N988JADiamond Aircraft Ind DA 42 · 2009

On May 9, 2022, about 1145 eastern daylight time, a Diamond Aircraft DA42, N988JA, was substantially damaged when it was involved in an accident near Lehighton, Pennsylvania. The flight instructor, pilot receiving instruction, and pilot-rated passenger received minor injuries. The airplane was operated by Gateway Aviation as a Title 14 Code of Federal Regulations Part 91 instructional flight.

The flight instructor reported that, during the instructional flight, he and the pilot receiving instruction shut down and secured the right engine to simulate an engine failure. During the process, the airplane descended “a few hundred feet.” Using the checklist, they attempted to restart the right engine, but realized that it was not producing power. The instructor reported that they chose to perform a forced landing to a field, during which the airplane slid into a ditch.

The pilot receiving instruction stated that, at an altitude around 5,000 ft msl, he and the instructor simulated an engine failure and shut down the right engine as outlined in the checklist. After completing the shutdown and securing the engine, they proceeded to restart the engine again as outlined in the checklist; however, they noticed that the right engine’s propeller was spinning at 1,970 rpm rather than its normal speed of 2,500 rpm. The pilot and instructor continued to troubleshoot as the airplane descended, and began to complete the checklist items for a total loss of engine power. At this time, the airplane was at an altitude about 2,500 to 3,000 ft msl and descending at roughly 500 ft per minute. The airplane was difficult to control, and he and the instructor “became task-saturated” between maintaining control of the airplane, completing checklists, communicating with air traffic control, and navigating toward the nearest airport. They declared an emergency with traffic control and stated that they would be making an off-airport landing.

The pilot-rated passenger reported that he was invited to observe the multi-engine instruction flight. The flight was uneventful until the “drag demonstration,” when the pilots shut down the right engine. After the pilots performed the restart engine procedure, the propeller was turning, and the passenger believed that the engine was on and running. After a few minutes of no communication between the pilots, the flight instructor said, "there is a problem, but I don't know what it is." This caught the passenger’s attention, because he believed it was a mock emergency scenario. He remembered looking at the instrument panel and the right engine was producing 1,950 rpm, but both fuel and oil pressure indications were “in the green range.” The left engine was producing a noticeably higher rpm. He did not remember where the throttle, propeller, and mixture control positions were. The flight instructor then asked, "where's the nearest airport?" The passenger, who was monitoring the flight’s position on his Foreflight application, responded, "7.5 miles east at 11 o'clock." They turned the airplane in that direction, and the passenger periodically directed the pilots to the airport, which was located behind a ridge.

The passenger reported that there was a “lack of communication” between the flight instructor and the pilot receiving instruction, and that “there seemed to be confusion on roles and responsibilities.” He did not hear any checklist items being reviewed and verified. He also noticed that the right propeller was still spinning. Around 1,500 ft msl, the flight instructor took control of the airplane and declared an emergency.

Review of on-scene photographs provided by the Federal Aviation Administration indicated that the mixture control levers were in the full rich position, the propeller control levers were in the fine pitch/high rpm position, the electric fuel pumps were on, and the fuel selectors were on. Digital data cards recovered from the airplane’s avionics system did not contain any useable data.

Postaccident examination of the airplane revealed substantial damage to the fuselage. Further examination of the airplane did not reveal any preimpact failures or anomalies that would have prevented normal operation.

The left engine remained attached to the left wing and its respective engine mount. All three propeller blades, which were found to be in the low pitch/high rpm position, were fractured midspan, with two of the blades missing the outboard section. The engine was deemed to be in suitable condition for a ground run, and each propeller blade was cut to provide clearance from the sides of the recovery trailer during engine operation.

With the top spark plugs removed, the drivetrain was rotated and suction and compression were noted on all cylinders.

External power was applied to the engine starter and an external fuel container with 100LL aviation fuel was used to attempt engine operation. Starter fluid was used initially to help draw fuel into the fuel system. The left engine started and was brought up to normal operating temperature and then run at low rpm ranges due to the shortened propeller blades. No evidence of any preimpact failures or malfunctions were noted during the engine run, and the engine operated normally when the throttle was advanced and retarded. The engine was shut down normally.

The right engine remained attached to the firewall and appeared undamaged. The propeller remained attached to the crankshaft flange and the three blades of the propeller, which were found to be in the low pitch/high rpm position, showed damage at the mid points and were cut similar to the left engine’s propeller blades to facilitate clearance from the recovery trailer.

The magneto timing was checked before the engine start attempts. Both magnetos were timed according to specification. The magnetos could not be run individually during the engine start-up because the keys for the ignition were not present.

The oil sump contained approximately 6.5 quarts of clean oil on the oil level gauge.

The engine was visually examined, and thumb compression and suction were established. External power was applied to the engine starter and an external fuel container with 100LL aviation fuel was used to attempt engine operation. Starter fluid was used initially to help draw fuel into the fuel system. The engine started and was brought up to normal operating temperature and then ran at low rpm ranges due to the shortened propeller blades. No anomalies were noted during the engine run and the engine operated normally when the throttle was manipulated. The engine was shut down normally.

Examination of the engines revealed no anomalies that would have prevented them from producing power.

According to the Airplane Flying Handbook (FAA-H-8083-3C):

Multiengine and single-engine airplanes operate differently during an engine failure. In a multiengine airplane, loss of thrust from one engine affects both performance and control. The most obvious problem is the loss of 50 percent of power, which reduces climb performance 80 to 90 percent. In some cases, after an engine failure, the ability to climb or maintain altitude in a light-twin may not exist. After an engine failure, asymmetrical thrust also creates control issues for the pilot. Attention to both these factors is crucial to safe OEI [one engine inoperative] flight.

Although the propellers of a multiengine airplane may appear identical to a constant-speed propeller used in many single-engine airplanes, this is usually not the case. The pilot of a typical multiengine airplane can feather the propeller of an inoperative engine. Since it stops engine rotation with the propeller blade streamlined with the airplane’s relative wind, feathering the propeller of an inoperative engine minimizes propeller drag. Depending upon single-engine performance, this feature often permits continued flight to a suitable airport following an engine failure.

Feathering is important because of the change in parasite drag with propeller blade angle. When the propeller blade angle is in the feathered position, parasite drag from the propeller is at a minimum. In a typical multiengine airplane, the parasite drag from a single, feathered propeller is a small part the airplane's total drag.

Review of the manufacturer’s Airplane Flight Manual indicated that, given the atmospheric conditions which existed at the time of the accident, if the “DEAD ENGINE” was feathered and secured, and the operating engine was set for maximum continuous power, the airplane would have been able to maintain a positive rate of climb. Guidance was also contained in the emergency procedures section for unfeathering and restarting the engine in flight, which advised that if it was not possible to start the engine, to continue with the “ENGINE SECURING (FEATHERING PROCEDURE).”