FAA 

Aviation Safety

EMERGENCY 

AIRWORTHINESS DIRECTIVE

www.faa.gov/aircraft/safety/alerts/ 

DATE: May 19, 2010 

AD #: 2010-11-52 

 This Emergency Airworthiness Directive (AD) is prompted by reports of intermittent 

malfunctions of the LITEF Attitude Heading and Reference System (AHRS) units of the navigation 

system. This condition, if not corrected, could result in malfunction of the autopilots, inability to 

reset the autopilots, an uncommanded roll, reduction in rotorcraft functional capabilities, inability of 

the crew to perform the required tasks, and subsequent loss of control of the helicopter. 

 We have reviewed Sikorsky Alert Service Bulletin No. 76-34-11, dated May 17, 2010 (ASB). 

The ASB specifies informing operators of an interim minimum flight crew restriction of two pilots 

for Instrument Flight Rules (IFR) and night flight for helicopters equipped with LITEF LCR-100, 

Mod Status 18, AHRS units. The ASB also specifies removing and inspecting the AHRS units to 

determine if part number (P/N) 145130-7100, Mod Status 18, is installed. Also, the ASB specifies if 

an AHRS unit with LITEF LCR-100, P/N 145130-7100, Mod Status 18 is installed, identifying the 

unit with a placard with a different P/N. Finally, the ASB specifies installing 2 placards P/N SS9140-

1746 or locally fabricated placards onto the instrument panel. 

 This unsafe condition is likely to exist or develop on other helicopters of these same type 

designs. Therefore, this AD requires inspecting the AHRS unit to determine if it is a Mod Status 18. 

If the nameplate on an AHRS unit is P/N 145130-7100, Mod Status 18, this AD requires installing 

placards on the instrument panel to prohibit single pilot IFR and single pilot night flight, and 

reducing airspeeds to 120 KIAS if both autopilots uncouple during IFR or night flight. This AD also 

requires inserting Active Temporary Revisions into the Limitations section of the applicable 

Rotorcraft Flight Manual (RFM) to limit the minimum flight crew to two pilots for IFR and night 

flight and to reduce airspeed to 120 KIAS if both autopilots uncouple during IFR or night flight. This 

AD does not require installing placards on the AHRS unit as specified in the ASB. The actions must 

be done by following specified portions of the ASB described previously. 

 This rule is issued under 49 U.S.C. Section 44701 pursuant to the authority delegated to me 

by the Administrator, and is effective immediately upon receipt of this emergency AD. 

2010-11-52 SIKORSKY AIRCRAFT CORPORATION: Directorate Identifier 

2010-SW-059-AD. 

 Applicability: Model S-76A, B, and C helicopters, with LITEF LCR-100, part number (P/N) 

145130-7100, Attitude Heading and Reference System (AHRS) Unit, installed, certificated in any 

category. 

 Compliance: Within 5 days, unless accomplished previously, and any time thereafter when a 

LITEF LCR-100, part number (P/N) 145130-7100, Attitude Heading and Reference System (AHRS) 

Unit is installed. 

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 To prevent malfunction of the autopilot, inability to reset the autopilots, an uncommanded 

roll, reduction in rotorcraft functional capabilities, inability of the crew to perform the required tasks, 

and subsequent loss of control of the helicopter, do the following: 

 (a) Inspect the nameplate for the No. 1 and No. 2 AHRS units to determine if P/N 145130-

7100, Mod Status 18, is installed. 

 (1) If P/N 145130-7100, Mod Status 18, is not installed, no further action is required. 

(2) If P/N 145130-7100, Mod Status 18, is installed on either unit, accomplish the following: 

(i) 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. 

(ii) Insert an Active Temporary Revision into the Limitations section of the Rotorcraft Flight 

Manual (RFM) to limit the minimum flight crew to two pilots for Instrument Flight Rules and night 

flight for the affected helicopters as follows: 

Table 1 

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 

 (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, for information about previously 

approved alternative methods of compliance. 

 (c) The Joint Aircraft System/Component (JASC) Code is 3420: Navigation. 

 (d) Copies of the applicable service information 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. 

 (e) Emergency AD 2010-11-52, issued May 19, 2010, becomes effective upon receipt. 

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FOR FURTHER INFORMATION CONTACT: Tony Pigott, Aviation Safety Engineer, Boston 

Aircraft Certification Office, 12 New England Executive Park, Burlington, MA 01803, telephone 

(781) 238-7158, fax (781) 238-7170. 

Issued in Fort Worth, Texas, on May 19, 2010. 

Mark R. Schilling, 

Acting Manager, Rotorcraft Directorate, 

Aircraft Certification Service. 

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