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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

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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

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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

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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.