Engine bleeds 737 что это
When are the engine bleed air, APU and packs turned on in the B737?
When do I have to turn on the engine bleed air and APU? In videos I have seen that they are always on, and sometimes they turn them off after take-off. I also have the same question about the packs.
2 Answers 2
The general answer is, the engine bleeds stay on almost all the time.
The times they’re turned off:
That scenario plays out if you’re using the APU to run the cabin air conditioning (typically, on a hot day with lots of passengers), since it puts out a greater volume of bleed air than the engines do when they’re operating at or near idle (i.e. typical taxi power settings). In that case, you close the engine bleeds, open the APU bleed and the isolation valve, and let the APU run both packs.
That scenario also plays out when starting an engine while taxiing; the switchology is reasonably intuitive but a little lengthy to describe.
There is no need when starting the engines initially to close the engine bleeds, since the normal procedure is to close the APU bleed & turn it off before taxiing the aircraft.
For a bleeds-off takeoff, the configuration is, engine bleeds off, APU bleed on, packs on, isolation valve closed. After takeoff, the steps are, #2 bleed on, pause, APU bleed off, pause, #1 bleed on, then isolation valve to Auto.
There is a procedure for a bleeds-off landing (to get more engine power for a go-around), and there are some QRH instances when you might turn a bleed switch off, but all of that is fairly rare.
If the OP is using a flight sim, the simple general answer, always leave the engine bleed switches on, will work fine. Turn off the APU bleed after start. If you get the Master Caution for «Dual Bleed», you forgot to turn off the APU bleed, do so.
Edit, pack switches: off for engine start, on otherwise (except as directed by the QRH).
737. Панель контроля отбора воздуха и кондиционеров
Обратите внимание на линии, нарисованные на панели: они показывают, как распределяется воздух от двигателей и APU по всей пневматической системе.
RECIRC FAN (1) (Recirculation fan) – тумблеры вентиляторов рециркуляции воздуха. Нормальное положение – AUTO.
В пассажирском салоне «обновляется» не весь воздух. Часть воздуха снова возвращается в салон – рециркулируется, тем самым снижая нагрузку на систему кондиционирования. Но пилоты в кабине всегда дышат свежим воздухом.
Индикатор давления в левом (L) и правом (R) каналах (2). На индикаторе – две стрелки с литерами L и R.
Тумблеры подачи воздуха в паки (3) левый (L PACK) и правый (R PACK).
Тумблеры отбора воздуха от двигателей (4). Для отбора двигатели должны быть запущены.
Тумблер отбора воздуха от ВСУ (APU) (5). Для отбора ВСУ должно быть запущено.
ISOLATION VALVE (6) – изолирующий клапан, которым замыкают каналы. CLOSE – закрыто. OPEN – открыто. AUTO закрывает клапан, когда воздух отбирается от двигателей, а паки включены в положение AUTO или HIGH. AUTO открывает клапан, если закрыт один из паков или нет отбора воздуха от одного из двигателей.
TRIP RESET (7) – кнопка гасит светосигнальные табло на этой панели. Только гасит табло! Проблема не решена!
На самом верху. Табло DUAL BLEED (8) – двойной отбор, то есть воздух одновременно отбирается и от ВСУ, и от двигателей. Он недопустим, поэтому, если табло горит, определитесь с выбором – откуда вы будете забирать воздух – от ВСУ или двигателей.
Табло RAM DOOR FULL OPEN (9) – створка прямоточной впускной системы открыта полностью. Это – воздухозаборник для охлаждения воздуха, отобранного от двигателей.
В центре панели. Табло PACK (10) – пак вышел из строя.
Табло WING-BODY OVERHEAT (11) – перегрев элементов крыла и фюзеляжа из-за утечки горячего воздуха в одном из каналов. На различных элементах корпуса и крыльев рядом с каналами стоят датчики, которые фиксируют повышение температуры и подают сигнал.
Табло BLEED TRIP OFF (12) – слишком высокая температура или давление воздуха, забираемого от двигателя. Автоматически прекращается отбор от этого двигателя и закрывается клапан.
engine bleed air
1 engine bleed air
2 engine bleed air
3 engine-bleed air
4 engine bleed air
5 engine bleed air
6 engine bleed air
7 engine bleed air
8 engine-bleed air
См. также в других словарях:
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Engine bleeds 737 что это
Руководство по летной эксплуатации Боинг-737-800.
FCOM B-737-800 (Flight Crew Operations Manual B-737-800).
Содержание: 
Volume 1.
Title Page.
Preface.
Model Identification.
Introduction.
Abbreviations.
Revision Record.
V1V2 List of Effective Pages.
Bulletin Record.
Limitations.
Normal Procedures.
Supplementary Procedures.
Performance Dispatch.
Performance Inflight.
Volume 2.
Airplane General, Emergency Equipment, Doors, Windows.
Air Systems.
Anti-Ice, Rain.
Automatic Flight.
Communications.
Electrica.
Engines, APU.
Fire Protection.
Flight Controls.
Flight Instruments, Displays.
Flight Management, Navigation.
Fuel.
Hydraulics.
Landing Gear.
Warning Systems.
Revision Date: September 25, 2014.
Document Number: D6-27370-800-AR.
The Boeing Company, Seattle, USA, 1628 с.,
AUXILIARY POWER UNIT
Contents
Page Contents
All of the information, photographs & schematics from this website and much more is now available in a 374 page printed book or in electronic format.
*** Updated 14 Nov 2021 ***
Other APUs available for the Classic were the Garrett GTCP 36-280(B) and the Sundstrand APS 2000; NGs have the Allied Signal GTCP 131-9B. The main difference between them is that the Garrett is hydro-mechanical whereas Sundstrand and Allied Signal are FADEC controlled. I am told by engineers that whilst the Garrett is more robust, the Sundstrand and Allied Signal APUs are easier to work on. On the 3/4/500s, we pilots prefer the Sundstrand because it has no EGT limits and faster restart wait times. The easiest way to tell which is fitted is to look at the EGT gauge limits; the GTCP 85-129 has an 850C limit and also runs at 415Hz, the GTCP 36-280 has an 1100C limit if no EGT limits are marked you have a Sundstrand. Later aircraft have MAINT instead of LOW OIL QUANTITY and FAULT instead of HIGH OIL TEMP warning lights.
The AlliedSignal APU has a 41,000ft start capability and incorporates a starter/generator, thus eliminating a DC starter and clutch. In practice this means that it can be started either by battery or AC transfer bus 1 (the classics are battery start only). It has an educter oil cooling system (see Bottom of page advert) and therefore has no need for a cooling fan. It is rated at 90KVA up to 31,000ft and 66KVA up to 41,000ft. The Garrett and Sundstrand APUs are only rated to 55KVA.
The fuel source is normally from the No 1 main tank and it is recommended that at least one pump in the supplying tank be on during the start sequence (and whenever operating) to provide positive fuel pressure and preserve the service life of the APU fuel control unit. Boeing responded to this need by installing an extra DC operated APU fuel boost pump in the No 1 tank on newer series 500 aircraft which automatically operates during APU start and shuts off when it reaches governed speed. You can quickly tell if this is installed by looking for the APU BAT position on the metering panel and the APU BAT OVHT light on the aft overhead panel.
It is recommended that the APU be operated for one full minute with no pneumatic load prior to shutdown. This cooling period is to extend the life of the turbine wheel of the APU.
Garrett 85-129 APU panel
EGT limits marked and oil temp & pressure captions.
No EGT limits and MAINT & FAULT captions.
Components
Sundstrand APS 2000
APU Timer
APU TimerSome aircraft have APU timers fitted on the aft overhead panel, since APU running time cannot be measured by aircraft logbook time.
Fire Protection
There is only one APU fire bottle, despite the fact that the handle can be turned in either direction! It is filled with Freon (the extinguishant) and Nitrogen (the propellant) at about 800psi. When the fire handle is turned, the squib is fired which breaks the diaphragm on the bottle, the pressure of the nitrogen then forces the freon into the APU compartment which suffocates the fire. Note that after a squib has been fired, the yellow disc on the fuselage may not blow completely clear, see photos below.
The APU fire extinguisher bottle indicators comprise of one yellow disc to show if the squib has been fired and one red disc to show if the bottle has over temperatured (130C) or over pressured (1800psi). Some aircraft are fitted with the sight glass to the bottle pressure gauge.
Note: Sight glass and bottle indicators are not fitted to NG’s.
This photo shows the condition of the discs after the APU fire bottle had been discharged. Notice how the yellow disc is displaced slightly but has not been blown away, this could easily be missed on an external inspection. Since the bottle only contains nitrogen and freon, there was no other external evidence of the bottle having been used since the evidence had evaporated away.
General
The APU will auto-shutdown for the following reasons:
The OVERSPEED light may illuminate for any of the following reasons:
There is no CSD in the APU because it is a constant speed engine.
If the APU appears to have started but no APU GEN OFF BUS light is observed then you may have a hung start.
LOW OIL QTY/MAINT – When illuminated, you may continue to operate the APU for up to 30 hrs. Note: this light is only armed when APU switch is ON.
FAULT – Although the malfunction will cause the APU to auto-shutdown, additional restarts may be attempted.
Max recommended start altitude – 25,000ft Classics; No limit NG’s.
Each start attempt uses approx 7mins of battery life.
Classic: Switching the battery off will shutdown the APU on the ground only.
NG: Switching the battery off will shutdown the APU in the air or on the ground.
 |
The APU is enclosed within a fireproof, sound reducing shroud which must be removed before access can be gained to its components.
There are two drain masts. The one just aft of the port wheel-well is shared with the hydraulic reservoir vent and is a shrouded line enclosing the APU fuel supply line, this collects any leakage of fuel into the shroud which can be drained when a stop cork is pushed up in the wheel-well. If fuel drains when the stop cork is pushed, it indicates a leak in the APU fuel line.
The drain mast on the APU Cowling (see photo left) mates with the APU shroud and drains oil from the forward accessory and the compressor bearing.
The opening at the top of the photo is the cooling air vent.
The APU shroud (center), fuel supply line (left), bleed air duct (right) and cooling air vent (outlined in red). Note this metal shroud is replaced by thermal fire protection blanket on the NG.
The APU cowling showing the lines to the discharge discs and the cooling air overboard exhaust. The small access panel above the cowling is the line of sight oil filler, this is sometime located ventrally in front of the cowling for easy access from the ground.
NG Eductor cooling system
The 737 NG APU is recognisable by the “eductor” cooling air inlet above the exhaust. This and a redesigned silencer make the NG APU 12dB quieter than the Classics.
The eductor works by using the high speed flow of the APU exhaust which forms a low pressure area. The low pressure pulls outside air through the eductor inlet duct to the APU compartment. The cooling air then goes through the oil cooler and out the APU exhaust duct below, eliminating the need for a separate cooling air vent or fan.
The protrusion on the lower right hand side of the photo is the vortex generator on the APU air inlet door.
Limitations & Operating Techniques:
APU life can be shortened by incorrect operating techniques. This can be helped by allowing the correct warm-up & cool-down times and bleed configuration for each type of APU. They all differ slightly due to engine core and design differences, but the manifestation of the failure is usually a turbine wheel rotor and/or blade separation. The following table is based on manufacturers recommendations.