The Boeing 777 routinely starts both engines at once. But as the other answers say we usually don't have the pneumatic capacity to turn two at once. The B787 uses electricity for engine starting.
People Also Ask
Can a wide body airliner land with a full fuel tank? Yes! But it is safer to land an aircraft below its published MLW. Using the B777-200 as an example.
If all of an airplane's engines fail simultaneously, the pilot will perform an emergency landing. As the airplane descends and decelerates, the pilot will begin to search for a safe area to perform an emergency landing. Ideally, the pilot will land on a nearby landing.
Efficiency. The primary reason why Boeing opted for a twin-engine 777 was due to the unparalleled efficiency it offers. Boeing had already noted the use of the 767 on transatlantic operations after ETOPS certification in 1985, bringing down the last barrier for long-haul twinjet operations.
“The Boeing 777's unique combination of superior range, outstanding fuel efficiency and passenger-preferred comfort has created long-range success for carriers around the world. And the 777-300ER now gives operators a perfect opportunity to extend that success.
The most recent derivative of the GE90, the GE90-115B, is the sole powerplant for Boeing's longer-range 777-300ER and 777-200LR aircraft. The GE90-115B certified at 115,000 lbs. of thrust and has broken a number of aviation records.
The 777-8 is slightly smaller than the 777-300ER, and the 777-9 is slightly bigger. The main differences are in the design, technologies, and efficiencies. They are not things many passengers will necessarily note, but it's something the airlines will. The smaller of the 777Xs, the 777-8 is just under 70 meters long.
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.
Techincally, there is only one way for the aircraft to remain hanging motionless in the air: if weight and lift cancel each other out perfectly, and at the same time thrust and drag cancel each other out too. But this is incredibly rare. To stay in the air and sustain its flight, an aircraft needs to be moving forward.
Flying at a typical altitude of 36,000 feet (about seven miles), an aircraft that loses both engines will be able to travel for another 70 miles before reaching the ground.
In the event of an emergency requiring a return to the departure airport, the aircraft circles nearby in order to consume fuel to get down to within the maximum structural landing weight limit, or, if the situation demands, simply land overweight without delay.
CBS News reported that, based on the expert opinion of a former Boeing 777 captain, Flight 89 would have likely dumped 15,000–20,000 US gallons (12,000–17,000 imp gal; 57,000–76,000 L) of fuel. Shortly after completing the fuel dump, the aircraft landed safely.