WWII Luftwaffe Aviation Fuel Coloring and Cockpit Fuel Tubing (clear portion)

[Juggernut]

Hi all,

 

I've heard that during WWII, the Luftwaffe added coloring to the fuel to differentiate between the different grades (i.e., C3, B4, etc.).  Ive found on a web search the following information:

 

80 Octane: A3 - Light Blue color.
87 Octane: B4 - Dark Blue color.
100 Octane: C3 - Dark Green color.

(WW2aircraft.net)

 

  To wit, would that coloring be reflected in the clear fuel pipe portion within the cockpit of the aircraft (i.e., dark blue)?  Everyone always leaves that particular portion of the fuel pipe clear when it seems to me that if the fuel were colored, that would also be reflected in that clear portion of the fuel piping that runs through the cockpit?  Any ideas, anyone?

Edited November 5, 2022 by Juggernut

[LSP_K2]

My question would be is there always fuel in that line, or only when the engine is running. I'd assume all the time, but have no real idea.

[quang]

3 hours ago, Juggernut said:

To wit, would that coloring be reflected in the clear fuel pipe portion within the cockpit of the aircraft (i.e., dark blue)?

Which cockpit? Incidentally a Bf-109G-14? 

[Juggernut]

All 109F and G had the clear fuel piping that ran through the cockpit.  I don't know about the Karl but no, not the G-14, the G-10.

[quang]

The fuel would appear as a clear/transparent tint set against the RLM 66 black-grey of the cockpit. No, I don’t think you’d see the difference.

[Juggernut]

Well, I know modern day 100LL shows up as a vibrant blue color both in sump jars (against a metal firewall) and on the hangar floor, even after the fuel has evaporated...which is why I posed the question.  I'll take your point into consideration.  I went ahead and painted it clear dark green but if it turns out you are correct, it's easily removed with some 91% isopropyl alcohol.

[RBrown]

The fuel line in question was the feed from the drop tank.  If no drop tank was fitted, or if the tank was empty, there would not be fuel in the line.

[Gazzas]

1 minute ago, RBrown said:

The fuel line in question was the feed from the drop tank.  If no drop tank was fitted, or if the tank was empty, there would not be fuel in the line.

 

Wow!  the tube finally makes sense.  How else would the pilot know that the tank was empty? 

[Juggernut]

12 minutes ago, RBrown said:

The fuel line in question was the feed from the drop tank.  If no drop tank was fitted, or if the tank was empty, there would not be fuel in the line.

 

Ah, that makes sense, thanks for that information. I was thinking it was the line from the main tank to the engine.  That cements my decision to use the drop tank (I'm going to use it).  Now, with that said, would fuel in the pipe be visible "pre-sortie" (as in the drop tank was just fitted and filled)?  Does the ground crew run the fuel boost pump [or whatever] to get the fuel "primed" into the line or does the fuel flow by jet pump (venturi principle) from the external tank into the main tank after the pilot starts the engine)?  I'm assuming there's a petcock someplace (under the R/H side of the instrument panel?) that allows the fuel flow from that tank to be shut off.  Boy, did I open the Pandora's box of questions....LOL.

 

Ya know, on second thought, I'm just going to remove the clear green paint from that clear area, there's too many "what-if's" in my brain and I don't have room for them.  I'm sure there'll be a little staining on the clear part which is beneficial I would imagine.

 

Thanks for all the replies, they helped a lot.

Edited November 5, 2022 by Juggernut

[Juggernut]

8 minutes ago, Gazzas said:

 

Wow!  the tube finally makes sense.  How else would the pilot know that the tank was empty? 

 

There's only one other way I could think of....the engine would cut out.

[RBrown]

Fuel from the drop tank fed the main tank.  The fuel gauge on the instrument panel only measured the main tank.  When pumping from the drop tank the fuel gauge would read full until the drop tank was emptied.

 

On the K series the plumbing was reconfigured slightly.  The fuel line was was routed to a windowed box lower in the cockpit.