If memory serves the monarch tanks were developed long before the retrofit caps for Cessna fuel bladders.

Monarch tanks are basically copies of old fashioned aluminum tanks made of fiberglass and then later some sort of rotationally molded plastic. These tanks are installed totally different than bladders, there's a big tank cover skin more like a Supercub. Not sure how the newer style caps would work with that.

Further research is needed.

To install Monarch main replacement tanks, the butt rib was removed(had to remove wing from plane) and the tank inserted and rib reinstalled. I'll show a pic showing the same cap and plate is used for bladder or plastic tank. I think the extra 15 gallon tank installed outboard of the originals had the skin cut between the wing ribs so the tank could be placed in that bay. then whatever it took to reinstall the skin. I've never seen caps like Tom's but think that might be for the extra 15 gallon tank. Even wet wings used the screw on caps but the plate was a oval.

180Marty wrote:To install Monarch main replacement tanks, the butt rib was removed and the tank inserted and rib reinstalled. I'll show a pic showing the same cap and plate is used for bladder or plastic tank. I think the extra 15 gallon tank installed outboard of the originals had the skin cut between the wing ribs so the tank could be placed in that bay. then whatever it took to reinstall the skin. I've never seen caps like Tom's but think that might be for the extra 15 gallon tank. Even wet wings used the screw on caps but the plate was a oval.

Good info, thanks!

It's been 15 years since I installed a monarch setup, I think my memories are fading!

What's with the large washer dropped in the neck? Is that ice? Cap sits proud and does hold snow that can drop in tank when removing cap.

I installed Monarch caps on my Cessna 205 at last annual. We've been experiencing intermittent fuel leakage out of the caps ever since. Been through a couple of cycles with the manufacturer with new rubber seals, verifying vent tube locations, etc.

It seems to me the problem only happens when the tanks are topped off (it has 80G extended range tanks). I believe that when it is in that condition and the vent tube is submerged under the fuel that it can siphonabout the top 8-10g of fuel out of the tanks.

Next flight I'm going to run an experiment with one completely topped tank and one at 30g and only run off of the tank w 30g and see if fuel is missing from the topped tank.

Definitely been frustrating as my previous "killer caps" were working fine and had been for 50 years but had to be replaced because they were "dangerous"...

Next flight I'm going to run an experiment with one completely topped tank and one at 30g and only run off of the tank w 30g and see if fuel is missing from the topped tank.

Try and see if it is leaking past the gasket that is between the plate and the bladder. With my caps off, the little flapper deal will actually hold gas from entering the tank when I shake my Mr Funnel. If it can't run in, it shouldn't run out. Also, here's a thought, remove your cap and pour a little sump gas into the neck and see if your flapper will hold it like mine.

I'm pretty passionate about this issue and I've posted on this before on various sites. I was returning home from a trip up north in the bush in a friends 180. He was telling me on the way home how he had a problem with his monarch caps leaking fuel in mid air. He saw the monarch guy at Oshkosh one year and asked him about it. He claimed he had never heard of this before but pulled a bag of washers out from behind the counter. There was at least 500 washers in the bag and he gave him a few and suggested to change the washers. Why do you suppose the manufacturer would travel around with 500 spare washers??

Anyway, as he was telling me the story, we noticed the fuel was dropping in the tank more than it should have. We landed with 2 gallons of fuel that day when we should have had close to 20. We could see after where the fuel had siphoned out in midair.

A few weeks later, we were telling our story to another 180 owner and he said he had the exact same issue loosing significant amounts of fuel in midair on multiple occasions. This gentlemen also went to monarch (5 mins from my house) and complained. The monarch owner told him as well that this was the first he had heard about it. Whatta croc. Both of these pilots removed the monarchs and replaced with the Cessna caps.

Anyway, lots of people have had success with these caps and that's great. We almost crashed that day due to fuel exhaustion. That's why I refer to them as killer caps as do other people here.

gear wrote: Whatta croc. Both of these pilots removed the monarchs and replaced with the Cessna caps.

Anyway, lots of people have had success with these caps and that's great. We almost crashed that day due to fuel exhaustion. That's why I refer to them as killer caps as do other people here.

Thanks for the post Gear. Over the years on different owned 180's/185's, and close to 25 years of being around Skywagons I've never had direct or indirect experience with the factory Cessna caps causing a problem. Absolutely i'm not denying that over the total population of planes and environments there have been issues...because there have.

Just saying that personally with my ownership of these planes and close friends flying them for 25 years I've yet to see the problems. Contrast that with dozens of documented accounts like yours, some with pictures and video...the monarch caps seem have way more unintended consequences. I'm sure the engineered solution was well intentioned, but as far as i can see the "killer cap" moniker looks to be much more rooted in marketing rather than supplying a demonstrably safer system.

59SC

Tough to beat the original cap arrangement on my 53 180.
Fuel cap well is covered by a convex "flapjack" cover,
and the neck itself sticks up high enough that it should never be underwater.
I had to replace the spring-loaded latches on the covers recently, far as I know they were original issue.
Darned Cessna parts anyway, they only hold up for a mere 60 years or so.

All I can say is that something must have changed from when Bill Barton sold them to me and when the new mfg/owner took over. Been remembering some things from 25 years ago. My friend/mechanic had a 1955 180 and he was having vent issues with the original caps like hotrod has. My friend went so far as to make a couple of holes in the front of the domed cover to try and scoop air in and pressurize that area. That's when he bought,and I followed, Monarchs and problem solved.Just proves that I could do something and it works and you could do the same exact thing and end in failure----guess that's the way of the world.

180Marty wrote:...My friend/mechanic had a 1955 180 and he was having vent issues with the original caps like hotrod has. My friend went so far as to make a couple of holes in the front of the domed cover to try and scoop air in and pressurize that area. ....

To be clear, I do have the original caps with covers but I have no venting issues.
Only trouble I had was the springs were broken in the cover latches.
New latches = all is well.

I wonder if your friend was having venting issues due to bad caps.
AD 79-10-14 was issued to address inadequate fuel tank venting,
and required the addition of vented fuel caps to supplement the stock vent.
This was a wide-reaching AD, applicable to almost all high-wing Cessnas.

http://rgl.faa.gov/Regulatory_and_Guida ... t=79-10-14

To tell you the truth, I can't remember if his problems occurred with the top of the cabin vent or when he updated to the behind the left wing strut vent. I do remember that his gas gauge would indicate full after flying awhile and he thought the bottom of the bladder was coming off the floor of the wing bay it is in. Made no sense to me but after he installed Monarch caps he had no more problem.

I will have new monarch caps, bladders and sending units to install in a few weeks on my 182. I don't suspect i will have any issues but i will give a report of the install if anyone is interested.

PAMR MX wrote:I will have new monarch caps, bladders and sending units to install in a few weeks on my 182. I don't suspect i will have any issues but i will give a report of the install if anyone is interested.

Just to be clear; you have new Monarch cap assemblies, Hartwig fuel bladders, and McFarlane senders?

If you have the time maybe shoot some photos of a brand new Monarch cap assembly from the side, curious about the gap between the bottom of the umbrella and the surface of the mounting plate.

Also, if you're feeling scientific turn a cap assembly upside down on the bench and fill it with gas, see if any leaks by the seal.

I'm still firmly of the opinion that there is some operator error involved in these stories of leaking Monarch caps, either the thing is creating a tight seal at the top of the tank or it is not, there's no in between. If it's not creating a tight seal then it needs to be fixed, just like any other cap.


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I second the test to see if it leaks by installing the cap in the plate and inverting with liquid.

I'm still firmly of the opinion that there is some operator error involved in these stories of leaking Monarch caps, either the thing is creating a tight seal at the top of the tank or it is not, there's no in between. If it's not creating a tight seal then it needs to be fixed, just like any other cap.

X2

PAMR MX wrote:I will have new monarch caps, bladders and sending units to install in a few weeks on my 182. I don't suspect i will have any issues but i will give a report of the install if anyone is interested.

Please do.

I will do it.
The monarch caps had been on back order for months. I should be getting them soon.
My fuel cells are original from what i know. I got them from floats and fuel cells. I have always been very impressed with their quality and fit compared to some of the other guys.

[quote="Halestorm"}....Also, if you're feeling scientific turn a cap assembly upside down on the bench and fill it with gas, see if any leaks by the seal....[/quote]

I didn't try the seal, but tried this test on the flapper. It didn't hold shit.
So if gravity can get gas by the flapper, what will a siphon do as when the fuel cap is left off?

Halestorm wrote:...If you have the time maybe shoot some photos of a brand new Monarch cap assembly from the side, curious about the gap between the bottom of the umbrella and the surface of the mounting plate....

Here's a phot I took last year.
This is a new, never installed cap assembly, but I don't know when it was produced as it came with my 180 when I bought it.

Is the flapper still intact since I can see the chain out the bottom? My flapper still holds fuel after all these years when I shake Mr Funnel