The pilot, who was of slight build, was tasked with conducting a regular public transport flight, with 6 passengers, from Gunnedah to Sydney (Kingsford Smith) airport. The aircraft, an Embraer EMB-820-C (licence built Piper PA31 Chieftain), had a valid maintenance release with no significant outstanding entries. Pre-flight preparation was normal and unrushed and an on-time departure was accomplished. The weather for the departure was fine with light wind.
Before initiating take-off from runway 11, the pilot, who was appropriately licensed, endorsed and base checked to fly the EMB-820-C aircraft, carried out engine run-ups and pre-take-off checks. The pre-take-off checks included selecting 15 degrees of flap and setting the elevator trim. The pilot's normal trim setting procedure was to wind the trim wheel all the way to the forward limit and then wind it back 5 to 6 complete turns. Consultation with industry pilots experienced on the aircraft type revealed that 3 to 4 turns was common. They indicated that pilots of lesser physical stature have found the aircraft type is easier to rotate with the elevator trim set to a nose-up position for take-off, however that would result in more re-trimming of the aircraft once airborne and during flap retraction. Low-wing aircraft have a tendency to pitch up slightly during flap retraction. Additionally, as an aircraft climbs out of ground effect, changed downwash over the tailplane produces a further pitch-up tendency.
The pilot reported that the take-off run and rotation appeared normal, however, as the flaps were retracted the elevator load increased. The pilot was only able to preserve a safe climb attitude by using both hands to maintain forward pressure on the control column. The pilot did not use the electric trim in normal day-to-day operations and did not consider using it to relieve the elevator load on that occasion. Believing the problem was either elevator trim or aircraft centre of gravity related, the pilot requested the passengers seated at the rear to move toward the front of the aircraft in order to lighten the load on the controls. A male passenger positioned himself in the unoccupied right control seat and, as the control forces were still high, the pilot requested that the passenger momentarily apply forward pressure on the control column. The pilot then took one hand from the controls to manually trim the aircraft and reduce the power.
The aircraft continued to Sydney without further incident and showed no abnormal handling characteristics on the subsequent sectors. A comprehensive inspection of the aircraft did not reveal any discrepancies with the elevator trim system and a review of the aircraft logbooks indicated no recent reported problems or disturbance of the trim system for rectification work. It was calculated that, at take-off, the aircraft weight was 39 Kg below the maximum take-off weight and the centre of gravity was slightly forward of the mid-point between the forward and aft limits.
Prior to the incident flight the pilot had positioned the aircraft to Gunnedah from Coonabarabran. The aircraft, which had no passengers or freight, was landed with full flap and in that configuration would have required almost full-back (nose-up) trim. Although not included in the after-landing checks of the operator's approved Piper Aircraft Corporation paper checklist, it was normal practise for most pilots to re-set the trim when clear of the runway. The Pilot's Operating Handbook expanded checklist recommended that course of action. The expanded checklist was used for training and as a supplement to normal and abnormal checklists. It was not meant to be referred to in flight.