Landing (descent or approach)

On December 14, 2004 at 1230 central standard time, an Aero Commander AC-685 twin-engine airplane, Mexican registration XB-GSG, was destroyed upon impact with terrain following a loss of control while maneuvering near Apodaca, State of Nuevo Leon, in the Republic of Mexico. The two commercial pilots and 3 passengers were fatally injured. The airplane, serial number 12058, was registered to a private individual. The flight originated from the Monterrey Del Norte Airport, near Monterrey, State of Nuevo Leon, Mexico, approximately 1225 and was en route to the McAllen-Miller International Airport (MFE), near McAllen, Texas, with Houston, Texas, as its final destination. Visual meteorological conditions prevailed for the business flight for which an instrument flight rules (IFR) flight plan was filed. According to local authorities the airplane was attempting to return to the airport when the accident occurred. The wreckage of the airplane was located on the 350-degree radial from the Monterrey VOR (ADN), for 2.3 nautical miles. A post-impact fire destroyed the aircraft. A post-impact fire consumed the aircraft.

When the crew departed São Paulo-Guarulhos Airport, weather conditions at destination were considered as good. These conditions deteriorated en route and when the crew started the approach to Uberaba Airport by night, the visibility was below IFR minimums. Nevertheless, the crew attempted to land, continued the approach, descended below the MDA by 240 feet when the aircraft struck two houses and crashed in the district of Conjunto Pontal, bursting into flames. The wreckage was found about 800 metres short of runway 17 threshold. Both pilots as well as one people in a house were killed.

Shortly after takeoff, the pilot reported to air traffic control he needed to return to the airport to land. The controller asked the pilot if he required any assistance, and the pilot responded, "negative for right now uh just need to get in as soon as possible." The controller then asked the pilot what the problem was, in which the pilot responded, "stand by one minute." Approximately 30 seconds later and while the airplane was on a left downwind to runway 35R, the pilot stated he was declaring an emergency and "...we've got an air an engine ta shut down uh please roll the equipment." The controller and other witnesses observed the airplane on the base leg and then overshoot the final approach to runway 35R. After observing the airplane overshoot the final approach, the controller then cleared the pilot to the next runway, runway 28, and there was no response from the pilot. The controller observed the airplane's landing lights turn down toward the terrain, and "the MU2 was gone." A witness observed the airplane make an "immediate sharp bank to the left and descend to the ground. The impact appeared to be just less than a 45 degree angle, nose first." A performance study revealed that while the airplane was on downwind, the airplane started to bank to the left. The bank angle indicated a constant left bank angle of about 24 degrees as the airplane turned to base leg. Twenty-three seconds later, the bank angle began to increase further as the airplane turned to final approach, overshooting the runway, while the angle of attack reached stall angle of about 17 degrees. The flight path angle then showed a decrease by 22 to 25 degrees, the calibrated airspeed showed a decrease by 40 to 70 knots, and the vertical speed indicated a 3,000 feet per minute descent rate just before impact. Examination of the airframe revealed the flaps were in the 20 degree position, and the landing gear was retracted. According to the airplane flight manual, during the base leg, the flaps should remain in the 5 degree position and the landing gear extended; and when landing is assured, the flaps then extended to 20 degrees and maintain 125 knots calibrated airspeed (KCAS) during final and 110 KCAS when over the runway. Minimum controllable airspeed (Vmc) for the airplane is 99 KCAS. Examination of the propellers revealed that at the time of impact, the left propeller was in the feathered position and the right propeller was in the normal operating range. Examination of the left engine revealed static witness marks on several internal engine components, and no anomalies were noted that would have precluded normal operation. The reason for the precautionary shutdown of the left engine was not determined. Examination of the right engine revealed rotational scorring and metal spray deposits on several internal engine components. Four vanes of the oil pump transfer tube were separated and missing. The gearbox oil-scavenge pump was not free to rotate and was disassembled. Disassembly of the oil-scavenge pump revealed one separated oil pump transfer tube vane was located in the pump. Pitting and wear damage was noted on all of the roller bearing elements and the outer bearing race of the propeller shaft roller bearing. No additional anomalies were noted.

The 2,100-hour instrument-rated private pilot stated that prior to departure for a 507 nautical mile cross-country flight, the fuel gauges indicated approximately 800 pounds of fuel on each side for a total of 1600 pounds; however, he did not visually check the amount of fuel that the tanks contained. During his approach to the destination airport, the right engine started to "sputter" before it finally quit. The pilot then "looked over at the fuel gauges and both tanks were showing empty." The left engine quit just a few moments later. The auto ignition installed in the airplane attempted to restart the engines. The engines restarted momentarily and then shut-off once more. The pilot declared an emergency and executed a forced landing onto a street below. After a hard landing onto the street, the right wing hit a telephone pole, and the left wing then hit several tree limbs before the airplane impacted a hill and came to a stop. The Federal Aviation Administration (FAA) inspector, who responded to the accident site, found the fuel transfer switch in the "right-crossfeed" position. The fuel system was examined and no leaks or anomalies were found. Approximately three-quarters of a gallon of unusable fuel was found in the right engine nacelle. Approximately four gallons (28 pounds) of usable fuel was found in the left engine nacelle.

The pilot was conducting a cargo flight in night instrument meteorological conditions, and was cleared for the ILS Runway 6L approach. The pilot reported that he was established on the localizer, and the control tower stated that the touchdown and mid-point "RVR" was 1,800 feet, and the roll-out "RVR" was 1,600 feet. The pilot also was instructed, and acknowledged, to make a right turn off the runway, after landing. There were no further communications from the airplane. The airplane's last radar target was observed at an altitude of 1,200 feet msl, and a ground speed of 130 knots. The airplane impacted trees, and came to rest inverted on airport property, on a bearing of 053 degrees, and a distance of 1/2 mile to the runway. Examination of the airplane did not reveal any pre-impact mechanical failures. A weather observation taken at the airport about the time of the accident included, winds from 140 degrees at 9 knots, 1/8 mile visibility, runway 06L visual range variable between 1,800, and 2,000 feet in fog, vertical visibility 100 feet, and a temperature and dew point 54 degrees F. The airport elevation was 1,009 feet msl. Review of the approach diagram for the ILS Runway 6L approach revealed a decision height of 1,198 feet msl, and an approach minimum of 1,800 feet runway visual range (RVR), or 1/2 mile visibility. The pilot had accumulated about 3,800 hours of total flight experience, which included about 350 hours in the same make and model as the accident airplane, and 250 total hours logged in instrument meteorological conditions.

Weather reporting facilities reported icing conditions in the area of the accident site. The pilot of a Cessna Citation flying the same RNAV approach twenty minutes prior to the accident aircraft reported picking up light to occasional moderate rime ice. The last communication between the local air traffic controller and the accident pilot indicated that the flight was two miles south of the final approach fix. The controller inquired if the pilot had the runway in sight, and the pilot reported "negative, still IMC." A witness on the ground near the accident site reported that he heard the aircraft first then saw it at a low level below the cloud base flying in a southeasterly direction. The witness stated that the right wing was lower than the left as the aircraft continued to descend. The witness then noted that the wings were moving "side to side" (up and down) a couple of times before the nose of the aircraft dropped near vertical to the terrain. This witness reported hearing the sound of the engine running steady throughout the event. The wreckage was located in a flat open field about 3,000 feet south of the final approach fix coordinates. The aircraft was destroyed by impact damage and a post crash fire.

The 9,500-hour ATP-rated pilot was forced to secure the left engine during a maintenance test flight following the malfunction of the left propeller. The crew executed single-engine instrument landing system (ILS) approach to runway 13. During short final, the crew noticed that the alternator light was illuminated and the hydraulic pressure gauge indicated "0" pressure. The landing gear was already extended and the flaps were partially extended, so the crew elected to continue the approach to a full-stop landing. Upon landing, the pilot immediately turned on the direct current (DC) hydraulic pump. The pilot added that he then realized that he was unable to maintain directional control of the airplane due to the lack of nose wheel steering and the ineffective wheel brakes. As a result, the airplane continued to veer to the right and exited the runway. The airplane collided with the airport perimeter fence and continued down into a drainage ditch. The examination of the aircraft revealed that the hydraulic pump switch did not appear as if it had been turned on.

The purpose of the flight was to "check out" the airplane before delivering it to its new owner, and to provide the copilot with an indoctrination ride in the Cessna 414. During the approach, the pilot provided guidance and corrections to the copilot. The copilot flew the airplane to within 200 feet of the ground when the nose of the airplane yawed abruptly to the right. The pilot took control of the airplane, and pushed the engine and propeller controls to the full forward position. He placed the fuel pump switches to the "high" position, retracted the flaps, and attempted to retract the landing gear. With full left rudder and full left aileron applied, he could neither maintain directional control nor stop a roll to the right. The airplane struck the ground and continued into the parking area where it struck an airplane and a waste-oil tank. Examination of the airplane following the accident revealed that the landing gear was down and locked, and the propeller on the right engine was not feathered. The emergency procedure for an engine inoperative go-around required landing gear retraction and a feathered propeller on the inoperative engine. The pilot's handbook further stated, "Climb or continued level flight is improbable with the landing gear extended and the propeller windmilling." After the accident, both pilots stated that they didn't notice a power loss on the right engine until the copilot surrendered the flight controls. The right engine was removed and placed in a test cell. The engine started immediately on the first attempt and ran continuously without interruption.

The flight was cleared for the ILS Runway 19 approach, circle-to-land on Runway 24; a 6,013-foot-long, 150-foot wide, asphalt runway. The auto throttle and autopilot were disengaged during the approach, about 800 feet agl. However, the auto throttle reengaged just prior to touchdown, about 35 feet agl. The flightcrew did not recall reengaging the auto throttle, and were not aware of the autothrottle reengagement. According to the auto throttle computers, the reengagement was commanded through one of the Engage/Disengage paddle switches located on each power lever. The target airspeed set for the auto throttle system was 138 knots. After touchdown, as the airplane decelerated below 138 knots, the auto throttle system gradually increased the power levers in an attempt to maintain the target airspeed. Without the power levers in the idle position, the ground spoilers and thrust reversers would not deploy. While the flightcrew was pulling up on the thrust reverser levers, they may not have initially provided enough aft force on the power levers (15 to 32 lbs.) to override and disconnect the auto throttle system. The flight data recorder indicated that the autothrottle system disengaged 16 seconds after the weight-on-wheels switches were activated in ground mode. As the airplane neared the end of the runway, the pilot engaged the emergency brake, and the airplane departed the right side of the runway. The autothrottle Engage/Disengage paddle switches were not equipped with switch guards. Although the autothrottle system provided an audible tone when disengaged, it did not provide a tone when engaged. The reported wind about the time of the accident was from 290 degrees at 16 knots, gusting to 25 knots, with a peak wind from 300 degrees at 32 knots.

While descending to Surakarta-Adisumarmo Airport, the crew was informed about stormy conditions at destination with cumulonimbus and heavy rain falls over the airport with a ceiling at 1,500 feet. The approach was continued and after touchdown on runway 26, the crew started the braking procedure and activated the thrust reverser systems. ON a wet runway, the aircraft was unable to stop within the remaining distance. It overran, lost its undercarriage and slid for few dozen metres, collided with equipments of the localizer antenna, a fence and came to rest in a cemetery. Both pilots and 23 passengers were killed while 70 other occupants were injured. 68 occupants escaped unhurt. The aircraft was destroyed.