On June 15, 2019, about 0932 Pacific daylight time, a Cessna 182M airplane, N777RK, was substantially damaged when it was involved in an accident near Cable Airport (CCB), Upland, California. The private pilot and two passengers were seriously injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

The pilot reported that during takeoff, as the airplane ascended through about 250 ft above ground level, the engine began to “sputter,” and he initiated a left turn to return to the airport. Shortly after, the engine lost all power, and he initiated a forced landing to an open area south of the departure runway on airport property. The pilot stated that he intended to land “hard to break both landing gear legs off so the airplane would slide to a stop;” however, the airplane bounced upon landing, became airborne, and traveled across a road before it landed in a parking lot, impacted trees, and came to rest upright.

Examination of the airplane by local law enforcement revealed that the left wing was separated, and the fuselage was structurally damaged. The airplane was recovered to a secure location for further examination.

Examination of the Continental Motors O-470-R engine revealed that compression was obtained on all cylinders except for the No. 2 cylinder. The No. 2 cylinder was examined internally using a lighted borescope. The No 2. cylinder was removed. Scuffing was observed throughout the sides of the piston.

The airplane was equipped with an engine monitoring unit. Data from the accident flight was downloaded from the unit and had a sample rate of every 6 seconds. The data spanned 1 minute, 42 seconds, from the time takeoff power was applied to the last recorded data plot. When takeoff power was applied at a unit time of 16:21:56, rpm, manifold pressure, and fuel flow increased. Fuel flow reached a maximum flow rate of 14.5 gallons per hour (GPH) at a unit time of 16:23:02, however decreased briefly for 12 seconds before reducing significantly 24 seconds later. Table 1 shows the manifold pressure, RPM, fuel flow, and altitude for the takeoff sequence.

Unit Time Manifold Pressure RPM Fuel Flow Altitude 16:21:56 18.5 969 2.1 1438 16:22:02 21 1791 3.2 1436 16:22:08 24.7 2383 6.4 1433 16:22:14 27.1 2613 11.9 1426 16:22:20 27.1 2613 12.7 1422 16:22:26 27.1 2613 12.9 1446 16:22:32 27.1 2603 12.3 1536 16:22:38 27.8 2389 12 1615 16:22:44 27 2486 12.5 1701 16:22:50 27.2 2524 12.2 1750 16:22:56 27.9 2238 12.5 1729 16:23:02 27.1 2571 14.5 1675 16:23:08 27.6 2564 13.9 1664 16:23:14 27.5 2585 13.8 1637 16:23:20 16 1522 9.6 1658 16:23:26 15.4 1314 1.6 1627 16:23:32 15.9 1255 1.4 1533 16:23:38 16.9 1205 2.8 1426 Table 1: Portion of downloaded engine monitoring data for the takeoff sequence.

Review of recorded data for the two flights prior to the accident flight, cylinder No. 2’s temperature had exceeded 460° on both flights.  According to the Continental owner’s manual for the O-470-R, the max cylinder head temperature is 460°.

Using the engine performance chart for the O-470-R, it was calculated that the fuel flow at a takeoff power setting should be about 22 gallons per hour.

The carburetor was examined under the supervision of a Federal Aviation Administration inspector. The inspector reported that due to damage to the throttle shaft, fuel flow measurements at any settings other than full throttle could not be obtained. When the carburetor was tested at full throttle, the carburetor had a flow rate slightly higher than the optimal specification, consistent with a slightly rich condition.

The FAA’s Pilot’s Book of Aeronautical Knowledge states in part “An overly lean mixture causes detonation, which may result in rough engine operation, overheating, and/or a loss of power.”

“Detonation is an uncontrolled, explosive ignition of the fuel-air mixture within the cylinder’s combustion chamber. It causes excessive temperatures and pressures which, if not corrected, can quickly lead to failure of the piston, cylinder, or valves. In less severe cases, detonation causes engine overheating, roughness, or loss of power.

Detonation is characterized by high cylinder head temperatures and is most likely to occur when operating at high power settings.

Common operational causes of detonation are: - Use of a lower fuel grade than that specified by the aircraft manufacturer - Operation of the engine with extremely high manifold pressures in conjunction with low rpm - Operation of the engine at high power settings with an excessively lean mixture”