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Sunday, August 13, 2017

The Why of CiES

For pilots and aircraft owners of general aviation aircraft, it’s been a historical challenge to measure fuel level in the air.  Every time a pilot scans their fuel gauges, they want to assess the state of fuel remaining in the aircraft.   To give a pilot  better decision making tools in flight, functional fuel gauges are a minimum requirement.  For this reason the FAA mandated operational fuel gauges for all flight operations.  This capability is critically true if you want to utilize the maximum safe range of your aircraft.

The main problem pilots face is misleading information provided by traditional fuel quantity instrumentation. Even if a pilot knows the fuel gauges to be erratic, they still can lead to bad decision making.  Today, their best option is measuring fuel before flight.  This measurement is  typically made with a wooden stick or glass pipette.  Pilots use this starting known fuel level  and keep track of consumption in flight, but of course, they still run out of fuel.  One key factor missing in this method is knowing exactly among the multiple tanks on the aircraft, just where is the fuel located.    Let's be frank using a stick in a modern aircraft illustrates that we have given up on ever making the fuel gauge work. 

With a bulk of the general aviation aircraft aging beyond 40 yrs, the problem is only get worse over time.

If only there was a better way to measure fuel quantity in the air, then pilots could make better decisions regarding extending flights, balancing tanks or making an extra fuel stop.  This capability would lead to less fuel starvation or exhaustion events and better piece of mind.  With 400,000 general aviation aircraft flying, there is a clear opportunity to meaningfully impact safety on the breadth of worlds general aviation pilots.

Wednesday, March 8, 2017

Lightning Safety - Fuel Senders

Image result for lightning aircraft imageLightning Safety - Aircraft  Fuel Quantity Senders  

It is required to provide in-flight lightning protection in all types of fixed/rotary wing and powered lift aircraft of conventional, composite, and mixed construction and their electrical and fuel systems.  The design of adequate lightning protection for aircraft fuel systems is one the most important lightning protection tasks to be accomplished. 

Government airworthiness certification requirements stress fuel system safety because this system has been responsible for most lightning-related aircraft accidents. 

Elements of the fuel system are typically spread throughout much of an aircraft and occupy a significant amount of its volume They include the fuel tanks themselves, associated vent and transfer plumbing, and electrical controls and fuel quantity instrumentation. 

Careful attention must be paid to all of these components  if adequate protection is to be obtained. The main objective of fuel system lightning protection is to keep ignition of fuel from destroying the aircraft 'during a strike. This goal is quite challenging because thousands of amperes of current must be transferred through the airframe when the aircraft is struck by lightning and a tiny spark of less than one ampere may release sufficient energy inside a fuel tank to ignite the fuel vapor and initiate an explosion. 

There are 4 methods of preventing aircraft fuel hazards from lightning:

  1. Containment - The expansion due to the explosion is contained without structural issue.
  2. Inerting - Introducing nitrogen into the fuel tank. 
  3. Foaming -  Fuel permeable foam like are cars 
  4. Eliminating Ignition Sources

CiES Magnetic Field Fuel Quantity Design embraces #4.   CiES simply eliminates the wiring and the wiring hazard from the fuel volume.    The wiring and fuel sensor element are kept completely out of the fuel volume, if the sender is mounted to the tank surface.   

This methodology eliminates any electrical ignition source from the fuel volume.  

While this issue has not proven to be an issue with some fuels namely AVGAS - lightning induced ignition of fuel tanks containing gasoline is not an unknown phenomenon as demonstrated below in Ohio

So while lightning indirect and direct effects are addressed for the wiring.   Induced effects become paramount for good design.  

Arcing and sparking within the fuel vapor space of a fuel tank is one of the primary concerns of the fuel quantity system designer. The distinction between arcing and sparking is worth reviewing. Arcing is the result of current through the interface between two conducting materials which are making limited electrical contact. Such a condition may exist at the interface of two moving metal components like the CIES rotor and pivot or between the arm and the internal tank surface as shown.

A spark, on the other hand, is an electrical die-charge resulting from a difference of potential across an air gap or along a dielectric material. This condition may exist, for example, in the CiES fuel sender as the metallic components are anodized and teflon impregnated for corrosion protection.  Current through the tank may result in difference of potential between these components. 

By insuring conductivity is maintained throughout the fuel quantity sender this hazard is mitigated.  CiES utilizes clever details to maintain corrosion protection but also to insure induced charges dissipate harmlessly to aircraft grounding structure 

Finally a fuel level sender specifically designed for the aviation market.

Friday, August 12, 2016

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.

Image result for Fuel level sender aircraftNow 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.


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 

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 


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.

Sunday, July 31, 2016

OSHKOSH RECAP - CiES Aircraft Fuel Senders

We are coming to an end of our first trip to OSHKOSH AIRVENTURE.  To say it was a success would be an understatement.  

The three most common comments we heard were 

  • "It is about time that somebody fixed aircraft fuel level" 
  • "Is is STC'd for my aircraft
  • Discussions of personal near miss fuel starvation events. 

Lucky for us several of the alphabet groups decided to stop by and pay us a visit.  They listened as we did, as one by one, potential customers stated all of the above.   

It was a sobering for them.  The magnitude of the issue we have created in aviation, by ignoring fuel quantity indication,  became very evident.

For the first time, somebody other than CiES confirmed  what we hear every working day. 

Fuel indication as we know is less than aviation grade in legacy aircraft.

We are dead set on changing that.  

Saturday, June 18, 2016

AOPA Pilot - May 2013

AOPA Pilot

The press is taking notice of the new digital fuel level senders in the new Cirrus aircraft.

In this case AOPA Pilot and Tom Horne

Here the new fuel level  senders are being discussed with the integration to the standard Cirrus Garmin Perspective Panel.

We agree that accurate fuel level makes it much easier to manage fuel and payload 

The dialogue we started a year and a half ago 

That accurate fuel level in aviation will allow for a higher level of integration, and relieve pilot workload

These innovations are reaching the light of day and in now in production

Tank level balancing and enriched warnings are now reality