Safety Advisory Notice
To Beechcraft Baron operators
Beechcraft Baron heater fuel supply line inspection
The ATSB is encouraging Baron operators to inspect the heater fuel supply line and nearby wiring in the aircraft cockpit to reduce the risk of an in-flight fire.
At approximately 0835 on the morning of 16 April 2022, the pilot of a Beechcraft B58 Baron registered VH-NPT commenced an approach to Runway 12 at the East Kimberley Regional Airport near Kununurra. Upon selection of the landing gear to the down position the pilot reported multiple unusual indications, the gear failed to extend and smoke started to emerge from forward of the pilots side circuit breaker panel. By the time the pilot had declared a PAN, flame was emerging from the same location as the smoke. The pilot expended the aircraft’s fire extinguisher but the fire returned. Smoke and flame continued to effect the pilot until the aircraft collided with terrain where it was consumed by a significant post impact fire. The pilot sustained serious injuries and the single passenger onboard was fatally injured.
During the initial phase of the investigation the ATSB identified a similar occurrence that had been investigated in 2014 (AO-2014-040). The investigation of the in-flight cockpit fire found that electrical wiring had chaffed through the heater fuel supply line causing it to arc and burn a hole in the fuel line. This provided an ignition source and accelerant for the fire.
Why did it happen
Both the heater fuel line and the aircraft wiring of NPT were consumed by the post impact fire, and an examination was not possible. However, the location, initiation and severity of the fire is similar to the incident detailed in AO‑2014‑040. As such, while the specific circumstances of the fire initiation and acceleration remain under investigation, in the interest of transport safety, the ATSB has issued this safety advisory notice.
In response to the advanced release of this ATSB SAN the manufacturer advised that there is a potential for chafing of wiring across several Beechcraft models including the Baron. Model Communiqué 116 references wire chafing reports in the Beechcraft Bonanza but the communiqué states that the protection of wires from chafing damage is applicable to all Beechcraft models.
Safety advisory notice
AO-2022-026-SAN-001: The ATSB encourages operators of Beechcraft Baron aircraft to conduct a detailed inspection of the heater fuel supply line and wiring in its vicinity. The examination should focus specifically on the area below the pilot’s circuit breaker panel and areas forward of this under the instrument panel. Any identified issues should be reported to CASA (via the defect reporting system) and the manufacturer.
The ATSB encourages Baron operators to review the Electrical Wire Chafing Protection section in Model Communiqué 116 (See attachment A) put out by Beechcraft in June of 2008, which is applicable to all Beechcraft models.
The ATSB further encourages operators to review the anti-chafing provisions within the relevant aircraft maintenance manual (see 20-04-00-001 – Electrical Wiring – Description and Operation) to ensure serviceability of anti-chafing materials and replace or fit, as necessary. Specific consideration should be given to wiring in the vicinity of lines carrying flammable liquids.
The ATSB notes similarities in several Beechcraft models, that utilise fuel lines running through the cockpit. While a review of ATSB data does not support the broadening of the SAN to include other aircraft models, chafe protection should be applied to wiring as per the manufacturers' requirements and particular care should be taken when wiring is in the proximity of lines carrying flammable liquids.
Area of concern in an exemplar Baron B58 showing the location of the fuel line and wiring looms. Inspection should encompass any areas along the fuel line where it may contact wiring looms.
Read more about this ATSB investigation: Investigation: AO-2022-026 - Collision with terrain involving Beechcraft Baron 58, VH-NPT, near Kununurra Airport, Western Australia, 16 April 2022 (atsb.gov.au)