Page:CAB Aircraft Accident Report, Northwest Airlines Flight 705.pdf/6

 All flight control systems were carefully studied for any indications of possible control malfunctions. Absolute positions of control linkages and cables could not be established, because of the extensive breakup. However, there was no evidence of any control system failure or malfunction except those associated with in-flight breakup or ground impact. The stabilizer trim jackscrew was found positioned to within $3/32$ inch of the aircraft nosedown mechanical stop. This is the stopping point of the jackscrew when it is operated electronically.

There was no evidence of arcing, burning, or electrical overload on any of the generators. All available wiring bundles were examined for evidence of electrical arcing or bending but none was found. There was no evidence of a lightning strike on any of the wreckage. A portion of the fuel vent system in the No. 1 reserve tank was never recovered, however, the remainder of the venting in both wings was unobstructed and showed no fire damage. There was no evidence of internal wing tank fires prior to initial breakup. In addition, no evidence of hail damage was found on the nose section, or the leading edges of the wing, tail, or engine coverings.

Examination of the aircraft instruments revealed that the nosedown rotational pitch stops of both vertical gyros, which furnish pitch and roll displacement intelligence for the HZ-4 and other devices, received severe impact damage as a result of a rapid rotation of the aircraft about its pitch axis. The compass instruments were indicating northeasterly headings at the time power was interrupted.

Selected samples of the aircraft wreckage were sent to the Federal Bureau of Investigation (FBI) laboratory for examination. However, no explosive residues were found.