?On December 8, 2014, about 1041 eastern standard time, an Embraer EMB-500 airplane (marketed as the Phenom 100), N100EQ, registered to and operated by Sage Aviation LLC, crashed while on approach to runway 14 at Montgomery County Airpark (GAI), Gaithersburg, Maryland. The airplane impacted three houses and the ground about 3/4 mile from the approach end of the runway. A postcrash fire involving the airplane and one of the three houses, which contained three occupants, ensued. The pilot, the two passengers, and the three people in the house died as a result of the accident. The airplane was destroyed by impact forces and postcrash fire. The flight was operating on an instrument flight rules flight plan under the provisions of 14 Code of Federal Regulations (CFR) Part 91. Visual meteorological conditions prevailed at the time of the accident. Data from the airplane�s cockpit voice and data recorder (CVDR) indicated that the takeoff about 0945 from Horace Williams Airport, Chapel Hill, North Carolina, and the cruise portion of the flight were uneventful. CVDR data showed that about 15 minutes after takeoff, the passenger in the right cockpit seat made a statement that the airplane was "in the clouds." A few seconds later, the airplane�s engine anti-ice system and the wing and horizontal stabilizer deice system were manually activated for about 2 minutes before they were manually turned off. About 6 minutes later, a recording from the automated weather observing system (AWOS) at GAI began transmitting over the pilot�s audio channel, containing sufficient information to indicate that conditions were conducive to icing during the approach to GAI. The CVDR recorded no activity or faults during the rest of the flight for either ice protection system, indicating that the pilot did not turn the systems back on. Before the airplane descended through 10,000 ft, in keeping with procedures in the EMB-500 Pilot Operating Handbook, the pilot was expected to perform the Descent checklist items in the Quick Reference Handbook (QRH), which the pilot should have had available in the airplane during the flight. Based on the AWOS-reported weather conditions, the pilot should have performed the Descent checklist items that appeared in the Normal Icing Conditions checklist, which included turning on the engine anti-ice and wing and horizontal stabilizer deice systems. That action, in turn, would require the pilot to use landing distance performance data that take into account the deice system�s activation. CVDR data show that, before beginning the descent, the pilot set the landing reference (Vref) speed at 92 knots, indicating that he used performance data for operation with the wing and horizontal stabilizer deice system turned off and an airplane landing weight less than the airplane�s actual weight. Using the appropriate Normal Icing Conditions checklist and accurate airplane weight, the pilot should have flown the approach at 126 knots (a Vref of 121 knots +5 knots) to account for the icing conditions. The NTSB�s investigation found that the pilot�s failure to use the wing and horizontal stabilizer deice system during the approach (even after acknowledging the right seat passenger�s observation that it was snowing when the airplane was about 2.8 nautical miles from GAI) led to ice accumulation, an aerodynamic stall at a higher airspeed than would occur without ice accumulation, and the occurrence of the stall before the aural stall warning sounded or the stick pusher activated. Because the deice system was not activated by the pilot before landing, the band indications (low speed awareness) on the airspeed display did not appropriately indicate the stall warning speed. The NTSB�s aircraft performance study found that there would have been sufficient warning of an aerodynamic stall had the wing and horizontal stabilizer deice system been used during the approach. Once the airplane stalled, its altitude was too low to recover. Based on available evidence, the NTSB could not determine why the pilot did not turn on the wing and horizontal stabilizer deice system during the approach to GAI. The pilot�s EMB-500 instructors reported that use of both ice protection systems was covered during initial and recurrent training, and the pilot turned on both systems when he encountered conditions conducive to icing shortly after taking off on the accident flight. This information suggests that the pilot was informed about the criteria for using these systems. The NTSB considered several scenarios in evaluating the pilot�s actions and identified the following areas for improvement to support safe operation of turbofan airplanes that require a type rating and are certified for single-pilot operations and flight in icing conditions, such as the EMB-500:Especially when conducting single-pilot operations, pilots of these airplanes would benefit from a system that provides automatic alerting when the ice protection systems should be activated. Postaccident interviews with the pilot�s first EMB-500 instructor revealed that the pilot had a tendency to freeze up and fixate on a subtask at the expense of other critical subtasks; thus, it is possible that the pilot forgot to activate the wing and horizontal stabilizer deice system during the approach (a relatively high workload phase of flight) to GAI. In a single-pilot operation, no additional crewmember is present to help detect an error of omission. Further, 14 CFR Part 91 operations do not necessarily share the same regulatory and organizational controls as 14 CFR Part 121 and Part 135 operations, which have more stringent requirements, oversight, and training that can all help to promote consistency in performance. ?Pilots of these airplanes would benefit from training beyond what is required to pass a check ride. Despite being described by his first EMB-500 instructor as very intelligent and highly motivated, the accident pilot needed a considerable amount of extra training time to prepare for his EMB-500 check ride. Although his instructors said that he was proficient by the time he passed his check ride and that all of the required special emphasis areas were addressed in some manner, evidence from the flight before the accident flight�as well as errors made by the pilot during the accident flight�revealed significant weaknesses in his capabilities.