Flight Crew Training Manual
Climb, Cruise, Descent & Holding

Amendment: Notes relating to Cruise CG entry on the PERF INIT page.

Preface

This chapter outlines recommended operating practices and techniques used during climb, cruise, descent and holding. Loss of an engine during climb or cruise and engine inoperative cruise/drift-down is also addressed. The recommended operating practices and techniques discussed in this chapter improve crew coordination, enhance safety, and provide a basis for standardization.

Climb

Reduced Thrust Climb

Engine service life may be extended by operating the engines at less than full climb rated thrust.

The Thrust Management Computer (TMC) or the FMC THRUST LIMIT page (as installed) provides two reduced thrust climb selections:

Reduced thrust climb may also be automatically selected by the TMC depending upon the amount of thrust reduction made for takeoff when using the fixed derate method (as installed). If the thrust reduction for takeoff is made using the assumed temperature method, there is no automatic selection of reduced thrust climb.

Climb thrust reductions are maintained throughout the climb profile. If rate of climb should drop below approximately 500 feet per minute, the next higher climb rating should be selected.

Prior to takeoff, if the pilot overrides the automatically selected climb thrust limit (as installed) after the takeoff selection has been completed, the takeoff derate (as installed) is also change. To override the automatically selected climb thrust limit without changing the takeoff derate, wait until airborne. After the climb is established, select the desired climb thrust mode on the Thrust Mode Select Panel (TMSP).

Note: Use of reduced thrust for climb increases total trip fuel and should be evaluated by each operator.

Climb Constraints

Climb constraints may be automatically entered in the route when selecting a procedure, or manually entered through CDU entry. When the airplane levels off at an MCP altitude, that altitude is treated as a climb constraint by the FMC.

All hard altitude climb restrictions, including “at or below” constraints, should be set in the MCP altitude window. The next altitude may be set when the restriction has been satisfied, or further clearance has been received. This procedure provides altitude alerting and assures compliance with altitude clearance limits.

When relieved of constraints by ATC, use of FLCH or VNAV with MCP altitude intervention (as installed) is recommended in congested areas, or during times of high workload. Altitude intervention (as installed) is accomplished by selecting the next desired altitude in the MCP altitude window, pushing the MCP altitude selector which deletes the altitude constraint and allows the airplane to climb to the MCP altitude.

Low Altitude Level Off

Occasionally a low altitude climb restriction may be required after takeoff. This level-off altitude should be placed in the MCP altitude window. When the airplane approaches this altitude with TO as the engaged pitch mode FMA, the pitch mode FMA changes to ALT CAP and the AutoThrottle FMA re-engages into EPR or N1 (as installed). This prevents the thrust levers from rapidly retarding to target the airspeed selected in the IAS/Mach speed window, which is normally set to V2 for takeoff. ALT CAP occurs as a function of climb rate. The higher the climb rate to the MCP altitude, the sooner ALT CAP engagement occurs. For example, takeoff from sea-level to a 1,000 feet level off altitude results in the pitch mode FMA changing from TO to ALT CAP as low as approximately 400 feet AGL.

During the low-altitude level off, the following technique allows the autothrottle FMA to engage into SPD for proper airspeed control and prevent excessive airspeed increase near the flap placard speed range:

Note: For airplanes with manual climb thrust selection, the CLB switch on the Thrust Mode Select Panel (TMSP) must be selected prior to engaging autothrottle SPD mode to preclude exceeding autothrottle climb thrust limits.

High Takeoff Thrust - Low Gross Weight

When accomplishing a low altitude level off following a takeoff using high takeoff thrust and at a low gross weight the crew should consider the following factors:

  • altitude capture can occur just after liftoff due to the proximity of the level off altitude and the high climb rate of the airplane
  • the AFDS control laws limit F/D and autopilot pitch commands for passenger comfort
  • there may not be enough altitude below the intended level off altitude to complete the normal capture profile and an overshoot may occur unless crew action is taken.

To prevent an altitude and/or airspeed overshoot, the crew should consider doing one or more of the following:

  • use reduced thrust for takeoff at low weights whenever possible
  • reduce from takeoff to climb thrust earlier than normal
  • disconnect the AFDS and complete the level off manually if there is a possibility of an overshoot
  • use manual thrust control as needed to manage speed and prevent flap overspeeds.

Transition to Climb

Maintain flaps up maneuvering speed until clear of obstacles or above minimum crossing altitudes. If there are no altitude or airspeed restrictions, accelerate to the desired climb speed schedule. The sooner the airplane can be accelerated to the climb speed schedule, the more time and fuel efficient the flight.

Climb Speed Determination

Enroute climb speed is automatically computed by the FMC and displayed on the CLIMB and PROGRESS pages. It is also displayed as command speed when VNAV is engaged. Below the speed transition altitude the FMC targets the transition speed limit stored in the navigation data base for the departure airport (250 knots below 10,000 ft MSL), or flaps up maneuvering speed, whichever is higher. The FMC applies waypoint-related speed restrictions displayed on the LEGS pages, and altitude-related speed restrictions displayed on the CLIMB page.

The FMC provides optimum climb speed modes for economy (ECON) operation and engine out (ENG OUT) operation. These optimum speeds can be changed before or during the climb. Reference speeds are also provided for maximum angle climb (MAX ANGLE) operation.

Climb Speed Determination The ECON climb speed is a constant speed/constant Mach schedule optimized to obtain the minimum airplane operating cost. The constant Mach value is set equal to the economy cruise Mach calculated for the cruise altitude entered in the FMC.

For very low cruise altitudes the economy climb speed is increased above normal values to match the economy cruise speed at the entered cruise altitude. For ECON climb, the speed is a function of gross weight (predicted weight at top of climb), predicted top of climb wind, predicted top of climb temperature deviation from ISA, and cost index.

Engine Icing During Climb

Engine icing may form when not expected and may occur when there is no evidence of icing on the windshield or other parts of the airplane. Once ice starts to form, accumulation can build very rapidly. Although one bank of clouds may not cause icing, another bank, which is similar, may cause icing.

Note: The engine anti-icing system should be turned on whenever icing conditions exist or are anticipated. Failure to follow the recommended anti-ice procedures can result in engine stall, over-temperature or engine damage.

Economy Climb

Economy Climb Speed Schedule The normal economy climb speed schedule of the FMC minimizes trip cost. It varies with gross weight and is influenced by cost index. The FMC generates a fixed speed schedule as a function of cost index and weight.

Economy climb speed normally exceeds 250 knots for all gross weights. FMC climb speed is limited to 250 knots below 10,000 ft (FAA Airspace), or a lower waypoint speed restriction, if entered. If the use of a higher speed below 10,000 ft is allowed, ECON speed provides additional cost savings (equivalent to a fuel saving of approximately 100 kg).

Question: Does Jeppesen take this into account?

Economy Climb Schedule - FMC Data Unavailable

Maximum Rate Climb

A maximum rate climb provides both high climb rates and minimum time to cruise altitude. Maximum rate climb can be approximated by using the following:

Note: The FMC does not provide maximum rate climb speeds.

Maximum Angle Climb

The FMC provides maximum angle climb speeds. Maximum angle climb speed is normally used for obstacle clearance, minimum crossing altitude or to reach a specified altitude in a minimum distance. It varies with gross weight and provides approximately the same climb gradient as flaps up maneuvering speed.

Engine Inoperative Climb

The engine inoperative climb speed is approximately maximum angle climb speed and varies with gross weight and altitude. At high altitudes and weights, a fixed Mach is used as an upper limit on the engine out climb speed. Engine out climb speed is the FMC default used during climb when ENG OUT CLIMB is selected. Select ENG OUT CLIMB after flap retraction and all obstructions are cleared.

If a thrust loss occurs at other than takeoff thrust, set maximum continuous thrust on the operative engine and adjust the pitch to maintain airspeed.

Note: Selecting CON on the TMSP moves the N1/EPR bug to maximum continuous thrust until another mode is selected or automatically engaged. Thrust must be manually set.

In the clean configuration, select the engine out prompt on the CDU CLIMB page. The engine out mode provides VNAV commands to climb at engine out climb speed to cruise altitude, or maximum engine out altitude, whichever is lower. If the airplane is currently above maximum engine out altitude, drift-down information is available. Upon reaching level off altitude, the command speed changes to engine out LRC. Leave thrust set at maximum continuous thrust until airspeed increases to the commanded value.

Note: If computed climb speeds are not available, use flaps up maneuvering speed and maximum continuous thrust.

Cruise

This section provides general guidance for the cruise portion of the flight for maximum passenger comfort and economy.

Maximum Altitude

MAXimum altitude is the highest altitude at which the airplane can be operated. It is determined by three basic characteristics, which are unique to each airplane model. The FMC predicted MAXimum altitude is the lowest of:

Although each of these limits are checked by the FMC, available thrust may limit the ability to accomplish anything other than relatively minor maneuvering. The amber band limits do not provide an indication of manoeuvre capability as limited by available thrust.

The minimum manoeuvre speed indication on the speed tape (as installed) does not guarantee the ability to maintain level flight at that speed. Decelerating the airplane to the amber band may create a situation where it is impossible to maintain speed and/or altitude because as speed decreases airplane drag may exceed available thrust, especially while turning. Operators may wish to reduce exposure to this situation by changing the FMC parameters (via maintenance action) to suit individual operator needs. Flight crews intending to operate at or near the maximum operation altitude should be familiar with the performance characteristics of the of the airplane in these conditions.

To get the most accurate altitude limits from the FMC, ensure the following entries are accurate:

Cruise CG Cruise CG is entered on the PERF INIT page and affects the calculated MAX ALT. If a forward CG is entered, the aircraft will have a lower MAX ALT than if an aft CG is entered. For best performance without sacrificing buffet margin, enter the lower of MACTOW and MACZFW.

Note : The entry of CG on the TAKEOFF REF page is unrelated to Cruise CG and is used for calculating STAB TRIM (using the same lookup table as provided in the QRH).

When at or near the FMC MAXimum altitude, it is possible for LNAV inputs to exceed the capability of the airplane. This could result in a loss of altitude or airspeed.

For LNAV operation, the FMC provides a real-time bank angle limiting function. This function will protect the commanded bank angle from exceeding the current available thrust limit. This function is only available when in LNAV.

For operations other than LNAV, fly at least 10 knots above the lower amber band and use bank angles of 10° or less when operating at or near maximum altitude. If speed drops below the amber band, immediately increase airspeed by doing one of the following:

Turbulence at or near maximum altitude can momentarily increase the airplane's angle of attack and activate the stick shaker. When flying at speeds near the lower amber band, any maneuvering increases the load factor and further reduces the margin to buffet onset and stick shaker.

FMC fuel predictions are not available above the FMC MAXimum altitude and are not displayed on the CDU. VNAV is not available above FMC MAXimum altitude. Fuel burn at or above maximum altitude increases. Flight above this altitude is not recommended.

Optimum Altitude

OPTimum altitude is the cruise altitude for minimum cost when operating in the ECON mode, and for minimum fuel burn when in the LRC or pilot-selected speed modes. In ECON mode, OPTimum altitude increases as either airplane weight or cost index decreases. In LRC or selected speed modes, OPTimum altitude increases as either airplane weight or speed decreases. On each flight, OPTimum altitude continues to increase as weight decreases during the flight.

For shorter trips (less than 250 nm), OPTimum altitude as defined above may not be achievable since the Top of Descent (T/D) point occurs prior to completing the climb to optimum altitude.

Trip altitude, as defined on the PERF INIT page, further constrains OPTimum altitude by reducing the altitude for short trips until minimum cruise segment time is satisfied. This minimum cruise time is typically one minute, but is operator selectable in the FMC by maintenance action.

Flight plans not constrained by short trip distance are typically based on conducting the cruise portion of the flight within plus or minus 2000 ft of OPTimum altitude. Since the OPTimum altitude increases as fuel is consumed during the flight, it is necessary to climb to a higher cruise altitude every few hours to achieve the flight plan fuel burn. This technique, referred to as Step Climb Cruise, is typically accomplished by initially climbing 2000 ft above OPTimum altitude and then cruising at that flight level until 2000 ft below optimum. For most flights, one or more step climbs may be required before reaching T/D. It may be especially advantageous to request an initial cruise altitude above optimum if altitude changes are difficult to obtain on specific routes. This minimizes the possibility of being held at a low altitude/high fuel consumption condition for long periods of time. The requested/accepted initial cruise altitude should be compared to the thrust limited or the manoeuvre margin limited altitudes. Remember, a cruise thrust limited altitude is dependent upon the cruise level temperature. If the cruise level temperature increases above the chart value for gross weight, maximum cruise thrust will not maintain desired cruise speed.

The selected cruise altitude should normally be as close to optimum as possible. OPTimum altitude is the altitude that gives the minimum trip cost for a given trip length, cost index, and gross weight. It provides approximately a 1.5 load factor (approximately 48° bank to buffet onset) or better buffet margin. As deviation from optimum cruise altitude increases, performance economy deteriorates.

Some loss of thrust limited manoeuvre margin can be expected above OPTimum altitude. Levels 2000 ft above OPTimum altitude normally allows approximately 45° bank prior to buffet onset. The higher the airplane flies above optimum altitude, the more the thrust margin is reduced. Before accepting an altitude above optimum, determine that it will continue to be acceptable as the flight progresses under projected conditions of temperature and turbulence.

On airplanes with higher thrust engines, the altitude selection is most likely limited by manoeuvre margin to initial buffet and will generally provide a minimum of 33 to 44 degrees bank angle margin (1.2 to 1.4 g) to buffet or stick shaker. Projected temperature and turbulence conditions along the route of flight should be reviewed when requesting/accepting initial cruise altitude as well as subsequent step climbs.

Cruise Speed Determination

Relationship between Cost Index, MRC, AUW and Nautical Air Miles per tonne of fuel

Cruise speed is automatically computed by the FMC and displayed on the CRZ and PROGRESS pages. It is also displayed by the command air speed when VNAV is engaged. The default cruise speed mode is economy (ECON) cruise. The pilot can also select Long Range Cruise (LRC), engine out modes, or overwrite fixed Mach or CAS values on the CRZ page target speed line.

Economy Cruise (ECON)

ECON cruise is a variable speed schedule that is a function of gross weight, cruise altitude, cost index, and headwind component. It is calculated to provide minimum operating cost for the entered cost index. Entry of zero for cost index results in Maximum Range Cruise.

Headwinds increase the ECON CRZ speed. Tailwinds decrease ECON CRZ speed, but not below the zero wind Maximum Range Cruise airspeed.

Maximum Range Cruise (MRC)

This is the speed at which maximum fuel mileage (air range) is achieved. It is calculated by the FMC and displayed on the CRZ page in the ECON mode when a Cost Index of zero is entered. To achieve maximum range an aircraft must operate continuously at the OPTimum altitude. Generally, MRC is flown at a constant angle of attack with power reducing as AUW reduces. Headwinds increase the MRC speed, but tailwinds have no effect.

It is also practical to operate at MRC on short, low altitude segments where differences in cruise speed have almost no effect on total enroute time.

Variation of fuel and time with speed.

Long Range Cruise (LRC)

Older generation aircraft with basic autothrottle systems had problems operating at MRC at higher altitudes, due to the frequent power changes needed to maintain target speed. Because of this, the industry adopted a speed slightly faster than MRC (typically .01 to .02 Mach) called Long Range Cruise

LRC is a variable speed schedule providing fuel mileage 1% less than the maximum available (99% MRC). The FMC does not apply wind corrections to LRC.

Required Time of Arrival (RTA) speed is generated to meet a time required at an RTA specified waypoint on the FMC LEGS page.

Step Climb

Flight plans not constrained by short trip distance are typically based on conducting the cruise portion of the flight close to OPTimum altitude. Since the OPTimum altitude increases as fuel is consumed during the flight, it is necessary to climb to a higher cruise altitude periodically to achieve the flight plan fuel burn. This technique, referred to as Step Climb Cruise, is typically accomplished by entering an appropriate step climb value in the FMC according to the available cruise levels. For most flights, one or more step climbs may be required before reaching T/D.

It may be especially advantageous to request an initial cruise altitude above optimum if altitude changes are difficult to obtain on specific routes. This minimizes the possibility of being held at a low altitude/high fuel consumption condition for long periods of time. The requested/accepted initial cruise altitude should be compared to the thrust limited or the manoeuvre margin limited altitudes. Remember, a cruise thrust limited altitude is dependent upon the cruise level temperature. If the cruise level temperature increases above the chart value for gross weight, maximum cruise thrust will not maintain desired cruise speed.

Step altitudes can be planned at waypoints or they can be optimum step points calculated by the FMC. Optimum step points are a function of the route length, flight conditions, speed mode, present airplane altitude, STEP TO altitude (or adjacent STEP TO altitudes) and gross weight.

The FMC computed step point provides for minimum trip cost for the flight, including allowances for climb fuel. Initiate a cruise climb to the new altitude as close as practicable to the step climb point.

Note: FMC default values for the step climb may not be appropriate for RVSM or metric airspace. Manually enter the appropriate step climb values as needed - typically by overwriting ICAO with 2000.

Fuel for Enroute Climb

The additional fuel required for a 4,000 foot enroute climb varies from 550 to 1,300 lbs, 250 to 600 kg depending on the airplane gross weight, initial altitude, air temperature and climb speed. The fuel increment is largest for high gross weights and low initial altitudes. Additional fuel burn is offset by fuel savings in the descent. It is usually beneficial to climb to a higher altitude if recommended by the FMC or the flight plan, provided the wind information used is reliable.

Note: The fuel saved at higher altitude does not normally justify a step climb unless the cruise time at the higher altitude is at least 20 minutes.

Low Fuel Temperature

Fuel temperature changes relative to total air temperature. For example, extended operation at high cruise altitudes tends to reduce fuel temperature. In some cases the fuel temperature may approach the minimum fuel temperature limit.

Fuel freezing point should not be confused with fuel ice formation caused by frozen water particles. The fuel freezing point is the temperature at which the formation of wax crystals appears in the fuel. The Jet A fuel specification limits the freezing point to -40° maximum, while the Jet A-1 limit is -47°C maximum. In the Former Soviet Union, the fuel is TS-1 or RT, which has a maximum freezing point of -50°C which can be lower in some geographical regions. The actual uplifted freezing point for jet fuels varies by the geographical region in which the fuel is refined.

Unless the operator measures the actual freezing point of the loaded fuel at the dispatch station, the maximum specification freezing point must be used. At most airports, the measured fuel freezing point can yield a lower freezing point than the specification maximum freezing point. The actual delivered freezing temperature can be used if it is known. Pilots should keep in mind that some airports store fuel above ground and in extremely low temperature conditions the fuel may already be close to the minimum allowable temperature before being loaded.

For blends of fuels, use the most conservative freezing point of the fuel on board as the freezing point of the fuel mixture. This procedure should be used until 3 consecutive refuellings with the lower freezing point fuel have been completed. Then the lower freezing point may be used. If fuel freezing point is projected to be critical for the next flight segment, the wing tank fuel should be transferred to the center wing tank before refuelling. The freezing point of the fuel being loaded can then be used for that flight segment.

Fuel temperature should be maintained within AFM limitations as specified in the Limitations chapter of the FCOM.

The minimum fuel temperature is minus 45°C (minus 49°F) or 3°C (5°F) above the freeze point, whichever is higher.

Maintaining a minimum fuel temperature should not be a concern unless the fuel temperature approaches the minimum temperature limit. The rate of cooling of the fuel is approximately 3°C per hour, with a maximum of 12°C per hour possible under the most extreme conditions.

Total air temperature can be raised in the following three ways, used individually or in combination:

Note: In most situations warmer air can be reached by descending but there have been reports of warmer air at higher flight levels. Air temperature forecasts should be carefully evaluated when colder than normal temperatures are anticipated.

It takes from 15 minutes to an hour to stabilise the fuel temperature. In most cases, the required descent would be 3,000 ft to 5,000 ft below OPTimum altitude. In more severe cases a descent to altitudes of 25,000 ft to 30,000 ft might be required. An increase of 0.01 Mach results in an increase of 0.5° to 0.7°C total air temperature.

Cruise Performance Economy

The flight plan fuel burn from departure to destination is based on certain assumed conditions. These include takeoff gross weight, cruise altitude, route of flight, temperature, enroute winds, and cruise speed.

Actual fuel burn should be compared with the flight plan fuel burn throughout the flight.

The planned fuel burn can increase due to:

Cruise fuel penalties include:

For cruise within 2,000 ft of optimum, long range cruise speed can be approximated by M.80. Long range cruise also provides the best buffet margin at all cruise altitudes.

Note: If a discrepancy is discovered between actual fuel burn and flight plan fuel burn that cannot be explained by one of the items above, a fuel leak should be considered. Accomplish the applicable non-normal checklist.

Engine Inoperative Cruise/Drift-Down

Performance of a non-normal checklist or sudden engine failure may lead to the requirement to perform a single engine drift-down.

Engine inoperative cruise information is available from the FMC.

If an engine failure occurs while at cruise altitude, it may be necessary to descend. The autothrottle should be disconnected, thrust reference set to CON on the TMSP and the thrust manually set to MCT on the operative engine. On the FMC ACT CRZ page, select the ENG OUT key. This displays MOD CRZ calculated on engine out MCT and maintaining the airspeed displayed on the EO SPD line.

Set the engine out cruise altitude in the MCP altitude window and execute the ENG OUT CRZ D/D page. The thrust reference mode on the EICAS display will display CON. The airplane descends in VNAV using the VNAV SPD pitch mode. Once the descent rate has decreased to 300 fpm during drift-down it is held constant by the FMC until altitude capture.

At altitude capture the ENG OUT CRZ page is displayed. Maintain MCT on the operative engine and drift-down altitude until the E/O SPD speed is established. Maintain this speed using manual thrust adjustments.

After level off at the target altitude, maintain MCT and allow the airplane to accelerate to the single engine long range cruise speed. Maintain this speed with manual thrust adjustments. Entering the new cruise altitude and airspeed on the ECON CRZ page updates the ETAs and Top of Descent predictions. When the ENG OUT VNAV mode is selected and an engine-out condition is detected, the FMC computes engine-out trip predictions, guidance parameters, and MAX ALT consistent with the detected engine-out conditions, the selected thrust rating using the actual bleeds. Refer to Engine Out Familiarization, chapter 7, for trim techniques.

Note: If the airplane is at or below maximum ENG OUT altitude when an engine becomes inoperative, select and execute the ENG OUT CRZ page. Maintain engine out cruise speed using manual thrust adjustments.

If required to cruise at maximum altitude, set MCT, establish a climb and decelerate slowly to ENG OUT CRZ speed. At level off select ENG OUT LRC for best fuel economy.

An alternate target drift-down speed can be selected using the MOD CRZ or ENG OUT D/D page. LRC speed would result in a lower drift-down altitude but better fuel performance. A company specified speed could be selected and provides for a higher drift-down speed and a shorter flight time to the alternate.

An ENG OUT ALT can be entered on the MOD CRZ or ENG OUT D/D page. If an engine out cruise altitude lower than the computed maximum altitude is entered, the FMC commands a cruise descent at approximately 1250 fpm rather than a drift-down schedule.

Unless altered by the pilot, the level off cruise mode will be the same as was used during drift-down. FMC fuel and ETA calculations for drift-down and the remainder of the trip will be consistent with the selected speed mode. For best fuel performance select the engine-out LRC mode following a minimum drag speed (E/O) drift-down.

When VNAV is not used during engine out, set MCT on the operative engine and maintain altitude until the airplane decelerates to the displayed appropriate engine out speed. Use engine out speed from the FMC while descending to the engine out cruise altitude. Remain at MCT until the airplane accelerates to LRC, then maintain LRC speed with manual thrust adjustments. If the FMC is inoperative use turbulence penetration airspeed to drift-down and the engine out long-range cruise tables in the QRH.

High Altitude High Speed Flight

[section omitted]

ETOPs

[section omitted]

Polar Operations

[section omitted]

Descent


Descent Speed Determination

cost_index_descent_speed The default FMC descent speed schedule is an economy (ECON) descent from cruise altitude to the airport speed transition altitude followed by a descent at ten knots less than this speed. The speed schedule is adjusted to accommodate waypoint speed/altitude constraints displayed on the LEGS pages, and speed/altitude constraints displayed on the DES page. If desired, the ECON speed schedule can be modified by alternate Mach, Mach/IAS, or IAS values on the DES page target speed line. If the FMC information is not available, use target speeds from the Descent Rates table in this chapter.

Descent Path

Descent Speed Determination An FMC path descent is the most economical descent method. At least one waypoint-related altitude constraint below cruise altitude on a LEGS page generates a descent guidance path. The path is built from the lowest constraint upward, assuming idle thrust, or approach idle below the anti-ice altitude entered on the DESCENT FORECAST page.

The path is based on the descent speed schedule, any entered speed/altitude constraints or forecast use of anti-ice. The path reflects descent wind values entered on the DESCENT FORECAST page.

Descent Constraints

Descent constraints may be automatically entered in the route when selecting an arrival procedure, or manually entered through the CDU.

Set all mandatory altitude restrictions and at or above constraints in the Mode Control Panel (MCP) altitude window. The next altitude may be set when the restriction has been assured or further clearance has been received.

Shallow vertical path segments may result in the autothrottle supplying partial power to maintain the target speed. Vertical path segments steeper than an idle descent may require the use of speedbrakes for speed control. Deceleration requirements below cruise altitude (such as at 10,000 MSL) are accomplished based on a rate of descent of approximately 500 fpm. When a deceleration is required at top of descent, it is performed in level flight.

Speed Intervention

VNAV speed intervention can be used to respond to ATC speed change requirements. VNAV SPD pitch mode responds to speed intervention by changing airplane pitch while the thrust remains at idle. VNAV PTH pitch mode may require the use of speedbrakes or increased thrust to maintain the desired airspeed.

Offpath Descent (as installed)

The LEGS pages should reflect the planned arrival procedure. If a published arrival procedure is required for reference while being radar vectored, or the arrival is momentarily interrupted by a heading vector from ATC, the offpath descent circles provide a good planning tool to determine drag and thrust requirements for the descent.

The outer circle is referenced to the end of descent point, using a clean configuration and a direct path from the airplane position to the end of descent waypoint constraint. The inner circle is referenced to the end of descent point using speedbrakes. A separate waypoint may be entered on the OFFPATH DES page as a reference for the descent circles.

Both circles assume normal descent speed schedules, including deceleration at transition altitude, but do not include waypoint speed and altitude constraints.

Descent Planning

Flight deck workload typically increases as the airplane descends into the terminal area. Distractions must be minimized and administrative and nonessential duties completed before descent or postponed until after landing. Perform essential duties early in the descent so more time is available during the critical approach and landing phases.

Operational factors and/or terminal area procedures may not allow following the optimum descent schedule. Terminal area requirements can be incorporated into basic flight planning but ATC, weather, icing and other traffic may require adjustments to the planned descent schedule.

Proper descent planning is necessary to arrive at the desired altitude at the proper speed and configuration. The distance required for the descent is approximately 3.5 NM/1000 ft altitude loss for no wind conditions using ECON speed. Rate of descent is dependent upon thrust, drag, airspeed schedule and gross weight.

Descent Rates

Descent Rates tables provide typical rates of descent below 20,000 ft with idle thrust and speedbrakes extended or retracted.

Target Speed Rate of Descent (Typical)
Clean with Speedbrake
757-200 757-300 767-
200/300
757-200 757-300 767-
200/300
0.78M / 290 knots 1800 fpm 2000 fpm 1800 fpm 2700 fpm 3200 fpm 2700 fpm
250 kts 1500 fpm 1500 fpm 1500 fpm 2000 fpm 2400 fpm 2000 fpm
Vref 30 + 80 1200 fpm 1300 fpm 1200 fpm 1600 fpm 2000 fpm 1600 fpm

Normally, descend with idle thrust and in clean configuration (no speedbrakes). Maintain cruise altitude until the proper distance or time out for the planned descent and then hold the selected airspeed schedule during descent. Deviations from this schedule may result in arriving too high at destination and require circling to descend, or arriving too low and far out requiring extra time and fuel to reach destination.

The speedbrake may be used to correct the descent profile if arriving too high or too fast. The descent procedure is normally initiated before the airplane descends below the cruise altitude for arrival at destination, and should be completed by 10,000 ft MSL. The approach procedure is normally started at transition level.

Plan the descent to arrive at traffic pattern altitude at flaps up maneuvering speed approximately 12 miles from the runway when proceeding straight-in or about 8 miles out when making an abeam approach. A good crosscheck is to be at 10,000 ft AGL, 40 miles from the airport, at 250 knots.

Losing airspeed can be difficult and may require a level flight segment. For planning purposes, it requires approximately 45 seconds and 3 NM to decelerate from 290 to 250 knots in level flight without speedbrakes. It requires an additional 45 seconds and 3 NM to decelerate to flaps up maneuvering speed at average gross weights. Using speedbrakes to aid in deceleration reduces these times and distances by approximately 30%.

Maintaining the desired descent profile and using the map mode to maintain awareness of position ensures a more efficient operation. Maintain awareness of the destination weather and traffic conditions, and consider the requirements of a potential diversion. Review the airport approach charts and discuss the plan for the approach, landing, and taxi routing to parking. Complete the approach briefing as soon as practical, preferably before arriving at top of descent. This allows full attention to be given to airplane control.

Speedbrakes

The PF should keep a hand on the speedbrake lever when the speedbrakes are used in-flight. This helps prevent leaving the speedbrakes extended when no longer required.

Use of speedbrakes does not appreciably affect airplane roll response. While using the speedbrakes in descent, allow sufficient altitude and airspeed margin to level off smoothly. Lower the speedbrakes before adding thrust.

To avoid buffeting, use of speedbrakes with flaps greater than 5 should be avoided. If circumstances dictate the use of speedbrakes with flaps extended, high sink rates during the approach should be avoided. Speedbrakes should be retracted before reaching 1,000 ft AGL.

Note: With speedbrakes fully extended, flaps up manoeuvre margin to stick shaker is reduced. Additional airspeed (up to 5 knots) may be added to flaps up maneuvering speed to ensure full manoeuvre margin (40° bank capability).

The flaps are normally not used for increasing the descent rate. Normal descents are made in the clean configuration to pattern or instrument approach altitude. When descending with the autopilot engaged and the speedbrakes extended at speeds near Vmo/Mmo, the airspeed may momentarily increase to above Vmo/Mmo if the speedbrakes are retracted quickly. To avoid this condition, smoothly and slowly retract the speedbrakes to allow the autopilot sufficient time to adjust the pitch attitude to maintain the airspeed within limits.

When the speedbrakes are retracted during altitude capture near Vmo/Mmo, a momentary overspeed condition may occur. This is because the autopilot captures the selected altitude smoothly by maintaining a fixed path while the thrust is at or near idle. To avoid this condition, it may be necessary to reduce the selected speed and or descent rate prior to altitude capture or reduce the selected speed and delay speedbrake retraction until after level off is complete.

Flaps and Landing Gear

Normal descents are made in the clean configuration to pattern or instrument approach altitude. If greater descent rates are desired, extend the speedbrakes. When thrust requirements for anti-icing result in less than normal descent rates with speedbrakes extended, or if higher than normal descent rates are required by ATC clearance, the landing gear can be lowered to increase the rate of descent. Extend the flaps when in the terminal area and conditions require a reduction in airspeed below flaps up maneuvering speed. Normally select flaps 5 prior to the approach fix going outbound, or just before entering downwind on a visual approach.

Note: Avoid using the landing gear for increased drag. This minimizes passenger discomfort and increases gear door life.

Speed Restrictions

Speed restrictions below specific altitudes/flight levels and in the vicinity of airports are common. At high gross weights, minimum maneuvering speed may exceed these limits. Consider extending the flaps to attain a lower maneuvering speed or obtain clearance for a higher airspeed from ATC.

Other speeds may be assigned by ATC. Pilots complying with speed adjustments are expected to maintain the speed within plus or minus 10 knots.

Engine Icing During Descent

The use of anti-ice and the increased thrust required increases the descent distance. Therefore, proper descent planning is necessary to arrive at the initial approach fix at the correct altitude, speed, and configuration. The anticipated anti-ice use altitude should be entered on the DESCENT FORECAST page to assist the FMC in computing a more accurate descent profile.

Engine icing may form when not expected and may occur when there is no evidence of icing on the windshield or other parts of the airplane. Once ice starts to form, accumulation can build very rapidly. Although one bank of clouds may not cause icing, another bank, which is similar, may induce icing.

Note: The engine anti-icing system should be turned ON or AUTO (as installed) whenever icing conditions exist or are anticipated. Failure to follow the recommended anti-ice procedures can result in engine stall, over temperature or engine damage.

Holding

Start reducing to holding airspeed 3 minutes before arrival time at the holding fix so that the airplane crosses the fix, initially, at or below the maximum holding airspeed.

If the FMC holding speed is greater than the ICAO or FAA maximum holding speed, holding may be conducted at flaps 1, using flaps 1 maneuvering speed. Flaps 1 uses approximately 10% more fuel than flaps up. Holding speeds in the FMC provide an optimum holding speed based upon fuel burn and speed capability; but are never lower than flaps up maneuvering speed.

If [the] holding speed is not available from the FMC, refer to the PI section of the QRH. Recommended holding speeds can be approximated by using the following guidance until more accurate speeds are obtained from the QRH:

Procedure Holding

When a procedure holding pattern is selected from the navigation data base and the FMC shows PROC HOLD on the LEGS page, the following is true when the PROC HOLD is the active leg:

ICAO Holding Airspeeds (Maximum)

Altitude Speed
Through 14,000 ft 230 knots
Above 14,000 ft to 20,000 ft MSL 240 knots
Above 20,000 ft to 34,000 ft MSL 265 knots
Above 34,000 ft MSL 0.83M

FAA Holding Airspeeds (Maximum)

Altitude Speed
Through 6,000 ft MSL 200 knots
6,001 ft MSL through 14,000 ft MSL 230 knots
(210 knots Washington DC and New York FIRs)
14,001 ft MSL and above 265 knots

Maintain clean configuration if holding in icing conditions or in turbulence. If the holding pattern has not been programmed in the FMC, the initial outbound leg should be flown for 1 minute or 1½ minutes as required by altitude. Timing for subsequent outbound legs should be adjusted as necessary to achieve proper inbound leg timing.

In extreme wind conditions or at high holding speeds, the defined holding pattern protected airspace may be exceeded. However, the holding pattern depicted on the map display will not exceed the limits. Advise ATC if an increase in airspeed is necessary due to turbulence, if unable to accomplish any part of the holding procedure, or if unable to comply with speeds listed in the tables above.

Note: Above FL250, use Vref 30 + 100 knots to provide adequate buffet margin.

Fuel