100% of Aircraft that Suffer Fuel Related Accidents have Non-Functional Fuel Gauges

That's a pretty bold statement.  

While the FAA and NTSB do not as a rule, evaluate or test the fuel quantity system in the fuel starved aircraft the same is not true for other national safety boards or aircraft regulatory agencies. 

These foriegn agencies and boards have determined that fuel indication plays a large part in fuel related accidents.

In fact these agencies and boards have petitioned our FAA to issue guidance or an Airworthiness Directive on the fuel quantity systems that they found to be less than functional.  

It is unfortunate - but in the aviation world we need to describe what a functional fuel gauge is.

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A Functional Aircraft Fuel Gauge has the following two Characteristics

• In level flight the indicated amount of fuel shown on the gauge should be within 3% of actual fuel volume in the tank.  

• When the fuel is at a low level demonstrated to the FAA to be the minimum fuel that can be drawn from the aircraft in all normal maneuvering flight conditions this demonstrated fuel quantity will be the "Zero" or "Empty" fuel level value.

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For reasons that we have discussed in this blog  - there are reasons and a history for why we in the aviation community treat the required instrumentation for fuel quantity different than all other required instrumentation on the on the aircraft.  

When you take a step back and look at it the context of what aircraft fuel level indication should be vs. what it is or what it has become.

There is room for improvement,  but most pilots believe that fuel indication will never change and they definitely won't rely on it.

Let's make aircraft fuel level indication functional to the two characteristics indicated above and use them to provide adequate warning of unplanned fuel usage or fuel loss.  

With this vital information available to pilots for actual fuel quantity in the tanks, pilots will make better decisions.

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. 

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.

So You Thought that "Capacitive" was the Only Viable Aircraft Fuel Quantity System - Think Again

CiES is offering the highest performance, best value fuel quantity system for aircraft.

Conventional aircraft wisdom suggests that "Capacitive" is the way to go for aircraft fuel quantity of all types.  And for various good reasons that was the case up until a few years ago.   

But that aviation maxim no longer holds water.

First a little history,  

Edward Simmonds brought the idea of aviation capacitive fuel quantity to life after observing a similar system utilized in the process industry.  A light went on, and Mr Simmonds and a Polish engineer worked out how this system could be made to work in Aviation.   This monumental work occurred at the end of WW II.  Mr. Simmonds was a master marketer and the "Pacitor" system soon became the aviation standard.  

The better story is what it took to take a stationary process fluid level system and place it in an aircraft environment.  Mr. Simmonds and more importantly his Polish engineer had a monumental task with many obstacles to reach an acceptable aircraft system. 

The capacitive concept is very simple - you place two metallic plates in the fuel volume and you utilize the fuel and remaining air or more precisely air and fuel vapor (ullage) are a component of the electrical system called the dielectric in the circuit.  This dielectric will be referred to as K factor. This is the space between the inner and outer tube identified as the electric field on the right.

Obstacle 1:    Aircraft transition from warm to cool environments readily - and this K Factor (or Dielectric) changes with temperature of the fuel  so it has to be compensated for.   This temperature shift is significant.   There needs to be compensation for the temperature of the fuel and also of the ullage as each can contribute errors to the fuel volume calculation 

FUEL & ULLAGE TEMPERATURE EFFECTS  

Obstacle 2:  Aircraft fuel is not a static uniform fluid but a combination of different hydrocarbons to meets an ASTM Standard.  Each hydrocarbon component of fuel has different K factor properties and therefore each batch of fuel will need a different fuel quantity calculation .  We need to calculate Permittivity or K factor of the delivered fluid in the tank and compare this fuel in the tank to a reference standard.  This process is necessary to obtain a deviation factor for computing the actual fuel in the tank with a capacitive sender. 

FUEL QUALITY EFFECTS

Obstacle 3:   The fuel in an aircraft especially Jet A can contain quite a bit of mixed air.  This is due to fluid motion and vibration and to a certain extent the loading of fuel into the aircraft.  This entrained air can be up to 14% of fuel volume and will outgas like an opened soda bottle on an increase in altitude.   This changing fluid density effects K factor and therefore a provides a different fuel quantity calculation with a capacitive sender.   We need to calculate the in tank Fuel density with a densimeter and obtain it's K factor and compare this changing fuel density in the tank to a reference standard.  We can now compute actual fuel quantity from the capacitive probe outputs.

FUEL DENSITY EFFECTS

Obstacle 4:  Aircraft ascend and descend and by doing so they introduce moisture into the ullage mixture (air, fuel vapor, humid air) this has multiple effects on fuel measurement.  Quite a bit of moisture is introduced into the fuel itself and will change the fuel quality measurement for a capacitive system.   Water itself is conductive of electricity and this effect on the capacitor circuit  needs to be addressed.   This fuel water mixture produces corrosive components, and by nature the metallic probes cannot be protected.   To account for this you need to add more capacitive probes to cover for corrosion issues that naturally occur in the aircraft fuel tank. 

FUEL AND ULLAGE TEMPERATURE EFFECTS

  FUEL QUALITY EFFECTS 

FUEL WATER LEVEL REJECTION 

FUEL PROBE CORROSION

Obstacle 5: After the TWA 800 Accident the world of fuel quantity changed dramatically.  So while we always had to have a safe system in the fuel tank free from spark energy or lightning effects.  The TWA Accident brought a large spotlight into these issues as the spark from the explosion was found to have come from the fuel quantity system.    Capacitive probes conduct electricity - by nature they are metallic or conductive elements in the fuel volume and they are connected to the aircraft wiring. So you have a direct path into the fuel system through the aircraft wiring.  This introduces a host of issues already covered.  We need to address lightning effects, intrinsic safety (spark energy).  In the case of fuel inerting systems that introduce carbon dioxide into the ullage space you need to calculate this new ullage k factor.

     INTRINSIC SAFETY BARRIER 

LIGHTNING EFFECTS

FUEL INERTING SYSTEM 

WIRING EFFECTS - SFAR 88 & EWIS 

In review - there was a tremendous engineering effort to get "Capacitive"fuel senders to work in aircraft.   

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So Why is CiES Better?

So with a simpler system, we simply didn't have as many obstacles to overcome to provide TSO'd fuel quantity.  Less components, less complexity yields higher reliability.  


CiES utilizes a high reliability position sensor typically found in
automotive systems: drive by wire (brake, throttle & steering), cam
position, and stability control. A non-contact, high reliability, proven
sensor is combined with a simple float, a concept patented by CiES Inc.

The beauty of the CiES system is that our sensor technology allows for better resolution of the fuel volume and is absent the modifications required of an aircraft grade capacitive system.   Fewer obstacles to quality fuel level information. 

So it is immaterial if it is a Beechcraft or Boeing,  simpler is truly better.  Let us show you how we can add value to your aircraft by allowing a CiES FQIS remove weight and complexity from your aircraft fuel quantity system.