CASA today has said it will investigate Australian-registered Bristell and Roko NG4 and NG5 aircraft after a UK association found that an error in the Pilot Operating Handbook could cause the aircraft to be loaded aft of the centre of gravity (CoG).
The UK Light Aircraft Association (LAA) issued an Airworthiness Alert in late July stating that a weight check on a Bristell NG5 in the UK determined the pilot and passenger moment arm was up to 150 mm further after than the manufacturers indicated.
"The POH defines this moment as 600 mm aft of the datum where the true figure appears to lie between 700 and 750 mm aft of the datum," the LAA alert says.
"The consequence of this further rearward location of the pilot and passenger is that the loaded centre of gravity of the aircraft will be further aft than previously calculated. Pilots using the 600 mm pilot moment arm in their pre-flight centre of gravity calculations might therefore inadvertently fly the aircraft with the centre of gravity outside of the aft [CoG] limit."
In addition, the Irish Aviation Authority has contacted owners of Bristell NG4 aircraft recommending their aircraft be weighed and checked as part of an ongoing fatal accident investigation.
CASA Executive Manager – Stakeholder Engagement Division Rob Walker said in a letter dated today that the regulator would evaluate the ramifications for Australian owners of both NG4 and NG5 aircraft.
"CASA is presently working through any implications of the above material and has expedited a thorough review of the information, including taking steps to seek confirmation from the manufacturer in relation to the accuracy of the pilot and passenger moment arm measurements as published in all Aircraft Operating Instructions [AOI] for Bristell aircraft currently operating in Australia."
Walker also states that Australian aircraft are most likely affected and that checks showed the POH of seven aircraft had the moment listed as 600 mm aft of the datum.
"Until CASA can conclusively determine the extent to which these aircraft operating in Australia are affected by this issue, CASA recommends that before any further flight of the aircraft owners confirm with the manufacturer the accuracy of the data as published in the AOI for the aircraft."
Bristell LSAs have been at the centre of a stall/spin controversy that led to CASA banning stalls in the type in early July. BRM Aero has hotly contested CASA's actions and has taken their concerns directly to Deputy Prime Minister Michael McCormack.