N4488B

HISTORY OF FLIGHT

On April 23, 2006, about 1158 Alaska daylight time, a wheel-equipped Cessna 170B airplane, N4488B, and a wheel-equipped Cessna 172 airplane, N5049A, collided in midair, approximately 7 miles north-northwest of Chugiak, Alaska. Both airplanes were being operated as visual flight rules (VFR) personal flights under Title 14, CFR Part 91, in visual meteorological conditions when the accident occurred. The certificated airline transport pilot, and the three passengers aboard the Cessna 170B, sustained fatal injuries. The sole occupant of the Cessna 172, a certificated commercial pilot, also sustained fatal injures. Both airplanes were destroyed during the collision, uncontrolled descent, and impact with tidal mud flats. Both airplanes were based at the Birchwood Airport, Chugiak. The Cessna 170B departed from the Birchwood Airport about 1153, and a VFR flight plan was filed for the flight to Talkeetna, Alaska. The Cessna 172 departed from the Birchwood Airport at an unknown time, for a local area flight.

During on-scene interviews with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on April 23, witnesses reported that they observed the Cessna 170B traveling north-northwest, between 1,500 and 2,000 feet msl, and a Cessna 172 traveling in a southwesterly direction. About 30 seconds later, the witnesses described hearing a "loud explosion" which directed their attention almost directly overhead. The witnesses reported seeing both airplanes entwined, descending vertically. As their descent continued, they separated, and struck the tidal mud flats in a nose low attitude. The witnesses said that as the Cessna 170B continued its vertical descent the left wing separated, and the airplane rotated counter-clockwise in a descending spiral.

During a telephone conversation with the NTSB IIC on April 25, a pilot-rated witness who saw both airplanes just before, during, and after the collision, said that he witnessed the accident from his driveway, located about a half-mile north of the accident site. He said that as he watched the Cessna 170B fly north-northwest, at an estimated altitude of 2,000 feet msl, he observed the Cessna 172 traveling in an west-southwesterly direction, approaching the Cessna 170B's right side. He said that as the airplane's flight tracks converged, and just before impact, he heard the Cessna 172's engine noise increase significantly, followed by a sharp nose-up maneuver. The witness stated that the north-northwest bound Cessna 170B subsequently collided with the west-southwest bound Cessna 172's left side of the fuselage, resulting in the subsequent breakup of both airplanes.

According to a family friend, the pilot of the Cessna 170B was en route to a Civil Air Patrol social gathering in Talkeetna, along with three of his children.

According to a family member of the Cessna 172 pilot, the accident airplane had just undergone an annual inspection, and the short local area flight was the first flight after the inspection.

PERSONNEL INFORMATION

Cessna 170B, N4488B:

At the time of the accident, the pilot of the Cessna 170B was employed by a commercial air carrier as a Boeing 737 captain.

He held a multi-engine land airline transport pilot certificate with type ratings for Boeing 737 and Lockheed L-382 aircraft. He had a flight engineer rating for turboprop engine airplanes, as well as commercial pilot privileges for airplane single-engine land and sea, glider, and rotorcraft. He also held an instrument rotorcraft rating. Additionally, he was a certificated flight instructor, with airplane single and multi-engine, instrument airplane, and glider ratings. His most recent first-class medical certificate was issued on November 4, 2005, and contained no limitations.

No personal flight records were located for the pilot, and the aeronautical experience listed on page 3 of this report was obtained from a review of the airman's FAA records on file in the Airman and Medical Records Center in Oklahoma City. On the pilot's last application for medical certificate, dated November 4, 2005, the pilot indicated that his total aeronautical (civilian) experience consisted of about 7,000 hours, of which 200 were accrued in the previous 6 months.

Cessna 172, N5049A:

At the time of the accident, the pilot of the Cessna 172 was employed as the Alaska Regional Aviation Manager for the U.S. Fish and Wildlife Service.

He held a commercial pilot certificate with airplane single-engine land, single-engine sea, and instrument airplane ratings. He also held a flight instructor certificate with an airplane single-engine land rating. His most recent second-class medical certificate was issued on December 13, 2005, and contained the limitation that he possess glasses for near and intermediate vision.

No personal flight records were located for the pilot, and the aeronautical experience listed on page 3 of this report was obtained from a review of the airman's FAA records on file in the Airman and Medical Records Center in Oklahoma City. On the pilot's last application for medical certificate, dated December 13, 2005, he indicated that his total aeronautical experience consisted of about 12,200 hours, of which 100 were accrued in the previous 6 months.

AIRCRAFT INFORMATION

Cessna 170B, N4488B:

An examination of the Cessna 170B's airframe logbook revealed the airplane was manufactured on April 19, 1955. The most recent annual inspection was conducted on January 2, 2006. At that time, the airframe logbook listed a total time of 6,812.6 hours.

The colors of the airplane included a primary base color of white, with green accent lines.

The airplane was equipped with a single, belly mounted, Flight Strobe, Inc., model 4400, high-intensity strobe light unit.

Cessna 172, N5049A:

An examination of the Cessna 172's airframe logbook revealed the airplane was manufactured on November 10, 1955. The most recent annual inspection was conducted on April 16, 2006. At that time, the airframe logbook listed a total time of 4,299.0 hours.

The colors of the airplane included a primary base color of white, with red accent lines. According to photos of the accident airplane taken before the accident, it was equipped with a single, high-intensity strobe light that was mounted on the empennage, atop the vertical stabilizer.

METEOROLGICAL INFORMATION

The closest official weather observation station is located at the Birchwood Airport, about 7 miles south-southeast of the accident site. At 1156, an Aviation Routine Weather Report (METAR) was reporting in part: Wind, calm; visibility, 10 statute miles; clouds and ceiling, clear; temperature, 41 degrees F; dew point, 31 degrees F; altimeter, 29.89 inHg.

COMMUNICATIONS

Cessna 170B, N4488B

At 1155 the pilot of the Cessna 170B contacted the Palmer Automated Flight Service Station (AFSS), and reported that he had departed from the Birchwood Airport, and then filed a round-robin VFR flight plan, with an anticipated return time of 1600. At 1157, the pilot again contacted the Palmer AFSS specialist on duty and changed the anticipated return time to 1700. No further radio communications were received from the Cessna 170B. The first emergency 911 call was received at the Alaska State Troopers dispatch at 1158. A complete transcript of the recorded radio communications between the pilot and the Palmer AFSS, is included in the public docket of this report.

Cessna 172, N5049A

There were no recorded radio communications from the pilot of the Cessna 172.

The area of the accident did not have any radar coverage.

WRECKAGE AND IMPACT INFORMATION

The National Transportation Safety Board investigator-in-charge (IIC) examined the wreckage at the accident site on April 23, 2006. The wreckage of the Cessna 170B was located about 478 feet to the north of the Cessna 172. Both aircraft came to rest in an area of tidal mud flats, adjacent to the shoreline of the Knik Arm.

Cessna 170B, N4488B

The wreckage of the Cessna 170B had extensive ground impact damage. The fuselage of the airplane was in a near vertical, nose down attitude. The longitudinal axis of the fuselage was oriented on a magnetic heading of about 040 degrees. [All heading/bearings noted in this report are oriented toward magnetic north.]

Except for the left wing that was severed during the in-flight collision, all of the Cessna 170B's major components were found at the main wreckage area. The Cessna 170B's severed left wing was located about 800 feet southwest of the main wreckage site.

The right wing had extensive spanwise leading edge aft crushing, and was oriented with the leading edge down, on about a 45-degree angle. The right wing lift strut remained attached to the wing and lower fuselage attach points. The right wing flight control surfaces remained connected to their respective attach points.

The wing carry-through was broken, and crushed in an aft direction. The fuselage was buckled just aft of the rear window.

The left wing was severed about 12 inches outboard of the fuselage to wing attach points. The left wing lift strut was severed about halfway between the wing and fuselage attach points. The upper portion of the severed left wing lift strut remained attached to the left wing, and the lower portion of the left wing strut remained attached to the fuselage attach point. A detailed inspection around the fracture area of the left wing lift strut revealed thick, black rubber deposits on the white paint that covered the lift strut.

Due to impact damage, the flight controls could not be moved by their respective control mechanisms, but continuity of the flight control cables were established to the cabin/cockpit area.

The propeller remained attached to the engine crankshaft. One propeller blade had slight torsional twisting, and significant aft bending ...