Beechcraft proposed AD

AOPA wish to alert all owners of Beechcraft aircraft, models E33, A36 and B55 to a control cable failure that occurred in an E 33 aircraft. CASA are proposing and AD that may affect their aircraft. AOPA are keeping a close watch on this development and have been in discussion with Mr. Roger Alder. Whilst we accept the need to inspect the control cable in question, we are endeavoring to arrive at an inspection program that address’s the safety concerns, but allows sufficient time for compliance.

“A Beech 33 Elevator cable failed during the control check immediately prior to take-off. The pilot had completed the prescribed daily / pre-flight inspection before operations commenced that day. The cable failed as the pilot was performing control checks at the holding point prior to take-off. The pilot decided to return to the apron to have it checked. The elevator cable was found to have failed (separated) where it runs between (over and under) the two closest pulleys in the elevator control circuit and to the lead weight, forward of the instrument panel, where the cable changes direction from horizontal to vertical. Extensive fraying was discovered in a second aircraft of the same type”.

CASA has received an initial report of an elevator cable failure in a Beech 33, and a separate case of extensive elevator cable fraying in the same location on the same cable in a Beech A36. Both aircraft were operating from the same airfield at the time.

Fortunately the Beech 33 Elevator cable failed during the control check prior to take-off. The pilot had completed the prescribed daily / pre-flight inspection before operations commenced that day. The cable failed as the pilot was performing control checks at the holding point prior to take-off. The pilot reported feeling something “funny” in the elevator controls and decided to return to the apron to have it checked. The cable was found to have failed (separated) where it runs between (over and under) the two closest pulleys in the elevator control circuit and to the lead weight, forward of the instrument panel, where the cable changes direction from horizontal to vertical.

The second aircraft, the Beech A36 was inspected at the owners request following the discovery of the failure of the Beech 33 cable. The elevator cable in the second aircraft was found to be extensively frayed in the same location as the Beech 33 cable.

Both aircraft are early model Beechcraft with the old-style elevator ‘single-pole’ control system (also similar to the early Beechcraft Baron) and maintained to CASA Schedule 5. Apparently the area of the cable system which suffered the failure can be very difficult to inspect properly using visual means alone, particularly while the cable is installed. It is strongly suggested that all owners of Beech aircraft replace all flight control cables which have been installed for 15 years or more, (Refer CASA AWB 27-1 Issue 2) and for all other cables, perform a close inspection of the entire flight control system cable run for wear and fatigue, particularly at the location identified in this report and check control cable rigging tension.

One inspection technique that has been suggested in this instance is to move the elevator control all the way through the full control movement while using some means of physical contact with the cable, such as a rag or card, to detect cable fraying. The suspect area is the inside (or pulley contact surface) of the cable where it runs between the two forward pulleys and to the lead bob weight. In this case, visual inspection alone is not considered adequate.

This is an initial report. The investigation is continuing.
Should you discover a defective cable or require any further details, please contact:

Roger Alder

Senior Engineer – Maintenance
Airworthiness & Engineering Branch
Standards Development & Future Technology
Civil Aviation Safety Authority of Australia
P: +61 (2) 6217 1374
F: +61 (2) 6217 1920
E: roger.alder@casa.gov.au
www.casa.gov.au