FAA SPECIAL AIRWORTHINESS
Aviation Safety INFORMATION BULLETIN
SAIB: CE-17-19
SUBJ: Cabin Altitude Encoder – Installation Evaluation Date: June 22, 2017
This is information only. Recommendations aren’t mandatory.
Introduction
This Special Airworthiness Information Bulletin (SAIB) alerts you, owners and operators of all
airplanes with cabin altitude encoder Sandia SAE5-35 or Garmin GAE 43 installed, of an
airworthiness concern on certain installation configurations of the encoder. The encoder provides
altitude information to avionics displays. We are recommending you evaluate the configuration of
your installation of the encoder.
At this time, this airworthiness concern has not been determined to be an unsafe condition that would
warrant AD action under Title 14 of the Code of Federal Regulations (14 CFR) part 39.
Background
As discussed in AD 2015-13-09, we received a report of an airplane that experienced a pitch control
system problem resulting in a limited ability to control the elevator. The investigation revealed that
an avionics box installed behind the instrument panel had fallen into the elevator control sector and
jammed the primary pitch control.
The AD was issued to address the specific location and installation configuration on certain Piper
airplanes. We have continued to investigate other installations of the cabin altitude encoder that might
have a similar configuration. The encoder is supplied as either SAE5-35 from Sandia under technical
standard order (TSO) C88a, or as GAE 43 from Garmin under a parts manufacturer approval (PMA).
See Figure 1 for a view of the encoder and Figure 2 for a diagram of the mounting assembly.
Figure 1 Figure 2
Other installations of the encoder could have occurred through several means such as part of a type
certificate (TC), supplemental type certificate (STC), or field approval. The typical installation of the
cabin altitude encoder would be “right side up” (as shown in Figure 2). In that configuration, gravity
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would retain the encoder if the retaining fastener fails. Also, the encoder should be installed away
from any systems that would have a direct impact on safety of flight. For instance, a typical location
would be on a rack in an avionics shelf or bay. Prior to the AD, no adverse service history had been
reported.
For reference, the TSO and PMA installation manual states that the encoder can be mounted in any
axis. This is true as far as operation of the encoder itself is concerned, since a TSO only focuses on
the performance requirements of the article itself. Airplane product safety, however, depends not only
on the components installed, but the details of the installation. In the case of the AD, the encoder was
installed:
• Upside down • Behind the instrument panel
• Directly above a critical flight • Lacking additional locking features on the
control system retaining fastener
As demonstrated in the AD, the typical installation assumptions can be changed to create an improper
configuration with increased risk. Sandia has revised the encoder installation manual to include a
caution addressing the location and configuration of the installation. They have also designed an
alternate mount assembly to address such configurations and referenced the new mount assembly in
the manual.
Recommendations
The FAA recommends that owners and operators of airplanes with cabin altitude encoder SAE5-35
(Sandia) or GAE 43 (Garmin) installed, evaluate the configuration of your installation. You may use
the background information provided above as a reference for considerations that could lead to an
improper installation. We also recommend you evaluate use of the alternate mount assembly
referenced in the revised Sandia installation manual to mitigate improper configurations.
For Further Information Contact
Gregory K. (“Keith”) Noles, Aerospace Engineer, Atlanta ACO, 1701 Columbia Ave., College Park,
GA 30337; phone: (404) 474-5551; fax: (404) 474-5606; email:
[email protected]
For Related Service Information Contact
Sandia Aerospace, 3700 Osuna Rd. NE, Suite 711, Albuquerque, NM 87109;
website: http://sandia.aero/
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Please find attached a Foreign State of Design Advisory document, endorsed by EASA.
This advisory document is also online at https://ad.easa.europa.eu/ad/CE-17-19 .
Should you have any questions, please contact the Agency by e-mail at
[email protected] or by fax,
No.: +49 221 89990 9515.
Safety Information Section Email:
[email protected]
EASA Website
(Attachment is in Acrobat PDF format)
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