Boeing 767 N443AZ accident near San Bernardino, California

Probable cause

The flight crew’s improper derotation which resulted in a hard nose gear touchdown. Contributing to the accident was the captain and first officer’s lack of crew resource management related to communication about pitch control inputs. Contributing to the improper derotation, was the crew’s lack of situational awareness about the control yoke inputs during landing. This resulted in the captain’s restriction of the control yoke aft movement and the first officer losing his grip on the control yoke, which led to an uncontrolled nose down pitch movement and subsequent hard touchdown of the nose landing gear.

NTSB analysis

Air Transport International (ATI) cargo flight 4340 experienced a hard landing at San Bernadino International Airport (SBD), San Bernadino, California. The unscheduled domestic cargo flight was operated under the provisions of Title 14 Code of Federal Regulations Part 121 from Spokane International Airport (GEG), Spokane, Washington. The airplane sustained substantial damage and there were no injuries.

A postaccident examination of the airplane performed by the operator revealed damage to the crown of the upper fuselage. The fuselage skin was buckled and fractured, as shown in figure 1, with damage to the underlying stringers, lap and butt joints.

Figure 1. Fuselage damage on top and right side. (Source: ATI)

The flight crew noted no anomalies with the airplane before or during flight. The first officer was the pilot flying. They performed a comprehensive approach briefing for the ILS to runway 6. They checked the automated terminal information system (ATIS) which indicated no concerning weather, with “excellent” VFR conditions and light winds. The airplane intercepted the localizer about 12 miles out, and they both described the approach as stable.

The first officer disconnected the autopilot between 250 and 200 ft above the ground as planned. As he heard the automated radio altitude callouts for 50 ft and 40ft, he began to reduce the decent rate, and at 10 ft, he retarded the throttles and prepared for touch down. He recalled the touchdown being normal, and then recognized the nose tended to pitch up. He relaxed the control column and applied forward pressure to prevent further pitch up. “At that moment, the controls moved forward abruptly and forcefully”, which caused him to momentarily lose his grip on the controls.

The nosewheel then forcefully contacted the runway. Afterwards, the airplane went back to a steady condition, and he applied left rudder to maintain centerline. At 60 knots, the captain called “my controls” and the first officer transferred the controls to him. The remainder of the rollout and taxi were uneventful.

The captain recalled that the landing flare was initiated at the appropriate time, though (at some time) he noticed “what appeared to be an over-rotation causing the plane to balloon.” Concerned about the “high pitch attitude and trend” [and the potential for a tail strike], he stuck his hand out to block the yoke from coming back further. The airplane then “de-rotated rapidly, landing with a jarring impact.”

A review of the flight data and cockpit voice recorder readouts revealed that the airplane had initially touched down (air/ground indication of “ground” and sound similar to wheels contacting runway) at an airspeed of about 124 knots, flaps 25°, with a pitch attitude of about 5° nose up, and a control column position of about +12° (positive values are aft of neutral). About 1-2 seconds later, the air ground indication momentarily changed to “air” for a single sample (recorded at 1 second intervals) and then back to “ground” where it remained.

Between the two “ground” indications, the control column position reduced to about +6°, and the pitch attitude reduced to about 3°. Just after the second “ground” indication, the control column position increased to about +20° and then immediately reversed and decreased to about -20° (negative values are forward of neutral). The decrease occurred over about 1.5 seconds, and during that time the CVR recorded an utterance from the first officer.

Further, during this aft-then-forward control column sequence, the airspeed initially decreased from about 119 to 113 knots, and the pitch attitude increased from about 3° to about 6°, before it decreased to about 0°. This decrease was the derotation to nose landing gear touchdown. As the pitch attitude reached 0°, a large spike in vertical acceleration was recorded (upwards to about 1.6 Gs, then reversed to about 0.1 Gs), consistent with nose landing gear touchdown.

While the first officer recalled that the controls moved abruptly forward while he was at the same time already moving it forward, the captain recalled putting his hand up to prevent further movement of the control column aft. The investigation was unable to resolve this discrepancy definitively. However, they both recalled that the derotation occurred just after their respective actions (the blocking of aft movement by the captain, and the loss of grip on the yoke of the first officer). That interaction almost certainly occurred during the +20° to -20° control column sequence, because that sequence ended with the derotation. It may have happened just prior to the first officer’s utterance captured by the CVR. See figure 2.

Figure 2. Chart of FDR and CVR data during landing.

The captain’s concern about a possible trail strike was likely due to the airplane’s pitch attitude which increased after touchdown and had ultimately reached about 6° nose up. Geometrically, the tail should strike ground at a pitch attitude of about 8° nose up with the main landing gear compressed (see NTSB accident investigation DCA25LA085). The airplane manufacturer’s flight crew training manual advises that pilots should not allow the pitch attitude to increase, or to hold the nose wheel off the runway after landing, which could lead to a tail strike.

However, there was no verbal communication between the crew recorded on the CVR at the time of the captain’s intervention, or the first officer’s loss of grip on the yoke. According to the crew’s statements, as well as conversations captured by the CVR after landing (between the captain and first officer, as well as of the captain while on a telephone call), the crew did not realize at the time what exactly had occurred.

The first officer didn’t realize that the captain had restricted the aft column motion, and the captain, who was looking at the runway at the time, didn’t see that the first officer’s hands had slipped off the yoke. They discovered this during their after-landing conversations, and concluded that for a period of time, apparently neither one of them were on the controls. The review of the recorded data could not definitively confirm when, or for how long the pilots had their hands off the control yoke.

However, it is likely that it began near or after the time that the control column reached its peak value of about 20° aft (because the captain was trying to limit its aft travel) and likely continued through the nose down control column trend at least until the time the pitch attitude reached 0° and the large vertical acceleration was recorded. The manufacturer’s flight crew training manual also advises not to make large nose-down control column movements, to avoid structural damage.

Derotation is the lowering of the aircraft’s nose gear to the runway following touchdown on the main gear during landing. In a review of National Transportation Safety Board investigations and assisted international investigations, eight similar derotation accidents involving Boeing 757/767 aircraft were found. Those investigations were:

January 16, 1992 - Asiana Airlines in Cheu Island, South Korea

October 27, 1992 – American Airlines flight 957 in São Paulo, Brazil

December 31, 1993 – LOT flight 002 in Warsaw, Poland

July 31, 1997 – Federal Express in Newark, New Jersey

May 22, 2002 – Monarch Airlines in Gibraltar

April 20, 2009 – Royal Air Maroc flight 200 in New York, New York

August 18, 2019 – Delta Air Lines 414 in Ponta Delgada, Portugal

July 29, 2023 – United Airlines 702 in Houston, Texas.

These accidents occurred when the pilots applied large nose-down control column deflections after main landing gear touchdown, which resulted in large nose-down pitch rates and high vertical velocities at the nose gear. It was this combination of vertical velocity and pitch rate that resulted in compression loads that exceeded the design loads of the forward fuselage crown structure.

In 1994, the NTSB made recommendations to the Federal Aviation Administration 1) calling for changes to Boeing 757/767 operating manuals, suggesting they include specific derotation techniques and guidance and 2) modification to initial and recurring Boeing 757/767 training programs to include discussion of derotation accidents. These recommendations were closed in August 1995 as acceptable (NTSB Recommendation Nos. A-94-118 and A-94-119).

Text from the NTSB. Open the NTSB docket for DCA26LA097 for the full record.