Improperly Clamped Fuel Line May Collapse Causing Fuel Starvation

[Guest DavidH10]

Because the detail of this post is buried in another thread, and I thought it should be more easily searchable, I've started a thread for it.

 

Last week, I suffered a fuel starvation symptom on climbout. The issue did not prevent me from maintaining altitude, but it did prevent a sustained climb. Needless to say, I discontinued the flight and landed at the airfield to investigate, while it was still just an annoyance.

 

Cutting to the chase...

 

The problem was caused by a constricted fuel hose, in itself resulting from two factors:-

 

1. The hose connection tube on the output side of the fuel flow sensor is shorter than on the input side, thus allowing a shorter amount of hose to be pushed over it to clamp.
    
    
   
2. The clamp was positioned such that while it clamped the hose in place on the output tube of the sensor, it also overlapped the end of the tube, thus applying pressure to the hose beyond the end of the tube.
    
    
   

 

 

Because of the pressure applied by the hose clamp to a part of the hose not supported by being overlapped on the sensor connection tube, over time the hose slowly collapsed. Over time, this meant that the inside diameter of the fuel hose at that point was getting smaller and smaller. The result was that eventually it reached a diameter where it constrained the fuel flow at or close to full power.

 

The fuel hose was replaced 200 hours ago and removed / refitted on the sensor 100 hours ago. That, therefore is the range of hours during which the tube collapsed.

 

To avoid this situation it is important to ensure that a hose clamp is placed so that there is no part of the clamped hose that is not supported by the tube to which it is being clamped. The photos and diagnosis are located here.

 

* I'm not qualified to provide advice, therefore this is just an account of my experience. Your mileage may vary.

 

 

[Guest DWB]

Because the detail of this post id buried in another thread, and I thought it should be more easily searchable, I've started a thread for it.

Good idea David

 

 

[Old Koreelah]

Thanks for sharing this, David.

 

My plane had no taps at all when I bought it and all I could find were large, heavy and ugly as sin.

 

I ended up fitted four brass gas taps, the lightest and smallest fuel taps I could find. Not being designed exactly for the job, one side is shorter than the other, but I managed good seals on the rubber fuel lines.

 

Three have given reliable service until recently. One always leaked fuel, even when closed, and I used to squeeze the tapered inner part into the outer housing to try to seal the leak. Now the others have also started to weep petrol. Not ideal. Can anyone suggest an better alternative?

 

Regards,

 

Lyle

 

 

[Guest DWB]

Lyle here's some that Aircraft Spruce have on their books. Their Brisbane agent might have them in stock even.

 

[ATTACH=full]938[/ATTACH]

 

[ATTACH=full]939[/ATTACH]

 

 

 

[Guest avi8tr]

Just wondering who actually fitted this unit as I would imagine that it's not part of the standard equipment for your aircraft?

 

 

[cficare]

i missed this forum and posted on another....

 

no heat shield around the fuel lines i see.

 

[T]here are known knowns; there are things we know we know.

 

We also know there are known unknowns; that is to say we know there are some things we do not know.

 

But there are also unknown unknowns – the ones we don't know we don't know.

 

cficare, Today at 3:25 PMEditReport