Cessna Pennycap Press Release - Flying Magazine May 1968

Cessna Pennycap

Copyright Flying Magazine May 1968

Curiosity got the best of us the other day, and somebody wondered if there was a similar example to a disruptive fuel level technology in General Aviation aircraft.   I indicated that there was a different system and it enjoyed a brief and limited success.  This system came out in the late 1960's and was featured on Cessna aircraft.

I went for a magazine search for press releases, curious to see what virtues would be given to a better fuel quantity system.

This system was produced by Consolidated Airborne Systems - which still operates out of a garage location in New York state.

The headline for the article was entitled 

GAS GAUGES THAT TELL THE TRUTH 

"General aviation airplanes - those engineering marvels, this distillations of technical wisdom and aeronautical magic incarnate - use fuel measuring devices of the same arrangement that plumbed fuel quantity in automobiles since the Model A  float tipped rods that electrically drive instrument panel needles to positions approximating the volume of fuel left.  Many such devices are off by as much as 25 percent" Copyright Flying Magazine May 1968

Many mechanics swore at these systems, many are swearing at them still.  The never lived up to the billing as corrosion on these low cost systems quickly robbed them of any accuracy advantage.  If you remember - Penny was to indicate "low cost" and cap was to indicate "Capacitive"  i.e. Pennycap system by its marketing title was a low cost capacitive fuel system.

"For not much more than the cost of an annual, then you'll be able to have a fuel gauging system of honest go/no-go quality.  Can you hold in the soup for 45 minutes at your alternate, or should you declare an emergency and tell them to get you down?  Can you afford to try and get out of that mountain strip with half full tanks and your present baggage load, or are your tanks more like three-quarters full?  It can make a difference." Copyright Flying Magazine May 1968

What is old is now new again - as 48 years later for the price of an annual you can have a CiES fuel gauging system of honest go/no-go quality. 

Cardinal Flyers Organization Digest - Sun & Fun

FROM THE Cardinal Flyers Organization DIGEST 

JP Instruments, the engine monitor folks, shared that they continue to work with CIES, a friend of CFO's, who have introduced a superior design fuel level transmitter.

JPI EDM 930

The JPI930 certified engine instrument replacement already works with the CIES transmitter in native mode, frequency domain.

JPI EDM 900

The JPI900 certified engine instrument replacement works with the CIES transmitter in voltage or current mode.

CiES Inc 177 Fuel Senders 

Several Cardinal owners have already ordered the CIES transmitters to improve repeatability and accuracy of their fuel level measurements, while reducing installation cost and fuss, and hopefully achieving longer term reliability.

www.jpinstruments.com

www.ciescorp.net

The Three Fundamental Truths About Aircraft Fuel Level

We have a unique perspective to aircraft fuel level,  in that CiES works daily on these systems.  We see the good, the bad and the downright ugly.

What we have observed and are sharing here is what CiES has determined to be the

Three Fundamental Truths about Aircraft Fuel Level Systems. 

Here they are:

If the technology of fuel level measurement can find the surface of the fuel reliably. 

• Floats that actually float or are allowed to float.
• A set capacitance based on fuel level in a tube (ignoring temperature & other fuel dielectric effects).
• Ultrasonics tend to get messed up with foaming fuel. 

If the basic sensor system can output a lot of data related to fuel level. 

• A capacitance fuel level system can output a theoretically infinite number of data points - but realistically in an actual fuel level device -  potentially 10,000 to 30,000 data points 
• Our Magnetic Field Technology has 10,000 to 12,000 data points.
• A legacy potentiometer system that provides maybe 50 or 60 data points (wiper and trace size controlling the data point size) 

If your fuel level display system can capture the complexities of a fuel tank curve  

• a non linearly marked fuel gauge or an Multi Function Display with a calibration feature

Then if these three criteria are met - you will have an excellent aircraft fuel level system - meet a few of them and your fuel level system will be functional. 

As we know the world isn’t perfect -  

To make a old aircraft fuel level system work well -  You need to make a unique potentiometer, carefully assemble it to reduce internal friction, maintain wiper contact and hope it all holds together and doesn’t corrode.  

Now combine the above with a non linear and an easy to calibrate gauge.  This is fussy work at best.

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Here is  our real world challenge  - 

• Say for example you have a simple fuel gauge marked with the same distance from Empty to 1/2 tank, & from 1/2 tank to full 
• We are all very familiar how long it takes to go from Full to 1/2 Tank and that it takes a fraction of the time to go from 1/2 Tank to Empty.
• The above is a fundamental universal truth. 
• Therefore because CiES can  - we load a tank table with a characteristic curve onto internal memory on the sender.
• Log, Sine, 3rd order, 4th order, 5th order, Non Linear - You name it - We can do it - challenge us.
• Of course we need the tank function and a simple gauge to get it right.
• Unlike a potentiometer - we don’t have to cram all that onto a circuit card by physically making the small steps with variably positioned traces, or onto a carefully delineated gauge.
• We have 10,000 reliable data points with our sensor technology - we just do it in software - easy peasy. 

Just don’t tell me that fuel gauges only have to be accurate at empty - we get all apoleptic.

Cessna - New Technology Non-Contact Fuel Level Sender

CiES Inc, Cessna Fuel Level Sender 

We are in the process of serial manufacture of a Cessna Fuel Level Sensor.  

Cessna Fuel Level Sender 

This fuel level sensor utilizes our patented magnetic field technology and carries FAA TSO Approval.  

Note:  TSO Approval is FAA component approval and not FAA installation approval.

We set out in 2010 to change the dialogue about fuel level indication in aircraft & we accomplished this by building an aerospace specific fuel sender design.  

Fuel Level Sender Exploded View

This new fuel sender design, while resembling older technology potentiometer fuel level senders, centers around a robust patented non contact sensor technology.  

The only common part between our fuel level sender and old technology is the float.  You can see the CiES attention to detail we are internationally known for.

Our goal was to design a fuel level system that had the potential of replacing many legacy aircraft fuel senders in the field.  Our initial fuel sender production was utilized almost exclusively by OEM aircraft manufacturers and to meet OEM requirements they utilized a robust proprietary digital output.  Unfortunately this output was only suitable for Garmin G1000, JPI 930 & Aerospace Logic displays and instrumentation.   We have produced over 7,500 non contact fuel level senders in this configuration and the results have been exceptional.

Our recently issued TSO allows us to reach and support a broader range of cockpit fuel indication interfaces and as a correlation allow CiES to spread it's wings so to speak.   This new sender design allows the CiES fuel level sender to output a variable voltage or resistive load giving us a nearly universal capability to support legacy aircraft.

As such, we are actively working on CiES fuel level solutions for many popular aircraft. 

Contact us and see if we have a solution for your aircraft.

Learn more on the CIES Inc Website

Cessna - Friggin Lasers in Their Fuel Tank

Hidden Costs Behind the High Cost of Aviation 

I had started to re-energize our 2015 marketing effort  and wrote a few blog posts about delivering magnetic field fuel senders to,  new to us,  European Aircraft and Helicopter customers.  We seem to be popular over there,  we may owe many thanks to Flieger editor Thomas Borchert  

To check on our progress on our google search listing placement,  I ran across a G1000 Cessna Fuel Sender for Sale on Ebay  and thought I'd share it.

This is a Meggitt TDR (Time Domain Reflectometry) Fuel Level Sensor for a Cessna Single Engine.

• Used Ebay Price is $1,800 each
• New Price from large Cessna Parts Jobber is $3,100
• Cessna List Price is $3,864.  

The Meggitt Fuel Level Sensors do look well made and come with a nice calibration sheet for your Cessna 172, 182 or 206.

Replacement Cost for 2 of these sensors on a Cessna would be $7K to $8K a Kit -  Installed cost would be well over $10,000 - This for a retrofit fuel level system on a Cessna 172 for heavens sake.  It is painfully obvious why there isn't a retrofit STC available.

Maybe some in aviation are correct,  airplanes are getting to be very expensive  - part prices contributing greatly.  But with a bit of creativity, it doesn't have to be.   

The caveat is,  that our Fuel Level Sensors met all the FAA TSO requirements that the TDR fuel sensor has met - and we do it for far less money.  I was told early on,  Engineering is not building the best without regard to cost, it is providing best performance at a price that is attractive to your consumer and the FAA.   

While I have heard that our FAA TSO fuel level sensors are expensive compared to legacy commercial grade resistance fuel senders, i.e. the kind of sensor they used to put in aircraft of the past.   I agree to a point on the expensive part arguement, but I truly feel CiES hit the target.  We provide improved aviation technology and performance at a competitive price. 

This Meggitt TDR sensor is not a well known change to the venerable Cessna Single Engine Lineup,  you would be hard pressed to know this was in your wing unless you queried the Cessna Illustrated Parts Catalogue.   There is no mention of this system any Cessna Marketing literature.   You'd think that a $8,000 fuel level system would be worthy of editorial or marketing content  - I guess it isn't.

Almost overnight the world of aviation fuel level changed and somehow nobody bothered to notice.

The TDR system works by shining laser light down a glass rod and measuring returns, so next time you come in contact with a G1000 Cessna owner - Let them know they have "friggin" lasers in their fuel tanks. I am going to bet they'll be surprised.

Magnetic Field Fuel Level Senders - Resistance Output

 Another Day And Another New Fuel Level Sender Configuration @ CiES 

While we discussed the Universal Output Sender in a previous blog post, it's much better to talk about an actual fuel level sender we are sending off to it's intended OEM manufacturer.   

This new configuration will output an equivalent resistance to be read by a gauge or the aircraft MFD.   While it appears on the surface to be easy it is actually the result of a 3 year effort to provide an output suitable for the aviation environment.   

Our senders are natively frequency output based, and this output has proven to work very well in our OEM and retrofit applications for Cirrus Aircraft,  but what we needed to do was convert that frequency to either a voltage or resistance output.

So we manipulate this native output to provide a variable voltage or a variable resistance.  

This unit for a new customer contains everything we wanted to provide;

• Frequency Output Fuel Level
• Slave Sender Input
• Resistance Output Fuel Level
• Fuel Temperature 

It is the culmination of making a Fuel Sensor that is compatible with most platforms out on aircraft & helicopter platforms in the field.

Cessna Cardinal 177 Fuel Sender Design Process

Can we offer a Retrofit CiES Fuel Sender for your aircraft. 

What are the steps we need to take: 

New Cessna 177 Cardinal Fuel Level Sensors 

• Obtain a a set of old fuel level sensors from the aircraft we are considering.  If the part numbers for the senders match the aircraft they are on, we are good to go.

• Ideally this aircraft should have a strong user base with an owner base that demonstrates their willingness to embrace new technology with their pocketbook.

• Discuss the compatibility with commonly installed MFD components or instruments.  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.

Old Cessna 177 Stewart Warner and Leigh Fuel Sensors 

• 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 prototype sensor with our best guess for geometry.

Cessna 177 Cardinal Fuel Tank - Internal Shot

• 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.

Fuel Tank with Prototype Sensor Installed 

• 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 -

Varying fuel tank angles caused by imbalanced fuel filling - filling one side before the other

or 

The angle of the ramp typically created to drain water from the ramp surface.

Both of the above have an effect on apparent aircraft fuel level from simple visual observation.  

• A confirmation of entered fuel level and actual fuel level when the aircraft is in stable cruise flight may allow the pilot to correct for an erroneous starting fuel level value. 

• The final result is a happy customer with a new fuel sender design that has hundreds of data points to describe the fuel tank contents on their new MFD display or instrument.

Note:  While this seems to be an involved procedure - accurate fuel display on an aircraft requires this level of detail otherwise you might not get the information you need.

Cessna Cardinal 177 & 177 RG Fuel Level Sensor

Well we produced another configuration of our fuel level sender for a very popular Cessna Aircraft model with a rabid and enthusiastic following.

---- Yes the Cessna Cardinal 177 ----

We had sought out common aviation fuel level sensors to copy into our format and we had a few mixed results, for example owners of Cessna 177's would send in the sensors per our request,  but the part numbers of the units supplied only matched up to another model Cessna Aircraft and did not match any of the Cessna Fuel Level drawings we have on hand.  

Finally, last year we got what we were looking for - Senders from an aircraft that matched the P/N for the aircraft. 

Note:  When you get involved in this small segment of aviation - It becomes very clear why fuel level in aviation has a very low reputation.

A Cardinal Aircraft owner tells a better story: 

Anyway, I saw the mention of CiES on one of the Cardinal Flyers Digests and gave them a call.  I spoke with Scott Philiben, who said that they could build them for me, and it would interface correctly with the JPI.  JPI confirmed this.  This was last FEB 2014 when I initially purchased the JPI, based on that answer.  

I had to wait till July 1 to start install, both due to the cold weather here, and because that was my annual date  (I also wanted to install an Oilamatic Pre-oiler and an Alpha Systems AOA Gauge).  

What Scott didn't tell me initially, was that I was to be the guinea pig for them getting a TSO sender for Cardinals as this minor variation needed to be sent to the FAA and approved - they had predicted an October delivery.

Scott & company finally came thru with fully TSO'd senders in late Nov, but I then encountered the passing of my Mom, which has led to further down time - anyway, FINALLY got the senders installed last Saturday.

CiES Above - Competitor Below

I was quite impressed on the substantial difference internally between CiES senders and the Electronics International ones.  The electronics in CiES look great, and based on the digital freq meter I have, they work VERY smoothly. I am also impressed with the machining on the fuel senders.

For JPI's part, their wire harness to the wing has three wires - +5V, Ground, and Signal. The JPI diagram says NOT to connect the +5V for CiES, but what they didnt say, and I didnt know until early Nov (when I mentioned that to Scott at CiES) is that the CiES units need +12V!! Turned out not to be an issue - the JPI harness has a "Y" connection in the harness shortly after the harness leaves the JPI box enroute to the wings - I unpinned the +5 wire that comes from the JPI and capped it off, and instead ran a +12 supply from one of the Circuit Breakers (dont remember which at the moment) into the same pin spot. (There is NO interface box as there is with some other senders. Not sure if my JPI is any different internally - JPI could answer though.) Works great (again, on my digital freq meter out at the sender)

One thing I particularly like about the CiES is that the float arm wire is 3x as thick as the one from Cessna, BUT the CiES float arm easily disconnects from the sender, making installation MUCH MUCH MUCH easier. I placed a long tie wrap on the fuel sender arm (in case I dropped the float/arm combination into the tank while working the sender into position) and then after the sender was connected and small cotter pin inserted, the tie wrap was removed. The senders come with a new rubber gasket, and there is no chance of leakage in the middle (like Cessna supplied Rochester, Stewart Warner, or Leigh senders) as there is no pass-thru screw terminal.  CiES uses a 3-pin connector with a twist lock shield. VERY easy to plug in.

At first, Scott and his engineers were concerned about MIN/MAX settings, but they had an epiphany one night and realized that all measurements are relative. They were worried about setting hard "stops" these are the little metal tabs on Cessna original equipment fuel senders that limit the float arm travel.   Turns out the CIES senders have the capability to move thru-out an almost 180 degree range from straight down to straight up.  The original equipment Cessna fuel sender contained a 60 degree potentiometer which limited the angle range allowed by these senders.   The calibration in the JPI is what establishes the fuel level limits and the physical limits of the fuel tank are the physical limits of the sender.

Scott Philiben's phone number is 541-408-1095 - they are in Oregon, so there is a 3hr time difference for me. His email is scott.philiben@ciescorp.com I still have the prototype sender/float combination that we used for testing and verification that this new simpler configuration would not hit any internal ribs/structure. Can't see internally, but externally it looks exactly like the ones with the TSO labels on them!

Update - Installed and calibrated - first impressions are good 

A Universal Aircraft Fuel Sender

A UNIVERSAL FUEL SENDER

When we started manufacturing fuel level senders,  we had a specific customer in mind.   

In order to maximize our customers benefit for this technology, we made this sender nearly exclusive for that customers application. 

We received quite few inquiries for this fuel sender and most of them related to will it interface to our existing system.  

Sadly because we had tailored the sender to a particular aircraft and avionics interface,  we had to turn good business away.  

So step forward 3 years nearly to the day,  we had an opportunity to reinvent the fuel sender product and add new features:

First:   We have utilized a unique circuitry design to create a universal output:
                         - We can supply:  Resistance
                                                      Voltage
                                                      Frequency 

Second:  We can supply a  Fuel Temperature Output.  This feature is helpful for Jet A applications  where Pounds Fuel is the unit of measure.

Third:  We have supplied a pigtail to allow installation in tight spaces and flexibility in the Fuel Sender connection. 

We are trying to remove any barrier for you to have a more reliable technology for fuel level in your aircraft.

Contact Us for more information.

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

Customer Feedback - Cirrus Retrofit

Folks I just picked up the plane this evening from Advanced Aviation in Lancaster PA.

Joel Glover and his team did an outstanding job installing the new CIES digital fuel sensors despite a steep learning curve on this first ever install.

The next one (an SR 20 was already in the shop) should go a lot faster as the first is always the hardest.

I had a chance to run the system through its paces on the short hop from KNLS to KMMU this evening.  I must say my first impression is WOW !  A huge improvement.

I love having the fuel flow quantity on the MFD now, but the icing on the cake is the redundancy with the new digital fuel guage that replaces the former analog version.

Really cool looking, but more important is the functionality.  I really like how you can flip between fuel quantity and the fuel burn graph, really helpful for fuel balance. 

The CIES team even made sure it dims with the instrument dimmer.

I will get some more time this weekend (during the daylight) to run it through its paces, but 

I would HIGHLY recommend this a must have upgrade to your Cirrus.

Get in line now and place your orders, I am convinced you will not regret it.

If you want to eliminate all your fuel level issues, this is the only way to go.

Like you I highly recommend Advanced Aviation in Lancaster PA as the place to get it done.  Joel and his team are the defacto experts now for this upgrade.

TSO C55a Approved Fuel Float Level Sensor

CIES Inc has obtained FAA TSO Approval - C55a - at the most rigorous standard for it's line of float based digital fuel level senders.

Its official we now are producing a line of TSO'd Fuel Level senders applicable to most aircraft below 12,500 lb gross weight. 

This effort provides a real alternative to the old Stewart Warner  senders long out of production for current General Aviation Aircraft fleet.

We are working with every major manufacturer to incorporate our senders as original equipment.

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 

Intrinsic Safety for Aircraft Fuel Tanks

INTRODUCTION    
A flammable mixture of fuel vapor and air can exist at times in a partially filled aircraft fuel tank containing jet fuel or much less so Avgas.  Research has been done to develop methods to eliminate or reduce the risk of having an explosive condition in the fuel tank. There are a few different approaches to preventing fuel tank explosions. Explosions need three conditions to occur simultaneously: a flammable fuel source, sufficient oxygen to react with fuel molecules, and an ignition source to start the chemical chain reactions. Eliminating any one of these conditions will prevent a fuel tank explosion. 

REDUCING OXYGEN CONCENTRATION

Recently, attention has been focused on developing a low-cost, low weight, high-efficiency fuel tank inerting system for use in large transport airplanes. This system uses high temperature bleed air from the engines to create nitrogen-enriched air (NEA) with as high as 98% nitrogen concentration. The NEA is plumbed into the ullage space above the liquid fuel in the fuel tank, forcing air out the vents and creating an atmosphere with a maximum oxygen concentration of 12%. This value has been shown to be the lowest oxygen concentration that will support ignition of  fuel vapors. This approach eliminates one of the key ingredients required to have a fuel tank explosion (sufficient oxygen). 

So now we have added a component to the aircraft to address what can't be addressed with a capacitive system in the fuel tank.

REDUCING IGNITION PROBABILITY
Ignition of fuel vapors can occur as a result of several different mechanisms. Voltage sparks, thermal sparks, and hot surfaces are the most probable ignition sources present in or around a fuel tank. Any of these ignition sources could occur due to lightning strikes, electrical faults in fuel tank electronics, or short circuits caused by cleaning debris, such as steel wool or other small conductive filaments that may have been inadvertently left within a fuel tank. Combined with fuel tank inerting, reduction or elimination of the likelihood of ignition sources could provide an additional safety factor to preclude virtually any fuel tank mishaps during the life of an aircraft.

Electrical spark has been the standard method of determining ignition energy required to ignite a flammable mixture. The generally accepted minimum ignition energy for a hydrocarbon/air mixture is around 200 micro Joules (μJ) for a specific mixture of fuel and air, usually at a stoichiometric mixture or slightly richer. The 200-μJ energy in most experiments is the energy stored in a capacitor and discharged across an electrode gap as a voltage spark. It should be noted that the stored capacitor energy is not the exact amount of energy deposited into the spark, as there are always losses between the capacitor and the electrodes. Nevertheless, the capacitor energy is a very good approximation of the minimum ignition energy of a mixture and the relative ignition strength of a voltage spark.

Flammable mixtures can also be ignited by means of thermal or friction sparks. Thermal sparks are different from voltage sparks; they are very small burning particles of metal that radiate bright colors due to high temperature burning. Thermal sparks are produced either by two hard surfaces sliding against each other creating a shower of sparks or a wire or filament making or

Spontaneous ignition of flammable vapors can also occur due to heat transfer from a hot surface to fuel molecules. A standard test method has been developed to measure the autoignition temperature of a liquid fuel by dropping a small amount of fuel onto a flat, heated surface and noting the temperature at which a flame is observed. It has been accepted that the autoignition temperature of jet fuel is around 450 ̊F and Avgas is around 536 ̊F , although these are not exact figures. Many factors can affect the ignition of the fuel vapors and the propagation of a flame front from the hot spot. The design of the test apparatus will determine the type of combustion that will occur. Cool flames can develop and propagate through a flammable mixture without creating an explosion as long as the rate of heat generated is not much greater than the rate of heat lost; explosions can only occur if significantly more heat is generated than lost.

Currently, the Federal Aviation Administration (FAA), guidance for electrical systems that introduce electrical energy into fuel tanks, such as fuel quantity indication systems (FQIS), provided in draft Advisory Circular (AC) 25.981-1C, states a maximum steady-state current of 10 milliamps (mA) root mean square (rms) is considered an intrinsically safe design limit for FQIS. It also states that current levels above 10 mA rms, particularly for failures and transient conditions, could also be considered acceptable, provided that proper substantiation by test and/or analysis justifies them as intrinsically safe. As an example, the AC states that for transient conditions, it is acceptable to limit the transient current to 150 mA rms, and failures that result in steady-state currents above 10 mA rms should be improbable and not result in steady- state currents greater than 30 mA rms. These values were determined after a considerable factor of safety was applied to the lowest values found from previous tests using Jet A vapors and steel wool filaments as the ignition source. The experimentation presented in this work was performed using a calibrated gas mixture with a predetermined minimum ignition energy to solidify the confidence in the electrical current guidance in draft AC 25.981-1C. 

CIES Inc FQIS SENDERS - 
Our senders do not have any electrical components in the tank, and no generated heat energy to ignite fuel in the tank.   The system measures the position of a magnetic pair on a float arm located inside the tank from a location outside the fuel tank proper.   This method of sensing is Anisotropic Magneto Resistive technology and is exclusive to CiES Inc.   

The CIES Senders eliminate the in tank ignition sources that could occur due to lightning strikes or  electrical faults in fuel tank electronics.   As the sensor does not rely on the fuel interface for measurement,   corrosion removal is not an issue.   Cleaning materials like steel wool that are used to clean capacitive sensors are not required with the CiES sender design.