NTSB Factual Report

HISTORY OF FLIGHT

On November 8, 2005, about 0725 eastern standard time, an Embraer 110P1, N7801Q, operated by Business Air, Incorporated as AirNow flight 352, was destroyed when it impacted a department store garden center shortly after takeoff from Manchester Airport (MHT), Manchester, New Hampshire. The certificated airline transport pilot was seriously injured. Visual meteorological conditions prevailed, and an instrument flight rules flight plan had been filed for the flight to Bangor International Airport (BGR), Bangor, Maine. The unscheduled cargo flight was being conducted under the provisions of 14 Code of Federal Regulations Part 135.

According to the pilot, the preflight inspection, start-up, taxi and takeoff from runway 6 with flaps set at 25 percent were all normal. However, just after raising the landing gear, the pilot heard an explosion from what he thought was the right engine. But when he checked the engine instruments, he saw that all of the gauges for the left engine indicated zero. The pilot then visually checked the left engine and saw that the left propeller had completely stopped. The pilot retarded the left power lever, but never had time to shut off the condition lever.

The pilot added full power to the right engine, left the flaps at 25 percent, and left the landing gear up. The airplane began a "shallow" left turn, and although the pilot "stood on the right rudder," he could not stop a left turning descent. (When interviewed, the pilot could not recall the position of the yoke.) The pilot advised the tower of the emergency, requested a landing back at the airport, and was issued a clearance to land on runway 17. However, before the pilot could fly the airplane back to the airport, it descended into the garden center. The pilot also noted that after the loss of engine power, he "couldn't hold V speeds" and "the stall warning horn was going off the whole time." When asked about the airplane’s maximum altitude, he "guess[ed] around a thousand feet."

In the garden center, the airplane struck several tractor trailer-sized metal storage containers. The cockpit separated from the rest of the fuselage, slid through the back fence and out of the garden center, and came to a stop on its right side. The pilot undid his harness, fell down to the right side, and crawled out the back opening, where bystanders helped move him away from the wreckage.

AIRPLANE INFORMATION

The airplane was a 1979 Embraer (EMB) 110P1 Bandeirante, powered by two Pratt and Whitney Canada (P&WC) PT6A-34 engines. The airplane had been converted from a passenger configuration to a cargo carrier and was carrying small packages at the time of the accident.

Business Air EMB110P1s were modified, in part, via Supplemental Type Certificate (STC) SA01184AT, which involved the removal of passenger windows and overwing exits, and the modification of airstair doors. Listed under "Limitations and Conditions," was: “Airplanes modified with this STC must be maintained with an Approved Aircraft Inspection Program [AAIP] for FAR Part 135.”

Per FAA Advisory Circular (AC) 135-10A, AAIP pertains to "aircraft of nine or less passenger seats operated under FAR Part 135."

According to FAA Type Certificate Data Sheet No A21SO, for the EMB-110P1, Note 9, "Cargo version must be maintained in accordance with the original certification requirements of a 10 or more passenger aircraft."

A review of maintenance records revealed that the airplane's left engine was overhauled in October 1998. At that time, the "power section was completely dismantled for full overhaul inspection in accordance with the overhaul requirements." The 1st stage planet gear assembly was replaced due to "frosted and pitted gear teeth." The sun gear was found to be serviceable, and was reinstalled along with a new planet gear assembly.

On September 2, 1999, P&WC issued Service Information Letter (SIL) PT6A-079 to advise all operators of an overhaul manual change that addressed first stage sun gear and planet gear reliability. According to the Letter, experience indicated "an increasing rate of unplanned removals due to first stage sun/planet gear distress following an overhaul where only the first stage sun gear or planet gears and not both were replaced." In the majority of distress cases, the first stage sun or planet gears had been matched with replacement "zero time" sun or planet gears. The Letter further stated that each engine model's corresponding overhaul manual would be changed to require the replacement of the sun and planet gears as a set should one of them be found unserviceable. In May 2000, the engine overhaul manual was updated.

Time since overhaul of the left engine power section was calculated to be 4,161 hours.

Automatic Feathering

The airplane was equipped with an automatic feathering system. According to the Airplane Flight Manual (AFM), if armed, and should the engine torque drop below 200, plus or minus 50 foot-pounds, an automatic feathering solenoid would be energized and the propeller would feather.

"Autofeather - Set" was part of the Before Takeoff Checklist.

Trim Controls

There were trim controls in the Bandeirante for all three flight axes, located on the center pedestal. The elevator trim was located on the left side of the pedestal, and consisted of a wheel that rotated in a fore and aft plane. Next to the elevator trim was the rudder trim, which consisted of a palm-sized wheel that rotated left and right. Below and aft of the rudder trim was aileron trim, which also consisted of a palm-sized wheel that rotated left and right.

Takeoff Weight

The takeoff weight of the airplane for the accident flight was calculated to be 11,554 pounds. The maximum gross weight of the airplane was 12,500 pounds.

Single Engine Airspeeds

The single engine best angle of climb airspeed (Vxse) at 11,500 pounds was calculated to be 104 knots. The single engine best rate of climb airspeed (Vyse) at 11,500 pounds was calculated to be 110 knots.

Stall Warning Horn

According to the AFM, the stall warning horn would have been energized between 5 and 10 knots above stalling speed. Indicated stall speed at 11,500 pounds with the landing gear up and flaps 25 percent was 83 knots at 0 degrees angle of bank, and 90 knots at 30 degrees angle of bank.

Takeoff Flap Setting

Avior Corporation, Incorporated, an affiliate company of Business Air and based at the same location, converted Embraer passenger airplanes into cargo airplanes via a series of FAA-approved STCs. One of the STCs, for single pilot operations, required the issuance of a Flight Manual Supplement. Supplement Limitations included: "Takeoff and Landing data, and checklist placards are required." One of the required placards included V speeds at various weights, and at the bottom stated, "Note: Vr at all weights, flaps 25 percent = 85 knots." The Supplement was approved by the Boston Aircraft Certification Office in January 2001.

Landing Gear Warning System

According to the AFM, "If at least one of the power levers is brought below an Ng range between 75 and 78 percent, while one landing gear strut is not in its downlocked position, this will be enough to make the system blow the horn and illuminate a red light on the annunciator panel (LANDING GEAR)."

Engine Chip Detectors

As originally certificated on the Bandeirante, the engines were equipped with chip detectors; however, per original type design, they were not connected to any cockpit warning systems.

PILOT INFORMATION

The pilot held an airline transport pilot certificate with a multi-engine rating and an EMB-110 rating. According to the pilot, he had previously flown Part 135 operations in Texas and Michigan, and had been part owner of a Piper Navajo operation in North Carolina prior to his employment with Business Air. He had been with the company about 5 months.

According to company records, the pilot had logged 3,612 total flight hours, with 137 hours in the EMB-110, and had flown his captain's check ride in July 2005.

The pilot's latest FAA first class medical certificate was issued on April 4, 2005.

Before the accident, the pilot had been scheduled to take assistant chief pilot training at company headquarters, to assume that position for the company's Cessna 208 operations in its southern region.

On one of his prior training flights, on July 23, 2005, the pilot performed a practice emergency descent. According to the instructor’s comments: “Recovery needs work – loss of airspeed. More aggressive on nose down att[itude].”

RADAR AND VIDEO INFORMATION

Due to the terrain, no radar track information was available. In addition, a check of local businesses and airport facilities revealed that no security cameras or ATM machine cameras were pointed at the airplane during the accident sequence.

According to a supervisor at Boston Approach Control, Manchester Sector, the radar computer system might be able to process a primary "skin paint" about 500 feet, but an altitude readout would not be present until 900 to 1,000 feet.

METEOROLOGICAL INFORMATION

Weather, reported at the airport at 0653, included calm winds, visibility 10 statute miles, broken clouds at 11,000 feet, temperature 7 degrees Celsius (C), and dew point -1 degree C.

Weather, reported at the airport at 0753, included winds from 270 degrees true at 5 knots, 10 statute miles visibility, scattered clouds at 8,000 feet, temperature 10 degrees C, and dew point -1 degree C.

WRECKAGE AND IMPACT INFORMATION

The accident site was located about 6/10 nautical mile, 010 degrees magnetic from the departure end of runway 6, in the vicinity of 42 degrees, 56.9 minutes north latitude, 71 degrees, 26.4 minutes west longitude.

The wreckage path, which was oriented toward 190 degrees magnetic, began at the top of a parking lot light stanchion, about 60 feet from the garden center. Damage continued along the garden center roof and included two more light stanchions. Past the roof, there were impact marks on numerous 40-foot, tractor trailer-sized metal storage containers that lined both sides of a pathway that led to a chain link security fence. The initial width of the pathway was estimated to be about 30 feet. The containers on the left side of the pathway were aligned along the department store wall, while the line of storage containers on the right side of the pathway angled away from the wall by an estimated 30 degrees.

An indentation, consistent with the position of the airplane's left wing, was found in the first container on the left side of the wreckage path. There were also scrape marks on the top of the container.

The left wing, including the left engine, was found fractured in sections, along the containers on the right side of the wreckage path. Further along, next to the containers on the left side of the pathway, was a turned-over and charred forklift. Next to the forklift were the charred remains of the right engine. Just beyond the forklift was a destroyed section of the chain-link security fence, containing the burnt remains of the airplane's right wing and center wing/fuselage section. Next to those were the mostly-charred remnants of the airplane's empennage.

About 60 feet beyond the empennage, was the airplane's unburned cockpit area, laying on its right side.

The left engine propeller hub was still attached to its engine. The propeller blades appeared to be angled about 90 degrees from the direction of rotation, and there was no significant leading edge damage to the propeller blades, consistent with the propeller having been feathered.

The right engine propeller hub was detached from the engine, and one propeller blade was separated about 8 inches from the tip, while the other blades exhibited curling, missing blade material and leading edge damage. The blades also appeared to be angled 90 degrees from the direction of rotation.

Control surface actuator positions were measured on the accident airplane, then correlated to a similar airplane at company headquarters. The resultant trim positions observed were: flaps were at 25 percent, the rudder at neutral trim, and aileron was at full left trim. However, the airplane's break-up sequence could have altered the in-flight trim positions.

TESTS AND RESEARCH

Climb Performance

Embraer engineers calculated the airplane's rate of climb performance based on 25 percent flaps, a takeoff weight of 11,550 pounds for the accident airplane, and the ambient conditions at the time of the accident. With an inoperative and feathered engine, the airplane should have been able to climb at 445 feet per minute.

Engine Out Performance

According to the STC placard mounted in the airplane, Vxse for 11,500 pounds was 104 knots, and Vyse was 110 knots. Utilizing the Bandeirante AFM Stall Speed Chart, and a "shallow" (15 degrees) angle of bank, landing gear up, flaps 25 percent, the stall speed for the airplane, if trimmed, would have been about 87 knots.

Engine Examinations

The two engines were examined in Montreal, at P&WC facilities, on December 6 and 7, 2005, with Safety Board oversight.

The right engine compressor turbine shroud exhibited rubbing marks. There was heavy rubbing/scoring damage on the compressor turbine disk rear face and turbine blade trailing edges. The power turbine shroud exhibited heavy circular scoring, and the power turbine had severe rubbing/scoring on the disk upstream face. All power turbine blades were fractured.

The left engine compressor turbine shroud exhibited some light material deposits adhering to the surfaces, and the compressor turbine blades exhibited tip burning with partial breakage. The power turbine shroud was heavily gouged and punctured. The power turbine disk was found angled approximately 45 degrees from its normal operating plane. There was also evidence of impact damage, but no evidence of rotational scoring.

An examination of the reduction gearing from the left engine revealed that the sun gear was fractured at three locations: one within the teeth and two along the shaft. The sun gear teeth were completely worn off about 1/4 the width of the gear. The remaining portions of teeth were also partially worn off, approximately 180 degrees around the gear. There was also heavy gear tooth damage to the 1st stage planet gears, with many of the teeth fractured.

The planet gears and sun gear were further examined at the P&WC Materials Laboratory. According to the Laboratory Report, the planet gears exhibited severe battering and multiple tooth fractures, and the sun gear was fractured radially within the teeth.

The sun gear fracture exhibited fatigue cracking in the root of the filet radius. A fractured tooth almost diametrically opposite of the radial fracture also exhibited fatigue in the filet radius on drive side of the tooth.

The planet gears exhibited numerous fractured teeth, which displayed features indicative of fatigue originating at the root filet radius on the drive side. The remaining battering was considered secondary.

Under high magnification, the fracture surfaces on the sun gear and one of the planet gears revealed the presence of fine striations, consistent with high cycle fatigue.

Chemical composition and hardness, as well as the depth of the finished case of the sun gear and one examined planet gear met the drawing requirements.

Debris found on the engine chip detector was identified as an iron-based alloy similar to reduction gear material, aluminum alloy similar to air seal material, and magnesium alloy similar to reduction gearbox housing material.

MAINTENANCE INFORMATION

Maintenance Reliability

FAA Advisory Circular (AC) 120-17A, “Maintenance Control by Reliability Methods,” initiated by Flight Standards Service (AFS)-230, provides “information and guidance material which may be used to design or develop maintenance control programs utilizing reliability control methods.”

The AC, which was issued in 1978, addresses approved aircraft maintenance programs to those operators subject to the provisions of Federal Air Regulations Parts 121 and 127. However, even though it wasn’t directed toward Part 135 operations, the AC never

NTSB Probable Cause

The pilot’s misapplication of flight controls following an engine failure. Contributing to the accident was the failure of the sun gear, which resulted in the loss of engine power. Contributing to the sun gear failure were the engine manufacturer’s grandfathering of previously recommended, but less reliable, maintenance standards, the Federal Aviation Administration’s (FAA) acceptance of the engine manufacturer’s grandfathering, the operator’s inadequate maintenance practices, and the FAA’s inadequate oversight of the operator.