SMO — Residents upset over what they said was a drastic increase in flights from Santa Monica Airport over their homes earlier this year are blasting a City Hall-funded study presented this week that found there had been no significant increase in noise levels.

The study by Mestre Greve Associates looked at flight data from a six-month period, beginning last December when the FAA began testing a new takeoff route, known as a 250 degree heading, for some small piston-powered planes. It concluded the test resulted in an average of eight additional flights over residential neighborhoods in Santa Monica, causing no substantial noise increase under FAA standards.

Lisa Hughes, a co-founder of the group Neighbors for a Safe & Healthy Community, which formed after residents filed thousands of noise complaints during the FAA’s test period, said City Hall’s noise analysis was “absolutely ridiculous.”

Scores of residents have confirmed that the six-month test resulted in heavy flyover traffic, she said, not a modest increase of eight planes per day.

“I just cannot understand why the city would pay for a study that doesn’t deal with reality,” she said.

The study’s flaw, she said, was that it took into account only planes flying under so-called “instrument flight rules (IFR),” which receive specific flight path instructions from the air traffic control tower. The majority of pilots operate under “visual flight rules (VFR)” and have a greater amount of flight path leeway.

The FAA’s test required only single engine piston-powered planes flying under IFR rules to take the 250 degree heading, which sends pilots in northerly direction over the Sunset Park and Ocean Park neighborhoods, as opposed to south over the Penmar Golf Course. But Hughes and other residents have said they suspect many VFR pilots opted to take the 250 degree heading as well during the test period, causing the spike in airplane noise.

Whether to analyze data from all flights out of SMO during the test period or to focus on only the IFR flights has been a point of contention between residents and City Hall.

Airport Director Bob Trimborn defended the decision to analyze only the data from IFR flights: those are the only planes the FAA will consider when it conducts its own analysis of the test route in order to determine whether it should be permanent, he said. So looking at data the FAA considers irrelevant isn’t likely to have any effect.

“We’re dealing with the FAA and they’re the ones that are going to make a call on whether there’s a significant impact or not,” he said.

But Hughes said the whole point of the city’s independent noise analysis was to gauge the true impacts of the FAA’s test on the community, not to replicate the analysis the FAA is expected to produce.

“I want [the city] to come out with the truth,” she said. “There are people that live on my street that have lived here for 25 plus years, [and] they tell me they have never seen this kind of plane activity over the neighborhood.”

The noise study was presented to the city’s Airport Commission on Monday. Not every commissioner was entirely satisfied with its findings.

E. Richard Brown, the commission’s vice chair, said the noise study “didn’t give us the full analysis we were looking for” but was useful as a tool to understand the limits of what a noise study can achieve.

There’s no plan yet to conduct an additional study that would look at all of the flight data, including VFR takeoffs, though Trimborn said discussions about commissioning a further analysis are ongoing.

One possible barrier is the cost.

Trimborn said it would be “very time consuming” to analyze VFR flight data because it would require transcribing months worth of audio recordings of communications between pilots and the air traffic control tower.

nick@smdp.cm