Beech Baron Digital Fuel Level Sender Retrofit - Part 3

Beech Baron 58 Fuel Level Senders

We have now digitized the Baron 58 Senders.  For the Baron 58 we have gone ahead with part production for top mount senders and only needed to establish the arm lengths to complete this design.   As we produce the arms in house - this gave us the shortest time to achieving a TSO Baron Fuel Sender for our customer.

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

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

One of the interesting items that came up in investigation is that every legacy Outboardd bottom mount Beechcraft Baron 58 Fuel Sender has a seemingly factory grind mark on the housing and screw  - Clearance ?

Stay tuned for further updates and pictures.

Cessna 210 Digital Fuel Level

CiES Added Another Aircraft Today 

So three new aircraft configurations this week in as many days.    This one was admittedly easy as it is identical to the Cessna 177 Design.   

I believe our greatest accomplishment this year is developing a methodology to add TSO'd configurations to our list.   

Our magnetic field design makes changes to fuel senders as easy as changing float arm length and an internal map profile 

Our technology for fuel level sending is eclipsed by no other method.  Magnetic Field is superior to both traditional aircraft Capacitive and Resistive fuel senders.  

Contact us to find out why we can make such a bold statement.

Tilting @ Propellers

Illus. Chris Demerest http://chrisdemarest.net 

Today I took a call,  the pilot on the line was enthused, he really wanted to get our new technology fuel senders on his aircraft.  

Further he engaged us in a dialogue wanting to let us know how significant this product was to aviation, and to his passion, you know the type,  a typical Mooney pilot.

He told me about the AOPA statistics on fuel mismanagement and starvation, and that it wasn't good press for general aviation or general aviation safety  to have a fuel starved aircraft parked along  a busy highway.

He was adamant to tell us about the significance of redundant and confirming cockpit information.  Being able to cross-check the two independent fuel quantity indications in his cockpit, he felt, would virtually eliminate fuel starvation in general aviation aircraft.

He talked about the level of quality he saw in fuel senders used in aviation, and that he just hoped he wouldn't have to overhaul his original set for the umpteenth time, and then have them fail hours later in flight, as they had on the past two occasions.

He related to me that as a multi type rated and experienced pilot he had never flown behind a good aviation fuel gauge in his entire life.

I didn't say a word  I sat back and listened to the sentiment that put us on the path to start a company around this product and idea.

The idea that we will build a good fuel level sensor, a quality fuel level sensor,  around robust patented technology using aerospace materials and standards.   We will prove our commitment by qualifying this fuel sensor to the most ridgid FAA standards for manufacturing and design.

My dream is that pilots will get this and install or demand this technology on their aircraft.  If that happens, we will make a lasting contribution to the aviation industry.

So many times in this aviation business,  you feel like you are setting your train along the wrong track,  why are you building a company in aviation,  when successful people all around you question the market size, vitality and rational.   You question your own sanity on a daily basis.

I guess we do this,  because our passion makes us tilt toward that propeller.  some days it's nice to know we aren't the only ones.

What Accuracy in Fuel Level Means for General Aviation

Why would I want accurate fuel gauges in my aircraft. 

Predicting and shaping the future are the providence of engineers.  

If accurate and reliable fuel level sensing for aircraft became a common reality 

What are the effects on the aircraft/pilot interface.

Warnings and Annunciation 

With cross checkable and reliable information between the Fuel Totalizer and Fuel Quantity 

• Low Fuel  
• It is already exists - 
• What if it was reliable and predictable

• Fuel Imbalance - 
• Let you know when you exceeded tank imbalance limits
• Warns you of a rapidly depleting tank - safety  

• Fuel Leakage or Venting  
• Matched information fuel totalizer and tank volume
• If rate of flow d not match - a leakage or venting warning 
• With a residual power or memory input
• Internal leaks annunciated 
• Fuel Theft 

• Errors - 
• As a reliable cross check between fuel flow and fuel tank volume 
• Provides a reliable diagnostic to errors or faulty components in each system
• Failure to follow a predictable path can be flagged as an sensor or tank system requiring maintenance. 

• Secondary Fuel Totalizer - Cross check to the fuel we can derive rate to give a simple totalizer function.

Automation 

With cross checkable and reliable information - Fuel Totalizer and Fuel Quantity we can use this information to relieve pilot workload 

Fuel  Management Computer - 

• Tank Switching -
• The aircraft system would handle switching between tanks for single engine aircraft.
• This could be overridden manually in the cockpit.

• Fuel Management. 

Allow a pilot to mange total fuel volume on the aircraft with an interconnected pump system 

• Minimizes human refueling errors 
• Cross-check quantity of fuel added and correct
• Manage the fuel added or remaining to balance tank volumes.
• Use fuselage wing tanks for weight and balance corrections or trim

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.  

Digital Output - Fuel Level Sensors

Digital Fuel Level 

When you enter the term above in Google you get a variety of responses most of them showing a display indicating fuel as a digit value on a screen.

What this is a numerical  manipulation of the the analog signal that most fuel level senders provide as an output:

Simple electronic analog values are the tradition for fuel level measurment.

• Resistance
• Capacitance
• In the case of Reed Switches  - Current or No Current.

But what we have is just another way of showing what analog sensors are providing digital is display only.

Digital output at the Sender is Unique - there are several aftermarket Capacitive Sensors in the Marine industry or Telematics that use a conditioned digital output.  There are conversion processes for these senders - temperature compensation signal conditioning maybe a de- bounce (smoothing) function.

Capacitive senders take an analog signal give it a binary component and communicate the signal.

What if the native language of the sensor were digital in that each fuel level was represented by a binary stream - natively   No conversion - no compensation - and if non contact

 No issues with Fuel quality or Fuel type  - NONE .

 In fact no compatibility issues with the measured liquid in question whatsoever

When Fuel is Important or Critical to Operation
Fuel level is important but what if knowing how much remained meant the difference between an inconvenience or something more significant.

The manner in which we handle the digital output signal is proven in aviation applications -

Signal integrity is paramount - in an environment where static charge and exposure to radiated fields would bring most fuel level systems to their knees.  If you couple the requirements for vibration shock and the extremes in temperature - it is surprising that any fuel level sender works at all in aviation.

So why Digital 

• The level output is provided continually -
• The Fuel Level is reported over and over again to the gauge or display
• The signal does not suffer from signal loss or interference
• Either the complete signal is transmitted or nothing at all 
• Not effected by voltage variation
• Many more data points to map the fuel tank
• 3,800 distinct points for 80 degrees of travel possible 
• No Temperature Effects 
• No compensation
• The device will output fluid temperature if required
• Failure is hard and the results predictable
• False signaling of tank volume due to wear is virtually eliminated.

Imagine a level sender that thrives in the critical  aviation environment and think what it could do for your application.