I generated this at part of another project, thought folks would like to take a look at it. It compares the occurrence rate of accident cause of homebuilts vs. the Cessna 172, Cessna 210, and a variety of fixed-gear Cherokees.
Ron Wanttaja
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I generated this at part of another project, thought folks would like to take a look at it. It compares the occurrence rate of accident cause of homebuilts vs. the Cessna 172, Cessna 210, and a variety of fixed-gear Cherokees.
Ron Wanttaja
Oh, crap.
I was really hoping for something huge in the E-AB column to put a finger on and say "Ah! I'll put extra care into area X of the build!" instead of the spread that's there.
"Builder error" is just too wide to get excited about, as that could be anything from poorly swagged cables to improperly torqued bolts to setting up the elevator to go the wrong way.
As always, though, my heartfelt thanks for sharing stuff like this. It helps keep me thinking about accident chains and how to mitigate them in my build.
And THAT is exactly why I started analyzing homebuilt accidents 15 years ago: I hoped to find definitive "smoking guns" that people could be aware of and avoid. Not the case... causes are just too varied.Quote:
Originally Posted by Frank Giger
Happy to help, Frank. Maybe the attached will be of aid. I went through my database, extracted the first-flight accidents, and culled out the Builder Error events. There's really not that many... 28 first-flight accidents due Builder Error in my 16-year database. But here's how they split out:Quote:
Originally Posted by Frank Giger
Attachment 4818
The prevalence of the carburetor mechanical issues was a bit of a surprise. Here's the Probable Cause for these events:
- "The pilot's delay in initiating landing flare during a forced landing following a total loss of engine power. A factor was the lack of correct venting of the carburetor float bowl."
- "A loss of engine power due to a disconnected throttle/power lever linkage. A contributing factor was the owner/builder's improper installation of the throttle linkage."
- " A partial loss of engine power during initial climb due to an over-lean carburetor setting. Contributing to the accident was the pilot's improper adjustment of the engine's carburetor during construction."
- "The pilot/owner's improper design change which resulted in a blocked carburetor inlet and a loss of engine power."
- "A total loss of engine power during approach due to the improper idle screw/stop adjustment. A factor contributing to the accident was deteriorated fuel."
- "A loss of power control due to a disconnected throttle linkage. Also causal was the inadequate maintenance by the owner/builder. "
Note that two of these cases were problems with the throttle linkage itself.
Of the four Fuel System inside Engine Compartment cases, two were improperly-constructed fuel lines.
For the Control issues, here are the Probable Causes:
- "An aileron control system failure during climb due to an improper welded installation by the aircraft homebuilder, resulting in an inflight loss of lateral control, and an inflight collision with the terrain during an uncontrolled descent and landing."
- "A loss of control due to the mechanical disconnection of an aileron pushrod from its bellcrank as a result of the mechanic's failure to properly secure the pushrod attach hardware. "
- The pilot/builder's attachment inadequate installation of the aileron control pushrods to the control stick assembly, resulting in the ailerons deflecting in a direction opposite of the input applied by the pilot. "
- "The owner/builder's improper installation of the foot pedal scissor beam, which resulted in its failure during hover flight."
Hope this helps....
Ron Wanttaja
Get more training, buy gas more often and fly more to stay proficient. Just think how those simple steps would dramatically lower the numbers.
This ain't rocket surgery.
That helps a lot!
It tells me that I need to get my EAA chapter folks to go over my plane for dumbsh*t stuff I might have done more than a couple times before the first flight. Hell, the other day I noticed that I hadn't tightened down the linkage between the control to the elevator to the elevator push rod. Fortunately, stuff like that on my plane is easy to see and check. Loads of the engine stuff, other than linkage, is test flight stuff. My carb and engine were tuned and broken in by the experts at Valley Engineering, but until it goes down the strip one can't be truly sure.
And why I'm having our expert builder types help with the fuel and electrical systems.
Okay, I plan on roping the tail and doing a pull test with scale at full throttle before flight #1.
Reading + thinking = similar but separate idea. I need to have a second set of eyes check normal maintenance. Nobody has looked at my aircraft routine checks but me for several years. Airlines, military, use QA inspections. I live on an airpark. Why don't I ask a neighbor to double check my work? Am I terminally stupid?Quote:
Originally Posted by Frank Giger
Frank my airplane has been flying for years and still today I will tie her down and do full throttle runs. I do this after getting her out of maintenance where something on the engine was taken off or removed and then reinstalled. I have even been known to do this after doing things like setting timing. My airplane the brakes are not hooked up and doing full throttle runs is tough unless she is tied down. So I tie her down a lot to do full throttle runs.Quote:
Originally Posted by Frank Giger
Tony
These are very interesting to me. I ran my Glasair III engine for the first time yesterday and today did a linkage adjustment to lower the idle. Before running we pumped fuel through the entire system to look for leaks and debris. My understanding is that particularly with fiberglass aircraft debris in the fuel is common and brings aircraft down. While we were careful to keep the fuel system clean and we found no fiberglass dust we did find a couple of tiny metal shards from the fuel lines I assume. After triple checking for leaks with the system pressurized we only found two very small leaks.
The next thing of note is all the control linkages, that's next for me. I need to confirm all control deflection to designed specs and ensure all the hardware is correct and installed correctly.
I guess what I'm trying to say is that this article is timely. It reinforces the need to be methodical and get it right. Further, it needs to continue after the build with good maintainance. I recently had one exhaust come loose on my Glastar. I have over 430 hours on it now and it is annual month. I do a rolling annual a section at a time through the month and I was letter sly going to do the fwf the next day. Made a lot of noise but wasn't dangerous.