Enclosure to A&C-12-227 

April 2, 2012 

Page 1 of 4 

Petition for Time Limited Exemption

Gulfstream Aerospace Corporation

Uncontrollable High Thrust Failure Conditions 

Model GVI

Relief from section 14 CFR Part 25.901(c) Amdt. 25- 46

Gulfstream Aerospace Corporation (Gulfstream) of Savannah, Georgia has submitted an application 

to the FAA’s Atlanta Aircraft Certification Office for type certification of a new, twin-engine, transport 

category aircraft to be known as the Gulfstream model GVI. FAA Project Number TC8700AT-T has 

been assigned to this effort. The model GVI will incorporate Rolls-Royce Deutschland BR700-725A1-

12 series engines. These engines incorporate Full Authority Digital Engine Control Systems. 

 

14 CFR section 25.901(c), Amendments 25-1 through 25-120: Requires that “. . . no single failure 

or malfunction or probable combination of failures will jeopardize the safe operation of the airplane . . 

.” 

During the development phase of the GVI, Gulfstream intended to fully comply with the requirement. 

However, failure analysis of the final design highlighted a fuel metering valve jammed condition that 

would prevent the GVI from fully demonstrating compliance for all flight conditions. During takeoff, the 

fuel metering valve could jam in the open position at higher speeds during the takeoff roll near V1. If 

this occurs and the crew elects to reject the takeoff, this could result is a runway excursion. 

In accordance with the provisions of 14 CFR 11.81, Gulfstream requests a time limited partial 

exemption to 14 CFR 25.901(c). This partial exemption would be for the extremely remote powerplant 

failure condition identified above that could adversely affect safe operation in a very limited portion of 

the flight envelope of the GVI aircraft, and its derivatives, that incorporate Rolls-Royce Deutschland 

BR700-725A1-12 series engines. Granting this exemption would permit type certification of the 

Gulfstream GVI airplane and future modifications/derivatives. 

This partial exemption, if granted, will require Gulfstream to demonstrate that the overall level of 

safety of the engine control system of the Model GVI, including future derivatives, will not be less than 

that of the current transport category aircraft fleet. 

The exemption is requested to be granted for a period of 4 years after FAA issuance. During this 

period, Gulfstream will develop and make available improved Uncontrollable High Thrust (UHT) logic. 

The improved logic will mitigate the effects of an UHT event during takeoff. Prior to expiration of the 

exemption, the engine control system modification will be certified as a design change, introduced into 

production, and all delivered airplanes will be retrofitted. 

The nature of this petition for partial exemption is similar to previously granted exemptions for Airbus 

models A340 and A318, Embraer models EMB-135BJ, EMB-145XR, ERJ 170, and ERJ 190, Boeing 

models 757 and 777, Dassault-Aviation Falcon 7X, and the Gulfstream models GIV-X, GV-SP and 

G280. 
Enclosure to A&C-12-227 

April 2, 2012 

Page 2 of 4 

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 UHT. The committee found that for the existing in-service airplanes, 

the propulsion systems demonstrated a level of reliability on the order of one UHT event per 10 million 

flight hours. The committee also noted it would not be in the public interest to mandate major and 

novel design changes in an attempt to eliminate the already small exposure potential to UHT 

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, take prompt corrective action by introducing 

focused design improvements using proven technology. 

The approach of taking action to correct specific problems as they are identified has been used 

successfully for many years on previous Gulfstream models, some of which also incorporate RollsRoyce Deutschland BR700-series engines. The Gulfstream fleet has maintained a high level of safety 

and reliability. 

Gulfstream will implement a change designed specifically to accommodate the failure as previously 

described. Full compliance with 14 CFR 25.901(c) will require Gulfstream to implement changes to 

the existing Electronic Engine Control (EEC) software to initiate engine shutdown via the overspeed 

shut-off mechanism following detection of a fuel metering valve jam, while the aircraft is on the ground 

and when the affected engine throttle is retarded to idle. 

Gulfstream intends to demonstrate that those combinations of failures that could jeopardize safe 

operation comply with 14 CFR 25.901(c) in that they are not “probable combinations1

.” However, 

Gulfstream has identified that an extremely remote single failure condition exists which could 

jeopardize safe operation with potentially severe effects. Compliance with 14 CFR 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 must be assumed to occur 

regardless of their probability2

, 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 during operating and/or environmental conditions 

that are not expected to occur. 

1

 The term “probable,” as used in § 25.901(c) has a very different meaning than the same term as subsequently 

used in association with § 25.1309(b) compliance. As used in §25.901(c), "probable" means “foreseeable”. In 

§25.1309(b) terms, this means the subject failure conditions are "anticipated to occur” (i.e., aren't "extremely 

improbable”). 

2

 Probability has been an acceptable means of supporting a finding that a particular "combination" of failures are 

not "probable". Any single failure that has an identifiable cause is typically characterized as "anticipated to 

occur", unless within the relevant exposure envelope the failure can be clearly and acceptably ruled out, as is 

the case for those structural failures specifically excepted by the rule itself. 
Enclosure to A&C-12-227 

April 2, 2012 

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Issue of Public Interest

Gulfstream designs, develops, manufactures, markets and services the world's most technologically 

advanced business jet aircraft to an international market. Gulfstream’s leadership position in the 

global business jet market is due to the efforts of its more than twelve thousand employees in the 

manufacturing plants, completion centers, and service centers across North America. The corporation 

utilizes numerous products, such as avionics and environmental control systems, from scores of 

suppliers located through out the United States. Gulfstream competes for new business all over the 

world. Granting this exemption will support the certification of the Gulfstream Model GVI aircraft in a 

timely manner, thereby having a direct effect on GVI aircraft sales. Manufacture, completion, and 

support of Gulfstream aircraft aids in the stabilization of the job market as well as the growth of the 

American economy. This is certainly in the interest of the public. 

Requiring the Model GVI to comply with this rule would prevent Gulfstream from certifying the aircraft 

on a timely and competitive schedule, putting it at an unfair disadvantage to its competitors, which 

include foreign and domestic aircraft manufacturers. During this time, sales of previously certified 

aircraft, which may also have an exemption to 14 CFR 25.901(c), will continue. This will delay the 

introduction to the public of advancements in safety brought forth by the Model GVI, not only in the 

areas of engine control, but throughout the airplane. This is counterproductive to both Gulfstream and 

the FAA’s goal of continuous improvement in overall aircraft safety. The advancement of aircraft 

safety is in the interest of the public. 

Effect of the Exemption on Safety

As stated above, Gulfstream will demonstrate that the risks due to UHT failure conditions on the GVI 

in its current configuration will not exceed those currently known and accepted for comparable 

existing transport category airplanes. This means that granting a partial exemption will not adversely 

affect and, in fact, will improve the average per flight hour risk within the current transport airplane 

fleet. For this purpose, Gulfstream analyzed the Uncontrollable High Engine Thrust failure rate data 

of the Rolls-Royce Deutschland BR700-725A1-12 series engines and performed simulated flight 

assessments of the scenarios. The results of the analysis and assessments shows that the frequency 

of occurrence of UHT event on the GVI is calculated to be ~1.3 E-8 per airplane operating hour, which 

is less than the average industry value of 1.0 E-7 per airplane operating hours.

 

Gulfstream 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 GVI 

Model aircraft. Furthermore, Gulfstream Aerospace would like to emphasize the following: 

 The GVI aft fuselage mounted engine design (i.e., relative close proximity to aircraft 

centerline) mitigates much of the adverse yaw condition that may be generated during a 

single engine UHT event on other designs. 

 The controllability assessment during UHT for conditions other than the exception noted 

below was evaluated by conservative Engineering simulations and determined to be 

compliant. 

 It was found that the GVI Model complies with 14CFR 25.901(c) for any foreseeable UHT 

failure conditions, except for in a very limited scenario: 
Enclosure to A&C-12-227 

April 2, 2012 

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o RTO conditions where the malfunction occurs at higher speeds during takeoff roll near 

V1. 

 Enhanced FADEC software is in development and will be incorporated in the GVI aircraft. 

Gulfstream has verified that the Model GVI exposures and failure rates are such that this airplane will 

not exceed the known average per flight-hour risks of comparable existing transport airplanes. Making 

this statement a consideration of this exemption request, in combination with the condition to further 

minimize the risk, means that granting this exemption will 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 GVI aircraft, Gulfstream will develop 

and obtain FAA acceptance of the instructions for continued airworthiness. Further, the Uncontrollable 

High Engine Thrust failures shall be considered reportable to the FAA under 14 CFR Part 21.3 for any 

airplane certificated under this exemption. 

Waiver of Notice and Public Procedure

Gulfstream respectfully requests that action on this petition should not be delayed by publication of a 

summary of our petition and associated comment period. We believe that the nature of this exemption 

does not set a precedent, the relief requested herein is effectively identical to exemptions previously 

granted, and delay of granting this exemption will unnecessarily delay final certification of the Model 

GVI. 

Operation Outside of the United States

Gulfstream requests consideration be given to extending this exemption for operation outside of the 

United States. Gulfstream aircraft are routinely registered and operated outside of the United States 

and projections are the same for the model GVI. Gulfstream believes that limiting this exemption to 

use within the U.S. would put unfair restrictions on the marketability of this aircraft. 

Conclusion

Gulfstream believes that the above arguments favor a time-limited, partial exemption from 14 CFR 

25.901(c) for the aft-fuselage-mounted installation of the Rolls-Royce Deutschland BR700-725A1-12, 

FADEC-controlled engines on the Gulfstream Model GVI aircraft and its derivatives. Gulfstream 

believes that an exemption is in the public interest and will not adversely affect the current transport 

airplane fleet safety.