Nose gear suspension

[TechMan]

This has come in to the office and it is worth airing because it will affect a lot of Jab owners particularly. Even so, it is a reminder to others to replace rubber shocks, worn or cracked engine mounts, and examining anything on your aircraft made from a poly something or other.

 

This may have been a faulty batch as it had only been put on the aircraft. It may have another reason though the pilot assures me that there were no heavy nose wheel forces on landings.

 

Any more of these out there?

 

Chris

 

 

 

[Ross]

Hi Techman

 

Could we be a little more specific when taking about Jabirus. Everyone seems to imply that the modelsare all the same. There is a lot of difference even within the same model.

 

I have J160 kit and that front shock looks suspiciously like the one in my kit so I would very much like to know a bit more detail.

 

[ATTACH]849[/ATTACH]

 

Likeabout what model it was, kit or factory built, what was the serial serial number of the fuselage, engine number,when was the part manufactured,was it original equipment etc etc.

 

Regards

 

 

 

[Wilfred]

some more information would be helpfull

 

we have a lot of hours on our jab with a lot of harsh??? treatment at times and nothing like that has ever been noticed

 

What model Jab

 

how long on the aircraft

 

and what were the details leading up to the problem

 

 

[Guest ozzie]

has the undercarriage ever been cleaned with solvents or had hi octane (optimax ect) fuel spilt on it. this sort of thing can make polypro dry out and fall aprt as above. ozzie

 

 

[TechMan]

Hi all,

 

A bit more info. It was a Jab UL.

 

I have been told that the rubbers were bought over 4 years ago and stored in a dry cool place.

 

They were put on the aircraft the day before going flying so I don't think that there were any solvents involved.

 

My guess is that these were deteriorated purely due to old age and probably drying out. The previous shocks lasted for around 300hrs.

 

I guess this possibly comes down to normal maintenance and the addage, 'when in doubt, throw it out' for any parts that you are wanting to put on your aircraft.

 

Chris

 

 

[Wilfred]

There is a known problem (hydrplysis) with PU (polyurethane) when it is stored and not used. it is a common problem with shoes.

 

HYDROLYSIS

 

It has been recognised since the earliest days that P.U can be subject to deterioration in its physical properties over a period of time. This deterioration generally takes the form of a progressive reduction it its abrasion resistance, softening and in extreme cases, can result in the material disintegrating through crumbling.

 

The severity of the problem is related to age and the storage environment. It is known that high temperature and humidity contributes to its onset and that long-term storage under such conditions can be expected to result in at least some degree of deterioration.

 

Strangely, footwear, which is actually in use, doesn’t seem to suffer to the same degree.