Does anyone have experience operating a legacy Cessna with the Flint internal tanks?

Do the pumps operate all the time?

https://flintaero.com/wp-content/upload ... 7-2013.pdf

The flight manual supplement suggests each pump is manually turned on and off, and is normally off except when transferring. Note this supplement is for a 210, but I looked at a couple of them and they all showed similar verbiage.

I was able to get a copy of the installation drawings since I first made this post and it now makes sense that you wouldn’t want to run the pumps all the time. It looks like it would be pretty easy to overfill the mains.

I’ve been on the hunt for more fuel capacity for quite some time. Passed up on flints a couple years ago because he was predicting crazy lead times post covid. Now it looks like his kits ship quickly and I need someone to give me a compelling reason not to buy a kit.

Isn't the compelling reason to not install flint tip tanks just how far outboard they are mounted? I think it depends on what year they are going into. I recently saw a 1955 (same year as mine) listed for sale that had been modified with Hartwig/Monarch tanks which were an extra 18g additional per side. I want to know how this works, and whether it's currently available as an STC or if it requires a field approval. And gravity feed is always better, no? I'm not sure I understand why fuel pumps would be better - other than the complexity.

I really want a fuel pod for the early 180. Mount that weight down low and aft cg where it wants to be. And removable.

Monarch system is currently available with a long lead time and kit price of usd $15k. Current version is gravity feed and made of rotationally molded polyvinyl which is cool but they will no longer sell just the outboard tanks, you need to buy the whole system. Flint kit is usd $6k.

I believe the thinking on the pumps with the flint system is the chance of fuel starvation in a long bank, maybe like a fish spotter would do.

I never had any trouble with the fuel tanks on the tips in a beaver. Fuel being outboard doesn’t bother me.

If there was a pod available for the wide body 182 I’d be very interested in that too.

Halestorm wrote:
I never had any trouble with the fuel tanks on the tips in a beaver. Fuel being outboard doesn’t bother me.

From a mechanical standpoint, the tip tanks on the Beaver are as simple as one can get...they operate IAW the laws of physics, a liquid in two conjoined containers will indeed seek equal level. The tips are obviously well above the mains in the Beav resulting in the fuel draining completely. Physics also comes into play in flight when encountering turbulence with any weight on a moment arm extended laterally from the roll axis (full tip tanks in this discussion). When encountering an unequal external force to the wings (as most turbulence is) a torque (roll) is induced which must be countered by an opposing force (your flight control input). The required opposing force (your control input) is increased due to Newton's Second Law (F=ma). It is possible with a strong enough external force (gust) to not have enough countering force to stop the rolling motion. Best be comfortable recovering from unusual attitudes. The only method I am aware to alleviate the aforementioned is to only fly in dead calm conditions, even then, by definition, when you impart a roll to turn the aircraft, the resulting force vector you imparted must be countered to stop the roll at the desired angle, once again, a larger control deflection is required.
I have tip tanks on our Beaver and use them occasionally but am keenly aware of that weight out on a very long moment arm. I also have a DeHavilland auxiliary belly tank which I shall be installing as soon as I procure the remaining parts. The aux belly makes refueling on floats much easier than fueling the tips. I am a fan of keeping the weight on the roll axis, (ref my article on ASC fuel pod install this site). What one does with their aircraft is their decision, My "task" as an educator is to ensure they know the possible negative effects.

TR

TR wrote:

Halestorm wrote:
I never had any trouble with the fuel tanks on the tips in a beaver. Fuel being outboard doesn’t bother me.

From a mechanical standpoint, the tip tanks on the Beaver are as simple as one can get...they operate IAW the laws of physics, a liquid in two conjoined containers will indeed seek equal level. The tips are obviously well above the mains in the Beav resulting in the fuel draining completely. Physics also comes into play in flight when encountering turbulence with any weight on a moment arm extended laterally from the roll axis (full tip tanks in this discussion). When encountering an unequal external force to the wings (as most turbulence is) a torque (roll) is induced which must be countered by an opposing force (your flight control input). The required opposing force (your control input) is increased due to Newton's Second Law (F=ma). It is possible with a strong enough external force (gust) to not have enough countering force to stop the rolling motion. Best be comfortable recovering from unusual attitudes. The only method I am aware to alleviate the aforementioned is to only fly in dead calm conditions, even then, by definition, when you impart a roll to turn the aircraft, the resulting force vector you imparted must be countered to stop the roll at the desired angle, once again, a larger control deflection is required.
I have tip tanks on our Beaver and use them occasionally but am keenly aware of that weight out on a very long moment arm. I also have a DeHavilland auxiliary belly tank which I shall be installing as soon as I procure the remaining parts. The aux belly makes refueling on floats much easier than fueling the tips. I am a fan of keeping the weight on the roll axis, (ref my article on ASC fuel pod install this site). What one does with their aircraft is their decision, My "task" as an educator is to ensure they know the possible negative effects.

TR

Fun explanation.

I personally operated beavers for several hundred hours with tip fuel and I could barely tell it was out there, really no adverse roll characteristics I recall. Only time it was a problem was when one side drained unevenly for whatever reason. That resulted in the minor annoyance of having to fly uncoordinated (wing high) for a few seconds to get it restarted.

With regard to the Flint tips does anyone have any experience operating them?

For the better part of 20 years, I owned a Cessna 170B, equipped with an O-360 Lycoming engine, and Flint tip tanks. I also occasionally operated a Cessna U-206G with the external Flint tip tanks.

Both those tank designs operate with small facet pumps, and both plumb into the system similarly. In the 170/180/185 internal tanks, you simply remove the wing tip, the two outboard ribs (maybe three, been a while), slide the tank back in and replace the tip rib and tip. A fuel line is run from the pump to the wing root, and a "T" is insterted into the fuel line from that side's main tank, just downstream of the tank fitting.

Operationally, the recommended proceedure is to run off one tank only for some time, then switch to the other tank, and energize the first tank's Flint pump. The pump forces fuel back up into the main tank on that side. The 206 got a bump of gross weight from 3600 to 3800 with the external tip tanks installed.....no kidding.

You repeat this process on the other side, etc. The tanks vary in capacity, the 170 were 12 gallons and if memory serves, the 206 were 18, and all that fuel is useable. That gave the 170 60 gallons of fuel, which I really loved in Alaska ops, and long trips in the lower 48.

Both these planes (206 and 170) are approved for all normal operations with fuel in tips, including landings. I generally tried to avoid landings with full fuel in the tips, just because of the lever arm out there, but it's approved. Both planes waddled a bit with full tip fuel when on wheels. I also operated both on straight floats. Other than the issues of fueling tips on floats, operation was straight forward there as well.

In twenty years of operations in the 170, I had one of the small facet pumps give up, easy and not very expensive to replace.

I generally switched to one main tank as soon as I was in cruise, ran it there for an hour, switched to the other main, and pumped half the fuel from the tip into the first main, rinse and repeat. That really precluded any significant lop sidedness in flight. A bit of monkey motion, but really pretty easy to manage, and keeps you awake.

I asked the Flint folks years ago why they want you to pump only one side at a time, and with the fuel selector on the other main tank. They said the concern is pressurizing the fuel system, but that was largely to keep the FAA happy.

I never really saw anything I didn't like about the systems. They were incredibly reliable (as soon as I had some fuel out of one main, early in a flight, I pumped a bit out of the tip, just to ensure it worked as advertised, and it nearly always did).

Very simple systems. The tanks are fiberglass.

I also operated a Beaver with tip tanks, and rarely used them. But as noted, those were about as simple as you can get....no moving parts save the selectors.

If I needed extra fuel in a Cessna, I'd add Flint tanks ASAP and not look back. If you want more info, give me a shout.

MTV

I have a C180B with Flint 23 gal useable tip tanks and 25.5 USG in each OEM tank. I typically run down to 14 gal on both, then transfer from one side, while running on the opposite. It takes about a half-hour to transfer each tip tank to empty. Then switch over to the other side. I tried running on the filling side exactly once. The aeration bubbles make for a very rough running engine. Not recommended. I keep the tanks full, even when use isn’t anticipated. There are little polymer-coated balls that serve as check valves, and will leak if allowed to dry, in my experience and per Flint. I had a place up in Kansas that’s done a bunch of them do the work.

Other than dried-up balls, the only problem I’ve had is some glitch in the right fuel qty guage. Some day’s it’s fine, some days the needle is bouncing around. I initially thought it was a ground issue, which requires pulling the outboard rib and then the tank for access. Not a particularly fun job. But then I noticed that the needle was twitching AOG when the master was off on occasion. I thought perhaps there was a stray conductor causing an intermittent, as pulling a couple unrelated CB’s stopped the twitch, but pulling the CB panel and inspection revealed no abnormalities. Oh well, can’t trust fuel guages anyway, still gotta eyeball the fuel level if I want to use it. So, an intermittent mystery. Fuel tanks are worth it, nevertheless.