LAX07LA186

A Certified Flight Instructor (CFI) was providing multiengine instruction to the pilot. They were in the traffic pattern, approximately 800 feet above ground level (agl), after completing several touch-and-go landings. The CFI stated that his regular method for setting up practice engine-out landings for a student was to close the mixture, allow the student to go through the process of controlling the airplane, and simulating the procedures to feather the inoperative engine's propeller. The instructor would then return the mixture to full rich, and verify engine operation. This would occur on downwind, and then the landing would be completed with the simulated inoperative engine at idle. On downwind, the instructor closed the mixture on the left engine. During this maneuver, the pilot turned the airplane left from base to final and the airspeed decreased. The airplane rolled sharply to the left and lost altitude. The instructor reduced both throttles and regained control of the airplane just as it collided with the roof of one house, bounced across another roof, and came to rest on top of a third house. The Federal Aviation Administration recommends that in-flight simulated engine failures at altitudes below 3,000 feet agl be introduced only by reduction of the throttle. Post-crash inspection of the engine and airframe found no anomalies that would have prevented normal operation.

History of flight

On June 4, 2007, about 1022 Pacific daylight time, a Piper PA-34-200, N4463T, collided with houses on final approach to Cable Airport, Upland, California. Roxy Corporation was operating the airplane under the provisions of 14 Code of Federal Regulations (CFR) Part 91. The certified flight instructor (CFI) pilot, the commercial pilot undergoing instruction (PUI), and one passenger sustained minor injuries; the airplane sustained substantial damage. The cross-country instructional flight departed Van Nuys, California, at an undetermined time en route to Upland. Instrument meteorological conditions prevailed at the nearest official reporting station, and an instrument flight plan had been filed.

The PUI was receiving instruction to prepare for a reexamination of a portion of the commercial pilot multiengine practical examination. The Designated Pilot Examiner (DPE) noted that, during the initial examination 2 days prior to the accident, the PUI failed to maintain minimum best single-engine rate of climb speed (Vyse) when simulating a loss of engine power on takeoff. After restoring controls to the PUI, the DPE noted that the approach to landing was high and fast. They did a go-around. On the second approach to landing, the PUI lined up on the left side of the runway and in a 30-degree bank. The PUI's instructor indicated that he had not seen this type of performance.

A Federal Aviation Administration (FAA) inspector interviewed the PUI. He was receiving multiengine instruction from the CFI. They were in the landing pattern, and completed several touch-and-go landings. On downwind, the CFI reduced power on one engine. As they turned left from base to final, the bank angle got steep. The airplane lost altitude, and collided with the roof of one house, bounced across another roof, and came to rest on top of a third house.

In a written statement, the CFI reported that they had departed Van Nuys under instrument flight rules (IFR). Upon arrival at Cable Airport, the PUI executed an instrument approach to the runway. The CFI noted that visual meteorological conditions prevailed at the airport, and they cancelled IFR with air traffic control and continued the flight under visual flight rules at a traffic pattern altitude of about 800 feet above ground level (agl).

The CFI reported that he wanted to perform engine-out landing practice with the PUI. He listed the following as his own procedure for the maneuver, which he stated he had performed hundreds of times:

1. At pattern altitude, close the mixture of one engine

2. Wait until the student goes through the immediate procedure of: controlling the airplane, adding full power, cleaning up flaps and gear, identifying the dead engine, verifying the dead engine with the throttle (by closing the dead engine throttle), feather (touch the correct propeller control to simulate feather).

3. Open the dead engine mixture to full.

4. Verify that the engine is working by advancing the closed throttle a little, and then close it again.

The CFI noted that all the above is done while the airplane is still on downwind. The simulated engine-out practice continues with the engine at idle and not really out.

The PUI performed one such maneuver, which the CFI reported was marginal, and the PUI initiated a touch-and-go on the runway in order to perform the engine-out procedure again. The CFI reported that he initiated the same maneuver with the steps listed above for the left engine, while on the downwind leg for the pattern. The CFI noted that due to the tight traffic pattern, the PUI initiated a 180-degree turn from the downwind leg to the final approach leg. During the turn, the CFI noticed the airspeed decrease to 100 miles per hour (mph), and notified the PUI not to slow below the blue line. The CFI stated that the blue line (Vyse) is 105 mph for the airplane. The airplane then rolled abruptly to the left, and the CFI took over control of the airplane. The CFI stated that he recovered from the sharp turn, and then attempted to recover from the descent by advancing both engine throttles. The CFI felt an asymmetrical thrust, closed both throttles, and flared the airplane as it collided with the roofs below.

The CFI also commented that he was puzzled as to why the airplane lost control at 100 mph, when the recommended safe speed (Vsse) for engine-out procedures in the airplane is 90 mph, with a red line (minimum controllable single-engine speed (Vmc)) of 80 mph.

On-scene observations

The National Transportation Safety Board investigator that examined the wreckage on scene reported the following information.

The debris path from the first identified point of contact (FIPC) to final resting place was 100 feet in length along a 220-degree magnetic heading. Pieces of airplane were distributed over several adjacent residential rooftops. The elevation of the main wreckage was 1,450 feet. Cable Airport was a distance of 0.61 nautical miles (nm) on a magnetic bearing of 237 degrees.

The FIPC consisted of the landing gear and other exterior airplane parts. These pieces were on the roof of the first struck residence. Imbedded in the roof and east-facing wall of the next residence was the right engine with the propeller still attached. On top of this residence was the portion of the left wing that was aft of the spar with the aileron and flap attached. On top of a third residence was the main wreckage consisting of the fuselage, right wing, forward portion of the left wing, and empennage. The left wing remained attached at the wing root area. The right wing remained attached at its front fitting, but the rear fitting was detached. The left engine remained with the main wreckage, but was detached from the wing. The front right seat separated from the airframe, and was on the south side of this residence in the grass along with some minor airframe parts. Investigators found a spar embedded in the grass near the seat.

First responders moved several switches prior to the investigator's arrival. They moved the magneto switches to the OFF position, the electric boost pump to the OFF position. They did not touch the fuel valves. The MASTER switch was still on when investigators arrived.

The airframe investigator found the fuel valves in the cross-feed position. He noted that it was possible that they could have been moved due to displacement of the wings. He noted that for landing, only one should be in the cross-feed mode.

The engine controls for both engines were at their respective stops. The propeller was at low pitch (high revolutions per minute) stop. The mixture control was at idle cutoff.

Follow up examination

Investigators examined the wreckage at Aircraft Recovery Service, Littlerock, California, on November 13, 2007.

Left Engine

Investigators slung the engine from a hoist, and removed the top spark plugs. All spark plugs were clean with no mechanical deformation. The spark plug electrodes were gray, which corresponded to normal operation according to the Champion Aviation Check-A-Plug AV-27 Chart.

A borescope inspection revealed no mechanical deformation on the valves, cylinder walls, or internal cylinder head.

Investigators manually rotated the crankshaft with the propeller. The crankshaft rotated freely, and the valves moved approximately the same amount of lift in firing order. The gears in the accessory case turned freely. Investigators obtained thumb compression on all cylinders in firing order.

Investigators manually rotated the magnetos, and both magnetos produced spark at all posts.

The vacuum pump drive gear remained unbroken, and the vacuum pump turned freely. All vacuum pump vanes were whole, in position, and moved freely.

The oil sump screen was clean and open; the oil filter was clean.

The fuel injection servo remained undamaged and securely attached at the mounting flange. The throttle and mixture controls were se