Diversion
Diversion
Definition
DIVERSION (DVRSN)- Flights that are required to land at other than their original destination for reasons beyond the control of the pilot/company, e.g. periods of significant weather.
Source: US FAA JO 7110.65
Description
A diversion is a situation where the pilot decides to land the aircraft at a different aerodrome than originally planned. Diversions can be divided into three broad groups:
- Air turnbacks. These are situations where the aircraft returns to the departure aerodrome.
- En-route diversions. These are situations where the aircraft diverts to an alternate before reaching the vicinity of the planned destination aerodrome.
- Destination diversions. These are situations where the aircraft diverts to an alternate after reaching the vicinity of the planned aerodrome.
Diversions can happen for a number of reasons, e.g.:
- Adverse weather, e.g.
- thunderstorms (either at destination or en-route leading to excessive extention of the route)
- heavy rain/flooded runway at destination
- significant crosswind at destination
- Aerodrome closure due to e.g.
- maintenance works
- the flight arriving outside opeating hours (too early or too late)
- Emergency or abnormal situation at the destination, e.g.
- security issues
- accident with another aircraft leading to runway/aerodrome closure
- Emergency or abnormal situation on board, e.g.:
- System or component failure (e.g. engine, electrical, pressurization, hydraulic, etc.)
- Insufficient fuel
- Medical issues (affecting either a passenger or a crew member)
- Unruly passenger(s)
- Bomb threat/hijack
- Clearance issues. Examples of these include:
- the aircraft is not allowed to land at the destination aerodrome
- some en-route airspace that either prevents the aircraft from reaching its destination or circumventing it extends the flight route to the point where fuel is no longer sufficient to reach the destination.
- Military interception
Excluding some security-related situations (hijack/interception), the decision to divert is made by the pilot in command. In most cases the new destination is (one of) the alternate(s) specified in the flight plan but depending on the circumstances (e.g. if they are all unreachable or considered inappropriate) other suitable alternatives can be used. Before making the final decision the pilot usually gathers additional information by e.g. the operator or the ATS unit they are in contact with. The latter can provide valuable information and assistance such as:
- weather (current and forecast) at the alternate(s) or other suitable aerodromes
- providing additional options (aerodromes not included as alterantes in the flight plan but probably suitable for the particular situation).
- navigation assistance (e.g. headings or direct routing to appropriate waypoints), especially in case the diversion is to an aerodrome that has not been planned for.
- runway and navaid information (e.g. runway length, available approach types, etc.).
- forwarding information to other ATS units along the modified route as well as the destination aerodrome and coordination of entry and landing permissions.
A&I Examples
Air Turnback
On 21 July 2022, one minute after takeoff from Surabaya, an Airbus A320 first officer acting as pilot flying (PF) saw that the captain was “in a rigid position." A medically qualified passenger was identified but could not find signs of life. A ‘PAN’ was declared and a return to land requested but due to resuscitation attempts, it was over 40 minutes before a landing occurred. The captain was subsequently confirmed deceased. The captain’s most recent medical examination was found not to have included a sufficiently in-depth assessment of his ongoing vascular risk factors before renewal of his medical certification.
On 17 October 2023 a Boeing 737-800 passing FL130 after departing Manchester received a cabin pressurisation warning, and the crew recognised that both engine air bleeds were off. After correcting this, climb was continued without donning oxygen masks until an air conditioning pack fault occurred, which prompted the operator to request a return which was uneventful. The bleeds-off condition had arisen after maintenance and had then not been recognised at release to service or during crew preflight checks.
On 19 October 2022, an Embraer E175-200 had just departed Dublin when the first officer, who was acting as Pilot Flying, became incapacitated. The captain immediately took over all flying duties, requested assistance for the first officer from the cabin crew, and declared a MAYDAY. The aircraft then returned to land without further significant event although a bird strike occurred on approach. The 35-year-old first officer was medically assessed, and the conclusion was that he had “low blood pressure (and) a possible lack of water and food” which would have been exacerbated by the rising cabin altitude after departure.
On 20 February 2023, a Fokker 70 flight crew realised, late into descent, that the landing altitude for their destination, Port Moresby, had not been set. With insufficient time to eliminate the cabin pressure differential automatically, they attempted to use manual control. When it became clear this had not worked, a go-around was initiated. When the cabin pressure differential then rose rapidly to 6 psi, multiple passenger ear/nose/throat injuries resulted, some serious. Another abnormal procedure was then actioned, and this resolved the situation and the aircraft was able to land.
On 20 December 2012, a PW4168A-engined Airbus A330-200 was climbing through FL220 after departing Phuket, Thailand, at night when sudden uncontained left engine failure occurred. Engine shutdown and initiation of a return was followed by loss of the green and then blue hydraulic systems. Shortly after this, a relatively uneventful landing followed with only minor damage but “without pilot assessment or knowledge of the safety margin." As the findings of the investigation raised still-relevant concerns about the way this multiple-failure scenario was handled, it was felt useful to publish the 148-page final report eleven years later.
En-route diversion
On 5 December 2019, the first officer of a Cessna 208 on a scheduled Indonesian domestic passenger flight close to Timor-Leste became physically ill during normal unpressurised cruise at 10,000 feet during conversation about a family health issue. When he briefly lost consciousness, the captain declared a MAYDAY and diverted to Dili. The first officer recovered and when hospital checks were passed, the flight to the intended destination was completed. An in-depth medical investigation found no evidence of physical illness and concluded that unmanaged emotional stress had led to hyperventilation followed by a temporary incapacitation.
On 23 July 2024, an ATR 42-600 was en route at FL180 when a contained failure of the left engine occurred. Despite a successful engine shutdown, fire occurred within the engine due to a fuel leak which may have been caused by a fuel line loosened when the engine failure happened. Both left engine fire bottles were required to extinguish the fire. With a MAYDAY declared, diversion to the nearest suitable airport, Aberdeen, was made. The engine failure resulted from undetected damage to its number six bearing which resulted in the high-pressure turbine no longer being correctly located.
On 17 February 2024, an Airbus A321 captain was initially unable to re-enter the flight deck after a short absence in cruise. On succeeding, he discovered that the first officer had become incapacitated with what ICAO classifies as a ‘seizure disorder,’ which was subsequently found to have occurred almost immediately after the captain had left. Once back on the flight deck, an emergency was declared with immediate diversion to Madrid Barajas where the first officer was hospitalised. A safety recommendation to consider further assessment of the risks of one pilot being alone on a secured flight deck was made.
On 20 October 2020, the crew of a Sikorsky S92A en route overwater to an offshore oilfield southwest of Stavanger received an engine 1 fire warning. They responded by shutting down the engine, deploying both fire extinguishing bottles, and eventually declaring a MAYDAY without taking all recommended steps to confirm an actual fire existed. They were aware that false engine fire warnings on this helicopter type had become a fairly regular occurrence, and when the warning persisted, they restarted the engine which ran normally. The flight was completed and made an uneventful landing on a platform close to the originally planned destination.
On 22 January 2022, an Airbus A320 departing the uncontrolled airport at Hayden, Colorado, announced its intended runway 10 takeoff despite calls from a Beech King Air 350 that it was inbound to reciprocal runway 28. When the A320 crew subsequently announced they were commencing takeoff from 10, the King Air Pilot responded by asking if the A320 was intending a quick turnout. Almost immediately after confirmation, the A320 captain rotated 24 knots before the correct speed with a resulting tail strike. Once airborne, an evasive right turn was commenced with the reciprocal-direction King Air just over 2 nm away.
Destination diversion
On 21 December 2023 a Boeing 787-8 crew inbound to Manchester on a day of significant weather-related flight disruption over northern England decided to divert to their nominated alternate East Midlands. When a landing there was denied, the flight proceeded to the nearest available alternate, Birmingham. After a windshear-related missed approach and subsequent low fuel MAYDAY declaration, a second approach led to a successful landing but with significant use of final reserve fuel. The operators of East Midlands and Birmingham airports subsequently revised their procedures for determining and communicating capacity for diversions and prioritising flights declaring low-fuel emergencies.
On 17 October 2022, an Airbus A320neo was unable to make an approach at either its intended destination of Riohacha or its designated alternate after those airports were both closed because of convective weather which developed over a significant part of Northern Columbia. A MAYDAY was declared due to low fuel and only 282 kg remained after the eventual landing at Santa Marta. Decision-making by both the aircraft operator and the flight crew and a lack of reliable communication between them was deemed contributory to what came very close to becoming a hull loss accident.
On 12 August 2024, an ATR 72-500 making a Category 1 ILS approach to Guernsey with thick fog breached an approach ban by continuing its descent below the applicable minimum altitude of 1,000 feet agl. The aircraft then continued below what would have been the applicable 200 feet agl Decision Altitude without visual reference. At around 70 feet agl, a go-around was called but not correctly commenced, and the aircraft passed close to an unseen mast north of the runway before it eventually climbed. In the absence of any visibility improvement, a diversion to Southampton then followed.
On 17 January 2023, an ATR 72-200 in the final stages of a CAT 2 ILS night approach to East Midlands experienced an electrical malfunction which disabled one set of primary flight instruments and triggered multiple system status indication failures. These included false system warnings and radio communications problems. The approach was discontinued, a MAYDAY declared and a successful manually flown diversion to Birmingham was made. The cause of the electrical malfunction was found to be a wiring defect, which was considered to have probably been caused by incorrect use of mechanical wire-stripping tools during third party maintenance.
On 21 December 2023, a Boeing 737-800 experienced a flap load protection response to turbulence during a night go-around at Billund, which locked the flaps in a mid-range position. A diversion to Copenhagen was commenced, but when it became clear that the fault would result in landing with slightly below minimum reserve fuel, a MAYDAY was declared. The flight was completed without further event. It was concluded that flap system locking had probably resulted from the crew’s manual selection of 15° flap just as the flap load relief system was responding, as designed, to a turbulence-caused flap overspeed condition.
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