[Federal Register Volume 84, Number 127 (Tuesday, July 2, 2019)]
[Proposed Rules]
[Pages 31522-31524]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2019-14010]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2019-0470; Notice No. 25-19-10-SC]


Special Conditions: Gulfstream Aerospace Corporation Model GVII 
Series Airplane; Electro-Hydraulically Actuated Seats Equipped With 
Backup Power Supply

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed special conditions.

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SUMMARY: This action proposes special conditions for the Gulfstream 
Aerospace Corporation (Gulfstream) Model GVII series airplane. These 
airplanes, as modified by Gulfstream, will have a novel or unusual 
design feature when compared to the state of technology envisioned in 
the airworthiness standards for transport-category airplanes. This 
design feature is electro-hydraulically actuated seats equipped with 
backup power supply. The applicable airworthiness regulations do not 
contain adequate or appropriate safety standards for this design 
feature. These proposed special conditions contain the additional 
safety standards that the Administrator considers necessary to 
establish a level of safety equivalent to that established by the 
existing airworthiness standards.

DATES: Send comments on or before August 1, 2019.

ADDRESSES: Send comments identified by Docket No. FAA-2019-0470 using 
any of the following methods:
     Federal eRegulations Portal: Go to http://www.regulations.gov/ and follow the online instructions for sending 
your comments electronically.

[[Page 31523]]

     Mail: Send comments to Docket Operations, M-30, U.S. 
Department of Transportation (DOT), 1200 New Jersey Avenue SE, Room 
W12-140, West Building Ground Floor, Washington, DC 20590-0001.
     Hand Delivery or Courier: Take comments to Docket 
Operations in Room W12-140 of the West Building Ground Floor at 1200 
New Jersey Avenue SE, Washington, DC, between 9 a.m. and 5 p.m., Monday 
through Friday, except Federal holidays.
     Fax: Fax comments to Docket Operations at 202-493-2251.
    Privacy: The FAA will post all comments it receives, without 
change, to http://www.regulations.gov/, including any personal 
information the commenter provides. Using the search function of the 
docket website, anyone can find and read the electronic form of all 
comments received into any FAA docket, including the name of the 
individual sending the comment (or signing the comment for an 
association, business, labor union, etc.). DOT's complete Privacy Act 
Statement can be found in the Federal Register published on April 11, 
2000 (65 FR 19477-19478).
    Docket: Background documents or comments received may be read at 
http://www.regulations.gov/ at any time. Follow the online instructions 
for accessing the docket or go to Docket Operations in Room W12-140 of 
the West Building Ground Floor at 1200 New Jersey Avenue SE, 
Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, 
except Federal holidays.

FOR FURTHER INFORMATION CONTACT: Alan Sinclair, AIR-675, Airframe and 
Cabin Safety Section, Transport Standards Branch, Policy and Innovation 
Division, Aircraft Certification Service, Federal Aviation 
Administration, 2200 South 216th Street, Des Moines, Washington 98198; 
telephone and fax 206-231-3215; email [email protected].

SUPPLEMENTARY INFORMATION:

Comments Invited

    We invite interested people to take part in this rulemaking by 
sending written comments, data, or views. The most helpful comments 
reference a specific portion of the special conditions, explain the 
reason for any recommended change, and include supporting data.
    We will consider all comments we receive by the closing date for 
comments. We may change these special conditions based on the comments 
we receive.

Background

    On October 12, 2018, Gulfstream applied for a supplemental type 
certificate for electro-hydraulically actuated seats equipped with 
backup power supply in the Model GVII series airplane. The Gulfstream 
Model GVII series airplane, currently approved under Type Certificate 
No. T00021AT, is twin-engine, transport-category airplane with seating 
for 19 passengers and a maximum takeoff weight of 79,600 pounds.

Type Certification Basis

    Under the provisions of title 14, Code of Federal Regulations (14 
CFR) 21.101, Gulfstream must show that the Model GVII series airplane, 
as changed, continues to meet the applicable provisions of the 
regulations listed in Type Certificate No. T00021AT or the applicable 
regulations in effect on the date of application for the change, except 
for earlier amendments as agreed upon by the FAA.
    If the Administrator finds that the applicable airworthiness 
regulations (i.e., 14 CFR part 25) do not contain adequate or 
appropriate safety standards for the Gulfstream Model GVII series 
airplane because of a novel or unusual design feature, special 
conditions are prescribed under the provisions of Sec.  21.16.
    Special conditions are initially applicable to the model for which 
they are issued. Should the applicant apply for a supplemental type 
certificate to modify any other model included on the same type 
certificate to incorporate the same novel or unusual design feature, 
these special conditions would also apply to the other model under 
Sec.  21.101.
    In addition to the applicable airworthiness regulations and special 
conditions, the Gulfstream Model GVII series airplane must comply with 
the fuel-vent and exhaust-emission requirements of 14 CFR part 34, and 
the noise-certification requirements of 14 CFR part 36.
    The FAA issues special conditions, as defined in 14 CFR 11.19, in 
accordance with Sec.  11.38, and they become part of the type 
certification basis under Sec.  21.101.

Novel or Unusual Design Features

    The Gulfstream Model GVII series airplane will incorporate the 
following novel or unusual design features:
    Hydraulically actuated components on airplane seats, including 
hydraulic reservoir, pump, actuators, and backup power systems.

Discussion

    Hydraulically actuated components and backup power systems on 
airplane seats are considered novel or unusual by the FAA. Therefore, 
we developed special conditions that contain the additional standards 
that the Administrator considers necessary to establish a level of 
safety equivalent to that established by the existing airworthiness 
standards.
    The FAA has considered the installation of seats with these 
features to have four primary safety concerns:
    1. Reliability of the backup power supply;
    2. Safety hazards to the occupants from the hydraulically actuated 
components of the seat;
    3. Structural integrity of the hydraulic components; and
    4. Flammability.
    Emergency exits must be accessible to the passengers, and the 
effectiveness of evacuation must be maintained. Typical airplane seats 
can be positioned manually to the lateral (track) and directional 
(swivel) taxi, takeoff, and landing (TT&L) position by mechanical 
means, so that the seats can be positioned accordingly in the event of 
a loss of cabin power. For this electro-hydraulically operated seat 
design, in lieu of a manual means to re-position the hydraulically 
operated seat features (backrest, seat pan, and leg-rest deployment) 
for TT&L, a backup power supply (BPS) temporarily powers the hydraulic 
system in the event of loss of cabin power. The BPS is deployed, and 
intended only for use, in the event of a loss of cabin power. If the 
seats are installed in the path of the emergency over-wing exits, 
failure to return the seat to a TT&L position may have an adverse 
effect on evacuation. Substantiation of 14 CFR 25.809(b) and 
25.813(c)(2)(ii) must be shown with the seats in their most adverse 
positions.
    It must be shown that the hydraulically actuated components of the 
seat pose no safety hazard to the occupants or airplane. This includes 
injuries caused by crushing of airplane occupants who are between the 
hydraulically actuated components and any part of the passenger cabin 
when seat features (e.g., leg rest or backrest) are actuated. 
Additionally, the risk of loss of function of a control or proximity 
switch, resulting in the pump motor commanded to remain pumping after 
the hydraulic actuator(s) have reached their minimum or maximum limit, 
must not cause the overloaded motor to overheat, a condition that could 
result in fire.
    The FAA has also considered the emergency-landing dynamic 
conditions

[[Page 31524]]

for the installation of electro-hydraulically actuated seats. The 
applicant must show that the hydraulic system (actuators, reservoir, 
lines, etc.) remains intact and free from leakage under the conditions 
specified in Sec.  25.562. Testing of each seat's hydraulic system per 
Sec.  25.1435(c) may be conducted off of the airplane.
    Flammability of hydraulic fluid used in the seat-movement mechanism 
must be considered. If the fluid is flammable, it could contribute to a 
post-crash or in-flight fire. Any failure modes that would result in 
release of the flammable hydraulic fluid during a post-crash or in-
flight fire, causing such fluid to materially increase an existing 
fire, must be examined. Examples of this could be flex lines burning 
through and releasing the flammable hydraulic fluid, or the fluid 
reservoir could be heated in a fire, resulting in a boiling-liquid, 
expanding-vapor explosion. The potential for spontaneous ignition of 
the fluid coming into contact with hot surfaces or other ignition 
sources should also be addressed. The applicant should examine any 
possible failure mode in which the flammable hydraulic fluid could be 
absorbed into materials, such as the seat foam and fabric, carpeting, 
etc. The applicant must show that any fluid-soaked seat parts remain 
self-extinguishing. The applicant must also show that flammability of 
dry residue, which may be present from a slow leak or fluid seepage, 
does not degrade the flammability characteristics of any materials the 
fluid contacts, to a level below the requirements specified in Sec.  
25.853.
    These proposed special conditions contain the additional safety 
standards that the Administrator considers necessary to establish a 
level of safety equivalent to that established by the existing 
airworthiness standards.

Applicability

    As discussed above, these proposed special conditions are 
applicable to the Gulfstream Model GVII series airplane. Should 
Gulfstream apply at a later date for a supplemental type certificate to 
modify any other model included on Type Certificate No. T00021AT to 
incorporate the same novel or unusual design feature, these special 
conditions would apply to that model as well.

Conclusion

    This action affects only certain novel or unusual design features 
on one model series of airplane. It is not a rule of general 
applicability and affects only the applicant who applied to the FAA for 
approval of these features on the airplane.

List of Subjects in 14 CFR Part 25

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.

Authority Citation

    The authority citation for these special conditions is as follows:

    Authority:  49 U.S.C. 106(f), 106(g), 40113, 44701, 44702, 
44704.

The Proposed Special Conditions

    Accordingly, the Federal Aviation Administration (FAA) proposes the 
following special conditions as part of the type certification basis 
for Model GVII series airplanes modified by Gulfstream Aerospace 
Corporation.
    1. It must be shown that the probability of failure of the backup 
power supply to return seat components to the required taxi, takeoff, 
and landing position is no greater than 10-5 per flight 
hour.
    2. It must be shown that the hydraulically actuated components of 
the seat pose no safety hazard to the occupants. Hazards to be 
considered, per the latest revision of Advisory Circular 25.1309-1, at 
a minimum are:
    a. Injuries caused by crushing of airplane occupants who are 
between the hydraulically actuated components and any part of the 
passenger cabin when the leg rest or backrest is actuated.
    b. The risk of loss of function of a control or proximity switch 
resulting in the pump motor being commanded to stay on after the 
hydraulic actuator(s) have reached their minimum or maximum limit, 
creating potential for motor overheating or fire.
    c. The potential for a significant contribution to a fire in the 
event fluid comes into contact with hot surfaces or other ignition 
sources, and the potential for release of toxic or flammable vapors and 
gasses.
    3. It must be shown that the hydraulic system (actuators, 
reservoir, lines, etc.) remains intact and free from leakage under the 
conditions specified in Sec.  25.562. Testing of each seat's hydraulic 
system per Sec.  25.1435(c) may be conducted off of the airplane.
    4. Section 25.863 requires consideration of any effects the 
hydraulic fluid, including the fluid as a dry residue, could have on 
combustible or absorbing materials. The characteristics of such 
flammable fluid in these conditions must be tested to the requirements 
of Sec.  25.853(a) and (c), or the materials must be shielded in a 
manner that prevents contact by the fluid. However, as an alternative 
to such testing or shielding, the applicant may provide, in accordance 
with Sec.  25.863(c), a quick-acting means that alerts the crew that 
hydraulic fluid has leaked.

    Issued in Des Moines, Washington, on June 21, 2019.
Christopher R. Parker,
Acting Manager, Transport Standards Branch, Policy and Innovation 
Division, Aircraft Certification Service.
[FR Doc. 2019-14010 Filed 7-1-19; 8:45 am]
BILLING CODE 4910-13-P