

to the right were fresh and the metal had normal colour. However, the break above the rudder cap occurred in highly corroded and paper thin metal. This was not visible before the break because it was painted over. The

 

following picture shows the sites of the failures.

 

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With the broken piece gone, there was nothing to support the bottom of the base strut of the rudder, so the rudder ceased to work. Since the rudder was working during taxiing, this suggests that the break occurred during the takeoff run.

 

Detail showing the highly corroded strut at top. This sleeve and a lot of rough welding on the structure shows rather poor quality repair work. The aircraft maintenance records show that it was wrecked and rebuilt in 1994.

 

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More detail of bad welding on old repair work:

 

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Much of this was hidden by the skins and the inner corrosion was invisible. The failure occurred on the

 

second day of flying the aircraft after I bought it. It had been L2 assessed as being OK and a "great little aircraft".

 

The seller flew it to the L2 and back, so I assume that he was either unaware of the corrosion or not concerned

 

about dying.

 

I'm posting this to encourage others to be extremely cautious about buying second hand aircraft and to raise

 

awareness of possible faults that may be invisible to the eye and not noticed by maintenance certified inspectors.

 

Best regards, good will flying, and may the powers that be have mercy on our frail hides ... as they had for W. and

 

I on this occasion !

 

Craig

 

 

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Thanks for posting this Craig.

 

Your pictures haven't come through though, they may need resizing to get them to download.

 

 

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About what?

Well your post implies the L2 was remiss in inspecting the airframe and the prior owner near negligent or deliberate in selling it.

 

Understand the situation where this comes up 2days after purchase but I like at least another read your post as a pizzed off one.

 

And like another I am glad your here to be pizzed off.

 

 

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Well your post implies the L2 was remiss in inspecting the airframe and the prior owner near negligent or deliberate in selling it.

Understand the situation where this comes up 2days after purchase but I like at least another read your post as a pizzed off one.

 

And like another I am glad your here to be pizzed off.

No, I don't blame anyone. I believe the fault was invisible to the seller, the L2, and myself, but caution others to be aware of this possibility.

 

 

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No, I don't blame anyone. I believe the fault was invisible to the seller, the L2, and myself, but caution others to be aware of this possibility.

Fair enough. Your intent just did not come through to some.

 

And for people looking at the older airframes areas of known corrosion are becoming less well known. Eg the area on your T500 was a known to me as a level2 back in the mid 90's when I was buying my own t500. Equally theT83 and T85 with the ali tail post have known issues of fracture on the lower tailboom bolt through fatigue from flexing due to side load from the tail wheel.

 

TOSG was a great resource and I wish you an inexpensive fix and many hours enjoyment in your thruster because they are lovely old planes

 

 

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Fair enough. Your intent just did not come through to some.

TOSG was a great resource and I wish you an inexpensive fix and many hours enjoyment in your thruster because they are lovely old planes

I like the aircraft, but am at a bit of a loss as to how to go forward, especially since it's 25-xxxx registered ...

 

 

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I like the aircraft, but am at a bit of a loss as to how to go forward, especially since it's 25-xxxx registered ...

PM me but it'll be relatively simple if not inexpensive

 

 

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So what else is wrong with the Thruster, that has also been missed, but not yet found? Where there's smoke, there's fire, an old saying goes.

 

 

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So what else is wrong with the Thruster, that has also been missed, but not yet found? Where there's smoke, there's fire, an old saying goes.

The beauty of the Thrusters (as ugly as they are) is that every structural component is out in the open (or can be very easily exposed) for visual or dye pentrant inspection. With the photos of the suss welding on the stern post indicating less than acceptable practices, a sharp rap with a hammer in that area would have surely given warning of internal corrosion problems? Not pointing the bone at anyone involved but although being a bit picky at the outset might take longer, it's preferable to hollering 'Oh Shite" on your way to meet mother earth after an in-flight component failure. Very pleased you got out of it with minimal grief Craig.

 

 

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You are lucky you didn't get much height. That area is a common corrosion place in many planes. It can also happen on the inside as well as the more visible areas with any tube(d) construction. Thick paint can cover problems. Some treatment of the inside areas will aid stopping corrosion. Trust NOTHING Check everything. Nev

 

 

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While doing the repairs, which Kasper says are relatively simple, would it be advisable to drill and tap a hole at the highest vertical point of frame members so that a small quantity of oil could be poured into the tubing to coat the inner surface as some protection against corrosion? The tapped hole can be sealed with a suitably threaded screw or bolt to restore the integrity of the tube.

 

OME

 

 

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...Thick paint can cover problems...

I've been told it's illegal to use opaque paint on a wooden ladder for that very reason.

 

 

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While doing the repairs, which Kasper says are relatively simple, would it be advisable to drill and tap a hole at the highest vertical point of frame members so that a small quantity of oil could be poured into the tubing to coat the inner surface as some protection against corrosion? The tapped hole can be sealed with a suitably threaded screw or bolt to restore the integrity of the tube.

OME

OME you'll be pleased to know I patched up a leaking galvanised steel water pipe at my house with an AD44ABSLF rivet a few month ago and it's going great

 

 

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OME I'd like to see the section sealed and some fish oil in there. I use a thin coat of white etch on the outside and any crack becomes instantly visible. SEAL it up and some use pressurised nitrogen and if the pressure remains there's no oxygen to cause corrosion and no cracks. That's a good check by just having a small pressure gauge. nev

 

 

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Nev in old Telecom exchanges there was a row of vertical clear tubes on the wall. Each contained a ball showing air pressure in the underground cable conduits. A leak meant a cable was damaged.

 

 

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