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.


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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.

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+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.

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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 " 

Beech Baron Digital Fuel Sender Retrofit Part 6

Beech Baron 58 Fuel Level Senders

CIES Baron 58 Fuel Quantity Senders

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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. 

Cirrus SR22 Fuel Level Retrofit

Feedback on the the CiES system....

While my aircraft (NA G3 #3813 Perspective) was at Leading Edge Aviation in Tampa for an annual, I had the CiES digital fuel system installed. The crew at LEA had recently received the benefit of Scott Philben's tutelage on the intricacies of this installation, and I was in line next for the retrofit. Two points of observation:

From This

1 - Fuel quantities are now precise and crisp. No longer do I tend to disbelieve fuel gauge indications because of erratic needles.

 Now there is no "negotiating" with myself of how much fuel I probably have. The installation includes calibration at 2 gallon intervals from "Zero Fuel" empty to full.  In my opinion, the replacement round gauge on the center panel is superior to the Perspective MFD indication.  Fuel quantity and balance is abundantly clear.

To This

2 - Choice of shop doing the work is very important. With the changes in wiring harnesses among all the iterations of Cirrus aircraft, there are a several unique and significant distinctions for each application. You need a knowledgable, detail-oriented, and thorough installer. I was fortunate to have one at Leading Edge Aviation.

Contact Steve Miller if you want this job done properly.




Finally, thank you Scott Philben for extending the OSH incentive, motivating me to get this system in my airplane. After seeing the results, I think the discount I received should more appropriately have been a premium paid to you. 

Aircraft Fuel Gauge Accuracy

Fuel Sensor Accuracy 

The following quoted from reference 2.

This FAR Part 91.205 fuel-gauge requirement can be seen as a corollary of a more general and more fundamental point, namely the importance of taking a layered approach to safety.

For any important task, you want to have multiple independent ways of dealing with the task, so that each way can serve as a cross-check and a backup for the other(s).

For example, the right magneto is a backup for the left magneto.  Similarly, pilots are trained to never overemphasize or underemphasize any particular instrument, but rather to scan all the instruments, cross-check them, and use all available information to build an understanding of the overall situation.

When we apply this idea to fuel, it means you should have multiple independent sources of information about the fuel quantity. 

Good sources include:

• The preflight measurement in combination with an estimate of the fuel-burn rate and the elapsed time.

• A fuel totalizer or totalizer function on the MFD.

• The fuel level gauges and by corollary the fuel level sensors

No one source should be overemphasized at the expense of the others.

Remember that having two magnetos doesn’t just make the engine twice as reliable; it makes it thousands of times more reliable.

Using gauges as a backup to a visual preflight, flight planning and totalizer makes fuel exhaustion vastly more unlikely.

CiES Inc builds accurate and reliable fuel level sensors - 

References

1.

“Pilot-In-Command Decisionmaking” (Chapter 21 of See How It Flies) http://www.av8n.com/how/htm/decision.html

2.

"Aircraft Fuel Gauge Accuracy" http://www.av8n.com/fly/fuel-gauges.htm

Aviation Fuel Level

Traditional Aircraft Fuel Sender 

Why don't my fuel gauges work?

Let us cover a few basics  

• Aviation industry has utilized level senders from other applications
• Aviation is not the largest market or the most financially rewarding for a dedicated fuel level sensing solution.

• Aircraft fuel tanks are larger than those for most other applications. 
• An aircraft carries more fuel.

• An aircraft has three degrees of motion freedom 
• The liquid fuel is free to move about.

There are other factors.

• Why not design a new system 
• Fuel Level Intellectual Property is hotly contested territory (a patent minefield) 
• A new aviation design must avoid other patents 
• The market share is small
• The perceived liability - Top 5 aircraft incident issue

• Fuel Level in Aircraft needs to be "Intrisically Safe".
• Explosion Proof 
• Limited Spark or Heat Energy in the fuel tank. 
• Non - Contact "The best solution" for Intrinsic safety is the hottest IP in Fuel Level
• Required for multi fuel and hybrid vehicles
• Required for vehicles with long term fuel storage - i.e. Boats
• Required in LNG / LPG

------------------------------------------------------------------------------------------------------------Fuel sending works in my car.

• Automotive fuel tanks are smaller
• What would be adequate for a resolving 16 gallons of fuel has difficulty with 3 times the volume.   
• If you have a boat - this is also an issue as you are well aware
• The variable resistor technology used in automotive applications doesn't scale well
• The variable resistor cards used,  allow 60 degrees of travel  - a good resistive card for aircraft or boats would require minimum. 180 degrees or more.

• Relatively stable fluid motion 
• The automotive sensor is exposed to some fluid motion but overall less. 
• Aircraft fuel can remain quite stable - however turbulence will creates concentrated fluid motion.
• This motion wears the resistive trace - so inadequate resolution of the variable resistor is now faced with increased wear.  From bad to worse.

• The basic requirements 
• Standard aircraft fuel gauges are calibrated only for the full and empty position.
• Caveat - new automotive systems are calibrated to the tank - great improvement
• Caveat - new aircraft MFD's allow tank calibration - Aerospace Logic, JPI, Garmin

• Almost daily use  
• The automotive sensor is continually washed with new solvent at every filling and fuel fills are more frequent. 
• Aircraft fuel can remain in the tank for long periods - it is designed to do so - however impurity buildup on the variable resistor are common at a fraction of usage time of the automotive application.
•  it is quite common to have your aircraft senders ultrasonically cleaned

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Propane Level Gauge

New requirements for intrinsic safety for all aviation fuel level systems 

• The general aircraft industry found that they could utilize a commercial off the shelf, patented float sending unit from the propane industry
• This met the new safety requirements and directly replace a float level legacy system.

• A Non- Contact solution - the resistance card was removed from the tank environment.
• Shock inputs from turbulent air can however de-couple the matched magnetic drive and the the gauge will take a set but in-accurate reading or drift back to the correct reading.
• Suffice to say - Propane Tanks were not meant to fly

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Aircraft Capacitive Sender Ad - 1948

Alternatives  - 

Capacitive Senders -

Conceived in the Late 1940's this aircraft fuel sending system set about to address the two most common issues presented above - fluid motion and resolution of the larger fuel quantity.   

These are the most widely used in aircraft above 12,500 lb 

Capacitive Sensor Benefits 

• Immunity from fluid motion 
• Greater resolution of the large fuel volume 
• Shapable to the fluid volume - tailored to the tank volume.

Capacitive Sensor Issues

• Difficult to Prove Intrinsic Safety
• The definition of the sensor is to utilize two metallic or conductive elements in the tank 
• The intrinsic safety requirement must be met with increasing the complexity of the system.
• It is a spark in the capacitive sensor that initiated the explosion in TWA 800 fuel tank. 

• Moisture Rejection
• An aircraft fuel tank breathes on ascending and descending - moisture in the air is constantly brought in contact with the fuel.  Sealing the tank is not an option.
• As the capacitive utilizes the fuel contents as an integral element of the level reading - this variable is very difficult to manage.

• What's in the tank - matters a great deal 
• Fuel must be:
• uniform 
• moisture-free
• stable and uniform temperature
• contaminant free
•  to give a consistent and accurate fuel level indication 

When you review the system above - the capacitive sender solved several issues with fuel level indication, however it brought a few of it's own limitations along for the ride.

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Ideal Aircraft Solution Characteristics

• Non Contact - New FAA Requirement
• Intrinsically Safe - 
• The alternative is proven safe electronics in the fuel
• Immune to fuel contamination

• Unaffected by Fluid motion 
• No wear items related to fuel level reporting

• High Resolution 
• Address the larger quantity of fuel in aviation systems.

• Simplicity 
• The best aviation solutions eschew complexity where a simple system provides equivalent benefit.

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CIES Inc AMR Fuel Level 

Float Based Level Sensing - Retrofits or directly replaces most units in the field

• Non Contact 
• No - Safety Issues 
• No - Fluid Contamination
• No - No moisture or fuel quality issues

• Immune to Fluid motion
• No wear of fuel level reporting system

• Resolution 
• Digital output
• More fuel level information 
• Integrity of the level signal
• Interfaces to modern avionic solutions
• Ability to output fuel temperature - Lbs fuel. 

• Simplicity




• No complexity required
• On the platforms we have been applied - exceed it's requirements

CIES Inc AMR  A sensor that was designed for and patented with the aviation industry in mind, but suitable for all high value applications.

Why Anisotropic Magneto Resistive

Why use Anisotropic Magneto Resistive Sensors 

Anisotropic Magnetoresistive (AMR) Sensors Technology used by CIES Inc  for our fuel level solutions   These sensors use the basic premise that the electrical resistance of certain ferromagnetic alloys, such as permalloy, are influenced by external magnetic fields.

Like a compass that always points North no matter how you move - our sensor always points to the float.

For larger fuel tanks like those in aviation or marine applications  - we need more information or position information to correctly depict the amount of fuel in the tank.  Our sensor technology does this we can measure tiny fractions of a degree. So not only pointing North but also with a high degree of precision.  In fact we have thousands of discrete data points to measure fuel level.

Automotive resistance sensors re-configured for these critical applications - are just not adequate.   60 discrete points might be good enough for 18 gallons - but it falls short  handing 5 times that volume - plain and simple.  The 60 or so discrete points found on thick film resistance cards just don't cut it.  Fuel movement found in aviation and marine applications adds additional problems to resistive senders - float motion out of of the pivot plane tends to make the resistance wiper act as a make and break switch.

These compromised systems attempting to scale current automotive ceramic resistive elements by adding a longer float arm or other measures - simply provides poor performance.  

CIES Inc Patented Method

Utilize a solid state magnetoresistive effect or anisotropic magnetoresistance can be fabricated in thin film technology, allowing the production of a very precise yet cost-effective angular measurement sensors.  Replace the coarse variable resistor with a solid state device.

From Wikipedia: 

Anisotropic Magneto Resistive - (AMR) is the property of a material in which a dependence of electrical resistance on the angle between the direction of electric current and orientation of magnetic field is observed. 

Why is this a better way to measure fuel 

It works under all conditions, temperatures and with moving fluid volumes - PROVEN IN AVIATION 

And there is a combination of influences but for an AMR sensor the built in 

strong magnetic external field attached to the float arm locally saturates the sensor, the actual magnitude of the local field strength has no impact on the measurements. - Remember temperature effects on both the magnetic strength and the efficiency of the sensor.

Only the direction of the field is evaluated.

Only the local magnetic field on the rotor has influence - the presence of other nearby magnetic fields such as motors will have no effect on the sensor as long as the rotor magnetic field strength is dominant. 

While other magneto resistive sensors are available - AMR has the capability to work under all conditions and give proven repeatable results. 

Non-contact fuel level sensing is a good idea.  It was a good idea to remove the electronics from the fluid measured.

Other fuel level reporting systems don't measure up


SUMMARY OF AMR ADVANTAGES

• Voltage in the case of our AMR sensor is converted to a bit stream digital output.
• More information for every degree of float travel
• Independence of magnetic drift during lifetime
  
• Independence of magnetic drift with temperature
  
• Independence of mechanical assembly tolerances
  
• Independence of mechanical shifts caused by thermal stress 

Digital Fuel Sender Now Certified

Digital fuel sender now certified

The AOPA Press Release came out today
It seems to be difficult to find, but it is on the web

The basic concept is ....


When we have specific aircraft (or aircraft type) information
and we demonstrate that the system is compatible to Transport Canada ... Flight Test
or operation under 337 Field Approval

We can add those aircraft onto the blanket AML STC owned by Aerospace Logic.

We believe after we demonstrate on several aircraft types that this is simple modification and installations are straight forward  additional aircraft models will fall into place.

Fuel Management

Fuel Management

“From an accident prevention perspective, fuel mismanagement is one of the most frustrating problems. The accidents are easy to avoid. The hardpart is reaching the pilots who are most at risk, because they’re not the ones attending safety seminars or taking online courses. A new approach is needed to get pilots to stop and think about the issue. Airing some ‘dirty laundry’? Perhaps, but we think it’s more than justified by the lives, aircraft, and dollars we lose to this problem every year. 

ACCIDENTS do far more damage to GA’s reputation than educational efforts to rectify the situation.

It shows that, the pilot community,  is making a good faith effort to address the problem.”

—Bruce Landsberg, President, AOPA Foundation

Fuel Management Accidents

Fuel management accidents are among the most preventable types of GA mishaps, and yet pilots still manage to turn perfectly good airplanes into impromptu gliders at an alarming rate well over two per week in the US.

The primary way GA pilots manage fuel on board is to do arithmetic.



 You look at the length of your trip, the winds, read some performance charts, then bust out your calculator or whiz wheel  to figure out how long it will take you to get to your destination at what fuel burn. I might get anywhere from 10 to 18 miles per gallon on a flight. And if the headwind is stronger than I expected or I'm routed the long way, it might take more than that. The 30 minute required reserve  is really not enough. 

FAR Part 91-151

Fuel Level Sender Video

Video Overview of Fuel Level History and Retrofit

We will start getting videos together of units in test and evaluation

Aerospace Logic Instrument Panel Interface

Here is the interface for the digital fuel level sender 

How Do You Inspire Pilot Confidence

- The Answer is Simple -

You Provide Them with Information They Can Trust 

It seems uncomplicated, ... accurate, reliable and trusted information is key to instilling a conviction that everything is going well.

Imagine a Synthetic Vision System that throws a few imaginary mountains at you, just for fun.   This would not be a system that inspires confidence.    Random false information would make a routine IFR flight more stressful and  stomach clenching even if you knew without a doubt that no mountainous terrain exists at any time in the State of Illinois.

  Conflicting information no matter how outrageous or unbelievable adds to pilot workload.

Cross checking normally reliable sources and getting similar results are the hallmarks of a good pilot.  Minor anomolies in calculation or display can be noted and corrected before a situation occurs.  To make this effective, any display in the cockpit should match what the pilot believes to be true most of the time.

In aircraft fuel level systems - reliable trusted information is hard to come by.

Pilots Trust in Fuel Sight Gauges 

Ignoring the issues of having a flammable substance with clamped connections on transparent and UV susceptible tubing or a fragile glass tube in the cockpit  - pilots trust seeing fuel as the most confidence inspiring  vs. any other method of level gauging.   If I can see it,  I have fuel and I know how much.   If I can't see it,  I don't have fuel in that tank.   I trust it, universally most pilots do.   But the limitations (high wing mostly)  revolve around the visibility of fuel  - Cessna uses a ball on the 162 Skycatcher.  But really these systems are best left in the dark.

Pilots have Faith in Capacitive Fuel Gauges

Professional pilots use them, they are the system of commercial aviation.  I hear from pilots that capacitive systems have no moving parts and are exact and reliable,  these pilots have not taken a careful look at commercial systems or the problems and solutions contained in a commercial or business aircraft system.   Good capacitive systems are expensive - the have extensive compensation for the fuel characteristics,  like temperature, water, entrained air, component corrosion These are all part of the capacitive equation for fuel level.   Good commercial Capacitance level systems compensate for this,  systems that rely on the capacitive reputation and fail to compensate or address these issues leave quite a bit to be desired.

Pilots will Believe in Anisotropic Magneto Resistive 

While more difficult technology to grasp,  digital output for fuel level from a float based system truly represents a real breakthrough in fuel level sensing.  

• It is safe, reliable - no wear parts
• There are no electronics in the fluid
• It is compatible with modern cockpit displays
• The fuel flow totalizers will match fuel quantity - giving you a truly redundant system in the cockpit.
• Provides a level output under extreme conditions

Youtube Video of the Sender under Test

How Can a Float Based Sender be so Accurate

Accuracy in Fuel Level Sensing 

Absent the aircraft substantiation that is protected intellectual property at the present time,  it is hard to demonstrate what this system does for the average pilot.  

This fuel system component will generate considerable interest, but fuel level senders of the past have been, an ineffective tool for pilots to utilize.

We can all point to or tell stories of classic flying films where the lead has - tapped the fuel gauge to see if it was reporting correctly.

A technological advancement in this field may not just improve an existing fuel quantity indication system  - but may become a new component with the potential to be disruptive to aviation safety. 

Why? 

In earlier dialogs we discussed the digital aspect of the fuel level sensor output - but what does that mean.

In the diagram above illustrates a distinct position output of the float arm as represented as a ray on the hemisphere.

The middle point being represented by the binary 10000000  - the next ray above is 01111111 the next ray above by the binary 01111110.   Each of these is different.

What this provides is a positive address for the float position for every ray shown on the diagram.

By combining a digital address to a non contact level system.  We allow free motion of the float - no discernible wear - no wear that would affect this digital output.

A measuring system with many discrete addresses over the rise and fall of the float makes it is easier to carefully describe the tank volume into usable information for the pilot.

More information allows complex tank shapes and configurations commonly found in aircraft to be described in more controlled and accurate manner.

The non-contact part of the sensor takes the fuel contents of the tank and it's varying electrical and physical properties out of the equation.  

The controlled float finds the fuel / air boundary in all flight conditions.

Legacy Systems 

Resistive Systems 

So lets compare to a resistive based float system with the resistance trace in the tank  - most general aviation aircraft in the field use this or some variation.

So the manufacturer of the fuel sender will talk about how this resistor card is laser trimmed and it has 50 or 60 precision resistive steps from empty to full when the unit is brand new.  

So that appears to be similar to the example above - yes the digital example has more steps but it is more expensive - yes.  

What is not revealed  is that the resistive steps in output are not distinct or different  - but rather a subtle step increase or decrease in the electrical property when new - after use or wear the subtleties are easily blurred or worn away.  So we in actual practice have a system that now may incur discontinuities in the stepwise output - and provide a less than adequate reading or even deceptive reading for fuel level .   

When we talk about modern general aviation aircraft and the resistance traces become much smaller as shown on the right.   The need for intrinsic safety - explosion proof requirement brought about some subtle changes in aviation fuel systems.  It was no longer acceptable to have wires or traces in the fuel tank proper.  The general aviation industry turned to propane gauges that had the wiper driven by a magnetic couple to an external wiper system enclosed in plastic.


Capacitive Systems

Capacitive Systems - this is the domain of larger aircraft and some small aircraft.  It is the defacto system for aviation.  The designs have no moving parts and are reliable in principle.

Again we are not dealing with distinct positions but an electrical subtlety between one level and another.  So while the fluid provides a good dielectric - the qualities of the fuel become a critical component in how the system works.  Therefore what you add to the tank is a measurable component for the fuel gauge system and is known as the k factor in a capacitance equation.

So what you add - Fuel -  Quality, Temperature, Composition, Entrained Air, Water and Temperature  have a direct bearing on the output of the gauge.

Components of a good Capacitive level systems contain the following:

• Probe Compensators - measure permittivity of the fuel  - ability to carry a charge
• Densitometers  to determine the specific gravity of the fuel
• Temperature compensation - direct though linear effect on k 
• Compensation of tube diameters to provide a linearized output

If your capacitive level system does not have compensation,  it has limited value in aircraft applications. 

Capacitance probes while highly developed and may utilize segregated DC or AC power, can meet requirements for intrinsic safety.   Capacitive systems however will never overcome the fact that we have separated metal tubes connected to external wiring in the aircraft.

Capacitive systems have difficulty with

• Fuel Stratfication - hot fuel added over cold soaked fuel 
• Contamination
• Corrosion 
• Indifferent fuel quality or in non aviation applications alcohol percentages

Capacitance systems in transport aircraft are redundent in that there are two systems for each tank to insure dispatch reliability for transport aircraft.  

Why Don't They Just Fix It

What is the Aviation Market for Fuel Level Sensing Technology

• Fuel Level Sensing is a very large market for other vehicle types or stationary fuel storage, aviation is a minuscule percentage of sales.

• The following companies are big players in these markets and are protective of their market share:

• Textron Kautex      -TI Group
• Wallbro                  - Robert Bosch
• Hyundai Mobis      - Delphi
• VDO                      - Toyota
• Bourns                    - Methode  
• Rochester Gauge    - Wema, Isspro, S-W

• Most of these companies are not interested in or will actively avoid the aviation market 
• Business interest to license is minimal and no interest in government controlled production
• Exposure to litigation  

• Fuel Level Sensor industry is protective of its Intellectual Property. 

• Hotly Contested Territory (It has been termed a patent minefield) 
• A thorough  patent search is required, prior to initiating a design process.
• Interest in sharing and licensing intellectual property is limited at best.

• Fuel Level Sensing in aircraft needs to be "Intrisically Safe".

• Explosion Proof 
• Limited Spark or Heat energy in the fuel tank
• TWA 800 Disaster brought about changes in FAA policy / regs.
• SFAR 88 - Wire separation from fuel system.
• Electronic Wiring Inspection System - EWIS.  

• Fuel Level Sensing in aircraft is complex. 
• Fuel can contain dissolved air - ie. Jet A 14% by volume 
• This will outgas like soda at altitude.
• This will influence simple capacitive level systems
• Aviation fuel will contain water
• The changes in altitude due to descent will suck ambient air into the fuel tank, that air will contain water vapor that will condense and mix with the fuel. 
• This will  influence simple capacitive level systems
• Aviation fuel will support biological growth and water in fuel will initiate corrosion
• Metallic or resistive components in the tank will be adversely effected and fuel level output in turn will be adversely effected.
• Fuel in aircraft is more dynamic.
• A vehicle with three dimensions of motion allows for a very dynamic fuel environment. 
• This movement will wear away resistance senders of all types and require mechanical complexities to capacitive sensors to stabilize the local fuel level.
• Replacements to 100 LL Avgas may not be so friendly to existing resistance senders in the fuel tank.

• Non-Contact Fuel Level Sensing, which meets the requirement for "Intrinsically Safe" is actively pursued and "IP" accumulated in the Fuel Sender Industry for functional and business reasons.

• Current best sensor system for Multi-Fuel vehicles
• Best sensor system for 100% alcohol fueled vehicles 
• Solves issues with partial alcohol content - corrosion
• Solves issues with de-sulfered diesel 
• Required for LNG -  LPG
• Future vehicle systems with long term fuel storage i.e.. Chevrolet Volt

• Aviation specific fuel system suppliers are not actively interested in the Non-Commercial, Non-Business aircraft application of their products or product lines.

So designing, building and certifying an aviation specific fuel level sender for aircraft under 12,500 lb is like most things in aviation. difficult, challenging and more involved than a cursory examination suggests.   It was however, not impossible.