Royco 950 in Fuel Systems Calibration

The fuel system on aircraft is definitely one of the most unsung heroes of the entire aircraft. It holds fuel and transfers fuel, right? Basically. But what happens if something goes wrong with the system? What if it is sensing fuel flow incorrectly? Or sense weight incorrectly in a tank? Very bad things, that is what happens. 

Fuel system components require careful calibration, like other critical parts of the aircraft, and for these critical systems, a special fluid is used for the safe and accurate calibration. Royco 950 is the fluid of choice for fuel system calibration for both piston and gas turbine aircraft engines. It is also a MIL-SPEC fluid, meeting MIL PRF 7024E. 

Royco 950 Overview

So, what is Royco 950, and specifically, what is calibrating fluid? 

Royco 950 is a Stoddard solvent fractionation with stabilizers for calibration of aircraft fuel system components in reciprocating and gas turbine engines. That word salad sounds confusing, so what does it mean?

Stoddard solvent fractionation refers to a complex process of separating the different hydrocarbon components within Stoddard solvent. This is typically achieved through techniques such as distillation. 

To be used on military aircraft, all liquids must meet a military performance standard, or MIL-PRF. Royco 950 meets military spec MIL-PRF-7024 Type 2 for high quality and reliability in fuel system calibration.

It is also formulated as a solvent to prevent gums and peroxides from forming in fuel system components. Gums are the death blow to fuel systems that are extremely sensitive to build-up, sludge, and, of course, gumming. 

Aircraft Fuel System Components

Alright, so what types of fuel system components need calibration fluids for maintenance?

Fuel Pumps and Injectors

It is very important to make sure that fuel pumps are moving fluid correctly and at the right rate, and Royco 950 does just that. Fuel injectors are just as sensitive (if not more so); fuel injectors have defined fans and spray patterns, so clogs and gumming throw all of that off. 

Technicians need a calibration fluid to check the pattern and flow of fuel pumps and fuel injectors, and this is the one. 

Fuel Level Sensors

There have been several very high-profile fuel exhaustion events over the years, and fuel level sensing is always high on the list of things to check. Sensors are usually float-style sensors that have an electrical input, which sends the calibrated quantity to the fuel management system. Royco 950 calibrates fuel system components in reciprocating and gas turbine engines, which makes sense since the fuel sensing systems are similar. 

What Is Calibrating Fluid?

So, in common terms, calibrating fluids are fluids that are made to safely mimic or replace the fluid in question for testing purposes only. It must have similar qualities to those of the fluid being tested to give an accurate reading when those systems and system components are being tested.

Using actual fuels in a shop environment is not favorable, so a replacement fluid is created for the job. 

What Is MIL-PRF 7024?

MIL-PRF-7024F is a military specification that defines the requirements for calibration fluids used in testing and verifying the performance of aircraft fuel system components. 

These fluids are used to calibrate sensitive fuel system equipment without introducing the variability or hazards of actual fuel. The specification defines three fluid types: Type I (Normal Heptane), Type II (Special Run Stoddard Solvent), and Type III (High Flash Point Fluid), each with distinct flash points and performance characteristics for various test environments.

The fluids are 100% hydrocarbon and must meet strict requirements for specific gravity, viscosity, flash point, vapor pressure, and chemical stability. They must be clear, free of sediment, and non-reactive with system components. Corrosion inhibitors and antioxidant additives can be blended into the fluids to improve storage life and prevent degradation or residue formation during use.

Safety and environmental considerations are built into the spec—fluids must be low toxicity and have minimal benzene. All branches of the US military use MIL-PRF-7024F, which helps maintain fuel system integrity across multiple aircraft platforms by ensuring consistency and reliability during calibration.

Good Information to Know About MIL PRF 7024 calibration fluid

Here are a few important facts about MIL-PRF-7024, and, in effect, Royco 950. 

  • The total shelf life for products meeting MIL-PRF-7024 specifications is 730 days.
  • MIL-PRF-7024E supersedes MIL-C-7024D and covers calibration fluids for aircraft fuel system components.
  • Royco 950 has a maximum recommended shelf life of 2 years from the date of manufacture.
  • Royco 950 has a kinematic viscosity of 1.17 ± 0.05 cSt at 25°C.
  • Royco 950 has an initial boiling point of 158°C and a final boiling point of 200°C.

Greenwood Aerospace Can Source Your Next Order of Royco 950

Greenwood Aerospace is your first call for aviation-grade lubricants, sealants, and yes, even calibrating fluid. We are an authorized distributor of Royco 950 and provide it in 55-gallon drums for your biggest jobs. When calibration cannot wait, you don’t have to. Give us a call at (580) 762-2580 or email us at contact@governmentprocurement.com, and we will get you all set up.