Aviation Investigation Report A98H0003

1.6.11  In-Flight Entertainment Network

  1. - Description
  2. - Wiring Installation
  3. - Components  Description (STI1-16)

The IFEN system combined computer, video, and audio technologies to allow passengers to select movies, audio, games, news, gambling, and the moving map display through an interactive seat video display. The IFEN was to be configured to give all passengers access to a variety of "on-demand" entertainment and information choices, with touch-screen control. The original design, for the Swissair MD-11, provided full IFEN access to 257 passenger seats, which included all cabin classes; however, only the first two aircraft were configured to have the IFEN available in all 257 seats. For economic reasons, in April 1997, Swissair decided to reduce the IFEN configuration to include only first- and business-class seats.

The IFEN system was installed in the first- and business-class passenger sections of HB-IWF between 21 August and 9 September 1997 (see Figure 14). Although the 49 business-class seats were installed at that time, because of delivery delays, the 12 IFEN-equipped first-class seats were not installed until February 1998. The economy-class passenger section was not configured with the IFEN, even though electrical cabling and equipment rack supports were installed for that section. HB-IWF was the eighth Swissair MD-11 to be equipped with the IFEN system. (STI1-17)  Wiring Installation

The IFEN system, as configured in HB-IWF, required 4.4 kilovolt-amperes of 115 V AC three-phase 400 hertz aircraft power according to the Hollingsead International (HI) electrical load analysis (ELA) 20032 revision (Rev) B. The main power supply cable for the IFEN system consisted of three 8 AWG, MIL-DTL-16878/5-BNL wires twisted together. This cable originated at an electrical terminal strip located in the avionics compartment and was terminated at a 15 A three-phase CB located on the lower avionics CB panel (see Figure 14 and Figure 15). This 15 A CB, identified as "RACK1 PS1," provided aircraft power by means of jumper wires[40] to three adjacent 15 A three-phase CBs located on the lower avionics CB panel. Each of these four 15 A CBs provided aircraft power to one of the four IFEN power supply units (PSU). The PSUs used a series of capacitors and internal electronics to convert the 115 V AC aircraft system power to 48 V DC output power, used by the IFEN system components.

Each of the four 15 A IFEN CBs was connected to its respective PSU by one of four PSU cable assemblies, hereinafter referred to as PSU cables; each PSU cable consisted of three 12 AWG, MIL-W-22759/16/12 wires twisted together.

Additionally, a 1 A CB was installed on the lower avionics CB panel. The CB provided 28 V DC power, by means of a 16 AWG wire (hereinafter referred to as 16 AWG control wire), to the IFEN relay assembly located in the ceiling above Galley 8. This 1 A CB, identified as "IFT/VES 28V," received 28 V DC aircraft power by means of a jumper wire from the line side of the adjacent CB, "SLAT CONTROL PWR B," and was used to control the 48 V DC output of the four PSUs through the IFEN relay assembly. Pulling this CB removed the 48 V DC output power from the PSUs; however, pulling the CB would not remove the 115 V AC input power to the PSUs.

The four IFEN PSU cables (PSU 1, 2, 3, 4) and the 16 AWG control wire were routed rearward along the lower avionics CB panel. In this area, they were attached to the main IFEN power supply cable with nylon self-locking cable ties. This IFEN wire bundle was then cable tied to the DC CB ground bus bar at the lower avionics CB panel and, in some installations, held in place near the rear of the panel by a clamp. The wire bundle was then directed upward until it separated in two directions. The main power supply cable looped downward, passing through a conduit along the right side of the fuselage into the avionics compartment. The four PSU cables and the 16 AWG control wire, now in their own bundle, continued upward as a single bundle near the avionics disconnect panel.

Following the SR 111 occurrence, the IFEN installation was examined in 15 Swissair MD-11s. It was noted that the routing of the bundle containing the PSU cables and the 16 AWG control wire varied among aircraft behind the avionics CB panel. None of these variations were considered to affect the immediate safety of flight. There were differences in how frequently this bundle was supported by any of the three horizontally mounted wire support brackets available, and in the methods used for fastening it to the brackets. Also, some installations had protective sleeving installed adjacent to the brackets, while others did not.

Near the avionics disconnect panel, the IFEN wire bundle was routed aft into one of the 102-cm (40-inch) long conduits that were installed above Galley 2 (see Figure 4 and Figure 5). In 11 of the examined Swissair MD-11s, the wire bundle was routed to pass in front of the avionics disconnect panel, and in three of those 11 installations, the bundles were then routed through the outboard conduit. In 4 of the examined aircraft, the bundle was not routed in front of the avionics disconnect panel; instead, it was routed close to the cockpit wall. In 2 of the 4 installations, the bundle was then routed through the outboard conduit. In total, 5 of the aircraft had the IFEN wire bundle routed through the outboard conduit, and 10 had the bundle routed through the middle conduit.

In the occurrence aircraft, it could not be determined from the IFEN installation documentation how the IFEN wire bundle had been routed in the area of the disconnect panel, or which conduit had been used in the area above Galley 2. The IFEN installers preferred to use the middle conduit where possible, but in the five instances noted above, the middle conduit was not available as it had been used for aircraft wiring. In the sequence of IFEN installations, the middle conduit had been used in the three aircraft prior to HB-IWF, and also in the seven aircraft following HB-IWF.

The investigation was not able to establish from the manufacturer's records which conduit might have been left unused in HB-IWF (SN 48448). In the aircraft built immediately before HB-IWF (HB-IWE – SN 48477), the middle conduit was used for the IFEN wire bundle. In the next Swissair aircraft built after HB-IWF (HB-IWG – SN 48452), the outboard conduit was used for the IFEN wire bundle.

The conduit material, based on DMS 2024 Revision B, was Type 1, convoluted, thin wall, fluorinated ethylene-propylene (FEP). The installation of the wire bundle, from where it exited the aft end of the conduit to approximately STA 515, also varied between aircraft. The wire bundle was found to be routed either above or below the upper horizontal angle support bracket for the R1 door ramp deflector, above or below the wire supports, and was clamped to either the top or bottom of these supports or to existing aircraft wiring. Where the IFEN cables were attached to existing wire harnesses, spacers were installed to provide separation between the wire bundles. Additionally, some of the aircraft had protective sleeving installed over the wire bundle in the area near the R1 door ramp deflector upper support.

The wire bundle continued rearward until the PSU 1 and 2 cables were separated from the bundle and terminated at an IFEN electronics rack (E-rack) 1. E-rack 1 was located in first class above the right aisle, with its forward support located at STA 647.

The 16 AWG control wire continued rearward, then crossed over the aircraft crown at approximately STA 750, and was terminated at the relay assembly mounted above Galley 8. This relay assembly received all of the external interfaces to the aircraft system including the following: the decompression signal, which removed power from the IFEN if the aircraft became depressurized; the PA system override signal, which was designed to stop all audio and video on the IFEN system whenever the PA was used; and the 28 V DC power input supplied by the "IFT/VES 28V" 1 A CB. Removal or loss of this 28 V DC power caused an "On/Off" relay, located within the relay assembly, to disable the output of all the PSUs.

The PSU 3 and 4 cables continued rearward until crossing over the aircraft crown at STA 1239. They were then routed rearward along the left side of the fuselage and terminated at E-rack 2. E-rack 2 was located in economy class above the left aisle, with its forward support located at STA 1429.  Wire Description

The primary wire type selected for the IFEN system installation was MIL-W-22759/16, an extruded ethylene-tetrafluoroethylene (ETFE) copolymer insulation, medium weight, tin-coated copper conductor, rated at 150°C, 600 volts. (See Figure 13.) Additionally, the wires used for the main power supply cable were MIL-DTL-16878, an extruded polytetrafluoroethylene (PTFE) insulation, copper-coated copper conductor, rated at 200°C, 1 000 volts. The MIL-W-22759/16 wire had a maximum temperature rating of 150°C.

The 28 V DC wire, from the 1 A CB in the lower avionics CB panel to the IFEN system relay assembly, was specified as 16 AWG MIL-W-22759/16.

Each IFEN PSU power cable consisted of three, 12 AWG, MIL-W-22759/16 wires twisted together. For circuit identification purposes, MIL-C-27500 specification required the wires for each cable to be coloured white, blue, and orange. The cable was to be labelled using identification markers as called out in an HI drawing.

The main IFEN power supply cable consisted of three, 8 AWG, MIL-DTL-16878/5-BNL wires twisted together as called out in an HI drawing. This drawing also stated that the wire will not be identified by printed marking on the outside of the wire. MIL-DTL-16878/5-BNL specifies an extruded PTFE, maximum rating of 200°C, 1 000 volts. For circuit identification purposes, MIL-C-27500 specification required the wires for each cable to be coloured white, blue, and orange. However, a red wire was substituted for the blue wire in the installation, which had no affect on the performance of the wire. Samples of each 8 AWG coloured wire were analyzed by Fourier Transform Infrared Spectroscopy and identified as PTFE with a melting point of 323°C; this was determined by differential scanning calorimetry.  Components (STI1-18)

E-rack 1 contained the following components (see Figure 14):

  • PSUs 1 and 2 that supplied 48 V DC power to CB Unit 1, which distributed 48 V DC power to the components mounted in E-rack 1;
  • Two electromagnetic interference (EMI) filter boxes, one attached to each PSU. The filters were connected between the power supply input and the PSU, and were designed to filter out conducted EMI from the aircraft power supply;
  • Two 32-channel modulators, which converted the baseband video and audio input signals to broadband RF output signals;
  • A video on demand (VOD), which extracted, selected, and distributed the movie/music data;
  • A disk array unit, which stored the digitally encoded programming;
  • A 13-channel modulator, which performed the same function as the 32-channel modulator, as well as distributed common video/audio information, such as the moving map system, to the entire aircraft;
  • Two head-end distribution units, which combined the separate modulator outputs then split the output four ways; and
  • Six cluster controllers, which coordinated all the computer network administrative tasks.

The VOD was also equipped with a removable disc pack to permit maintenance personnel to upload movies.

E-rack 2 contained the following:

  • PSUs 3 and 4 that supplied 48 V DC power to CB Unit 2, which distributed 48 V DC power to the components mounted in E-rack 2;
  • EMI filters 3 and 4; and
  • A network switching unit, which provided network links for the IFEN administrative network.

Each first- and business-class seat was equipped with an interactive video seat display that included a touch screen and magnetic card reader; a seat electronics box, which processed all information for the passenger interface; and a dual audio/game-port, which controlled the games and audio. In addition, each set of first- and business-class seats was equipped with a seat disconnect unit, which contained the tuner and network repeater.

A cabin file server, located on a rack in Galley 8, controlled the download of movies, stored flight/casino information, and collected the credit card data transmitted from each seat. Galleys 1 and 8 were fitted with a management video display (MVD). The MVD provided an interface for cabin crew and maintenance personnel, and served as a point of control for configuring, maintaining, and monitoring the IFEN. Each MVD was equipped with a management terminal electronic box, the primary functional component interface to the IFEN by the flight crew and maintenance personnel. A printer was also located in Galley 8.

[40]    The jumper wire was a single wire that was installed between common terminals of two circuit breakers.

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