Chamblee, GA, USA
N969CB
CESSNA T337G
Shortly after takeoff on a hot day, after the airplane was about 10 miles from the departure airport, the rear engine failed for undetermined reasons. The pilot turned the airplane back toward the airport, feathered the rear engine, and maintained front engine power at the top of the green arc of the manifold pressure gage, at 33 inches of manifold pressure. The airplane did not maintain altitude at that power setting, and to avoid houses and vehicles on the ground, the pilot performed a forced landing at a water treatment plant. During the landing, the airplane struck the top of a concrete structure, hit the ground, and became engulfed in flames. According to the owner’s manual, after an engine failure, the remaining engine power to be used isto be "increased as required." The published maximum power setting was 37 inches of manifold pressure at "red line," without any time limitations. A performance calculation indicated that at the existing ambient temperatures, and at that power setting, the airplane should have climbed at least 290 feet per minute. Additional references to the use of a 37-inch power setting, including performance calculations, were noted in the owner’s manual.
HISTORY OF FLIGHT On August 8, 2007, about 1940 eastern daylight time, a Cessna T337G, N969CB, was destroyed during a forced landing near Chamblee, Georgia. The certificated commercial pilot and the non-pilot/owner were seriously injured. Visual meteorological conditions prevailed. No flight plan was filed for the flight, which departed Dekalb-Peachtree Airport (PDK), Atlanta, Georgia, for Medina Municipal Airport (1G5), Medina, Ohio, about 1930. The personal flight was conducted under 14 Code of Federal Regulations Part 91. In a written statement, the pilot stated that shortly after takeoff, the rear engine manifold pressure dropped to 25 inches, and the airplane "became sluggish in the climb." In addition, the fuel flow dropped to 24 pounds per hour (pph), when it should have been between 90 and 100 pph, and the cylinder head temperature gauge indicated cooling. The pilot manipulated the rpm lever for the engine and turned on the fuel pump, and as she did so, the fuel flow indicated 0 pph. The pilot subsequently attempted an engine restart, which was unsuccessful. The pilot turned the airplane back toward the departure airport, and became concerned that it could not maintain altitude, even though the front engine was "indicating full power." The pilot also thought that the front engine could not "overcome the high density altitude because of such a hot day," as the airplane continued to lose altitude and airspeed. She was concerned the airplane would land in trees or someone’s house, and searched for an open field. The last thing she remembered was lowering the landing gear. About 6 weeks after the accident, the pilot was interviewed by an insurance adjuster. The interview was recorded, and a transcript was made, with the pilot providing permission to the adjuster to share the information with the Safety Board. According to the transcript, the pilot conducted a preflight inspection of the airplane, sumped the fuel, checked it for discoloration and water, and added oil to both engines. She also completed an engine run-up before takeoff. The pilot subsequently performed a "static" takeoff, which she described as, "leave the brakes on, stand the throttles up to make sure…the turbochargers don’t hang up," obtain "between 33 inches and the red line, and generate full power," and verify again that the rear engine was operating normally. The pilot then released the brakes, and the airplane took off with "no problems." Once airborne, with the landing gear and flaps up, about 500 feet above the ground, the pilot reduced power to "the top of the green, which is about 33 inches of manifold pressure, and brought the propeller levers to about 2,600, 2,650…to get them to sync in that range." The pilot turned the airplane on course, to about 015 degrees magnetic, toward Medina, and the airplane continued to climb at "a normal rate." A minute or two later, the rear engine manifold pressure "just instantly dropped" dropped to 25 inches. The pilot advised the passenger, and noted that the rear engine gauges indicated 900 rpm and 24 pph fuel flow. There had also been a change in the sound of the engine, and the pilot thought that it had "lost the turbo charger." The pilot subsequently moved the rear engine throttle full forward, then brought it "all the way back," but the manifold pressure remained at 25 inches. The pilot then moved the propeller control forward, and the propeller rpm dropped to about 650, so she had the passenger activate the rear engine fuel pump. The rear engine cylinder head temperature indicators were also flashing "high cool," so at that point the pilot informed the passenger that she thought they had "lost" the rear engine, and she then flew the "blue line" airspeed. At the time of the engine failure, the pilot estimated the airplane was 1,000 to 1,500 feet above the ground, and between 2,700 feet and 3,000 feet above mean sea level (msl). GPS indicated a small airport about 6 miles away, but the pilot felt the larger airport they had just departed, about 10 miles to the south, would be better due to emergency equipment and a control tower. The pilot then began a gradual turn back toward the south, and while doing so, asked the passenger to verify rear engine switch positions. She then attempted an engine restart, and when it was unsuccessful, she contacted DeKalb-Peachtree Tower and advised the controller of the situation. As the pilot was communicating with the tower controller, she noticed that at blue line airspeed, the airplane was losing 50 to 70 feet per minute of altitude. She then feathered the rear engine, but the airplane continued to lose altitude. About 6 to 7 miles from the airport, the pilot advised the passenger, "I don’t think we’re going to make it back," and because there were trees and houses "everywhere," and the roads were "packed" with cars, she looked for an open area where she could land the airplane and not hurt anyone on the ground. The pilot also noted that the front engine rpm was 2,650, power was "to the top of the green," the fuel flow was "right," and "everything was in the green as far as the front engine is going." However, "it just was not keeping us at a safe altitude to get back to the airport." The pilot made an approach to the "green area" of a water plant, cleared a transmission line, reduced power and lowered the landing gear. Her memory after that was not clear, but she did recall the passenger waking her up, and her subsequently assisting him in getting out of the wreckage. METEOROLOGICAL INFORMATION Weather at PDK about the time of the accident, included clear skies, winds from 290 degrees true at 5 knots, 7 miles visibility, temperature 34 degrees Celsius (C), dew point 21 degrees C, and an altimeter setting of 29.92 inches Hg. AIRCRAFT INFORMATION The airplane, which was manufactured in August 1975, was powered by two Teledyne Continental Motors TSIO-360-CB engines in an in-line, push-pull configuration, with each engine producing up to 225 horsepower at 37 inches of manifold pressure. The current owner registered the airplane in June 2005, and the latest annual inspection was completed in September 2006. A replacement turbocharger exhaust bypass valve (wastegate) was installed on the rear engine on January 12, 2007, and again on May 23, 2007. According to the pilot, the airplane was about 200 pounds under maximum gross weight at the time of the accident. PERSONNEL INFORMATION The pilot, age 34, held a commercial pilot certificate with airplane single engine land, multi engine land, and instrument airplane ratings, and a CL-65 rating with "SIC privileges only." The pilot reported 4,650 hours of total flight time, with 145 hours in make and model. Her latest FAA first class medical certificate was issued on June 5, 2007. WRECKAGE AND IMPACT INFORMATION An examination of the accident site by an FAA inspector and representatives of the airplane and engine manufacturer revealed that the left wing of the airplane had struck a 50-foot light pole. The airplane then "made a glancing blow" to the top of a concrete structure, hit the ground, and almost completely burned. An examination of the airplane confirmed control continuity to all flight control surfaces. The flaps and landing gear were retracted. The propeller from the aft engine displayed no damage, and was in a "feathered" position. The propeller from the front engine was separated aft of the propeller flange. One of the propeller blades from the front engine displayed some leading edge damage, and was bent aft approximately 5 degrees at mid-span. The front engine propeller was forwarded to the manufacturer, McCauley, for further examination under FAA oversight. According to the manufacturer’s report, there were no indications of any propeller failure prior to impact. The propeller was operating at impact; however, the exact power at impact could not be determined. Witness marks indicated that the propeller was operating at an angle of approximately 15 degrees at impact, with 12.5 degrees equaling a low pitch angle. From November 27, 2007 through November 29, 2007, the engines were examined at the manufacturer’s facility with Safety Board oversight. The pilot was contacted during the examinations, and confirmed that after the rear engine failure, she had maintained front engine power at "the top of the green." The examinations of both engines, including the accessories, revealed extensive thermal damage. Of those items that could be examined, including the internal engine parts, there was no evidence of any anomaly to either engine that would have precluded normal operation prior to the accident. ADDITIONAL INFORMATION According to the airplane owner’s manual: The dual engine manifold pressure gage indicated, within a green arc, a "normal operating range" of 17 to 33 inches. The "maximum pressure" was 37 inches at "red line," without any time limitations noted. The single-engine rate-of-climb (blue Line) air speed was listed as 102 mph. The ENGINE-OUT DURING FLIGHT procedure found in the aircraft owner’s manual stated: (1) Power -- INCREASE as required (2) Inoperative engine -- IDENTIFY (3) Cowl flaps -- AS REQUIRED (4) Mixture -- ADJUST (5) Inoperative engine -- ATTEMPT RESTART (6) Inoperative engine -- SECURE a. Mixture -- IDLE CUT-OFF b. Propeller – FEATHER c. Ignition Switch – OFF d. Alternator Switch – OFF e. Fuel Selector – FUEL OFF f. Cowl Flaps – CLOSED g. Synchrophaser -- OFF The "Single-Engine Maximum Rate-of-Climb Data Chart" found in the owner’s manual indicated that the airplane, at maximum gross weight, and at 5,000 ft msl, should have been able to climb about 290 feet per minute with the ambient temperature conditions that existed at the time. Notes attached to the chart stated that the operating engine must be operated at 37 inches of manifold pressure, at 2,800 rpm, and that the inoperative propeller had to be feathered to obtain the results listed in the chart. The "Single Engine Service Ceiling Chart" found in the owner’s manual was also predicated on the use of 37 inches of manifold pressure and 2,800 rpm.
The pilot’s failure to utilize all of the power available following an engine failure. Contributing to the accident were the failure of the rear engine for undetermined reasons.
Source: NTSB Aviation Accident Database
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