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Entering VNAV speeds in the CDU

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Hi there,When i try to enter my own vnav clb speeds, it wont allow me, saying my inputs are invalid, this is when i try to enter a ias and a mach together using the format xxx/.xx however it will allow either an ias entry or a mach entry. is this an issue or was it designed this way?? If the latter why?? is it like that in the RW, and why can it be done in other payware addons??Another thing is when i was on short final i disconnected the AP, thus showing a red EICAS msg saying autopilot disc (i think) anyway, once on the ground, i could not cancel that red msg no matter what i tried.ThanksJason

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Jason,The reason you can't enter both numbers is that during a climb the mach number changes constantly based on the altitude density i.e. at FL200 an airspeed giving Mach .56 is going to increase to give around Mach .75 at FL300.You do know that you are supposed to cancel ALL warning messages when they occur if they are MANUAL EVENTS i.e. you did them?

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Ok, i understand, but the purpose of the two numbers is as is with the default cost index figures, so you will fly ias to until the mach number desired is reached and from then it is flown on the mach number. ie. i want to do a 320/.840 climb not a 310/.82 climb. It seems a little silly to muck about with the cost index until you get it right.With ref to the AP, i disconnected at about a mile final, once landing roll complete, i re-engaged the AP bar and tried to cancel the alert, was the time difference too long??Jason

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You dial in a CLIMB NUMBER in IAS you dont try to climb at mach.......... the computer just tells you what the number is based on current density altitude. As far as the AP yes in a normal cockpit when a manual event takes place the PNF ( Pilot Not Flying ) would cancel all alarms after they are noted.

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Ok, but in the RW all aircraft climb and crz at a mach number above a certain level.Jason

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Ok, now, how does the FMC work out an accurate TOD point if you cant put the 2 speeds into the CDU. On the VNAV des page when approacing Dubai it was giving a default of .73/273, so thats what TOD point is caculated with is it not. I want to descend at .84/320, now if you cant put those two speeds in, how is the TOD point caculated, if you just put in .84 it should calc .84 all the way down to 10000 feet which would have you doing about 400kts ias at some stage. If you enter just 320, then its going to accellerate to close to mach 1 in the initial part of the descent.Am i being dumb?????????Jason

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Jason,You can climb or descend on one figure or the other. Both figures are not the same at different levels.Ie you can decend on a mach number or a speed.

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Hi,In the real world you can put ias/mach in the VNAV page. works on CLB and DES page. VNAV will fly the IAS till it gets to the MACH nr and vice versa in the descent.Autopilot Master Warning:The first press of the Autopilot disconnect switch on the control column disconnects the AP. the second press:-Resets the master warning lts-Resets EICAS warning msg-Resets the aural warning.Cheers Sjaako

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Thanks Sjaako,What would happen if just entered one speed in the RW, if you just put in an IAS in the CLB then you would have to manually change it to mach when you reached your desired mach speed. I thought one of the benefiting factors of an FMC was to automate things a lot more so when you're are on the GND you can select your climb profile and not have to interfere all the way to the CRZ.Jason

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> I thought one of the benefiting factors of an FMC was to>automate things a lot more This was my basic understanding too. Im as interested as you now Jason.

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Hi Guys,If you enter just an IAS it will accept it but fly the IAS all the way to TOC (CLB example). Which means it would start to overspeed when the Mach nrs become more limiting. For instance at FL370 the Mach nr is .84 the IAS is somewhere round 270kts. so if you would climb with constant IAS in the VNAV clb page i.e. 300kts it would overspeed at some point before FL370.You have the option to alter the speeds but don't have to. Econ speeds also work but when flying cost index 0 it gives around 250kts descent speed. This is when most people put in .84/300kts or anything along those lines.If you change a CLB page speed/mach nr. it only changes the CLB speed CRZ and DES remain unaltered.Cheers Sjaako

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Thanks SjaakoSo what you are saying, which is what i believe to be correct, is the real world procedure if you were overiding your cost index econ speed is to enter two values, an IAS and a Mach. Likewise with the DES.Normanany comments on the findings of my flight with ref to some of those issues?Jason

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Normally speaking YES.Unless you fly a very short sector i.e. FL100 then you would not use mach nr's.So 99% of the time I enter IAS/Mach nr. in CLB and DESand Mach nr in the CRZ page. (In the CRZ page you can enter IAS OR Mach nr.) not both.Cheers guysSjaako

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Thanks SjaakoThat is exectly what i understood to be real, thats why i was so confused when i was faced with this limitation.PSS, something to look at!!!!Jason

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Interestingly, the 777 manual that I have access to (see below) clearly shows that user inputs to VNAV CLB or DES pages are limited to either CAS or Mach - not both. On the CLB page either CAS or Mach is shown (on LSK L2), but on the DES page both values are shown.It seems that the diplay of either CAS or Mach on the CLB page is governed by an entry in the airline policy file, so I wonder if the whole issue could be airline option dependent?Anyway, below are extracts from the relevant parts of the manual-------------------------------------------------------------------VNAV CLB pagePage TitleThe page title shows the type of climb.

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And then it goes on saying:The FMC commanded speed is in magenta. Below CAS/Mach transition altitude, CAS is magenta and Mach is white. Above CAS/Mach transition altitude, Mach is magenta and CAS is white.So this would mean both values are displayed leading me to believe you can change them both ie CAS/Mach entry.CheerioSjaako

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Hi,Just had a look at the Cathay 777 video. This shows the VNAV CLB page with both numbers ie. CAS/Mach.Maybe it is airline specific.Can't tell you more till I get my hands on the real deal Friday.Cheerio

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>And then it goes on saying:>>The FMC commanded speed is in magenta. Below CAS/Mach>transition altitude, CAS is magenta and Mach is white. Above>CAS/Mach transition altitude, Mach is magenta and CAS is>white.>>So this would mean both values are displayed leading me to>believe you can change them both ie CAS/Mach entry.>Sjaako,You're right, I didn't cut'n'paste the last bits, but they are indeed as you described above. That being said, the Cathay video (which I don't have) definitely does not correlate with the information from my Continental Manual.I'll see if I can find some stuff on airliners.net Found this one: http://www.airliners.net/open.file/0238090/L/Difficult to read but it seems that the captain is on ACT ECON CLB and there are indeed 2 values indicated, I guess its magenta CAS and white Mach in this case. Let us know after Friday.Cheers,S

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Hi,Well just got back and the story goes as follows:All 3 entry methods worked i.e.-CAS-Mach-CAS/MachThe only thing different from other boeing aircraft I've flown is that when you enter just an CAS OR Mach, it only shows that one number. Cheerio,Sjaako

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Thanks for all the research there. Can this maybe added to the list of bugs/fixes for the patch. it would be nice to have as close to life as possible.Jason

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I have noticed the AP disconnect problem as well. In the real A/C, you click the AP Disconnect button twice on the yoke and it cancels all EICAS messages and aural warnings related to the disconnect. Is this just an error in the PSS software that we are unable to cancel them out? It doesnt bother me at all, its just sort of odd.In reference to the VNAV climb speeds, I had a discussion with my dad about it since hes a 777 FO for COA. I asked him if it was possible to change the VNAV speeds on the climb page. He said you could, but he doesnt understand why you would want to. He said that if you needed to change your climb speed, which is mainly due to ATC instructions, you would just do it in the airspeed window on the CDU. Otherwise, the VNAV speeds are calculated by the cost index you put in during preflight. So I guess my conclusion would be if you needed to increase/decrease your speed during climb, take the A/C out of VNAV and put the desired speed in the CDU window, then click Flight Level Change or FLCH. It is my understanding however, that pilots rarely use FLCH or VS (vertical speed). I hope this answers your question.Brian

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Hi,Well as you said in the climb it is not all that usefull, in the descent however all the more. This is where it is used most in real life. Also when you update your descent speed it will give you new vertical profile information. This comes in usefull when on an atc resriction and you fly in FLCH or V/S.You can fly in VNAV as a vertical mode and open the MCP SPEED WINDOW. this will allow you to directly control the speed to your liking.I use V/S all the time.... Today there is so much traffic it really helps to use V/S when you approach your cleared level and try not to scare the guy/girl 1000ft above/below you with a TCAS RA.Also a very valid reason to change your climb speed is turbulence, but this is mainly done through the MCP window.CheerioSjaako

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heheh, an old and bold 747 pilot told me never to trust the flch. In the real a/c he said (NWA) it to wild, he always used the V/S for climbs and decends.I think.. just think.. that we want it to be to perfect, while the real one isnt also.JohanPS: nothing todo with the speeds.. btw..A LITTLE LESS CONVERSATION, AND A LITTLE MORE ACTION PLEASE!HELP:http://support.microsoft.com/?kbid=238882

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