A380
Maintenance Airframe; Maintenance Powerplant
Maintenance Technician 35
Confusion; Situational Awareness; Communication Breakdown
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural FAR
General None Reported / Taken
Aircraft; Human Factors; Incorrect / Not Installed / Unavailable Part
At the time of design/development of the GP7200-powered Airbus A380 aircraft; Airbus required a 'scupper' or drip pan; underneath the engine pylon raceway fluid connection fittings. The outlet; or drain; of this drip pan; which is exposed to prevailing nacelle pressures; is connected to the Zone 'A' pylon/strut drain line; that leads from the interior floor of the engine pylon (or 'strut') down to the engine-mounted [lower] drain mast; and open to atmosphere at the lower end of the drain mast. During normal engine operation; the nacelle will be pressurized with respect to ambient atmospheric pressure; due to the operation of the Core Compartment Cooling system and other factors. The interior of the engine pylon [compartments]; will remain at ambient atmospheric pressure. By connecting the [scupper] drip pan drain [line] to the [pylon/strut] Zone 'A' drain [line running down] inside the nacelle; the nacelle [pressurized] air will flow not only through the [scupper] drip pan drain exit towards the [lower] drain mast; but also 'upwards'; into the pylon interior cavities. [One] Fire Zone (the engine nacelle area); is therefore connected to a Flammable Fluid Leakage Zone (the pylon interior).This violates 14 CFR 25.1187 (c); which states: '(c) No ventilation opening may be where it would allow the entry of flammable fluids; vapors; or flame from other zones.' It is the flammable fluids and vapors aspect of this regulation that is of most concern. Although the probability of an accident or incident occurring from this situation is low; (it would take both a flammable fluid or vapor source in the [engine] nacelle and an ignition source in the pylon or strut simultaneously); the results could be catastrophic. Airbus and General Electric Aircraft Engines Management were advised of this concern in writing at the time of design; well before engine and aircraft certification. Both Management teams chose to ignore and disregard this concern and issue. Determine if this configuration still exists on the applicable aircraft (or any other Airbus aircraft); and if so; issue Airworthiness Directives (AD) as required to the Aircraft and Engine manufacturers; as applicable; to correct the situation.
Reporter stated when he refers to the pylon/strut area he is talking about the area above the core engine firewall and fan case. The nacelle area would be the engine area enclosed by all the cowlings. The lower section of the pylon has drain hole covered by a screen with a drain line connected under the lower surface of the pylon to allow any water; fuel or hydraulic fluids to drain down and out of the pylon. The pylon drain line normally runs down uninterrupted (no other connections attached or 'Teed' into the line) to the lower drain mast at the engine's bifurcated cowling area. The pylon area is subject to whatever ambient (outside) atmospheric pressure exists. However; the inside area of the engine nacelle is subject to cooling ram air or bleed air and slightly pressurizes the nacelle above ambient pressure. Reporter stated the scupper; or drip pan; that collects fluid from the engine fuel and hydraulic disconnect lines under the pylon in the nacelle area; is subject to that same nacelle air pressure; which is greater than the pylon ambient pressure. The pylon and nacelle areas are completely separate zone areas. Instead of running a separate drain line from the scupper pan down to the lower drain mast; GE/Pratt connected the scupper drain line to the drain line running down from the pylon; using a 'T' fitting. Reporter believes the connection with nacelle air pressure would allow for the possibility of pressurized flammable fluids and vapors from the pressurized nacelle area to flow not only down to the lower drain mast; but upwards into the pylon compartment cavities. Reporter suggests that GE/Pratt run a dedicated drain line from the scupper drain pan down to the drain mast and just 'cap-off' the scupper line connection to the 'T' fitting that was installed on the pylon drain line. His whole premise of concern is the breach in maintaining separate Zones; i.e.; pylon/strut from the engine nacelle as required under FAR 25.1187 (c). Everything under the lower side of the engine pylon is considered engine hardware; including the drain system; which would become General Electric (GE) and Pratt's responsibility.
An Aircraft Maintenance Technician (AMT) reports his concerns about a design issue involving fluid drain lines in the pylon and engine nacelles of A380 aircraft equipped with GP7200 series engines. Technician notes that connecting the ambient pressure pylon drain line with the pressurized engine nacelle scupper pan drain line is not in compliance with 14CFR 25.1187 (c) and would 'allow the entry of flammable fluids; vapors; or flame from other zones.'