I was looking over the new mandatory service bulletin SB-02-23 regarding the fuel pick-up tube loosening for unknown reasons. I built and fly an RV-9A, and I remember insuring that my fuel pick-up tube B-Nuts were tight on both sides (actually three times). The reason that I'm writing this response is that in owning, performing my own maintenance and flying many aircraft over the past 25 years, I have a very hard time understanding the logic for this service bulletin and feel that it might actually cause more problems than hoping to solve. First of all, if the B-Nut on the fuel pickup tube needs to be safety wired, then all other critical B-Nuts on fuel and oil lines that take even more vibration should also be drilled and safety-wired. Now, in saying this, we all know that this should not be necessary and the FAA doesn't require this even on certified aircraft. From my experience, I have never seen a B-Nut that was properly tightened come loose. This brings me to only one logical conclusion--the guy that built the aircraft did not tighten the fuel pick-up tube B-Nut properly.
In being around and seeing other RV builders, I have noticed the following two builder types:
The Builder "A" Type: (this is how I did it): For every build operation, you complete the entire build sequence for that sub-assembly or use a checklist, and then inspect each sub-assembly twice (i.e. make sure the B-Nut is tight during sub-assembly and also just before installation).
The Builder "B" Type: Work on multiple sub-assemblies all at once, jumping between sub-assemblies (i.e. installing hoses and nuts but not tightening them until just before the DAR inspection). They then go back and try to tighten and safety everything up at the end. Builders I have questioned about this practice say that the DAR will find anything loose, and they don't seem too worried.
Now, if everyone opens up their fuel tanks just for one badly managed case, then I see a higher probability that builders are more likely to make a mistake and drill through the B-Nut into the threads or over tighten the B-Nut causing air to get into the fuel system when the tank is less than 1/3 full.
I understand the reason for a left and a right fuel selector is to isolate a fuel problem to one side so it does not lead to an off-airport landing, assuming that you manage the fuel system correctly.
I feel that this builder made 3 serious mistakes:
1. He was a Builder "B" type, and did not get the B-Nut tight.
2. He knew that he had a problem and continued to fly anyway.
3. He did not manage the fuel system correctly during that last flight.
These are my recommendations to Van's:
1. Educate builders on the importance of Builder "A" Type.
2. Show by this example how important locating a "fight critical" issue is.
3. Encourage RV builders to ask Van's Technical Support for input.
4. Educate RV pilots on the importance of fuel management
5. Make sure that things are tight by inspection twice or three times.
6. Educate builders on the importance of inspection during building and maintenance.
7. Maybe require flop-tubes to be safety wired due to rotation of the tubes during flight.
Van's has really designed a near perfect flying machine in my opinion. We just need to listen to what our airplanes are trying to tell us and inspect things very carefully.
John
In being around and seeing other RV builders, I have noticed the following two builder types:
The Builder "A" Type: (this is how I did it): For every build operation, you complete the entire build sequence for that sub-assembly or use a checklist, and then inspect each sub-assembly twice (i.e. make sure the B-Nut is tight during sub-assembly and also just before installation).
The Builder "B" Type: Work on multiple sub-assemblies all at once, jumping between sub-assemblies (i.e. installing hoses and nuts but not tightening them until just before the DAR inspection). They then go back and try to tighten and safety everything up at the end. Builders I have questioned about this practice say that the DAR will find anything loose, and they don't seem too worried.
Now, if everyone opens up their fuel tanks just for one badly managed case, then I see a higher probability that builders are more likely to make a mistake and drill through the B-Nut into the threads or over tighten the B-Nut causing air to get into the fuel system when the tank is less than 1/3 full.
I understand the reason for a left and a right fuel selector is to isolate a fuel problem to one side so it does not lead to an off-airport landing, assuming that you manage the fuel system correctly.
I feel that this builder made 3 serious mistakes:
1. He was a Builder "B" type, and did not get the B-Nut tight.
2. He knew that he had a problem and continued to fly anyway.
3. He did not manage the fuel system correctly during that last flight.
These are my recommendations to Van's:
1. Educate builders on the importance of Builder "A" Type.
2. Show by this example how important locating a "fight critical" issue is.
3. Encourage RV builders to ask Van's Technical Support for input.
4. Educate RV pilots on the importance of fuel management
5. Make sure that things are tight by inspection twice or three times.
6. Educate builders on the importance of inspection during building and maintenance.
7. Maybe require flop-tubes to be safety wired due to rotation of the tubes during flight.
Van's has really designed a near perfect flying machine in my opinion. We just need to listen to what our airplanes are trying to tell us and inspect things very carefully.
John
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