Can microlights wings fail??

[KFA]

Have you guys had a proper look at your trike's bolts. They are most probably 8.8 or 12.9 bolts. We have been using 8.8 bolts for the past 20 years and have had no trouble at all. You just have to adhere to the replacement shedule and all is Ok. When we design the planes we factor in the strenght of the bolt so it is irrelevant that the bolts are weaker than the AN bolt. Another problem with AN bolts are that they are not metric. The bushing and seemless tubing that we use are metric so that creates a problem with the manufacturing process.

This argument is the same as the 4130 chrome moly vs. the mild steel. If the designer factored the strenght of the 8.8 in his design and it has been tested then there is no further discussion. The problem comes in when guys replace an AN bolt with a 8.8 bolt, then it will be inferior for the job.

[bobthebuilder]

If the designer factored the strenght of the 8.8 in his design and it has been tested then there is no further discussion. The problem comes in when guys replace an AN bolt with a 8.8 bolt, then it will be inferior for the job.

There you have it! .... from a manufacturer.

Thanks .... my point exactly.

[shorebird]

If the designer factored the strenght of the 8.8 in his design and it has been tested then there is no further discussion. The problem comes in when guys replace an AN bolt with a 8.8 bolt, then it will be inferior for the job.

There you have it! .... from a manufacturer.

Thanks .... my point exactly.

You both are totally ignoring this:

I had the displeasure of a wing structural failure in an Aquilla trike several years ago. Shortly after take off (and fortunately on a very calm day), the main bolt that connects the flying wires to the triangular plate on the spreader bar snapped

The snapped bolt above was NOT an AN bolt.

[shorebird]

The problem comes in when guys replace an AN bolt with a 8.8 bolt, then it will be inferior for the job.

Using very simple reverse engineering on that sentence, there is only one conclusion:

AN bolts are superior to 8.8

So why would a manufacturer use 8.8? "Good enough" doesn't cut it.

[FAWGie]

I think we also have to consider that there are other significant differences between an AN grade bolt an any other type of bolt....
The AN grade bolt is subjected to a far higher standard of quality control and x-rayed (screened) for internal fractures and imperfections. The bolt that failed on my wing had a manufacturing imperfection or "internal stress fracture" if you like that had been present for a long time before the bolt ultimately failed. (Moisture had managed to seep into the almost invisible fracture and the inside portion was discoloured)

I don't think the whole argument is about "hard " and "soft" bolts, but more about the quality control of the end product. The designer of the wing as suggested earlier is basig his / her calculations on having a high quality bolt. Only AN grade bolts offer that assurance in quality.