NTSB Factual Report

HISTORY OF FLIGHT

On December 22, 2011, at 1725 eastern standard time (EST), a Cessna 441, N48BS, was substantially damaged when it impacted terrain near Nashville, Pennsylvania, while approaching York Airport (THV), Thomasville, Pennsylvania. The commercial pilot was fatally injured. Night visual meteorological conditions prevailed. The airplane had been operating on an instrument flight rules (IFR) flight plan from Long Beach Airport - Daugherty Field (LGB), Long Beach, California, to THV; however, the pilot had cancelled the flight plan and was proceeding visually via the airport traffic pattern at the time of the accident. The personal flight was operating under the provisions of 14 Code of Federal Regulations Part 91.

According to the pilot's wife, he was joining the rest of the immediate family, who had previously arrived via a commercial flight for the Christmas holidays with relatives.

Air traffic control information indicated that the airplane departed LGB about 1105 (0805 Pacific standard time) and climbed to 33,000 feet. About 1522, it climbed to 35,000 feet, and about 1639, it began a descent. At 1707, the pilot cancelled the IFR flight plan with New York Center, and at 1716, he terminated flight following with Harrisburg Approach Control.

Radar data indicated that at 1719, the airplane was about 24 miles west of THV at 1,700 feet. The airplane continued eastbound, and entered a 45-degree left downwind for runway 35. The airplane subsequently turned onto a left base, then slightly overshot runway centerline before commencing a right turn and disappearing from radar.

An airport employee stated that the pilot radioed for airport advisories, and about 4 or 5 minutes later, he saw the airplane on the [left] base leg for runway 35. When the airplane was about midway through the base leg, the pilot transmitted that he had an "engine out." The airplane did not then turn onto the final approach leg, but continued through it, heading east. The pilot then called "base to final," quickly followed by the airplane turning [right], to the south, then to the west. The employee saw the angle of bank increase to where the airplane's wings were vertical, then inverted, and saw the airplane then make at least 1 ½ "rolls" and descend in a near-vertical descent.

Another witness saw the airplane flying "awfully slow," and subsequently saw it turn to the left. The airplane then nosed over and began to dive and spin, "snap rolling nose down, tail up." The witness also noted that although the sky was dark, it was not yet pitch black.

Measurements of plotted radar positions versus time indicated an approximate ground speed of 112 knots during the downwind leg, slowing to 102 knots at the beginning of the left base leg. During the subsequent right turn, the ground speed slowed to about 75 knots while the airplane maintained altitudes of 1,100 to 1,200 feet.

The airplane was equipped with an Enhanced Ground Proximity Warning System (EGPWS), which, according to the NTSB Specialist's Factual Report, records data on non-volatile memory for the 20 seconds prior to a warning and 10 seconds afterwards.

The report also noted that the event which most likely triggered the EGPWS recording was an "Excessive Rate of Descent Warning." Consistent data prior to the airplane's rapid descent included an uncorrected altitude of about 1,100 feet as the airplane was turning to the right, and a ground speed of about 78 knots through the beginning of the airplane's final descent.

PILOT INFORMATION

The pilot, age 38, held a commercial pilot certificate with ratings for airplane single engine land and multiengine land airplane, and instrument airplane. According to the last entry in the pilot's logbook, appearing to have been written during the accident flight, the pilot had flown 1,409 total hours with 951 hours of that being in multi-engine airplanes and 463 "turbine" hours. Between the pilot's latest insurance application and his logbook, it was estimated that he had flown 502 hours in airplane make and model.

The pilot had last completed a flight review on January 28, 2011 in a "Cessna Conquest II." His latest FAA third class medical certificate was dated November 7, 2011.

The pilot had a communication device capable of voice calls, texting, email and alarms, among other functions. Emails were sent by the device until 0323 (EST), and an alarm sounded at 0920.

AIRPLANE INFORMATION

The airplane was powered by two Honeywell (Garrett/AiResearch) TPE331-10N-535S turboprop single fixed shaft engines, flat-rated at 635 shaft horsepower each.

Each engine powered a four-bladed, hydraulically operated constant speed Hartzell propeller with feathering and reverse pitch capability.

According to the aircraft logbooks, the latest Phase 2 maintenance inspection was completed on July 1, 2011, at 5,890 airplane hours, and 514 hours since major overhaul of both engines. The hour meter indicated 2,874 hours at the time.

- Systems and Controls -

According to the airplane's Pilot's Operating Handbook (POH):

Minimum control speed (Vmca)

- "Vmca is the minimum flight speed at which the airplane is directionally and laterally controllable…in accordance with Federal Aviation Regulations. Airplane certification conditions include one engine becoming inoperative; not more than 5-degree bank toward the operative engine; takeoff power on [the] operative engine; landing gear up; flaps in takeoff position; and most critical center-of-gravity."

- The POH also noted that Vmca was 91 knots indicated airspeed (KIAS).

- The POH also included an FAA-approved Flight Manual Supplement for the installation of a "441 Vortex Generator Kit;" however, Vmca remained at 91 KIAS.

- The Supplement further noted that 76 KIAS was the maximum-weight stalling airspeed in the landing configuration.

Wing Flap System

- The POH stated that the hydraulically controlled flap actuator was controlled by the wing flap position switch which incorporated a select amount of wing flaps desired. "With the wing flaps set at UP, T.O., APPR or LAND positions, the corresponding inboard wing flap extensions are 0 degrees, 10 degrees, 20 degrees and 30 degrees.

- The outboard wing flaps were mechanically linked to the inboard sections, extending at a slower rate. When the inboard wing flaps were fully extended (30 degrees), the outboard wing flaps were extended 20 degrees.

Power Levers

Per the POH, '"The power lever controls engine operation in the beta and propeller governing modes. Beta mode is used during ground operation only. In beta mode, the propeller blade angles are controlled hydraulically by the power levers. In propeller governing mode, the power lever controls fuel flow, either electrically in normal mode operation or hydromechanically in manual mode operation, and the propeller blade angles are governor controlled to maintain proper engine speed.

Prior to landing in normal (computer) mode engine operation, with the condition levers in TAKEOFF, CLIMB AND LANDING and the power lever at flight idle, engine fuel flow assumes a scheduled value to obtain predictable drag during landing. In manual mode, the flight idle position will provide significantly more drag due to the lower fixed fuel flow scheduling."

The POH also discussed the "Electronic Fuel Computers" (EFCs), also known as electronic engine controls (EECs) by the engine manufacturer. The POH noted that there was one EFC for each engine and that each EFC regulated fuel flow and engine speed through output signals to the fuel control unit and the propeller governor. The POH further noted that the EFC had a self monitoring feature that automatically transferred control from "normal" to "manual" in the case of loss of power lever electrical input, low voltage, and disagreement within the computer between the power requested and the output to the fuel control. The protection was restricted to specific operating ranges of the power lever and condition lever.

Negative Torque Sensing (NTS) System

Per the POH, the NTS system operated automatically, with no controls for the pilot.

"Negative torque occurs when the propeller drives the engine rather than the engine driving the propeller. When negative torque does occur, the propeller pitch will automatically increase toward the feather position to a level that will reduce the drag of the windmilling propeller. Negative torque can occur during any normal operation when the fuel flow schedule is excessively low and will not support the engine power requirements to maintain positive torque. Negative torque sensing will always occur during an engine failure before the propeller is feathered, and during low altitude normal mode operation at flight idle."

The Garrett TPE331-8/-9 Maintenance Manual further noted that, "the NTS system effects a movement of the propeller blades automatically toward their feathered position (should the engine suddenly lose power while in flight) and precisely modulates the propeller- blade pitch angle during a propeller-windmilled engine air-start."

Propeller and Control

Per the POH, each propeller was hydraulically actuated, constant speed and full-feathering.

"The propeller governing system is interconnected with the NTS system (and the fuel control system electrically in normal mode.) Engine oil pressure, feathering springs and propeller blade counterweights are used to set the propeller blade angles. Engine oil pressure is increased by the propeller governor and transferred to the propeller hub through a beta tube. The propeller counterweights and feathering spring attempt to move the propeller blades to full feather while the oil pressure attempts to move the propeller blades to reverse pitch. Propeller blade angle can thus be set as desired by use of the power and condition levers, which control the amount of oil pressure exerted in the propeller hub.

Feathering the propeller is achieved by dumping oil pressure in the propeller hub assembly. This can be accomplished by stopping the engine-driven oil pump (engine shutdown) or by positioning the condition lever to EMERG SHUTOFF. The EMERG SHUTOFF position of the condition lever will actuate the manual fuel shutoff valve to shut down the engine and then dump the propeller oil pressure to feather the propeller."

Fuel Control

Per the POH, the fuel control system provided filtered and metered fuel to the engine.

"The fuel control system is regulated by the electronic fuel control for 'normal mode' operation, and by a manual backup system for manual mode operation.

When operating in manual mode, the pilot directly controls the engine fuel schedule with the power lever, which is mechanically connected to the propeller pitch control and hydro mechanical unit. When operating in manual mode, some of the refinements of normal mode are not available."

- Normal Procedures: Before Landing -

13. Wing Flaps – LAND below 180 knots.

14. Approach Speed – 99 KIAS at 9360 pounds.

- Emergency Procedures (Amplified Procedures) -

Engine Failure in Flight (Speed Below Vmca)

(Memory Items)

1. Power Lever – RETARD as required to stop turn.

2. Aileron and Rudder – AS REQUIRED toward operative engine to maintain straight-ahead flight.

3. Pitch Attitude – LOWER NOSE to accelerate above 91 knots.

(Non-Memory Item)

4. Accomplish procedures for Engine Failure During Flight (Speed Above Vmca)

Engine Failure During Flight (Speed Above Vmca)

(Memory Items)

1. Engine Power – ADJUST as required.

2. Inoperative Engine – DETERMINE. Idle engine same side as idle foot; also, torque and EGT will be low.

a. Condition Lever – EMER SHUT-OFF.

b. Firewall Shutoff – PUSH to close.

3. Landing Gear – UP.

4. Wing Flaps – UP above 115 KIAS.

METEOROLOGICAL INFORMATION

Weather, recorded at 1753, included calm wind, clear skies, visibility 10 statute miles, temperature 7 degrees C, dew point 4 degrees C, and altimeter 30.02 inches Hg.

According to U.S. Naval Observatory data, sunset occurred at 1645 and the end of civil twilight occurred at 1716. There was no moon illumination at the time of the accident.

WRECKAGE AND IMPACT INFORMATION

The wreckage was located on open, rolling terrain, about 145 degrees magnetic, 1.56 statute miles from THV runway 35, in the vicinity of 39 degrees, 53.53 minutes north latitude, 076 degrees, 51.11 minutes west longitude. There was no wreckage path, and ground indentations matching the positions of the extended landing gear, and the nose and tail of the airplane were consistent with an almost vertical descent, and an initial ground impact heading of about 060 degrees magnetic. There were then no ground marks, consistent with the airplane having bounced once, then coming to rest heading about 090 degrees magnetic.

The airplane's tail section was broken off to the left, and the left wing outboard of the left engine was broken forward. The aft portion of the right wing root was pushed into the fuselage, and the landing gear were fractured upwards. The overall damage noted was consistent with an airplane having been in a right-turning flat spin when it initially impacted the ground.

There was no evidence of either an in-flight or post-flight smoke or fire.

Flight control continuity was confirmed from all flight control surfaces to the front of the damaged cabin area, where there was cable impingement. The flap handle was in approach, and the flap actuator position equated with the flaps being extended approximately 30 degrees.

The left engine throttle was near flight idle, and the right engine throttle was full forward; however, the effects of ground impact on their positions could not be determined. Both condition levers were in the EMERG SHUT-OFF position, but according to a witness, they were pulled to that position after initial responders smelled fuel. The responder who shut off the condition levers stated that he did not touch the throttles.

About 4 gallons of fuel were drained from the right fuel tank; however, the tank and the fuel hopper were breached. There was also an odor of fuel in the soil beneath the wing. Fuel quantity from the left fuel tank could not be determined due to the extent of damage to the tank and to the wing. When the wing was lifted, fuel flowed from a breach near the wingtip.

The right propeller did not exhibit any outward signs of significant power at impact. Two of the four propeller blades exhibited no damage while the other two had some bending, but no significant chordwise scratching. The right propeller did not appear to have been in feather at impact; however, by the following day, the blades had moved toward the feather position.

The left propeller exhibited significant damage. Two of the four propeller blades were broken off at the hub, while the third blade was dangling loose in the hub and the fourth blade was bent in a direction opposite normal rotation.

The hour meter indicated 2,955 hours.

Both engines, both propellers, and several other items were retained for further examination:

- Engines -

The engines were disassembled and examined at the manufacturer's facility under NTSB oversight. The extent of damage to the engines precluded any attempt to run them.

- The right engine exhibited some impact damage, but no debris ingestion. No preexisting mechanical anomalies were noted that would have prevented normal operation. In addition:

Fuel was found within the engine fuel pump filter housing; however, with fractured fuel lines and couplings, fuel was missing from within some of the lines.

There were static witness marks on the first stage compressor impeller shroud between the 9 and 12 o'clock positions aft, looking forward (ALF). There were also rub/chatter marks between the 3 and 6 o'clock positions that corresponded to slight leading edge scoring on four vanes of the first stage compressor impeller.

The first stage also revealed about 45 degrees of rotational scoring on the aft hub with corresponding scoring on the inner diameter of the crossover duct housing seal area.

The second stage compressor housing exhibited 90 degrees of rub with correspondin

NTSB Probable Cause

The pilot's failure to maintain minimum control airspeed after a loss of power to the right engine, which resulted in an uncontrollable roll into an inadvertent stall/spin. Contributing to the accident was the failure of the airplane's right engine for reasons that could not be determined because no preexisting mechanical anomalies were found, and the pilot's subsequent turn toward that inoperative engine while maintaining altitude.