Engines Turn Or Passengers Swim

The national geographic channel has a programme "Air Crash Investigation" that recaps and investigates air disasters and other mishaps. I happened to see the one regarding an Airbus A330 AirTransat north atlantic crossing that had to make an emergency landing in the Azores islands, Portugal. This episode was titled "Flying on Empty". The ultra-modern fly-by-wire Airtransat Airbus A-330 flight 236 with 306 passengers on board departed Toronto, Canada enroute to Lisbon, Portugal at around 8pm in August 2001. The first half of the journey was incident free. Trouble began then, when the co-pilot noticed some oil pressure problems on his panel and also saw fuel imbalance between the two fuel tanks supplying fuel to the engines on the left and right wings. Going through the Airbus manual, the pilots took a decision to open up the cross-feed valve that balances fuel between the tanks. The oil pressure and fuel imbalance problem was because of a fuel leak in the right wing and the balancing of fuel meant that fuel from the left wing was also wasted on leaking right wing. Soon the aircraft was flying with the engines shut off because of empty fuel tanks. The problem with high-tech fly-by-wire mechanisms is that controlling the aircraft requires power and and without engines the electrical generators on board don't function. Airbus aircrafts do have emergency ram air turbines to supply power but the supply doesn't include the main flaps and the brakes. Luckily for everyone aboard this flight the Azores islands were within gliding range for the aircraft to attempt a landing. Though the landing was not smooth, there were no fatalities except for 10 injured passengers. Investigations pointed out that AirTransat engineers had replaced a faulty bracket on the right wing that had seared off the supply pipe to the right engine thus dumping 37000 gallons of aviation fuel into the Atlantic Ocean.

This put a question in my mind. What would have happened if the Azores Islands were not within landing distance of the aircraft? Would it mean that all 306 passengers would meet a watery grave? Were there any regulations by Aviation authorities to ensure safe flying? My curiosity led to the term ETOPS (Extended-range Twin-engine Operation Performance Standards) or jokingly called "Engines turn or passengers swim". Historically, aircrafts had piston based engines that were not very reliable. The FAA introduced regulations that restricted twin engined aircrafts to stay within 60 minutes flying time to a nearest airport to handle engine failure emergencies. The distance from an airport corresponding to the 60 minutes flying time may vary depending on the speed of the aircraft with one engine inoperative. But this meant that crossing the Atlantic would take longer and weather at airports in the flight path became critical for deciding the trans-atlantic crossing.
But the development and deployment of the turbine engine (jet engine) changed the equation. These engines not only provided more thrust but also were much more reliable than the piston based ones. The 3 engined Boeing 727 was the first aircraft that was waived the 60 minute rule when flying across oceans. This led to the development of tri-engine aircrafts such as the Lockheed TriStar and the McDonnell Douglas DC-10. The Boeing 747 was also one of the effects of relaxing the 60-minute rule for aircrafts propelled by more than 2 engines. However, outside the US the diversion time was 90-minutes and Airbus had come up with the Airbus A300, a twin engine wide body airliner that was smaller than the DC-10 and the Tristar, but at the same time was very efficient and cheaper to operate. The A300 also showed amazingly low failure rates for a twin-engine aircraft and was quite a big success outside the US. The response to the A300 from Boeing were the 757s and the 767s.

The success and superior technical design of these twin-engine aircrafts (A300, Boeing 757 and 767) and the active lobbying from the aircraft industry prompted the FAA to introduce ETOPS. The initial version of ETOPS allowed properly designed twin-engine aircrafts a diversion time of 120 minutes and was called ETOPS-120. Soon ETOPS-180 was introduced that certified aircrafts to have a 180-minute diversion time after subjecting them to stringent technical tests. Many twin-engined aircrafts like the A300, A310, A320, A330 series from Airbus and some 737s, 757s and 767s from Boeing were ETOPS certified. ETOPS-180 allowed 95% of the earth's surface to be covered by these flights. The introduction of ETOPS meant that production of tri-engined aircrafts (DC-10 and Tristar) were abandoned and production of 4 engined aircrafts like the 747s were scaled down. The JAA (Joint Aviation Authority) and the ICAO (International Civil Aviation Organization) adopted ETOPS for flights across the globe. To accomodate for bad weather conditions and volcanic activities in diversion airports (snow in Greenland or volcanoes in the Aleutians), a 15% extension was provided to the ETOPS-180 and ETOPS-120 regulations, introducing ETOPS-138 and ETOPS-207. The Boeing 777 is the only aircraft allowed to operate under ETOPS-207, if and only if the diversion airports are closed because of adverse operating conditions.

Private Jets are exempted from ETOPS within the FAAs jurisdiction, but they are subjected to ETOPS-120 in JAAs jurisdiction. In the southern hemisphere, twin jets are still off-limits on several routes because of ETOPS regulations. I found this ETOPS FAQ which could be of interest to the readers of this blog.

share this: facebook