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.


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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 

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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 

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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 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. 

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.

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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. 

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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. 

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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. 

Why: 

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  

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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.

Turboprop Fuel Level Senders - Digital

Bull Aircraft - Digital Fuel Level 

This  will be the first of many announcements we are allowed to make before the end of May 2015.

Another customer is added to the list.   Bull Aircraft manufactures a turboprop utility plane the Explorer.  

Bull Aircraft Website

We manufactured our new TSO Senders for this kit built aircraft providing a universal sender for every location. These senders incorporate fuel temperature probes to provide - Lbs. or Kilo's Fuel as this is a Jet A Application utilizing the Walter M601 Turbine.

We are interfacing with a VR Avionics MFD and we expect to see an interesting interface for fuel level.

Both,  Bull Aircraft and VR are Experimental - but the senders for this aircraft are FAA TSO Approved.

We think this aircraft will be sucessful.

CiES Inc Website

CiES Inc Update

If we reflect on the past year we have accomplished quite a bit

• Secured a OEM contract on the most produced General Aviation Aircraft  - Cirrus SR20 & SR22.

• Obtained a TSO for producing this fuel level sender applicable to all aircraft.

• Received retrofit approval to install our TSO sender on all legacy Cirrus Aircraft. 

• Designed an LPG (propane) level sensor with iPhone/iPad interface

• Initiated OEM installation on the Gippsland GA-10 Turboprop, Discovery 201 & Vulcanair P68 Aircraft series.
  
  

• Achieved aircraft industry recognition for our accomplishments

What is now happening behind the scenes is truly impressive 

• Engaged in engineering design with several manufacturers for installation of our fuel level sensors on their aircraft platforms.

• Working three new aircraft platforms 

• Involved in several STC retrofit applications 

• Finalizing the boat level sensor to display at a major customer

• Engineering new aircraft systems and interfaces using our technology

• Planning for exposure in non aviation markets 

So we have been quite busy and very active - and look forward to next opportunity to demonstrate our capabilities

Overnight - The world of aviation fuel level measurement changed

Just like the classic instrument six pack.

Seemingly while you weren't looking  -   The days of simple capacitive and resistive fuel senders disappeared and were relegated to history. 

 You need only to look at the parts manuals for the latest Cirrus SR20, SR22 or Cessna 172, 182 & 206 single engine aircraft.     Take a real close look and  you will see terms like AMR and TDR  (Anisotropic Magneto Resistive & Time Domain Reflectometry).  And instead of a voltage or resistance output to be checked in the maintenance manual - you will see terms like CANBUS and Digital Frequency.  

So what changed ...... well quite a lot ...... the digital age hit fuel level.

• First ---- The FAA requires there to be working fuel gauges in aircraft.  

Fuel gauges that are accurate throughout the range.   Yes the FAA really wants accurate gauges in the aircraft not just at "Empty"

• The FAA in their regulations makes that clear -

• The pilot is required by Part 91.205 to have working fuel gauges
• The definition of working is:   Provide accurate fuel level through the  tank range.

• The aircraft manufacturer is required  by Parts 23.963, 23.1305, 23.1337, 23.1555 to provide working fuel gauges.

• These regulations very clearly indicate that the installed fuel gauges must give accurate fuel level through the whole tank range.
• Note:  Some of these requirements were recently revised.

• Second ----- The rate of fuel starvation events remained unchanged.
•  2 to 3 per week in the US 

For a long time,  excuses have been made for fuel level reporting systems in General Aviation aircraft.   

General aviation fuel gauges were (insert your own adjective) bad, pilots didn't trust them and pilots did not rely on the information they provided.   Plain and Simple 

Uncharacteristically,  the FAA turned a blind eye to the fuel level regulations they provided, tacitly acknowledging in their own documents and publications, that the state of the art was not up to the task.  

Pilots sought and effectively utilized "work arounds" - pilots relied on wristwatches only and aircraft manufacturers and avionic shops installed or incorporated fuel totalizer equipment in the aircraft.  

Iphone App showing fuel level 

Contrary to popular belief totalizers are not required equipment. but they will give pilots confidence in their fuel level.   They have proven to be accurate while in flight and provide a reliable cross check of the wristwatch fuel calculations  at any time.   You will find a fuel totalizer or range graph is on virtually every piece of modern avionic equipment.

Fuel leaking from an aircraft fuel pump

The posting on the web (pictured right) of illustrates succinctly the common complacency of having accurate gauges in the cockpit.   The particular pilot shows his "trusted" iPhone App illustrating a half tank - this app standing in stark contrast to the values depicted on the aircraft fuel gauge.

So why did the FAA really want working fuel gauges in the aircraft.  

Nothing but an actual working fuel gauge .... can tell you exactly what you actually have onboard the aircraft.   

Case in point --- Fuel leaks at a pump are one of the hazards a working gauge will detect.

You would believe that somewhere in the digital age and the era of MFD avionics, the simple fuel gauge would be relegated to the trash heap.   

However 

--- No Pilot Calculation -- 

--- No Totalizer ----

--- No Stop Watch ----

--- No Range Map ----

Only a working aircraft fuel gauge will let you know what you have in your tank and modern technology can give you that information .  

Welcome to the digital age in fuel level reporting 

   

CIES Has New European Installation Centre

CiES Inc is proud to have RGV Aviation 
join our list of Installation Centers.  They are excited to be able to offer their Cirrus customers the new CiES  Fuel Level retrofit for SR22T, SR22TN, SR22 & SR20 Aircraft.

This modification brings legacy Cirrus Aircraft the benefit of the new factory Gen 5 digital fuel level sensor solution.  

RGV - A Cirrus Platinum Service Center -  Based at Gloucestershire Airport (EGBJ), is a family run Aircraft and Avionics maintenance business established in 1973.  As an established EASA Part 145, FAA Repair Station with EASA Subpart G and Irish Aviation Authority Subpart G approval, they have the ability and capability to support you and your aircraft, regardless of your requirements.

CiES  - A design and manufacturing business to incorporated to redefine the measurement of fuel.   CiES patented technology for measuring fuel is intrinsically safe - Non contact,  highly accurate and has proven itself reliable under the harshest conditions.   We brought accurate fuel level to aviation 

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