Accident Brief: December 2018 – Plane & Pilot Magazine

Nightmare Fire In An Air Ambulance


Amarillo, Texas

Accidents: three Deadly

The pilot and two medical crewmembers departed on an air ambulance flight in night time instrument meteorological circumstances to select up a affected person. After departure, the native air visitors controller noticed the airplane’s main radar goal with an incorrect transponder code in a proper flip and climbing by means of Four,400 ft imply sea degree (msl), which was 800 ft above floor degree (agl). The controller instructed the pilot to reset the transponder to the right code, and the airplane leveled off between Four,400 ft and Four,600 ft msl for about 30 seconds. The controller then confirmed that the airplane was being tracked on radar with the right transponder code; the airplane resumed its climb at a price of about 6,000 ft per minute (fpm) to six,000 ft msl. The pilot modified frequencies as instructed, then contacted departure management and reported “with you at 6,000 [ft msl]” and the departure controller radar-recognized the airplane. About 1 minute later, the departure controller suggested the pilot that he was not receiving the airplane’s transponder; the pilot didn’t reply, and there have been no additional recorded transmissions from the pilot. Radar knowledge confirmed the airplane descending quickly at a fee that reached 17,000 fpm. Surveillance video from a close-by truck cease recorded lights from the airplane descending at an angle of about 45° adopted by an explosion.

The airplane impacted a pasture about 1.5 nautical miles south of the airport, and a postimpact hearth ensued. All main elements of the airplane have been situated inside the particles area. Floor scars on the accident website and injury to the airplane indicated that the airplane was in a steep, nostril-low and wings-degree angle on the time of influence. The airplane’s steep descent and its influence angle are in step with a lack of management.

An airplane efficiency research based mostly on radar knowledge and simulations decided that, in the course of the climb to six,000 ft and about 37 seconds earlier than impression, the airplane achieved a peak pitch angle of about 23°, after which the pitch angle decreased steadily to an estimated -42° at impression. Because the pitch angle decreased, the roll angle elevated steadily to the left, reaching an estimated -76° at influence. The efficiency research revealed that the airplane might fly the accident flight trajectory with out experiencing an aerodynamic stall. The obvious pitch and roll angles, which symbolize the angle a pilot would “feel” the airplane to be in based mostly on his vestibular and kinesthetic notion of the elements of the load issue vector in his personal physique coordinate system, have been calculated. The obvious pitch angle ranged from zero° to 15° as the actual pitch angle steadily decreased to -42°, and the obvious roll angle ranged from zero° to -Four° as the actual roll angle elevated to -78°. This means that even when the airplane was in a steeply banked descent, circumstances have been current that would have produced a somatogravic phantasm of degree flight and resulted in spatial disorientation of the pilot.

Evaluation of the efficiency research and the airplane’s flight monitor revealed that the pilot executed a number of non-commonplace actions in the course of the departure to incorporate: extreme pitch and roll angles, speedy climb, sudden degree-offs, and non-normal ATC communications. Along with the non- Web page 2 of 5 CEN17FA168 commonplace actions, the pilot’s restricted current flight expertise in night time IFR circumstances, and average turbulence would have been conducive to the onset of spatial disorientation.

The pilot’s failure to set the right transponder code earlier than departure, his non-commonplace departure maneuvering, and his obvious confusion relating to his altitude point out a psychological state not at peak acuity, additional growing the probabilities of spatial disorientation. A postaccident examination of the flight management system didn’t reveal proof of any preimpact anomalies that might have prevented regular operation. The engine exhibited rotational signatures indicative of engine operation throughout impression, and an examination didn’t reveal any preimpact anomalies that may have precluded regular engine operation. The injury to the propeller hub and blades indicated that the propeller was working underneath excessive energy within the regular vary of operation at time of impression.

Evaluate of recorded knowledge recovered from airplane’s angle and heading reference unit didn’t reveal any faults with the airplane’s angle and heading reference system (AHRS) through the accident flight, and there have been no upkeep logbook entries indicating any earlier digital angle director indicator (EADI) or AHRS malfunctions. Subsequently, it’s unlikely that faulty angle info was displayed on the EADI that would have misled the pilot in regards to the precise angle of the airplane. A light-weight bulb filament evaluation of the airplane’s central advisory show unit (CADU) revealed that the “autopilot disengage” warning indicator was doubtless illuminated at influence, and the “autopilot trim” warning indicator was probably not illuminated. A filament evaluation of the autopilot mode controller revealed that the “autopilot,” “yaw damper,” and “altitude hold” indicators have been probably not illuminated at impression. The standing of the “trim” warning indicator on the autopilot mode controller couldn’t be decided as a result of the filaments of the indicator’s bulbs have been lacking. Nevertheless, because the CADU’s “autopilot trim” warning indicator was doubtless not illuminated, the mode controller’s “trim” warning indicator was additionally possible not illuminated at impression.

Exemplar airplane testing revealed that the “autopilot disengage” warning indicator would solely illuminate if the autopilot had been engaged after which disconnected. It might not illuminate if the autopilot was off with out being beforehand engaged nor wouldn’t it illuminate if the pilot tried and failed to interact the autopilot by urgent the “autopilot” pushbutton on the mode controller. Because the “autopilot disengage” warning indicator would stay illuminated for 30 seconds after the autopilot was disengaged and was doubtless illuminated at impression, it’s doubtless that the autopilot had been engaged sooner or later in the course of the flight and disengaged inside 30 seconds of the impression; the pilot was reporting to ATC at 6,000 ft about 30 seconds earlier than impression after which the speedy descent started.

The airplane was not outfitted with a recording system that might have recorded the operational standing of the autopilot, and the investigation couldn’t decide the exact occasions at which autopilot engagement and disengagement occurred. Nevertheless, these occasions could be estimated as follows:

  • The pilot doubtless engaged the autopilot after the airplane climbed by means of 1,000 ft agl about 46 seconds after takeoff, as a result of this was the beneficial minimal autopilot engagement altitude that he was taught.
  • In accordance with the airplane efficiency research, the airplane’s acceleration exceeded the autopilot’s restrict load issue of +1.6g about 9 seconds earlier than influence. If it was engaged presently, the autopilot would have routinely disengaged.
  • The roll angle knowledge from the efficiency research have been according to engagement of the autopilot between two factors: 1) about 31 seconds earlier than influence, throughout climb, when the financial institution Web page three of 5 CEN17FA168 angle, which had stabilized for a couple of seconds, began to extend once more and a couple of) about 9 seconds earlier than influence, throughout descent, at which era the autopilot would have routinely disengaged. Because the autopilot would have decreased the financial institution angle as quickly because it was engaged and there’s no proof of the financial institution angle decreasing considerably between these two factors, it’s probably that the autopilot was engaged nearer to the latter level than the previous. Engagement of the autopilot shortly earlier than the latter level would have left little time for the autopilot to scale back the financial institution angle earlier than it will have disengaged routinely because of exceedance of the traditional load issue restrict.

Subsequently, it’s possible that the pilot engaged the autopilot a couple of seconds earlier than it routinely disconnected about 9 seconds earlier than impression.

The operator reported that the airplane had skilled repeated, sudden, inflight autopilot disconnects, and, two days earlier than the accident, the chief pilot recorded a video of the autopilot disconnecting throughout a flight. Exemplar airplane testing and upkeep info revealed that, in the course of the flight during which the video was recorded, the autopilot’s pitch trim adapter possible skilled a momentary lack of energy for undetermined causes, which resulted within the sequence of occasions noticed within the video. It’s potential that the autopilot disconnected in the course of the accident flight because of the pitch trim adapter experiencing a lack of energy, which must have occurred between 30 and 9 seconds earlier than influence.

A postaccident climate evaluation revealed that the airplane was working in an setting requiring devices to navigate, however it couldn’t be decided if the airplane was in cloud when the lack of management occurred. The sustained floor wind was from the north at 21 knots with gusts as much as 28 knots, and average turbulence existed. The presence of the average turbulence might have contributed to the controllability of the airplane and the pilot’s lack of ability to acknowledge the airplane’s angle and the autopilot’s operational standing.

Possible trigger(s): The pilot’s lack of airplane management on account of spatial disorientation in the course of the preliminary climb after takeoff in night time instrument meteorological circumstances and average turbulence.

NOTE: The report revealed right here is from the NTSB and is printed verbatim and in its full type. 

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