Accident Gulfstream G-IV N121JM,

ASN Wikibase Occurrence # 320519

Date:	Saturday 31 May 2014
Time:	21:40
Type:	Gulfstream G-IV
Owner/operator:	Arizin Ventures, LLC
Registration:	N121JM
MSN:	1399
Year of manufacture:	2000
Total airframe hrs:	4950 hours
Cycles:	2745 flights
Engine model:	Rolls-Royce Tay 611
Fatalities:	Fatalities: 7 / Occupants: 7
Aircraft damage:	Destroyed, written off
Category:	Accident
Location:	Bedford-Hanscom Field, MA (BED) - United States of America
Phase:	Take off
Nature:	Private
Departure airport:	Bedford-Hanscom Field, MA (BED/KBED)
Destination airport:	Atlantic City International Airport, NJ (ACY/KACY)
Investigating agency:	NTSB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
A Gulfstream G-IV corporate jet was destroyed in a takeoff accident at Bedford-Hanscom Field, MA (BED). All four passengers and three crew members were killed in the accident.
During the engine start process, the flight crew neglected to disengage the airplane's gust lock system, which locks the elevator, ailerons, and rudder while the airplane is parked to protect them against wind gust loads. Further, before initiating takeoff, the pilots neglected to perform a flight control check that would have alerted them of the locked flight controls. A review of data from the airplanes quick access recorder revealed that the pilots had neglected to perform complete flight control checks before 98% of their previous 175 takeoffs in the airplane, indicating that this oversight was habitual and not an anomaly.
A mechanical interlock between the gust lock handle and the throttle levers restricts the movement of the throttle levers when the gust lock handle is in the ON position. According to Gulfstream, the interlock mechanism was intended to limit throttle lever movement to a throttle lever angle (TLA) of no greater than 6° during operation with the gust lock on. However, postaccident testing on nine in-service G-IV airplanes found that, with the gust lock handle in the ON position, the forward throttle lever movement that could be achieved on the G-IV was 3 to 4 times greater than the intended TLA of 6°.
During takeoff from runway 11 at Bedford-Hanscom Field, which is 2137 m (7011 feet) long, the pilot-in-command (PIC) manually advanced the throttle levers, but the engine pressure ratio (EPR) did not reach the expected level due to the throttles contacting the gust lock/throttle lever interlock. The PIC did not immediately reject the takeoff; instead, he engaged the autothrottle, and the throttle levers moved slightly forward, which allowed the engines to attain an EPR value that approached (but never reached) the target setting.
As the takeoff roll continued, the second-in-command made the standard takeoff speed callouts as the airplane successively reached 80 knots, the takeoff safety speed, and the rotation speed. When the PIC attempted to rotate the airplane, he discovered that he could not move the control yoke and began calling out "(steer) lock is on." At this point, the PIC clearly understood that the controls were locked but still did not immediately initiate a rejected takeoff. If the flight crew had initiated a rejected takeoff at the time of the PICs first "lock is on" comment or at any time up until about 11 seconds after this comment, the airplane could have been stopped on the paved surface. However, the flight crew delayed applying brakes for about 10 seconds and further delayed reducing power by 4 seconds; therefore, the rejected takeoff was not initiated until the accident was unavoidable.
The airplane thus failed to stop on the runway and continued onto the runway safety area and then the grass. The airplane continued on the grass, where it struck approach lighting and a localizer antenna assembly, before coming to rest in a gully, on about runway heading, about 1,850 feet from the end of the runway. A postcrash fire consumed a majority of the airplane aft of the cockpit; however; all major portions of the airplane were accounted for at the accident site. The nose gear and left main landing gear separated during the accident sequence and were located on the grass area between the safety area and the gully.

Probable Cause: "The NTSB determines that the probable cause of this accident was the flight crewmembers failure to perform the flight control check before takeoff, their attempt to take off with the gust lock system engaged, and their delayed execution of a rejected takeoff after they became aware that the controls were locked. Contributing to the accident were the flight crews
habitual noncompliance with checklists, Gulfstream Aerospace Corporations failure to ensure that the G-IV gust lock/throttle lever interlock system would prevent an attempted takeoff with the gust lock engaged, and the Federal Aviation Administrations failure to detect this inadequacy during the G-IVs certification."

METAR:

00:56 UTC / 20:56 local time:
KBED 010056Z 00000KT 10SM CLR 09/04 A3027 RMK AO2 SLP264 T00940044

01:56 UTC / 21:56 local time:
KBED 010156Z 00000KT 10SM CLR 08/06 A3028 RMK AO2 SLP268 T00780056
Wind: calm; Visibility: 10 or more miles; sky clear below 12,000 feet AGL; Temperature: 8°C, Dewpoint: 6°C; Pressure 1025 mb

Accident investigation: