[Federal Register Volume 62, Number 200 (Thursday, October 16, 1997)]
[Rules and Regulations]
[Pages 53733-53737]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-27504]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 23
[Docket No. 136CE, Special Condition 23-ACE-88]
Special Conditions; Ballistic Recovery Systems Cirrus SR-20
Installation
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final special conditions.
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SUMMARY: These special conditions are being issued to become part of
the type certification basis for the Ballistic Recovery Systems, Inc.,
(BRS) parachute recovery system installed in the Cirrus SR-20 Model
airplane. This system is referred to as the General Aviation Recovery
Device (GARD). Airplanes modified to use this system will incorporate
novel or unusual design features for which the applicable airworthiness
regulations do not contain adequate or appropriate safety standards.
These special conditions contain the additional airworthiness standards
that the Administrator considers necessary to establish a level of
safety equivalent to the original certification basis for these
airplanes.
EFFECTIVE DATE: November 17, 1997.
FOR FURTHER INFORMATION CONTACT: Lowell Foster, Aerospace Engineer,
Standards Office (ACE-110), Small Airplane Directorate, Aircraft
Certification Service, Federal Aviation Administration, 601 East 12th
Street, Kansas City, Missouri 64106; telephone (816) 426-5688.
SUPPLEMENTARY INFORMATION:
Background
On March 7, 1996, Cirrus Design, 4515 Taylor Circle, Duluth, MN
55811, filed an application for a type certificate (TC). Included in
this TC application was the provision to install the BRS GARD parachute
recovery system as standard equipment on each Cirrus Model SR-20
airplane. The parachute recovery system is intended to recover an
airplane in emergency situations such as mid-air collision, loss of
engine power, loss of airplane control, severe structural failure,
pilot disorientation, or pilot incapacitation with a passenger on
board. The GARD system, which is only used as a last resort, is
intended to prevent serious injuries to the airplane occupants by
parachuting the airplane to the ground.
The parachute recovery system consists of a parachute packed in a
canister mounted on the airframe. A solid propellant rocket motor
deploys the canopy and is located on the side of the canister. A door
positioned above the canister seals the canister, parachute canopy, and
rocket motor from the elements and provides free exit when the canopy
is deployed. The system is deployed by a mechanical pull handle mounted
so that the pilot and passenger can reach it. At least two separate and
[[Page 53734]]
independent actions are required to deploy the system.
A multi-cable bridle attaches the canopy bridle to the airplane
primary structure. The cable lengths are sized to provide the best
airplane touchdown attitude. The cables are routed from the parachute
canister thru the fuselage and run externally to the fuselage attach
points. The external portion of these cables are covered with small
frangible fairings.
Type Certification Basis
The type certification basis for the Cirrus Model SR-20 is as
follows: 14 CFR part 23, effective February 1, 1965, including
Amendments 23-1 through 23-47; 14 CFR part 36, effective December 1,
1969, including Amendments 36-1 through the amendment in effect at the
time of U.S. certification; Equivalent Level of Safety Findings;
Exemptions approved by the FAA (14 CFR part 11, Sec. 11.27; Section
611(b) of the FAA Action of 1958 (49 U.S.C. 44715); and the special
conditions adopted by this rulemaking action.
Discussion
Special conditions may be issued and amended, as necessary, as part
of the type certification basis if the Administrator finds that the
airworthiness standards designated in accordance with 14 CFR part 21,
Sec. 21.16 do not contain adequate or appropriate safety standards
because of the novel and unusual design features of the airplane
modification. Special conditions, as appropriate, are issued after
public notice in accordance with Sec. 11.49 (as amended September 25,
1989), as required by Secs. 11.28 and 11.29(b). The special conditions
become part of the type certification basis, as provided by
Sec. 21.17(a)(2).
The installation of parachute recovery systems in 14 CFR part 23
airplanes was not envisioned when the certification basis for these
airplanes was established. In addition, the Administrator has
determined that current regulations do not contain adequate or
appropriate safety standards for a parachute recovery system;
therefore, this system is considered a novel and unusual design
feature. The flight test demonstration requirements will ensure that
the parachute recovery system will perform its intended function
without exceeding its strength capabilities. Demonstrations will be
required to show that the parachute will deploy in specified flight
conditions. These conditions are a minimum of maneuvering speed,
VO or higher, and deployment during a one-turn spin entry.
If the airplane does not depart , the condition is the maneuver that
results from pro-spin control inputs held for one turn, or three
seconds, whichever comes first.
Occupant restraint requirements will ensure that the airplane is
equipped with a restraint system designed to protect the occupants from
injury during parachute deployment and ground impact. Each occupant
seat must meet the requirements of 14 CFR part 23, Sec. 23.562 as part
of the original certification basis.
Requirements for parachute performance will ensure all of the
following: (a) The parachute complies with the applicable section of
TSO-C23c (SAE AS8015A) at the maximum airplane weights. (b) The
parachute deployment loads do not exceed the structural strength of the
airplane. (c) The system will provide a ground impact that does not
result in serious injury of the passengers. (d) The system will operate
in adverse weather conditions.
The requirements for the functions and operations of the parachute
recovery system will ensure all of the following: (a) There is no fire
hazard associated with the system. (b) The installation of this system
allows relief from another part 23 requirement, spins. For this reason,
it will need to be operational for all flights. (c) That the system
will work in all weather conditions that the airplane is approved to
operate in, including the IFR and icing environments. (d) The sequence
of arming and activating the system will prevent inadvertent
deployment. (e) The system can be activated from either the pilot's or
the copilot's position by various sized people. (f) The system will be
labeled to show its identification function and operating limitations.
(g) A warning placard will be located on the fuselage near the rocket
motor to warn rescue crews of the ballistic system. (h) The FAA-
approved flight manual will include a thorough explanation of system's
operation and limitations as well as the safe deployment envelope. (i)
The occupants are protected from serious injury after touchdown in
adverse weather.
Requirements for protection of the parachute recovery system will
ensure the following: the system is protected from deterioration due to
weathering, corrosion, and abrasion; provisions are made to provide
adequate ventilation and drainage of the airplane structure that houses
the parachute canister.
Requirements for a system inspection provision will ensure that
adequate means are available to permit examination of the parachute
recovery system components and that instructions for continued
airworthiness are provided.
Requirements for operating limitations of the parachute recovery
system will ensure that the system operating limitations and deployment
envelope are prescribed, including inspection, repacking, and replacing
the system's parachute deployment mechanism at approved intervals.
Discussion of Comments
Notice of Proposed Special Conditions, Notice No. 23-ACE-88, Docket
No. 136CE was published in the Federal Register on February 6, 1997,
and the comment period closed March 10, 1997. Following is a summary of
the comments received and a response to each comment.
Only one commenter responded to the notice and that was Cirrus
Design. They offered five comments, all of which are addressed below.
1. Comment. Paragraph 1(a). Proposed Special Condition, Docket No.
136CE, 23-ACE-88 does not contain provisions for the flight test
demonstration to be conducted on an aircraft having similar
characteristics as was accepted for Docket No. 118CE, 23-ACE-76,
Special Conditions: Ballistic Recovery Systems, Modified for Small
General Aviation Aircraft. Cirrus proposes to modify the current
language of 1(a) to include: ``The system may be demonstrated on an
aircraft having similar characteristics (such as configuration, weight,
and speed) and similar installation.'' The crucial elements here are
the mass distribution of the aircraft and center of gravity (moment of
inertia), the location of the riser attachments relative to the c.g.,
and the riser configurations. The flight demonstration is conclusive if
these elements are similar. An example of this situation would be that
of demonstrating the operation of the recovery system in a development
prototype aircraft similar to that of the type design aircraft. It is
only a matter of necessary conformity and degree of similarity. The
allowance for ``similar'' aircraft flight demonstration is a logical
inclusion and will require a case by case review. This provision was
found acceptable for 23-ACE-76 and, therefore, is acceptable for any
STC installations. A TC application should not, by law, require more
stringent conditions.
FAA Response. The special conditions for BRS installations referred
to by Cirrus; 23-ACE-76, Docket No. 118CE, were originally intended for
airplanes similar to the Quicksilver GT-500 and they were intended for
general applicability for certificated small
[[Page 53735]]
airplanes. The Cirrus special conditions do not include this provision
because they are unique to the model SR-20. On a model specific special
condition, general applicability items are not appropriate. This does
not imply that minor design variations in the model would require
additional testing.
The FAA agrees that the crucial elements are mass distribution,
moment of inertia, riser attachments and configurations. If these
crucial elements remain essentially constant with minor design
variation, then credit for GARD testing should apply to both airplanes.
This issue has been adequately addressed in this preamble and no change
in the special conditions is necessary.
2. Comment. Paragraph 1(b)(2). It is recommended that item 1(b)(2)
be changed to: ``maximum allowable deployment speed with 1g normal
load.'' The use of this type of safety equipment is in its infancy and
analytical predictions of deployment dynamics are challenging. Based on
this, the loads used in the design phase are estimations based on the
best information available. The actual loads are determined during
flight testing and fix the maximum allowable deployment speed that the
designed structure can withstand. A requirement for a system to be
deployed at VNE not only offers extreme risk within a
development and certification program, but also extends beyond that
which is necessary to offer increased safety to the pilot and
passengers for the portion of the flight envelope reflecting the
largest numbers of accidents. This equipment is provided to give the
pilot an additional option for recovery in a critical situation. The
deployment envelope should be clearly placarded; beyond which point
system operation is prohibited/not recommended. However, the mere
presence of the equipment does offer a certain increase in safety. This
option to the pilot should not be totally withdrawn because of the
potential inability of the system to be deployed at VNE. In
order to use the GARD system for the spin ELOS, the system need only be
safely deployed in a spin situation. Deployments at any other time are
an increase in safety above that which is required by FARs.
This requirement also significantly affects customer value. Not all
aircraft [especially high performance] can offer this equipment with
V5NE envelope capability while maintaining an overall
aircraft value/utility, due to the severe structural requirements
(energy as the square of the velocity). Should pilots of these aircraft
be denied the use of this equipment when in a critical low speed
situation? As a final note, a maximum deployment speed other than
VNE was found to be acceptable for the GARD 150 program,
which also began with a VNE requirement, 23-ACE-33, Special
Conditions: Ballistic Recovery System, Inc., Modified Cessna 150/A150
Series Airplanes and 152/A152 Model Airplanes to Incorporate the GARD-
150 System.
FAA Response. The FAA developed the original special conditions for
the Ballistic Recovery System GARD-150 System based on what was
believed to be appropriate at that time. Ideally, it is desirable for
any safety device to operate over the entire flight envelope of the
airplane it is installed in. Based on this ideal, the original special
conditions were intended to cover operation from stall to
VNE. Prior to the Cessna 150 STC installing the GARD-150,
the typical airplanes that installed a ballistic parachute recovery
system could use the system over the entire flight envelope because
they were very light, low performance vehicles. The Cirrus SR-20 is a
heavy, high performance airplane by comparison. There are challenging
technical issues to address with this installation, one of them is the
maximum demonstrated deployment speed.
Cirrus is installing the BRS GARD system not only for general
safety improvements but also for relief from the spin recovery
demonstrations required by part 23. The FAA agrees with Cirrus that a
requirement for deployment at VNE is not relative to a
requirement for an equivalent safety finding for spin recovery. The
FAA, however, disagrees with Cirrus's recommended change because it is
open ended, allowing any speed above stall to meet the special
condition.
The introduction of innovative safety devices, such as ballistic
parachute recovery systems, is important to the FAA's goal of reducing
fatal accidents. For this reason, the FAA met with representatives from
Cirrus to discuss the maximum deployment demonstration issue. Cirrus'
concern, as expressed in their comments, focuses on the risk of
developing the system that will safely deploy throughout most of the
airplane's speed range, falling just short of VNE and,
hence, not receiving approval to install the system in their airplane.
Furthermore, Cirrus argues that the mere presence of the GARD system
offers a certain increase in safety; therefore, specifying a maximum
deployment speed that may not be achievable risks negating the GARD
system installation. This action would not be in the best interest of
safety.
It is important to understand that this issue does not concern
operational deployment by pilots directly. It addresses the deployment
tests required by this special condition for certification. The test
airplane used for the GARD system deployments must be safely used for
multiple deployments. This means that the airplane must remain
airworthy after GARD system deployment so that the parachute can be cut
away and the airplane safely landed. In operational use, the airplane
does not need to remain airworthy after parachute deployment because it
is committed to returning to the ground. Once the parachute is deployed
in operation, the airplane is going to the ground and probably will not
be in an airworthy condition after the landing. Moreover, the FAA
should be clear that our concern is that of occupant safety. If the
initial opening shock of the GARD system fails parts of the airframe,
that is acceptable as long as the occupants meet the safety
requirements of these special conditions. The point of this discussion
is that an acceptable operational deployment of the GARD system may not
be acceptable in the flight test deployment case because the airplane
could sustain serious damage, preventing the completion of the flight
test program.
After discussing all technical points and positions, the FAA agreed
that the appropriate course was to require a maximum deployment speed
based on the equivalent safety finding. The equivalent safety finding
provides relief from the spin recovery demonstration requirements of
Sec. 23.221. The entry requirement for a spin is a stall; therefore,
the FAA determined that an acceptable maximum demonstrated deployment
speed for the GARD system must be at least VO, the maximum
speed at which, with a full deflection control input, the airplane will
stall before reaching limit load on the airframe. This will provide
adequate margin for the safe application of the equivalent safety
finding and reduce Cirrus' concern that their GARD system installation
would not be approved. The FAA also acknowledges that it is Cirrus'
goal to push the GARD system deployment speed as high as possible
within practical constraints.
3. Comment. Paragraph 3(b). It is suggested that this paragraph
include ``and the parachute assembly.''
FAA Response. The FAA agrees and will incorporate the comment.
4. Comment. Paragraph 4(b). This paragraph states that a ``system
failure must be shown to be extremely improbable.'' Previous
requirements for this type of system, reference 23-ACE-
[[Page 53736]]
76, cited that the system, ``must be shown to function reliably and to
perform its intended function.''
The previous requirements were appropriate for equipment that
increases the level of safety of the airplane. Reliability of
``extremely improbable,'' as defined in AC 23-1309, cannot be
reasonably shown quantitatively. The system, as designed, can deliver
functional reliability. The testing required on incipient spin recovery
will not quantify a demonstration of ``extremely improbable.''
The critical firing system is designed with similar methodology as
redundant load path structure. There are two firing primers, where only
one is necessary for ignition of the rocket. The remainder of the
system is mechanical in nature with few parts. The following is offered
as a possible change to the wording: ``activation system must be shown
to function reliably [such as redundant ignition sources] and to
perform its intended function.''
FAA Response. The FAA agrees in principle with Cirrus' comments
concerning reliability. The following changes are included in these
special conditions.
``Discussion'' section:
The probability that the system will operate as designed is very
high.
``Special Conditions'' section:
The system must be shown to perform its intended function with a
high probability that it will operate as designed.
5. Comment. Paragraph 7(b). Based on the comments of Paragraph
1(b)(2) above, it is also recommended that 7(b) be removed from this
special condition. Again, the ELOS does not maintain applicability to
the high speed portion of the flight envelope and, therefore, the
equipment should not be required to operate in this speed range.
FAA Response. Addressed in the earlier discussion concerning
deployment demonstration at VNE.
Conclusion
The following special conditions are issued for the Cirrus SR-20
airplane. This action affects only novel and unusual design features on
specified model/series airplanes. It is not a rule of general
applicability and affects only those applicants who apply to the FAA
for approval of these features on these airplanes.
List of Subjects in 14 CFR Part 23
Aircraft, Aviation safety, and Signs and Symbols.
Citation
The authority citation for this special condition is as follows:
Authority: 49 U.S.C. 106(g), 40113 and 44701; 14 CFR 21.16 and
101; and 14 CFR 11.28 and 11.49.
Adoption of Special Conditions
Accordingly, pursuant to the authority delegated to me by the
Administrator, the Federal Aviation Administration issues the following
special conditions as part of the type certification basis for the
Cirrus Model SR-20 airplanes:
1. Flight Test Demonstration
(a) The system must be demonstrated in flight to satisfactorily
perform its intended function, without exceeding the system deployment
design loads, for the critical flight conditions.
(b) Satisfactory deployment of the parachute must be demonstrated,
at the most critical airplane weight and balance, for the following
flight conditions:
(1) One of the two maneuvers, (i) or (ii), must be performed for
the low speed end of the flight envelope;
(i) Spin with deployment at one turn or 3 seconds, whichever is
longer; or
(ii) Deployment immediately following the maneuver that results
from a pro-spin control input held for one turn or 3 seconds, whichever
is longer.
(2) A minimum of maneuvering speed, VO or higher;
2. Occupant Restraint.
Each seat in the airplane must be equipped with a restraint system,
consisting of a seat belt and shoulder harness, that will protect the
occupants from head and upper torso injuries during parachute
deployment and ground impact at the critical load conditions.
3. Parachute Performance
(a) The parachute must comply with the applicable requirements of
TSO-C23c, or an approved equivalent, for the maximum airplane weight at
paragraph 1(b)(2).
(b) The loads during deployment must not exceed 80 percent of the
ultimate design load for the attaching structure, the cabin structure
surrounding the occupants, and any interconnecting structure of the
airplane.
(c) It must be shown that, although the airplane structure may be
damaged, the airplane impact during touchdown will result in an
occupant environment in which serious injury to the occupants is
improbable.
(d) It must be shown that, with the parachute deployed, the
airplane can impact the ground in various adverse weather conditions,
including winds up to 15 knots, without endangering the airplane
occupants.
4. System Function and Operations
(a) It must be shown that there is no fire hazard associated with
activation of the system.
(b) The system must be shown to perform its intended function with
a high probability that it will operate as designed.
(c) It must be shown that reliable and functional deployment in the
adverse weather conditions that the airplane is approved for have been
considered. For example, if the aircraft is certified for flight into
known icing, and flight test in actual icing reveals that ice may cover
the deployment area, then the possible adverse effects of ice or an ice
layer covering the parachute deployment area should be analyzed.
(d) It must be shown that arming and activating the system can only
be accomplished in a sequence that makes inadvertent deployment
extremely improbable.
(e) It must be demonstrated that the system can be activated
without difficulty by various sized people, from a 10th percentile
female to a 90th percentile male, while sitting in the pilot or copilot
seat.
(f) The system must be labeled to show its identification,
function, and operating limitations.
(g) A warning placard must be located on the fuselage near the
rocket motor warning of the rocket.
(h) The FAA-approved flight manual must include a thorough
explanation of operation and limitations as well as the safe deployment
envelope.
(i) It must be shown that the occupants will be protected from
serious injury after touchdown under various adverse weather
conditions, including high winds.
5. System Protection
(a) All components of the system must provide protection against
deterioration due to weathering, corrosion, and abrasion.
(b) Adequate provisions must be made for ventilation and drainage
of the parachute canister and associated structure to ensure the sound
condition of the system.
6. System Inspection Provisions
(a) Instructions for continued airworthiness must be prepared for
the system that meet the requirements of Sec. 23.1529.
(b) Adequate means must be provided to permit the close examination
of the parachute and other system components to ensure proper
functioning, alignment,
[[Page 53737]]
lubrication, and adjustment during the required inspection of the
system.
7. Operating Limitations
(a) Operating limitations must be prescribed to ensure proper
operation of the system within its deployment envelope. A detailed
discussion of the system, including operation, limitations and
deployment envelope must be included in the Airplane Flight Manual.
(b) The deployment envelope of the GARD system must be possible at
speeds up to VO or higher.
(c) Operating limitations must be prescribed for inspecting,
repacking, and replacing the parachute and deployment mechanism at
approved intervals.
Issued in Kansas City, Missouri on September 30, 1997.
Michael Gallagher,
Manager, Small Airplane Directorate Aircraft Certification Service.
[FR Doc. 97-27504 Filed 10-15-97; 8:45 am]
BILLING CODE 4910-13-P