The Why of CiES

For pilots and aircraft owners of general aviation aircraft, it’s been a historical challenge to measure fuel level in the air.  Every time a pilot scans their fuel gauges, they want to assess the state of fuel remaining in the aircraft.   To give a pilot  better decision making tools in flight, functional fuel gauges are a minimum requirement.  For this reason the FAA mandated operational fuel gauges for all flight operations.  This capability is critically true if you want to utilize the maximum safe range of your aircraft.

The main problem pilots face is misleading information provided by traditional fuel quantity instrumentation. Even if a pilot knows the fuel gauges to be erratic, they still can lead to bad decision making.  Today, their best option is measuring fuel before flight.  This measurement is  typically made with a wooden stick or glass pipette.  Pilots use this starting known fuel level  and keep track of consumption in flight, but of course, they still run out of fuel.  One key factor missing in this method is knowing exactly among the multiple tanks on the aircraft, just where is the fuel located.    Let's be frank using a stick in a modern aircraft illustrates that we have given up on ever making the fuel gauge work. 

With a bulk of the general aviation aircraft aging beyond 40 yrs, the problem is only get worse over time.

If only there was a better way to measure fuel quantity in the air, then pilots could make better decisions regarding extending flights, balancing tanks or making an extra fuel stop.  This capability would lead to less fuel starvation or exhaustion events and better piece of mind.  With 400,000 general aviation aircraft flying, there is a clear opportunity to meaningfully impact safety on the breadth of worlds general aviation pilots.

Lightning Safety - Fuel Senders

Lightning Safety - Aircraft  Fuel Quantity Senders  

It is required to provide in-flight lightning protection in all types of fixed/rotary wing and powered lift aircraft of conventional, composite, and mixed construction and their electrical and fuel systems.  The design of adequate lightning protection for aircraft fuel systems is one the most important lightning protection tasks to be accomplished. 

Government airworthiness certification requirements stress fuel system safety because this system has been responsible for most lightning-related aircraft accidents. 

Elements of the fuel system are typically spread throughout much of an aircraft and occupy a significant amount of its volume They include the fuel tanks themselves, associated vent and transfer plumbing, and electrical controls and fuel quantity instrumentation. 

Careful attention must be paid to all of these components  if adequate protection is to be obtained. The main objective of fuel system lightning protection is to keep ignition of fuel from destroying the aircraft 'during a strike. This goal is quite challenging because thousands of amperes of current must be transferred through the airframe when the aircraft is struck by lightning and a tiny spark of less than one ampere may release sufficient energy inside a fuel tank to ignite the fuel vapor and initiate an explosion. 

There are 4 methods of preventing aircraft fuel hazards from lightning:

1. Containment - The expansion due to the explosion is contained without structural issue.
2. Inerting - Introducing nitrogen into the fuel tank. 
3. Foaming -  Fuel permeable foam like are cars 
4. Eliminating Ignition Sources

CiES Magnetic Field Fuel Quantity Design embraces #4.   CiES simply eliminates the wiring and the wiring hazard from the fuel volume.    The wiring and fuel sensor element are kept completely out of the fuel volume, if the sender is mounted to the tank surface.   

This methodology eliminates any electrical ignition source from the fuel volume.  

While this issue has not proven to be an issue with some fuels namely AVGAS - lightning induced ignition of fuel tanks containing gasoline is not an unknown phenomenon as demonstrated below in Ohio

So while lightning indirect and direct effects are addressed for the wiring.   Induced effects become paramount for good design.  

Arcing and sparking within the fuel vapor space of a fuel tank is one of the primary concerns of the fuel quantity system designer. The distinction between arcing and sparking is worth reviewing. Arcing is the result of current through the interface between two conducting materials which are making limited electrical contact. Such a condition may exist at the interface of two moving metal components like the CIES rotor and pivot or between the arm and the internal tank surface as shown.

A spark, on the other hand, is an electrical die-charge resulting from a difference of potential across an air gap or along a dielectric material. This condition may exist, for example, in the CiES fuel sender as the metallic components are anodized and teflon impregnated for corrosion protection.  Current through the tank may result in difference of potential between these components. 

By insuring conductivity is maintained throughout the fuel quantity sender this hazard is mitigated.  CiES utilizes clever details to maintain corrosion protection but also to insure induced charges dissipate harmlessly to aircraft grounding structure 

Finally a fuel level sender specifically designed for the aviation market.

New Video - CiES Operation

Why do Aircraft Fuel Gauges Suck

In the 1950’s when a majority of GA aircraft were designed,  the aircraft manufacturers in the USA turned to automotive fuel senders and equivalent gauges made by the same manufacturer - AC DELCO or in some cases Stewart Warner.

Rebuilt Piper Comanche Sender 

These gauges and senders were produced by the millions for the primary automotive application Buicks and Cadillacs in the mid 1950's.  I get a sense looking at these senders and gauges now 50 or 60 yrs later that there was a sense of pride,  they did last far longer than they should have.  But even 50 yr old automobiles have issues.

The trouble with these automotive senders is that they are: 

• Made of Steel. 
• Only in production for a few years. (more of this later) 

Fuel tanks for both applications automobile and aircraft were very similar in size 

• The sender and gauge face size that were matched. The indication size allowing for  the automotive requirement to provide a warning of impending fuel starvation.

• Interesting note:  in that automotive systems are biased to show a faster fall in fuel level from 1/2 tank to zero - the Big Three were trying to keep car owners from running out of fuel.  That clever manipulation is still being used in automobiles today.

Now because aircraft are aluminum we have introduced dissimilar metal corrosion.  Steel sender body and aluminum aircraft tank or structure.

Water vapor introduced on descent is one of the reasons we sump the tank before flight.  But water vapor also condenses on the steel sender body.  Water increases the rate of galvanic corrosion.

What else is necessary, oh yeah, latent time, when the aircraft tanks sits empty waiting for the next flight. 

What is worse - is that we stuck the resistance measurement method inside this little corrosion lab - it degrades right along side the metal in the sender body and just as quickly.

Fuel senders last longer if they get the regular washing with fuel.


——

So now just for fun,  we have introduced corrosion by products into our fuel stream,  rust and rust particles threatening fuel passage.

Now with totalizers, we added a little turbine to measure fuel

We should replace the senders every so often,  yes that would be a good plan - the only issue is that that particular automotive sender is no longer made.

So to accomplish this lofty ideal you would have to wholesale replace the senders and gauges - Cessna Parts Distribution only reports 4 to 5 sales per year for a program like this.  I was told it was a single persons job for 5 years to put together this program.  Somebody thought it was worthwhile.

First for the Stewart Warner System and then for the Rochester Gauges unit (an Aluminum Body finally)

It should have been required - it should have been made into a Mandatory Service Bulletin - Actually it has and actually it is. 

Nobody pays attention to it, very few are aware it exists.  

Piper, Mooney and Beech have similar 

Fuel tanks got larger over time  and only Beech and Cessna in the Twin aircraft   increased the fuel gauge size for better recording accuracy 

———
Well where that leaves us is with marginally operational gauges that for a very good functional reason nobody would trust, as they weren’t designed for the job. 

But instead of fixing the issue, and Cessna did try and so did a few others - pilots and aircraft manufacturers  just gave up.  They gave up on new technology, they gave up on new designs. 

Who would want to fix it - if nobody cared or even though they though they didn’t need a functional fuel gauge.



So when a pilot says he trusts his watch or his unapproved  Minimum Equipment List stick or some other fancy but non-required workaround and that they state emphatically that they wouldn’t trust a fuel gauge 

• We are fairly certain they are flying with un-airworthy fuel gauges and senders that haven’t been serviced or calibrated 
• We are dead certain of the lack functional fuel indication capability in an aircraft,  when the pilot emphatically states that fuel gauges don’t have to be accurate or only accurate at zero 

The ridiculous part is that the magazine pundits agree with them, all for a system, that was by it’s very design was going to fail 

--------------------------------------------

This is the saving grace - CiES now has over 85% of the OEM general aviation fuel sender market - All of Textron Piston and All of Cirrus Piston and Jet  - and a large smattering of others 

The aircraft manufacturers, do not agree with the magazine pundits, and that should be a sobering moment.  Internally in the industry when we have discussions on this topic and the concerns are completely foreign to what is perceived by the pilot community believes.

Aircraft Manufacturers Requirements

• Aluminum Body - that has an additional element of corrosion protection.
• One less thing to introduce rust into the tank environment
• Designed for the harsh aviation environment - DO-160 Testing
• Repeatable and reliable accuracy over the aircraft life.
• Measurement method removed from the fuel volume 
• Intrinsically Safe 
• The ability to effectively stick the tank anytime in level flight
• Digital system to offer the a better owner satisfaction and reduced warranty claims 
• They wanted fuel quantity solution for life of the aircraft 

Aircraft manufacturers know that fuel totalizers, did not and do not fix fuel starvation as Cirrus aircraft in particular had several notable events 

The funny thing is that this new GA fuel quantity system can be retrofitted to older aircraft -

It has the potential to make all aviation fuel level gauges functional - more importantly TRUSTED.

Beech Customer Responses

Beech Customer Responses

I have the CiES frequency senders, with matching Aerospace Logic gauges.

Working with Aerospace Logic requires patience, but in the end, the result is really spectacular.

Yesterday, at 8500 AGL, I ran both R&L Auxiliary tanks down to 0.0 gals, at 47:35 on the clock, precisely as expected... A few seconds later... Fuel pressure begins to fall, immediately switched back to left main.  

Accuracy... It's a totally new experience. I have two fuel totalizers. One Shadin and one in my G4.  Maybe having accurate fuel gauges is overkill... But it's an overkill that I like. 

The only caveat is that my shop wasn't particularly efficient with the remove / reinstall / remove / final install / calibrate process.   I have ALOT of money tied up in this.   But I don't regret it, and I would do it again. 







For anyone who is considering CiES fuel senders these things are awesome. They are well worth the work to install. I ran all new shielded conductor up to the back of my JPI 930. Finally I have a reliable and consistent fuel measurement in my airplane. 

Wow, who would have thought accurate fuel level was possible.

If your airplane is down for an upgrade I would send your old fuel senders to CiES.   This will insure that the senders are appropriately set up the first time.   Beech in all their wisdom made numerous different senders inverting the bolt patterns on some etc. 

CiES senders can work by resistance, voltage or frequency. I would chose at a minimum voltage if you can, Frequency is even better.
Scott @ CiES knows his stuff.


----------------------------------------
The cost to retrofit CiES senders to a pre-74 B55 is around $3200 (plus installation). That may seem "outrageous" but it's only about 50% more than what it costs to have the eight (2 per tank * 4 tanks) senders "overhauled" and my experience with overhauled senders is not very good. At best the overhauled senders will perform as good as when new for a few years which is to say they're accurate to within about +/- 5 gallons.

Properly calibrated the CiES senders appear to be within one gallon.  In a Bonanza with two 40 gallon tanks or a post 1973 Baron there are only four senders so that cost is cut in half.

 IIRC the last time I checked, new (1940s technology based) senders from Beech were around $1,600 each or over four times what CiES charges.

-----------------------------

+1 on the CiES/ Scott Philiben Phan club. There's no better customer service than that provided by Scott. anywhere.

I'm still VERY happy with my CiES senders. You know, when something "just works", you take it for granted.   I don't really give my CiES senders much thought. 

They're underappreciated little heros quietly doing their job. Perfectly. All the time.

------------


 
AIRCRAFT FUEL GAUGES THAT YOU CAN TRUST 

"With over 12,000 units now flying, CiES has taken over the OEM fuel level sending field.   Our combination of outstanding quality,  reliability, and accuracy has made CiES the standard and the runaway industry leader for fuel level indication on all aviation platforms, GA, Utility, Rotorcraft for both reciprocating and turbine engine applications " 

A New Day has Dawned in Aviation

General Aviation News Photo

“Getting this STC done has created the roadmap for us to continue on,” said Pelton, noting that other STCs may involve fuel systems, autopilots and more."  General Aviation News 

We have made great strides in replacing legacy fuel quantity indication in GA aircraft and Jack Pelton's comment above, indicates the importance of improved fuel quantity indication in the roadmap to improving the equipment on legacy GA Aircraft.    

Today's EAA STC news announcement opens up the literal Pandora's box of opportunity.

Actually our FAA TSO approval allows us to move even faster into getting universal approval for installing better fuel quantity systems in GA aircraft.  

The TSO approval insures that we have met both the new ASTM standard for Verification of Avionic Systems but also the RTCA DO-254 Design Assurance Guidance for Airborne Hardware as well as the DO-160 standard for surviving the external environmental conditions found on the wing of the aircraft 

This is a major step forward and was not anticipated after the Part 23 Rewrite NPRM.  

The new ASTM Standard makes it much easier to show compliance with organization, definition &  verification of our software.   

Utilizing a smart sensor was key to CiES obtaining the outstanding aviation fuel level sensing results.  

This quality indication is one that thousands of pilots rely on,  flying brand new Cirrus, Vulcanair, & Quest aircraft.  

Contact CiES as we are adding fuel quantity sensor configurations for thousands of single engine and twin aircraft. 

• Cessna
• Beechcraft 
• Piper
• Cirrus
• Brittan-Norman
• Fairchild 
• Technam

Aviation Fuel Level Indication - Customer Responses

Customer Responses

The cost to retrofit CiES senders to a pre-74 B55 is around $3200 (plus installation). That may seem "outrageous" but it's only about 50% more than what it costs to have the eight (2 per tank * 4 tanks) senders "overhauled" and my experience with overhauled senders is not very good. At best the OH senders will perform as good as when new for a few years which is to say they're accurate to within about +/- 5 gallons.
Properly calibrated the CiES senders appear to be within one gallon.  In a Bonanza with two 40 gallon tanks or a post 1973 Baron there are only four senders so that cost is cut in half. IIRC the last time I checked, new (1940s technology based) senders from Beech were around $1,600 each or over four times what CiES charges.

I'm having a hard time seeing anything "outrageous" with CIES pricing.

---------

And one additional point about CIES senders. I have absolutely no doubt if any question or issue came up, Scott would be on the phone within the hour. (More likely in minutes.) Every interaction I have had with him and interactions I have seen others have with him have been very positive. 

Phone or email he's always been very helpful.

------------

+1 on the CiES/ Scott Philiben Phan club. There's no better customer service than that provided by Scott. anywhere.

I'm still VERY happy with my CiES senders. You know, when something "just works", you take it for granted. I don't really give my CiES senders much thought. They're underappreciated little heros quietly doing their job. Perfectly. All the time.

------------


 
AIRCRAFT FUEL GAUGES THAT YOU CAN TRUST 

"With over 10,000 units now flying, CiES has taken over the OEM fuel level sending field.   Our combination of outstanding quality,  reliability, and accuracy has made CiES the standard and the industry leader for fuel level indication on all aviation platforms, GA, Utility, Rotorcraft for both reciprocating and turbine engine applications " 

Customer Responses - CiES Non-Contact Fuel Level

Cessna 177

Hi Scott,Our senders have been working perfectly with the Aerospace Logic gauge since installation last August. Thank you for your outstanding support in helping us work through an unrelated ground wire issue in the plane.Gregg Ridder

Mine have worked flawlessly since installation, and the accuracy appears to be extremely good. Hopefully someday I’ll be able to quantify that accuracy. I sure wish other aviation vendors cared about their customers like you do. Jerry Olson, 76 C177RG

Hey Scott,
I presume you got the original frequency senders back by now? The new ‘voltage’ type senders are working fine with my old(er) JPI 930. I did calibrate them (again) when installing them, however, they fail to indicate the full 30.5 gal on each side on the 930 when ‘full’ (JPI’s display units do not show partial gallonage). Most times the 930 reads 29 each side when “full” (full is over 30.5 gallons each side, sometimes QUITE a bit more). However, when I fill up, I can tell you the amount put in + the 930 readout of what’s left is almost spot on, close enough to more closely calibrate my K factor in the 930 installation (it’s still off quite a bit). I also double check with my fuel dipstick. And I did level the plane while calibrating, even though the Cardinal cruises nose down, so calibration methods give differing results depending on nose strut extension, attitude, cross level, etc.
Any my 930 still shows the digital amount remaining.
So I’m happy. Much better than the OEM stuff and those original gauges.  And it will get better with more flights.
Too bad you can’t get JPI to include your senders when new fuel reading units are ordered.
Marc, 76 C177RG 

Everyone, Mine are installed (Bob Russell) and interface properly with the JPI 930.  Fuel readings seem to be extremely accurate.  I can read the remaining fuel from the JPI, and then stick the tanks for a comparison.  So far, readings are within .5 gal of what I measure.  Scott, excellent product.  Thanks for supporting CFO and members.Alan, C177RG

Beech Baron Digital Fuel Sender Retrofit Part 6

Beech Baron 58 Fuel Level Senders

CIES Baron 58 Fuel Quantity Senders

\

We have some results back on the Baron 58 Senders.    There was a slight glitch as the middle left sender somehow got caught on the initial calibration.  But that was rectified easily   

The result was a fairly simple curve with no major discontinuities - Nice Job.

Even better we got a good result in the air.  

We got the middle float unstuck on the left side, it was helpful that with a frequency output graph that you could pinpoint the problem remotely like that.

After it was free, we mirrored the calibration numbers on the right side with the offset we had from the first reading and They  seem very accurate,  within a gallon of the totalizer on the JPI 960.

Tank calibration curve

We put lots of work on this aircraft... we did air conditioner, new engines, props, & avionics.    The owner has flown in it,  but we are still tweaking and breaking in the new engines for him.   

So a gallon or so off of the totalizer on a 150 gallon aircraft -  Not bad at all. 

Legacy Beechcraft Senders

All dimensions for these new senders  were captured from a legacy set of Beech Baron 58 Fuel Level senders.  As the CiES design constraints are different from the legacy senders - there are a few little tricks to getting the right geometry in the tank 

For this short flight fuel level is in green and fuel flow in blue.  You can see the effects of pitch change on fuel level on takeoff and landing. But you can also see the steady drop in fuel level over time.


This was our first multiple sender summing aircraft and we are very happy with the result. 

We were looking forward to this system in the aircraft as it represents a chance for us to utilize the capability of summing multiple senders to achieve a single digital fuel tank output.  

Every day we see that we can meet or exceed  the 0.75% most stringent TSO quality standard.  In the case of the Baron - that would be 0.66% accuracy for fuel quantity. 

Beech Baron Digital Fuel Level Sender Retrofit - Part 5

Beech Baron 55 Fuel Level Senders

We have now produced the Baron 55 Senders.  These senders are fully TSO'd and presented our largest challenge to date as each sender had a unique peculiarity.

We will wait for confimation in the aircraft that all is well as we did for the Beech 58 senders we completed two weeks ago 

We are looking forward to this system in the aircraft as it represents a chance for us to utilize our capability of giving a multiple tank system, Mains and aux tanks accurate fuel level.

Stay tuned for further updates and pictures.

Britten-Norman Islander Fuel Quantity Senders

Britten-Norman Islander Fuel Quantity Senders  

We just completed a set of Britten-Norman Islander senders for the manufacturer.   

We placed the old Britten-Norman sender design alongside the CiES design for contrast.  Like a lot of small aircraft manufacturers, Britten-Norman had to modify commercial resistance senders to work in their application until we came along.

If you look closely you will see the careful welds on the legacy sender float arm and if you look inside you will see tank sealant applied to the riveted and electrical connections to prevent fuel leakage through the sender body.

The CiES fuel level sender is built for the application, with a custom arm dedicated to this assembly.  Our non contact fuel quantity measurement insures that leakage will not happen through the sender body.  

All of our sensor electronics are fully enclosed in the aluminum housing.  Unlike traditional failure prone senders - our senders have amassed an impressive record of 300,000 hrs of flight time without error or in service replacement.   We will change your opinion of what float fuel senders are capable of - both from a precision and reliability standpoint.

Finally a fuel level sender designed for the aviation market.

What if We Legislated Accurate Aircraft Fuel Level

Yes Virginia, Bad Fuel Level Indication Can Lead to Aircraft Fuel Starvation.

If you look at the small aircraft fuel starvation/exhaustion statistics you might make an assumption that aircraft might have poor fuel quantity indication systems and you might be exactly right.  What is more astounding is that the FAA will agree with you and put it in writing.   Three to four aircraft a week find a way of running out of fuel in North America.

But if you ask a pilot - they will probably equivocate and  shift the responsibility for these fuel starvation events elsewhere. 

So let's look at some of the basics:

Every transportation system, save small piston and turboprop aircraft in North America,  when you evaluate fuel starvation from a functional hazard assessment, indicate that a failure or inaccuracy of the fuel indication is a causal factor in fuel starvation.  

Lets look at the closest brethren to small aircraft - our commercial aircraft cousins.

 

In large commercial aIrcraft fuel quantity indication has been determined to be a leading factor in fuel starvation - The example of the Gimli Glider a Air Canada Boeing 767 that suffered fuel exhaustion and glided to a landing was due to erroneous fuel loading calculations and fuel-gauge malfunctions.

The aircraft's fuel gauges were inoperative because of an electronic fault which was indicated on the instrument panel and airplane logs (the pilots believed the flight was legal with this malfunction)

In an Aviation Week Article in Nov 2011 

EASA Proposal Targets Fuel Starvation Risks

Lessons learned from 65 transport aircraft fuel starvation incidents and accidents in the past four decades have prompted the European Aviation Safety Agency (EASA) to propose certification rule modifications designed to mitigate the occurrence of similar incidents. 

The notice of proposed rulemaking (NPA-2011-13) issued this summer would modify EASA's certification specifications for large aeroplanes (CS-25) by requiring the installation of fuel identification systems, replacing the currently required fuel quantity indicators for each fuel tank. The new systems would have to permanently display to the flight crew the total quantity of usable fuel on board as well as in each fuel tank. provide low-level fuel warnings for each tank, and warn the crew of an airplane configuration that, if left uncorrected, would starve one or more engines of fuel.

In this case EASA would like to improve aviation safety by putting in a better fuel quantity indication system in Commercial aircraft to address the Fuel Starvation hazard.

Not so in General Aviation, Let's look at how AOPA handles this same concept.

• Know how much fuel you have onboard. 

• Think of Fuel not in Gallons but in Hours and Minutes.
• Use a calibrated Dipstick and your Fuel Computer (Trip Computer)
• Depart with Full Tanks

• Know your fuel system 
• Know what kind of fuel is in your tank
• Update your status during flight
• Land with adequate reserve

In this helpful Fuel Awareness White Paper somewhere at the end

• Finally "some sort of Fuel indication is provided for the pilot" 

So nowhere in this paper does the AOPA tie the fuel you have onboard your small aircraft to your fuel quantity instrumentation in the aircraft.  Instrumentation that is designed to let you know your remaining fuel quantity, nowhere. 

It is a fact that a working fuel indication system should help you determine how much fuel you have all the way through your flight. 

Why do we tolerate this in General Aviation Aircraft.  

By FAA regulation you are supposed to have Fuel gauge for each and every aircraft tank. When you take delivery of a new aircraft you should expect the following from your fuel indication:  Part 23

• This gauge is to read from Full to Empty 

• Where Empty is the least fuel you can safely use.

• This gauge is to be marked with Numbers and what these Numbers represent i.e. Gallons.

There is no other performance standard for this gauge and even for large commercial aircraft the fuel indication regulation reads exactly the same.

In commercial aircraft the fuel indication system typically meets a TSO Standard which is a numerical quality standard for indication.  Maintenance is required to show that this system is maintaining that standard. 

Here is where it get's lost in the General Aviation world.  There is no quantitative  (numerical)  performance standard in the regulation.   The fuel quantity system does not typically meet a numerical performance TSO standard.  In fact it has been stated, that it only needs to be accurate when you are Empty.   This statement is not folklore its printed FAA policy and guidance. 

The  FAA Position - We don't really have a usable standard, it's up to you. 

The follow on regulations for the pilot and mechanic are equally vague and fuzzy and they are as follows: 

Pilots need to have a working fuel gauge indicating the quantity of fuel in each tank.  Part 91

Mechanics need to insure the following under the aircraft's mandatory yearly maintenance: Part 43

• Check for poor condition

• Check that the gauge is properly secured to the aircraft

• Check to insure the markings are clear 

• Check (where practical) for improper operation 

So we have a  touchy / feely standard for what constitutes a working fuel gauge in general aviation.  

If we peer into the maintenance manuals - this aviation requirement is equally spongy and strangely consistent for every small aircraft manufactured.   

Most aircraft manufacturers have issued Service Bulletins outlining a calibration procedure that could be accomplished to insure the system is somewhat accurate, but is not required.

There is no quantitative standard for for small aircraft fuel gauge accuracy and no quantitative standard in the field to determine if the fuel gauge is providing useful information to the pilot.

 Actually accuracy is left up to the personal discretion of the pilot and their mechanic to a personal definition of "working" and "improper operation".   This is obviously a purely qualitative evaluation.  

Remember:

 If you can't measure it 

you can't manage it.

Let's look at an example of  how small aircraft fuel indication should be handled:

The Australian Civil Aviation Authority came upon this lack of a consistent standard and decided to do something about it.   The Australian fuel quantity performance standard has to be met 4 year intervals.   This testing is mandated by law and very similar in result to an FAA or EASA AD.  You must comply, but it deals with forcing proper maintenance and not addressing a manufactured design defect.

This mandatory repetitive compliance testing has a clear qualitative standard that is traceable back to the FAA requirement and the underlying Society of Automotive Engineering requirements for fuel indication in aircraft.  

The standard is flexible enough to account for aircraft that have rudimentary sight gauge indication systems.   

Even more impressive is that this standard is combined with an element of best practice to insure an aircraft has accurate fuel level indication for the pilot to use.

Basically these standards are :

• That the Fuel Gauge progress smoothly and continuously to empty as fuel is drained.

• The Fuel Gauge reads Empty with the zero usable fuel level in the tank.

• If the Fuel Gauge is marked at major graduations for fuel quantity (Part 23 Aircraft) that the gauge indicate within a few percentage points of that marked value.

• If the Fuel Gauge is marked in 1/4 tank increments (E,1/4.1/2,3/4, F) that a placard be placed along side the instrument to list the numerical volume associated with that mark. 

Simple and straight forward, Why don't we give it a try.