Aircraft
Certification Service Washington, DC U.S. Department of Transportation Federal Aviation Administration
CE-16-23
September 7, 2016
This is information only. Recommendations
aren’t mandatory.
Introduction
This Special Airworthiness Information Bulletin is being issued to
alert Title 14 of the Code of Federal Regulations (14 CFR) part 91, 91
Subpart K, and 135 operators of an airworthiness concern on Embraer
S.A. Model EMB-505 airplanes. Specifically, operators should be aware
of possible degraded attitude and heading reference system (AHRS)
performance when operating in areas of unreliable or unavailable global
positioning system (GPS) signal.
In addition, this SAIB is being issued to alert operators of the
Brazilian Agencia National De Aviacao Civil (ANAC) Special
Airworthiness Bulletin (SAB) No. 2016-01 dated April 13, 2016, Embraer
S.A. Operational Bulletin (OB) No. 505-002/16 dated April 13, 2016,
Embraer S.A. Flight Operations Letter No. FOL PHE505-006/16 dated July
01, 2016, and recent changes (Revision 13) to EMB-505 Quick Reference
Handbook (QRH)-2668-02. All of these items relate to the subject matter
of this SAIB.
At this time, this airworthiness concern is not considered an unsafe
condition that would warrant airworthiness directive (AD) action under
14 CFR part 39.
Background
The United States (U.S.) Department of Defense regularly conducts tests
on GPS signals in different regions around the U.S. national airspace
system (NAS). A published Notice to Airmen (NOTAM) precedes these
tests. The NOTAM advises pilots that the expected level of service may
not be available. The FAA has become aware of situations where Model
EMB-505 airplanes operating in areas where GPS was unreliable or
unavailable have resulted in AHRS 1 and 2 FAULT crew alerting system
(CAS) messages, which were shortly followed by ventral rudder control
(VRC), yaw damper (YD), and Autopilot (AP) FAIL CAS messages, and a
stall warning protection system (SWPS) FAULT CAS message. The airplane
flight manual (AFM) and QRH procedures for these failures require
descending the airplane to flight level (FL) 250 or below. The AFM and
QRH procedures also indicate that lateral/directional oscillations may
occur. This combination of system failures, the required descent, and
the Dutch roll exhibited by the airplane have caused Model EMB-505
airplane pilots to declare an emergency and divert to unplanned
airports.
The ANAC SAB No. 2016-01 and Embraer S.A. OB No. 505-002/16 specified a
new flight crew procedure for simultaneous AHRS 1 and 2 FAULT white CAS
messages. This information was incorporated in a recent revision to the
Model EMB-500 QRH, which resulted in Embraer removing the OB from the
online publication. The procedure requires the pilot to reduce airplane
airspeed to MAX 240 knots indicated airspeed (KIAS) / 0.63 Mach (M),
which is intended to prevent the consequent failure of the VRC, YD, and
AP, and fault of the SWPS. This prevention of consequent failures and
associated CAS messages would alleviate the requirement for abnormal
procedures involving descents and Dutch roll mitigations. ANAC has
indicated that if the AHRS 1 and AHRS 2 FAULT messages clear, then
normal airspeed can be resumed.
In addition, to minimize possible disruptions to air traffic control
(ATC) resulting from unplanned airspeed reductions, Embraer S.A. has
now released Flight Operations Letter (FOL) No. FOL PHE505-006/16 to
recommend that pilots limit their airspeed to 375 knots true airspeed
(KTAS) when filing their flight plans for areas outlined in the NOTAMs
for GPS interference testing. It is noted that this instruction is for
flight planning only and the airspeed limits of 240 KIAS/0.63 M should
be observed when actually flying in the areas outlined in the NOTAMs
for GPS interference testing.
Recommendations
The FAA recommends the following:
Become familiar with the
recently added QRH procedures for AHRS 1 and 2 FAULT CAS messages,
which are referenced within the ANAC Special Airworthiness Bulletin No.
2016-01 and the now incorporated, Embraer S.A. OB No. 505-002/16.
Before operating any Model
EMB-505 airplane, become familiar with GPS NOTAMs applicable to your
route of flight and determine what level of service is available for
the planned flight as indicated in FAA Advisory Circular AC 90-105A,
Chapter 9.
During flight planning,
become familiar with Embraer S.A. Flight Operations Letter No. FOL
PHE505-006/16 and plan to limit your airspeed to 375 KTAS when
operating in NOTAM testing areas during the testing hours.
During flight operations,
remain vigilant for AHRS 1 FAULT and AHRS 2 FAULT CAS messages
displayed simultaneously and, if this happens, then immediately follow
the QRH procedure as indicated.
If any CAUTION CAS message is displayed, follow the appropriate QRH procedure.
Report unexpected GPS
anomalies, including degraded operation and/or loss of service, as soon
as possible, following Aeronautical Information Manual paragraph 1−1−13.
For Further Information Contact
Jim Rutherford, Aerospace Engineer, 901 Locust Room 301, Kansas City,
MO 64106; phone: (816) 329-4165; fax: (816) 329-4090; e-mail:
jim.rutherford@faa.gov.