Sometimes they burp. Sometimes they spew. Sometimes they simply drizzle.
Airplanes have a number of ways of relieving the pressure of the fuel in their wings when it grows too high.
And they’re doing it too much at Scottsdale Airport, said airport advisory commissioner Mike Osborne. “It seems like every couple of meetings, there is a report of a fuel spill,” he said.
Fuel spills are fairly common at airports, but the volatile liquid can spark a fire or seep into the groundwater if not handled correctly.
Scottsdale Airport sees a number of fuel spills each year, and the incidents are increasing.
Between 2004 and 2005, the number of fuel spills at Scottsdale Airport doubled, from nine to 18.
In comparison, Williams Gateway Airport reported 18 spills in the last three years. Scottsdale Airport had 39 in the same time.
Whenever a spill occurs in Scottsdale, the incident must be reported to the airport director within two hours.
If the spill covers 50 square feet or more, the airport requires a call be made to the Scottsdale Fire Department.
The department wa s called for 20 of the 39 spills since 2003. Airplane fuel can break down and soften asphalt on the tarmac if not cleaned up promptly. “We have to make sure it’s cleaned up so it doesn’t get into the spillwater system,” said Scott Gray, aviation director.
Usually, fuel spills are between one and five gallons and can be cleaned up with an absorbent resembling cat litter that is then swept up and disposed of according to city and state guidelines, said Cathy Gedvilas, spokeswoman for Landmark Aviation, a fixed-base operator — a provider of fueling and other airport services.
Landmark Aviation recently acquired Corporate Jets, a fixed-base operator that was involved in the spills and the cleanup in nearly all of the incidents reported at Scottsdale Airport.
Usually, the firefighters monitor the situation to decide whether a hazardous-incident team is necessary, said Capt. Jim Novotny.
Reports show that such a team has been called only once: About 6 a.m. on Sept. 14, 2003, an airport official noticed a Cessna Citation 750 was leaking profusely from its left wing. An estimated 200 gallons was spilled, some of which seeped through the pavement into the soil. The cleanup took more than four hours.
The fire department also provides support in case of fire, a risk that increases during the summer.
When air temperatures rise past 100 degrees, the asphalt at the airport gets even hotter. In rare cases, if the asphalt is hot enough, spilled fuel could flash into a fire, Novotny said.
Higher temperatures also increase the likelihood of a fuel spill.
Three of the fuel spills at Scottsdale Airport in 2005 were attributed to thermal expansion, a process in which the jet fuel heats up and expands, causing a plane’s fuel tank to spontaneously vent some of the fuel.
“It’s just like any other liquid. When you heat up water, it expands a little bit,” said Bill Gott, president of the Scottsdale Pilots and Aviation Association. “It’s like if you fill up a water bottle and leave it on the windshield in the car, then you take the top off and it squirts you.”
According to the incident reports filed with Scottsdale Airport, the causes of fuel spills include an overfilled tank, a stuck valve that allows fuel to drain out and a failure in the fuel tank’s automatic shut-off system, which is supposed to shut down when the tank is full.
In one spill report, a pilot claimed somebody stole his airplane’s wing gas cap. In another, a fueling employee said the airplane “burped.”
Both Osborne and Gray said fuel spills are common.
Osborne said most of the spills are caused by airplane malfunction.
The rest are simple mistakes.