Years ago, piston engines were undependable. Because of this, twin-engine aircraft were required to fly in range of a suitable airport for landing. In 1953, the FAA imposed what is known as the “60-minute rule” on two- and three-engine airplanes, disallowing them to fly more than 60 minutes outside the closest airport.
For example, if an aircraft is certified for 180 minutes, it is permitted to fly any route not more than 180 minutes' single-engine flying time to the nearest suitable airport. The following ratings are awarded under current regulations according to the capability of the airliner: ETOPS-75.
In 1988, it was again extended to a 180-minute maximum. Today, this has increased to a 240-minute ETOPS rule, but it is only approved in certain circumstances. All aircraft must be ETOPS certified and approved by the FAA first.
One Engine Down
In fact, airliners can fly quite well on just one. The Boeing 777 is certified to fly up to five and a half hours with one engine out.
The Federal Aviation Administration (FAA) may authorize operations over a route that contains a point farther than 180 minutes flying time from an adequate airport at an approved one-engine inoperative cruise speed under standard conditions in still air.
For larger aircraft, typically people use some form of the 3/6 Rule: 3 times the altitude (in thousands of feet) you have to lose is the distance back to start the descent; 6 times your groundspeed is your descent rate.
Many pilots refer to this as the 1-2-3 rule: Plus or minus 1 hour from arrival, ceilings at least 2,000 feet and visibility at least 3 statute miles.
While it's very clear that a 747 cannot fly properly with the failure of three engines, we can see that a single functioning engine would at least extend the aircraft's distance and prolong its time in the air.
For example, with a glide ratio of 15:1, a Boeing 747-200 can glide for 150 kilometres (93 mi; 81 nmi) from a cruising altitude of 10,000 metres (33,000 ft).
The 747-8 has ETOPS 330. The 787 has ETOPS 330. The A350 has ETOPS 370.
Boeing's Converted Freighters: 20 More Years of Life
2015 to fly beyond 180 minutes from an en-route alternate airport, the 747-8's design is approved to conduct 330-minute ETOPS missions. These missions allow operators to fly long-distances more directly on virtually any worldwide city pair routing.
A twinjet or twin-engine jet is a jet aircraft powered by two engines. A twinjet is able to fly well enough to land with a single working engine, making it safer than a single-engine aircraft in the event of failure of an engine. Fuel efficiency of a twinjet is better than that of aircraft with more engines.
While flights have a scheduled departure time, there is an unwritten final-boarding rule. The gate agent will often close the door to the plane 10 minutes before departure, which, depending on what side of the door you're on, can either mean a huge sigh of relief or a delayed or even ruined trip.
The Genie 120-minute rule says that you can make a new reservation at most 2 hours from when you made the last one, and this countdown timer doesn't change if you modify the reservation.
For domestic flights most carriers require you to be at the departure gate between 10 minutes and 30 minutes before scheduled departure, but some deadlines can be an hour or longer.
What happens if all engines fail in the air? If both engines fail, the aircraft will fly and glide quite happily. Modern passenger jets can glide with a ratio of around 1:10, so for every 1000 feet lost, the aircraft will fly 10,000 feet forward.
Without engine thrust, the 747 had a glide ratio of 15:1, meaning it can glide forward 15 kilometres for every kilometre it drops.
Built in 1967 to produce the mammoth jet, it remains the world's largest manufacturing plant according to Boeing. But after five decades, customer demand for the 747 eroded as Boeing and Airbus (AIR.PA) developed more fuel efficient two-engine widebody planes.
These four engines' combined thrust equates to around 1,427.24 kN (320,840 lbf), which powers the aircraft to lift it into the sky. To maintain level flight with a single engine, its thrust of 356.81 kN (80,210 lbf) would need to produce sufficient power to maintain a cruise speed of Mach 0.85 (903 km/h; 488 knots).
From the mid-1990s, twin-engine aircraft such as the Boeing 777 and Airbus A330 offered the same payload, the same range and lower operating cost than the triples, and that was the end of the road for the triple-engine giants as passenger aircraft.
AMARG: The World's Biggest Boneyard. On average, an aircraft is operable for about 30 years before it has to be retired. A Boeing 747 can endure about 35,000 pressurization cycles and flights—roughly 135,000 to 165,000 flight hours—before metal fatigue sets in. 747s are retired after approximately 27 years of service.
The 80:20 rule means airlines need to use their take-off slots at least 80% of the time in order to retain them. A "justified non-use provision" will be retained to prevent airlines flying ghost flights.
Applying this 1 percent rule would result in an airline pilot being denied a medical certificate if their risk of a medical incapacitation (e.g. heart attack, convulsion, stroke, faint etc) was determined as being greater than 1% during the year.
Instruments and Equipment: Rule 57 of Aircraft Rules, 1937 and Civil Aviation Requirements Section 2 - Airworthiness Series 'I' Part II and Series 'R' Part I- Provides for minimum instruments and equipment including Communication and Navigation equipment which are to be installed on aircraft depending on their ...