(a) EFFECTIVE DATE
This Emergency AD is effective upon receipt.
(b) AFFECTED ADS
This AD applies to Cirrus Design Corporation Model SF50 airplanes, all
serial numbers, certificated in standard category.
Joint Aircraft System Component (JASC)/Air Transport Association (ATA)
of America Code 27; Flight Controls.
(e) UNSAFE CONDITION
This AD was prompted by Cirrus reporting three incidents of the stall
warning and protection system (SWPS) or Electronic Stability &
Protection (ESP) System engaging when not appropriate. The SWPS and
ESP may engage even when sufficient airspeed and proper angle of
attack (AOA) exists for normal flight. SWPS includes the stall warning
alarm, stick shaker and stick pusher. ESP includes under speed
protection (USP). The SWPS and ESP engaging could potentially result
in a STALL WARNING crew alert (CAS) message activation, accompanied by
an audio alarm and stick shaker activation, followed possibly by
either low speed ESP/USP engaging and/or the stick pusher engaging.
The pilot will also observe the dynamic and color-coded (Red) airspeed
awareness ranges displaying the stall band, regardless of actual
indicated airspeed. These conditions, if not addressed, could result
in the flight crew having difficulty controlling the airplane, lead to
excessive nose-down attitude, significant altitude loss, and possible
impact with terrain.
Comply with this AD within the compliance times specified, unless
(g) CORRECTIVE ACTION
(1) Before further flight after receipt of this emergency AD, replace the
AOA sensor with an improved AOA sensor, Aerosonic part number 4677-03
Mod 1 or Cirrus part number 32159-004 in accordance with section 11.
ACCOMPLISHMENT INSTRUCTIONS, paragraphs A, B, and C of Cirrus Design
Corporation SF50 Service Bulletin Number: SB5X-34-03, dated April 16,
(2) Before further flight after replacement of the AOA sensor per para-
graph (g)(1) of this AD, perform final installation checkout pro-
cedures and flight tests in accordance with a method approved by the
Manager, FAA, Chicago ACO Branch. For the checkout procedures and
flight test to be approved by the Manager, FAA, Chicago ACO Branch as
required by this paragraph, the Manager’s approval letter must
specifically refer to this AD.
(3) As of the effective date of this emergency AD, do not install any AOA
sensor on any affected airplane unless it is an improved AOA sensor as
identified in paragraph (g)(1) of this AD.
(h) SPECIAL FLIGHT PERMIT
A special flight permit is allowed with the following limitation:
Operators may fly the airplane to a location where the
modification/corrective action can be incorporated. However, the pilot
must follow the procedures listed in section 4., Pilot Actions
Required, in Cirrus SF50 Alert Service Advisory SA19-08, dated April
(i) ALTERNATIVE METHODS OF COMPLIANCE (AMOCS)
(1) The Manager, Chicago ACO Branch, FAA, has the authority to approve
AMOCs for this AD, if requested using the procedures found in 14 CFR
39.19. In accordance with 14 CFR 39.19, send your request to your
principal inspector or local Flight Standards District Office, as
appropriate. If sending information directly to the manager of the
certification office, send it to the attention of the person identi-
fied in paragraph (j)(1) of this AD.
(2) Before using any approved AMOC, notify your appropriate principal in-
spector, or lacking a principal inspector, the manager of the local
flight standards district office/certificate holding district office.
(j) RELATED INFORMATION
(1) For further information about this AD, contact: Wess Rouse, Small Air-
plane Program Manager, 2300 East Devon Avenue, Room 107, Des Plaines,
Illinois 60018; telephone: (847) 294-8113; fax: (847) 294-7834; email:
(2) For copies of the service information referenced in this AD, contact:
Cirrus Worldwide Headquarters, 4515 Taylor Circle, Duluth, Minnesota,
55811; telephone: (800) 921-2737 or after hours (800) 921-2737; fax:
(218) 788-3500; email firstname.lastname@example.org; Internet https:
//cirrusaircraft.com/service-support/. You may view this referenced
service information at the FAA, Small Airplane Standards Branch, 901
Locust, Kansas City, Missouri 64106. For information on the availabil-
ity of this material at the FAA, call (816) 329-4148.
Issued in Kansas City, Missouri, on April 18, 2019. Lance T Gant, Director
Compliance & Airworthiness Division, Aircraft Certification Service.
DATE: April 18, 2019
AD #: 2019-08-51
Emergency Airworthiness Directive (AD) 2019-08-51 is sent to owners and
operators of Cirrus Design Corporation (Cirrus) Model SF50 airplanes.
This emergency AD was prompted by Cirrus reporting three incidents on
Cirrus Model SF50 airplanes of the stall warning and protection system
(SWPS) or Electronic Stability & Protection (ESP) System engaging when
not appropriate, with the first incident occuring in November 2018 and
the latest in April 2019. The SWPS or ESP systems may engage even when
sufficient airspeed and proper angle of attack (AOA) exists for normal
flight. The SWPS includes the stall warning alarm, stick shaker, and stick
pusher. The ESP includes under speed protection (USP). The SWPS system
engaging inappropriately could potentially result in a STALL WARNING crew
alert (CAS) message activation, accompanied by an audio alarm and stick
shaker activation, followed possibly by either low speed ESP/USP engaging,
and/or the stick pusher engaging. The pilot will also observe the dynamic
and color-coded (Red) airspeed awareness ranges displaying the stall band,
regardless of actual indicated airspeed.
The information below presents information on each incident.
1. While the airplane was under manual pilot control, the airplane activated
several downward pitch commands coincident with stall warning, stick shaker,
and several associated alerts. The pilot reported "AOA FAIL" and "STICK
PUSHER FAIL CAS" messages preceding the pitch command. The pilot was able
to stop the automatic pitch commands by pressing and holding the autopilot
disconnect button in accordance with the emergency procedure in the airplane
flight manual and safely landed at his destination.
2. The operator reported stall warning and stick pusher failure in flight.
3. The airspeed indicator went red and the stall warning and stick shaker
were heard and felt while on descent. The autopilot was disengaged with
the same results. The system settled with stick pusher fail, stall warning
fail, and low speed awareness (LSA) fail under the airspeed. The pilot
hand flew the approach and had no VREF indicator but AOA appeared to be
Cirrus and Aerosonic (manufacturer of the technical standard order AOA
sensor) have identified the probable root cause as an AOA sensor malfunction
due to a quality escape in the assembly of the AOA sensor at Aerosonic.
Two set screws that secure the potentiometer shaft to the AOA vane shaft
may have improper torqueing and no application of thread locker (Loctite)
to secure the two set screws. The AOA sensor with this quality escape
is labeled with part number 4677-03.
Potential erroneous AOA derived indications may occur before, during,
and after unintended
automatic control system engagement. These indications include an abnormal
appearing low speed red band or VREF green donut presented on the airspeed
tape. Failed indications or intermittent indication may result in one
or more of the following:
• Unintended automatic flight control activations;
• The flight crew having difficulty controlling the airplane;
• Excessive nose-down attitude; and/or
• Possible impact with terrain.
Relevant Service Information
We reviewed Cirrus Design Corporation SF50 Service Bulletin Number: SB5X-34-03,
April 16, 2019 (SB5X-34-03). The service information provides instructions
for replacing the AOA sensor with an improved flight sensor.
We are issuing this AD because we evaluated all the relevant information
and determined the
unsafe condition described previously is likely to exist or develop in
other products of the same type design. The noted condition presents an
immediate danger to pilots and passengers of Cirrus Design Corporation
Model SF50 airplanes because an uncommanded pitch down may be difficult
to recover from in some flight regimes with potential fatal consequences.
The before further flight compliance time and need to replace the AOA
sensors due to the potential fatal consequences does not allow for prior
notice and opportunity to comment for the public.
This AD requires replacing the AOA sensors with improved AOA sensors using
instructions in SB5X-34-03.
Differences Between This AD and the Service Information
SB5X-34-03 specifies 5 hours time-in-service (TIS) before replacing the
AOA sensors. We
determined that allowing 5 hours TIS to replace the AOA sensors does not
mitigate the unsafe
condition; thus, this AD requires such replacement before further flight.
Authority for this Rulemaking
Title 49 of the United States Code specifies the FAA’s authority to issue
rules on aviation
safety. Subtitle I, Section 106, describes the authority of the FAA Administrator.
Aviation Programs, describes in more detail the scope of the Agency’s
We are issuing this rulemaking under the authority described in Subtitle
VII, Part A,
Subpart III, Section 44701, "General requirements." Under that section,
Congress charges the FAA with promoting safe flight of civil aircraft
in air commerce by prescribing regulations for practices, methods, and
procedures the Administrator finds necessary for safety in air commerce.
This regulation is within the scope of that authority because it addresses
an unsafe condition that is likely to exist or develop on products identified
in this rulemaking action.
Presentation of the Actual AD
We are issuing this AD under 49 U.S.C. Section 44701 according to the
authority delegated to me by the Administrator.