Two pilots flying a Learjet from Philadelphia to Teterboro Airport (TEB) near New York City made a series of errors that led to the airplane crashing into a building, killing the crew. No one else was injured in the May 2017 accident.

According to an accident investigation report issued by the National Transportation Safety Board (NTSB), the flight crew exhibited a “lack of situational awareness throughout the flight and approach” to the airport. Neither pilot realized that the airplane’s navigation equipment had not been properly set for the instrument approach clearance they received from air traffic controllers. As a result, the crew improperly lined up for the final approach and the aircraft was hundreds of feet above what was specified by the approach procedure.

Accident aircraft. Source: NTSBThe aircraft stalled and fell onto a building and parking lot around half a nautical mile (nm) from the end of the runway.

NTSB Chairman Robert Sumwalt said that some safety programs used by commercial airline operators are not required for flights like the one that resulted in a fatal crash, including on-demand and commuter flights as well as air medical service, air taxi and charter flights. These are known formally as 14 CFR Part 135 operators, which identifies the part of the federal aviation code that governs their operation.

“If operators of these flights were required to use the same tools as airline operators, accidents like this might not happen,” Sumwalt said.

Accident timeline

According to the accident time, which was included in the NTSB report, on May 15, 2017, at about 1529 eastern daylight time, a Learjet 35A, registration number N452DA, hit the commercial building and parking lot while on final approach to TEB. At the time of the accident, visual weather conditions were in effect, and an instrument flight plan was filed. Gusty winds also were reported, which may have contributed to the airplane’s fatal stall.

(Click to enlarge.) Path of accident aircraft as pilots attempted to line up with the runway. Source: NTSBThe flight left Philadelphia International Airport for TEB at about 1504 and was destined for TEB and the crew filed a flight plan that included an altitude of 27,000 ft and a flight time of 28 minutes. The safety board said that the flight entries were incompatible with each other, which suggests that the crew “devoted little attention to preflight planning.”

The accident report also said that the crew had limited time in flight to plan and brief the landing approach, as required by their company’s policy. They also did not conduct an approach briefing before attempting to land.

Cockpit voice recorder data indicated that the second in command was the pilot flying (PF). This apparently violated a company policy prohibiting the second in command from acting as PF based on his level of experience.

The pilot in command coached the second in command from before takeoff to the flight’s final seconds. The NTSB said that the “extensive coaching” likely distracted the pilot in command from his duties, such as executing checklists and entering approach waypoints into the flight management system.

As the aircraft approached TEB, air traffic controllers vectored the flight for an instrument landing system approach to the airport’s runway 6 to runway 1. When the crew initiated the circle-to-land maneuver to comply with the command, the airplane was 2.8 nm beyond the final approach fix (and about 1 mile from the runway 6 threshold). The plane could not be maneuvered to line up properly with the landing runway.

The NTSB said this situation should have prompted the crew to execute a go-around. However, neither pilot called for a go-around, and the pilot in command (who had taken over control of the airplane) continued the approach by starting a turn to line up with the landing runway.

Radar data indicated that the airplane’s airspeed was below the approach speed required by company standard operating procedures, the NTSB said. During the turn, the airplane stalled and crashed about ½ nm south of the runway 1 threshold.

NTSB recommendations

The NTSB said that the approach speeds listed in the operating company’s procedural manual did not include wind additives to account for gusting wind conditions that were present during the accident flight. The airplane was flown at airspeeds “significantly slower than directed” by standard operating procedures during the approach, it remained above the manufacturer-published stall speed.

Even so, the NTSB said that the strong, gusting wind “might have momentarily” reduced the airplane’s airspeed below the stall speed. The safety board said that adding guidance to Learjet 35A operations manuals to include a wind additive when calculating approach speeds would provide additional stall margin and reduce the risk of a stall.

The NTSB also repeated its recommendation for flight data monitoring programs for Part 135 operators. It said it first issued a safety recommendation for data recording devices and monitoring programs for helicopter emergency medical service operators in 2009. More recently, following a 2015 fatal accident in Akron, Ohio, involving a Part 135 operator, the NTSB recommended that the Federal Aviation Administration require all Part 135 operators to install data recording devices. The NTSB said that the Teterboro accident “further highlights the need for such programs and recording devices” to be required for Part 135 operators.