BOEING 787-9 AUTOSTART
Both engines are normally started at the same time, unless the outside air temperature is below 41°F (5°C).
FROM THE PRELIMINARY REPORT
As per the EAFR data both engines N2 values passed below minimum idle speed, and the RAT hydraulic pump began supplying hydraulic power at about 08:08:47 UTC.
RAT in extended position
As per the EAFR, the Engine 1 fuel cutoff switch transitioned from CUTOFF to RUN at about 08:08:52 UTC. The APU Inlet Door began opening at about 08:08:54 UTC, consistent with the APU Auto Start logic. Thereafter at 08:08:56 UTC the Engine 2 fuel cutoff switch also transitions from CUTOFF to RUN. When fuel control switches are moved from CUTOFF to RUN while the aircraft is inflight, each engines full authority dual engine control (FADEC) automatically manages a relight and thrust recovery sequence of ignition and fuel introduction.
The EGT was observed to be rising for both engines indicating relight. Engine 1’s core deceleration stopped, reversed and started to progress to recovery. Engine 2 was able to relight but could not arrest core speed deceleration and re-introduced fuel repeatedly to increase core speed acceleration and recovery. The EAFR recording stopped at 08:09:11 UTC
At about 08:09:05 UTC, one of the pilots transmitted “MAYDAY MAYDAY MAYDAY”. The ATCO enquired about the call sign. ATCO did not get any response but observed the aircraft crashing outside the airport boundary and activated the emergency response.
To move any FUEL flow control switch from RUN position to CUT-OFF position requires PULLING the switch BACKWARD to pass it over the safety detent and, put it down on CUT-OFF position. It is very hard accidentally the switch moves to CUT OFF position.
Operation illustration for LAYMEN better understanding
Considering the MAYDAY call a consequence of a very stressful situation on flightdeck.
So, the first thing the pilots
had to pay attention it was the engine parameters out of standard and
secondarily, a pilot had acknowledged an abnormal engine.
Following that, the other pilot
has perceived an engine having been shut down by his colleague, who denied to
have shut down the engine.
We, out of the cockpit, must
accept the condition for shutting down an engine. The pilot needs to pull the
FUEL switch up (back) to overtake the safety detent and, bring it to OFF
position, so the FUEL flow will be cut to the engine.
The FUEL switch has no condition
to jump for itself over the safety detent.
Now we have two possibilities:
1. A pilot mistakenly moved manually the FUEL switch to OFF position. But he denied it.
2. The FUEL switch had lost electric power to keep the fuel flow function (at the RUN position) feeding the engine.
NOTE: There is a COMMON MOTOR STARTER CONTROLLER
The Common Motor Starter Controller or CMSC, supplies variable frequency and variable AC voltage to airplane systems that need a high voltage to operate such as the Cabin Air Compressor and the Electric Motor Pump. Because the CMSC's can get very hot, they are cooled via the Power Electronic Cooling System (PECS).
Click on the image to see isolated
FROM THE PRELIMINARY REPORT
In-Flight Start
In-flight
start envelope information
is displayed on the EICAS display when an engine is
not running in flight (N2
RPM below idle RPM) or when an engine is
shut down in flight and the respective
engine fire switch is not pulled.
The in-flight start envelope indicates the airspeed range necessary to ensure
an in-flight start at the current flight level. If the current flight level is
above the maximum start altitude, the maximum start altitude and respective
airspeed range are displayed.
Secondary
engine indications are automatically displayed in flight when an engine is not running (N2 RPM is below idle with
corresponding FUEL CONTROL switch in RUN)
or when a FUEL CONTROL switch is moved to CUTOFF.
A starter assist indication (X-START) is displayed below the N2 indication if
airspeed is below that recommended for a windmilling start. For in- flight
starts, autostart makes continuous start attempts until the engine either
starts or the pilot aborts the start attempt by positioning the FUEL CONTROL
switch to CUTOFF (and positioning the START switch to NORM if it was a starter
assisted attempt).
During the windmilling in-flight start, the EEC monitors engine parameters to provide the best fuel schedule to ensure the shortest possible start time. (Refer to Engine In-Flight Start, QRH, Non-Normal Checklists Chapter 7, for the in-flight engine start procedure.)
NOTE: There is a COMMON MOTOR STARTER CONTROLLER
The Common Motor Starter Controller or CMSC, supplies variable frequency and variable AC voltage to airplane systems that need a high voltage to operate such as the Cabin Air Compressor and the Electric Motor Pump. Because the CMSC's can get very hot, they are cooled via the Power Electronic Cooling System (PECS).
Engine start (Dynamic)
Once all doors and hatches are closed, external cables and pipes have been removed and the APU is running, we're ready to push back from the gate and start our engines.
Both engines are normally started at the same time, unless the outside air temperature is below 41°F (5°C).
On other aircraft types, the engines require high pressure air from the APU to turn the starter in the engine. This requires a lot of power from the APU and is also quite noisy. On the 787, the engine start is entirely electrical.
Power is drawn from the APU and feeds the VFSGs in the engines. If you remember from earlier, these fist act as starter motors. The starter motor starts the turn the turbines in the middle of the engine. These in turn start to turn the forward stages of the engine. Once there is enough airflow through the engine, and the fuel is igniting, there is enough energy to continue running itself.
The electrical system during an engine start. L1 and L2 are in generator mode whilst R1 and R2 are acting as starters. The APU is still providing power to the aircraft systems.
After start
Once the engine is running, the VFSGs stop acting as starter motors and revert to acting as generators. As these generators are the preferred power source, they automatically take over the running of the electrical systems from the APU, which can then be switched off. The aircraft is now in the desired configuration for flight, with the 4 VFSGs in both engines providing all the power the aircraft needs.
As the aircraft moves away toward the runway, another electrically powered system is used — the brakes. On other aircraft types, the brakes are powered by the hydraulics system. This requires extra pipe work and the associated weight that goes with that. Hydraulically powered brake units can also be time consuming to replace.
By having electric brakes, the 787 is able to reduce the weight of the hydraulics system and it also makes it easier to change brake units. "Plug in and play" brakes are far quicker to change, keeping maintenance costs down and reducing flight delays.
In-flight
Another system which is powered electrically on the 787 is the anti-ice system. As aircraft fly though clouds in cold temperatures, ice can build up along the leading edge of the wing. As this reduces the efficiency of the wing, we need to get rid of this.
How pilots keep you safe while flying through strong winds
Other aircraft types use hot air from the engines to melt it. On the 787, we have electrically powered pads along the leading edge which heat up to melt the ice.
Not only does this keep more power in the engines, but it also reduces the drag created as the hot air leaves the structure of the wing. A double win for fuel savings.
Engine generators
Two Starter/Generators 235 Vac (L1-L2-R1-R2)
- Each engine, two starter/Generators are directly connected to the Engine gear box, producing variable frequency power proportional to the Engine rotor speed.
- Both engine starters are used for engine start, but nevertheless the engine may be started with only one generator. The start will be slower than the normal start.
- Power for engine start may be provided by the APU, opposite engine generators or external power.
- Both generators on each side will provide a variable frequency of 235 Vac to the AFT E/E bay, were power is distributed. Four main buses (L1-L2-R1-R2) each powered by its respective generator line. Automatic protection ensures that only one source is applied to the main bus at a time.
- Each generator has a drive disconnect mechanism that allows the generator to be mechanically disconnected from the engine. Depending on the fault condition, can be disconnected manually or automatically. (DRIVE DISC), once disconnected cannot be reconnected.
ABOUT THE LANDING GEAR NOT RETRACTED
The Preliminary Report brought the answer, the landing gear lever was not moved to the UP position after lift off.
The flap handle assembly (fig.11) sustained significant thermal damage. The handle was found to be firmly seated in the 5-degree flap position, consistent with a normal takeoff flap setting. The position was also confirmed from the EAFR data. The landing gear lever was in “DOWN” position. (fig.12)
The thrust lever quadrant sustained significant thermal damage. Both thrust levers were found near the aft (idle) position. However, the EAFR data revealed that the thrust levers remained forward (takeoff thrust) until the impact. Both fuel control switch were found in the “RUN” position. (fig.13) The reverser levers were bent but were in the “stowed” position. The wiring from the TO/GA switches and autothrottle disconnect switches were visible, but heavily damaged.
Click on the image to magnify it (isolated)
In-Air Rat only Mode (Standby Power)
Is active with the loss of all electrical power to the Captain’s & First officers flight instruments, in that case the RAT will energize the captains flight instruments with some essential equipment including flight controls, navigation and communications.
Energized equipment by the RAT are as follows.
Captains inboard & outboard DU’s, lower DU,MCP, PFC, ECL, FMC limited operation, Autopilot limited operation, Autoflight system, Captain’s & First officer’s ACP’s and the flight interphone, LEFT( VHF/TCP/DSP/MFK/CCD/CCR), LEFT & RIGHT (IRU/AHRU/INR), Centre pitot heat, Engine/APU fire detection and miscellaneous lighting.
INOP systems include TAT, Autothrottle, LNAV/VNAV, FMC predictions and thrust limits, TAP, Flaps & Slats, Stabilizer trim, Packs, HUD’s, HF, SATCOM, TCAS, GPWS, Transponder, WX radar, External lighting, Wipes, and Window heat.
