N29GA

On December 2, 2024, about 1530 Pacific standard time (all times PST), a Gulfstream AM CORP COMM DIV 690D, N29GA, was substantially damaged when it was involved in an accident near Spokane, Washington. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

During the GPS instrument approach to runway 04L at Felts Field Airport (SFF), Spokane, Washington, the airplane encountered moderate rime icingand a broken ceiling about 300 ft above ground level (agl). The pilot reported that, before entering the clouds, he confirmed that all deicing equipment was activated. The airplane exited the cloud layer about 300 ft agl. The airplane began to descend below the glide path, so the pilot advanced the engine throttles, but both engines were unresponsive. He initiated a forced landing to soft terrain short of the runway threshold. During the landing roll, the landing gear collapsed and the airplane came to rest upright.

According to the Pilot’s Operating Handbook, the airplane was certificated for flight in known icing conditions and was equipped with deicing and anti-icing systems. The deice system included deice boots for the empennage and both wings, as well as the propellers. The function of the deicer systems was to eliminate ice after it accumulated. The anti-icing systems were designed to prevent ice accumulation and were to be placed in operation before entering flight conditions conducive to the formation of ice. The anti-icing systems included a heated stall warning, rudder horn anti-icer, rudder tab anti-icer, generator inlet anti-icer, electrically heated windshield, and pitot-static heaters.

ADS-B data showed that the airplane departed the DeLaurentis Airport (OKH), Oak Harbor, Washington, at 1429:10 PST and ascended to 1,625 ft mean sea level (msl) before turning to the east. The airplane continued on an easterly heading and ascended to about 23,600 ft msl. At 1508:10, the airplane began a descent toward SFF. At 1523:01, the airplane made a right descending turn to the southeast and was at an altitude of 5,250 ft msl. At 1527:02, the airplane made a left turn toward the northeast, consistent with the GPS approach to SFF, and was at an altitude of 3,900 ft msl. The last recorded ADS-B target, at 1533:18, showed that the airplane landed about 1,000 ft short of the runway threshold, with an altitude of 1,900 ft msl.

The forecasts issued by the NWS Spokane Weather Forecast Office surrounding the time of the accident were as follows:

At 0933 PST, effective from 1000 PST on December 2 to 1000 PST on December 3, winds will be variable from any direction at 3 kts. Visibility is expected to be > 6 statute miles. The sky will be overcast with a cloud base at 600 ft agl.

Starting at 1400 PST on December 2, winds will remain variable at 3 kts and visibility is expected to remain > 6 statute miles. The overcast cloud layer is expected to rise to 1,000 ft agl.

Starting at 2000 PST on December 2, winds will remain variable at 3 kts, and visibility is expected to remain > 6 statute miles. The overcast cloud layer is expected to drop back to 600 ft agl.

An amended report was issued at 1418 PST, effective from 1400 PST on December 2 to 1000 PST on December 3, indicating winds calm at 0 kts, visibility of 4 statute miles, mist, and broken clouds at 300 ft agl, with an overcast layer at 600 ft agl. Starting at 1500 PST on December 2, a rapid change is expected to occur, with variable wind direction at 3 kts, visibility > 6 statute miles, and overcast clouds at 600 ft agl.

The NWS issued a series of AIRMETs at 1045 PST for the area, primarily for IFR and mountain obscuration conditions.

The NWS GFA flight categories chart for ceilings and visibility current at the time of the accident depicted an extensive area of LIFR conditions over the area due to low ceilings and freezing fog.

The weather observation for SFF at 1553 PST indicated calm wind, visibility of 2 miles in mist, a broken ceiling at 300 ft, overcast at 600 ft, temperature of -1°C, dew point temperature of -1°C, and altimeter of 30.42 inches of mercury. Remarks indicated an automated observation system with a precipitation discriminator, sea-level pressure of 1032.4 hectopascals, temperature of -0.6°C, dew point of -1.1°C, a 6-hour maximum temperature of 0.0°C, a 6-hour minimum temperature of -1.1°C, and 3-hour pressure tendency risen 0.6 hectopascals.

Postaccident site examination revealed that the airplane came to rest upright with the landing gear collapsed underneath the fuselage. The first identified point of contact with the terrain was skid marks about 1,122 ft southwest of where the airplane came to rest. Various locations on both sides of the airplane’s fuselage exhibited crushing and bending. Both propeller assemblies were fracture separated from the engines and were located in the debris path. Remnants of moderate rime icing were observed on the right and left wing leading edges. Indications of icing were also still visible on the propeller spinner, vertical and horizontal surfaces, and two top fuselage antennas. Severe icing was observed on the stall warning vane (figure).

Figure. View of ice on the stall warning vane. (Source: FAA)

Examination of the recovered wreckage revealed buckling and crushing damage throughout the fuselage. Recovery personnel had separated both the left and right wings at the wing root to facilitate recovery. Continuity of the stall warning vane heat was established from the cockpit switch to the heating element of the stall warning vane. Power was applied to the wires of the heating element, and the stall warning vane heating element was hot when touched by hand. When power was applied to the airplane the pitot heat on both the left and right pitot tubes activated. Both left and right pitots were hot when touched by hand. Control continuity of the power levers and the condition levers for both engines was established from the cockpit controls to both engines. Both the power control cables and condition lever cables had separations (cuts) near the wing roots and engine nacelles, consistent with cuts by recovery personnel to facilitate recovery.

A visual inspection was conducted of the left and right wing fuel systems with no obstructions identified. Continuity of the remainder of the fuel system from the fuel tanks throughout the system to the engine nacelles was established. Air pressure was applied to the fuel lines for both engine nacelles and fuel was observed draining from both fuel bladders. Power was applied to the airframe fuel pumps at the wing roots, and the airframe fuel pumps audibly functioned.

A sample of the recovered fuel was tested using a Misco Palm Abbe digital refractometer for anti-icing aviation fuel additive. The reading on the meter was 1.3341, consistent with positive indications of the fuel additive.

Subsequent examination and test running of both engines revealed no preaccident mechanical failures or malfunctions with either engine that would have precluded normal operation. Both engines were operated at various power settings and responded to power lever inputs, including rapid power lever increases. Both engines’ anti-ice valves were activated from the control room and there was audible actuation of the anti-ice valve solenoid.