NTSB Factual Report

HISTORY OF FLIGHT

On February 14, 2011, about 1315 central standard time, a Gulfstream Aerospace Corporation GV-SP airplane, N535GA, had a landing overrun on runway 30 (6,501 feet by 150 feet, dry grooved concrete) at the Outagamie County Regional Airport (ATW), near Appleton, Wisconsin, following a reported loss of a hydraulic system. The two airline transport pilots and one passenger were not injured. The airplane incurred substantial left wing damage when the left main landing gear collapsed during the overrun. The airplane was registered to and operated by Gulfstream Aerospace Corporation under the provisions of 14 Code of Federal Regulations Part 91 as a maintenance test flight. Day, visual flight rules conditions prevailed for the flight, which operated on an activated instrument flight rules flight plan. The local flight departed from ATW about 1010.

The purpose of the flight was a test flight following the installation of the airplane's interior prior to delivery of the airplane to its owner. According to the report submitted by the operator, a preflight brief started at 0815 and some "writeups" were noted. Taxi, engine "run-ups", and takeoff were reported as normal.

The flight to the Marquette, Michigan, area was normal. All inflight checks were found to be normal. However, writeups were noted with the number one flight management system, the elevator trim, and mach trim. The autopilot disengaged during two inflight maneuvers. Following a low approach at the Austin Straubel International Airport, near Green Bay, Wisconsin, the flight crew was cleared direct to SUDIE, an initial approach fix for the area navigation (RNAV)/global positioning system (GPS) runway 30 approach at ATW.

Flaps 10 degrees were selected prior to an intermediate fix named "APESE." Flaps 20 degrees were selected between APESE and the final approach fix (FAF) named "ZUMUG." A discussion about another approach and maintenance issues was conducted and a full stop landing was decided upon to follow the GPS approach. As the airplane approached the virtual glide slope, the pilot flying (PF) called for the landing gear to be selected down and called for the landing checklist to be conducted. The landing gear came down with an indication of three green lights and no red lights. The pilot not flying (PNF) completed the before landing checklist to "include arming ground spoilers, warning inhibit, pumping up Brakes/Hydraulics/Brake Accumulator to 3000 psi" except for "selecting full flaps." Full flaps were to be selected at the PF's call for full flaps. The PNF also selected the Landing Mode on the Cabin Pressure Controller. Subsequent to that, an amber left side hydraulic quantity low crew alerting system (CAS) message illuminated when the airplane was inside the FAF. The PF selected the hydraulic synoptic page and noticed the hydraulic quantity decreasing. The PF called for flaps full and PNF selected flaps full. No movement of the flaps occurred so the PNF re-selected flaps 20 degrees. Shortly after that an amber left hydraulic system fail CAS message appeared.

The PNF pulled out the checklist to accomplish the procedures related to the left hydraulic system fail CAS message and suggested a go-around. At the beginning of the checklist, there is a note that, in part, indicated, "Select a runway that is at least 7,000 feet (2133.6 m) long and 150 feet (45.7 m) wide." According to the operator's report, the PF decided to land due to the significant hydraulic leak and the airplane was in a landing configuration below 1,000 feet above ground level (AGL) with prior autopilot/trim problems. The PNF continued to comply with the left hydraulic fail checklist and turned on the auxiliary (AUX) pump at approximately 500 feet AGL. At the beginning of the checklist, there is a caution statement to verify the availability of the auxiliary system fluid by selecting the AUX pump on for a minimum of 30 seconds to assure that pressure can be maintained. Based on flight data recorder (FDR) data, the left and right contactor transitioning from "Open" to "Closed" 26 seconds prior to all wheels on-ground, consistent with the AUX pump selected on. According to the operator's report, both the PF and PNF indicated that they thought before landing that they had a good auxiliary hydraulic system with normal spoilers, brakes, and nose wheel steering.

The PF had throttles at idle as the airplane touched down on the runway. He indicated that it "felt it took a long time to get the nose down."

According to the operator's report, the PF selected right thrust reverser aft. He began pressing the brakes and felt no braking action. The PF reported that he reached for the emergency brakes, saw the 3,000 feet of runway remaining sign, and decided it would not be enough remaining distance to stop. He attempted to go-around by advancing throttles to the maximum continuous thrust setting.

The PNF felt there was not enough runway remaining to get airborne, saw the airspeed was stable at 100 knots indicated airspeed (KIAS), and did not feel acceleration or see the airspeed start to increase. The PNF pulled the throttles back. The PNF reported that he made this decision to avoid a worst-case scenario of a runway overrun at an even higher speed just as the engines were finally spooling up. The PNF estimated that approximately 1,000 feet of runway remained when the throttles were pulled back. At that time, the PF reached up, deployed right thrust reverser, and began steering airplane to the right to avoid obstacles. The aircraft exited the end of runway 30 at approximately 95 KIAS. The airplane veered right and came to a stop after left main landing gear collapsed.

PERSONNEL INFORMATION

The Pilot Flying

The PF, age 46, seated in the left pilot seat, held an airline transport pilot certificate with a rating for multi-engine land airplanes and commercial pilot privileges for single engine land airplanes. The PF was type rated in Gulfstream Aerospace G-IV, G-V, and Cessna CE-500 airplanes. His most recent Federal Aviation Administration (FAA) first-class airman medical certificate was issued on December 21, 2010, and it listed no limitations. The operator indicated that the PF had accumulated about 6,181 hours of total flight time of which 5,115 hours were as pilot-in-command. The PF had accumulated 555 hours in G-V airplane of which 40 hours were flown in the G-V airplane in the 90 days preceding the accident. The PF had flown about 82, 33, and 3 hours in the last 90 days, 30 days, and 24 hours respectively. The PF's last flight review occurred on January 7, 2011. According to the operator, the PF had military fighter flight experience and had accumulated about 4,500 hours of flight time in the military.

The Pilot Not Flying

The PNF, age 46, seated in the right pilot seat, held an airline transport pilot certificate with a rating for multi-engine land airplanes and commercial pilot privileges for single engine land airplanes. The PNF was type rated in Gulfstream Aerospace G-IV and G-V airplanes. His most recent FAA first-class airman medical certificate was issued on November 9, 2010, and it listed no limitations. The operator indicated that the PNF had accumulated about 4,793 hours of total flight time of which 4,105 hours were as pilot-in-command. The PNF had accumulated 1,176 hours in G-V airplane. The PNF had flown about 90, 32, and 4 hours in the last 90 days, 30 days, and 24 hours respectively, which were all flown in a G-V airplane. The PNF's last flight review occurred on November 19, 2010. According to the operator, the PNF had military fighter flight experience and had accumulated about 3,200 hours of flight time in the military.

AIRCRAFT INFORMATION

The N535GA was a Gulfstream Aerospace Corporation GV-SP airplane with serial number 5305. The FAA issued an amended standard airworthiness certificate for the airplane, on November 9, 2010. The operator reported that at the time of the accident, the airplane had accumulated about 10 hours of total flight time. The airplane had a maximum ramp weight of 91,400 pounds and it was powered by two nacelle mounted Rolls Royce BR700-710C4-11 high bypass ratio turbofan engines rated at 15,385 lbs of takeoff thrust at sea level on a standard day. According to the operator, it typically takes a minimum of eight seconds for the engines to reach full thrust from idle. The engine nacelles feature thrust reversers at the exhaust section to aid in slowing the aircraft during landing. The aircraft landing gear incorporated a steerable nose wheel and main wheel anti-skid braking. The fuselage was of semi-monocoque metal construction.

The main aircraft entrance door was located at the front of the passenger compartment. The cantilevered aircraft wings were swept back 27-degrees and had a 3-degree dihedral. Each wing contained a fuel tank integrated into the wing structure. Primary and secondary flight controls were installed on the wing trailing edge. The primary flight controls were the ailerons, with the left aileron having an adjustable trim tab. Secondary flight controls include the Fowler-type flaps and spoilers. At the wing roots on either side of the fuselage keel were the wheel wells and the main landing gear support structure. The airplane tail section consists of a fixed vertical stabilizer and an adjustable horizontal stabilizer equipped with primary flight controls.

According to the airplane's operating manual, the airplane was equipped with two hydraulic systems, left and right, each powered by an engine driven pump installed on the respective left and right engine that pressurizes fluid contained in dedicated reservoirs. Both systems were independent, each with separate lines and no common point for fluid interchange to preserve the integrity of each system.

Hydraulically powered aircraft components, except the engine thrust reversers, were redundantly protected with an alternate hydraulic power source, dual (left and right) hydraulic actuators, hydraulic accumulator pressure, or compressed nitrogen bottle pressure. Control surfaces used throughout the flight regime were powered using actuators connected to both hydraulic systems, with either system capable of independently powering the controls.

Control surfaces and aircraft sub-systems used in the takeoff and landing phases were powered by a single system, the left hydraulic system. The left hydraulic system was unique in that left system fluid may be pressurized by two sources other than the engine driven pump. Either the electrically driven auxiliary (AUX) pump or a power transfer unit (PTU) driven by the right hydraulic system pressure, which can pressurize left system hydraulic fluid. These two hydraulic pressurization sources offer additional redundancy by using separate quantities of left system hydraulic fluid. The PTU pressurizes normal left system fluid, but the AUX pump uses a dedicated quantity of left system fluid preserved within the left system reservoir in the event of left system fluid loss. If all left and AUX hydraulic fluid was lost, the components essential to landing can be operated using pressure stored in accumulators or nitrogen bottles. The landing gear had pressurized nitrogen as an emergency activation source and the brakes had a hydraulic accumulator as an emergency activation source.

The left hydraulic system supplies fluid drawn from a reservoir and pressurized by an engine-driven pump to all aircraft components and subsystems that require the additional force of hydraulic pressure for normal operation. Since left hydraulic system pressurized some aircraft components and subsystems, two additional means of pressurizing the left system were incorporated to compensate for the loss of the left engine or pump: an electric AUX pump and a PTU driven by right system pressure. The AUX pump was provided with a dedicated volume of hydraulic fluid in the left system reservoir to ensure that AUX pump pressure was available if left system fluid was lost.

The engine-driven hydraulic pump was mounted on the engine accessory gearbox within the nacelle. Engine rotation spins the hydraulic pump so that the pump operates whenever the engine was running. A shutoff valve was installed in the supply line between the reservoir and the pump, powered by the left essential bus, and was controlled by the left engine fire handle. Pulling out the fire handle closes the shutoff valve, preventing hydraulic fluid from entering the engine nacelle.

The left system hydraulic reservoir was located on the left side of the aft equipment bay and the reservoir was divided internally into two compartments, one for left system fluid and the other for AUX pump fluid. The total capacity of the left hydraulic system, including the fluid in system lines was 20.6 gallons, with the reservoir containing five 5.7 gallons, of which 3.7 gallons were available to the left system and 2 gallons reserved for use by the AUX pump.

The left fluid quantity within the reservoir was displayed on a direct reading circular gage, mounted on the side of the reservoir and in the cockpit from data from an electrically powered linear variable differential transducer within the reservoir. The left hydraulic quantity displayed on cockpit synoptic / system windows was the most accurate reading of fluid in the reservoir.

According to the operator, the AUX system quantity display will indicate full when there is any residual fluid in the left hydraulic system and the system will display empty when the left hydraulic system shows empty. There are no intermediate displays for the AUX system.

The electrically powered AUX pump was plumbed into the left hydraulic system and was powered by the left essential DC bus, and can produce a flow of 2 gallons per minute at 3,000 psi. Since the AUX pump was located at some distance from the left system reservoir, a boost pump was installed in the supply line to the AUX pump. The AUX pump can provide hydraulic pressure to operate components essential to configuring the aircraft for approach and landing if no other means of pressurizing the left hydraulic system was available. The AUX pump was also used to pressurize the brake accumulator.

Performance of the hydraulic system components may be monitored on the hydraulics or summary synoptic 2/3 window displays. The hydraulics synoptic display offers the most comprehensive view of the left and right systems. On the summary synoptic window, hydraulic pressures and quantities were shown digitally in colors reflecting system operation - white for normal ranges and amber for abnormal conditions.

The right hydraulic system was operationally similar to the left system, but limited to providing redundant hydraulic power to the flight controls, and single source power to the right engine thrust reverser and the motor drive of the PTU impeller.

According to the operator, during the condition where there was no hydraulic fluid in either the left or AUX system, the ground spoilers would not auto deploy on landing because there would be no hydraulic pressure to initiate the ground spoilers "pop up" signal. Porting of the fluid in the AUX system through a discontinuity in the left hydraulic system can occur when the AUX pump was operated. The failure of both the left and auxiliary hydraulics results in the loss of nose wheel steering, main and AUX brakes, ground spoiler control, left thrust reverser, auxiliary rudder operation and flaps. Emergency brakes are however still available based on pressure remaining in the brake accumulator. Landing gear extension could be accomplished through a compressed gas charge.

METEOROLOGICAL INFORMATION

At 1327, the recorded weather at ATW was: Wind 340 degrees at 10 knots; visibility 10 statute miles; sky condition few clouds 3,500 feet; temperature 2 degrees C; dew point -7 degrees C; altimeter 30.13 inches of mercury.

AIDS TO NAVIGATION

The published inbound course for the RNAV GPS RWY 30 approach at ATW was 298 degrees magnetic. The straight in minimum descent altitude for that approach using localizer performance with vertical guidance approach minima was 1075 feet above mean sea level (MSL), which was listed as 200 feet above the touchdown and using lateral navigation/

NTSB Probable Cause

The pilot flying's (PF) decision to land on a shorter-than-recommended runway with a known left hydraulic system failure rather than go around as suggested by the pilot-not-flying, his failure to immediately apply emergency brakes following the detection of the lack of normal brakes, and his attempt to go around late in the landing roll with insufficient runway remaining. Contributing to the accident was the nose landing gear swivel assembly failure, the lack of a hydraulic fuse before this critical failure point, and the design of the swivel using two similar alloys with a propensity to adhere to each other when rubbed together. Also contributing to the accident was the lack of a disciplined cockpit environment.