Remember, the two aircraft that crashed were not properly maintained and did not meet type design.
I invite you to read the following report from Transport Canada. Altough there was a missing return spring on the accident aircraft, evidence found on multiple other aircraft inspected during the BST investigation, showed the importance of develloping a solution to a potential catastrophic situation. I think the rudder kit is a very cheap insurance that all C150-C152 owners should buy.
From 17 January to 04 February 2000, Transport Canada conducted a maintenance audit of another flight school operator at Saint-Hubert Airport, Québec. During the audit, Transport Canada inspectors found discrepancies that led to the grounding of 22 aircraft for various reasons. Following this maintenance audit, the operator, on 15 February 2000, submitted a Service Difficulty Report (SDR) after inspecting its fleet of 10 Cessna 152 aircraft. On five of these aircraft, there was evidence that the rudder stop plates on the rudder horns had ridden over the stop bolts. Transport Canada also submitted an SDR on the same subject. TSB investigators visited the operator the next day for preliminary examinations of the five aircraft with the rudder problems.
On 22 February 2000, four TSB investigators met at the flight school at Saint-Hubert, with representatives of Laurentide Aviation, Transport Canada, and Cessna, to examine the aircraft with suspected rudder anomalies to determine if rudder anomalies were related to the circumstances that led to the accident involving C-GZLZ. It was determined that a very hard left rudder pedal input could cause the right side of the rudder horn to deflect slightly and over-travel and hang up momentarily on the stop plate (bumper) on the top of the stop bolt. Witness marks were evident showing that this had occurred on previous occasions. However, a slight application of right rudder pedal would release the rudder. During those tests, it was not possible to make the rudder horn stop plate override the stop bolt and hook behind and below it, as was found in the accident aircraft. It was noted during these tests that the rudder was being stopped from further over-travel in its movement by contact with the left elevator. Witness marks found on the accident aircraft correspond with previous contact between the rudder and elevator.
To better understand whether and how the rudder could have over-traveled and jammed on the accident aircraft, additional tests were conducted on a similar aircraft. The test conditions included removing the right rudder bar return spring and disconnecting the right rudder cable. As with a loose rudder cable, this facilitated over-deflection of the rudder to the left. It was also determined that moving the elevator to a position more than two-thirds up--increasing the clearance between the rudder and the elevator--permitted further travel of the rudder. In that condition, a very hard left rudder pedal input permitted the rudder to over-travel and the stop plate locked below and behind the stop bolt, exactly as had been found in the accident aircraft. The rudder was locked irreversibly and had to be released by levering the rudder horn with a screwdriver. A second test, with the rudder cable reconnected, but slightly loose, and with other conditions the same, again led to a locked rudder. These tests showed that the design and condition of the stop bolt and rudder horn stop plate allowed the stop plate to over-travel the stop bolt and jam.
On 14 March 2000, Cessna notified TSB investigators that it is developing a new design for the rudder horn stop bolt to preclude the possibility of over-travel of the rudder. Cessna has notified the Federal Aviation Administration (FAA) Aircraft Certification Office that it is developing a Service Bulletin to offer the new configuration for all Cessna 150s and 152s produced after 1966. Transport Canada and the FAA are considering airworthiness actions.
The following Engineering Branch report was completed:
* LP 89/98 - Investigation of a Locked Rudder.
This report is available upon request from the Transportation Safety Board of Canada. Complete report here:
http://www.tsb.gc.ca/eng/rapports-reports/aviation/1998/a98q0114/a98q0114.asp
