ATC Lasham
A320 overhaul expertise 01256 356123.

A story of A320 aircraft damage and its detection.

Type-qualified engineers

The landing at Bristol Airport was conducted in a strong crosswind with
associated turbulence. During shutdown the crew was presented with an
automatically generated aircraft warning that certain parameters had been
exceeded during the landing. The crew reported this in the Technical
Log. A type-qualified engineer met the aircraft on arrival and complied with
his understanding of the technical checks required after such a warning.
However, substantial damage had occurred to the landing gear and this damage
was not detected before the aircraft was cleared for a further flight. On that
flight, the crew experienced landing gear problems after takeoff, together
with other ECAM warnings, and diverted to Manchester Airport. Despite
further engineering checks, the aircraft was once again released for flight
without the damage being detected; this resulted in a repeat of the landing gear
problems after takeoff, together with the ECAM warnings. After the return
to Manchester, engineers finally discovered the damage.
Why was this damage not detected on the two inspections?

A320 maintenance support

The operator’s procedures allow for an approach to be continued, even though
the indicated crosswind may be out of limits during the approach, providing
the latest tower reports are within landing limits. However, the operator has
re-emphasised to its crews that this is the ‘aircraft’ limit, and crews may decide
to be more conservative on the day. If there is any doubt then the crew should
not continue the approach.
The commander disconnected the autopilots about 100 ft above the runway
threshold, this was 5 seconds prior to initiating the flare and 8 seconds before
touchdown. In the prevailing turbulent conditions this allowed insufficient
time to separate the piloting tasks of taking control of the aircraft and flaring
the aircraft to land. In addition, during the remaining flight to touchdown,
the pilot made a number of increasingly large control inputs, in both pitch
and roll, in an attempt to maintain the required flight path. At the same time,
changes to both the groundspeed and airspeed indicated the presence of an
increasing headwind. As a consequence of the successive pitch
control inputs the rate of descent increased and the aircraft descended below the glidepath. The two main contributors to the heavy landing were successive pitch control inputs which increased the rate of descent and the longitudinal wind gradient, with an increasing tailwind just before touchdown.
The aircraft touched down on the right main landing gear, with 2.5º angle of
bank to the right, and about 400 milliseconds later on the left main landing
gear. At touchdown the aircraft bounced. After takeoff on the following flight, the flight crew were not able to retract the landing gear. This was due to a sensor signalling that the right main landing gear was still compressed.
It is possible that had the gear not been able to compress during the
retraction, there was the likelihood of damage to the gear and the gear door.
Having successfully retracted the gear the crew reviewed the remaining
warnings while established in a holding pattern at 5,000 ft. Having considered
the possible implications on their landing performance, the available runways
and associated weather information, they decided to divert to Manchester. This
had the added advantage of being the main operating base for their company,
where maintenance support would be readily available. Prior to leaving the
holding pattern, they lowered the gear to ensure correct operation, to reduce
the ECAM messages and to increase the fuel consumption and thereby reduce
the landing weight. The crew subsequently conducted a gentle landing at Manchester.
The aircraft was subsequently returned to service and the same crew were tasked
to position the aircraft back to Bristol. After takeoff, the gear failed to retract
and the crew were presented with almost the same warnings as on the previous
flight. They reselected the gear down and returned to land at Manchester.

Rare failure of A320 engineering activity

The significant damage to the right main landing gear upper diaphragm tube was
caused by the initial heavy landing at Bristol. Although checks were carried out
at Bristol, an opportunity to find this damage was missed. A second opportunity
to discover the damage occurred at Manchester after its first arrival following
the diversion. Again, this opportunity was missed. It was only after the second
landing at Manchester that the damage was discovered. This, together with previous hard landings on A320 aircraft, demonstrates that the aircraft is able to withstand such landings without suffering major structural damage. The subsequent landings at Manchester also indicate how strong the landing gear is and that it is still capable of providing some shock absorbing despite the damage sustained. However, the weakest point appears to be the landing gear, and in particular the upper diaphragm, the failure of which is not readily apparent when the aircraft is on the ground. The failure only becomes apparent when the weight is taken off, such as during jacking.
Therefore, the only method of determining whether the landing gear has suffered any damage during the landing is to jack the aircraft.

Third party maintenance organisations

Because the appropriate limits had been exceeded during the landing the
aircraft produced a LOAD <15> report, something that the engineer who met
the aircraft had not seen before. The aircraft’s operator had only recently
started its winter season programme at Bristol. The engineer at Bristol had had no formal training on the use of the system. He had not received the required training
from the operator on their practices, procedures and documentation. The inspection he carried out only required the jacking of the aircraft if damage was identified to the gear or the surrounding structure.
Since he did not see any such damage he assumed that everything was in order
and released the aircraft.
In the absence of any training, he had assumed that when ‘print job card’ is
selected it would provide all the variants of the check.

Airbus 320 heavy maintenance

Modern aircraft, such as the A320, have complex systems and the maintenance
manuals for such systems, which are provided electronically, can be just as
complex. Therefore, adequate training in the use of these documents is essential to the continued safe operation of the aircraft.
The operator provides bi-annual continuation training on policy, procedures and
the use of its documentation.
As part of the subcontracting process for line maintenance, the operator’s quality
department carries out annual audits of the third party maintenance organisations.
The operator’s audit paperwork requires a check of the personnel’s training,
including the bi-annual continuation training, and following this incident an
audit in December 2006 highlighted the 3 engineers who had not completed
this training. This audit, however, did not highlight the fact that all of the
engineers at Bristol had not received formal training on the recently introduced
AirN@V system. If these audits do not identify failures in training, especially
on new aircraft manual software which should be a reasonably straightforward
area to audit, the efficacy of such audits must be in doubt.
The expectation of the operator was that at any outstation the engineers, whether their own or those from a third party, would contact them if there was any lengthy unscheduled maintenance or defects that may affect the operating schedule for the next day. In this particular case, the operator would have expected the engineer at Bristol to report the heavy landing, with its associated lengthy checks. Similarly, the engineer, who did not know the significance of the LOAD <15> report could have contacted the operator’s Maintrol for advice. It is likely that had this occurred then the Maintrol engineer would have contacted the operator’s specialist technical services engineer. He would then have been able to provide advice on interpretation of the report and the corrective action required. It is also likely that the Maintrol engineer, who was familiar with AirN@V, would have discovered the more appropriate check
and found the requirement to lift the aircraft.

Second opportunity

The second opportunity to discover the damage was following the first landing
at Manchester. Prior to the aircraft’s arrival at Manchester, Maintrol had been
made aware that the aircraft had diverted due to problems with the landing
gear and thrust reversers. As a result, a team of engineers were briefed to
meet the aircraft to carry out the required troubleshooting and rectification
work. At this point Maintrol had not been made aware of the LOAD <15>
report or the fact that it had suffered a heavy landing at Bristol. The ASR that
was filed by the flight crew was not sent to Maintrol, but to the operator’s
safety department. Also, the engineer at Bristol had not been in contact with
the operator’s Maintrol either since he believed that the check, which had
identified no damage, had been completed correctly. The first time that the
engineering team become aware of the LOAD <15> event was when the
aircraft’s technical log was reviewed following its arrival. However, since
the technical log had already been cleared, with a satisfactory inspection in
accordance with the AMM, the engineering team believed that this was not
the cause of the faults on the diversion flight. No further action with regard
to the heavy landing, by the engineering team, was carried out following this
first arrival.
The troubleshooting that was carried out correctly identified the sensor as the
problem area. However, the root cause of the problem was not due to a sensor
or target failure, but the over extension of the right main landing gear. On
the ground everything appeared normal and the engineers did not connect the
previous LOAD <15> report and a proximity problem with the sensor to
possible internal damage to the gear leading. The sensor was replaced and the fault cleared; this led the engineers to the conclusion that the defect had been remedied. The aircraft was therefore released to service.

Moral of the story…
Even with the best, the maintenance training and procedural controls can be better.
Contact the best
ATC Lasham
A320 overhaul expertise
00 44 (0)1256 356123