I had a bad day in Buffalo

[jatkins]

Has any one ever seen anything like this before ?

I landed, in Buffalo, calm wind, a good touch down, NOT hard ! a very slight swing to the right as the tail came down,...
I apply left rudder, more right swing, and some left brake, and next thing I know , is I hear a bang,
and I get as hard as I can on the brakes .
I pulled the mixture cutoff, as it swung around.

No Prop strike ??

The MS bolts which hold the axel onto the gear leg sheared.

the L/H wing tip is damaged,
the L/H gear box is wrinkled
the L/H elevator is wrinkled
The windshield is broken all along the top where it attaches to the cabin roof.

[flyboy122]

Ughh, my condolences! Brake failure? I've had 2 ground loops, both due to brake failures at very inopportune times. It's amazing how fast it goes from "need at little rudder" to "holy crap the wing tip is a foot off the ground!"

DEM

[C170U2]

What a bummer! Good news is that you are ok and the plane doesn't look that bad. Given the circumstances it seems you handled it about as good as you could.

I'm sure you'll be back up flying in no time!

Mike

[c170b53]

I know the feeling all too well. Summer time and the plane needs repairs. Glad you're ok.

[c170b53]

The weak point of the wing is the inboard trailing edge, if its wrinkle free that tip, like mine is repairable. The glass broken along the top thats obviously not good as something likely has shifted a bit.

[hilltop170]

Has any one ever seen anything like this before?

If I was going to guess, I would say those bolts look like they were over-torqued during installation and broke in the root of one of the first set of threads from the bolt shank. I have never seen an axle bolt fail like that before but other folks may have?

If they were over-torqued, the bolt would have stretched and yielded slightly and necked-down in diameter slightly at the weakest section of the bolt which is most likely in the thread area near the bolt shank. When the bolt stretches, the observed torque will drop off and there will be an urge to tighten the bolt some more. If it is tightened more, the bolt stretches and necks down more but the effect is that the bolt is then under-torqued due to the stretching and is suseptable to fatigue failure at that point. If left in that condition, that is where the bolt will fail if it ever does.

If it was my plane, I would remove the bolts from the other axle and replace them proper bolts and nuts with the proper torque.

However, I don't see how the brake torque plate could jump off of the brake caliper pins like the first picture shows. Even if the axle bolts broke off first and the torque plate came loose, I don't remember there being enough room for the caliper pins to disengage but Its obvious they did.

Another possibility is the bolts were too long and the nuts bottomed-out on the last thread and never got the proper torque to start. It is unlikely all the bolts were too long by the same amount so I still think they were over-torqued.

What does the end of the left landing gear leg look like? Was it noticibly worn off in the skid across the pavement?

[bat443]

Richard, what I am about post is in no way to imply that I know what failed or that jatkins had the incorrect parts installed but is only a possible scenario. He did a nice job of keeping the airplane under control and damage to a minimum. Without knowing the history of the brake caliper and brake disc it is possible that a caliper with the short pins and short bushings in the torque plate intended to be used with the shallower offset brake disc for 600x6 tires was used with the deeper offset disc used with 800x6 tires to give increased caliper to tire sidewall clearance. As the brake linings and disc wear it might make it possible for the caliper to disengage with the torque plate. The caliper may have disengaged with the torque plate and locked up the wheel before the gear leg to axle bolts failed. Just a reminder to keep track that the correct parts are being used when repairs or replacements are made.

Tim

[GAHorn]

Are you certain those are MS bolts? What do the heads look like? Pics? (very closeups if possible)

[jatkins]

Tim,
That is a very interesting, point you brought up. Thank you.
We will certainly look into that possibility, how ever I do know that for certain that the tire did not lockup and skid,
as we have very closely inspected the tire for skid indications, and non are evident.


George,
Yes they are certainly MS bolts they are internal wrenching Allen key, heads.
I will try to post the pictures for you. ( and yes the proper cupped washers were installed.

( The NTSB ) believes that the wheel hub failed, due to intergranular corrosion


John

[mongo2]

Tim, George,

My 170A IPC shows AN-5 and AN-6 bolts for attaching the axles to the legs. Fig 27, items 14 and 15
Are you saying they should be MS bolts like used on the vertical?

Rick

[jatkins]

Hi Rick,
AN bolts are correct for normal application,
MS are called for when on Skis.

John

[bat443]

John, sorry for the damage to your airplane. As I stated in my original post I don't want to imply that you have incorrect parts installed. My real intent was to bring to the attention of others reading this post in the future that great care must be used when replacing parts on modified aircraft and just because the part used as a replacement matches the one removed does not always insure that the correct part is installed unless you know the entire history of the aircraft since it was modified. I purchased a used 180 that had a torque plate with the short bushings on one side and one with the long bushings on the other side. Fortunately both wheel calipers had the long pins.

Tim

[jatkins]

Hi Tim,

Thanks for the reply, no offence is taken.

We will look at this aspect of the wheel tomorrow. I will let you know what we find.

There were only very very faint skids makes on the runway, you had to look very closely to see if they even applied to my situation.
As I mentioned , the tires ( either one ) showed no signs of skidding or flat spots any where on the tires.

I would really like to know, for certain what caused this, and why ?

John

[bat443]

Me too.

Tim