Fuel filler cap locking tab direction?

[Jonathan33]

Greetings everyone,

Can someone help educate me as a new owner of a DA42 about the direction the fuel filler cap locking tab should be pointed?

I was told that it should point forward (towards the direction of flight), but I can not find that in print anywhere.

Any help would be much appreciated!

Jonathan

[Soareyes]

I was told the same thing. Which means you will have to follow behind the line person and turn it back to the front after every refueling.

[Jonathan33]

Soareyes,

Thank you for the response!

Does anyone know where this standard practice originated?

Jonathan

[mhoran]

Interesting. I was taught the opposite. We always point it towards the back. I was told this is so the slipstream doesn't try to open it in flight, and would force it closed. Not sure where these practices came from -- but I've been doing it for over ten years!

[Soareyes]

Does your fuel cap look like this:

Or like this:

The lip on the latch to catch with your finger, or possibly the slipstream, faces opposite directions.

[mhoran]

Aha! The first.

[Boatguy]

My 40NG and 62 are both the second style.

I was trained by CFIDave that on Diamond's it goes aft. If you look at the shape, you can see that it would deflect the air ever so slightly up reducing drag! Or maybe it's just a place to hook your finger into.

Yes, line personnel always orient the tab aft. I've made this a feature. When I do my pre-flight, if the tab is aft, I know I need to open the cap and visually inspect the tank level. If the tab is forward, I know I've done my inspection.

[Mjwatlanta]

Here is what what Concise Guide to Da 40 book says:

[Rmateu]

my cap is the second one, and I was told that the reason to be directed forward is to create a small vortice to clear any puddle of water that might be deposited in the cap because of rain.

[Steve]

One can develop a rationale for installing the cap in either direction. That, however, doesn't mean that either approach is better. I do like Russ' approach, using the direction as reminder of a preflight check item. Also, irrespective of direction, if the O-ring seals are faulty you can get water intrusion either on the ground or in flight through rain. One reason why I replace the cap O-rings every 5 years or so prophylactically, even though my airplane lives in a hangar most of the time.