OPERATIONS
Parts Departing from Aircraft (PDA)
PDAs may be considered by some people as noncritical, especially when the part is small. Yet whatever the size, they may represent a potential safety risk. Preventing them must be the single objective of the combined and coordinated effort of a number of actors.
Parts Departing from Aircraft (PDA) represent a real safety risk
What is a PDA?
A PDA, also called TFOA, which means “Things Falling-Off Aircraft” is any piece of equipment falling from an aircraft, ranging in size from a simple rivet up to a fan cowl.
Why may a PDA represent a potential safety risk?
A PDA may lead to damage vital parts of the aircraft and/or cause serious or fatal injuries to passengers or people on ground. A part detached during take-off may also represent a danger to following aircraft, if the part falls on the runway and is ingested by an engine or projected against a control surface for example.
Example of PDA
Potable water service doors 164AR/154BR were reported to have detached from A330 and A340 aircraft. In one occurrence the panel hit the horizontal tailplane, damaging its leading edge (fig.1 and 2).
(fig.1 and 2)
A potable water service panel was lost in flight and damaged the horizontal tail plane
How can this risk be reduced?
Securing all the parts before aircraft departure is certainly an answer, but it is a bit simplistic. Preventing PDAs starts with aircraft design and goes all the way to the maintenance and crew pre taxi walk-around involving, along the way, a variety of players.
1 – The role of the operators
- Maintenance personnel
Mechanics may reduce the number of occurrences by complying with the procedures, by identifying all elements during the visual inspections, which could lead to a PDA and by making sure they properly close all access panels and cowls after maintenance operations.
- Flight crews
Pilots may do their part by performing a thorough walk-around before each flight.
But there is another, less obvious actor, which has a more remote and transverse, yet important role to play:
- The engineering department
Indeed the recurrence of similar PDAs across the fleet may highlight the need to modify the design, amend a maintenance procedure or training. By reporting all PDA events to Airbus, the engineering department contributes to the identification of areas where a design/procedure/training modification would reduce the risk.
When such a modification is made available, the engineering department then plays a role in its implementation on the aircraft, in the maintenance documentation or in the training course material.Airbus has raised awareness about the need to report PDAs through a dedicated Operator Information Transmission (OIT ref 999.0094/12) and a WISE article (ref.EngOps-14921).
The reporting itself has been facilitated by the introduction in the Trouble Shooting Manual (TSM 05-50) of a standardized PDA Reporting Sheet (fig.3) and the creation of a generic reporting e-mail address: pda.reporting@airbus.com
(fig.3)
Standardized PMA reporting sheet
2 – The role of the manufacturer
As mentioned above, the modification of the aircraft design, the maintenance procedures or training may play a significant part in the reduction of PDAs.In fact, the role of the manufacturer is to:
- Investigate all PDA occurrences
- Develop mitigating solutions, which may range from a simple information or training recommendation to operators up to a maintenance procedure change or design enhancement
- Communicate these solutions to the operators
- Monitor the in-service effectiveness of these solutions
- Report all PDA events to EASA
But… To fulfil this role, Airbus is entirely dependent on the information provided by the operators. It is therefore very important that airlines report all PDA occurrences to their manufacturer so that they can benefit from the PDA prevention measures that Airbus may develop.
Illustration of a solution developed following a report to Airbus
Using the example of potable water service doors 164AR/154BR detachment, the PDA events were reported to Airbus, which then launched an investigation. Analysis of the occurrences concluded that the loss of the panels were attributable to both worn hinges (fig.4) and deficient locking mechanisms (fig.5).
(fig.4)
Pre mod worn service panel hinges
(fig.5)
Pre mod service panel latch
Pre-Mod
This led to the development of Modification n°53666 (Service Bulletin n°52-3076/4087/5010), which increases the hinge pin bearing area (fig.6) and Modification n°201715 (Mandated SB n°52-3086/4094/5019), which consists in replacing the existing latches by more robust models (fig.7) and by introducing an additional latch on the leading edge of the door.
(fig.6)
Post mod hinges
(fig.7)
Post mod latch
Post-Mod
No new occurrences were reported on aircraft which had these modifications embodied. The lessons learnt from these occurrences were transferred to the A350 design and will also be transposed to all future programs.
Parts Departing from Aircraft range in size from fan cowls – which were the subject of a specific Safety first article on July 2012 (issue 14) – down to a simple nut. However they share a common point: they may all represent a safety risk to the aircraft and its occupants, to people on ground or to following airplanes if they land on a runway.
Manufacturer and operators both have the responsibility to minimize the number of PDA occurrences, but the former definitely needs the cooperation of the latter in order to be able to fully play its role. Airbus therefore needs to be informed by the operators of all PDA occurrences, no matter the shape, material, size or weight of the detached part.
The reporting itself has been facilitated by the introduction of a standardized PDA Reporting Sheet, in chapter 05-50 of the Trouble Shooting Manual, which may be sent to the following generic e-mail address: pda.reporting@airbus.com
This will allow Airbus to:
- monitor PDA events and launch appropriate prevention actions, through communication, training, maintenance tasks or redesign
- check the efficiency of these preventive actions
References
CONTRIBUTOR
Jérome REAL
Engineer, Propulsion Systems Customer Services