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Thursday, March 20, 2014

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.

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:


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. 

  • Do they just give you folklore.

1 comment:

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