It had been pointed out to the pilot, by another pilot on a previous flight, that the undercarriage retraction
cycle was slow and he resolved to have this checked on the approaching 100 hourly inspection. The purpose
of this flight was to position the aircraft for this inspection. After a normal flight from Adelaide the pilot
selected undercarriage "Down" on a practice ILS approach to Essendon and noticed that cockpit indications
for the port undercarriage continued to show "Up". He advised the Tower of the problem and on a subsequent
pass over the Tower, ground observers confirmed that the port wheel was still retracted. Since he had plenty
of fuel on board, the pilot spent about an hour attempting to lower the undercarriage, using the normal and
emergency lowering methods. All systems operated normally, except for the port gear, which remained
retracted. Acting upon instructions from engineers on the ground, the passenger removed a panel from the
hydraulic system and tapped the port gear jack with the rubber end of a crash axe, but to no avail. The pilot
decided to make a wheels up landing on the grass parallel to runway 08, and outside the northern boundary
of the flight strip. Although the aircraft landed smoothly the under side of the fuselage was considerably
damaged.
Subsequent examination of the port undercarriage jack showed that the piston 'O' ring was badly chipped, but
the reason for this could not be established. A fragment from the chipped 'O' ring had blocked the orifice of
the jack brake valve, preventing operation'of the jack to lower the port gear. The unit containing the
defective 'O' ring was required to be overhauled at periods not in excess of 4 years, but examination of the
aircraft servicing records showed that it had not been overhauled since 14.2.1967.