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pdgetrf

questions on take-off and vnav

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HiI use default FMC setup for takeoff and noticed that if there is no route or no waypoint in LEGS (sometimes I don't have any waypoints when I practice touch-go in traffic pattern over an airport), VNAV cannot be armed (VNAV textgoes white and then disappears on PFD) either on the ground or after airborne, and through out the climb after flaps 5 VNAV is not taking over to lower the angle for speed up, and it's stuck in TO mode. I understand that VNAV is the vertical profile of the flight plan and therefore , no plan, no profile (right?). The flaps 5 setting is in TAKEOFF REF and seems to have nothing to do with vertical profile. What's the logic in this? Also, from the FMC VNAV page 1, I can't find anything related to the flight plan, then why doesn't matter if there is a flight plan or not to use VNAV for takeoff?Thanks!

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HiI use default FMC setup for takeoff and noticed that if there is no route or no waypoint in LEGS (sometimes I don't have any waypoints when I practice touch-go in traffic pattern over an airport), VNAV cannot be armed (VNAV textgoes white and then disappears on PFD) either on the ground or after airborne, and through out the climb after flaps 5 VNAV is not taking over to lower the angle for speed up, and it's stuck in TO mode. I understand that VNAV is the vertical profile of the flight plan and therefore , no plan, no profile (right?). The flaps 5 setting is in TAKEOFF REF and seems to have nothing to do with vertical profile. What's the logic in this? Also, from the FMC VNAV page 1, I can't find anything related to the flight plan, then why doesn't matter if there is a flight plan or not to use VNAV for takeoff?Thanks!
Hi,Because your not fully programming the FMC for pattern work push the 'THR' Button on the MCP to get out of T/O mode, this will activate thrust reduction and the aircraft will climb at whatever thrust setting you selected (CLB1/CLB2) the aircraft will automaticly accelarate to your clean speed when you reach the acceleration altitude set in the FMC providing you retract flaps on schedule.As stated VNAV is not available unless you have at least a basic route entered, even entering the arrival and daparture runway is enough.If you don't want to use a route then use FLCH, V/S and HDG SELECT.Regards

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Thanks for the headsup and reply. And no I don't have many experience flying these high-end add-on. That's why I'm asking.
I figured as much, I just wanted to make sure so I didnt give an answer that was unhelpful.VNAV is best used as a mode for climb and descent to follow a flight plan. You put in this flight plan in the FMS during your preflight items. This includes the route which you filed, as well as departure runway, departure procedure, arrival procedure, planned/probable approach, and landing runway. With all this information, you can plot your flight plan both as points on the map, as wel as altitudes in the sky. If you look at DPs and STARs charts (check out skyvector or flightaware to see some US airport charts), you will see certain "crossing restrictions", such as pass the HASBO intersection as 14000 AMSL. Either by selecting the DPs or STARs via the DEP/APP button on the FMS, or by entering those in yourself, you can set it up that the autopilot will respect those restrictions, as well as the universal <250 kts when under 10,000 ft.So once you have your whole flight planed out, both the route, and the performance page (which is wher you select your crusie altitdue, step climbs, cost index (which is your fuel burn), and other things), you will get the line "Preflight complete".Assuming you have your FMS preflight complete, you can then take off.Enter the runway, arm autothrottle, turn on your strobe, your landing lights, throttle up to about 40-50 % N1, then hit the TOGA button (screw on the MCP), and the A/T will spool up to TO power. At V2, pull back on the yoke and take her up into the air following the flight director on your PFD.At 400 feet AGSL (the radio altimeter, not the barometric altimeter that gives you feet above sea level), arm LNAV or Heading Select, base on your departure procedure. At 1,000 feet AGSL, arm VNAV, and turn on the the Left in Command. Retract your flaps on schedule, and you are cleared to your destination as filed.

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VNAV and LNAV are armed on the ground. Sometimes even before push back. Auto Throttle is also armed at the same time. When you look in on the taxi out conducting your FMA's Flight Mode Annunciations), you call, "Blank TOGA TOGA, LNAV VNAV armed" Then you announce the block altitude set. If thats how it's all been set as.The is the most important thing to learn if you want to keep it real life, is your FMA's. They are called as they change. After the PNF calls positive rate, you call "Gear Up" The next FMA you will get is LNAV. That comes at 50 feet. You call "LNAV". Then, as Scott said, at about 400 feet, you get "THRUST REF. VNAV SPEED" You would then call that aloud. Then the choice is yours. Manual fly following the Flight Director or call for one of the Autopilots to command. One pressed, you annouce "Command Green"Hope this helps.Buzz.

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Thank you all for reply and kind explanation. Looks like THR is the solution to the scenario where I don't have a flight plan to use like in the case of flying traffic pattern to practice touch and go. I gave the manual another read and it's explained as the following:THR Switch: If current mode is FLCH,SPD, VNAV SPD, VNAV PTH, VNAV ALT orTO/GA, pressing the THR switch changesthe thrust limit to the CLB thrust setting.This setting will be displayed on the PrimaryEICAS. This does not affect the autothrottlemode, but changes the thrust limit allowed.Thrust Reduction: ... ... This will occur automatically if VNAV and the autothrottle are engaged.Now pieces start to fall together for the case of manual (no VNAV, therefore no automatic thrust reduction) takeoff:(1) Flap acceleration height set in TAKEOFF REF page, say 1000 feet (2) At takeoff, follow the FD clue to pitch for climb and maintain V2 (or V2+10). At 500’ AGL, VNAV is going to activate and take over pitch commands to the flight director (according to the type rating course lesson 2), and manage climb and acceleration from now until level off. So if VNAV is not even armed, at flap acceleration height pitch does NOT come down for speed up.(3a) If VNAV is armed (requiring a flight plan, or at least a few waypoints in the LEG page) when reaching this height, VNAV takes over the control and lower the pitch to start flaps retraction by speeding up, and when flaps 5 is reached, thrust change from THR REF to CLB setting and higher speed is set automatically (up to 250 as set in the VNAV page of FMC). Now and after, FLCH can be used for further climb and level-off(3b) If VNAV is NOT armed, at flap acceleration height, either press THR to bail out of TO/GA mode into CLB mode, manually set a higher speed in MCP IAS/Mach window (up to 250) and lower the pitch according to FD (which reacts to the new lower thrust setting and higher speed in window) to speed up and retract flaps, or use FLCH which picks the best thrust setting for climb and uses the speed selected in MCP IAS/Mach window.The difference between 3a (automatic) and 3b (manual) is that in 3a, speed up at flaps retraction height starts with THR REF setting while in 3b it's in a lower setting: CLB or the one picked by FLCH. This is under the assumption that the plane is flied solely as indicated by FD.

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VNAV and LNAV are armed on the ground. Sometimes even before push back. Auto Throttle is also armed at the same time. When you look in on the taxi out conducting your FMA's Flight Mode Annunciations), you call, "Blank TOGA TOGA, LNAV VNAV armed" Then you announce the block altitude set. If thats how it's all been set as.The is the most important thing to learn if you want to keep it real life, is your FMA's. They are called as they change. After the PNF calls positive rate, you call "Gear Up" The next FMA you will get is LNAV. That comes at 50 feet. You call "LNAV". Then, as Scott said, at about 400 feet, you get "THRUST REF. VNAV SPEED" You would then call that aloud. Then the choice is yours. Manual fly following the Flight Director or call for one of the Autopilots to command. One pressed, you annouce "Command Green"Hope this helps.Buzz.
You can arm LNAV or HDG SEL on the ground, but Boeing has put out that arming VNAV on the ground can cause problems, so SOP is to avoid doing that. While I am sure doing so will not result in the FMS issues in the PMDG, I personally abovid arming VNAV until I deem the aircraft is climb and is under control. My thinking is that I will continue to fly to the minimum action altitude using the TO logic on the FD, which in some cases I extend up the 1500 on very heavy loads, then I turn on VNAV and Left in Command at the same time. I will only turn on VNAV when I put the plane in autoflight.

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You can arm LNAV or HDG SEL on the ground, but Boeing has put out that arming VNAV on the ground can cause problems, so SOP is to avoid doing that. While I am sure doing so will not result in the FMS issues in the PMDG, I personally abovid arming VNAV until I deem the aircraft is climb and is under control. My thinking is that I will continue to fly to the minimum action altitude using the TO logic on the FD, which in some cases I extend up the 1500 on very heavy loads, then I turn on VNAV and Left in Command at the same time. I will only turn on VNAV when I put the plane in autoflight.
Some airports require a noise abatement departure, i.e EGLL. So Climb Thrust is set to an altitude before flap retraction. The FMC defaults to climb thrust at flaps 5. QF FCTM recommended setting climb thrust at flaps 5 unless noise abatement is required. Also, the Flight Director will not command nose down for flap retraction unless VNAV is armed. You don't have to use the Auto Pilot, just fly the Flight Director.In that case VNAV would have to be armed to fly the profile programmed within the FMC.As I've said in a previous post, this is the difference between PMDG and the real thing. It is a lot harder hand flying following the Flight Director in the real thing!Hope all this is helping you understand the 744. :( Buzz

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Just to add to what Marty has said,BA FCTM directs pilots to 'look through the F/D' on rotation' aiming for an initial pitch attitude after lift off of 12-12.5 degrees nose up, at V2 + 10kts to V2 +20kts. It also adds that F/D pitch indications should be ignored below 400ft aal.It also advocates the use of VNAV, & as such it is armed as part of the preflight set up of the MCP & is an item on the Before Start Checklist.BA FCTM also advocates Packs OFF if the PTOW is above 300t & CLB Thrust with the selection of Flap 5, unless a noise abatement procedure is required. Packs are selected ON again once CLB Thrust is set.For a standard noise abatement departing LHR the BA FCTM calls for Flap/Accel at 1000ft aal, CLB Thrust at 1000ft aal & then SPD INTV as the Flap 10 bug is passed to Flap 10 +10kts. Flap 10 is selected passing the Flap 10 bug. The terminating altitude for a noise abatement at LHR is 4000ft aal & this configuration is maintained until passing 4000ft aal whereupon a normal clean up is continued. The rationale is that this configuration places the aircraft in a condition whereby the noise footprint is minimised. It goes on to add that where ATC allow the aircraft should be accelerated to the ECON CLB SPD as soon as possible after the Noise Abatement (approx 328kts/M.840) even if below FL100, & once the aircraft is clean (flaps up) CLB1 should be selected to preserve engine life.Noise abatement techniques & altitudes differ from ARPT to ARPT as does the terminating altitude, some like HKG call for different procedures altogether such as the NDAP1 & 2 options.

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