Home / News / Safety 1st Alert (SFA): 2025.3 Fuel Truck Fire Highlights Hazards and Underscores Critical Considerations for Annual Meter Proving

Safety 1st Alert (SFA): 2025.3 Fuel Truck Fire Highlights Hazards and Underscores Critical Considerations for Annual Meter Proving

Back Member Updates / August 12, 2025

Safety 1st Alert (SFA): 2025.3

Fuel Truck Fire Highlights Hazards and Underscores Critical Considerations for Annual Meter Proving

August 12, 2025

​​​​​​A fire recently occurred on an Avgas 100LL mobile refueler following a routine meter proving operation. Once the operation was completed, the fuel used for testing was “splash loaded” via the dome cover on top of the mobile refueler.

Splash loading involves introducing fuel into the top of a tank without a drop tube, causing it to fall freely through the vapor space and strike the tank bottom. This method significantly increases static electricity buildup and concentrates flammable vapors — making it a well-known ignition hazard.

In this case, a static spark did ignite those vapors, resulting in a fire. Thanks to the quick response of the local fire department, the flames were extinguished before causing injury. While no injuries occurred, the incident reinforces the critical importance of following proper procedures and fuel quality controls when calibrating refueling equipment. This event has prompted the publication of this SFA with NATA’s GA Fuel Handling Subcommittee guidance for FBOs and other into-plane fuel providers on critical considerations for calibrating refueling equipment each year, including top-loading and fuel quality procedures.

Top Loading Considerations:

  1. Top loading of refueling equipment is never considered best practice and should only be performed in extreme circumstances. Bottom loading is ALWAYS the preferred method
  2. If it is necessary to top load, the operation must be performed in compliance with OSHA’s General Fall Protection Requirements defined in 29 CFR 1910 which requires fall protection where employees are exposed to a fall risk of four feet or more
  3. Top loading should NEVER occur without the use of a metallic drop-tube specifically intended for the transfer of aviation fuels
    1. Purpose of drop tubes
      1. Directs the flow of fuel to the bottom (or near bottom) of the tank
      2. Prevents free fall of fuel through the vapor space (i.e., eliminates “splash loading”)
      3. Reduces static electricity buildup
      4. Minimizes vapor generation, lowering the risk of fire or explosion
    2. Key Characteristics of drop tubes used with aviation fuels
      1. Constructed of stainless steel or aluminum
      2. Must be bonded to the fueling equipment to equalize electrical potential
      3. Maintained in position during the entire loading operation
  4. Top loading shall be performed per
    1. NFPA 407:
      1. 6.2.11.10.1 Where loading tank trucks through open domes, a bond shall be established between the loading piping and the cargo tank to equalize potentials
      2. 6.2.11.10.2 The bond connection shall be made before the dome is opened and shall be removed only after the dome is closed
      3. 6.2.11.10.3 Drop tubes attached to loading assemblies mextending into the vehicle tank shall extend to the bottom of the tank and shall be maintained in that position until the tank is loaded to provide submerged loading
      4. 6.2.11.10.4 Splash filling shall be prohibited
      5. 6.2.11.10.5 The flow rate into the tanks shall not exceed 25 percent of the maximum flow until the outlet (of drop tube) is fully covered
      6. 6.2.11.10.6 Fixed drop tubes permanently mounted in the vehicle tank shall extend to the bottom of the tank or to the inside of the sump to maintain submerged loading and to avoid splashing of the fuel
      7. 6.2.11.10.6 The level in the tank shall be visually monitored at all times during top loading
    2. NFPA 410:
      1. 10.2.4 Fuel transfer operations shall have at least two dry chemical extinguishers, each having a minimum 9.1 kg (20 lb) agent capacity and agent discharge flow rate of 0.45 kg/sec (1 lb/sec), located in the immediate vicinity
      2. 4.1.10.3 ABC multipurpose dry chemical fire extinguishers (ammonium phosphate) shall not be placed on aircraft fueling vehicles, airport fuel servicing ramps or aprons, or at airport fuel facilities that are located within 150 m (500 ft) of aircraft operating areas

Fuel Quality Control Considerations:

  1. Where the proving tank or hopper is used for multiple types and grades of fuel, it shall be flushed with product to be tested until equipment is clean and samples are 1A clean and bright BEFORE testing begins with aviation fuels
    1. Avgas equipment should be proved prior to Jet-A due to it’s quick evaporation
  2. After proving is complete, perform API gravity testing prior to returning fuel back to storage. API gravity test should be performed on:
    1. The fuel in the receiving storage tank
    2. The fuel being returned to storage
    3. Both must be on specification (+/- 1 degree API)
      1. If off-spec, fuel should be properly disposed of and not returned to storage
  3. The return of fuel to storage should be supervised by or performed by FBO or refueling operator staff, not the third-party performing the meter proving