This article originally appeared on the P&WC Airtime Blog.
Airtime spoke with Yves Houde, PT6A Customer Manager at P&WC, to discover how the Ground Performance Check (GPC) process plays an important role for PT6A-powered aircraft.
A SIMPLE SOLUTION TO MONITOR AIRCRAFT ENGINE PERFORMANCE
PT6A engine operators can benefit from an occasional GPC to better understand a variety of engine performance parameters in real time. Operators can conduct the GPC themselves and plot the results on a GPC chart, which is typically found in the Airframe Maintenance Manual (AMM).
The performance curves on the GPC chart represent the characteristics of various engine parameters over a wide range of ambient pressures and temperatures. It is important to note these curves do not represent the limits of the parameters and are not to be used for acceptance or rejection of an engine in service.
“Although it’s not a required task of our Engine Maintenance Manuals, we recommend PT6A engine customers conduct a GPC on a regular basis to get an accurate, real-time picture of their engine’s operating performance,” says Yves.
From the GPC, customers can gain engine insights that trigger particular maintenance tasks so that engine performance events can be avoided all together.
WHAT TO LOOK FOR DURING A GROUND PERFORMANCE CHECK
“There are three primary engine performance values that should be evaluated and recorded during the GPC while the engine is running, after having set the engine torque for the day based on the outside air temperature and barometric pressure,” explains Yves. “These are Inter-Turbine Temperature or ITT, compressor speed – also known as NG and fuel flow.”
If these performance values are running close to the recommended thresholds or if a shift is observed from the last GPC, it is an indication that follow-up work should be conducted – work that might range from a simple redo of the GPC to a borescope inspection or a hot section inspection. All of these maintenance tasks can be completed on-wing thanks to the PT6A’s modular engine design.
In most instances, the recommended thresholds for the three performance values (which can differ from one PT6A engine model to another) and other related information can be found in the aircraft’s maintenance manual, though that does vary depending on the airframe original equipment manufacturer (OEM). Yves says a quick call to a P&WC Field Support Representative or the company’s CFirst response centre is a good way to quickly get accurate information.
ROUTINE GROUND PERFORMANCE CHECKS INCREASE AIRCRAFT ENGINE VALUE
He also urges customers to keep accurate records from their GPCs as together they form an ongoing narrative on the engine’s performance.
For customers looking to trade in their aircraft, we find having continuous GPC documentation on the engine helps support this transaction, because they have a clear reference point to the engine’s performance over time-since-new or time-since-overhaul.
While there is no set interval for conducting a GPC, Yves recommends it be done coinciding with regular fuel nozzle cleaning, which is typically every 300 to 400 hours.
Looking for more tips on engine maintenance? Airtime has you covered.