Aft Fuel Tank

[Scott Crosby]

My Cadet (457) has the optional 15 gallon aft fuel tank. My 90hp Franklin that came with it also has the 8 qt sump that appears to be required when the aft tank is installed. (I assume for weight & balance purposes)

I have looked at every photo of a Cadet that I can find and I can't see any of them with a rear tank filler like mine. It is on the upper right side just behind the passenger door. How many have this option?

Anyone have any experience with this rear tank or any thoughts about it? I almost wish my plane didn't have it.
Kind of somewhat defeats the simple nature of the Culvers I think.

I can take a photo of the installation if someone would like to see it.

[Paul Rule]

I have 2 (not installed) rear tanks.  One is "D" shaped and (I think) made at the factory.  The other is more rectangular and taller, and I am not sure of its history.  Neither has an outside filler cap... both to be filled by tipping the seat back forward.   I have no drawings for plumbing.  I would think the main tank would have to be less then 1/2 full for any fuel to feed forward from tank to tank.  For the aft tank to feed the engine directly it does not have enough head for a climbing attitude so I would expect its 'level flight only'.

The larger oil tank on the engine is a regulatory requirment, I think.  The regs required that you not run out of oil before you run out of gasoline!!!

[Bill Poynter]

Scott,  I've never seen a Cadet with the aux tank installation.  If you can post some photos, it would be great.  Is the plumbing still in place?

[Scott Crosby]

Here's a couple photos.

[Scott Crosby]

I'll try again

[Paul Rule]

Good pictures Scott.   They started me thinking about my tank.  A few questions;)

I am still not very sure how the factory might have hooked it up.   The 'ticker pump' was not available in 1941 although there were other rotary type electric pumps they might have used.

The aluminum line from the sump going off to the aircraft right is an outside drain valve of some kind I assume.
What is the aluminum line from the 'T' on the pump for?
How ie the supply line going through the bulkhead plumed into the front?  Probably just an inline valve on the LH side and a 'T' into the front tank, right?
Is that front 'T' up or down stream of the main shut-off? It would make a big difference in how the system works. 

If it is up stream you would keep the main tank supplying the engine at all times and just 'refill the main' from the aux as the main tank level went down and have to keep an eye on it so as not to over flow the main.

If it is down stream of the main valve it could operate exactly the same OR someone could shut the main valve when feeding from the aux there by remove the possibility of overflowing the main tank BUT also inviting the possibility of the engine running dry and having to switch back quickly to the main, hopefully not near the ground!

I guess there are no placards or operation instructions in the papers?  Any idea of the added (empty) weight?

The last question.... when would any of us want/need to stay up in a Cadet for 6-8 hours???

[Scott Crosby]

I agree - who needs that kind of range?  I wish I didn't have this tank but I don't think I can remove it without
de-skinning the fuselage.

Both left and right aluminum lines going down from the tank go to quick drains.
The line runs through a bulkhead fitting and then along the left side next to the seat, then up to the panel.
There is a fuel selector on the panel with  main/aux positions. (it may have an off, too. I'll check)
The panel has an aux fuel pump switch.
I will check and see if the aux tank feeds the main tank or goes directly to the engine.

[Bill Poynter]

Two questions that occur to me; Did the factory provide a hatch to remove/service the tank?  Did the Cadets with a factory installed tank have a gross weight increase?

I always assumed that since the TCDS says the location is "aft of seat" that they meant in the baggage compartment.

[Scott Crosby]

I just looked at my aux tank plumbing.  The line comes up and through an on/off valve on the panel and then feeds directly into the back top side of the main tank. That's it.  I used to have a plane that used a hand operated wobble pump that was used to keep the aux tanks topping off the main tank. You would know the tank was too full when gas would overflow the vent! 

[Paul Rule]

Bill, the Heltons, I think, had about a 18" x 18" inch hatch on the RH side just aft of the bulkhead.  One of my airplanes has a large hatch too.  That's what I was talking about to get the tail cone properly varnished in all the corners.  The tank would go in and out of something like that I think.  Some airplanes mounted battries back there I think.  That hatch would be needed for that too.

[Brett Lovett]

Mine apparently had an aft tank installed at one time, although I don't have any documentation of it.  I do have pretty poor copies of the factory drawings for the aft tank installation.  Apparently mine was installed and removed though the 18x18 inch panel on the belly.  I have to wonder how things like adjusting and safetying the trim cable turnbuckles were done though the original openings. 

[Paul Rule]

Brett,   You have not lived until you have rigged the trim tab system through the round hole only !!!!!     PR

[Brett Lovett]

Brett,   You have not lived until you have rigged the trim tab system through the round hole only !!!!!     PR

I saw LCA-102 (NC20949) a few years ago, and it does not appear to have the round hole !!!!