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cj-ibbotson

747-400X Climbout

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Hi Guys,I have had the excellent 744X for a few months now and I'm slowly learning various aspects to it's manual and automatic flight when time allows it (can't fly in FSX as much as would like). I do however have a question. I understand how to enter the performance data i.e. fuel and load weights etc into the FMC and for it to generate V1, VR and V2 speeds, I click on the LSK keys to upload them to the PFD. From what I understand on takeoff I would have runway heading selected on the MCP together with V2+10 on the speed bug. The problem occurs when I advance the throttles, allow the engines to stabilise then press the TOGA switch. ThrustRef becomes annuniated on the PFD which is fine and the throttles advance and the aircraft increases speed down the runway. I reach VR and begin rotation then V2 is called out I then have a problem with maintaining a set speed. If I fly by hand and follow the FD the aircraft still accelerates pretty fast and I dont have time to retract flaps etc. I was under the impression from some excellent dvds I have watched like the ITVV Virgin Atlantic 747-400 that the aircraft retains a set speed until Thrust Ref changes to SPD from which the aircraft should pitch the nose down and start increasing in speed. If I increase the pitch to control the speed my altitude increases too fast and I overshoot any altitute restrictions on the particular SID I'm following. Even enabling the AP immediately after takeoff will usually cause a sudden decrease in speed and descent in altitude as I have quickly passed that set on the MCP or in the FMC LEGS page. I haven't played around with any Derate settings etc so perhaps this is the problem based on the weight of the aircraft i.e. too light using max thrust.Any help would be much obliged.RegardsChris Ibbotson


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Chris Ibbotson

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Hi ChrisMax thrust at low weights is very hard to control if you want to keep ahead of the aircraft. Try and get hold of a program called TOPCAT and it will calculate your derates for you.Rob


Rob Prest

 

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Chris,It looks as if you could get a great deal from following the PMDG tutorials. They explain all this in excellent detail, and give you the exercises to go through to understand how the aircraft reacts to your inputs. Give it a try, and then give us all some feedback on your experiences.Good luck!Regards, Richard


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Thanks for the inputs so far. Yes perhaps you are correct I have read a lot on the PMDG manuals and have downloaded the 4 Type Rating tutorials. I also have a very comprehensive tutorial from Craig Read which I will browse through too. One thing I never did before was engage LNAV and VNAV prior to commencing my takeoff procedure. I see now that pilots do press these and they are shown in White on the PDF then presume go green when the AP is engaged. I always pressed these after takeoff then engaged the AP so perhaps this isnt helping either. Its all a learning curve so I will read more and try a few things.ThanksChris Ibbotson


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Chris Ibbotson

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Hey Chris,Sounds like you're already pretty knowledgeable about the takeoff procedure. As was mentioned, the weight may be your issue. In this case, you can 'derate' the thrust so you aren't doing a major climb after the takeoff. To get this done, press 3 keys on the FMC. 1-INIT REF 2- INDEX LSK6L 3-THRUST LIM. Changing your thrust will be done on the ground, as this page switches to another mode when airborne. The preset values of 5 or 15 should do just nicely.In addition, remember that speed is always controllable with pitch. After takeoff, you have to climb at least 400 feet before you can engage the AP. I suggest a minimum of 800. Pull the yoke back, you lose airspeed, push it forward, you gain airspeed. Flight director is a bit unreliable at times in the initial climb, so watch the airpseed.As you said, having LNAV and VNAV should help. This means that at your chosen engagement altitude (mine is 800) you will simply press the center autopilot, and you LNAV and VNAV will automatically engage. I'm not sure if this even helped, but I sure hope it did.


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Chris:I would FIRST get TOPCAT (http://topcat.ofplan.net/?page=main).That way you will get proper derates for your T/O weights and conditions.Even more important than the engine savings, is the fact that a properly derated T/O will give you an approx. 55 second T/O roll, allowing for proper monitoring of HOLD, 80kts, V1, Vr, V2, LNAV and THR REF VNAV SPD.Yes, the MCP ought to have V2 (or V2 +10 based on SOPs), initial heading and initial cleared altitude. LNAV AND VNAV ought to be armed (white) and your FMAs ought to read Blank TOGA TOGA, Blank LNAV VNAV armed.At rotation fly 10 1/2 degrees, wait for the unstick, and then once through 50' pitch for speed- forget the FD for PITCH NOT ROLL (notoriously unreliable at initial high body angles) and FLY AIRSPEED! If you loose an engine you will be very glad you did!Once 1000agl (or 1600 or whatever engine out is) you can fly the FD for pitch as well- keep in mind LNAV and VNAV will be reflected by the FD bars- you could conceivably fly the whole flight in LNAV and VNAV without ever relinquishing control to the AP. As long as you keep the FD happy, you WILL fly the programmed flight profile. The AP just does it for you automatically- they are completely independant of each other.Remember you can STILL fly SPD INTV if you want to (for noise abatement) through the flap retraction sequence, in or out of the AP! Despite all the automatics, she will still fly on raw data- just like a 172.Best-Carl F. Avari-Cooper BAW0225http://online.vatsimindicators.net/980091/523.png| XP Pro SP3 | 2 x APC UPS | Coolermaster Stacker 830 SE | Gigabyte P35 DS3R | e8500 @ 4gHz | Tuniq Tower 120 | EVGA 8800GT 512MB | Creative X-Fi Fatal1ty | 2 x 1 GB Corsair XMS2 | 2 x 320GB WD Caviar RAID 0 | Corsair HX620W PS | CH Products Yoke-Pedals-Throttle Quadrant | Aerosoft 747MCP-EFIS-EICAS |


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Carl Avari-Cooper

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I'm all for a high performance climb! :D It's not that difficult to fly a light jet at full power, but you've got to be on the ball. An obvious side-effect is that the V-speeds occur much quicker, so there is less time for things to fail on the ground (but statistics show that isn't such a bad thing).As was mentioned above - control speed with pitch. Just be careful not to over-rotate and strike the tail. Once established in the climb, throttle back, and manage pitch/power as normal.Best regards,Robin.

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