Pilot Debrief

CESSNA 210 near Ramona, CA — 2018-06-01

Final reportANC18LA043
Sign in to save
Date
2018-06-01
Location
Ramona, CA, USA
Airport
RNM
Aircraft
CESSNA 210
Registration
N9410M
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Approach

Probable cause

The failure of the engine-driven hydraulic pump due to the installation of improper cap screws, which resulted in a gap in the pump housing, a subsequent hydraulic leak, and the landing gear collapsing.

NTSB narrative

The private pilot was conducting a personal, cross-country flight. He reported that he attempted to lower the retractable landing gear during a visual approach; however, the right main landing gear (MLG) did not fully extend. He attempted to manually pump the landing gear down with the emergency hand pump, but it was very difficult to move, and after several pumps, it would not move at all. Upon landing, the right MLG collapsed and the airplane impacted the ground, which resulted in substantial damage to the right horizontal stabilizer and elevator. Postaccident examination and tests revealed that, when the MLG system was tested using the airplane’s engine-driven hydraulic pump, fluid started leaking from a gap in the pump’s diaphragm seal between the front plate assembly and the rear housing assembly, and the MLG would not extend. Subsequently, the MLG system was tested with an external hydraulic pump, and it functioned properly. The two front plate cap screws on the side of the leaking pump gap were loose, had only three or four threads engaged with the rear assembly, and had insufficient shank length. The corresponding rear housing internal threads were sheared. Due to the installation of cap screws with insufficient shank length, fewer threads were engaged when the screws were tightened. The insufficient length of the shanks likely led to excessive force being applied on the engaged threads when the cap screws were installed, the threads being damaged, and a gap in the pump housing to develop, which allowed fluid to leak from the pump when it was pressurized. The hydraulic leak prevented the right MLG from fully extending and resulted in it collapsing upon landing.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Pilot could have aborted the landing when landing gear did not lock down.

NTSB coding

Evidence available

  • Photos
  • 5 docket documents
View NTSB final reportView NTSB docket

Docket documents5

Related mishaps