Nosegear Leg Replacement

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Steve
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Re: Fuel selector valve universal joint replacement

Post by Steve »

Davestation wrote: Sat Feb 08, 2020 2:29 pm
Steve wrote: Sat Feb 08, 2020 3:04 am If it is more common (as you stated from your experience) further action (AD) might be considered. I never heard about your 5 failures...
It’s already an AD...

Sorry, I was trying to use a relatable parallel and accidentally hijacked the entire thread.
True. I guess all of your failures occurred after the AD was issued.
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Re: Nosegear Leg Replacement

Post by Bing »

The nose strut on my 2006 DA40 broke last year at brake check (thankfully not on landing) causing a prop strike. 7 months later, a crack was discovered in the replacement Gen 2 "improved" strut. Thankfully, the mechanic checks this area regularly despite no AD on this generation of strut. Weather you have the AD version or not, I would have it checked regularly. This plane is used in a flight school. I am not saying it never lands hard but, the instructors keep pretty tight control on the students. Not to mention, Diamond promotes this plane as perfect for flight training. None of the other much older Pipers and Cessnas in the school's fleet have ever had a gear problem. To Diamond's credit, they replaced the second strut and covered all of the associated labor.
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Re: Nosegear Leg Replacement

Post by Rich »

I've recorded 900 takeoffs and landings in my plane. Adding in others' landings, it likely to be above 2,000. No problems yet. But it was never used for primary training. I'm not sure what to think. Way back when the DA40 was introduced, Diamond published a period of flight testing where they had a variety of pilots take off and land 10,000 times. They called the program "Best Tested Airplane". Back when I was a flight instructor (in other airplanes) it was common to be able to pull off 10 touch and go's in an hour. So that 10,000 landings could be surpassed fairly quickly in such an environment.

Cracking at this location in this manner suggests to me that the joint is machined to a too-tight radius, creating a stress focus.
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Davestation
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Re: Nosegear Leg Replacement

Post by Davestation »

Bing wrote: Sun Feb 09, 2020 3:16 pm The nose strut on my 2006 DA40 broke last year at brake check (thankfully not on landing) causing a prop strike. 7 months later, a crack was discovered in the replacement Gen 2 "improved" strut. Thankfully, the mechanic checks this area regularly despite no AD on this generation of strut. Weather you have the AD version or not, I would have it checked regularly. This plane is used in a flight school. I am not saying it never lands hard but, the instructors keep pretty tight control on the students. Not to mention, Diamond promotes this plane as perfect for flight training. None of the other much older Pipers and Cessnas in the school's fleet have ever had a gear problem. To Diamond's credit, they replaced the second strut and covered all of the associated labor.
Now that’s the kind of thing you should submit a SDR about.
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Re: Nosegear Leg Replacement

Post by Davestation »

Rich wrote: Sun Feb 09, 2020 3:40 pm
Cracking at this location in this manner suggests to me that the joint is machined to a too-tight radius, creating a stress focus.
The original leg had basically zero radius, and the improved leg has maybe an 1/8” radius.
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Re: Nosegear Leg Replacement

Post by Bing »

Davestation wrote: Sun Feb 09, 2020 5:44 pm
Bing wrote: Sun Feb 09, 2020 3:16 pm The nose strut on my 2006 DA40 broke last year at brake check (thankfully not on landing) causing a prop strike. 7 months later, a crack was discovered in the replacement Gen 2 "improved" strut. Thankfully, the mechanic checks this area regularly despite no AD on this generation of strut. Weather you have the AD version or not, I would have it checked regularly. This plane is used in a flight school. I am not saying it never lands hard but, the instructors keep pretty tight control on the students. Not to mention, Diamond promotes this plane as perfect for flight training. None of the other much older Pipers and Cessnas in the school's fleet have ever had a gear problem. To Diamond's credit, they replaced the second strut and covered all of the associated labor.
Now that’s the kind of thing you should submit a SDR about.
SDRs were filed for both instances.
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Re: Nosegear Leg Replacement

Post by Rich »

After calculating the considerable torque in a nose-down-rotation orientation against the pivot at all times on the ground (300-400 lb-ft at rest) it's clearly metal fatigue manifesting in this portion of the joint. The "real" cure is not obvious to me. Different material? More material in the pivot root?

Even though I have an ingrained behavior to baby all nosegear (there are plenty of rebuilt Cessna firewalls out there) and I don't log a lot of landings per hour/year it could just be a matter of time.
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Re: Nosegear Leg Replacement

Post by Karl »

Bing wrote: Sun Feb 09, 2020 3:16 pm None of the other much older Pipers and Cessnas in the school's fleet have ever had a gear problem.
Cessna and Piper nose gear issues are very common in flight school aircraft.
I have repaired numerous Cessna a152 and 172 and at least a few PA 28's with nose gear failures.
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