Aircraft and Flight Details
A Grob G115E Tutor, registration G-BYVE, was conducting a training flight from RAF Wittering, Cambridgeshire on 24 August 2016. The aircraft was powered by a single Lycoming AEIO-360-B1F piston engine. The crew consisted of two persons; no passengers were on board. The commander held a military licence with 4,690 hours total flying experience, including 910 hours on type, and had flown 45 hours in the last 90 days and 13 hours in the last 28 days.
Circumstances
During a formation takeoff, at approximately 400 ft above ground level, a loud “thud” was heard followed by the onset of severe vibration. The aircraft was turned downwind immediately and a PAN was declared. Once sufficient runway was available to complete a safe landing, the pilot turned onto finals and executed a glide approach, resulting in a successful landing.
Examination Findings
Post-flight examination revealed that the anti-erosion sheath had separated from one of the propeller blades. As a precaution, the operator removed from service all propellers that had been overhauled by their UK subcontractor, which included the incident propeller. Specialist examination by the propeller manufacturer determined that a combination of three defects led to the loss of the anti-erosion sheath: insufficient adhesive between the blade and the sheath, excessive sanding of the glass fibre layers on the inner portion of the sheath, and the sheath not being cleaned totally before refitting to the blade. Examination of the remaining two blades of the incident propeller and all three blades of another propeller overhauled by the same UK subcontractor showed them to be free from these defects.
Investigation
The investigation was based on the Aircraft Accident Report Form submitted by the pilot. No other sources of information were cited.