Why The Size of Fuel Hoses On Self-Serve Systems Is So Important!

by Dave Weiman
Published in Midwest Flyer Magazine August/September 2019 issue

If you have never thought about the size of the hose at airport self-serve fuel systems, you are not alone. I didn’t either until last winter while self-fueling our Cessna 182 Skylane at a rural Wisconsin airport. It was then and there that I noticed the airport installed a fuel hose normally used for JET A fuel, and not for an over-wing self-serve fuel system for 100LL.

Single-point fueling (or pressure refueling) is a method of refueling an aircraft from a single point on the aircraft, rather than over the wing. The fuel hose is attached to a point on the aircraft, and the current tank valves are then opened. Some aircraft are gravity refueled through a single point as well.

The hose at this airport was so large in diameter that it was cumbersome to handle…would not rewind on the reel…and pumped such a large volume of fuel that it over-flowed all over my wing – not once, but on two separate occasions! A waste of fuel, potentially damaging to the paint, not good for the environment, and a mess on the tarmac.

Over-wing fuel hoses on JET A refueling trucks are typically 1.25-inch I.D. (inside diameter) x 1.73-inch O.D. (outside diameter) x 50 feet in length. JET A over-wing nozzles are required to have a duck bill style spout (OPW # 295SAJ-0200), which will prevent misfuelling. The airport I was at used a 1.25-inch I.D. x 1.73-inch O.D. fuel hose, but for over-wing self-fueling of 100LL, and apparently, the pressure could not be adjusted (or wasnt), like it can with single-point fuel systems. Additionally, the nozzles used to refuel piston aircraft are typically smaller 1-inch or 1.25-inch with a small 1-inch (O.D.) round spout.

Most of the JET A refueler trucks used by fixed base operators (FBOs) for single-point refueling have a 2.0-inch I.D. x 2.6-inch O.D. fuel hose 50 feet in length, which weighs about 64 lbs. The single-point fueling operation on an FBO JET A refueling truck has a flow rated between 200-240 USGPM (U.S. gallons per minute). Flow rates can vary on a JET A refueling truck depending on the aircraft being refueled.

Picture yourself trying to lift and maneuver a heavy/inflexible hose from one side of your aircraft to the other without hitting the wing, cowling or propeller, and climbing up and down a ladder with the hose not once, but twice. Remember, all along, you have a static line clipped to a metal surface somewhere on the nose of your aircraft, which you must avoid disconnecting.

Now picture yourself on a ladder pumping fuel at a rate more than 22 gallons per minute (GPM) – a rate so fast that you cannot release the handle on the fuel nozzle quick enough to stop the flow, and fuel overflows on top of your wing. In comparison, a 1-inch I.D. fuel hose intended for over-wing fueling pumps fuel usually at a rate of 15-20 GPM and the handle is therefore much easier to release.

Okay, you have refueled your aircraft. Now you must rewind the hose using a manual reel – tension or crank – only to find out that the hose is so large that there is not enough room on the reel for the remaining 15 feet. You have no choice but to let the hose lay on the ground, or try wrapping it around the reel. This not only presents another possible safety concern, but it doesn’t look very good, either.

Shortly after my incident with the new hose, I learned that a neighboring airport had a completely new self-serve fuel system installed by the same company, and they installed the correct hose for over-wing self-fueling. The specifications for that hose are as follows:

Over Wing Aircraft Fueling Line

15-30 GPM adjustable flow regulation, 1 1/2” pipe, s. s. swivel joint, 1⁄2 HP motor operated electric hose reel for 1″ hose, no fast retrieve (hose reel to be geared slower than normal, 98 f/m ratio 12:25 retrieve speed). Clutch release. Back up hand crank. Stainless steel hose alignment roller assembly to keep hose on reel and not rub on cabinet with space to stow the nozzle inside the cabinet. Pressurized hose must fit on the reel. Paint a red strip on the hose where it is at the top of the reel in the normally stowed position. (Shows the user where to stop the retrieve.)

75′ of 1″ aviation approved hose meeting API bulletin 1529, 5th Edition, 1998, Grade I, Type C and NFPA #407 (2017 edition), (shop tested and certified), 1″ nozzle inlet swivel joint, 100 mesh strainer, OPW 295 1″ aviation type nozzle, 100 mesh strainer, 1″ x 1 1/4” x 1” or equal with hose ground wire, heavy duty clip, dead man manual nozzle control (NO AUTO FILL OVERRIDE), and dust cover for fueling nozzle.

Bret Swan, President of “Minnesota Petroleum Services, Inc.” of Minneapolis, Minnesota, which was NOT the firm that installed the fuel hoses at either of these two rural airports, said that a “1-inch (I.D.) hose is overly common and manageable. I just filled my plane (Cirrus SR20) with a 1-inch system at the airport in Montevideo, Minnesota on a new system we built and it was flowing at 22 GPM. The weight of the 1-inch hose was super manageable and friendly. Airports do not need more than 15-20 GPM for general aviation aircraft.”  The larger the hose, the faster the fuel flow rate, and messes are made.

Another fuel system professional we contacted confirmed this information, stating that the maximum pump flow rate is what determines the diameter size of the hose. According to that individual, a self-serve system for AVGAS 100LL and SWIFT UNLEAD that is flowing less than 50 USGPM would not require a fueling hose larger than 1-inch I.D. Flow rate in the 25 USGPM range could use the smaller 3/4-inch I.D. fueling hose. The larger diameter fueling hoses are typically for JET A systems that pump 100, 200, 300 and 400 USGPM and higher.

If you are pumping faster than 50 GPM over-wing into small aircraft, “splash back” could be a problem. If the hose has a 1-inch I.D., the weight is much more manageable and the hose is easier to handle for self-serve systems. “Trying to reel in a long length of hose on a wet or snowy pavement can also be tricky,” he said. Also, low temperature hoses in the range of -67 F to 158 F will not stiffen in cold Midwest winters and are much easier to handle.

The following data sheet, provided by a major aircraft fuel hose manufacturer, shows both the inside diameter (I.D.) and outside diameter (O.D.) of fuel hoses, and the weight in pounds (lbs) per foot (ft) in length:
0.75 I.D. X 1.22 O.D. inches0.40 lbs/ft
1.00 I.D. X 1.45 O.D. inches0.54 lbs/ft
1.25 I.D. X 1.73 O.D. inches0.67 lbs/ft
1.50 I.D. X 2.00 O.D. inches0.81 lbs/ft
2.00 I.D. X 2.60 O.D. inches1.28 lbs/ft
2.50 I.D. X 3.11 O.D. inches1.61 lbs/ft
3.00 I.D. X 3.58 O.D. inches1.88 lbs/ft
4.00 I.D. X 4.56 O.D. inches2.49 lbs/ft

We also learned that aviation grade refueling hose assemblies must be hydrostatic tested and certified to 600 PSI (Pounds per Square Inch). A copy of the hydrostatic test certificate must be supplied with the hose when it is sold, and kept on file until the hose is replaced because of wear or once it has reached its time limit (10 years is maximum).

The Federal Aviation Administration (FAA) expects fueling installations, trucks, etc., to conform with National Fire Protection Association (NFPA) standards. See Code NFPC 407. In addition, airports follow local and state codes and sometimes Air Transport Association (ATA) and National Business Aviation Association (NBAA) guidelines.

Self-serve fuel systems are increasing in popularity and are a great contribution to general aviation in helping to reduce costs and increase accessibility. We just hope that the industry realizes the importance of providing self-serve fuel hoses which are safe and easy to handle. We also hope that in addition to installing the correct fuel hose for over-wing self-fueling, airports realize the importance of maintaining safe “static lines.” All too often static lines or tension reels are broken by pilots who prematurely release them. As pilots, let’s do our part to keep systems safe and in good operating condition.

I welcome your input on this and other topics that affect your flying. Email dave@midwestflyer.com.

DISCLAIMER: The information contained in this editorial is the expressed opinion of the author and those referenced. Readers are advised to obtain additional information on this topic and seek the advice and assistance of others, such as federal, state and local authorities; airport engineers and consultants; and fuel equipment manufacturers, suppliers and installers, before arriving at any conclusions.

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