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Michael Moe

speedtape Question

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Hi,

Its bin a while flying this old bird and i still love and enjoy her so much :-) 

I am on a flying to Helsinki and notice my speedtape with this yellow over/under my crz speed and wondering what this very narrow window actually meens ?

Its more common on approach and landing to understand but in CRZ ?

Thanks for learning to fly :-)

https://imgur.com/a/HJqnvgC

Michael Moe


Michael Moe

 

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Maximum maneuvering speed. Fly into the amber bar, and you have reduced maneuver capability. Should be in the FCOM somewhere. Can't really help you figure out where since I don't own the NGX, I'm just using the FCOM from the 747-400 to pull this up.


Captain Kevin

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Air Kevin 124 heavy, wind calm, runway 4 left, cleared for take-off.

Live streams of my flights here.

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33 minutes ago, Michael Moe said:

Hi,

Its bin a while flying this old bird and i still love and enjoy her so much 🙂

I am on a flying to Helsinki and notice my speedtape with this yellow over/under my crz speed and wondering what this very narrow window actually meens ?

Its more common on approach and landing to understand but in CRZ ?

Thanks for learning to fly 🙂

https://imgur.com/a/HJqnvgC

Michael Moe

Michael, every symbol and message on every display is defined in the FCOM.  Sure, there's lots of pages but it's easy to find anything if you follow a few simple steps.  First open FCOM v1 and the Table of Contents for both volumes is up front, find the chapter on flight displays to be Ch 10.... open FCOM to beginning of Ch 10 and find the Chapter Table of Contents and the PFD speed indications starts on 10.11.6. 

You'll find your specific answer on page 10.11.8.  Index items 5 and 7 are minimum and maximum maneuver speeds.

Finding the answer this way is much quicker than posting on the forum and waiting for a response.

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Dan Downs KCRP

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Maybe too heavy to fly at that altitude?


Romain Roux

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Avec l'avion, nous avons inventé la ligne droite.

St Exupéry, Terre des hommes.

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That's some narrow envelope!  I don't think I've never seen it that tight.  I flew at FL400 last night and the FMC calculated max FL380, but I still burned enough to get up there and have a decent envelope.


- Chris Jefferies

 

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You‘re close to the coffin corner... fly faster and you may damage your structure, fly slower and you may stall. That‘s actually the limitation of the cruise altitude and I bet you are way over the max flightlevel adviced by the FMC. 😄

it‘s a simulator, I guess you‘re fine learning that way but the manuals are really interesting to read about. 


,

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Ahh thanks everyone. FL390 might be to much with that weight but PFPX gave me this altitude at that position. 

Thanks again 

Michael Moe 

 

 

 

 


Michael Moe

 

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6 hours ago, Michael Moe said:

Ahh thanks everyone. FL390 might be to much with that weight but PFPX gave me this altitude at that position. 

Thanks again 

Michael Moe 

 

 

 

 

Don't use PFPX flight plan as anything but a plan that you deviate from as warranted by conditions.  Perhaps your SAT is higher than forecast.  Stick to the altitudes available to you in the FMS.

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Dan Downs KCRP

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7 hours ago, Michael Moe said:

Ahh thanks everyone. FL390 might be to much with that weight but PFPX gave me this altitude at that position.

I read the altitudes from PFPX and often wonder where it even gets its calculations from. I just stick with the FMC.


Captain Kevin

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Air Kevin 124 heavy, wind calm, runway 4 left, cleared for take-off.

Live streams of my flights here.

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Thanks , now this pilot to pilot conversation is hard to find in the FCOM right ? 😉

Thanks for all of your answers and hopefully you will stick to my "plan" regarding sharing knowledge ? 😃

Love you all 

 

Michael Moe


Michael Moe

 

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I can nothing but second Kevin‘s advice. The FCOM and FCTM are actual Boeing manual and if they aren‘t perfect to study, what else? But if one needs help from experienced pilots, there are many of them here type rated on the models we have and there‘s always something to learn when they jump in. 


,

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19 hours ago, Ephedrin said:

I can nothing but second Kevin‘s advice. The FCOM and FCTM are actual Boeing manual and if they aren‘t perfect to study, what else? But if one needs help from experienced pilots, there are many of them here type rated on the models we have and there‘s always something to learn when they jump in. 

Thanks , its just harder to "just" read the FCOM and FCTM without actually getting a real pilot education.

I feel i need the dialog with people and gladly you guys fill in. 😉

its stil a hobby for me.

I do use the FCOMS but must admit that a Pilot instructor (like Blackbox711)with video - learning the systems and how they interact with each-other is more "interesting " for me 😉 But i agree with you.

(and airline2sim offcause - great series btw)

Thanks Michael Moe

Edited by Michael Moe
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Michael Moe

 

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As stated, they're both maneuver margins.  The bottom of the upper amber band is where the SMYD computers and FMCs calculate high - speed (mach) buffet will begin under a 1.3g loading.

Likewise, the top of the bottom amber bar is the speed the computers calculate that low - speed buffet will begin under a 1.3g loading. 

The takeaway is that you're flying too high.  The cruise page of the FMC shows you two altitudes - optimum and maximum.  You can treat the maximum altitude as theoretical - no one flies there.  You would have almost no window at all. 

Stick closer to optimum altitude.  Interestingly, not only is there a safety disadvantage to flying higher than optimum, you aren't doing anything useful for your operation anyway.  You'll actually burn more fuel if you operate above optimum altitude, and the penalty increases quickly.  I remember a stat along the lines of: flying one thousand feet above optimum altitude is an equal fuel penalty to flying around three thousand feet below it. 


Andrew Crowley

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Exactly as above! Fuel burn is about constant also at speeds between ECON and LRC. faster or slower than this burns more fuel as well as near Optimum altitude.

One mistake folk can make is to out climb bad weather  in a swept wing jet transport. Above Optimum, you lose margin. don't do it- far safer to go round the weather!

One other point. In your performance page, you entered the cruize MAC percentage. Often this defaults to 5%. If you change this to 25%, those yellow bars and your maximum alt will change too. That's where the FMC is getting the reference from!

My last company always tried to trim the aircraft aft, as you reached TOC you'd have used up most of the centre tank anyway, so reaching about 28% there was perfect and we could leave the Turkish border heading to maybe western Germany at FL400.

My present company I return to UK from Turkey and can barely get to FL360 by Ederne. They trim far more conservatively. FL380 comes by eastern Germany.

Loads, weights, temperature and trim all play a part.


Mark Jason Harris.

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