N22AUPiper PA-31-310 · 1975

On March 7, 2022, about 1045 eastern standard time, a Cessna 525B, N22AU, was substantially damaged when it was involved in an accident in Middle River, Maryland. The two pilots were not injured. The airplane was operated by Executive Flight Services, LLC, as a Title 14 Code of Federal Regulations Part 135 on demand charter flight.

The pilots reported they flew a stabilized approach to runway 15 at Martin State Airport (MTN), Baltimore, Maryland after the positioning flight from Washington Dulles International Airport (IAD) Washington, District of Columbia. They added 5 knots to their Vref speed to account for the gusting wind.

The pilot reported the landing performance data indicated they would need about 3,000 ft of runway to land, and pilot reported that they landed in the touchdown zone of the 6,997 ft runway. The landing rollout appeared normal until the pilot asked, “Why aren’t the brakes working?” The copilot applied brakes on his side also and was unsuccessful in achieving any braking action. They attempted to locate the emergency brake (located under the instrument panel in front of the pilot’s legs) but were unable to locate it so they applied the parking brake instead. The airplane departed the runway and travelled 450 ft before impacting the airport perimeter fence.

A witness located in the parking lot of the control tower stated that the airplane appeared to be landing very long and that it looked like it touched down near taxiway J, which was located about 3,900 ft past the runway threshold.

Automatic dependent surveillance - broadcast (ADS-B) data, recovered onboard flight data and review of video footage from two airport surveillance cameras were utilized to determine that the airplane touched down about 2,000 ft beyond the approach end of the runway at about 110 knots.

The pilot, an airline transport pilot occupying the left seat, had over 2,780 hours total time with 248 hours in the accident airplane make and model. In May 2021 the pilot completed Part 135 initial/training (Flight Safety Textron Aviation) for the Cessna 525 ground school that included 45.5 hours of ground training and 11 hours of briefing/debriefing hours. The training included, but was not limited to, general systems, pneumatics, hydraulics, flight controls and landing gear and brakes. In addition, the pilot received 14 hours of flight simulator time with an additional 14 hours of pilot monitoring (co-pilot) time. Airplane recurrent Part 135 training was completed in October 2021.

The co-pilot, an airline transport pilot occupying the right seat, had over 7,500 hours total time with 115 hours in the accident airplane make and model. In December 2017 the co-pilot completed Part 135 initial/training (Flight Safety Textron Aviation) for the Cessna 525 ground school that included 48.5 hours of ground training and 10.5 hours of briefing/debriefing hours. The training included, but was not limited to, general systems, pneumatics, hydraulics, flight controls and landing gear and brakes. In addition, the pilot received 14 hours of flight simulator time with an additional 2 hours of pilot monitoring (co-pilot) time. Airplane specific recurrent Part 135 training was completed in May 2018, October 2018, and December 2021.

The Cessna Citation 525B was a medium-size business jet powered by two medium bypass ratio, Williams International FJ44-3A turbofan engines (about 2,800 pounds of flat-rated static thrust at sea level, 22°C, takeoff power) mounted on the aft fuselage. It was not equipped with thrust reversers but had an antiskid braking system designed to maximize braking effectiveness by reducing hydraulic pressure when the wheel speed transducers sense a sudden deceleration on a wheel that skids, without the loss of braking effectiveness, control, or lockup.

The main components of the power brake and antiskid system are the hydraulic pack assembly, accumulator, antiskid control unit, control valve, transducers, fault display and brake metering valve. Other components include the squat switches, which indicate when the airplane is safely settled on the ground, high and low pressure switches, and an emergency brake system that includes a pneumatic storage bottle and emergency brake valve.

The emergency brake system was actuated when the nitrogen pneumatic storage bottle contents were released into the brake system through the emergency brake lever (figure 1). When the lever is pulled, compressed nitrogen is released from the bottle to apply the wheel brakes. Although antiskid protection is unavailable with the emergency brake system, the pilot can modulate the lever to achieve the desired airplane deceleration rate.

Figure 1. Emergency brake (red knob/handle) location

Under the published Pilots Abbreviated Checklist for the Model 525B, Normal Procedures, Decent/Approach/Landing, after application of brakes, the subsequent Caution message read, “IF DURING LANDING A NO BRAKING CONDITION IS ENCOUNTERED, OPERATE THE EMERGENCY BRAKING SYSTEM. MAINTENANCE IS REQUIRED BEFORE THE NEXT FLIGHT.”

Under the Emergency Procedures (Section 2), for Wheel Brake Failure line item #1 states to remove feet from brake pedals and #2 states Emergency Brake Handle……Pull as required. (See Figure 2)

Figure 2. Brake failure procedures

At 1053 EST, the MTN Automated Surface Observing System reported wind from 210° at 12 knots gusting to 21 knots, visibility 10 statute miles or greater, clear skies to 10,000 ft above ground level or greater, temperature of 23° C, dew point 13° C, and altimeter setting of 29.79 inches of mercury. The wind crosswind component as calculated was a crosswind of 10.4 kts and a headwind of 6 kts and gust conditions were calculated to be 18 kts crosswind and 10.5 kts headwind.

The Cessna Citation 525B was a medium-size business jet powered by two medium bypass ratio, Williams International FJ44-3A turbofan engines (about 2,800 pounds of flat-rated static thrust at sea level, 22°C, takeoff power) mounted on the aft fuselage. It was not equipped with thrust reversers but had an antiskid braking system designed to maximize braking effectiveness by reducing hydraulic pressure when the wheel speed transducers sense a sudden deceleration on a wheel that skids, without the loss of braking effectiveness, control, or lockup.

The main components of the power brake and antiskid system are the hydraulic pack assembly, accumulator, antiskid control unit, control valve, transducers, fault display and brake metering valve. Other components include the squat switches, which indicate when the airplane is safely settled on the ground, high and low pressure switches, and an emergency brake system that includes a pneumatic storage bottle and emergency brake valve.

The emergency brake system was actuated when the nitrogen pneumatic storage bottle contents were released into the brake system through the emergency brake lever (figure 1). When the lever is pulled, compressed nitrogen is released from the bottle to apply the wheel brakes. Although antiskid protection is unavailable with the emergency brake system, the pilot can modulate the lever to achieve the desired airplane deceleration rate.

Figure 1. Emergency brake (red knob/handle) location

Under the published Pilots Abbreviated Checklist for the Model 525B, Normal Procedures, Decent/Approach/Landing, after application of brakes, the subsequent Caution message read, “IF DURING LANDING A NO BRAKING CONDITION IS ENCOUNTERED, OPERATE THE EMERGENCY BRAKING SYSTEM. MAINTENANCE IS REQUIRED BEFORE THE NEXT FLIGHT.”

Under the Emergency Procedures (Section 2), for Wheel Brake Failure line item #1 states to remove feet from brake pedals and #2 states Emergency Brake Handle……Pull as required. (See Figure 2)

Figure 2. Brake failure procedures

The airplane departed the runway surface, leaving light skid marks on the last 100 ft of runway before departing the paved runway surface. Three wheel indentation/skid marks continued through the grass for about 450 ft, where the airplane impacted an airport perimeter security fence and came to rest. The resulting impact resulted in substantial damage to the wings and fuselage.

Postaccident examination of the brake system revealed that the pneumatic storage bottle for the emergency brake system and emergency landing gear deployment was removed by the operator after the accident but before the examination on an unknown date and was not observed. It was reported by the operator to be fully charged before it was removed.

A visual inspection of the main landing gear brakes was conducted with no anomalies noted. No evidence of hydraulic leaks was observed near the brakes or any of the associated lines and fittings located in the wheel well. The brake reservoir and brake accumulator were properly serviced. The Valve and Control Unit BIT indicators were observed tripped. The indicators were reset before any testing was accomplished. The parking brake was set and the wear pins on each wheel were examined. The brakes were in a serviceable condition.

The On-ground Mode Antiskid Functional Test was accomplished. The PWR BRK LOW PRESS annunciator illuminated while the accumulator was charged by the airplane pump from a pre-charge state until it reached the normal operating range (green) when the annunciator extinguished. A single pressure gauge was attached at each brake’s highest bleed port and with full pressure applied both brakes performed as designed, holding and maintaining minimum pressure.

The rotary test switch was placed in the ANTISKID position and then quickly placed in the OFF position. The ANTISKID INOP annunciator illuminated for about6 seconds and then extinguished.

Both pilots’ left and right brake pedals were depressed fully and held. With the ANTI-SKID switch in the ON position, the left antiskid speed transducer was turned with a drill and the right brake pressure decreased appropriately, then as the transducer was suddenly stopped, and the left brake pressure decreased before gradually returning to the initial level. The right antiskid speed transducer was turned with a drill and exhibited the same behavior as the left transducer. The behavior of the system was normal with no anomalies observed.

The landing gear tires and treads were down to about 80% of their useful treadwear and had reached the normal removal wear limit.

Postaccident examination and testing of the airplane’s braking system revealed no evidence of any preaccident mechanical malfunctions or failures.

A performance study revealed that main gear touchdown occurred at about 110 knots airspeed and about 104 knots groundspeed about 2,000 ft beyond the approach end of runway 15, within the first third of the landing distance available. However, the airplane aerodynamics and flight-idle thrust models indicated that during the landing ground rollout, configured with ground flaps and speed brakes deployed, the airplane experienced a prolonged period of low equivalent retarding force at the wheel/runway interface. The airplane performance model indicated that, during the ground rollout, the deceleration was primarily due to aerodynamic drag and free rolling (unbraked) wheel friction. The accident airplane did not slow to a safe taxi speed over a pavement rollout distance of about 5,000 ft. The unexpected, prolonged, low equivalent retarding force at the wheel/runway interface during the ground rollout substantially reduced the airplane’s deceleration and prevented the airplane from dissipating sufficient energy to slow to a safe taxi speed or stop prior to the runway departure end. The airplane overran the departure end of runway 15 at a groundspeed of about 58 knots.

According to published airplane performance and landing data, based on the landing weight, dry surface runway conditions, flaps 35 and anti-ice protection either on or off,

the maximum landing distance required was 2,900 ft. (total runway length was 6,997) This calculation was similar to the crew’s report of about 3,000 ft. As configured, the average airplane deceleration was about 1.25 knots per second, significantly less than the expected maximum airplane deceleration capability of 5 to 6 knots per second.

The accident airplane was equipped with a Cessna Aircraft Recording System (AReS) and a Cockpit Voice Recorder (CVR). The AReS data were collected, processed by Textron/Cessna staff, and provided to the National Transportation Safety Board (NTSB) investigation. The CVR data were collected and processed by an NTSB recorder specialist. Both recording device data and reports are in the public docket.