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.:

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 20 February 2021, a Boeing 777-200 climbing through 12,500 feet experienced a sudden right engine failure and fire shortly after thrust had been increased before entering airspace where moderate turbulence was expected. Despite actioning the corresponding drills, the fire did not go out until shortly before landing back at Denver. Engine debris fell to the ground over a wide area, fortuitously with only damage and no injuries. The failure was found to have been initiated by the fatigue failure of a single fan blade after required routine inspections had failed to find early-stage evidence of such a risk.

On 7 April 2022, a Boeing 757-200F returning to San Jose after a left side hydraulics failure and MAYDAY declaration suddenly veered off the right hand side of the landing runway there during deceleration and passage over uneven ground led to landing gear collapse and significant fuselage structural damage. This runway excursion immediately followed simultaneous advancement of both thrust levers after their prior asymmetric movement earlier in the landing roll and resulted in high left thrust concurrent with idle thrust on the right. With no airworthiness aspect identified, the excursion was attributed to unintended thrust lever selection by the crew.

On 22 March 2021, the pilots of a Boeing 747-8F which had just reached its initial cruise level after departing Dubai observed smoke and sparks coming from the window heating system and declared a PAN advising their intention to dump fuel and return to Dubai. With the faulty system switched off, this was accomplished without further event. It was found that the cause of the system malfunction was a design-related vulnerability with a history of recurrence which had not been adequately addressed by the aircraft manufacturer and the FAA as safety regulator following relevant NTSB Safety Recommendations made in 2007.

On 2 February 2016, an Airbus A321 Boeing 757-200F in the climb after departing from Mogadishu had just passed FL100 when an explosion occurred inside the passenger cabin. This led to significant structural damage to a small area of the fuselage, which caused cabin depressurisation, the ejection of one passenger, and led to three others being seriously injured. The damaged aircraft was recovered to Mogadishu without any further consequences, and the explosion was found to have been intentionally caused by the ejected male passenger. A series of Safety Recommendations were issued, aimed at improving security screening of passengers boarding flights from Mogadishu.

On 5 January 2024, a Boeing 737-9 which had just departed Portland was climbing through 14,800 feet when there was a loud bang followed by a rapid decompression. The cause - the loss of a fuselage plug fitted at an unused door location - was immediately obvious. An emergency was declared and a landing back at Portland was made after a total of twenty minutes airborne. The Investigation is continuing but has found that the fuselage plug involved was installed without being properly secured and noted that the aircraft had only recently been delivered new to the operator.

En-route diversion

On 17 January 2022, about 30 minutes after takeoff from Fort-de-France, Martinique, on an ETOPS flight, an Airbus A330-900 was approaching its initial cruise altitude when the apparently unconscious Captain appeared initially unresponsive. On being more aggressively roused, he seemed normal and a doctor on board initially assessed him as fit to continue. However, about two hours into the flight his condition subsequently deteriorated and the First Officer called the Chief Purser to take his seat to assist. A PAN, later upgraded to a MAYDAY, was declared and a diversion was made to Lajes where the Captain was hospitalised.

On 8 June 2016, a Boeing 737-800 en-route to Seville had already reverted to alternate automatic pressurisation control when this also failed. Manual system control was attempted but was unsuccessful so an emergency descent followed by diversion to Toulouse was then completed without further event. A similar pressurisation control fault had occurred earlier that day but had not been properly dealt with by an appropriately qualified engineer. Both system controllers were showing faults and were replaced as were a ruptured flexible hose and a series of malfunctioning drain valves. More reliable controllers and routine checking of system performance were recommended.

On 31 October 2021, a ‘Fuel Imbalance’ message occurred on a Boeing 787-9 soon after departing Bangkok at night but attempted fuel transfer was unsuccessful. A ‘Fuel Disagree’ message subsequently appeared and use of available system checklists indicated that there was a fuel leak from the left engine or tank. Left engine shutdown was therefore accomplished and a MAYDAY diversion to an overweight landing at Goa followed. The Investigation determined that the leak was actually from the right side fuel tank and attributed crew misdiagnosis to inadequate fuel system malfunction checklists and deficient crew guidance and training on fault diagnosis.

On 25 February 2015, a Boeing 737-800 encountered severe clear air turbulence as it crossed the Pyrenees northbound at FL 380. Two of the four cabin crew sustained serious injuries and it was decided to divert to Bordeaux where the flight arrived 35 minutes later. The turbulence and its consequences were attributed to the flight’s lateral and vertical closeness to a correctly forecast opposite-direction jet stream core and specifically to allowing cabin service to commence despite being near the boundary associated with severe turbulence following a negative ATC response when asked whether other flights had reported severe turbulence.

On 12 September 2021, a Boeing 777-300 in cruise at FL380 and approaching Oman from the east at night experienced a sudden left engine failure. The engine was shut down, a PAN call was made, and the crew diverted to Muscat rather than completing the intended flight to Abu Dhabi. An off-wing examination of the GE90 engine found that the hydromechanical unit of the accessory gearbox had malfunctioned in a way which allowed fuel to mix with the engine oil. This failure had not been anticipated in the applicable Fault Identification Manual, which was amended accordingly.

Destination diversion

On 31 January 2022, a Bombardier Challenger 604 pilot lost control during the final stages of a London Stansted night crosswind landing. A bounced nose-gear-first touchdown was followed by a brief runway excursion onto grass before a return to the runway and a climb away. A diversion to London Gatwick followed without further event but subsequent inspection revealed structural and other damage sufficient to result in the aircraft being declared an economic hull loss. The Stansted touchdown was found to have occurred after a premature flare at idle thrust continued towards the stall and a momentary stick pusher activation occurred.

On 25 October 2022, a Boeing 777-300ER encountered deteriorating weather conditions after initiating a delayed arrival diversion from Singapore Changi to nearby Batam where four approaches were flown and a ‘MAYDAY Fuel’ declared before a landing was achieved. By this time, the fuel remaining was “significantly below final reserve” although the actual figure was not published in the Investigation Report. It was concluded that the mismanagement of weather operational risk by the flight crew involved had resulted in potentially hazardous circumstances created by both the delay in commencing the diversion and a lack of professionalism on reaching its vicinity.

On 19 October 2015, an ATR 72-600 crew mishandled a landing at Ende, Indonesia, and a minor runway excursion occurred and pitch control authority was split due to simultaneous contrary inputs by both pilots. A go around and diversion direct to the next scheduled stop at Komodo was made without further event. The Investigation noted that the necessarily visual approach at Ende had been unstable with a nosewheel-first bounced touchdown followed by another bounced touchdown partially off-runway. The First Officer was found to have provided unannounced assistance to the Captain when a high rate of descent developed just prior to the flare. 

On 15 November 2018, a Bombardier DHC8-300 made a main gear only touchdown at Stephenville with only minor damage after diverting there when the nose landing gear only partially extended when routinely selected on approach at the originally intended destination. The Investigation found that the cause was incorrect nose gear assembly which had allowed hydraulic fluid to leak and eventually led to it jamming. There was some concern at the way the flight was conducted following the problem which involved continuous smartphone communications with the operator and an overspeed which it was considered constituted an avoidable risk to safety.

On 16 January 2018, a McDonnell Douglas MD-82 attempting to land at Tarbes was subject to gross mishandling by the crew and the approach became unstable. A subsequent low level go-around attempt was then made without setting sufficient thrust which resulted in sustained and close proximity to terrain at an airspeed close to stall entry before the required thrust was eventually applied. The Investigation was hindered by non-reporting of the event but was able to conclude that multiple pilot errors in a context of poor crew coordination during the approach had caused confusion when the go around was initiated.

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