What happened
On 7 July 2005, a Piper PA34-200T Seneca II, registration ZK-MSL, performed an intentional wheels-up landing at Napier Aerodrome. The flight, a scheduled freight service, was operating between Palmerston North and Napier. During the approach to Wairoa Aerodrome, the pilot noticed the landing gear unsafe warning light was illuminated. Despite attempting both normal and emergency extension procedures, the nose landing gear failed to deploy.
After consulting with the chief pilot and attempting various maneuvers to dislodge the gear, the pilot decided to return to Napier. To mitigate risk, the pilot opted for a landing on a grass runway with the gear retracted. The aircraft touched down approximately 50 meters after the start of the runway. While the two occupants escaped without injury, the landing caused substantial damage to the propellers and minor damage to the fuselage.
The investigation
The investigation focused on why the nose gear failed to extend despite the use of emergency procedures. Investigators examined the aircraft's maintenance history and discovered that a centering spring attachment bolt had been installed incorrectly during maintenance performed nine weeks prior. This error was committed by a trainee engineer under the supervision of a licensed engineer.
Further examination of the nose baggage compartment revealed that the compartment was heavily loaded with freight. The weight of the cargo, combined with potential lack of rigidity in the nose cone, caused structural distortion. This distortion caused the improperly installed bolt to jam against the gear door assembly, physically preventing the gear from extending.
Findings
- The nose landing gear failed to extend because the nose gear doors were obstructed by a centering spring attachment bolt that had been incorrectly installed.
- The installation error occurred during maintenance work performed by a trainee engineer.
- Excessive weight in the nose baggage compartment and possible nose cone distortion exacerbated the binding of the bolt.
- The absence of a required caution placard on the nose gear strut meant there was no visual warning to alert engineers to the improper installation.
- The aircraft was released to service in an un-airworthy state due to the faulty maintenance.
Safety action
Following the incident, the maintenance provider implemented new internal procedures and conducted staff training sessions focused on organizational failure prevention. The Director of Civil Aviation also took steps to ensure Seneca operators complied with airworthiness directives regarding the nose gear housing placard.