AOPA Australia has raised concerns that a gas plume coming from the proposed Tallawarra B power station near Wollongong could cause GA aircraft to stall.
In a letter addressed to Energy Australia Project Director Julian Turecek AOPA CEO Ben Morgan said that an aeronautical impact assessment conducted by Energy Australia did not correctly take into account the impact of the proposed open-cycle gas turbine (OCGT) plume on GA aircraft.
"The Critical Plume Velocity [CPV] used in this report has been calculated incorrectly and overlooks the role that vertical gusts play in safe flight conditions for general aviation aircraft within the circuit," Morgan said in the letter. "This is the most significant error in the report."
The Energy Australia assessment used a CPV of 6.1 m/s in its calculations, but AOPA says that measure failed to take into account the aircraft types likely to encounter the plume, the stage of flight the aircraft would be at when encountering the plume and the location of the plume itself.
"A plume vertical velocity of 6.2 m/s encountered by a Cessna 172N climbing out at best rate of climb speed and maximum take-off weight will push the aircraft wings to the critical angle-of-attack (AoA), causing the wings to loose lift and the aircraft to momentarily stop flying [stall]."
Morgan goes on to claim that a plume of 6.1 m/s would stall a Piper Archer II, but may cause smaller aircraft such as a Foxbat or a Jabiru to enter a spin.
AOPA has recommended that CASA should calculate the appropriate velocity and height given the types of aircraft likely to encounter the plume and the phase of flight the aircraft will be in at the time.
In August last year, CASA declined to approve a Danger Area around the site of the Tallawarra B power station site because it said the measure put forward by Energy Australia did not sufficiently mitigate the risk.
The site of Tallawarra B is on the western shore of Lake Illawarra within the circuit area of Shellharbour (Albion Park) Airport.