Cirrus Aircraft Fuel Level Retrofit - Video

Cirrus Aircraft Fuel Level Retrofit 

We set out to change fuel level in Aviation.  We wanted to demonstrate that accurate and reliable information on fuel quantity could be accomplished in single engine and other aircraft.

The concept has literally taken off.  

We have proven they we can measure fuel in a highly dynamic environment and we can do so accurately.   


Click Here for Cirrus Inflight Video 

Measuring Fuel ... How Do you Measure Up?

I have been trying to track down this exact "Pilot Folklore" regarding fuel level in aircraft.
  
Specifically the widespread pilot belief that the FAA doesn't require for you to have working fuel gauges in your aircraft.

The gauges only need to tell you when you're empty.

Sure enough in a FAA Safety Bulletin in April 2002
The FAA said just that - the exact words as follows:

 As you can see, the regulations only require that the aircraft fuel gauge read “zero” during level flight when the quantity of fuel remaining in the tank is equal to the unusable fuel supply determined under 14 CFR §23.959(a).  Therefore, the gauge cannot be depended upon for checking the fuel quantity in a tank. This is especially true of the smaller, less sophisticated general aviation aircraft. Visual or physical checking or both are the only safe means of determining the actual quantity of fuel onboard such aircraft. How do you measure fuel? Do you measure up?  H. Dean Chamberlain 

In fact,  as recently as February 2013, the FAA allowed this to be reprinted in a blog site... unbelievable.   Supporting a culture where it is acceptable for "Fuel Exhaustion" to be one of the TOP 5 GA Incidents, and according to the AOPA Nall Report the second highest cause of pilot death.

In most cases pilots will blame  pilot behavior and preflight.  All pilots will rally to the aviator cause, and like this FAA article, seek to change the an obviously errant pilot procedure.   .... Education is the tool to address this serious safety issue .  Despite the efforts, the number of fuel exhaustion incidents still remain high.
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So back to the fuel gauge ....  I have been through over 150 certification meetings in my life - 

But I have not yet brought in a new aircraft or new aircraft modification and told the Administrator that; 

I removed the fuel gauge and  replaced it with an idiot light letting the pilot know -

"That at this very moment you ran out of fuel"  

or propose an aural announcement like:

 "WARNING YOUR ENGINE WILL NOW STOP... PLEASE LOOK FOR A SAFE LANDING & HAVE A NICE DAY"

But according to the FAA author above - that is exactly what the administrator is looking for in an aircraft design  ....

...   REALLY,  What pilot or aviation professional believes this?


 So what do the FAR's (Federal Airworthiness Requirements) really say:

Title  14 Code of Federal Regulations (CFR) §23.1337(b), Powerplant instruments installation.

  It reads:

(b) Fuel quantity indication. There must be a means to indicate to the flightcrew members the quantity of usable fuel in each tank during flight. An indicator calibrated in appropriate units and clearly marked to indicate those units must be used.

It says you have to have a fuel gauge and it needs to show you the amount of fuel in your tank in flight.  It says that in fairly clear language. 

In  addition:  

(1) Each fuel quantity indicator must be calibrated to read “zero” during level flight when the quantity of fuel remaining in the tank is equal to the unusable fuel supply determined under 14 CFR §23.959(a);

It says that the fuel gauge must have the capability to be be calibrated to read zero usable fuel.  This feature is an added part (In addition) to the requirement that it must  let you know how much fuel you had in total,  when the aircraft is in flight.

Does anyone believe that the FAA would have you put a fuel gauge in an aircraft and 
let that gauge

• Indicate any value fuel level other than zero.
• When you were at zero usable fuel it will read "ZERO"

According to this skewed interpretation of the regulation.

A binary gauge meets this folklore requirement   ... 

•  "SOME FUEL"

to be followed by a calibrated  

• "NO FUEL" 

Well the FAA actually expects something dramatically MORE Accurate 

in FAA TSO C55a -

- No more than 3% of full scale tank volume in the worst case -

Minimum Performance Standard for Fuel and Oil Quantity Indicating System Components, 

When you get in your aircraft and you look at your fuel gauges.

• Do they meet the real and intended FAA standard. 

or 

• Do they just give you folklore.

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 

   

What Accuracy in Fuel Level Means for General Aviation

Why would I want accurate fuel gauges in my aircraft. 

Predicting and shaping the future are the providence of engineers.  

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

What are the effects on the aircraft/pilot interface.

Warnings and Annunciation 

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

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

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

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

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

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

Automation 

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

Fuel  Management Computer - 

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

• Fuel Management. 

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

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

How Do You Inspire Pilot Confidence

- The Answer is Simple -

You Provide Them with Information They Can Trust 

It seems uncomplicated, ... accurate, reliable and trusted information is key to instilling a conviction that everything is going well.

Imagine a Synthetic Vision System that throws a few imaginary mountains at you, just for fun.   This would not be a system that inspires confidence.    Random false information would make a routine IFR flight more stressful and  stomach clenching even if you knew without a doubt that no mountainous terrain exists at any time in the State of Illinois.

  Conflicting information no matter how outrageous or unbelievable adds to pilot workload.

Cross checking normally reliable sources and getting similar results are the hallmarks of a good pilot.  Minor anomolies in calculation or display can be noted and corrected before a situation occurs.  To make this effective, any display in the cockpit should match what the pilot believes to be true most of the time.

In aircraft fuel level systems - reliable trusted information is hard to come by.

Pilots Trust in Fuel Sight Gauges 

Ignoring the issues of having a flammable substance with clamped connections on transparent and UV susceptible tubing or a fragile glass tube in the cockpit  - pilots trust seeing fuel as the most confidence inspiring  vs. any other method of level gauging.   If I can see it,  I have fuel and I know how much.   If I can't see it,  I don't have fuel in that tank.   I trust it, universally most pilots do.   But the limitations (high wing mostly)  revolve around the visibility of fuel  - Cessna uses a ball on the 162 Skycatcher.  But really these systems are best left in the dark.

Pilots have Faith in Capacitive Fuel Gauges

Professional pilots use them, they are the system of commercial aviation.  I hear from pilots that capacitive systems have no moving parts and are exact and reliable,  these pilots have not taken a careful look at commercial systems or the problems and solutions contained in a commercial or business aircraft system.   Good capacitive systems are expensive - the have extensive compensation for the fuel characteristics,  like temperature, water, entrained air, component corrosion These are all part of the capacitive equation for fuel level.   Good commercial Capacitance level systems compensate for this,  systems that rely on the capacitive reputation and fail to compensate or address these issues leave quite a bit to be desired.

Pilots will Believe in Anisotropic Magneto Resistive 

While more difficult technology to grasp,  digital output for fuel level from a float based system truly represents a real breakthrough in fuel level sensing.  

• It is safe, reliable - no wear parts
• There are no electronics in the fluid
• It is compatible with modern cockpit displays
• The fuel flow totalizers will match fuel quantity - giving you a truly redundant system in the cockpit.
• Provides a level output under extreme conditions

Youtube Video of the Sender under Test