N550LX

On January 28, 2023, about 1542 eastern standard time, an experimental amateur-built Lancair 4P airplane, N550LX, was destroyed when it was involved in an accident at the Hartford-Brainard Airport (HFD), Hartford, Connecticut. The private pilot was seriously injured. The airplane was operated by the pilot as a Title 14 Code of Federal Regulations Part 91 personal flight.

According to the pilot, he planned to fly to Groton-New London Airport (GON), Groton, Connecticut, to conduct instrument approaches. He did not notice any abnormalities with the airplane during preflight and taxied for departure. The pilot reported that he aborted the first takeoff because “something was not feeling right” with the airplane. After returning to the ramp and taxiing around briefly, he decided to attempt another takeoff because he did not observe anything obviously wrong with the airplane.

The pilot reported that, during the second takeoff, the airplane immediately rolled left after rotation. He reported that the first thing through his mind was, “I gotta get this plane on the ground.” He recalled that engine power was normal and, due to the left banking tendency, he started pulling back on the power to reduce thrust. Subsequently, he attempted to complete a landing in the grass to the left of the runway, but “the plane just kept going to left” despite his attempts to lower the right wing with the flight controls. He recalled that the left wing hit the ground first; he saw sparks and then was ejected from the airplane. The pilot crawled away from the postimpact fire and was rescued by first responders.

Review of airport surveillance video found that the airplane taxied from the ramp to runway 20 before taking off. The airplane accelerated with the pilot subsequently aborting the takeoff before becoming airborne. The airplane returned to the ramp and completed a 360° right taxiing turn before proceeding back to runway 20 a few minutes later.

During the second takeoff, the airplane accelerated and rotated near the runway’s 1,000 ft markers. Immediately after rotation the airplane entered a left roll, climbed momentarily, and then entered a steep left roll and left turn toward the terrain to the left of the runway. The airplane continued in a 90° left roll and subsequently impacted terrain in a left turn when the airplane cartwheeled and an explosion and postcrash fire immediately ensued.

A Federal Aviation Administration (FAA) inspector performed a visual examination of the airplane and photographed the accident site. The initial impact ground scar was about 475 ft from the runway and the fuselage came to rest about 260 ft from the initial impact point. A postimpact fire consumed a majority of the composite airframe structure.

According to the FAA airworthiness and registration records, the airplane was an experimental amateur-built Lancair 4P. It was issued an airworthiness certificate in 1999 and originally configured with a Continental Motors TSIO-550 piston engine. In August 2019, the airframe, engine, and its systems were heavily modified into an RDD Enterprises LLC model LX7-20 turbine airplane. The wings were lengthened, the airplane was about one foot longer, and its tail height was about 2 ft taller. A Pratt & Whitney Canada T74-CP-700 turbine engine was also installed.

According to the company who performed the modifications (RDD Enterprises, LLC), the LX7-20 was a pressurized, 4-seat composite airplane with retractable landing gear and a turboprop engine.

Examination of the engine and propeller found no evidence of preimpact mechanical malfunction or failure. The propeller blades exhibited s-bending, torsional twisting, and chordwise scratches, consistent with the engine operating at power during the impact with terrain.

All of the control cable breaks exhibited evidence of tensile overload consistent with separation during the impact. All fuel pumps sustained thermal and impact damage. The on/off cross-feed valve was found in its normal installation area and displayed thermal damage and melting. The valve was found mostly closed and it had seized; however, it displayed a slight angle towards the open position.

The PFD and multi-function display (MFD) were recovered from the wreckage and contained flight data from the accident flight. The accident takeoff was not recorded in the data; however, data was obtained from engine start up through the second taxi for departure. The engine parameters were nominal throughout the ground operations. The left and right fuel quantity indications displayed an imbalance throughout the entire accident flight.

During power-up, the left tank quantity was 85 gallons indicated and the right tank was 39 gallons indicated. Throughout the ground operations, the gallons indicated per each side fluctuated by a few gallons, but the imbalance was observed throughout the entirety of the recorded data. The last indicated fuel quantity recorded, during the second taxi for departure, was 82 gallons in the left tank and 39 gallons in the right tank.

The pilot reported that during preflight inspection he did not notice any abnormalities with the airplane. He did not visually check the fuel levels via the fuel filler caps. He recalled that the PFD fuel indications showed that both wings had 38 gallons. This fuel level was consistent with his recollection that he last landed with less than 45 gallons per tank during a flight about 30 days before the accident.

The pilot reported that in the past the airplane had an issue with fuel migrating from the right tank to the left tank. He recalled that during past preflight inspections he had noticed that the left tank appeared to be nearly topped off when he could not see any fuel when looking into the right tank.

A fixed-based-operator (FBO) employee who towed the airplane from the hangar before the accident noticed that the airplane was leaning a little to the left (left-wing low). He was aware that the airplane had an ongoing issue with fuel migrating from one wing to another when it sat for periods of time in the hangar. He recalled that the left lean that he saw on the day of the accident was not as bad as past instances that he had observed.

Another individual who worked at a business located at the airport had seen jacks placed under the left wing to prevent the airplane from tipping over and to prevent fuel leaking from the left side fuel vents. He saw the airplane in the hangar the day of the accident and it was left-wing low, but the leaning was not as extreme as other instances and no jacks were under the left wing.

The maintenance records were located in the airplane and were destroyed. According to copies of maintenance records, during a condition inspection on April 21, 2022, the left and right fuel pump and fuel filter assemblies were replaced.

According to the pilot, during the summer of 2022, additional work was performed on the fuel system to troubleshoot the fuel migration issue by a mechanic not affiliated with RDD Enterprises, the company who performed the airframe modifications. According to the mechanic who performed this work, he no longer possessed copies of the maintenance endorsements, but he stated that the on/off cross-feed valve was replaced. The valve used was supplied by RDD Enterprises.

According to the POH, the airplane had two 90-gallon fuel tanks incorporated into wet-wing fuel tanks. Fuel balance was designed to be maintained through electronic fuel level sensing that varied the output of each individual fuel boost pump. The fuel system had a pilot selectable on/off cross-feed valve that could allow fuel to move from one tank to the other. The fuel sensors located in the wings provided actual fuel levels to the cockpit displays.

The POH stated that if tanks are not filled to capacity, each tank should be refilled so that each tank quantity is as equal as possible. It further stated that if the fuel imbalance increased beyond 10 gallons that pilot should make a precautionary landing. There was no explicit warning not to depart with a fuel imbalance beyond 10 gallons.

According to RDD Enterprises, there had been reports of fuel migration between tanks while on the ground with the LX7-20 make and model with the original design of the fuel system. According to RDD, the migration issue was resolved when the fuel system was updated in 2021. According to RDD, the accident airplane was equipped with the most recent fuel system design/fuel pumps.

According to RDD, the fuel system design incorporated check valves to prevent the migration of fuel from one wing to another, even in temperature changes as well as sloped parking conditions. However, if a check valve developed a seep or the cross-feed on/off valve was cracked open, it was possible for fuel to migrate from one wing tank to another while the airplane was on the ground.

According to RDD, during the original design and testing of the LX7-20, they determined that for any speed below 100 knots a roll control deficiency would occur at an imbalance of 30 gallons between the left and right tanks. The maximum imbalance of fuel that had been flight tested during takeoff was 10 gallons.

According to the pilot’s operating handbook, the rotation speed (Vr) was 65 knots. The maximum demonstrated crosswind component was 25 knots.

Based upon a review of the windsock captured on the airport’s surveillance video, during the accident takeoff, about a 10-15 knot gusting westerly crosswind (from the right) was present.