This year AEC created an amendment to the WAAS STC for the EC-145. The existing commercially developed EC-145 STC for WAAS implementation modified an aircraft with dual Garmin GNS-430 VOR/LOC/COM/GPS units, a DM 451 Distance Measuring Equipment (DME) system, and dual FCDM/SMD-45 systems. The final configuration for this aircraft allows Single Pilot/Dual Pilot Instrument Flight Rules (SP/DPIFR) with NMS1-2 switching capable of GPS display on either FCDM/SMD-45 system. The specific aircraft that was used for the initial STC work had several items of equipment that were installed outside of the Type Certificated option choices. As a result, the aircraft pre-modification configuration for the prototype installation of the STC was very different from the Type Certificated options pre-modification configuration. The revision of the STC to account for the configuration differences is required in order to allow for a broader aircraft serial number applicability baseline. A large number of MBB-BK 117C-2 aircraft serial numbers have no provisions for display of the #1 GPS on the FCDM/SMD-45 systems since the NMS1-2 switching option was not installed in these aircraft. The baseline MBB-BK 117C-2 aircraft GPS system status annunciator location are not within the primary field of view of the flight crew as defined in FAA guidance material. This has important implications to be detailed later in this document. There are further issues with the certification basis and physical location of the GPS antennas. The Flight Manual Supplement for the existing EC-145 STC for WAAS implementation places a temperature limitation of “ISA+29°C, limited to +44°C” on the aircraft. This limitation is due to the GNS-430 and cooling fan systems on the original EC-145 having been installed by the FAA “Field Approval” process. The new baseline configuration aircraft has a cooling system for the Garmin GNS430 units installed under the Type Certificated design data. The intent of the STC revision is to not disturb these original Type Certified systems and therefore, not incur any such temperature restrictions.
In order to properly implement an integration solution for the new baseline configuration aircraft in the EC-145 WAAS STC, these differences must be clearly outlined and understood. The EC-145 WAAS STC revision to allow incorporation into the target configuration aircraft is outlined below. • The EC-145 WAAS GPS antennas are not collocated on the tailfin console as the target configuration GPS antennas are. The GPS antennas were separated to mitigate the possibility of a lightning strike incapacitating both antennas simultaneously. This modification is required on the target configuration aircraft also. • The target configuration aircraft GA-35 GPS antennas are not appropriately certified for the lightning zone that they are installed in on the vertical fin location. The GA35 environmental data reflects “2A” qualification and the target configuration aircraft vertical fin location is categorized as Zone “1B”. A primary implication is that the antenna could become partially or substantially detached from the mounting during a lightning event. This could have detrimental safety impacts on the tail rotor. • The EC-145 GPS antenna tailfin console is not the same as the target configuration tailfin console. The EC-145 tailfin console supports a single large CI428-200 GPS WAAS COMDAT antenna for the #2 GPS system. The CI428-200 antenna is appropriately lightning qualified for the tailfin zone location. The target configuration tailfin console supports two smaller GA35 GPS antennas for systems #1 & #2. There are two distinct versions of the target configuration tailfin console in use. The STC design document revision allows the possibility of using either version of these consoles. Retrofit consoles are to be repaired and then modified for the new antenna while production version consoles will not require a repair, only installation of the new antenna. The original WAAS STC EC-145 CI428-200 GPS WAAS COMDAT antenna for the #1 system was mounted to a bracket assembly installed on the upper tail boom left side between frame 8 & 9. (Forward of the horizontal tail plane structure.) For the target configuration aircraft this location is above ARC-231 antenna on some configurations, above a P-2000 antenna in other configurations, and near a SATCOM transceiver antenna location for another configuration. Testing has shown blanking of the GPS signal
when installed in close proximity to these configurations. The STC revision requires the installation of a GPS WAAS COMDAT Comant part number CI 428 200 antenna which will replace the GPS #1 antenna. 428-200 This antenna will be mounted to a centerline fairing located aft of the upper Wire Strike Protection Blade. Flight testing of this configuration has been accomplished and verified as part of this project. accomplished See “Figure 1 New GPS#1 Antenna & Fairing Location below tenna Location”
Figure 1 New GPS#1 Antenna & Fairing Location • The original EC-145 WAAS STC installed a switching relay box to select between GPS1 or GPS2 145 outputs being displayed on both FCDM/SMD 45 and the annunciation of the various GPS FCDM/SMD-45 “status” indications. The target configuration aircraft does not have wiring to support the display of the GPS1 outputs to the FCDM/SMD 45 systems and status indications. Only the isplay FCDM/SMD-45 GPS2 system is currently displayed on both FCDM/SMD 45 systems. The target configuration FCDM/SMD-45 required additional wiring to be installed to obtain the GPS1 system data and status st annunciations to the new switching relay. As a side note, the switching is required to be called and indicated as NMS1 & NMS2 for FAA certification in order to match the naming conventions in the software for the annunciations on the SMD SMD-45 displays. • The EC-145 WAAS STC switching relay box (RS 012) was installed in a location inside and 145 (RS-012) forward of the slant console that for the target configuration aircraft is congested with wire harness routings. The appropriate option is the addition of a Sandia SR 23 relay circuit card to SR-623 the SRU-5 housing that duplicates the functions of the switching relay box. The SRU housing is 5 SRU-5
already installed on certain aircraft with customer mission packages. The target configuration aircraft will require the installation of the SRU-5 housing. • The EC-145 GPS WAAS Status annunciations have no provision for NVIS compatible annunciators. The revision to the STC is required to allow for any NVIS capabilities of the aircraft by utilization of the Aerospace Optics LED series that have been incorporated into other configurations. • The EC-145 WAAS STC Engineering documentation addresses only a Single Pilot Instrument Flight Rules (SPIFR) aircraft configuration while the STC Flight Manual Supplement and the STC approves a Single Pilot/Dual Pilot Instrument Flight Rules (SP/DPIFR) aircraft. In order for the target configuration to obtain GPS WAAS with LPV approach capabilities, the GPS status annunciators must be located within the “Primary Field of View” for each flight crew member. It has been communicated that some customers maintain an operational requirement for dual pilot at all times. Such a requirement demands that the annunciators be on both sides of the cockpit. The “Primary Field of View” is defined by FAA “Human Factors Design Standard” (HFDS 2002). o Chapter 6.2.2.1.8 Location of indicators for critical functions states: “Indicators for critical functions shall be located within 15° of the user’s normal line of sight, as illustrated in Exhibit 6.2.2.1.8.” o Chapter 2.6.10 Design for 5th to 95th percentile states: “Systems and equipment shall be, at minimum, designed for personnel from the 5th through the 95th percentile levels of the human physical characteristics that
represent the user population.”
Figure 2- FAA Primary Field of View
o The Flight Department ODA UM’s, in conjunction with the Engineering and Program Departments have conducted an “on aircraft” mock-up and evaluation of the pilot and copilot annunciator relocation/addition. The determination was made and will be implemented in the STC revision for the annunciator locations to be centered above the PFD SMD-45 on both crew member sides and attached to the bottom surface of the glare shield. The new location obscures the existing “radio call” placards from view and as a result of this one placard will be relocated to the center instrument panel area and one placard will be removed from the aircraft. The annunciators are shown below in Figure 3.
Figure 3 Annunciator location
•
The EC-145 WAAS STC included the addition of a backlighted pushbutton switch for the “COM2 XFER” feature in the lower instrument panel area adjacent to the existing annunciator/switch grouping. The some target configuration aircraft have this “COM2 XFER” feature but implements an unlit pushbutton switch along with a post light assembly or back-lighted overlay panel depending on aircraft version. This switch and light are mounted in a dedicated Dzus panel located in the right side of the slant console area. Relocation of the switching function to the lower instrument panel area and change of switch type would free the slant console location for other functions such as the addition of a smaller version of the AHRS Free Steering Mode control panel. The relocation of this transfer switch utilizing an NVIS compliant annunciator/switch is accomplished in the STC revision.
•
The original EC-145 WAAS STC installed a second LD12 light dimmer supply in order to support the annunciation/switch lighting requirements for the NMS1-2 switching and status annunciators. The LD12 was installed as a “piggy-back” on the existing LD12 light dimmer supply. The location of this installation is not viable for the target configuration due to wire harness routing in this location. For some target configuration aircraft with SA 3 already installed on the aft avionics shelf; the SA-3 circuit card will be replaced with the newer version SA-3 NVG circuit card and one additional NVG logic wire installed between the aircraft lighting circuits and the new circuit card. See Figure 4 below:
SRU-5 Housing SR623 Switching Card SA 3-NVG Card
Forward
Figure 4 New Annunciation/Switch Lighting Location
•
The EC-145 STC installs a pair of relays that are used to remove DME Distance data from both FCDM/SMD-45 systems if either GPS #1 or #2 is selected for display on the FCDM/SMD-45 systems. The FCDM/SMD-45 system software is not capable of differentiating between GPS distance and DME distance and would superimpose one on the other if presented with both signals. The resulting distance display is not readable and therefore must be externally switched out for the deselected source. Relays and sockets remain identical as the commercial version.
•
The original EC-145 STC required the installation of an avionics cooling fan for the Garmin GNS430 units that incorporated a “monitor” indicating circuit in case of a failed fan and resultant
diminished cooling of the GNS-430 units. This installation was driven by this particular EC-145 not having the Type Certificated avionics cooling system and the TC installation of the GNS-430 systems. The target configuration aircraft has the Type Certificated avionics cooling fan system and the Type Certificated GNS-430 systems already installed. Therefore, installation of the original STC version cooling fan and monitoring circuits is not required. • The EC-145 STC documents do not perform the software configuration settings of the Garmin GNS-430 units in the same manner as the target configuration aircraft program documents. Each aircraft has a specific Configuration Document that sets all parameters of both the #1 and #2 GNS-430 units in order to properly interface each unit to the aircraft equipment such as the FCDM/SMD-45, lighting, DME, and etc. The GNS-430 units will not require a new configuration document version. The GNS-430W units have additional configuration requirements that are addressed properly by Garmin service bulletins and by the existing STC documents and reports. • The EC-145 STC documents require specific software 4.01 upgrade to the GNS-430 units if not already installed. An Engineering Report and Garmin service bulletin documents that are specified by the STC documents contains instructions for installing the upgrade and enabling the Satellite Based Augmentation System (SBAS). No differences between retrofit and production aircraft versions are identified. • The EC-145 STC documentation removes the Thales FCDS SMD-45 units part number C19267VG11 and replaces them with part number C19267ZG12 units. There are four possible part number versions that could be identified in the target configuration aircraft fleet. o VG11- Obsolete due to parts availability and not WAAS compatible. o ZG12- A modified VG11 that is WAAS compatible. o YA01- Current production replacement for the VG11 and not WAAS compatible. o YA02- Current production WAAS compatible. An ECD Service Bulletin currently exists that controls and configures the upgrade of these SMD45 units to the WAAS configuration. The STC must invoke this Service Bulletin as a “prerequisite” for the STC. • The EC-145 STC package documents a test procedure that is performed on the aircraft to validate the installation.
•
The EC-145 STC package Flight Manual Supplement (FMS) was updated to be compatible with the design for the final configuration and compliance with the applicable FAA requirements.
•
For the new version of the STC a new Instructions for Continued Airworthiness (ICA) also known as Maintenance Manual Supplement was created to show the new configuration only.
The flight test, covering both performance and vibration testing went very well. The relocated GPS antenna showed no degradation in performance. Certification went very smoothly and the FAA returned accepted the RFMS and ICA just before the Government shutdown.
