Acceleration Alt/Thr Reduction

[Guest frankathl]

I really enjoyed and learnt much from the thread on flap retraction altitude. Thank you, guys! :-)A small clarification on the headline topic, if you please?Assuming I want to begin flap retraction at 1000', should I reduce to climb power before speeding up, or should I increase speed and let the transition to climb thrust happen automatically at 1500'? Does it matter?So,1000'Push N1 to reduce to climb thrustV2+15/20 ---> 220k using MCP Speed windowretract flaps on schedule---or---1000'V2+15/20 ---> 220k using MCP Speed windowretract flaps on schedule1500'FMC automatically transitions to climb thrustOh, one other thing! A lot of the examples offered in the thread on flap retraction altitude did not mention engagement of the A/P in CMD.Does that mean that many of you, including R/L pilots fly a lot in F/D mode only? Thanks,Frank

[zubart 5]

>I really enjoyed and learnt much from the thread on flap>retraction altitude. Thank you, guys! :-)>>A small clarification on the headline topic, if you please?>>Assuming I want to begin flap retraction at 1000', should I>reduce to climb power before speeding up, or should I increase>speed and let the transition to climb thrust happen>automatically at 1500'? Does it matter?>>So,>1000'>Push N1 to reduce to climb thrust>V2+15/20 ---> 220k using MCP Speed window>retract flaps on schedule>>---or--->>1000'>V2+15/20 ---> 220k using MCP Speed window>retract flaps on schedule>1500'>FMC automatically transitions to climb thrust>>Oh, one other thing! A lot of the examples offered in the>thread on flap retraction altitude did not mention engagement>of the A/P in CMD.>Does that mean that many of you, including R/L pilots fly a>lot in F/D mode only? >>Thanks,>FrankFrank,Yes, at 1000 feet AFE, Push N1, Bug Up and set Flaps UP maneuvering speed. Verify flight and thrust mode annunciations on the FMA at thrust reduction altitude.In this airplane the FAA says no Autopilot until passing 400 AGL.Unless you have a good reason to I wouldn't engage the autopilot until the flaps are up and your passing 3000 feet. In the real 737NG, there are some requirements in order for the autopilot to engage such as no force being applied to the control wheel and if pitch and roll commands are more than 1/2 scale from center, pushing CMD A or B switch engages the A/P in CWS for pitch and/or roll and the related F/D bars(s) retract. So you see, you don't want all this going on during this critical phase of flight. Its better to fly the airplane with the Flight Directors to at least 3000 feet AFE and engage the autopilot. I know the PMDG 737's autopilot always engages the first time with no distractions but I'm telling you how it is in a real 737NG. The autopilot may not engage on the first attempt.In real 737NG operations, I find that most pilots will engage the autopilot between 3000 feet and 10,000 feet, few pilots will wait until 10,000 feet, very few will wait until cruise and nobody will cruise without the autopilot engaged.Floyd

[Guest frankathl]

Thank you, Floyd. Yes, I see your point about the autopilot. Very interesting!"Yes, at 1000 feet AFE, Push N1, Bug Up and set Flaps UP maneuvering speed." I am a bit unsure about the meaning of "Bug Up" in this context? I thought Bug Up = Flaps UP Airspeed, but obviously I am wrong(?)BR,Frank

[zubart 5]

Frank,"Bug Up" means to reposition the magenta airspeed bug on the PFD to the green "UP" using the MCP airspeed window. That's standard Boeing phraseology used in real line. The flying pilot will say to the non-flying pilot at 1000 feet AFE, "N1, Bug UP, Flaps 1" for a flaps 5 takeoff (at least V2+15) or just "N1, Bug Up" for a Flaps 1 takeoff. Then retract the remaining flaps on schedule in both scenarios. Floyd

[Guest frankathl]

Ah, got it now, Floyd! Thanks for the clarification.BR,Frank

[Guest tomahawk_pa38]

Floyd,Ah, this goes on to a bit I've never really understood ! After pressing N1 and pulling in the flaps, when and how does the fmc know when to switch over to show fmc speed or does it remain in N1 or is this happen when the a/p is engaged ?

[zubart 5]

>Floyd,>>Ah, this goes on to a bit I've never really understood ! After>pressing N1 and pulling in the flaps, when and how does the>fmc know when to switch over to show fmc speed or does it>remain in N1 or is this happen when the a/p is engaged ?Dave,In a nutshell,A very complex question. As you fly, study the FMA closely and watch the A/T, Roll and Pitch modes change during different phases of flight.The FMC will not enable FMC SPD alone. You will have to engage VNAV to see FMC SPD on the FMA. You'll only see FMC SPD displayed on the FMA when VNAV PTH is also displayed during CRZ.For example, during a climb, you engage VNAV and the modes displayed on the FMA will be, N1 for A/T, LNAV or HDG SEL for roll and VNAV SPD for pitch. As the airplane approachs CRZ altitude the FMA display will change to, FMC SPD for A/T, LNAV or HDG SEL for roll and VNAV PTH for pitch.It won't matter if the autopilot or even F/D's are engaged or not.Make sense?Floyd

[Guest tomahawk_pa38]

Floyd,Thanks - I tried this over the weekend and began my takeoff run using the TOGA button, but I'm sure after t/o that I couldn't push the N1 button - it just wouldn't do anything. I'll try it again next weekend and se if it works.

[victorlima01 2]

One more question for Floyd: Ok I think I'm getting things right. Please check my work and see if it's close to the real thing: after engine start and cleared for taxi arm F/D and A/T. Arm Lnav or HDG SEL when aligned with runway, push TOGA and monitor EICAS, after takeoff maintain V2+15-20 till THRUST RED/ACCEL HEIGHT (1000 or 1500). at this altitude "N1, bug up, Flaps 1".From now on I get confused. How do I know what height to select from thrust reduction? Does each carrier have a specific way of doing this depicted in their sops? When the aircraft passes thru the green "1" on the speed tape I retract from flaps 1 to flaps up? Furthermore how do I know what's the bug up speed? Is it the one where there's the green "up" (seems to change depending on conditions)? Finally, what about when the aircraft achieves bug up speed? Should I arm Vnav or select 250 in the speed window of the FMC and press LVL CHNG? And is it only after all this that I should engage A/P? And one more please: I don't think I understand the difference between Thrust reduction height and accel height. What I don't understand really is how come the 737's FMC will only let us input thrust reduction and not accel height. The other Boeing FMC I'm familiar with (777), has both these entries for the pilot to enter a number and I've always understood this the following way (please correct any mistakes): if I select Trust red height 1500 and Accel height 3000 (i.e noise abatement procedures)I understand that the airplane will reduce to CLIMB TRHUST upon reaching 1500'AFE but the F?D will only direct the pilot to reduce pitch to gain airspeed upon reaching 3000'AFE correct? When this is the case, when should I commence flap retraction? And how can I do this procedure on the 737NG provided I cannot choose the accel height in the FMC?The more I write, the more quesiotns keep popping up... better stop for now. Thnaks for the previous posts Floyd, very very helpfulCheers, Victorhttp://www.precisionmanuals.com/images/forum/800driver.jpg

[zubart 5]

>One more question for Floyd: Ok I think I'm getting things>right. Please check my work and see if it's close to the real>thing: after engine start and cleared for taxi arm F/D and>A/T. Arm Lnav or HDG SEL when aligned with runway, push TOGA>and monitor EICAS, after takeoff maintain V2+15-20 till THRUST>RED/ACCEL HEIGHT (1000 or 1500). at this altitude "N1, bug up,>Flaps 1".Yes, you are correct. Only one item I would change. Turn on both F/D's at the gate before engine start. >>From now on I get confused. How do I know what height to>select from thrust reduction? Does each carrier have a>specific way of doing this depicted in their sops?Yes. >When the>aircraft passes thru the green "1" on the speed tape I retract>from flaps 1 to flaps up? Yes.>Furthermore how do I know what's the>bug up speed? Is it the one where there's the green "up">(seems to change depending on conditions)?Yes. >Finally, what about>when the aircraft achieves bug up speed? Should I arm Vnav or>select 250 in the speed window of the FMC and press LVL CHNG?>And is it only after all this that I should engage A/P? Boeing SOP is to engage VNAV for pitch only after passing 3000 feet AFE. Until then you can engage LVL CHG for Pitch. You can also stay in TO/GA for pitch and then engage VNAV passing 3000 feet. Engage the autopilot only after cleaning the airplane up and your no longer in a critical phase of the takeoff usually around 3000 feet AFE.> >>And one more please: I don't think I understand the difference>between Thrust reduction height and accel height. What I don't> understand really is how come the 737's FMC will only let us>input thrust reduction and not accel height.I can't answer this.> The other Boeing>FMC I'm familiar with (777), has both these entries for the>pilot to enter a number and I've always understood this the>following way (please correct any mistakes): if I select Trust>red height 1500 and Accel height 3000 (i.e noise abatement>procedures)I understand that the airplane will reduce to CLIMB>TRHUST upon reaching 1500'AFE Yes.>but the F?D will only direct the>pilot to reduce pitch to gain airspeed upon reaching 3000'AFE>correct? No. Not automatically. To accelerate passing 3000 feet you would have to do one of the following, Bug Up, LVL CHG or VNAV, otherwise the F/D will just continue to command V2 + 20 until you engage one of these pitch modes. You could also use VS but its just not down in real line flying.>When this is the case, when should I commence flap>retraction?If your doing a noise abatement procedure like CYVR has, then the first flap retraction will be at 3000 feet AFE. If your just doing a standard takeoff then the first flap retraction will be 1000 feet AFE.> And how can I do this procedure on the 737NG>provided I cannot choose the accel height in the FMC?Do it manually.>>The more I write, the more quesiotns keep popping up... better>stop for now. Thnaks for the previous posts Floyd, very very>helpful>>Cheers, Victor>>>http://www.precisionmanuals.com/images/forum/800driver.jpgI understand.Floyd

[Guest frankathl]

Could I ask if "acceleration height" refers only to the height at which we increae speed in order to accelerate through the flap schedule, or has it other references, also? As, for example, at 3000', when we increase speed to 250k, or above 10,000' when transitioning to cruise speed?Thanks,Frank

[zubart 5]

>Could I ask if "acceleration height" refers only to the>height at which we increase speed in order to accelerate>through the flap schedule,Yes.> or has it other references, also?>As, for example, at 3000', when we increase speed to 250k, or>above 10,000' when transitioning to cruise speed?>>Thanks,>FrankAcceleration height only refers to the altitude after takeoff when thrust is reduced to CLB, flap retraction is started and the airplane climb rate is reduced some what to accelerate to "clean up".I've never heard it referenced to any other phase of flight.Floyd

[victorlima01 2]

Floyd once again thank you very much for your answers. I think I'm done now, but don't count on it! :)Cheers, Victorhttp://www.precisionmanuals.com/images/forum/800driver.jpg

[Guest frankathl]

Thanks, Floyd, for clarifying this term for me!Then, Acceleration Altitude = Thrust Reduction Altitude.Right?BR,Frank

[victorlima01 2]

I'm gonna try to reply this one nut I might be wrong here Frank. Not necessarily the same, because as I mentioned earlier in some aircraft (for example B777 and A320 series) the FMC will let you imput different values for both these altitudes. And in noise abatement procedures the THRUST RED height does not coincide with ACCEL HEIGHT. I tend to think of it in the following way:THRUST RED height: Height AFE where A/T changes over from Takeoff N1 thrust setting to the selected Climb N1 setting (so you have a reduction in thrust output). I believe this procedure has to do with fuel economy and preserving the engines. After all, once you're at a certain height (say 100 AFE) with gears up and no more immediate terrain to clear you don;t need all that power form takeoffACCEL height: height at which the flight director will lower i'ts horizontal bar in order for the aircraft to command such a pitch as to accelerate quickly thru the flap retraciton schedule whilst still climbing (at a lower climb rate than the one prior to reacing ccel height).I hope I didn't confuse you Frank, anyway that's my take on the matter and I'm only a private pilot!Cheers Victorhttp://www.precisionmanuals.com/images/forum/800driver.jpg