EROPS and the Overwater Twin

EROPS has taken for its datum, the existing rules used by different countries for twin-engine operations based on ICAO Annex 6 – ‘the ninety minute rule’. This guideline limits twin-engine aircraft to routes where they are never more than 90 minutes at an all-engine speed from a suitable airport. To quote from the Boeing paper:

“Extended range is defined in the context of aviation rules and operational guidelines promulgated over 30 years ago. These rules focus on engines . . . and are based on the reliability of the piston engines in use i_n the late 1940s and the early 1950s. ”

The US adopted a more restrictive approach – their operating rule limited all two-engine aircraft to a time limitation of 6() minutes at a one-engine inoperative cruise speed from an adequate airport. (An adequate airport, incidentally, was defined as one which was acceptable as far as runway length and surface and with weather adequate to allow a safe landing with an inoperative engine/system. )

When Boeing first approached the FAA, scepticism was initially expressed at the idea of extending the 60 minute threshold. Boeing, as stated above, had been collecting data since the beginning of the 1980s and after producing evidence of airframes, systems and engines (often referred to as propulsion systems), the FAA expressed a willingness to objectively assess ongoing results. Actual fleet experience commenced after 1982.

The ‘transition years’ were from 1983 to 1985. Nations such as the US and UK, France, Canada, Israel, Australia and New Zealand consulted with each other; airworthiness authorities and airframe and. engine manufacturers exchanged complementary information. ICAO sponsored a study group for technical discussion of new regulations.

By the mid-1980s, most authorities had recognised that it was appropriate to extend the one-engine threshold provided defined requirements were met.

Normally an operator was required to accrue 250,000 hours of a particular airframe/engine combination (and all flight hours were to contribute, regardless of whether EROPS or not). Extended range 767s were being built with improved monitoring of avionics cooling, additional cargo fire suppression, four electric generators (one connected to each engine, one to the APU, and one to the hydraulic motor generator). The APU was able to be started in flight, even if cold soaked. These were some of the items in the minimum equipment list (MEL) stipulated by authorities. Allowable engine system shutdown/failure rates had been established, and standards for crew training and maintenance schedules were being adhered to.

The FAA granted approval to TWA to perform EROPS to a 120 minute threshold in May 1985, with transatlantic crossings. Others soon followed: American Airlines, El Al and Air Canada. The latter, incidentally, had been operating to the Caribbean at a 75 minute threshold since December 1983. EROPS soon extended to the Indian and Pacific Oceans and the Tasman Sea.

It is worth mentioning that from May 1985 to December 1986, over 13,000 767 EROPS flights were conducted. There were 25 reported events: seven turned back and eight diverted prior to the EROPS portion of the flight; six diverted during the EROPS phase and four continued to their destination. A success rate of 99. 838%.

In Australia the 90 minute rule was applied until 28 October 1985; aircraft built after this time would adhere to the 60 minute threshold at one-engine inoperative speed. This imposes a significant distance limitation. Consider the following: 767 . . :. about 700nm threshold at 90 minute rule; 400nm at 60 minute one-engine inoperative. Of course, Boeing’s 737-300s, 757s and 767s built after this date meet EROPS requirements. In 1985 Qantas took delivery of 767-200ER aircraft. It seemed logical that Qantas would order EROPS aircraft rather than convert Lip the track; Qantas, after all, has been operating extended range since . ‘day one’ (consider, for example, the Perth to Colombo Catalina ops in WWII).

“In principle we have approval from the DOTC to operate to 120 minutes”,. Captain Peter Flannery, Manager – 767s Qantas, told me. “With excellent trend monitoring, there’s provision for this time to be extended by 15% to 138 minutes. The biggest advantage is that it enables Qantas to plan for better equipped and thus safer, airports. This is particularly desirable, say, between Sydney and Manila, where adequate airports may have marginal ATC facilities and animals in the airport precincts – certainly not up to our main airport standards. ”

Qantas are operating 767 services out of every major Australian city; destinations include New Zealand, Noumea, New Guinea, Japan and Singapore.

On a flight from Noumea to Sydney, Capt Flannery demonstrated the options on the flight management computer, if our 767 had suddenly suffered a major problem; they were considerable. First, a selection of altitudes, power settings and speeds were available; some of the determining factors could be: smoke in the cabin, a fire in the cargo hold, icing and turbulence at a lower level. The FMC provided levels, speeds and times for diversions to Brisbane or Sydney. The point was that the avionics on modern EROPS aircraft assist the crew enormously if an incident did occur.

The Qantas 767s also have EICAS – engine and instrument crew alerting system; and AIDS-aircraft integrated data system. The latter facility. will monitor and record systems data until within range of an Arinc VHF station, where it will off load. The data finds its was back to company data storage, where it no doubt contributes to the ongoing EROPS evolution.

Capt Flannery is an advocate of EROPS and is confident that the imminent 767-300s with the new GE engines will meet their requirements without problems. (Operations will be restricted to trans-Tasman, Noumea and Port Moresby for six months due to the new airframe/engine mix. ) The 767-300s will actually. have 180 minute capability, a factor which could see 767s operating

transpacific in the near future. Ansett Airlines have also had EROPS involvement. The airline modified two of its 767s serving the Cook Islands. Ansett had taken delivery of their 767s in 1983.

“We would virtually be operating EROPS from Melbourne and Sydney to Perth every day if it wasn’t for Forrest”, Captain Jim Duff, line operations manager said. “In the unlikely event of that alternate becoming unavailable due to weather, then we would definitely be in an EROPS situation. Our 737-300s meet EROPS requirements, as will the Airbus A320, which achieved certification on 26 February 1988. ”

It is no secret that Boeing would like to see EROPS go to 180 minutes. When this does occur, virtually all of the world can be served by EROPS aircraft. With the enormous range of the 767- 300ER (eg Sydney to San Francisco), it appears that the only restriction will be on duty times and it is likely that multiple crews and horizontal rest facilities would ensue – no doubt creating the 767-400! It may be viable to inaugurate a route between Austral. ia and South America at last. The 180 minute limitation would also provide operators with the flexibility to avoid adverse winds and other weather.

The question does arise, of course – why EROPS?

Boeing list a number of reasons: EROPS aircraft connect secondary cities and provide initial route development to cities without international links; they offer a seasonal substitute for 747s; they can also alleviate stopovers and the inconvenience incurred. ·

”The 767 offers frequency”, Capt Flannery said. “We can now ask passengers what time they want to go rather than what day. ”

It would appear, then, that the question is not ‘Will there . be EROPS?’ – rather, it is ‘When will there be EROPS?’. It is fairly likely that interested parties will witness further developments later this year and into next year, with emphasis on the 180 minute proposal. Another era in aviation begins.