[Federal Register Volume 84, Number 156 (Tuesday, August 13, 2019)]
[Rules and Regulations]
[Pages 39959-39960]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2019-17257]



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 Rules and Regulations
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  Federal Register / Vol. 84, No. 156 / Tuesday, August 13, 2019 / 
Rules and Regulations  

[[Page 39959]]



DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2019-0470; Special Conditions No. 25-754-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: Final special conditions.

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SUMMARY: These special conditions are issued 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 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: Effective August 13, 2019.

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:

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)

[[Page 39960]]

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 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 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.

Discussion of Comments

    The FAA issued Notice of Proposed Special Conditions No. 25-19-10-
SC for the Gulfstream Model GVII series airplane, which was published 
in the Federal Register on July 2, 2019 (84 FR 31522). No comments were 
received, and the special conditions are adopted as proposed.

Applicability

    As discussed above, these 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 Special Conditions

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the following special conditions are issued as part of 
the type certification basis for Gulfstream Aerospace Corporation Model 
GVII series airplanes.
    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 August 7, 2019.
Christopher R. Parker,
Acting Manager, Transport Standards Branch, Policy and Innovation 
Division, Aircraft Certification Service.
[FR Doc. 2019-17257 Filed 8-12-19; 8:45 am]
 BILLING CODE 4910-13-P