Air Canada flight AC008 on July 29th, 2019 returned to Hong Kong following an aborted flight to Vancouver, Canada. The exhaust gas temperature (EGT) was reading high in one engine. The crew were notified that debris had been found on the runway following take off. As such, the Captain decided to return to the point of origin.
Report of engine problems
The Aviation Herald reported on August 10th that an Air Canada Boeing 777-333ER, registration C-FIVW, with 442 passengers on board together with 17 crew returned back to Hong Kong’s Chep Lak Airport following an apparent engine malfunction. The flight in question was Air Canada’s AC008 from Hong Kong to Vancouver, British Columbia, Canada.
The report says that as the flight was departing on runway 07R, the crew heard a popping sound from one of the engines and then observed a brief EGT exceedance indication on the right-hand engine (GE90).
Progress of the flight
The flight record shows that the aircraft continued to climb and was en route at FL300 about 515nm (955 km) from Hong Kong, Northeast of Chilung on the Northern tip of Taiwan, when the crew decided to return to the airport.
The aircraft maintained FL300 for the return and landed safely back on Hong Kong’s runway 07L at 10:29 pm local time, exactly 3 hours 20 minutes after departure. We are all aware that flying is the safest form of transport but incidents do happen.
AC008 returned because of a small malfunction. Similarly, on August 11th, 2019, a Qatar Airways 777 returned to base when a hole developed in its engine cowling: the aircraft landed safely and no one was injured.
Return to Hong Kong
Although at the time of writing, no definite link has been made to this flight, the Canadian TSB reported the tower advised the crew that debris was found on the departure runway. Nevertheless, that information and the EGT exceedance seems to have been instrumental in leading the crew to consult with maintenance then deciding to return back to Hong Kong. It can never be good to have to turn round; but just imagine this, you fall asleep, your plane lands and everyone gets off, except you!
What is EGT exceedance?
For an understanding of the term EGT and its exceedance, let’s learn from Arnaud BONNET, Engine Performance Manager in his article “Avoiding high speed rejected takeoffs due to EGT exceedance limits“.
EGT stands for Exhaust Gas Temperature and gives us some idea of the health of an engine. Specifically, it tells us about the health of the compressors and sensors. They set what they call the red line limit of the EGT Margin for an engine by assuming what it should be in a full power takeoff, without ambient temperature extremes and assuming a take off at sea level.
The EGT margin is one of many indicators that are used to detect shifts in performance for each engine, which can indicate the need for inspections and/or maintenance.
What the EGT Margin can also help pilots and engineers to understand is the effect of the accumulation of dust/dirt ingestion on an engine. Moreover, dust/dirt accumulation on fan blades/compressor airfoils together with other elements of wear and tear also take their toll on all engines and even a momentary EGT exceedance can be expected in an aircraft of the age of C-FIVW: just over six years.
The good news is that this event was minor and redeemable, which is a better situation than the possibility of something worse: falsifying documents can never be a good thing.
The final outcome?
The aircraft is said to have sustained minor damage and a maintenance investigation has been undertaken. Aircraft C-FIVW was ferried from Hong Kong to Toronto on Aug 4th.