EXEMPTION FROM SUBSECTION 521.158(7) OF THE CANADIAN AVIATION REGULATIONS ONLY WITH RESPECT TO PARAGRAPH 3.2(a)(1) OF SPECIAL CONDITION – AIRWORTHINESS 2010-02

Pursuant to subsection 5.9(2) of the Aeronautics Act, and after taking into account that the exemption is in the public interest and is not likely to affect aviation safety, I hereby exempt, subject to the conditions described herein, P.O. Box 2206, Savannah, GA 31402-2206, U.S.A. (Gulfstream) from the requirements set out in subsection 521.158(7) of the Canadian Aviation Regulations (CARs) only with respect to one of the requirements of Transport Canada Special Condition – Airworthiness (SCA) 2010-02 for the Gulfstream GIV-X aeroplane, issued on May 28, 2010, specifically paragraph 3.2(a)(1), and only with respect to exceeding the cabin altitude and duration limits expressed in 3.2(a)(1)(i) and (ii), following the uncontained engine failure case of 3.2(a)(2).  All of the remaining requirements of SCA 2010-02 including the other failure scenarios of 3.2(a)(2) must be complied with..

The text of the above-noted provision is provided in Appendix A of this exemption.  Special Conditions - Airworthiness (SCA) 2010-02 issued on 2010-05-28 is provided in Appendix B of this exemption.

PURPOSE

The purpose of this exemption is to allow the Gulfstream to request a change to the Canadian type design of the GIV-X aeroplane model without showing compliance with the cabin altitude and duration limits expressed in subparagraphs 3.2(a)(1)(i) and (ii), following the uncontained engine failure case of 3.2(a)(2), of SCA 2010-02.  All of the remaining requirements of SCA 2010-02 including the other failure scenarios of 3.2(a)(2) must be complied with.

APPLICATION

This exemption applies to Gulfstream Aerospace Corporation when applying for a change to the Canadian type design of the GIV-X aeroplane where the SCA 2010-02 has been incorporated.

CONDITIONS

The exemption is subject to the following conditions:

1. Gulfstream shall design the aeroplane so that occupants shall not be exposed to a cabin pressure altitude that exceeds the following after cabin decompression from an uncontained engine failure:


Cabin Pressure Altitude
( feet )

Maximum Total Exposure Time
( minutes )

Above 45,000

0

Above 40,000

1

Above 25,000

3

Above 10,000

6

2. In showing compliance, it may be assumed that an emergency descent is made in accordance with an approved emergency procedure.  Gulfstream shall apply a 17-second flight crew recognition and reaction time between cabin altitude warning and the initiation of an emergency descent.

3. Gulfstream shall incorporate an Automatic Emergency Descent Mode (EDM) that is designed to automatically descend the aeroplane in a controlled descent to a safe altitude from which the flight crew can regain control of the aeroplane.

4. For any aeroplane whose maximum operating altitude limitation exceeds 41,000 feet, Gulfstream shall develop and submit along with their application operating limitations requiring that:

a)   the Automatic EDM feature be armed and available any time the aeroplane is operated above 41,000 feet altitude; and

b)   if the Automatic EDM feature (including the autopilot and/or autothrottle systems) becomes inoperative while the aeroplane is above 41,000 feet altitude, the flight crew immediately descends to an altitude not exceeding 41,000 feet.

VALIDITY

This exemption is in effect until the earliest of the following:

a)   the date on which any one of the conditions set out in this exemption is breached; or

b)   the date on which this exemption is cancelled in writing by the Minister where he is of the opinion that the exemption is no longer in the public interest or that it is likely to affect aviation safety.

Dated at Ottawa, Ontario, Canada this _18_ day of November 2010, on behalf of the Minister of Transport.

 

 

[Original Version 11 signed by David Turnbull, AARD, 18 Nov 2010]

David Turnbull
Director, National Aircraft Certification
Civil Aviation

 

Attachment – Appendix A and Appendix B

APPENDIX A

 

REGULATORY REQUIREMENTS
CANADIAN AVIATION REGULATIONS

Part V - Airworthiness
Subpart 21 – Approval of the Type Design
or a Change to the Type Design of an Aeronautical Product
Section 521.158 – Standards of Airworthiness
(1) Subject to subsections (2) to (9), an applicant for the approval of a change to the type design of an aeronautical product shall demonstrate that the product meets the standards of airworthiness recorded in the type certificate data sheets and in force on the date of the application for the change.
.
.
.
(7) An applicant for the approval of a change to the type design of an aeronautical product having a novel or unusual design feature shall comply with any special conditions that are necessary to ensure that the change provides a level of safety equivalent to that provided by the applicable certification basis determined under subsections (1) to (6), (8) and (9).

APPENDIX B

SPECIAL CONDITION – AIRWORTHINESS 2010-02

Full text of SCA 2010-02 follows.


 

Special Conditions—Airworthiness (SCA)

File No.:

5010-A729

 

SCA No.:

2010-02

Airworthiness Manual File:

5009-6-525-3

 

Issue Date:

2010-05-28

RDIMS No.:

4719813 v6

 

 

 

These Special Conditions-Airworthiness are issued pursuant to paragraph 521.30(1)(c) and section 521.157 of the Canadian Aviation Regulations (CARs) with respect to the standards of airworthiness for which the Minister will issue a type certificate:

 

Gulfstream Aerospace
Model GIV-X Aeroplane
 

Operation Above 41,000ft Altitude up to and including 45,000ft
 
1.         General

These Special Conditions – Airworthiness (SCA) contain additional airworthiness requirements for the approval of a type certificate for the Gulfstream Aerospace Model GIV-X aeroplane.

The Gulfstream Model GIV-X aeroplane has novel or unusual design features associated with operation above 41,000 feet. The applicable airworthiness standards do not contain adequate or appropriate safety standards for operation above 41,000 feet.

These Special Conditions – Airworthiness contain the additional airworthiness standards specified by the Minister as being necessary to ensure that the type design will provide a level of safety equivalent to that established by the applicable standards of airworthiness.

 

2.         Background and Discussion

The Gulfstream Model GIV-X is a large-cabin business jet. There are two versions of GIV-X, the G450 and the G350. The G450 is the long-range (up to 4,450 nm) version and the G350 is a reduced fuel capacity version for mid-range capability (up to 3,990 nm).  Powered by two Rolls-Royce Tay Mk 611-8C turbine engines, equipped with FADEC (full authority digital engine control), the GIV-X has a maximum operating speed of Mach 0.88 and can accommodate up to 19 passengers.  The aeroplane maximum take-off weight is 33 521 kg (73,900 lbs) and the proposed maximum operating altitude is 45,000 ft.

The Gulfstream GIV-X is a derivative of the G-IV aeroplane, which itself is a derivative of the G-III, which in turn is derived from the G-II.  Hence, some elements of the GIV-X have a certification basis dating back to the G-II.

 

The basis of certification for the Gulfstream Model GIV-X aeroplane includes the applicable standards of Airworthiness Manual (AWM) Chapter 525 Change 525-8 (equivalent to FAR part 25 up to Amdt. 25-98), with exceptions, plus FAR part 25 amendments 25-99 through 25-101.  Included in the exceptions are AWM 525.365, 525.841, 525.571 and 525.1447, which revert to their predecessor FAR requirements of Amdts. 25-54, 25-38, 25-22 and 25-41 respectively for unmodified structure as compared to the GIV-series aeroplane.  AWM Change 525-8 (incorporating FAR §§ 25.365, 25.841 and 25.1447 at Amdt. 25-87, as well as 25.571 at Amdt. 25-96) is applicable for new or modified structure as compared to the GIV-series aeroplane.  Changes for the GIV-X as compared to the GIV-series are described on the Transport Canada type certificate data sheet, A-129.

The higher operational altitudes made feasible by the advent of turbojet transport aeroplanes introduced certain risks with respect to crew and passenger breathing that were not experienced with earlier propeller-driven aeroplanes. Accordingly, certification standards were developed in the early 1950s to permit safe operation of early turbojet transport aeroplanes up to certain maximum operating altitudes – typically up to 41,000 or 42,000 feet. Subsequent to the type certification of the early turbojet transport aeroplanes, approval to operate certain later aeroplanes at higher altitudes was requested.

The operation of aeroplanes at altitudes above 40,000 feet involves a number of novel or unusual features that were not addressed by any applicable airworthiness requirements up until FAR Amdt. 25-87 (1996).  Amendment 25-87 was promulgated expressly to deal with high altitude operations from 41,000ft up to 51,000ft. The applicable standards for the GIV-X have largely excluded Amdt. 25-87 as they relate to protection requirements for the aeroplane fuselage pressure vessel, or passengers and crew in the event of a rapid decompression, during high altitude operations.  In view of the potential adverse impact from rapid decompression at high altitudes, it is necessary to provide additional requirements for adequate protection.

Prior to Amdt. 25-87, various standards were developed and applied as special conditions by the Federal Aviation Administration (FAA) and other civil aviation authorities to certificate operation of certain executive transport aeroplanes to altitudes up to 51,000 feet.  For example, as part of Transport Canada’s type approval activity in 1986 for the G-IV, SCA 86-01 was deemed necessary to provide adequate protection during high altitude flights above 41,000ft up to 51,000ft.  The design criteria provided in that SCA were provided in addition to the applicable standards for the G-IV that included FAR part 25 up to Amdt. 25-56, with certain exceptions including § 25.571 at Amdt. 25-22.

Amendment 25-87 provided regulatory changes to codify and consolidate the different high-altitude criteria that had been made applicable by special conditions to previously certificated subsonic transport aeroplanes. Unlike the special conditions, Amdt. 25-87 established objective standards for high altitude operations, rather than addressing specific design features, as did the SCAs. In addition, that amendment acknowledged a human physiological pressure limit of 34,000 feet, the level above which persons not using supplementary oxygen are in serious peril and to which aeroplane occupants could be exposed during a cabin decompression.  Given that these high altitude operations requirements were provided and harmonized between Europe and North America in order to facilitate world sales of transport category aeroplanes, Transport Canada considers it appropriate to base this SCA upon the requirements provided in amendment 25-87 (adopted by Transport Canada into AWM Chapter 525 at Change 525-8).

The requirements for high altitude operation, as provided in Amdt. 25-87, were built upon requirements already promulgated under earlier amendments, including § 25.571 amendments 25-45 (1978), 25-54 (1980) and 25-72 (1990) to require damage-tolerance and fatigue evaluation of aeroplane primary structure.  Whereas the GIV-X does not include the later amendments to  § 25.571 in its applicable standards (for unmodified structure), damage tolerance methods are proposed by this SCA to be used to ensure pressure vessel integrity while operating at the higher altitudes.  AWM 525.571(a) at First Edition (incorporating FAR Amdt. 25-54) requires a showing that a catastrophic failure due to fatigue, corrosion, or accidental damage will not occur throughout the operational life of the aeroplane. The failure conditions described in AWM 525.571 are related to – and not limited to – depressurization. Compliance with AWM 525.571 requires the development of inspection intervals and procedures for the detection of crack lengths associated with the decompression of critical vent areas.

Further, with the incorporation of FAR Amdt. 25-87 (1996) into AWM Change 525-8, it was required that any event that would expose the occupants to cabin pressure altitudes in excess of the limits established in that amendment shall be shown to be extremely improbable. Specifically, in order to prevent permanent human physiological damage, the cabin altitude must not exceed 25,000 feet for more than two minutes. Further, the maximum peak cabin altitude must not exceed 40,000 feet, a requirement that is consistent with the standards established for previous certification programs.

Earlier special conditions for high altitude operations had included certain design criteria addressing pressurized cabins, to precisely define the manner in which various causes of a cabin decompression, and the resulting cabin pressure altitude profiles, were evaluated.  With FAR Amdt. 25-87, these design criteria were codified into § 25.841(a)(3), capturing the general intent from the special conditions into regulation, but transferring the specific cabin pressurization design criteria into FAA Advisory Circular (AC) 25-20. Therefore, compliance with this TCCA SCA must be demonstrated taking into consideration the applicable advisory material in FAA AC 25-20.

The cabin pressure altitude limits are prescribed based upon certain assumptions.  Continuous flow passenger oxygen equipment is certificated for use up to 40,000 feet. However, for rapid decompressions above 34,000 feet, reverse diffusion leads to low oxygen partial pressure in the lungs, to the extent that a small percentage of people may lose useful consciousness at 35,000 feet. The percentage increases to an estimated 60 percent at 40,000 feet, even with the use of the continuous flow system. In addition, at these altitudes the other aspects of decompression sickness have a significant detrimental effect on pilot performance (for example, a pilot can be incapacitated by internal expanding gases).

Decompression above 37,000 feet can result in cabin altitudes that approach the physiological limits of the average person; therefore, every effort must be made to provide the pilots with adequate oxygen equipment to withstand these severe decompressions. Reducing the time interval between pressurization failure and the time the pilot receives oxygen will provide a safety margin against being incapacitated and can be accomplished by the use of mask-mounted regulators. These special conditions therefore require pressure demand masks with mask-mounted regulators for the flightcrew. This combination of equipment will provide the best practical protection for the failures covered by the proposed special conditions and for improbable failures not covered by the special conditions, provided the cabin altitude is limited.

With reference to TCCA SCA 86-01, today’s SCA differs in the following areas:

  1. Airframe.  The requirements for Pressure Vessel Integrity-General and Damage‑Tolerance and Fatigue Evaluation of Structure requirements are revised to reflect elements of the standards promulgated under AWM 525.571 at First Edition (equivalent to FAR Sec 25.571 at Amdt. 25-54).  This is intended to: (1) provide for damage tolerance methods to be used to ensure pressure vessel integrity while operating at higher altitudes; (2) establish inspection intervals and procedures to detect cracks before an opening in the pressure vessel would allow rapid decompression; and (3) include these in the Airworthiness Limitations section of the Instructions for Continued Airworthiness.

  1. Systems and Equipment - Cabin Pressurization. These requirements are revised to reflect the objective standards promulgated under AWM 525.841(a) at Change 525-8 (equivalent to FAR § 25.841(a) at Amdt. 25-87).

With reference to the requirements of AWM 525.841(a) Pressurised Cabins, the fuselage structure, engine and system failures, which would otherwise be required to be considered at Change 525-8 and later amendments in evaluating the cabin decompression, is not an area of change for the GIV-X; consequently only FAR § 25.841(a) as amended through 25-38 is applicable (see Transport Canada TCDS A-129) for which no such consideration is required.  Therefore, the applicable standards are not appropriate to allow for the approval of a maximum operating altitude of 45,000 feet.

In demonstrating compliance with AWM 525.841(a) at Change 525-8 – and with this SCA – the crew is presumed to be using the oxygen equipment prior to a decompression that results in a cabin altitude greater than 34,000 feet, and would presumably perform an emergency descent in accordance with an approved emergency procedure. The time required for the crew to recognize a decompression emergency and don their oxygen masks has been established by tests to be 17 seconds. FAA Advisory Circular (AC) 25-20 - Pressurization, Ventilation and Oxygen Systems Assessment for Subsonic Flight including High Altitude Operation (9/10/96) provides a discussion of this recognition time. This 17-second delay is imposed between the cabin altitude warning and the beginning of action for descent. The critical failure case (probable system failure) shall be demonstrated by system failure tests at the maximum aeroplane altitude. For improbable failures, the cabin altitude could be established by analysis, and verified, if necessary, by tests at a much lower altitude, with the results extrapolated to the higher altitude.

  1. Systems and Equipment - Ventilation. These requirements are deleted in consideration that the GIV-X applicable standards are revised as compared to the GIV-series to include the requirement of AWM 525.831(a) at Change 525-8 (equivalent to FAR § 25.831(a) at Amdt. 25-89).

  1. Systems and Equipment – Air Conditioning. These requirements are deleted in consideration that the GIV-X applicable standards are revised as compared to the GIV-series to include the requirement of AWM 525.831(g) at Change 525-8 (equivalent to FAR § 25.831(g) at Amdt. 25-89).

  1. Systems and Equipment – Oxygen Equipment and Supply.  These requirements are revised to reflect the requirement of AWM 525.1447(c)(3) at Change 525-8 (equivalent to FAR § 25.1447(c)(3) at Amdt. 25-87).

 

In view of the discussion herein, and that provided in the preamble to FAR amendment 25-87 [61 FR 28684, Jun.5, 1996] and associated Notice of Proposed Rulemaking (NPRM) No. 89-31 [54 FR 48538, Nov.22, 1989], in order to ensure a level of safety equivalent to that established by Transport Canada’s applicable standards of airworthiness, this SCA is deemed necessary to provide adequate protection during high altitude flights.

The additional requirements of this SCA include consideration for pressurized compartment loads, cabin pressurization, and oxygen equipment and supply.

3. Airworthiness Standards

For type certification of the Gulfstream Model GIV-X aeroplane, the following airworthiness requirements for approval of high altitude subsonic flight are provided in addition to the applicable standards of AWM Chapter 525 and FAR part 25.

3.1       Airframe

  1. Pressure Vessel Integrity

    1. The maximum extent of failure and pressure vessel opening that can be demonstrated to comply with subsection 3.2(a) Cabin Pressurization of this special condition must be determined. It must be demonstrated by crack propagation and damage tolerance analysis supported by testing that a larger opening or a more severe failure than demonstrated will not occur in normal operations.

    2. Inspection schedules and procedures must be established to assure that cracks and normal fuselage leak rates will not deteriorate to the extent that an unsafe condition could exist during normal operation, and must be included in the Airworthiness Limitations section of the Instructions for Continued Airworthiness required by AWM 525.1529.

3.2 Systems and Equipment

(a) Cabin Pressurization

In addition to the requirements of FAR § 25.841(a), the following applies:

  1. The aeroplane must be designed so that occupants will not be exposed to a cabin pressure altitude that exceeds the following after decompression from any failure condition not shown to be extremely improbable:

    1. Twenty-five thousand (25,000) feet for more than 2 minutes; or

    2. Forty thousand (40,000) feet for any duration.
  2. Fuselage structure, engine and system failures are to be considered in evaluating the cabin decompression.

  3. In showing compliance with paragraphs 3.2(a)(1) and (2) of this special condition, it may be assumed that an emergency descent is made in accordance with an approved emergency procedure.  A 17-second crew recognition and reaction time must be applied between cabin altitude warning and the initiation of an emergency descent.

(b) Oxygen Equipment and Supply

In addition to FAR § 25.1447(c), the following applies:

  1. The oxygen dispensing equipment for the flight crewmembers shall be:

    1. The diluter demand or pressure demand (pressure demand mask with a diluter demand pressure breathing regulator) type, or other approved oxygen equipment shown to provide the same degree of protection, for the aeroplane to be operated above 25,000 feet.

    2. The pressure demand (pressure demand mask with a diluter demand pressure breathing regulator) type with mask-mounted regulator, or other approved oxygen equipment shown to provide the same degree of protection, for the aeroplane to be operated at altitudes where decompressions that are not extremely improbable may expose the flight crew to cabin pressure altitudes in excess of 34,000 feet.

  2. A Continuous flow oxygen system must be provided for the passengers.

 

[Original SCA 2010-02 signed by Blake Cheney, A/AARTC, May 28 2010 (see scanned document, embedded above)]

<Original signed by>

Blake T. Cheney
A/Chief, Aircraft Certification Standards

 

 

 

Date de modification :