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Tuesday, November 3, 2015

Early Bonanza Fuel Quantity Senders

Early Beech Bonanza Fuel Senders

What are the steps we need to take to build fuel senders for your aircraft: 

  • Obtain a a set of old fuel level sensors from the aircraft we are considering (see the lower portion of the picture on the right).  If the IPC part numbers for the supplied senders match the aircraft they are on, we are good to go.
  • Ideally this aircraft should have a strong user base with an owner that demonstrates a willingness to embrace new technology with their pocketbook.
  • Discuss the compatibility with commonly installed MFD components or instruments.  We prefer instruments that accept digital input like Aerospace Logic, Garmin & JPI.
  • CiES  Fuel Level Senders now has the capability of driving even old analog gauges in the aircraft (Universal Fuel Level)..
  • Our market is the pilot / customer that is more concerned with fuel level issues and wants the required fuel level instrument in the panel to have the  capability of multiple point calibration.
  • Evaluate the existing sensor design -  For example the bends in these sensor arms are either to assist in installation and removal of the fuel sensor or to clear aircraft structure in the fuel tank.
  • As our sensor design allows for an easily detachable arm - these bends might not be necessary and simplify the design greatly.
  • We then proceed to manufacture a conforming sensor with our best guess for geometry.
  • Check the sensor in the aircraft fuel tank.  As you can see in the illustration - in this case the simple arm design works better in the tank and sweeps a better fuel volume being closes to the Spar and maximum chord point.
  • At this point we qualify the design with drawings and procedures for the completed unit so that we can send these files to the FAA to have this configuration added to our TSO.
  • Once we have approved drawings we can can produce the required sender with a TSO Tag attached.
  • The fuel tank is then drained, the aircraft leveled and braced only then is the zero fuel amount added.  There should be movement of the sender to be able to record an accurate zero fuel level, this is an absolute requirement.
  • Fuel is then added to the tank incrementally and accurately to obtain data points for calibration.  We direct the installer to take special caution to insure tabs fuel value is accurately recorded by the fuel display.
  • Equally the installer needs to insure full fuel level per the POH is also accurately displayed.   
Note:  All aircraft fuel tanks are built with expansion volume - Full fuel per the POH may or may not be to the neck on the filler plate.  This is very important as the aircraft will probably be fueled in the future on a ramp - 

Wednesday, October 21, 2015

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.


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.

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.

Monday, October 5, 2015

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. 

Friday, October 2, 2015

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.

Thursday, October 1, 2015

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 


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. 


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.


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. 





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.





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


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.

Friday, September 18, 2015

Bad Aircraft Fuel Level Indication Can Lead to Aircraft Fuel Starvation.

Really Where's your Proof 

Yes I know you have read every publication put out by AOPA and the FAA and they clearly say fuel level indication is clearly a pilot error issue.  In NTSB reports they have a rubber stamp that reads like the following :

"The pilots improper pre-flight and inflight planning, which resulted in fuel exhaustion."
What most in the general aviation community opinion on this issue is referred to as Fundamental Attribution Error.  (FAE) This is where we naturally blame people, even when circumstances or conditions are the primary issue.  

Last week I wrote a blog with the intentionally provocative title: "Let's Legislate Accurate AIrcraft Fuel Level"

For this I received the expected typical responses below: 
"How about we simply look at the number of people that have fuel related accidents and see if they did a proper preflight ...which...since you keep going by FAR's is required. If they didn't do a preflight correctly...they are poor pilots...and if they are poor pilots...gauges won't make a difference. You can't save people from being stupid"
"So, how much of this is lack of awareness, poor training or just laziness I do not know. But this is one of the most preventable accidents out there that keeps happening on a regular basis. I am not convinced an AOPA video will change that.  That is the real crime. They are still happening twice a week and none of them have to."

You would actually expect this pilot response to the provocative inquiry.   In looking at this as a pilot cultural issue or a FAE  the concept of  "Just World Phenomenon" features prominently.  This is the belief that people get what they deserve and deserve what they get.   

Unfortunately, the just-world hypothesis also results in a tendency for people to blame and disparage victims of an accident or a tragedy.  It is actually a protective strategy of the mind, providing mental separation from those kind of pilots that run out of fuel.   It won't happen to me, I am not like one of those pilots.

Sorry - These are random events and they happen to good pilots - I have a files and files from Transportation Boards across the world - you are not immune.  You have a doppleganger who was just as careful as you are and ran out of fuel in their aircraft.   I am sorry to burst the protective bubble.

What appears to happen in General Aviation is that, blame for fuel starvation, falls squarely on the those pilot shoulders .  This appears to be cultural phenomenon among pilots of all types.  The primary message we hear is that education will cure the miscreants, those bad pilots that will always get into trouble.

Very rarely do we delve into the situational factors of the fuel starvation issue at hand.  Our cultural bias doesn't allow that possibility.


Fuel indication in aviation is loathsome at best - it is not a deep dark secret that most aircraft fuel indication systems are marginal from the start. 

 When you compound a marginal system with poor or no maintenance,  you can make a general statement that a functionally inoperative fuel gauge is common place in aviation.  

This is illustrated by responses from a General Aviation News inquiry as to what pilots felt about general aviation fuel level indication.
"Maybe they’re also more in the habit of keeping an eye on the clock in flight, even sneaking the occasional glance at those notoriously inaccurate fuel gauges." 
"Airplanes are legendary for having inaccurate fuel quantity gauges" 
"These devices are notoriously inaccurate, showing empty when there are gallons left in the tank and showing full for the first 1/2 hour."
"Aircraft fuel gauges can be notoriously inaccurate." 
"Without a means of measuring fuel flow, you must rely on the aircraft fuel gauges or total time of flight. Aircraft fuel gauges are notoriously inaccurate (they are only required by the FAA to read accurately when displaying empty)." 
"Aircraft fuel gauges have a well-deserved reputation for being unreliable and the FARs only require that fuel gauges read correctly when they are empty!" 
"Second, as others have said aircraft fuel gauges have historically been
poorly designed and grossly inaccurate.  Many will indicate something significantly different in a climb vs a descent and there are some airplanes with fuel gauges that are designed to read full until a substantial amount of fuel has been consumed." 
"Don’t bet your life on your fuel gauges, visually check the fuel level by “dipping” all tanks. Some aircraft models have notoriously unreliable fuel gauges." 
"All light aircraft gauges are notoriously, infamously and reliably, unreliable." 
"Sounds great in theory, but I have not yet seen an accurate Cessna fuel gauge, Ever. A fairly expensive AD would be the only thing that would ever change that."
I don't think a statement that  "Aviation fuel level indication could be improved" would fall very far from the mark. 


Better fuel indication will lead to better decisions and appropriate warnings in aviation.  

While it seems obvious to a layperson

Strangely, Thats not the popular opinion in GA.  But here is the proof. 

EASA (European FAA) - In a Transport Aircraft study for revisions to required powerplant instruments.  EASA showed that better fuel indication would have improved the result of the 65 incidents and accidents in Transport AIrcraft - well over 70% of these accidents/incidents could have been avoided.  Transport aircraft are not GA, but it is the same mode.

CASA (Australian Civil Aviation Authority) Requires that aircraft fuel Indication in Australian aircraft meet a performance standard, every 4 years.   The reasons cited are improving the fuel starvation incident and accident rate. 

TSBC (Transportation Safety Board of Canada) Makes findings of faulty fuel indication a factor in fuel starvation events.  They point to the wide use of fuel sticks as an indication that fuel level reliability could be improved in aviation
 The fuel quantity indicators on this type of aircraft were not reliable. As a result, the pilot could not be sure of the quantity of available fuel in the left tank during flight.

Tests on the components of the fuel level indication system established that the only time the fuel level in the wing tank was shown correctly was when the tank was empty 

The Bell 214B and Bell 205 flight manuals be modified to provide information regarding the inaccuracy of fuel quantity indications, thereby allowing pilots to make informed decisions in the event of a loss of fuel boost pump pressure. 

Cognitive Bias 

While these two points are associated with the same system and appear plain as day 

  1. General Aviation Aircraft have inaccurate fuel level indication.
  2. General Aviation Aircraft are prone to fuel starvation and fuel exhaustion.

A general aviation pilot won't recognize those statements as connected. 


Anchoring Bias -  The tendency to rely too heavily, or "anchor", on one trait or piece of information when making decisions (usually the first piece of information that we acquire on that subject.

Pilot's are told to never trust the fuel gauge on the first training flight. 

Availability Cascade A self-reinforcing process in which a collective belief gains more and more plausibility through its increasing repetition in public discourse (or "repeat something long enough and it will become true.

Bandwagon Effect The tendency to do (or believe) things because many other people do (or believe) the same.

AOPA, FAA continually tell us that we need to use proper pre-flight procedure including sticks.
Confirmation Bias The tendency to search for, interpret, focus on and remember information in a way that confirms one's preconceptions
Aircraft fuel gauges only have to be accurate at zero 
You're only interested in selling senders  
I have a passion for European Sports cars of the 50's and 60's  and I was talking with a group of MG-TC owners.  The subject of fuel indication came up and the MG owner brought out his calibrated stick.   MG T Series cars don't have a fuel gauge, they have a warning light, and Old British cars being what they are the warning light isn't a trusted component or indication of anything of merit.    

I mentioned that small aircraft use a stick as well to determine fuel quantity.  There were lots of raised eyebrows and a few quizzical looks.    The very first statement I heard was.

  "I bet they run out of gas"
  followed by 

"They can't just pull over and check with the stick can they"

I told them the various reasons why,  and they asked if something was being done to improve that.  

I told them sadly no.  A pilot will go out today after purchasing a new aircraft and obtain a stick to measure their fuel.  

It's  startling commentary, that in aviation, we use fuel measurement methods and techniques to prevent running out of fuel that were common on minimal equipment British sports cars of the 40's & 50's.  

I hope it makes us think.