Accident Details
On December 2, 2024, at about 1530 Pacific standard time, a Gulfstream AM CORP COMM DIV 690D, registration N29GA, was substantially damaged during an accident near Spokane, Washington. The pilot was not injured. The flight was conducted as a Title 14 Code of Federal Regulations Part 91 personal flight.
Approach and Icing Encounter
The airplane was conducting a GPS instrument approach to runway 04L at Felts Field Airport (SFF), Spokane, Washington. During the approach, the airplane encountered moderate rime icing and a broken ceiling about 300 ft above ground level (agl). The pilot reported that before entering the clouds, he confirmed all deicing equipment was activated. The airplane exited the cloud layer at about 300 ft agl. Subsequently, the airplane began to descend below the glide path. 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.
Aircraft Ice Protection Systems
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.
Flight Path and ADS-B Data
ADS-B data showed that the airplane departed DeLaurentis Airport (OKH), Oak Harbor, Washington, at 1429:10 PST and ascended to 1,625 ft mean sea level (msl) before turning east. The airplane continued easterly and ascended to about 23,600 ft msl. At 1508:10, it began a descent toward SFF. At 1523:01, it made a right descending turn to the southeast at an altitude of 5,250 ft msl. At 1527:02, it made a left turn toward the northeast, consistent with the GPS approach to SFF, at 3,900 ft msl. The last recorded ADS-B target at 1533:18 showed the airplane landing about 1,000 ft short of the runway threshold at an altitude of 1,900 ft msl.
Weather Conditions
The National Weather Service (NWS) Spokane Weather Forecast Office issued forecasts for the period. At 0933 PST, effective from 1000 PST December 2 to 1000 PST December 3, winds were variable at 3 kts, visibility >6 statute miles, overcast with cloud base at 600 ft agl. Starting at 1400 PST, the overcast layer was expected to rise to 1,000 ft agl. An amended report at 1418 PST, effective from 1400 PST, indicated calm winds, visibility 4 statute miles, mist, broken clouds at 300 ft agl, overcast at 600 ft agl. Starting at 1500 PST, rapid change expected: variable wind at 3 kts, visibility >6 statute miles, overcast at 600 ft agl. The NWS issued AIRMETs at 1045 PST for IFR and mountain obscuration. The NWS GFA flight categories chart depicted LIFR conditions due to low ceilings and freezing fog.
The weather observation at SFF at 1553 PST indicated calm wind, visibility 2 miles in mist, broken ceiling at 300 ft, overcast at 600 ft, temperature -1°C, dew point -1°C, altimeter 30.42 inHg. Remarks: automated observation, sea-level pressure 1032.4 hPa, temperature -0.6°C, dew point -1.1°C, 6-hour max temperature 0.0°C, 6-hour min -1.1°C, 3-hour pressure tendency risen 0.6 hPa.
Postaccident Examination
Postaccident site examination revealed the airplane came to rest upright with the landing gear collapsed underneath the fuselage. The first identified point of contact was skid marks about 1,122 ft southwest of the resting position. Various locations on both sides of the fuselage exhibited crushing and bending. Both propeller assemblies were fracture separated from the engines and located in the debris path. Remnants of moderate rime icing were observed on the right and left wing leading edges. Icing was also visible on the propeller spinner, vertical and horizontal surfaces, and two top fuselage antennas. Severe icing was observed on the stall warning vane.
Examination of the wreckage revealed buckling and crushing damage throughout the fuselage. Recovery personnel had separated the wings at the wing root. Continuity of the stall warning vane heat was established from the cockpit switch to the heating element; power was applied and the element was hot. Pitot heat on both pitot tubes activated and was hot. Control continuity of the power levers and condition levers for both engines was established from cockpit to engines. Both power and condition lever cables had separations (cuts) near wing roots and engine nacelles, consistent with cuts by recovery personnel.
A visual inspection of the left and right wing fuel systems found no obstructions. Fuel system continuity from tanks to engine nacelles was established. Air pressure applied to fuel lines resulted in fuel draining from both fuel bladders. Power applied to airframe fuel pumps audibly functioned. A fuel sample tested with a Misco Palm Abbe digital refractometer for anti-icing additive gave a reading of 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 that would have precluded normal operation. Both engines were operated at various power settings and responded to power lever inputs, including rapid increases. Both engines’ anti-ice valves were activated from the control room and audible actuation was noted.
Probable Cause
No probable cause was stated in the source.