With a range of up to 8,555 nautical miles (15,840km), the Boeing 777 is one of the most versatile long-range passenger aircraft in service today. Even so, passengers unfamiliar with twin-engine operations and safety standards may feel apprehensive about long-range flights should an engine be lost.
Can a Boeing 777 Fly on One Engine?
Let’s start by taking a look at whether the Triple Seven can fly on one engine in each of the phases of a flight.
Take-Off
Takeoff in any aircraft involves planning and thought behind every step of the process. Checklists abound and are followed rigidly, and pre-flight planning and inspections take place well before the engines are fired up, and continue on thereafter.
Usually, any major issue will be caught well before a pilot pushes in the throttle and starts off down a runway. Pilots will have completed a final takeoff briefing before entering the runway – deciding and verbally stating what will happen if any issue that could disrupt the safety of the flight takes place during takeoff.
This includes plans for what will happen if a problem is encountered while the aircraft is still on the ground, while it is off the ground but above the runway, above the ground and beyond the runway, and at various climb altitudes. During the takeoff roll, particularly in multi-engine aircraft, several designated speeds (V1, Vr, and V2), often referred to as “V-speeds,” represent critical moments that will be included in this briefing.
V1 is the designated speed by which pilots must decide whether to continue the takeoff or abort. In the 777, as with any other large turbofan jet, this is not a universally set speed but rather is calculated based on several factors including runway length and slope, takeoff obstacle clearance altitudes, outside temperature, atmospheric pressure, and the aircraft’s loaded weight at takeoff.
Generally speaking, V1 must be reached by a designated point on the runway; if V1 is not reached by that point, the pilots know something is not right and will abort the takeoff. Loss of an engine prior to this point would certainly affect where V1 was reached, and would almost definitely lead to an aborted takeoff before the plane ever left the ground.
Following Vr, the speed at which the aircraft’s nose is lifted into the air, V2 is essentially the takeoff speed. V2 is the minimum speed that must be maintained in order to climb safely in the event of an engine failure.
Although the pilots would most likely turn around and land as soon as safe and practical in the event of an engine failure, the 777 is capable of maintaining V2 on one engine should the other fail. The aircraft would have diminished performance – most notably at this stage would be the plane’s much lower rate of climb – but pilots can make adjustments to compensate.
A fully-loaded 777 may have some trouble remaining above required obstacle clearance altitudes (ROC), but it will normally have no trouble remaining above the lower minimum obstacle clearance altitudes (MOCA).
Cruise
Engine loss during cruise is, of course, an emergency situation, but is hardly a reason to panic. Boeing 777 variants are rated to fly as far as 330 minutes away from the nearest diversion airport in the event of an engine loss and are capable of perfectly safe, sustained flight on a single engine.
Most immediately, pilots will need to compensate for thrust imbalances. With one engine gone, the engine opposite the failed one will now cause the aircraft to yaw in the direction of the failed engine. In other words, the nose of the plane will want to continually move towards the failed engine rather than continue flight in a straight line. Pilots will compensate by applying appropriate rudder pressure in the direction of the live engine.
The second immediate issue that will likely need to be dealt with will be that of altitude management. The 777 often cruises well above 30,000 feet, but will become very difficult to control at those altitudes following the loss of an engine. Adjusting this will typically include an altitude change to around 20,000-25,000 feet; during descent, attempts may be made to restart the engine.
Landing
If an engine is lost during the final approach to landing, the crew may opt to fly a missed approach and fly a holding pattern or go around to buy some additional time to secure the engine, rebrief the approach, review and ensure their comfort with their engine-out landing checklists, and make other necessary adjustments.
If an engine was lost earlier on in the flight and the crew is landing the plane at a diversion airport, they will need to consider the weight of the aircraft. Because planes burn fuel over the course of their journeys, they become lighter the longer they fly. Many large aircraft like the 777 are unable to safely land at their fully loaded takeoff weight.
This means that, if an engine is lost early in the flight, the pilots may need to fly a holding pattern until enough fuel is burned to get the plane to a low enough weight to land or, in the event the crew needed to get the plane on the ground sooner, they could opt to dump fuel.
Once ready to make the approach, the biggest difference from normal will be the amount of rudder pressure required and the amount of throttle used, since the plane has half the thrust it normally does. Even so, the Boeing 777 is perfectly capable of flying a safe approach on one engine.
How Far Can a Boeing 777 Fly on One Engine?
As a twin-engine aircraft designed to regularly make trips spanning continents, the Boeing 777 is subject to Extended-range Twin-engine Operations Performance Standards, otherwise known as ETOPS. ETOPS are standards created by the International Civil Aviation Organization (ICAO) that govern elements of flights that take place beyond one hour from a diversion airport at one-engine-inoperative cruise speeds.
In effect, ETOPS regulations provide designations for how far away from the nearest diversion airport a twin-engine aircraft can fly. The original ETOPS regulations from 1985 allowed designated airlines to fly up to 120 minutes from the nearest diversion point.
The Boeing 777 was the first aircraft to receive greater than an ETOPS-120 rating, when it received ETOPS-180 in the 1990s, allowing for flight 180 minutes from the nearest diversion point. Today, 777-300ER, 777-200LR, 777-F, and 777-200ER models have up to ETOPS-330 designations, allowing for flight virtually anywhere in the world on a single engine.
Examples of Boeing 777s Flying on One Engine
Although examples of engine losses are rare, they do happen.
One of the most recent engine-out situations on a Boeing 777 occurred in February 2021, when a United Airlines flight from Denver to Honolulu experienced an engine fire and break-up shortly after takeoff. Although the captain reported a mayday, the crew was able to return safely to Denver.
Crews do not take engine issues lightly and often divert out of an abundance of caution even when an engine has not failed. A KLM flight from Amsterdam to Zanzibar, also in February 2021, experienced a bird strike shortly after takeoff. Although it did not lose an engine and continued flight until around 100 nm southeast of Athens, Greece, the flight ultimately returned to Amsterdam upon signs that something may be wrong.
Summary
The Boeing 777 is an extremely safe and modern long-range jet that is built to current multi-engine safety standards. While an engine loss is rare and hardly ideal, such incidents are not inherently a cause for serious concern – they are built to continue on and their crews are well-trained on what to do next.
As a 777 passenger, you can rest assured that engine-out situations in modern twin jets have almost exclusively happy endings.
