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Go around speeds and clean-up


badderjet

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Hello,

 

didn't find too much using the search so far.

 

I am unsure about what speeds are displayed during G/A (esp referring to magenta bug). Say I shoot a (manual) ILS and hit TOGA at 200' RA, flaps go back to 15, gear up on positive rate. The magenta bug is not going to exactly any flap maneuvering speed but it just goes somewhere in between. When and how am I supposed to clean up? Normal acceleration altitude as I would use on takeoff? Do I just select UP speed? Because the magenta bug somewhat increases whenever I just start to retract the flaps, and I still don't understand the values it points to.

 

Second question: During automatic G/A the first button push will go to limited G/A thrust. When flying manually, I was wondering if A/T should be in ARM for a potential go-around (because I think it should not, at least not in any other stage of flight when A/P is off), since otherwise I will never have the "reduced thrust option" when flying manual, correct?

 

Any useful info there?

 

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I only ask this because I don't know the answer exactly, but have you checked the FCOMs?  I'm guessing you could easily find your answer there.  You might have, but you said "search," which I'm guessing only extends to Google and possibly the forum here.

 

Manual first - then the rest.

Kyle Rodgers

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I only ask this because I don't know the answer exactly, but have you checked the FCOMs?  I'm guessing you could easily find your answer there.  You might have, but you said "search," which I'm guessing only extends to Google and possibly the forum here.

 

Manual first - then the rest.

Good old FCOMS. I read a few pages during lunch every day. Co-Worker asks, "what ya reading?" Me: How to escape from the overhead cabin crew rest Version 2, on a 777.

 

Co-worker: "Isnt the 777 that Malaysian plane?" Me: Blank look.

 

In short, the manuals are the hidden gem of the PMDG product line-up. Read them. Not all in one night though.

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Hey folks,

 

if you have answers, I'd be happy if you could provide a reference. Sure enough it's possible to overlook something in thousands of pages of documentation.  B) If I had found clear answers I certainly wouldn't ask here.

Regarding the indicated speeds, we can find in FCOM 2 4.20.27, F/D Go-Around:
 

The command airspeed cursor automatically moves to a target speed for the existing flap position based on maximum takeoff weight calculations.

Now what exactly is "a target speed"? Flap maneuvering speed? Seems to be in the NGX, but still: wondering what the benefit is flying with MTOW numbers here, as the current weight should still be available to the FMC.

Regarding G/A thrust we find under the same section:
 

With the first push of either TO/GA switch:
- A/T (if armed) engages in GA and advances thrust toward the reduced go-around N1...

Nowhere does it say if having A/T armed would ever be used to get the reduced N1 during a manual G/A (probably not, according to FCTM 1.43, but I just want to make sure).

FCOM 1 NP.21.78, Go-Around and Missed Approach Procedure:

 

At acceleration height, call "FLAPS ___" according to the flap retraction schedule.


FCTM 5.86, Go-Around and Missed Approach - All Engines Operating on the same topic:

 

The minimum altitude for flap retraction during a normal takeoff is not normally applicable to a missed approach procedure. However, obstacles in the missed approach flight path must be taken into consideration. During traning, use 1,000 feet AGL to initiate acceleration for flap retraction, as during the takeoff procedure.

Nowhere does it say what to use for non-training. Also FCTM 5.84, G/A schematic, doesn't say more. So if the answers are hidden somewhere else, please provide a page number. I'd appreciate it! :Applause: Or if you know examples from line operations, I'd be glad to hear about these as well.

Thanks,

 

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Now what exactly is "a target speed"?

 

FCTM 5.86 "Command speed automatically increases to maneuvering speed for the existing flap position."

 

 

 


wondering what the benefit is flying with MTOW numbers here,

 

Possibly it could be done for safety or required by regulations.

 

 

 


Nowhere does it say what to use for non-training.

 

As by company SOP or airport requirements.

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Etienne-

 

Regarding your first question: When executing a go-around all you want to do is gain altitude FAST! As long as you don't bust 250knots below 10.000' or get dangerously slow it's all good. On any ILS- or approach chart in general the go-around procedure is described precisely with all its limits and possible restrictions. Don't just follow the magenta cross or any magenta bugs during critical phases of the flight such as takeoff, landing or a go-around. Always be ahead of your plane with your hands on the yoke and the throttles. 

 

To your second question: Why would you want the reduced thrust for your go-around in the first place? The derated N1 which you might have set for your takeoff should jump back to the default rating of your engine (which depends on the airline you are flying) after you have reached the CLIMB or CRUISE phase. If you want to apply the go-around thrust manually, simply smash those levers full forward, verify a positive rate of climb, retract the flaps and the gear, make sure you're following the published go-around procedures for your particular approach and only THEN you can bother about your thrust, which you can either continue managing manually or switch on the AT to reduce the workload, which is totally appropriate in this situation. 

In the NG you normally would not fly manually with the AT armed, as is the case with more modern and complex airliners such as the 777 or any Airbus. 

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Now what exactly is "a target speed"? Flap maneuvering speed? Seems to be in the NGX, but still: wondering what the benefit is flying with MTOW numbers here, as the current weight should still be available to the FMC.

 

The manual seems pretty clear here.  It's moving to a target airspeed for the current flap position given max weight conditions.  Remember that various aircraft speeds increase with weight (namely, stall).  If it sets the max weight scenario, you'd be safe at all weights with that speed set in there.  There's no need to add additional layers of calculation and complexity by trying to optimize that speed for the current weight.  If you're safe at 180 at MGW, then you'll be safe at 180 at with min fuel, too.

 

The vague manner in which it is described leads me to believe that it's simply a value they've come up with as a safe value (likely calculated as a buffer off of stall speeds in a given config) for recovery from a high drag state.  While I applaud your curiosity, I don't think there's a ton to be gained by figuring out everything that goes into it for the operation of the aircraft.

 

 

 


Nowhere does it say if having A/T armed would ever be used to get the reduced N1 during a manual G/A (probably not, according to FCTM 1.43, but I just want to make sure).

 

Not sure what the question/issue is here.  The manual is simply stating that, with A/T armed, pressing TO/GA will put it on the G/A limiter as indicated on the EICAS (unless I'm misunderstanding it).  My understanding is that, without A/T armed and physically handling the throttles, you have full authority to place the throttles at the full forward stop for max thrust beyond the G/A bug on the EICAS.  I could be wrong.

 

TO/GA (no A/T):

-F/D will provide G/A cues

-You have to set thrust manually

 

TO/GA (with A/T):

-F/D will provide G/A cues

-A/T will place the thrust levers on the indicated G/A bug ("reduced" in the manner that it's not max rated thrust as placing the throttles on the forward stops would get you)

 

 

 


Nowhere does it say what to use for non-training. Also FCTM 5.84, G/A schematic, doesn't say more. So if the answers are hidden somewhere else, please provide a page number. I'd appreciate it! Or if you know examples from line operations, I'd be glad to hear about these as well.

 

It does, and you quoted it: use the acceleration height.  The reason that it's not specific is - cue my surprise face :lol:  - it changes!  And then we can cue my other normal line of "aviation isn't as rigid as many think!"  Accel height is an AGL value, and it can vary by whatever departure procedure you ascribe to (ICAO NADP, airport specific, operator specific, or otherwise).  Think about a go around at KSNA here...retracting to flaps up will be delayed to get back up to 3000 first (obviously, safety permitting, though those in SoCal will still complain it was too loud).

 

The reason is says "for training, use [...]" is that the training is meant to cover the G/A in particular, and not distract the training from that goal by trying to also bring in the variables of different departure profiles.

 

If you're curious about departure profiles, in general, so that you have a better idea of accel height for various operations, here's a brochure on NADP:

http://www.b737mrg.net/downloads/b737mrg_noise.pdf

 

Note NADP 1 has you cleaning up and accelerating to flaps up speed (by the flap schedule) at 3000.   NADP 2 has you do this beginning at 800.

Kyle Rodgers

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Why would you want the reduced thrust for your go-around in the first place? The derated N1 which you might have set for your takeoff should jump back to the default rating of your engine (which depends on the airline you are flying) after you have reached the CLIMB or CRUISE phase. If you want to apply the go-around thrust manually, simply smash those levers full forward, verify a positive rate of climb, retract the flaps and the gear, make sure you're following the published go-around procedures for your particular approach and only THEN you can bother about your thrust, which you can either continue managing manually or switch on the AT to reduce the workload, which is totally appropriate in this situation. 

 

There are several very good reasons why you wouldn't want to go full thrust on goaround... some of which include the pitchup moment, which will be quite pronounced, other that a lot of stuff happens very fast, and the last thing you need is to worry about super high thrust producing engine shooting you through altitude constraint at 3000fpm+.

 

If you need the extra thrust... it is just another click away.

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Second question: During automatic G/A the first button push will go to limited G/A thrust. When flying manually, I was wondering if A/T should be in ARM for a potential go-around (because I think it should not, at least not in any other stage of flight when A/P is off), since otherwise I will never have the "reduced thrust option" when flying manual, correct?

 

We fly all of our normal approaches with the A/T engaged to touchdown, A/P on or off.  To go around, press TOGA once and you get enough power to climb around 2000 FPM.  At 400' with both engines operating the F/D will auto bug up for you.  Just stay in the flight director and retract the flaps on schedule.  Works great.

 

Single engine approaches are a different story.  A/T has to be off for those you you need to apply go around thrust manually.  The auto bug up doesn't happen on a single engine go around either.  On a single engine go around we fly the TOGA mode to 1000' AFL, select VNAV and accelerate and retract the flaps on schedule.

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Folks,

 

thanks for the replies and the discussion. Helps quite a bit when a bunch of people just throw in a few opinions on the topic. B)

 

To your second question: Why would you want the reduced thrust for your go-around in the first place? The derated N1 which you might have set for your takeoff should jump back to the default rating of your engine (which depends on the airline you are flying) after you have reached the CLIMB or CRUISE phase. If you want to apply the go-around thrust manually, simply smash those levers full forward

Might be hypothetical, but e. g. when at very low weights and not obstacle/terrain limited in any way.

 

 

The manual seems pretty clear here.  It's moving to a target airspeed for the current flap position given max weight conditions.  Remember that various aircraft speeds increase with weight (namely, stall).  If it sets the max weight scenario, you'd be safe at all weights with that speed set in there.  There's no need to add additional layers of calculation and complexity by trying to optimize that speed for the current weight.  If you're safe at 180 at MGW, then you'll be safe at 180 at with min fuel, too.

 

The vague manner in which it is described leads me to believe that it's simply a value they've come up with as a safe value (likely calculated as a buffer off of stall speeds in a given config) for recovery from a high drag state.  While I applaud your curiosity, I don't think there's a ton to be gained by figuring out everything that goes into it for the operation of the aircraft.

Say we're light and approach with both engines at ~130, that would yield a ~50 kts "gap" to my MTOW-based flap 15 "target" speed. Of course you're right from the safety point of view.

 

It does, and you quoted it: use the acceleration height.  The reason that it's not specific is - cue my surprise face :lol:  - it changes!  And then we can cue my other normal line of "aviation isn't as rigid as many think!"  Accel height is an AGL value, and it can vary by whatever departure procedure you ascribe to (ICAO NADP, airport specific, operator specific, or otherwise).

Thanks! I was just wondering if there is some sort of "rule", say, use the acceleration height you would have used on a normal takeoff from that runway or so.

 

We fly all of our normal approaches with the A/T engaged to touchdown, A/P on or off.  To go around, press TOGA once and you get enough power to climb around 2000 FPM.  At 400' with both engines operating the F/D will auto bug up for you.  Just stay in the flight director and retract the flaps on schedule.  Works great.

That's very interesting, thanks for the insight! As quoted above (FCTM somewhere...) I would not have expected anyone to do it that way, but good to see it seems to do the job just as well.

 

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The manual seems pretty clear here. It's moving to a target airspeed for the current flap position given max weight conditions. Remember that various aircraft speeds increase with weight (namely, stall). If it sets the max weight scenario, you'd be safe at all weights with that speed set in there. There's no need to add additional layers of calculation and complexity by trying to optimize that speed for the current weight. If you're safe at 180 at MGW, then you'll be safe at 180 at with min fuel, too.

 

The vague manner in which it is described leads me to believe that it's simply a value they've come up with as a safe value (likely calculated as a buffer off of stall speeds in a given config) for recovery from a high drag state. While I applaud your curiosity, I don't think there's a ton to be gained by figuring out everything that goes into it for the operation of the aircraft.

 

 

Not sure what the question/issue is here. The manual is simply stating that, with A/T armed, pressing TO/GA will put it on the G/A limiter as indicated on the EICAS (unless I'm misunderstanding it). My understanding is that, without A/T armed and physically handling the throttles, you have full authority to place the throttles at the full forward stop for max thrust beyond the G/A bug on the EICAS. I could be wrong.

 

TO/GA (no A/T):

-F/D will provide G/A cues

-You have to set thrust manually

 

TO/GA (with A/T):

-F/D will provide G/A cues

-A/T will place the thrust levers on the indicated G/A bug ("reduced" in the manner that it's not max rated thrust as placing the throttles on the forward stops would get you)

 

 

It does, and you quoted it: use the acceleration height. The reason that it's not specific is - cue my surprise face :lol: - it changes! And then we can cue my other normal line of "aviation isn't as rigid as many think!" Accel height is an AGL value, and it can vary by whatever departure procedure you ascribe to (ICAO NADP, airport specific, operator specific, or otherwise). Think about a go around at KSNA here...retracting to flaps up will be delayed to get back up to 3000 first (obviously, safety permitting, though those in SoCal will still complain it was too loud).

 

The reason is says "for training, use [...]" is that the training is meant to cover the G/A in particular, and not distract the training from that goal by trying to also bring in the variables of different departure profiles.

 

If you're curious about departure profiles, in general, so that you have a better idea of accel height for various operations, here's a brochure on NADP:

http://www.b737mrg.net/downloads/b737mrg_noise.pdf

 

Note NADP 1 has you cleaning up and accelerating to flaps up speed (by the flap schedule) at 3000. NADP 2 has you do this beginning at 800.

I'm not sure if this is what you're saying, but I don't think most airlines address NADP1 or -2 in a missed approach scenario. I think most airlines have 2 basic profiles for a missed approach 2 engine or 1.

 

KSNA doesn't get a special missed, either. I'll look at my manuals later to check.

Matt Cee

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I'm not sure if this is what you're saying, but I don't think most airlines address NADP1 or -2 in a missed approach scenario. I think most airlines have 2 basic profiles for a missed approach 2 engine or 1.

KSNA doesn't get a special missed, either. I'll look at my manuals later to check.

 

We only have two profiles, two engine and single engine.  Unless we have a company specific engine out missed approach procedure in the Jepps acceleration height on a single engine approach is 1000' AFL.  We don't have an engine out procedure for KSNA either.

 

I've never heard of the NADP procedures being used for anything other than takeoff.  There is no such thing as a noise abatement go around, at least I've never heard of one.

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I'm not sure if this is what you're saying, but I don't think most airlines address NADP1 or -2 in a missed approach scenario. I think most airlines have 2 basic profiles for a missed approach 2 engine or 1.

 

KSNA doesn't get a special missed, either. I'll look at my manuals later to check.

 

Wasn't what I was saying, though I wasn't particularly clear about it.  The manual offered "acceleration height" and did not specify anything further.  The reason is that the accel height can change.  By its very nature, accel height is defined as part of the departure profile.  In order to illustrate that there are different takes on where accel height should occur, I used standardized departure profiles (NADPs) and specialized (SNA's), because that's how accel height is usually referenced.

 

In the end, as you and Joe noted, company SOPs dictate what you're going to do to recover and set up for another approach.

Kyle Rodgers

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