1 of 3

Gulfstream Aerospace LP ¤ c/o IAI Dept. 4199 ¤ Ben Gurion Int'l Airport 70100 ¤ ISRAEL

Tel: +972-3-935-6624 ¤ Fax: +972-3-935-6750 July 30, 2015 GALP Ref: FAA/15220/CG

Mr. Thomas Rodriguez Program Manager, International Branch, ANM-116
Federal Aviation Administration Transport Airplane Directorate
Aircraft Certification

Subject: Request for Extension on FAA Exemption No. 10408 for Gulfstream G280

Attachments:

(A) Petition for partial Exemption Gulfstream Aerospace LP Uncontrollable High Thrust
Failure Conditions Gulfstream Model G250 (B) Exemption No. 10408 - Regulatory Docket No.FAA-2011-0686

Dear Mr. Rodriguez,

I am writing on behalf of Gulfstream Aerospace Limited Partnership (GALP), the holder of FAA type certificate A61NM for the Gulfstream G280 aircraft model, to request an extension of the current 19 December, 2015 deadline for obtaining FAA approval of an amended type design incorporating thrust-malfunction accommodation logic and for incorporating the design change on new production aircraft. GALP hereby respectfully requests an extension of twelve (12) months from the current deadline based upon the justifications provided
herein.

On December 19, 2011 the Federal Aviation Administration (FAA) granted exemption 10408 (petition and grant attached) associated with 25.901(c) of Title 14 of the Code of Federal Regulations and the Uncontrollable High Thrust (UHT) scenario. More than eight months later, on 30 August 2012, the FAA issued type certificate A61NM for the Gulfstream G280. The technical basis and merits for granting this exemption for the G280 are well documented in attachments (A) and (B) and remain equally compelling at this time.

We have been working intensively and very closely with the G280 engine manufacturer, Honeywell, in developing the amended type design intended to address the UHT issue. The software which provides the required UHT protection resides in the engines Full Authority Digital Engine Control (FADEC). The FADEC software version 2.0 has been in development now for several years to support the requirements of this exemption as well as to incorporate various improvements. Following the review of recent flight test data and performance calculations we have identified additional issues requiring correction by Honeywell.2 of 3

Gulfstream Aerospace LP ¤ c/o IAI Dept. 4199 ¤ Ben Gurion Int'l Airport 70100 ¤ ISRAEL

Tel: +972-3-935-6624 ¤ Fax: +972-3-935-6750 Honeywell estimates that incorporation and certification of the necessary corrections will require an additional four months, beyond the eight months discussed above. The result being a total requested extension of twelve (12) months to December 2016.

A review of several FAA exemptions related to the UHT issue and compliance with 25.901(c) with a focus on the issue dates of the exemption and of the type certificate clearly show that in the case of the G280 the more than eight (8) month span between the exemption and type certificate issue dates is extreme. Issuing th e exemption so far in advance of the issuance of the type certificate, and attaching the four year compliance requirement to the exemption issuance date rather than the type certificate issuance date in effect started the “timer” for providing a new design (amended type design) while we were still developing / certifying the initial type design. To illustrate this we provide below a summary of a number business aviation aircraft models receiving type certification in the same period. This is by no means an all inclusive list but illustrates the issue quite clearly.

TC Holder Aircraft Model TC No. TC Issue

Date Exemption

Issue Date FAA Exemption

No.

Gulfstream Aerospace

LP G280 A61NM 8/30/2012 12/19/2011 10408

Bombardier Challenger 350 (BD

‐ 100

‐ 1A10) T00005NY 6/24/2014 6/24/2014 11013

Gulfstream Aerospace
Corporation (GAC) Gulfstream GVI (G650) T00015AT 9/7/2012 8/28/2012 10614

Cessna Model 680
Sovereign+ T00012WI 12/20/2013 11/29/2013 10902

The additional four months requested, beyond the eight months justified due to the significant difference between exemption and type certificate issue dates, poses no adverse effect on safety of the aircraft, its operators or to the public in general. The case for granting this exemption made in the original GALP petition (Attachment (A)) would not be impacted by this extension. In order to place this in t he correct perspective it is important to point out that at the G280 production rate established for the period covering the additional four months requested only an additional 6-7 aircraft would be entering into service under the exemption if the full twelve month extension is granted by the FAA.

In addition to the inherent limited exposure and extremely low occurrence rate of such events throughout the industry, the FAA required that the G280 Aircraft Maintenance Manual (AMM) contain mandatory reporting requirements for engine controls related Line Replaceable Units (LRU) and their specific failure modes which could lead to a UHT event. While the reporting requirement is from the operator to the FAA, we have no records of any such reports having been made.3 of 3

Gulfstream Aerospace LP ¤ c/o IAI Dept. 4199 ¤ Ben Gurion Int'l Airport 70100 ¤ ISRAEL

Tel: +972-3-935-6624 ¤ Fax: +972-3-935-6750 GALP respectfully requests that the FAA not delay taking a decision on this request by foregoing the publication and public comment procedures. GALP feels this request is supported by the position that granting of this extension has no impact upon public safety nor does it represent a matter of compelling interest to the public. Additionally, a delay in acting on this request for extension caused by publication could have an adverse effect on GALP and the operators of the G280 airplanes who have made substantial commitments
associated with aircraft deliveries.

We greatly appreciate the FAA’s consideration to this request and look forward to its timely processing.

Regards,

Charly Gaber Airworthiness & Certification Manager Gulfstream Aerospace LP
P.O. Box 1036 Airport City 7019900, Israel e-mail: Charly.Gaber@gulfstream.com Telephone: +972-3-935-6627
Fax: +972-3-935-6750

cc: D. Lawton, J. Gibbs, D. Such, S. Cottrell, I. Kalal, M. Kollet, T. Nir M. Fagan, File1 of 7

Gulfstream Aerospace LP ¤ PO Box 1036 ¤ Airport City 70100 ¤ ISRAEL

Tel: +972-3-935-6624 ¤ Fax: +972-3-935-6750 Petition for partial Exemption Gulfstream Aerospace LP Uncontrollable High Thrust Failure Conditions

Gulfstream Model G250 Relief from section 14 CFR Part 25.901(c)

Section 25.901(c) requires in part th at “no single failure or malfunction or probable combination of failures will jeopardize the safe operation of the airplane”.

Gulfstream Aerospace LP respectfully requests a time limited partial exemption to Federal Aviation Regulation (FAR) Part 25.901(c) of Title 14, CFR, for certain extremely remote powerplant failures that could affect only a very limited portion of the flight envelope of the
Gulfstream Model G250.

This partial exemption requires Gulfstream Aerospace LP to demonstrate that the overall level of safety of the thrust control system of G250 model will not be less than that of the current transport category aircraft fleet. For this purpose, Gulfstream Aerospace LP analyzed the Uncontrollable High Engine Thrust failure rate data of the Honeywell AS907 engine family and performed engineering-simulated flights per scenarios specified in CAAI / FAA Issue Paper P-10.

The exemption is required for a period of 4 years after FAA validation. During this period, GALP and Honeywell will develop and make available improved UHT logic which will mitigate the effects of an UHT event in some scenarios. The improvement will be certified as a product improvement prior to the expiration of the time frame specified above and will be implemented in all new production a/c manufactured after this date. It is not the intention of GALP to retrofit previously fi elded aircraft (estimated 100 a/c) with the improved UHT logic.

The nature of this petition for partial exemption is similar to previously granted exemptionsfor the Airbus models A340-500, A340-600, the Embraer models EMB-135BJ, EMB145XR, the Boeing model 757-300 and 777’s and the Gulfstream Models G150, G-1159, G-IV, GV and GV-SP.

Supportive Information:

A committee consisting of representatives from the FAA, the JAA, airplane manufacturers, and engine manufacturers was formed in 1998 to study strategies for providing additional protection from thrust control malfunctions resulting in un-commanded high thrust. The committee found that for the existing in-s ervice airplanes, whose propulsion systems have demonstrated a level of reliability on the order of one un-commanded high thrust event per 10 million flight hours, it would not be in the public interest to mandate major and noveldesign changes in an attempt to eliminate the already small potential exposure to uncommanded high thrust malfunctions resultin g from single failures. The committee’s recommended approach to ensure continued high levels of reliability for all presently certified models is to monitor in-service performance and, if any unacceptable failure modes are identified, to take prompt corrective action by introducing focused design improvements using proven technology.2 of 7

Gulfstream Aerospace LP ¤ PO Box 1036 ¤ Airport City 70100 ¤ ISRAEL

Tel: +972-3-935-6624 ¤ Fax: +972-3-935-6750 Full compliance with 14 CFR 25.901(c) would require introduction of complicated and novel design changes to the G250 Program, such as the Thrust Control Malfunction feature. It is recognized that experience with this feature over the past few years has demonstrated that such a feature can safely and reliably eliminate most of the causes of noncompliant UHT failures conditions.

At this time GALP is considering the right solution to incorporate this feature in the G250
aircraft.

The petitioner intends to demonstrate that those combinations of failures that could jeopardize safe operation meet the intent of § 25.901(c) in that they are not “probable

combinations 1 .” Conversely, the petitioner does not always intend to demonstrate that those single failures which could jeopardize safe operation comply with § 25.901(c). Compliance with § 25.901(c) requires each identified single failure be assumed to occur under all anticipated combinations of airplane operating and environmental conditions. While the single failures themselves must be assumed to occur regardless of their probability 2 , probability can be considered when determining what combinations of operating and environmental conditions are anticipated to occur in the fleet life of the airplane type. Single failures do not need to be assumed to occur under conditions that are in and of themselves not expected to occur.

The engine control system for the G250 is a FADEC-based system and as such, future design changes to this control system should pr ovide opportunities to significantly reduce or even eliminate the subject non-compliance. The conditions established by the FAA for granting this partial exemption, when applied to each proposed design change, are intended to take full advantage of each practicable opportunity for improvement while affording the petitioner all warranted flexibility to certificate non-compliant derivative designs

.

Issue of Public Interest

A control system that might eliminate all fa ilure modes of concern for the Gulfstream Aerospace LP G250 Model (such as the Thrust Control Malfunction Unit), would require

1 The term “probable,” as used in § 25.901(c) has a very differen t meaning than the same term as subsequently used in associatio n with § 25.1309(b) compliance. As used in §25.901(c), "probable" mean s “foreseeable”. In §25.1309(b) terms, this means the subject failure conditions are "anticipated to occur” (i.e. aren't "extremely improbable”).

2 While probability has been an acceptable m eans of supporting a finding th at a particular "combination" of failures are not "pr obable", any single failure where the physics of the failure can be identif ied is typically "anticipated to occur" unless that occurrenc e within the relevant exposure can be clearly and acceptably ruled out, as is the case for those structural failures specifically excepted b y the rule itself.3 of 7

Gulfstream Aerospace LP ¤ PO Box 1036 ¤ Airport City 70100 ¤ ISRAEL

Tel: +972-3-935-6624 ¤ Fax: +972-3-935-6750 significant modifications to the current engi ne control system. A re design of previously approved engine control system architecture wo uld impact the schedule of the Gulfstream Aerospace LP G250 Model program

.

Since this feature is still in development, requiring the G250 Model to fully comply with this rule would prevent Gulfstream Aerospace LP from certifying the aircraft on a timely and competitive schedule, putting it in an unfair disadvantage to its competitors in Europe and with other foreign aircraft manufacturers. This could result in economic disadvantage to the company, its employees and communities who are dependent upon this commerce. Additionally, Gulfstream Aerospace LP is a highly reputable supplier of transport aircraft that serve vital commercial and governmental entities throughout the world. These operators depend on the improved technology in new Gulfstream Aerospace LP models to effectively and safely meet the needs of national and international commerce, governance and charitable missions throughout the world.

Effect of the Exemption on Safety

As stated above, Gulfstr eam Aerospace LP will demons trate that the risks due to uncontrollable high thrust failure conditions on G250 will not exceed those currently known and accepted for comparable existing transport category airplanes. This means that granting partial exemption should not adversely affect and, in fact, should improve the average per flight hour risk within the current transport airplane fleet.

For those existing transport airplanes re-evaluated to date, the conditions under which an uncontrollable high thrust failure may jeopardize the safe operation of the airplane are limited to specific aborted takeoff scenarios. Given that these scenarios occur, there is still a low probability that any serious injury will develop. This limited exposure, in conjunction with the low probability of occurrence, means that an Uncontrolled High Thrust event is a relatively low per flight hour risk. This assessment is supported by the fact that the 1997 Saudi Arabian Airlines Boeing 737-200 accident is the only one attributed to these types of failures and there were no serious injuries in that accident.

It is the spectra of this low per-flight-hour risk accumulating indefinitely on many, if not most, existing and future transport airplanes that are the primary concern driving development of the FAA’s “Thrust Control Malfunction Airworthiness Program.” To date, corrective actions under 14 CFR part 39 have only been deemed warranted when the uncorrected risks for a particular type design were considered significantly greater than those required by the conditions and limitations of this petition for partial exemption.

Gulfstream Aerosapce LP agrees to demonstrate that all practicable actions have been taken to minimize the adverse effect on safety associated with granting of the exemption from 14CFR 25.901(c) for the G250 Model aircraft. Furthermore, Gulfstream Aerospace LP would like to emphasize the following:4 of 7

Gulfstream Aerospace LP ¤ PO Box 1036 ¤ Airport City 70100 ¤ ISRAEL

Tel: +972-3-935-6624 ¤ Fax: +972-3-935-6750  The G250 aft fuselage mounted engine design (i.e. relative close proximity to A/C centerline) mitigates much of the adverse yaw condition that may be generated during a single engine uncontrollable high thrust event on other designs.

 The G250 incorporates a Thrust Compensator feature that compensates the thrust asymmetry by rudder movement. This feature is automatically actuated when thrust asymmetry occurs and it augments the aircraft controllability when UHT is encountered (as demonstrated in the engineering simulation).

 The controllability assessment during Uncontrolled High Thrust was evaluated by conservative Engineering simulations and will be verified in a full Level D airplane
simulator as soon as it is available.

 It was found that the G250 Model complies with 14CFR 25.901(c) for any foreseeable uncontrollable high thrust failure conditions, except for very limited window(refer to Flight Simulator test report, doc number: 30P011/071452) :

 RTO scenarios where the malfunction occurs below 50kts, as was demonstrated in simulation flights. This scenario is included in the request for exemption since the Nose Wheel Steering, which is essential for controlling the A/C on ground at low speeds was not available on the simulator.

 The frequency of occurrence of uncontrollable high thrust failure condition on the G250 was calculated to be ~2 E-8 which is less than the known average industry value of one per ten million airpla ne operating hours.

 Thrust Control Malfunction unit is in development and will be incorporated in the G250.

Gulfstream Aerospace LP has verified that the G250 Model exposures and failure rates are such that this airplane should not exceed the known average per flight-hour risks of comparable existing transport airplanes. Making this statement a condition of this exemption, in combination with the condition to minimize that risk, means that granting this exemption should not adversely affect and in fact, should improve the average per flight hour risk within the current transport airplane fleet.

In support of this exemption and prior to customer delivery of any G250 aircraft, Gulfstream Aerospace LP will develop and obtain CAAI / FAA acceptance of the instructions for continued airworthiness. Further, the Uncontrollable High Engine Thrust failures shall be considered mandatory reportable to the CAAI/FAA under 14 CFR Part 21.3, for any airplane certificated under this exemption.

The limited exposure, in conjunction with the historically low occurrence rates throughout the industry, makes this a relatively low per fl ight hour risk. This assessment is further supported by the fact that the 1997 Saudi Arabian Airlines Boeing 737-200 accident is the only event attributed to these types of failures and there were no serious injuries in that

accident

.5 of 7

Gulfstream Aerospace LP ¤ PO Box 1036 ¤ Airport City 70100 ¤ ISRAEL

Tel: +972-3-935-6624 ¤ Fax: +972-3-935-6750 Waiver of Notice and Public Procedure

Gulfstream Aerospace LP respectfully requests that, and believes that good cause exists why, action on this petition should not be delayed by publication and comment procedures. Gulfstream Aerospace LP feels this request is supported by the following reasons:

1. The petitioner’s request does not set a precedent because the relief requested herein is identical to exemptions granted previously.

2. A delay in acting on the petition caused by publication could have an adverse effect on Gulfstream Aerospace LP and the operators of the G250 airplanes who have made substantial commitments and plans for the introduction of the airplanes into the fleet to
meet mission needs.

Conclusion

Gulfstream Aerospace LP believes that the above arguments favor a time limited exemption from 14 CFR 25.901(c) for the aft fuselage mounted installation of the Honeywell FADEC controlled engines onto the GULFSTREAM AEROSPACE LP G250 aircraft. Additionally, Gulfstream Aerospac e LP believes that any risks due to an Uncontrollable High Thrust failure condition on G250 will not exceed those currently known and accepted for comparable existing transport category airplanes and that an exemption is in the public interest. Gulfstream Aerospace LP requests that the privileges of this exemption would apply outside th e United States due to the tr ansoceanic capability of the G250 aircraft and the character of mission for many of our operators.6 of 7

Gulfstream Aerospace LP ¤ PO Box 1036 ¤ Airport City 70100 ¤ ISRAEL

Tel: +972-3-935-6624 ¤ Fax: +972-3-935-6750 APPENDIX A

ENGINE CONTROL SYSTEM OVERVIEW

.

The G250 is equipped with two Honeywell AS907-2 turbofan engines of 4.2 to 1 bypass ratio, enclosed by nace lles and mounted to pylons extending laterally outward from the aft fuselage section.

A throttle control assembly (TQA) is installed in the flight compartment with all controls on the pedest al accessible to both pilot and copilot. The engine thrust is controlled by the pilot with the throttle lever by means of Full Authority Digital Electronic Control (FADEC) which is electrically monito ring the thrust lever position (thrust by wire). Each of the engine power controls consist of a throttle lever, thrust reverser lever, AT (Autothrottle) Engage/Disengage switch, AT Quick Disconnect switch, and Takeoff/Go- Around switch. A single APR switch is located forward of the TQA. If the APR switch is selected, an engine will engage APR mode if the respective throttle lever is moved into the takeoff range. A RUN/STOP switch is provided to shutdown each engine.

G250 Engine control system –

Uncontrolle d engine overspeed safety features.

1. N2 Overspeed Shutdown

The N2 overspeed system protects against overspeed of both rotor systems (N1 and N2) driven by control system failures. These failures may include software errors and electrical malfunctions
of the FADEC or HMU mechanical malfunctions that result in uncommanded acceleration or over fueling of the engine. The N2 overspeed protec tion system is implemented through dedicated circuits within the engine FADEC controller. These circuits operate independently of the CPU and software that control engine operation. Each ECU contains two N2 overspeed detection circuits. One circuit monitors the PMA N2 signal, while the other monitors the gearbox mounted N2 monopole signal. When both circuits detect an overspeed condition (defined as N2>103 percent ±0.5 percent), the shutoff solenoid is energized. In addition, the run coil (used by software to enabl e fuel flow on start) is disabled by overspeed detection circuit and not the software. The shutdown coil is maintained energized and the run coil disabled until 35 percent speed, when the overspeed circuits unlatch. During the flameout/deceleration from overspeed to 35 per cent, software attempts to de-power the run solenoid and igniters, also closing the main MV to positively latch the shutdown. Either engine FADEC controller can detect an overspeed condition and thus shut down the engine, even if that channel is not the controlling channel. The N2 overspeed system is checked on each start and
each shutdown.

2. Broken Low Pressure Shaft (N1) Overspeed Shutdown

The N1 broken shaft system provides protection against LPT overspeed driven by LPT shaft breakage. In order to obtain the rapid response needed for this function, the system is implemented through dedicated circuits within the ECU, and independent of the CPU. Note that N1 overspeed protection is implemented via the N2 overspeed protection system. A power turbine position detector, mounted behind the final LPT stage, senses LPT position and signals the N1 OSSO circuit, if LPT position shifts rearward enough to indicate a severed LPT shaft. The N1 OSSO circuit then initiates an engine shutdown using the same OSSOV as the N2 OSSO system. T he power turbine position detector is a device that breaks an electrical link, or circuit, to indica te rearward motion of the LPT. Redundant wiring to the link ensures that open circuit failures of connectors or harnesses do not result in false broken shaft detection. Each engine FADEC contains two identical but independent N1 OSSO detection
circuits that monitor the link. A broken shaft is detected when both N1 OSSO detection circuits simultaneously detect a broken link with continuity on all other detector lines continuously for 1.0 to 1.5 milliseconds. When a broken shaft is detected, the circuit energizes the overspeed shutoff coil.7 of 7

Gulfstream Aerospace LP ¤ PO Box 1036 ¤ Airport City 70100 ¤ ISRAEL

Tel: +972-3-935-6624 ¤ Fax: +972-3-935-6750 The circuitry simultaneously shorts out the run coil to remove this opposing force. FADEC ensures that the coil voltage collapses quickly to remove any opposing force. Within a few hundred milliseconds of the detected event, software also initiates a normal shutdown, disabling ignition, deenergizing the run coil, and closing the MV latching in the shutdown. The event is stored in NVM, and software will not allow another engine start until proper
maintenance action is taken. The N1 broken shaft protection system is checked on each startup and shutdown.

### Exemption No. 10408

UNITED STATES OF AMERICA

DEPARTMENT OF TRANSPORTATION

FEDERAL AVIATION ADMINISTRATION RENTON, WASHINGTON 98057-3356

In the matter of the petition of

Gulfstream Aerospace LP

for an exemption from § 25.901(c) of Title 14, Code of Federal Regulations Regulatory Docket No.FAA-2011-0686

GRANT OF EXEMPTION

On June 21, 2011, Mr. Baruch Marom, Gulfstream Aerospace LP (GALP), P.O. Box 1036, Airport City 70100, Israel, petitioned for an exemption from the “no single failure” criteria of § 25.901(c) of Title 14, Code of Federal Regulations (14 CFR) as it relates to certain extremely remote, uncontrollable, high-thrust failure conditions. Recent studies and service experience indicate that some existing transport-category ai rplanes do not strictly comply with § 25.901(c) for certain uncontrollable high-thrust failure conditions. The proposed exemption, if granted, would permit type certification of similarly non-compliant GALP Model G280 airplanes with Honeywell AS907 engines.

The petitioner requires relief from the following regulations:

Section 25.901(c) as amended by Am endments 25-1 through 25-84:

(c) For each powerplant and auxiliary power unit installation, it must be established that no single failure or malfunction or probable combination of failures will jeopardize the safe operation of the airplane except that the failure of structural elements need not be considered if the probability of such failure is extremely remote.

The petitioner supports its request with the following information:

This section quotes the relevant information from the petitioner’s request. The complete petition is available at the Department of Transportation’s Federal Docket Management System, on the Internet at http://regulations.gov, in docket no. FAA-2011-0686.

### 2 Gulfstream Aerospace LP respectfully requests a time limited partial exemption to Federal Aviation Regulation (FAR) Part 25.901(c) of Title 14, CFR, for certain extremely remote powerplant failures that could affect only a very limited portion of the flight envelope of the Gulfstream Model G280.

This partial exemption requires Gulfstream Aerospace LP to demonstrate that the overall level of safety of the thrust control system of G280 model will not be less than that of the current transport category aircraft fleet. For this purpose, Gulfstream Aerospace LP analyzed the Uncontrollable High Engine Thrust failure rate data of the Honeywell AS907 engine family and performed engineering-simulated flights per scenarios specified in CAAI / FAA Issue Paper P-10.

The exemption is required for a period of 4 years after FAA validation. During this period, GALP and Honeywell will develop and make available improved UHT logic which will mitigate the effects of an UHT event in some scenarios. The improvement will be certified as a product improvement prior to the expiration of the time frame specified above and will be implemented in all new production a/c manufactured after this date. It is not the intention of GALP to retrofit prev iously fielded aircraft (estimated 100 a/c) with the improved UHT logic.

The nature of this petition for partial exemption is similar to previously grantedexemptions for the Airbus models A340-500, A340-600, the Embraer models EMB135BJ, EMB145XR, the Boeing model 757-300 and 777’s and the Gulfstream Models G150, G-1159, G-IV, GV and GV-SP.

Supportive Information:

A committee consisting of representatives from the FAA, the JAA, airplane manufacturers, and engine manufacturers was formed in 1998 to study strategies forproviding additional protection from thrust control malfunctions resulting in uncommanded high thrust. The committee found that for the existing in-service airplanes,whose propulsion systems have demonstrated a level of reliability on the order of one uncommanded high thrust event per 10 million flight hours, it would not be in the public interest to mandate major and novel design changes in an attempt to eliminate the already small potential exposure to uncommanded high thrust malfunctions resulting from single failures. The committee’s recommended approach to ensure continued high levels of reliability for all presently certified models is to monitor in-service performance and, if any unacceptable failure modes are identified, to take prompt corrective action by introducing focused design improvements using proven technology.

Full compliance with 14 CFR 25.901(c) would require introduction of complicated and novel design changes to the G280 Program, such as the Thrust Control Malfunction feature. It is recognized that experience with this feature over the past few years has demonstrated that such a feature can safely and reliably eliminate most of the causes of noncompliant UHT failures conditions.

### 3 At this time GALP is considering the right solution to incorporate this feature in the

G280 aircraft.

The petitioner intends to demonstrate that those combinations of failures that could jeopardize safe operation meet the intent of § 25.901(c) in that they are not “probable combinations.” Conversely, the petitioner does not always intend to demonstrate that those single failures which could jeopardize safe operation comply with § 25.901(c).

The engine control system for the G280 is a FADEC-based system and as such, future design changes to this control system should provide opportunities to significantly reduce or even eliminate the subject non-compliance. The conditions established by the FAA for granting this partial exemption, when applied to each proposed design change, are intended to take full advantage of each practicable opportunity for improvement while affording the petitioner all warranted flexibility to certificate non-compliant derivative designs.

Issue of Public Interest

A control system that might eliminate all failure modes of concern for the Gulfstream Aerospace LP G280 Model (such as the Thrust Control Malfunction Unit), would require significant modifications to the current engine control system. A redesign of previously approved engine control system architecture would impact the schedule of the Gulfstream Aerospace LP G280 Model program.

Since this feature is still in development, requiring the G280 Model to fully comply with this rule would prevent Gulfstream Aerospace LP from certifying the aircraft on a timely and competitive schedule, putting it in an unfair disadvantage to its competitors in Europe and with other foreign aircraft manufacturers. This could result in economic disadvantage to the company, its employees and communities who are dependent upon this commerce. Additionally, Gulfstream Aerospace LP is a highly reputable supplier of transport aircraft that serve vital commercial and governmental entities throughout the world. These operators depend on the improved technology in new Gulfstream Aerospace LP models to effectively and safely meet the needs of national and international commerce, governance and charitable missions throughout the world.

Effect of the Exemption on Safety

As stated above, Gulfstream Aerospace LP will demonstrate that the risks due to uncontrollable high thrust failure conditions on G280 will not exceed those currently known and accepted for comparable existing transport category airplanes. This means that granting partial exemption should not a dversely affect and, in fact, should improve the average per flight hour risk within the current transport airplane fleet.

Gulfstream Aerospace LP agrees to demonstrate that all practicable actions have been taken to minimize the adverse effect on safety associated with granting of the exemption

### 4 from 14CFR 25.901(c) for the G280 Model aircraft. Furthermore, Gulfstream Aerospace LP would like to emphasize the following:

 The G280 aft fuselage mounted engine design (i.e. relative close proximity to A/C centerline) mitigates much of the adverse yaw condition that may be generated during a single engine uncontrollable high thrust event on other designs.

 The G280 incorporates a Thrust Compensator feature that compensates the thrust asymmetry by rudder movement. This feature is automatically actuated when thrust asymmetry occurs and it augments the aircraft controllability when UHT is encountered (as demonstrated in the engineering simulation).

 The controllability assessment during Uncontrolled High Thrust was evaluated by conservative Engineering simulations and will be verified in a full Level D airplane simulator as soon as it is available.

 It was found that the G280 Model complies with 14CFR 25.901(c) for any foreseeable uncontrollable high thrust failure conditions, except for very limited window(refer to Flight Simulator test report, doc number: 30P011/071452):

 RTO scenarios where the malfunction occurs below 50kts, as was demonstrated in simulation flights. This scenario is included in the request for exemption since the Nose Wheel Steering, which is essential for controlling the A/C on ground at low speeds was not available on the

simulator.

 The frequency of occurrence of uncontrollable high thrust failure condition on the G280 was calculated to be ~2 E-8 which is less than the known average industry value of one per 10 million airplane operating hours.

 Thrust Control Malfunction unit is in development and will be incorporated in the

G280.

Gulfstream Aerospace LP has verified that the G280 Model exposures and failure rates are such that this airplane should not exceed the known average per flight-hour risks of comparable existing transport airplanes. Making this statement a condition of this exemption, in combination with the condition to minimize that risk, means that granting this exemption should not adversely affect and in fact, should improve the average per flight hour risk within the current transport airplane fleet.

In support of this exemption and prior to customer delivery of any G280 aircraft, Gulfstream Aerospace LP will develop and obtain CAAI / FAA acceptance of the

instructions for continued airworthiness. Fu rther, the Uncontrollable High Engine Thrust failures shall be considered mandatory reportable to the CAAI/FAA under 14 CFR Part 21.3, for any airplane certificated under this exemption.

### 5 Federal Register publication

A summary of this petition was published in the Federal Register on July 29, 2011. The FAA

received no comments.

FAA Analysis: Introduction

Granting this exemption requires the petitioner to show, as required by § 11.81(d), that the request is in the public interest, and, as required by § 11.81(e), that the exemption will not adversely affect safety, or that a level of safety will be provided that is equal to that provided by the rules from which the exemption is sought.

FAA Analysis: Public Interest

In their petition, Gulfstream Aerospace LP (GALP) acknowledges that the Model G280 type design currently proposed for certification will not fully comply with the “no single failure” provision of § 25.901(c) as it relates to certain uncontrollable high-thrust failure conditions. Following the investigation of a 1997 Saudi Ar abian Airlines Boeing 737-200 accident, it was recognized that this type of non-compliance had long been endemic in the state-of-the-art engine-control architectures of most transport- category airplanes. Furthermore, it was going to be very challenging to develop and validate safe practical compliant alternatives to that architecture. Since that time, most type-certif ication programs have included some sort of exemption for uncontrollable high-thrust failure conditions. However, one of the conditions for granting each of those exemptions has been that the applicant take all practicable actions to minimize the adverse effects on safety associated with granting the exemption.

In the process of evaluating the proposed GAL P Model G280 type design, the FAA recognized

that GALP had not taken all feasible actions to eliminate or further reduce the risks associated with this non-compliance. Specifically, thrust-m alfunction-accommodation logic (i.e. logic that identifies and safely accommodates any sustained, substantial discrepancy between the actual and commanded thrust, as sensed and validated by the engine control) was not incorporated. Such thrust-malfunction-accommodation logic incorporated into some recently approved airplane type designs has proven itself to be practical and effective at eliminating most noncompliant, uncontrollable, high-thrust failures except for those associated with the airplane throttle system (e.g. stuck throttle, disagreement between actual throttle position and that input to the engine control, etc.).

However, GALP did not become aware that thrust-malfunction-accommodation logic was considered a practical and effective mitigating action until it was too late to safely develop and validate such critical engine-control logic without substantially impacting their delivery schedule, which made incorporation of such engine-control logic, before certification, impractical. Consequently, GALP has requested this exemption to allow them up to 4 years from the date of granting to develop, certificate, put into production, and facilitate retrofit of acceptable thrust-malfunction-accommodation logic, eliminating all noncompliant,

### 6 uncontrollable, high-thrust failures, except perhaps those due to failures within the airplane throttle system.

If the FAA were to deny this petition, that would substantially delay delivery of these aircraft and put considerable schedule pressure on the de velopment and certification of critical enginecontrol-logic changes. This would not only have the adverse economic and logistical impacts noted by the petitioner, but also inherently increase the risk of undiscovered development errors in the new thrust-malfunction-accomodation logic. The malfunctioning of this logic could have a more adverse impact on safety than would its absence; the FAA considers it critical to safety to allow ample time for proper development and validation of such logic systems.

In consideration of the above, and with the finding below that granting this petition will not adversely affect safety, the FAA concludes that granting this time-limited exemption is in the public interest.

FAA Analysis: Effect on Safety

The petitioner will be required, by the conditions for granting this exemption, to demonstrate that the risks due to uncontrollable high-thrust failure conditions on any airplane certificated under this exemption will not exceed those currently known and accepted for comparable existing transport-category airplanes. Making this a condition of this exemption, in combination with the condition that all practical actions be taken to eliminate or further reduce that risk, means thatgranting this exemption should not adversely affect and, in fact, should improve the average perflight-hour risk within the current transport-airplane fleet.

For those existing transport airplanes re-evaluated to date, the conditions under which an uncontrollable high-thrust failure may jeopardize the safe operation of the airplane are limited to specific aborted takeoff or approach-and-landing scenarios. Given that these scenarios occur, there is still a low probability that a serious injury will result. This limited exposure, in conjunction with the historically low occurrence rates, makes this a relatively low risk per flight

hour.

It is the spectre of this low risk per flight hour accumulating indefinitely on many, if not most, existing and future transport airplanes that is the primary concern driving development of the FAA “Thrust Control Malfunction Airworthiness Program.” To date, corrective actions under 14 CFR part 39 have been deemed warranted only when the uncorrected risks for a particular type design were considered significantly great er than those allowed by the conditions and limitations of this exemption. Given that these conditions and limitations require that any airplane certificated under this exemption have an uncontrollable high-thrust failure rate over three times better than the current fleet average, the impact of adding these GALP Model G280 fleet hours to the overall transport fleet exposure should be insignificant. Furthermore, GALP is commiting to implement thrust-malfunction-accomoda tion logic within 4 years of the date of granting, which will further reduce that risk. If , as part of the “Thrust Control Malfunction Airworthiness Program,” the FAA determines that additional, generally applicable precautions must be taken, including perhaps some future introduction of this or other design features, these precautions will further minimize any cumulative-risk impact of granting this exemption.

### 7 This exemption allows a somewhat greater hazard than full compliance with § 25.901(c). This is why the FAA intends to bring the transport fleet back into full compliance as soon as practicable. Nevertheless, the fact that the per-flight-hour risks associated with this non-compliance are low allows the FAA to develop a well-considered recovery program to assure that the solution does not introduce a problem worse than the one we are trying to solve, and that this recovery program is clearly in the public interest.

The FAA agrees with GALP that mandating retrofit of the new thrust-malfunctionaccommodation logic is not warranted, as the initial G280 airplane design is expected to provide an acceptable level of safety.

In consideration of the above, the FAA concludes that granting this time-limited exemption will not adversely affect safety.

The Grant of Exemption

In consideration of the foregoing, I find that a grant of exemption is in the public interest and will not adversely affect safety. Therefore, pursuant to the authority contained in 49 U.S.C. 40113 and 44701, delegated to me by the Administrator, Gulfstream Aerospace LP (GALP) is granted an exemption from § 25.901(c) to the extent necessary to allow type certification of the Model G280 airplanes with Honeywell AS907 engine s, without an exact showing of compliance with the requirements of § 25.901(c) or other applicable regulations as they relate to single failures resulting in uncontrollable high-thrust conditions. This exemption is subject to the following conditions and limitations:

1. GALP must demonstrate, in accordance with an FAA-approved “Airworthiness Assessment and Risk Management Plan,” that all practicable actions have been taken to minimize the adverse effects on safety associated with granting this petition. These must include, but are not limited to, practical actions to eliminate or further reduce the risks by improving designs, procedures, training, and Instructions for Continued Airworthiness (ICA).

2. GALP must demonstrate, in accordance with an FAA-approved “Airworthiness Assessment and Risk Management Plan,” that the risks associated with exempting the uncontrollable high-thrust failure condition from the single failure provisions of § 25.901(c) are no greater for the proposed Model G280 airplanes with Honeywell AS907 engines than those currently known and accepted for comparable airplanes within the current transport fleet. Acceptable risk for this provision can be characterized as:

a. The airplane complies with § 25.901(c) for any foreseeable, uncontrollable, high-thrust failure conditions in flight, except possibly during approach below 400 feet; and

b. The expected frequency of occurrence of the uncontrollable high-thrust failure condition is less than once per 10 million airplane operating hours.

### 8 3. The following “Note” will be added to the airplane Type Certification Data Sheet for any airplane certificated under this exemption:

The FAA has concluded that the occurrence of any uncontrollable high-thrust failure condition, or any of the associat ed causal failures listed within GALP Document (reference TBD), may endanger the safe operation of an airplane. Consequently, the FAA recommends that operators be encouraged to report any

such failures in accordance with Title 14, Code of Federal Regulations 121.703 (c), 125.409 (c), and 135.415 (c).

In support of this “Note,” GALP must develop and obtain, prior to customer delivery, FAA approval of the GALP document referenced in the “Note.” This document lists those failures that can contribute to or cause an uncontrollable high-thrust failure condition covered by this exemption. This document will then be made available as part of the ICA. Further, the failures listed within this document will be added to the list of reportables under 14 CFR 21.3 for any airplane certificated under this exemption.

4. No later than four years from this granting, for all airplanes to which this exemption applies,

Gulfstream must:

a. Obtain FAA approval of amended type designs incorporating thrust-malfunctionaccommodation logic that eliminates all noncompliant, uncontrollable, high-thrust failures, except for those due to failures within the airplane throttle system;

b. Show that all new Model G280 production airplanes are equipped with the amended typedesigns approved to satisfy condition 4a or any subsequently approved thrustmalfunction-accommodation logic; and

The granting of this exemption does not relieve any regulatory obligation to identify and correct unsafe conditions related to uncontrollable high-thrust failure conditions.

Note: Additional background and guidance regard ing these provisions are provided in FAA Letter 02-112-02, dated October 19, 2001.

Issued in Renton, Washington, on December 19, 2011.

/s/ K. C. Yanamura

K. C. Yanamura Acting Manager, Transport Airplane Directorate

Aircraft Certification Service