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Qavion2

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Posts posted by Qavion2

  2. Posted

    On our earlier aircraft, there used to be fuel system logic to prevent refuelling if the stabiliser was not in the 5~7 unit range. A light illuminated on the fuelling panel to advise that HST fuelling was inhibited.

    Now there is no light or logic, so I guess Boeing deemed it unnecessary. There are 10 level sensors in the tail tank, so I guess they can figure out what the level is, irrespective of angle.

  3. Posted

     

    24 minutes ago, calzonister said:

    Autostart: Offered as a customer option from day one. First aircraft delivered to Lufthansa, D-ABVB. L/N 700. The first 747-400 L/N 696 was delivered to Northwest, however NW did not option Autostart. 

    It was engine dependent. Northwest had PW engines. I don't think PW engines had an autostart option until a few years later. PW simply didn't have the technology on their engines.

     

    I stand corrected on the message logic (I amended my earlier message), but there were wiring modifications carried out to pump power relays somewhere after 2009 (I don't know if PMDG models these).
     

  4. Posted

    As far as I know, weight and balance systems are mostly fitted to freighters (or combis). Freighters don't have stabiliser tanks.

    Single or dual appears to be simply a customer option (and how deep the customer airline's pockets are).

    Ballast fuel is related to the CWT. When freighters/combis are empty, fuel is carried in the CWT to help shift the Centre of Gravity forward.

  5. Posted · Edited by Qavion2

    2 hours ago, kevinh said:

    Autostart has always been available AFAIK. 

    The first 744's came out with PW engines which initially didn't have autostart. I recall that even our first RB211-powered aircraft didn't have autostart, but were later retrofitted.I guess within a few years of 747-400 production.

     

    2 hours ago, kevinh said:

    I have no idea when the updated fuel system was introduced. I don’t think it was before 2004. 

    It depends on what aspect of the new fuel system in PMDG. Hydromechanical scavenge pumps? New message logic? Automatic pump shutoff with pump low fuel pressure? The last one was somewhere between 2009 and 2011 (I have wiring diagrams dated 2009 without the updated logic and diagrams with the updated logic dated 2011). Hydromechanical scavenge pumps have been around much longer.

    Quote

    Aux Hyd 1

    At least since August 1989. Qantas' first -400 had the #1 Aux pump.

     

     

    • Upvote 1

  6. Posted

    On 12/27/2018 at 9:21 AM, berts said:

    Pushing the FIRE/OVHT TEST ENG switch actually introduces a fire/overheat signal into the Engine Turbine overheat detectors.  

    Technically speaking, the test induces an artificial fire signal in the AFOLTS* cards, not the overheat detectors themselves.

    *Automatic Fire/Overheat Logic Test System

    The turbine overheat detectors are only found on the RB211. These are overheat "switches", which talk directly to the AFOLTS (computer) cards.

    The normal (cowl) fire detectors (or "loops" as they are known) are found on all engine types. The loops feed into specialised detector cards. These determine if the signals from the loops are faults or fires. The detector cards then talk to the AFOLTS cards.

    The AFOLTS cards process test pushbutton and fire/fault signals and then send signals to the rest of the aircraft to produce lights, bells and messages.

    There are very few indicator lights on the flight deck which are not illuminated by the Master Dim and Test System. The engine/APU fire and squib tests lights are some of these (including the fire handles). Other lights that come to mind are the big orange EVAC light on the pedestal and the Stab Greenband forward/aft lights.

    On some Boeing aircraft, some light tests may be affected by the configuration of aircraft switches.

     

     

  8. Posted

    On 12/24/2018 at 9:05 AM, Qavion2 said:

    During Standby Power operation, the Ground Handling Bus is unpowered.

    Sorry.. I used the expression Ground Handling Bus instead of Ground Service Bus at one point in my response. But, yes, the brake indicator runs off the GSB.

     

    On 12/27/2018 at 11:12 AM, berts said:

    However, you previously stated the Ground Service Bus powers the brake pressure gauge, so provided the Battery switch is ON and the Standby Power Selector is in AUTO, then the Ground Service Bus should normally be powered automatically in flight and on the ground whenever AC Bus 1 is powered. 

    I recall that PMDG's 744 automatically powers the GSB when the aircraft is powered using the GHB (even though manual intervention is required at door Left 2 on the real aircraft)  I doubt this was a factor in the video, however.

  9. Posted

    Bare weight of the RB211-524G/H, according to my manuals is 9,681lbs (4391Kg). I seem to remember earlier discussions on this as to whether this included the reverser assembly. I think reversers are included in the bare weight of a RB211, but not on a GE.

    So where does the (huge) extra 5th pod "weight" come from? I guess the mounting strut weight is included, the fairing panel weight, etc. The fan blades are removed, so that should reduce the weight significantly. I guess the weight penalty is based on aerodynamic drag at critical phases.

  10. Posted · Edited by Qavion2

    For takeoff and landing performance determination, the spare engine certified weight of 6,786Kg is used. For loading calculations (possibly airline specific), the spare engine weights and indexes applied in the Flight Management (FM) load planning system are:

     

    RB211-524D4 6,537kg

    RB211-524G/H series 6,610Kg

    RB211-524G-T/H-T series 6,524Kg

     

     

  12. Posted

    Engineering should check to see how long the engine was at specific temperatures/speeds, to see what maintenance checks will be required (not always an engine change, but may simply be an inspection). After maintenance has been completed, the "exceedance" has to be erased from the non-volatile memories in the instrument display computers using the CDU Central Maintenance Computer ("Chapter 71") pages on the real aircraft.

    • Upvote 1

  13. Posted · Edited by Qavion2

    On 12/17/2018 at 8:20 AM, berts said:

    Should the heading cursor be in view on the ND? The MCP is dead, so no computed data.

    Source loss or invalid data to the HDG display should show up as dashes.  However, heading information to the NAV display is supplied by the selected IRU.

    Actually, I was talking about the selected heading cursor here.

     

    On 12/17/2018 at 8:20 AM, berts said:

    Shouldn't the Brake Pressure Gauge be showing fully zero (power normally comes from the Ground Service Bus)?

    This instrument shows the brake accumulator pressure, so provided some brake pressure is still present it shouldn't read zero. 

    The pressure sensor needs power. Without power, the needle will go to the zero endstop. Wiring Schematic reference 32-41-03. During Standby Power operation, the Ground Handling Bus is unpowered.

    Cheers

    JHW

    P.S. I don't have the latest version of QOTS II, so perhaps someone can recheck these and submit a ticket?

     

     

  14. Posted

    Did you accidentally activate Pogo Stick power after you turned off the engines ?? 🤔


    Off topic, but I noticed a few other curiosities in that video clip:

    Should the PFD and ND blank after switching off the engines? Wouldn't Standby Power take over almost immediately? The Upper EICAS seemed ok.

    Shouldn't there be an [RA] flag on the PFD with no main bus power to the Radio Altimeters?

    Should there be an [FD] flag on the PFD? I'm not sure how it would behave with the MCP unpowered.

    Should the heading cursor be in view on the ND? The MCP is dead, so no computed data.

    Shouldn't the Brake Pressure Gauge be showing fully zero (power normally comes from the Ground Service Bus)?

     

    Unfortunately, I can't test this on the real aircraft anymore.

     

     

  15. Posted

     

    On 7/10/2018 at 12:00 AM, asdfgh said:

    it's possible to perform a turn right from where you remove your chocks.

    My 2 cents' worth:

    In the real world, you would almost never start turning a 747 straight away. You would normally clear most of the parking area before turning. This way, there would be less chance of colliding with aerobridges, mobile steps, aircraft on the next gate, light poles and lines of parked cargo equipment. Taxiways also provide a wider space for the turn. To get a sharp turn in a small amount of space, initially you may reach the nose gear turn angle limit for towing (65 degrees). Also, the larger the steering angle, the more strain there will be on the main gear. More than 20 degrees of nose gear angle forces the body gear steering to activate. This helps alleviate the twisting forces on the main gear during sharp turns.

    Anyway, it's not something I would recommend for a beginner tug driver. Pushing an aircraft is a little like reverse parking a very long trailer/caravan

  16. Posted

    12 hours ago, berts said:

    Another thing to look for on the real aircraft that is usually not mentioned in the abnormal checklist procedures, but always worth checking, is to see if a circuit breaker has popped.  Unless there is some obvious and very good reason not to do this, a single reset of the CB is permissible because it just might clear the fault(s). 

    Indeed. The Main and APU Battery Bus RCCBs have corresponding CBs on circuit breaker panel P6 in the cockpit. However, I don't know what the general policy is for resetting a circuit breaker of this magnitude. It guess it would be similar to resetting a GCB, but.. I don't know for sure.

    You can force the battery busses to use battery (or battery charger?) power using the Standby Power switch, but if there is indeed a short on one or more battery busses, you may do more harm than good. There are also RCCBs on the battery side of the battery busses, but if they didn't trip or didn't trip fast enough, you might affect the Hot Battery Busses, too. 

    Some of those fire loop messages are a little worrying. I thought the APU Bat Bus provided power for the B loops. I can't easily think of a scenario where both the APU and Main Bat busses would be affected. Only the PMDG team would know what this scenario involves.

     

    12 hours ago, berts said:

    The FLAPS CONTROL message is one of the more obvious clues here, because it is generated by the loss of the Primary Trailing Edge Flaps DC control. 

    Not sure. This comes back to whether or not the flap system can detect a DC power loss prior to flaps being used. Flap position data loss will be detected prior to flap use. Flap position transmitters use voltages from the FCEs. However, these voltages are derived from the overhead panel AC CBs. The FCE's do send (FCE status) data to user systems, but the text in the manuals is a little ambiguous regarding how (and when) that data is used.

    Unfortunately, without an airplane to experiment on, we probably will never know. I did pull FCE CBs a few years ago (for the purposes of sim development), but the CB combinations I used didn't give a full picture of their effect. Some combinations gave some pretty weird effects (such as the pitch limit indicators appearing on the PFDs with the flaps up).

    Cheers

     

  17. Posted

    On 9/15/2018 at 12:10 AM, 19AB67 said:

    FLAPS PRIMARY
       >NO AUTOLAND
       >YAW DAMPER UPR

    The status page on the lower CRT, I get even 3 pages full of messages: 

    E/E CLNG CARD
    ENG x OVHT LP B
    ENG x FIRE LP B (x = 1..4)
    MAIN DK FIRE LOOP y Z (y=1..8, Z= A; B)
    CLAP CONTROL
    STALL WARN SYS R, L
    STAB AUTO TRIM

    Complicated.

    e.g. STALL WARN SYS R, L

    This must be due to a sensor power failure rather than due to power to the stick shaker motors or MAWEA.The stick shaker motors are powered by the Main Battery Bus, but the aircraft would not know that the stick shaker motors were unpowered. There is no feedback from the motors.

    FLAPS PRIMARY

    I see some components of the flap system are powered by the main battery bus, but (in some cases) messages wouldn't be generated until you actually tried to move the flaps. There was a debate on another forum regarding what would happen if you lost DC power to the Flight Control Power Supply Units (FCE's). If you removed DC power (only), are you affecting the user systems or just the FCEs?

    I assume your problem is some kind of short on the battery busses. If there was a lot of current being drawn, the Remote Control Circuit Breaker/s (RCCBs) feeding the battery busses might have tripped (opened) before the short had time to drag down DC Bus 3 and the other DC busses. You would normally expect a power-related message if a TRU couldn't produce enough volts because of a short, but if the RCCBs acted before the current and voltage abnormalites were detected by the Generator Control Units, you wouldn't get a #3 TRU message and the #3 DCIR wouldn't trip.

    AFAIK, there are no voltage sensors on the Bat Busses themselves. If you looked at the battery indications, however, you might see that they were using very little current if the Remote Control Circuit Breaker/s for the Bat Busses busses had tripped and the battery relays were in their normal positions. In the case where the RCCBs had tripped, the batteries(or battery chargers in TRU mode) would not be commanded to take over from #3 Main DC Bus.

    This stuff is a lot easier to understand if you have a detailed schematic )))

  19. Posted

    On 9/2/2018 at 5:10 PM, VHOJT said:

    It is fairly common knowledge around the web that QF 744s have extra oxygen bottles that allow for depressurised flight at 14,000ft for a considerable number of hours, and even higher for shorter periods. This would help with minimising decompression fuel vs having to go down to the usual 10,000ft for hours.

    Cargo fire suppression is another issue on these long haulers. Some of the aircraft's fire bottles give an instant blast, but then other bottles feed a slower supply for a certain amount of time. After this, nothing... If the fire restarts or if you have a fire in another cargo area, you're in trouble.

  20. Posted

    I don't know how relevant this is, but the (real) 744 Approach Reference page allows a greater gross weight than your total, Angelo.

    A few years ago, on real 744s, I recorded the following values:

    Standard freighter (CF6) and pax (RR):

    154.2 ~ 408.2 Tonnes
    Airspeed range:
    (Flaps 25) 120kts to 199 kts
    (Flaps 30) 115kts to 191 kts

     

    747-400ER pax (CF6)

    154.2 ~ 435.5 Tonnes
    Airspeed range:
    (Flaps 25) 120kts to 206 kts
    (Flaps 30) 115kts to 197kts

     

     

     

     

  25. Posted

    23 minutes ago, thibodba57 said:

    How far into cruise are you checking the packs. All packs should be high until 30 min after reaching the programmed cruise altitude if I recall correctly. 

    Should be faster than that. The packs should go into normal flow in "Cruise Clamp". This is defined by:

    Above 25,000' and within 100 feet of cruise altitude.

    The ECS miscellaneous card receives the climb, cruise, descent and
    altitude information from the EIUs.

    This data is passed on to the pack controllers and other controllers.

    Not all packs should go into normal flow at the same time. There should be a 15 second delay between packs.

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