NTSB: Post-Maintenance Stall Test Flown by Crew, Not Test Pilot, Preceded Fatal Hawker Crash

The preliminary investigation into the crash of a business jet in Michigan in October is focusing on the stall characteristics of the aircraft and the crew’s decision to conduct a postmaintenance test flight themselves rather than hiring a test pilot.

The National Transportation Safety Board (NTSB) on Friday released the preliminary report on the crash of the Hawker 800XP (Mexican registration XA-JMR) that went down near Bath Township on October 16, killing all three occupants. They were identified as two pilots and a maintenance representative, all three from Mexico.

According to the NTSB, the airplane, owned and operated by Aerolineas del Centro, arrived at Duncan Aviation, a maintenance facility at Battle Creek Executive Airport at Kellogg Field (KBTL) in March for routine maintenance.

Maintenance personnel spent the next seven months conducting routine inspections of the aircraft, including the removal of the wing leading edges and TKS ice protection panels for a visual inspection for cracks and signs of corrosion.

Per the manufacturer, after the leading edge inspection, a post-maintenance stall test flight is required before the airplane can be returned to service.

According to the NTSB report, the flight crew was the primary crew for the airplane. The crew reported they flew it about 150 hours per year and, according to their logbooks, had completed their most recent training at a commercial simulator training facility in May.

As the maintenance was nearing completion, Duncan Aviation personnel provided the captain of the Hawker with a list of experienced test pilots for hire to perform the post-maintenance stall test flight.

“However, after being unable to coordinate the stall test flight with a test pilot, the flight crew elected to perform the post-maintenance stall test themselves,” the NTSB report said.

The Accident Flight

According to preliminary ADS-B data, the accident airplane departed KBTL at 5:08 p.m. EDT, entered a left climbing turn, and proceeded to an area about 9 miles northeast of the airport. The flight crew contacted air traffic control (ATC) and requested a block altitude from FL 140 to FL 160. ATC approved the request, and the airplane leveled off at FL 150.

At 5:27 p.m. the airplane entered a rapid descent beginning at FL 140. There was an indiscernible transmission from the accident airplane, and ATC responded, “XA-JMR Cleveland.” The flight crew answered, “We are in a…,” followed by a transmission in Spanish, which translated to “in a stall, recovering, sorry.” There were no further transmissions from the flight crew.

Witnesses on the ground reported seeing the aircraft “corkscrewing” as it descended. The airplane came to rest in a wooded area about 9 miles northeast of the airport, impacting the wooded terrain in a relatively flat attitude.

A post-impact fire consumed a large portion of the main wreckage with the exception of a portion of the right wing, both winglets, and the empennage section. All major structures were accounted for at the accident site and retained for further study.

The Hawker was equipped with a cockpit voice recorder (CVR) that was recovered from the accident site and was sent to the NTSB laboratory in Washington, D.C., for analysis.

Aircraft Performance Studied

The NTSB reviewed the pilot’s operating manual (POM) for the Hawker, specifically instructions on operating limitations, system descriptions, flight planning, flight handling, and techniques for the stall test flight.

According to the POM, the stall test should only be done in daytime visual conditions with the “autopilot disengaged, an operative stall identification system, the external surfaces free of ice, the ventral tank empty, and weather radar on standby” and at an altitude over 10,000 feet above ground level, 10,000 feet above clouds, and below 18,000 feet mean sea level.”

The POM also noted that “there is no natural stall warning or aerodynamic buffet prior to the stall. It is acceptable for stick pusher operation to be coincident with the natural stall, provided that any rolling tendency can be restrained to within a 20-degree bank angle by normal use of ailerons.”

A caution advisory stated that a “frequent reason for unacceptable stall characteristics is a tendency to roll the stall. It is acceptable for a moderate roll to occur, provided that normal use of ailerons can limit the roll angle to no more than 20 percent.”

The POM warned that “aileron snatch,” which is the uncommanded tendency of the ailerons to increase deflection, may occur at or prior to stall and is not acceptable and may be strong enough to affect recovery using aileron input. In that case the elevator control must be moved forward to decrease the angle of attack and allow the return of normal aileron control in such an event, so the pilot must be prepared to recover from an unusual attitude.

Chapter 5 of the FAA’s Airplane Flying Handbook states an unusual attitude is commonly referenced as “an unintended or unexpected attitude”—for example, a pitch attitude greater than 25 degrees nose up, nose down greater than 10 degrees, and a bank angle greater than 45 degrees.

Recognition of unusual attitudes and the proper technique for recovery are introduced during student pilot training as part of basic attitude instrument flying and continue to be practiced for proficiency. Pilots are also taught to recognize situations that may result in an unusual attitude, which could potentially lead to a stall or spin.

“Pilots conducting stall checks should have prior experience in performing stalls in the Hawker and must be prepared for unacceptable stall behavior at any point leading up to and throughout the maneuver,” the Hawker POM reads. ““There is no natural stall warning or aerodynamic buffet prior to the stall. It is acceptable for stick pusher operation to be coincident with the natural stall, provided that any rolling tendency can be restrained to within 20-degree bank angle by normal use of ailerons.”

The Michigan accident is the second crash of a Hawker jet during a post-maintenance test flight in two years.

The NTSB is also still working on the investigation into the crash of a Hawker 900XP (N900VA). The preliminary report on that accident indicates N900VA had just come out of maintenance, which included a requirement to remove the wing leading edges and TKS panels to inspect for cracks and signs of corrosion, which necessitated a stall warning and systems check in accordance with the manufacturer’s requirements.

After the inspections were completed on February 6, 2024, the flight crew, made up of a pilot and copilot, planned to fly the airplane from Grand Junction Regional Airport (KGJT) in Colorado to Tacoma Narrows Airport (KTIW) in Gig Harbor, Washington. The preliminary NTSB report shows the aircraft entered a rapid descent and spiraled into terrain near the Colorado-Utah border on February 7, killing both the pilots as the aircraft caught fire on impact.

Both crashes remain under investigation. Traditionally, NTSB investigations take approximately 18 months to a year to conclude.

The complete NTSB preliminary reports for both Hawker accidents can be found below: