On a bad day, things can go bizarre

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There have been media & unconfirmed reports with pictures of PK8303 with the ram air turbine deployed. Newly released photo’s show oil marks on the runway at Karachi Airport runway 25L. With little confirmed, the whole episode looks quite bizarre. There could be a maintenance error causing an engine oil leak, leading to low oil levels.

For the proponents of the belly landing theory, it looks like this. While the engines touch the ground, the belly also touches the runway. If a go-around is being attempted, then the trajectory has to be really flat to avoid a tail strike.

B-757 Belly Landing

U.S. aviation regulators in 2013 unveiled a proposed safety directive targeting maintenance errors that over the years have caused dangerous engine-oil leaks on more than three dozen Boeing Co. 737 aircraft CFM engines.

I read a similar intriguing report of a past incident with Thomas Cook Airlines A320 aircraft. The aircraft experienced Low Oil Level on Engines 1 and during approach following slats & flaps configuration, a DUAL Hydraulic failure triggered. The two events could not be co-related.

Engine trouble

The crew took off from Brussels (Belgium) bound for Tenerife (Spain). They were informed by the ECAM of an oil level problem on engine no.1. The auto-thrust disconnected two minutes later. The PF made an input on the engine no.1 thrust control. As it responded normally to these inputs, the crew re-engaged the auto-thrust. A Master Warning sounded, associated with low oil pressure on engine no.1. The crew immediately reduced the thrust to idle and then shut down the engine. The aeroplane was then above the Atlantic Ocean, 116 NM west of Bordeaux. The crew took the decision to divert to Bordeaux-Merignac aerodrome (33), after issuing a pan pan message and then a distress message to the ATC. They also informed the operator via an ACARS message about their engine problem.

Interruptions

While the crew was preparing for a single-engine arrival at Bordeaux Merignac Airport, the ECAM yellow system low hydraulic level page was displayed with, at the same time, the Master Caution alert. The crew started to deal with this hydraulic failure, following the associated ECAM page, but then interrupted the procedure after receiving an ACARS message from the operator asking them to fly to Toulouse Blagnac Airport.

Approach

The crew told the Bordeaux approach controller that they wished to divert
to Toulouse-Blagnac Airport. During this diversion the pressure values of the three hydraulic systems remained close to 3,000 Psi (nominal pressure).
On the approach to Toulouse-Blagnac aerodrome, the crew switched the
aeroplane to configuration 1 (leading edge slats and flaps). The pressures on the yellow and green systems dropped considerably (from 3,000 to 2,200 Psi).

A Master Warning alarm was triggered associated with an ECAM green
system low-pressure page. The crew then requested and made a delaying 360°turn on the axis. The combination of low hydraulic pressure on the yellow and green systems lengthened the time required to extend the flight control surfaces.
Nine minutes later, before extending the landing gear, the pressures on the yellow and green hydraulic systems climbed to 3,000 Psi. The landing gear slowly extended and locked. The aeroplane was on the ILS axis.
As the aeroplane landed hydraulic demand climbed to a high level when the flight control surfaces and the engine 2 thrust reverser were used. The aeroplane stopped on the runway with a dual hydraulic failure. The nose gear steering system was inactive and some flight control surfaces remained extended (spoilers, slats, flaps, engine 2 thrust reverser).
On the ground, a hydraulic fluid leak was found and a connection on the yellow the system was found to be loose.

Lessons learnt & conclusion


The investigation was unable to determine whether there was a common link between maintenance operations on the no.1 engine and the yellow hydraulic system. The failure of the yellow hydraulic system was caused by an incorrectly performed maintenance operation. The oil leak on engine no.1 can be attributed either to a maintenance operation or to a deterioration of the magnetic seal.
By fully applying the “yellow system low hydraulic level’’ procedure, the crew would have had to deal with a dual hydraulic failure. Although this situation may seem uncomfortable, it is included in the procedures and training.
Since the “yellow system low hydraulic’’ procedure had not been fully applied, the flight continued with a malfunctioning yellow system and a green system pressurized by windmilling. In such a case, it is not possible to predict the behaviour of hydraulic devices, and a dual hydraulic failure can occur at any time, especially during a critical phase of flight (short final, flare or landing roll as happened on the day of the incident).
Its occurrence had, however, been anticipated by the captain, who asked the co-pilot to prepare the associated procedure.