Cessna fuel sender and fuelsenders.com

[Scott Philiben]

Dan. Good luck with that. The average is more for detecting lowering level of fuel. All of what you said is correct, however this will be an owner modification. There are better ways to handle the picofarad differences with modern electronics and processors. The dog simple butter knife example is inappropriate as fuel is a nasty environment. A gas and vented fuel tanks produce all manner of gue and this affects the so called simple system in a dramatic fashion and we are looking at picofarad differences. As a EE you are aware that fuel being used as the dielectric is nice if it was uniform - sadly it isn’t, Avgas is made up of several hydrocarbons or is it uniform temperature, or a uniform density.

I applaud your efforts in solving an erratic system in the aircraft.

 

[Daniel F. Smith]

Thanks Scott for your reply. I understand the dielectric constant can be all over the map, and especially over time, for the reasons you state. But the fundamental problem I'm trying to fix is the intermittent issues, not the accuracy. I would venture that even airlines don't have super accurate volume calculations. 2% error on 36,000 gallons (Boeing 747) is 720 gallons. It burns 5 gals of fuel per mile. About 144 miles of inaccuracy. Not bad for something that flies across an ocean.

Something interesting: the 777 uses ultrasonic sensors. What a programming nightmare! But who knows? Maybe they're all tied in parallel and produce an "average" Ha!

The difference is, we only have 50 to 100 gallons. I don't know about you, but I NEVER depend on those stupid gas gauges. They look like toys, bouncing around on the dash. And unless the sender units improve, how is a pretty, LED bar graph any different? Makes me kinda wonder if the best sensor would be a camera, inside the tank!

Well... I'll have some fun with this and see where it leads.

 

[Scott Philiben]

You wouldn't design a system to be not trusted - that would be foolish and a waste of effort. Cirrus relies on our fuel quantity system to signal the automatic switching of the fuel tanks on the SF50 Jet, failure to do so accurately and reliably would result in temporary fuel starvation and flameout. We performed a similar system for a Chinese turboprop and we are delivering an experimental system for the RDD LX7 (A rewinged and tailed Lancair 4P). The red LX7 has 190 gallons of fuel or 95 gallons per side - we keep that within a gallon utilizing fuel level as the control input.

So yes we depend and I have learned to depend on fuel gauges - It sounds strange, but there is no sound reason not to design a trusted system. You can trust fuel gauges. I live this every day.

Boeing quit on ultrasonic fuel sensing on the 777 and went to a fiber optic output capacitive system produced by Zodiac as the Ultrasonic had many operational issues on an aircraft known to have a outstanding dispatch reliability. Like any good engineer we went out in a simulated vehicle - in our case a boat, with a large plexiglass tank and we experimented with several technologies including ultrasonic, time domain reflectometry and capacitive. There is a lot of literature on capacitive so we explored future concepts. We were mindful of the new requirement to insure intrinsic safety of the sensor system (this is what lead Boeing to the failed Ultrasonic solution) We found that buoyancy worked the best - yes really it did - A camera would get confused and immersion in Avgas fuel is a bad bad thing. Bouyancy automatically compensated for fuel temp, density, fuel type
and it also provided a degree of mechanical damping biased in the proper direction- ie waves wash over the float that also only rides in the troughs. We increased the density of the float to provide midpoint buoyancy. we kept the electricity away from the fuel - good deal

Our equation for fuel level is dog simple Alfa=fuel quantity - I won't bore you with the other equations - but you can imagine with all the defining variables what the size and complexity of other equations would be

Anyway - we are fixing the King Air system by throwing the capacitive away - but keeping the gauge

I feel for your effort - but on an owner defined system a microprocessor is the way to go on improving the Pennycap system

 

[Daniel F. Smith]

More power to you if a micro can take a float system (or even capacitive sensing) and make it reasonably accurate for the GA user, without mounting incredible cost.

My humble effort is to try to use the hardware that came from the factory, even if it merely gets it back to only level factory performance. At least it will be more stable than the war stories I'm hearing.

 

[Scott Philiben]

You can, not really a step forward from 1968 when it was designed. Linearization of the tank was catch as catch can and this was true of most analog gauging of the time. Pennycap was an apt term for the system, renting the barfield to diagnose was $$$$$mucho dinero cap. An addressable lookup table addresses the non linearities and the micro allows all sorts of slosh damping routines. While the probe is stationary the fuel isn’t

 

[PaulMillner]

My A&P tells me that a bad fuel sender is the cause of intermittent readings on my right hand tank in the 172 SP. Lovely. $610 for the factory part and $75 for the gasket. (How? How does a simple rubber gasket get to $75?) I balked at the price and he pointed out fuelsenders.com and this $350 rebuild:

http://www.fuelsenders.com/site/898219/product/S3852-2

He has no experience with the shop. Putting aside the awful website, does anyone have experience with Malkasian? Are the rebuilds they provide really a better part than the Cessna/Rochester garbage part?

Consider www.ciescorp.com. Digital, solid state, no wetted working parts, very high accuracy.

I had my old senders repaired... four years later, they’re intermittent again. CIES next time around!

Makes the most sense if you’re adding fuel level to your engine monitor... but CIES can also support your stock gages.

Paul

 

[Challenged]

Insurance for my 172, with a hull value of $140K, is $571 per month. I don't know, off-hand, how much is liability and how much is hull.

Man, that's cheap. Who are you using for insurance? My premium is more than that @ 1/3 the hull value.

 

[arnoha]

Man, that's cheap. Who are you using for insurance? My premium is more than that @ 1/3 the hull value.

Actually, that was the old insurance with the old club. New club is $399 per month. Club arranges it and I'm not sure who's carrying the paper. However, I know http://zanetteaviation.com/ is the broker.

A lot of that has to do with two things about the club: a long history of very few claims (40 years) and a large number of planes insured on the policy (54). Probably going up, though. Last year was an outlier with four large claims.

 

[Dan Johnson]

Insurance for my 172, with a hull value of $140K, is $571 per month. I don't know, off-hand, how much is liability and how much is hull.

Yikes! I've had a 1957 C172 for 35 years. Paid $8K for it and Avemco wanted $1000 a year for full coverage back then. Figured I could not wreck it for 8 years so opted for $150 liability only. It's up to $260 per year now.
With your premiums vs mine, I guess I'm $70K ahead!
Thanks for the smile!

Oh yeah, we use air parts of lockhaven for our sender repair.

 

[arnoha]

Yikes! I've had a 1957 C172 for 35 years. Paid $8K for it and Avemco wanted $1000 a year for full coverage back then. Figured I could not wreck it for 8 years so opted for $150 liability only. It's up to $260 per year now.
With your premiums vs mine, I guess I'm $70K ahead!
Thanks for the smile!

Oh yeah, we use air parts of lockhaven for our sender repair.

Remember that's for commercial insurance for a leaseback aircraft. If I privately owned it, it would be closer to $1200 a year. Commercial insurance is crazy expensive. Also, I can't skip full, since I've still got paper on the plane. (Note, liability is $2MM right now, so that's pretty high, too.)

 

[3393RP]

I like Daniel Smith's post. These days it's rare to find electronic circuitry that can be sketched out and checked for proper operation.

I always enjoyed TTL work. It was kinda fun to diagnose a problem and fix it with a $1.98 IC chip. Now microprocessors and miniaturized components just stare back at me.

 

[David Kagey]

Well, pulled the trigger on fuelsenders.com and $350 for the rebuild. 1 year warranty on film-type pots, 2-year on wire-type pots. Even after that, he's charging only $100 for repair on one of his own rebuilds. $10 for the gasket vs. $75 from Cessna. Only downside is that he has nearly zero inventory, so it's a 5-day turn-around. Wish it were an exchange instead, but I'll take what I can get.

I'll update on how things go.

I know this is an old post. One of my fuel senders is bad. Tried searching on fuelsenders.com and nothing. Is he out of business? Thanks

 

[arnoha]

He is out of business. He has passed away. His son took over some of the remaining work, but my understanding is that it was to complete existing work. When that was done, no more work was taken.

It still doesn't solve the terrible design of the senders in the first place. Now that CiES senders and some other competitors exist, I wouldn't mess with repairing these things anymore. I eventually jumped on CiES and regret it not a single moment.

 

[David Kagey]

He is out of business. He has passed away. His son took over some of the remaining work, but my understanding is that it was to complete existing work. When that was done, no more work was taken.

It still doesn't solve the terrible design of the senders in the first place. Now that CiES senders and some other competitors exist, I wouldn't mess with repairing these things anymore. I eventually jumped on CiES and regret it not a single moment.

Thanks for he info. I would get CiES but a few years ago I put in an Aerospace Logic electronic gauges and the one I have isn’t compatible with CiES. They have one that is, but I would have to start over. Think I will look at refurb. Found a place Air Parts of Loch Haven. I sent him an email and will see what he says. Anyone used them in the past? If not, will just get new from McFarland. Appreciate the help

 

[arnoha]

Thanks for he info. I would get CiES but a few years ago I put in an Aerospace Logic electronic gauges and the one I have isn’t compatible with CiES. They have one that is, but I would have to start over. Think I will look at refurb. Found a place Air Parts of Loch Haven. I sent him an email and will see what he says. Anyone used them in the past? If not, will just get new from McFarland. Appreciate the help

Did you check with CiES? They recommend the digital input version of that gauge, of course. It's the better signal. But I believe they can be adapted to the stock gauges...which should mean they can be adapted to the analog input version of AL gauge you have.

I wouldn't stake my life on that info, but that was what I last heard.

 

[Racerx]

Cies senders are a labor intensive install and calibration is apparently difficult. The MacFarlane senders maybe aren't quite as accurate. But the cies aren't worth the squeeze imo.

 

[arnoha]

Cies senders are a labor intensive install and calibration is apparently difficult. The MacFarlane senders maybe aren't quite as accurate. But the cies aren't worth the squeeze imo.

I can't speak to the McFarlane product. It is only available for wire-wound (Stewart-Warner) type senders, which would be most pre-restart Cessna. Ironically, it's a film-type product, which is similar to the Rochester ones that are on the post-restart. They are definitely more prone to failure than the wire-wound. It's possible they've corrected the errors, so I won't immediately say that the McFarlane one would suffer the same short life.

At only $400 each, though, it makes overhaul of the existing senders uneconomical if you're replacing wire-wound ones. I personally would not go with refurbs, given how cheap the McFarlane are. Last I checked, the stock product is around $1200, but I haven't checked in a while. Probably higher now.

The CiES is definitely a bunch more up front. The senders are relatively cheap, but it's all labor, mostly in getting the power to the tank. The calibration is down to the experience of the shop. It's not difficult. It's actually really straight forward: Set a level, drain a gallon, repeat until empty. It is a little labor intensive, too. But a shop that's done it a couple times will have the process pretty streamlined.

End of the day, it's down to your use. In my case, the McFarlane product was and still is not a match for my plane. With my plane on leaseback and on automatic fuel to tabs and tied down, it meant a short life for the stock expensive Rochester parts right around tabs level. The CiES senders were expensive to install, but I would never again have to deal with the stock senders or fuel gauge, all of which had failed multiple times in the past. And that's been borne out: in the years since, I've had not a single failure to dispatch due to the fuel level system.

I haven't done the math for an infrequently used and hangared plane. The hangar matters because it cuts down the rocking of the plane in the breeze. It's that small motion of the wiper over time that wears out the pots. It's possible the McFarlane is a better solution for some situations.

 

[Larry Korona]

Thanks for he info. I would get CiES but a few years ago I put in an Aerospace Logic electronic gauges and the one I have isn’t compatible with CiES. They have one that is, but I would have to start over. Think I will look at refurb. Found a place Air Parts of Loch Haven. I sent him an email and will see what he says. Anyone used them in the past? If not, will just get new from McFarland. Appreciate the help

I've used Air Parts of Lock Haven a number of times (for both fuel gauges and senders) and always received excellent service and support would recommend them.

 

[NordicDave]

I just upgraded to 2 CiES magnetic senders for $545 each plus Aerospace Logic gauge. Probably never have to look at fuel senders again for another 60 years and have total accuracy across the fuel range to boot.

CiES senders match my fuel totalizer within a gallon. Nice to have such accurate cross-check.

 

[David Kagey]

I've used Air Parts of Lock Haven a number of times (for both fuel gauges and senders) and always received excellent service and support would recommend them.

Thanks. Sent them to Air Parts of Lock Haven. Turns out whatever part number mine were, they couldn’t overhaul. Suggested new from McFarland. He said he did check mine out and there was some dirt and corrosion so he said he would clean it and rest it. Tested good so he returned. Installed the other day and works perfect. Highly recommend them. Straight shooters and the cleaning at a fair price.