Amateur-built aircraft like the one that crashed through the roof of a Methuen condominium building on Tuesday have faced increasing scrutiny from the Federal Aviation Administration in recent years as interest in these types of planes has taken off.

The experimental Sonex plane fell from the sky as it was approaching Lawrence Municipal Airport for landing early Tuesday afternoon -- killing the pilot, former Newburyport Mayor Alan Lavender. The crash has raised concerns from the community about the safety of home-built planes and the experience pilots need to fly them.

In addition to referring to unproven designs, the term "experimental" in aviation is used as a designation for home-built aircraft, even those based on well established designs. 

National Transportation Safety Board (NTSB) air safety investigator Aaron McCarter said "it's very common" for pilots to build their own planes. The FAA documented 27,922 active aircraft across its various experimental airplane categories in 2015. Of those, 21,195 are classified as amateur, making home-built airplanes just more than 10 percent of the 210,030 general aviation and air taxi craft in service that year.

But with experimental planes come safety concerns. Amateur-built and other experimental aircraft were involved in more than 25 percent of fatal general aviation accidents in the United States over the past five years, while only accounting for an estimated 5 percent of total general aviation fleet hours, according to the FAA. 

"General aviation" refers to all civil aviation operations other than scheduled air services and air transport operations for hire. It includes private planes, gliders, corporate jets and other such flights.

A 2012 NTSB study into experimental amateur-built aircraft said the planes accounted for a “disproportionate number of total accidents and an even more disproportionate number of fatal accidents,” when compared with similar non-home-built aircraft doing similar flight operations. That study resulted in several recommendations from the NTSB related to aircraft certification, flight testing and pilot training.

However, with an increased focus on safety and education efforts in the years following that study, the number of fatal accidents for experimental planes has decreased in recent years, according to the Experimental Aircraft Association (EAA).

“What we've seen from that emphasis in safety over the past five years is a significant drop in the number of fatal accidents in amateur-built aircraft,” said EAA spokesman Dick Knapinski.

He added, “This is a safe pursuit to begin with, but in a safety sense one (fatality) is always too many, so you always want to make sure you can get that number down.”

'It was well built'

Lavender's 2016 Sonex airplane was one of 16 experimental aircraft based at Lawrence Municipal Airport, according to airport manager Michael Miller. There are 215 aircraft based at the airport, though not all of them are airworthy, he said.

The former Newburyport mayor built the plane himself over the course of about three-and-a-half years, said Bob Di Meo, vice president of EAA Chapter 106, which is based at the airport and serves the greater Boston area.

Di Meo had been involved with Lavender's build, advising him over the last eight months or so of the plane's construction. The last time he had any direct involvement with the Sonex was when Lavender asked him to look over the plane just before its official inspection.

Di Meo said he “spent several hours climbing over the aircraft,” asking questions and looking at the plane's construction plans.

While he hasn't built a Sonex aircraft, Di Meo constructed his own Van's RV-8 aircraft and serves as a technical counselor for his EAA chapter. He told Lavender the plane “looks pretty good to me,” and the Newburyport man had the inspector come.

That inspector “found nothing,” Di Meo said.

“That made me feel really good because that means I didn't miss anything and really that was the last time I looked at the aircraft,” he said. “To me it was well built, it was sound, the engine, the wiring, the instrumentation all looked like I would do it.”

Extensive inspection process

To qualify as an experimental amateur-built aircraft, builders must construct at least 51 percent of their plane, according to the FAA. Many of these airplanes come from kits made by manufacturers, including from Sonex and Van's -- one of the more popular models in the country -- that are designed to meet that requirement.

The build and certification process for these planes is extensive.

Di Meo, of Bedford, New Hampshire, said it took him about eight years to construct his RV-8 plane. He ordered the first piece of his kit in 1998 and finished the project in 2005. He built the wings and tail in his basement; the fuselage, engine and instrumentation work in his garage; then took it to the airport and spent another year assembling the plane for flight.

“The FAA actually says that part of the experimental aircraft reason is to be that it's educational and its recreational. That's the premise that we build our aircraft on, to learn and enjoy ourselves,” he said.

The kit planes come with construction materials, instructions and blueprints.

“Every little thing including all the rivets and the screws and nuts and washers is specifically spelled out,” said Roger Pascoe, of Salem, New Hampshire, who owns and operates a home-built plane.

While Pascoe didn't build the Van's RV-8 he now owns, he does the maintenance work and has a thick stack of blueprints and a binder-full of instructions for the plane in his hangar at Lawrence Municipal Airport. Lavender's Sonex aircraft would have had similar materials, he said. Pascoe noted that manufacturer's website also provide updates to the instruction materials based on feedback from the field.

Before it can fly, a plane must be deemed airworthy by either an FAA official or a designated airworthiness representative (DAR).

“They go through a very intensive inspection of the aircraft to make sure as much as possible that the aircraft has been built reasonably well and that it can operate as an airworthy aircraft,” Di Meo said.

Once the plane is approved, the inspector gives the pilot a set of operating limitations, parameters within which to test the plane during its initial hours in flight. For instance, the plane must be flown between 25 and 40 hours over "unpopulated areas" before the pilot is allowed to carry passengers, pilots said.

The planes are then inspected every year or 100 hours of flight time, whichever comes first, Knapinski said.

Along with certifying the plane, pilots must also be appropriately licensed.

“Pilots need the same kind of training and recurring training as (they would to operate) the small Cessnas you might see at a local airport,” he said, referring to a line of factory-made planes.

Lavender's plane received its certification in 2016, and records show he is listed as the manufacturer of the plane.

Studying safety

What caused Lavender's plane to crash into Building 7 at the Prides Crossing condominium development early Tuesday afternoon while approaching Lawrence Municipal Airport for landing remains unclear, and will for some time. A preliminary report into the crash is expect this week, while a full report could take up to a year, and a final report could take up to a year and a half to materialize.

Di Meo doesn't know what went wrong in Lavender's last flight.

“It was like nine months, 10 months ago that he made his first flight and he was flying it fairly regularly,” Di Meo said of Lavender. “It sounds to me that he had gone over the hump of the highest risk part of it.”

According to accident analyses from its 2012 study, system failures and in-flight loss of control were among the most common types of accidents for experimental amateur-built aircraft. The NTSB undertook the study in part due to safety concerns about these types of aircraft and the lack of “contemporary and definitive analysis” of their safety. The EAA provided information for the study.

The study showed that fatal accident rates were generally higher for home-built aircraft over their counterparts, which include all single-engine piston-powered airplanes and helicopters, balloons and gliders that were not certified in that category. For instance, the accident rate per 100,000 flight hours – time spent in the air – for the experimental aircraft was between 2.5 to 3 times higher than that of their counterparts between 2001 and 2010. The fatal accident rate averaged about 4 times greater, the study said.

Based on its findings, the NTSB issued 12 recommendations to the FAA and four to the EAA. That included expanding documentation requirements for initial aircraft airworthiness certification, verifying the completion of the first phase of flight testing and improving pilot access to transition training efforts. It also encouraged the use of recorded data during flight testing and made recommendations about proper documentation and aircraft identification in registry records.

Making improvements

Following that study, Knapinski said the EAA undertook several efforts to enhance safety, including participating in the General Aviation Joint Steering Committee, a public-private partnership to improve general aviation safety.

The FAA has also since approved the optional Additional Pilot Program where a second licensed pilot can be in an experimental aircraft during the first phase of test flying “to help monitor the critical systems and make sure everything's working properly,” Knapinski said.

In July of 2016, the FAA reported that loss of control remained the leading cause of fatal accidents for this type of airplane.

However, with the help of these education efforts and updated safety materials, experimental planes were “showing improvement,” the agency said.

Data provided by Knapinski and the EAA showed a drop in fatal accidents over the past few years.

Between October 2015 and September 2016, there were 33 fatal accidents reported in home-built aircraft, down from 40 fatal accidents in the previous reporting year and 51 in the year prior to that.

“The fact that you have probably twice as many airplanes as you did 25 years ago, but the total number of accidents is dropping, it speaks to the safety of people who build and own these aircraft,” Knapinski said.

The two pilots, Di Meo and Pascoe, have also noticed the trend of increased education and safety efforts.

Pascoe has been flying since he was a teenager. He's flown about two dozen different types of aircraft and prefers experimental planes for their enhanced performance features like aerobatics and speed. As the home-build field grows, oversight and outreach efforts increase as well, he said.

“The EAA has really mushroomed out and has training classes now and has promoted local chapters in doing the same,” he said. “Builders, when they buy kits, are encouraged to contact local chapters and get in touch with people building similar airplanes.”

Di Meo also serves as a flight adviser, helping plane builders better learn the characteristics of their airplanes and how the nuances of how they fly.

“To us it's become a pretty safe endeavor as long as (pilots) approach it carefully,” he said.

Follow Lisa Kashinsky on Twitter @lisakash23.

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