7AC Replacement Struts

[zipperdu]

After flying this 7AC awhile I finally got the courage to disassemble the oleo struts- Yuck!

One strut had the original fibre piston which had broken apart allowing the attaching pin to beat up on the stuffing box, the results were not very pretty.

The other strut had an aluminum piston but it's stuffing box didn't look so great either.

Both struts had corrosion and pitting on the piston rod, to top it off both lower struts were worn pretty badly.

Anyway, does anyone have a recommendiation for a timely replacement?

Thanks,

Jon Marion 7AC-107 N81488

[Nathan K. Hammond]

About $650 from Wagaero p/n 3-665.

For that much, you could buy all the parts from Wag, do the work yourself and come out way ahead. The only specialty tools/skill needed is a bit of silver soldering and a big reamer for the new bushing.

nkh

[zipperdu]

Thank you Nathan, that was what I was thinking.

A note to everyone about that failed fibre piston- even though the AD to replace that piston is over 60 years old, heres proof that they can still slip by. The piston retaining pin was bent in an arc, beating the stuffing box to an unairworthy condition- if that pin had failed the strut would have possibly fallen out of the airplane while in flight.

One other thought, my 7AC is an early model and the AD 47-20-02 should not be applicable due to serial number (it starts with s/n 226 on the 7AC) that also means that the LG snare cable is not required!

I would suggest that if you don't KNOW what the piston material is then install a snare untill you do!

Thanks, Jon Marion

[MikeB]

The oleo's (regular) are rebuilt on my 7AC with all new parts put I still opted to leave the snare cables on for a little extra insurance. I've also thought about cables for the no bounce gear on the L16 but looks like they'd have to be quite a bit longer.

Being a natural born worrier........................

MikeB

[joea]

Still cannot believe that we are seeing fibre pistons coming out of these struts. At least you found it on the bench and not the runway!

[MikeB]

Would you believe both oleos on my Chief project had the fiber retainers and worn and bent pins? How many annual do you suppose this slipped by with the log book endorsment "Checked all AD's thru XXXX"

Mike

[Paul Agaliotis]

Mike,
The fiber spring retainers are not the items subject to the AD. Only the pistons which are internal to the oleo and only visible thru the drain holes. The retainer damage typically comes from the oleos running dry. The plane slams down with a lot of unabsorbed force as well as the rebound force. Any condition is bad for the oleos, keep them serviced.
Paul

[MikeB]

But ........ I'm looking at the oleo and thinking "if the (upper) fiber retainer breaks it seems the oleo unit can fall out". Which can certainly ruin your day. I understand about the other fiber piston (or whatever) that's apparently located in the lower part of the oleo assembly and is the subject of the AD. I haven't got around to disassembling the oleo itself yet and the fill plug is rusted in at this point......wanna bet they have the wrong parts too?? .

Even though the oleos on my Champ were rebuilt by Safe Air I had the 'snare cables' on it just for peace of mind. The L16 has 'no bounce' so a bit of a different story.

Mike

[Paul Agaliotis]

Mike,
The only way for the strut to fall free is for the bolt to be missing from the oleo frame. The retainer is held in place with a hollow pin and the attach bolt attaches the oleo assembly to the case frane. This puts the attach in a double shear condition. If the retainer should break the aircraft will start leaning to one side, the side with the broken retainer. I've found a lot of stuff broke inside the oleos, and all of it is from running them dry. Keep them serviced.
Paul

[MikeB]

Yup! Just pulled them apart this afternoon and was able to get the fill plugs out. I see there is an aluminum retainer inside the hole so that part is Ok anyway. The piston rod hole is 'somewhat oversized' (due to banging no doubt) and the upper fiber retainer is broken pretty much in half but I believe the new ones are aluminum. I'll have to see if I can come up with a 'slightly oversized' retainer pin. Looks like it can be saved anyway.
Mike

[Paul Agaliotis]

Mike,
I believe Univair has the retainer. I've seen them in fiber, aluminum and even brass. The oleos are a very good design in shock absorbtion but need routine service. I'm sure the fiber pistons would hold up fine if the oleos were kept full.
Paul