An air accident report into a crash between two Ryanair aircraft at Dublin airport has revealed difficulties with "winglets" -- the upturned end points of wings -- which are increasingly being fitted to aircraft across the world.

In two separate crashes at Dublin airport, the winglets of Ryanair Boeing aircraft struck other Ryanair aircraft during taxiing on the ground.

In one, the winglet detached from its parent aircraft and became embedded in the tail elevator of another aircraft. In a separate incident at Stansted, a Ryanair aircraft was so damaged that fuel leaked out on to the ground.

Similar incidents involving winglets have been reported in Europe and the U.S. where recommendations that airlines place pilot aides such as cameras on the winglets were vetoed on the basis of cost.

Winglets are increasingly being used by aircraft-makers such as Boeing and Airbus as they reduce fuel usage and emissions as well as increasing stability in the air.

The air accident investigation unit at the Department of Transport, which investigated the Irish crashes and reviewed data from similar crashes globally, has now recommended the world aviation authority, the International Civil Aviation Organisation, reassess the need for visual aides for pilots.

Review of material

It also said Ryanair should review the guidance material provided to flight crews regarding the difficulty associated with assessing wing-tip clearance.

A third recommendation was that Dublin Airport Authority conduct a critical review of the taxiway system at the airport, "to ensure that taxiway routes are as simple as possible in order to avoid pilot confusion and the need for complicated instructions".

The three recommendations were in the report of the first of the winglet incidents, which occurred on October 7, 2014, in poor visibility during busy conditions at 5:45 a.m. Both aircraft involved were Boeing 737-8AS models operated by Ryanair.

As the first aircraft carrying 88 passengers and six crew was approaching runway 28 for take-off there was a queue, and it paused on an approach route known as link two.

Collision

The second aircraft with 100 passengers and eight crew on board then approached via link two preparing to turn for runway 34. As the second aircraft made a right turn, the tip of the port side winglet struck the starboard side elevator at the rear of the stationary craft.

The moving aeroplane suffered damage to the tip of port winglet while the other suffered damage to the starboard elevator.

The commander of the stationary aircraft initially thought it had been rocked by jet turbulence from a departing aircraft ahead of him. However, he heard the second aircraft calling in the collision to air traffic control and realised his aircraft had been hit. All passengers and crew were taken from the aircraft without injury.

The report also notes that on April 1st, 2015, "a second similar ground collision occurred between two B737-8AS in the vicinity of link two".