Извиняюсь за новые вопросы по Б777. Хотелось бы узнать у специалистов - используется ли режим V/S (для экономии топлива или еще по какой либо причине). Нашел в Инете такой документ:
http://www.redskyventures.org/doc/g...ractices-And-Techniques-1.9.HL_ExVirginOz.pdf
Вкратце выписал то, что интересует. Очень сложно перевести технически грамотно - машинный перевод совершенно не подходит. Можно в двух словах, у кого хорошо с английским.
3.10. VS : (Not So) Very Special Mode
There is a perception that VS (and by association, FPA) is somehow an AFDS mode with
inherent flight safety implications and should only be used as a last resort. Generally
speaking this attitude stems from a poor understanding of the AFDS VS/FPA mode. While
FLCH is usually superior in most situations to VS, there are a number of situations where VS
is highly appropriate.
It is true that VS has some issues related to airspeed. These issues are inherent in the design
of the mode – unlike FLCH and VNAV SPD, the primary controlling parameter is not IAS. As
such, IAS is sacrificed where necessary to maintain the primary controlling influence of
Vertical Speed. Therefore VS/FPA can be inappropriate at high altitude (and/or high weight)
when thrust is insufficient and airspeed may reduce towards minimum manoeuvring
margin. Very high VS selections in either climb or descent can result in inappropriate speed excursions.
One specific issue is the use of VS or FPA at high altitude. Engaging VS/FPA from VNAV opens the speed window to the
currentIAS indication. VS/FPA level changes with IAS as the parameter commanding elevator at high altitude is
inherently risky – the MCP airspeed selector should be changed to MACH.
VS/FPA however is the mode of choice for:
• Reducing rate of climb or descent when approaching an altitude/level and other aircraft are in the vicinity.
• Non Precision Approaches when VNAV is not available.
• Continuous Descent Arrivals.
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12.4. Use of VS to change Level at Higher Altitudes
See 12.5 Block Clearances. The use of VS/FPA (and even FLCH) constitutes a higher workload on the flight deck and comes with issues related to the use of IAS as a controlling auto flight parameter at high altitude. VNAV is generally the preferred solution.
12.5. Block Clearances
ATC Block clearances allow the aircraft to operate at any altitude within the cleared block limits. Climb or Descent within the block is at the behest of the crew. While traditionally used to maintain the most optimum cruise level to reduce fuel usage, block clearances have also been useful to find altitude between traditional RVSM levels that provide a smoother ride.
One crucial aspect of a block clearance during augmented operations is the clear
communication of the clearance to the next crew during handover.
VNAV to Change Level
For altitude changes of 100 ft in the block level, VNAV provides the lowest workload solution through a simple twist and
press of the altitude selector. The FMA does not change and the FMC Cruise Altitude is updated automatically. Thrust
increases to maintain the FMC commanded MACH while the elevators pitch up to climb the 100 ft to the next level.
Thrust and pitch change are minimal resulting in smooth ride for the passengers. Altitude changes of 200 ft or more
however will result in the usual two rounds of FMA changes and the application of more thrust and pitch.
AFDS Basic Modes to Change Level
For level changes in excess of 100 ft in the block, some crew prefer VS +100 fpm (or FPA +0.1°). This is a higher
workload/higher risk solution and it should be noted that any time a basic AFDS pitch mode is used at higher altitude,
the AFDS Thrust Mode will default to Indicated Airspeed (IAS) – this should be changed to Mach. IAS as a commanded
auto-throttle parameter during level changes at high altitude can expose the aircraft to high and low speed limit
excursions. Note also that the FMC Cruise Altitude will need to be updated during the level change – this can be done
anytime by pressing the altitude selector. When the level change is complete – even if another level change is expected
shortly thereafter – the AFDS should be returned to VNAV PATH.
In essence, use of VS/FPA (and to a lesser extent FLCH) at higher altitudes to change levels is considered a high
workload solution to a problem that VNAV was designed to address with greater ease
