GE Flight Ops Newsletter 2006

Flight Operations Newsletter GE AviationVolume 1, Issue 1 Fall 2006

The information contained in this document is GE proprietary information and is disclosed in confidence. It is the property of GE and shall not be used, disclosed to others or reproduced without the express written consent of GE, including, but without limitation, it is not to be used in the creation, manufacture, development, or derivation of any repairs, modifications, spare parts, designs, or configuration changes or to obtain FAA or any other government or regulatory approval to do so. If consent is given for reproduction in whole or in part, this notice and the notice set forth on each page of this document shall appear in any such reproduction in whole or in part. The information contained in this document may also be controlled by the U.S. export control laws. Unauthorized export or re-export is prohibited.

GE PROPRIETARY INFORMATION

Flight Ops Newsletter is published by:

GE Flight Operations Support

1 Neumann Way, Room 300

Cincinnati, OH 45215

Editor: Walt Moeller

[email protected]

Phone: (513) 552-6602

Copyright 2006

To all of our Aviation customers, we’re pleased to welcome you to our first edition of the GE Aviation Flight Operations Newsletter. The industry in which we operate has seen dramatic changes in recent years, and as we move forward, one major aim is to be more proactive in sharing technology updates and best practices that will ultimately help your operations. This newsletter is a key part of that process. Our goal is to provide engine technical and operational information in a way that is familiar to pilots and flight operations personnel. We hope you will find this information to be beneficial.

Periodically, we will publish this newsletter to bring you updates on new engine technology, operational recommendations and other best practices related to engine operation. Please take a look and let us know if there are any topics that you would like covered in a future issue or if you have any recommendations on how to make this a better publication.

Welcome!

GE Flight Operations Support -A Brief Introduction

In this issue:• Welcome!

• GE Flight Operations Support – A

Brief Introduction

• Engine Power Loss Associated with

Ice Crystal Exposure

• Fuel Conservation

• Engine Warm-up and Cool-down

Times

• The Fleet Logbook

• Inclement Weather Operations

• Introducing the GEnx

GE Flight Operations Support is a part of the GE Aviation Customer and Product Support Organization based in Cincinnati, Ohio. Our primary focus is providing operational support which involves continuous interfacing between the operators, aircraft manufacturers, internal engine experts and regulatory agencies. In addition to providing engine specific training, we regularly answer operator questions, occasionally conduct operational reviews -sometimes through jumpseat observations, and help implement best practices in areas like fuel conservation, increased reduced thrust usage, FOD reduction, etc. In much the same way as airlines are typically involved in the initial design of new aircraft types, we are heavily involved in the engine design process. With continuous feedback from you, the operator, we play a very important role in promoting engine designs that are practical and “user friendly” to the ultimate end user, the pilots. Please meet our crew:

Capt. John Gough is Director of GE Flight Operations Support and has been with GE Aviation since 2004. John has 12 years of airline operational experience, most recently as a captain for a major US airline, and prior flew 10 years in the USAF. He is type rated in the B777, A330 and B737. John can be reached at: (513) 552-4406 or [email protected]

Capt. Andy Mihalchik has been with GE Aviation for 31 years and is currently responsible for all CFM, GP7200 and GEnx applications. Andy has an extensive background in engineering, has been flying for 33 years, and is type rated in the A330 and CRJ700. Andy can be reached at: (513) 552-2737 or [email protected].

Capt. Walt Moeller joined GE Aviation in 1987 as a design engineer and is currently responsible for CT7, CF34-8E, -10E, -10A and GE90 applications. Walt has been flying for 26 years including 14 years of airline operational experience, most recently as a captain for a major US airline, and is type rated in the B777 and CRJ200. Walt can be reached at: (513) 552-6602 or [email protected].

Capt. Jim Waggoner joined GE Aviation in 2005 and is currently responsible for all CF6, CF34-3 and CF34-8C applications. Jim has 13 years of operational experience with a major US airline and prior flew 8 years in the USN. He is type rated in the B757/767 and CRJ700. Jim can be reached at: (513) 552-6546 or [email protected].

Volume 1, Issue 1 Fall 2006

Page 2

Engine Power Loss Associated with Ice Crystal ExposureGE has been investigating several engine power loss events associated with flight in inclement weather, more specifically, flight in or near what is suspected to be an ice crystal environment. While it appears that the power loss events are not unique to GE engines, there have been several CF6-80 events since the early 1990’s, in a period covering more than 12.5 million departures and over 128 million flight hours. In all cases, the engines relit and normal power was restored. In some cases the flight crews were unaware that a momentary power loss had occurred. This article is intended to share information relative to the events and our investigation so that operators have a better understanding about the ice crystal environment and potential operational considerations to minimize engine effects due to ice crystal exposure.

engine. Deep convective weather systems, characterized by significant lifting and cumulonimbus clouds with very high cloud tops, may have a combination of ice crystals and supercooled droplets. These deep convection weather systems may contain ice crystal concentrations estimated to be up to 9 grams per cubic meter or nearly 4.5 times the maximum supercooled liquid concentration of 2 grams per cubic meter, which is the basis for current engine icing certification testing.

Event Reports – Common Characteristics

Pilot reports and engine data have been obtained from a number of the engine events. Typically the engine power loss events occurred during acceleration following prolonged low power descent with the following similar characteristics:

•In or near convective weather with visible moisture

•Light to moderate turbulence was often reported

•“Heavy rain” was often reported at very high altitudes and at ambient temperatures below freezing

•Little and often no radar detection at event altitudes

•No significant airframe icing. In most cases, icing conditions were typically not detected/indicated by the aircraft ice detectors

• Total air temperature (TAT) significantly different than expected and often near zero degrees C several minutes just prior to the engine flameout.

•Event altitudes ranged from 11,500 feet to 36,000 feet

Understanding the Engine Effects

Investigation of engine related effects resulting from ice crystal ingestion suggests that the ice crystals melt quickly within theengine forming a liquid film on surfaces, eventually capturing more ice crystals. It is suspected that during prolonged operation in an ice crystal environment, ice crystals are accumulating in the first several stages of the engine core. Asengine power is increased the accumulated ice suddenly sheds with some of the ice shed leaving through the open variable bleed valves (VBV’s) and some of the ice shed continuing into the core. In rare cases, the shed ice travels through the compressor, changing state, causing the combustor inlet characteristics to change rapidly (see article on water ingestion later in this newsletter) resulting in an engine flame-out or brief power loss. This shed typically occurs within 2 to 3 seconds after power is advanced during level off. In all cases, the engines have always relit and continued normal operations.

The Ice Crystal Environment

Investigation of recent engine power loss events has shown that some of the events have occurred in or near convective weather above the altitudes typically associated with icing conditions. Research has shown that these same convective weather systems can contain very small crystals of frozen water. These “ice crystals” can be extremely small (the size of several grains of flour) and do not typically adhere to very cold airframe surfaces, instead bouncing off. For this reason, ice crystal conditions are often not detected by the aircraft ice detectors. It is believed that the ice crystals may partially melt and refreeze on warmer surfaces similar to those inside the


Page 3

Engine Modifications

Extensive engine testing and research has shown that ice ingestion into the core of the engine can be minimized by allowing shed ice to discharge out of the VBV’s as shown above. During low power operation, the VBV’s are commanded open. As the engine accelerates the VBV’s are closed. New FADEC logic will slow the rate of VBV closure during accels allowing more of the ice that was actually shed during the accel to leave the engine through the open VBV doors into the fan stream. Similar engine logic has been very effective at lower altitudes. Testing has shown that the revised VBV logic can also provide similar benefits at higher altitudes.

A CF6-80C2 engine undergoing extensive ice ingestion testing in early 2006 to help identify the cause of suspected ice crystal related flameouts.

Avoiding Adverse Ice Crystal Effects

Although there has been an extensive amount of research and engine testing related to ice crystal exposure the best approach to minimizing engine related effects is to minimize exposure to the ice crystal environment as described earlier. If flight into or near a suspected ice crystal environment can not be avoided flight crews should consider the following:

•Follow specific operational guidance provided by the aircraft manufacturers.

•Turn on continuous ignition if the aircraft/engine do not have an auto-relight system installed.

•Combustor flame-out resistance may be increased by increasing engine bleed air extraction to create a higher fuel-to-air ratio.

•If practical, reduce engine “scoop factor” (see included article) prior to actually entering inclement weather conditionsto minimize engine water/ice ingestion.

•The probability of a sudden ice shed within the engine may be minimized if thrust fluctuations are avoided and a constant thrust level is maintained.

Extensive research and analysis continues at GE to better understand the ice crystal environment and its effect on jet engines. Updated information will be published in this newsletter and other GE publications when available. Any additional information that operators can provide is welcome in our continuing investigation. For more information please contact Capt. Jim Waggoner at (513) 552-6546 or [email protected]

20GE Aviation

Sequence of Ice Crystal Flameout Event

4 Ice changes state thru HPC, melting, evaporation

5 Combustor inlet air temperature depressed, Combustor efficiency drops

6 Flameout occurs

4

5

6


Page 4

Fuel ConservationThe rapid increase in fuel prices over the last several years has affected all operators. GE has formed a fuel burn cluster group, which is studying this issue from every angle to include:new engine technologies, improved maintenance practices, different operational considerations and other suggestions to flight crews for the optimized use of the engines. The following information may be beneficial in reducing fuel consumption at your operation.

New Engine Technologies

A primary focus of new engine designs is significantly reducing fuel burn. The advanced combustor design and other features of our new GEnx engine powering the B787, B747-8 and A350 will help reduce specific fuel consumption (SFC) nearly 15% compared to the CF6-80C2 and nearly 7% compared to our more modern GE90-94B. The CFM56 Tech Insertion program will be introducing new technologies in existing CFM56 engines which will improve specific fuel consumption (SFC) and increase time-on-wing by increasing EGT margin. Engine improvements are also underway for existing CF6-80C2/-80E1 engines called “Tech CF6” that will improve fuel burn retention while reducing maintenance costs. All of these new technologies will help reduce operational costs and will also improve engine time-on-wing to reduce overhaul costs. These new engine designs are integral to our GE “Ecomagination” initiative with a commitment to being “green”through less fuel burn and lower emissions.

Improved Maintenance Practices

One of the best and simplest ways to reduce engine fuel burn is the use of water wash. The water wash process is simple, typically does not require any engine hardware changes, and is accomplished by spraying water or water/detergent mix into the engine core while the engine is dry-motored. The water wash cleans the core of the engine by removing accumulated dirt and contamination from the engine airfoil surfaces. The result is a much more efficient engine which generally has higher EGT margin and better SFC after the wash process. Typically, for every 10 degrees of EGT margin loss, fuel flow efficiency decreases approximately 0.6-0.8% SFC, so keeping the engine “clean” is essential to fuel savings. In addition to lower fuel burn, the obvious side effect of increased EGT margin is increased time-on-wing.

Proactively Monitoring the Fleet with GE Diagnostics

Operators are increasingly aware of the tremendous resource that GE’s Diagnostics tool can be in reducing fuel burn. EGT or ITT trending can identify bleed air leaks and other engine conditions that can reduce engine efficiency. Unidentified bleed air leaks as a result of a valve change or other maintenance can increase fuel burn and decrease EGT margin. Diagnostics can help identify these inadvertent leaks much more quickly, saving fuel, compared to finding the leak at the next scheduled maintenance check. The basic GE Diagnostics tool is available free of charge to all GE engine operators.

Reduced Thrust Takeoffs

An excellent way to preserve engine efficiency and reduce overall fuel burn is to maximize the use of reduced thrust takeoffs. Reduced thrust takeoffs using fixed derates, assumed temperatures or a combination result in less severe operating temperatures, pressures and rotational speeds for the engine components which results in less wear, better EGT margin retention, better SFC retention and ultimately longer time-on-wing. The concept of reducing thrust for a takeoff is counterintuitive to most pilots and the theory associated with the assumed temperature method for thrust and performance calculations is often misunderstood. Several of the aircraft manufacturers have published excellent material covering reduced thrust operations specific to their aircraft. We also have engine related material to help explain the concept and significant benefits of reduced thrust operations.

Human Factors

The highest exposure to excessive engine deterioration comes at the hands of the human operators. Both pilots and maintenance technicians are equally qualified to cause excessive deterioration by using aggressive thrust lever or power lever movements. Rapid thrust lever or power lever bursts or chops cause rapid thermal changes to occur between the more massive internal rotating components and the less massive external engine cases. The different thermal expansion characteristics combined with centrifugal forces may result in turbine “rubs” that actually remove material from the turbine blades decreasing turbine efficiency and increasing fuel burn. Operators are encouraged to teach pilots and maintenance technicians that smooth, and deliberate thrust/power lever movements are essential in preserving engine efficiency. Rapid thrust lever movements should simply be avoided whenever practical.


Page 5

Engine-Out Taxi

Many of our customers are using engine-out taxi as a means to save fuel. There are many factors to evaluate when considering engine-out taxi operations. GE neither advocates or discourages engine-out taxi operations. We encourage all operators to consider the aircraft systems effects of engine-out taxi operations and also ask that operators consider engine related operational requirements like minimum warm-up times, minimum cool-down times and FOD prevention in the overall evaluation of engine-out operations. Additional information on engine warm-up and cool-down may be found in this newsletter. The aircraft manufacturers have their own procedures and recommendations regarding engine-out taxi and are the final authority as to how the engine is operated on each particular aircraft installation.

From an engine only perspective, engine-out taxi operations may result in considerable fuel burn reduction especially on larger fleets. The table below contains some typical all enginevs. engine-out taxi comparisons for a total 20-minute taxi time (assuming 10 minute taxi-in and 10 minute taxi-out).

$1957561440GE90

$27110502000CF6-80C2

(4 Eng. Appl.)

$128494940CF6-80C2

(2 Eng. Appl.)

$68263500CFM56

(2 Eng. Appl.)

$60231441CF34

Estimated Savings @ $2.00 per Gallon

Engine-Out Taxi Fuel Required

(lbs)

All Engine Taxi Fuel Required

(lbs)

Engine

Type

Optimizing Reverse Thrust

An additional means to save fuel during flight operations is optimizing the use of reverse thrust when operating conditions allow. Again, it is important to consider all FCOM, performance, airline and safety procedures in the evaluation of the amount of reverse thrust to use. Obviously the benefit of reduced fuel burn and reduced FOD ingestion associated with lower than maximum reverse thrust must be weighed against operational requirements, the potential for increased brake wear and the operational considerations associated with the potential for increased brake temperatures. The potential fuel savings, assuming idle reverse thrust is used on all engines for 20 seconds, are shown below.

$43149GE90

$76267CF6-80C2

(4 Eng. Appl..)

$38133CF6-80C2

(2 Eng. Appl..)

$930CFM56

(2 Eng. Appl..)

$1139CF34

Estimated Savings

@ $2.00 per Gallon

Idle Reverse

Fuel Burn

Reduction

(lbs)

Engine

Type

One of the fastest growing cost at most airlines is fuel. It is important flight crews become fully involved in fuel conservation and take ownership. This may help reduce operating costs at your airline.

If you have any other recommendations or wish GE Flight Operations Support to come to your airline to give a presentation on the optimized use of the engines, please contact me, Capt John Gough at 513-552-4406 or [email protected].

The fuel savings above are approximate and may vary with different installations, aircraft loading, etc.

The fuel burn reduction estimates above are approximate and may vary with different installations, aircraft loading,

etc.


Page 6

Engine Warm-Up and Cool-Down Times In recent years more and more operators are using engine-out taxi procedures as a way of reducing costs. In addition, shorter quick-turn times aimed at increasing aircraft utilization are usually resulting in less observance of the minimum warm-up and cool-down times. While it is true that fuel burn can be reduced by minimizing engine run time on the ground, it is important that flight crews understand the importance of proper engine warm-up and cool-down times so that more costly engine maintenance and/or in-flight events can be avoided.

Warm-up Time

The engine warm-up time is used to help thermally stabilize the engine components prior to takeoff thrust application. Rapid thrust advance on a cold soaked engine may increase the potential for turbine blade rubs which increase engine deterioration and increase fuel burn. In addition, some operators have found that increasing the first flight of the daywarm-up time, from 2 minutes to 5 minutes for example, can minimize the potential of an EGT exceedance during takeoff, especially on older non-FADEC engines.

Cool-down Time

The engine cool-down time is also intended to thermally stabilize the engine prior to shutdown. Insufficient cool-down times may result in increased oil system coking and/or increased fuel nozzle coking. Oil system coking, shown below, occurs when the oil flow from the engine driven oil pump is reduced after shutdown allowing the stagnant oil to basically bake in the tube which is exposed to the high soak-back temperature. Increasing cool-down time will help reduce this soak-back temperature and minimize coking. Insufficient

2 min.2 min.CT7

3 min.3 min.GE90

3 min.3 min.CF6

3 min.2 min.CFM56

2 min.2 min.CF34

Cool-down TimeWarm-up TimeEngine

cool-down times may also increase the probability of a bowed rotor start during the subsequent start. The bowed rotor condition is caused by high soak-back temperature and the decreasing air flow within the nacelle after shutdown. As thehot air rises within the nacelle the lower part of the engine rotor system cools more rapidly than the top causing a very slight bow of the high pressure and/or low pressure rotor. Although it is typically not detrimental to the engine, a bowed rotor start may result in increased vibration during the early portion of the next start until the airflow within the engine increases, thermally stabilizing the engine components. The highest probability of a bowed rotor start is typically 20 minutes to several hours after engine shutdown.

The typical normal operation warm-up and cool-down times for the various engine families are shown below. Specific operations, like high power maintenance runs or other operations may require longer times than shown. Please refer to the aircraft operations documents or engine maintenance documents specific to the aircraft and engine configuration you are operating for specific warm-up and cool-down requirements. For more information please contact Capt. Walt Moeller at (513) 552-6602 or [email protected]

The photo on the left shows a typical oil system component clogged by accumulated coke which is shown in detail on the right. Total oil flow blockage may result in increased bearing wear.

The Fleet Log BookA brief summary of engine hours to date.

1003

28

252

564

56

103

No. of Operators

67986640227556Totals

7790227483GE90

2923408306677CF6

32298463115763CFM56

306408183013CF34

261098961620CT7

Cumulative Engine Hours

No. of Engines

Engine Family

The normal times above take into consideration the typical power/thrust increases associated with aircraft taxiing.


Page 7

Fuel flow (WF)/Burner Pr essure

(PS3))

RollbackOperating line with extremely high wateringestion

Accel schedule

Operating line dry

Decel schedule

Core speed (N2)

One effect that many flight crews do not understand is the relationship between aircraft speed and engine speed and their combined effect on water/ice ingestion and engine operability.

“Scoop Factor”

The typical flight crew response to encountering turbulence or heavy rain associated with convective weather is to slow the aircraft down to the maximum turbulence penetration speed by reducing thrust. During encounters with rain and/or hail, reducing engine RPM at higher aircraft speeds increases inlet air “spillage” as shown below. The result is that the water-to-air ratio at the engine face increases creating a more severe operating environment for the engine. At lower aircraft speeds and higher engine RPM this air spillage is not as great and the water-to-air ratio at the engine face decreases.

Engine Operation in Inclement Weather

Lower engine RPM at a higher aircraft speed results in lighter air particles “spilling” around the inlet while the heavier water particles maintain their trajectory into the inlet.

In comparison, higher engine speed at lower aircraft speed results in less air “spillage” and a lower water-to-air ratio at the engine face in the same weather conditions.

Changing water from a solid or liquid state to a gaseous state requires energy just like boiling water on a stove. When water or ice enters the engine core the energy required to vaporize the ingested water must be recovered or the net effect will be a reduction in the energy available at the turbine to drive the compressor and fan, or in simpler terms, a reduction in thrust. The engine control responds during water/ice ingestion by increasing fuel or “enriching” the fuel to burner air pressure ratio as shown below. This ratio plotted as a function of N2 or“operating line” for a dry engine is lower than the operating line for a wet engine. As the engine water-to-air ratio increases further the engine control will keep commanding more fuel until reaching the accel schedule. At this point, fuel is limited and the engine begins to rollback along the accel schedule reducing thrust. A flameout may eventually occur if engine core speed (N2) continues to decrease with the same level of water ingestion as depicted below.

The engine basically has two fuel schedules: an accel schedule and a decel schedule. The accel schedule is basically a maximum fuel flow which varies with core speed and the decel schedule is basically a minimum fuel flow rate that also varies with core speed. The engine fuel schedules are based

Engine Fuel Schedules

Engine Operation During Water and Ice Ingestion

Minimizing the Effect of Water, Hail or Ice Ingestion

The simplest way to minimize the effect of water ingestion is to reduce the amount of water ingested by lowering the “scoop factor”. Quite simply, if inclement weather can not be avoided, it is better, from an engine perspective, to reduce aircraft speed and increase engine core speed prior to entering the inclement weather conditions. For more information please contact Capt. Walt Moeller at (513) 552-6602 or [email protected]

Comparison of dry and wet operating lines. The wet (red) operating line represents operation in an extreme water environment that may be worse than defined certification levels at lower core speeds.

on successful operability testing to predefined certification standards that are established by the regulatory agencies to reflect worst case historical meteorological conditions.


Page 8

A fundamental design requirement for the GEnx was versatility. By versatility, we mean the ability to provide essentially common hardware capable of operating at multiple thrust ratings and an un-compromised solution for both no-bleed and bleed applications.

.

Introducing theThe GEnx is GE’s next generation, 2 spool, turbofan in the 53,000 – 75,000 lb. thrust class. It will be the workhorse engine of the 21st century for medium and large-capacity, long-range aircraft. The GEnx will deliver up to 15% better specific fuel consumption, stay on wing 20% longer, and use 30 percent fewer parts than earlier engines. The GEnx’semissions will be up to 95% below current regulatory limits, ensuring compliance for years to come.

Innovative and Versatile Engine Design

Coneliptical Spinner

for improved inclement weather characteristics

Super-high Bypass Fan•With 18 high-flow, swept, wide-chord, virtually maintenance free composite fan

blades similar to GE90 fan blades with unprecedented performance – only three GE90 blade removals from service in more than 7 million flight hours even after multiple large bird strikes.

•Quietest GE engine ever in its class with 30% less noise than its predecessors for an enhanced cabin/flight deck environment

Composite Fan Case for superior damage tolerance with less weight

Advanced, Stall-free, HP Compressor•Highest pressure ratio in aviation history (23:1) in only 10 stages

•Innovative bleed and no-bleed configurations

•Traditional power off-take for accessory drives

Unique FOD Rejection System results in a FOD-free core.

Advanced Engine Diagnostics

•Electronic oil system debris monitoring

•Advanced vibration monitoring

•Fuel system trending

•Improved starter/ignitor health detection

•Enhanced performance trending

•Improved troubleshooting capabilities

Advanced Combustor Technology for leaner fuel burn and lower emissions

3D Aero Turbine Designs with Counter-rotating Spools for increased efficiency and lower weight

On Track for the 21st Century

The first GEnx-1B engine began testing ahead of schedule on March 19th, 2006. In less than 2 days, the engine achieved 80,500 lbs of thrust. The second phase of testing is under way focusing on starting, transient characteristics, fuel system scheduling and overall performance. The GEnx has already successfully demonstrated the capability to start with one starter-generator inoperative, an important aircraft manufacturer requirement. For additional information please contact Capt. Andy Mihalchik at (513) 552 2737 or [email protected]. To see an interactive presentation please go to the following site:

http://www.geae.com/education/theatre/genx/

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GE Flight Ops Newsletter 2006