Thread: Fuel Sight Tubes

Don't know how much engineering would be involved but, my eyes would like a small colored ball floating in the sight tubes. My eyes find it hard to exactly see the level, especially during preflight, not to mention during flight.

Paul

if i want to check the site tubes ( in stead of dipping ) i give the wing a shake and find the level easier to see if it is moving.

i only keep tape over the site tube openings when very cold.

A ball in any liquid sight tube can and do get stuck or give false readings. Our tubes are not all perfectly round from top to bottom because of the soft plastic and they are bent. The ball would not be able to move freely and could get stuck and you would think you had a different fuel level. They can lodge at the top or bottom. As a fireman for 28 years we used these devices and they do help sometimes, but other times they gave false readings.

I like Paul's idea and agree with Roger. To use a ball, the design would probably need to use a straight glass tube which would take redesigning the fitting locations. Probably an increase in weight too.

Others have pointed out some problems with the idea of a fuel float making the fuel level more
readable, putting a float in sight tubes is not unheard of. The Grumman AA-1, AA-1A, and AA-1B
had an Airworthiness Directive (AD 78-13-04) requiring the installation of floats on the fuel
site gauges. The purpose was stated as:

To provide increased visibility and readability of the fuel measurement gauge and thereby
to minimize the occurrence of unintentional fuel exhaustion in flight, accomplish the following:

In those gauges, the tube was glass, and inside a protective metal case. Clearly the previous
writer is correct in that a flexible tube could be squeezed and jam the float.

Alan

The thing that amazes me the most is that with all the hoopla from FD regarding all of the modern electronics in their aircraft, they end up with a poorly designed site glass (which isn't really glass) to provide us with critical information on one of the variables in an aircraft that can actually kill you!!!

I think the fuel sight tubes are the most fool proof, reliable and accurate fuel indicators possible, so I disagree with your comments.

Just add some petrol fuel dye comes in lots of different colors would make it easer to see ...

Rgs Mike

rodghearing,

Them's fighting words!!

Give me the site tubes any day of the week. I'm loaded with electronics but when it comes to fuel -- being able to "look at it" sure seems to be one heck of a lot better then a gauge that might be faulty! I'd have to give kudo's to FD for this sure fire method of "am I out of gas or not"!!

Roger

Yip, i would have to agree, the sight tube are 100% reliable

I cut some clear isotate sheets, in circular shape and silconed them on, over the viewing holes. Now im snug as a bug ina rug

However, on the downside i now get a cold hand when resting on the throttle as it draws cool air in from somewhere else

i'll post photo's soon

take it easy

neil