Airworthiness Directive · Amendment 39-16548 · Sikorsky Aircraft Corporation (Sikorsky) Model S76A, B, and C Helicopters
Sikorsky Aircraft Corporation (Sikorsky) Model S76A, B, and C Helicopters
Model S-76A, B, and C helicopters, with LITEF LCR-100, Attitude Heading and Reference System (AHRS) Unit, part number (P/N) 145130-7100, installed, certificated in any category.
This amendment supersedes an existing emergency airworthiness directive (EAD) for the specified Sikorsky model helicopters. The EAD requires inspecting the LITEF Attitude Heading and Reference System (AHRS) unit of the navigation system to determine if it is at a Mod Status "18." If either AHRS unit is at Mod Status "18," the EAD requires installing placards on the instrument panel to prohibit single pilot instrument flight rule (IFR) and single pilot night flight and reducing airspeeds to 120 knots indicated airspeed (KIAS) if both autopilots uncouple during instrument meteorological conditions (IMC) or night flight. The EAD also requires inserting minimum crew and airspeed limitations into the Limitations section of the applicable Rotorcraft Flight Manual (RFM) to limit the minimum flight crew to 2 pilots for night flight and IFR flight and to reduce airspeed to 120 KIAS if both autopilots uncouple during IMC or night flight. This amendment contains the same requirements but draws the appropriate distinctions between IFR and IMC as used in the intended operating limitations. Also, unlike the EAD, this AD states the airspeed must be reduced to 120 KIAS if both autopilots uncouple during IMC or night flight. Further, we are removing the limitation contained in the Active Temporary Revisions relating to pilots keeping their hands and feet near the flight controls. This AD was prompted by the need to supersede the EAD to state the distinction between IFR and IMC as used in the operating limitations and to reduce the airspeed to 120 KIAS if both autopilots uncouple during IMC or night flight. The actions specified by this AD are intended to implement operating limitations based on an anomaly in the AHRS related to the 26 volt AC inverter that could result in a decoupling of both autopilots and to prevent loss of control of the helicopter during IMC and during night flight.
To implement operating limitations based on an anomaly in the AHRS related to the 26-volt AC inverter that could result in a decoupling of both autopilots and to prevent loss of the helicopter during instrument meteorological conditions (IMC) and while operating under instrument flight rules (IFR) and night flight, do the following:
(a) By referencing the nameplate of the No. 1 and No. 2 AHRS unit, determine whether the modification (Mod) status is at “18.” If the Mod status is “18” for either AHRS unit:
(1) Install instrument panel placards as shown in Figure 2 in the areas depicted in Figure 3 of Sikorsky Alert Service Bulletin No. 76-34-11, dated May 17, 2010 (ASB), and by following the Accomplishment Instructions, paragraph 3.A.(6)(c) through (d) of the ASB.
(2) Revise the “Minimum Flight Crew” section of the Operating Limitations section of the Rotorcraft Flight Manual (RFM) as follows: “For helicopters with an LCR-100 Mod Status ‘18’ AHRS installed, two pilots are required for IFR and night flights.”
(3) Revise the “Airspeed Limits” section of the Operating Limitations section of the RFM as follows: “For helicopters with an LCR-100 Mod Status ‘18’ AHRS installed, airspeed is limited to 120 knots indicated airspeed (KIAS) when both autopilots are uncoupled and operating at night or in IMC.”
(4) When present, remove and discard the following Active Temporary Revisions from the Operating Limitations section of the RFM for each affected helicopter:
| Model | RFM document No. | Active temporary rev. No. |
|---|---|---|
| S-76A | SA-4047-76-1 | T-Revision 3. |
| S-76B | SA 4047-76B-1 | T-Revision 3. |
| S-76C (TurboMeca Arriel 1S1 engines installed) | SA 4047-76C-1 | T-Revision 3. |
| S-76C (TurboMeca Arriel 2S1 engines installed) | SA 4047-76C-10 | T-Revision 4. |
| S-76C (TurboMeca Arriel 2S1 engines installed and s/n 760511 and subsequent) | SA 4047-76C-14 | T-Revision 4. |
| S-76C (TurboMeca Arriel 2S2 engines installed) | SA 4047-76C-15 | T-Revision 1. |
(5) Revise the Operating Limitations section of the RFM by inserting a copy of this AD into the appropriate section of the RFM.
(b) To request a different method of compliance or a different compliance time for this AD, follow the procedures in 14 CFR 39.19. Contact the Manager, Boston Aircraft Certification Office, FAA, Attn: Tony Pigott, Aviation Safety Engineer, 12 New England Executive Park, Burlington, MA 01803, telephone (781) 238-7158, fax (781) 238-7170.
(c) The Joint Aircraft System/Component (JASC) Code is 3420: Navigation.
(d) Installing the placards shall be done by following the specified portions of Sikorsky Alert Service Bulletin No. 76-34-11, dated May 17, 2010. The Director of the Federal Register approved this incorporation by reference in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Sikorsky Aircraft Corporation, Attn: Manager, Commercial Technical Support, mailstop s581a, 6900 Main Street, Stratford, CT, telephone (203) 383-4866, e-mail address tsslibrary@sikorsky.com, or at http://www.sikorsky.com. Copies may be inspected at the FAA, Office of the Regional Counsel, Southwest Region, 2601 Meacham Blvd., Room 663, Fort Worth, Texas, or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.
The aircraft, engines and makers this AD names, by the model designations in its text. A model listed here may still be outside the AD's serial ranges.
Aircraft
