Another FMC question

hi everyone,

 

i am trying to install an fmc into some freeware aircraft (defaults and non-defaults).

lets take the bendix/king honeywell fmc, one of the most popular.

 

if i use this device by adding it as a new gauge, how can it control my vertical navigation?

because no aircraft has a "vnav button" on the autopilot. and the fmc add on comes plain,

without any help on this.

 

has anyone done something like this before?

couldnt find a video on this, all fmc (ok most) tutorials are based on pmdg etc.

 

thanks in advance for your help...

(actually can't wait for your answers)

 

erol

Dunno.. The only add on FMC I've tried was the one that commonly in the

"hot files" section.. And I think it can do a pseudo version of VNAV.. But it was

so alien in operation compared to what I'm used to on the Boeing's, I didn't mess

with it a whole lot. I was trying to use it on the FSX Lear 45 as I recall..

So I think it can sort of be done with it, but it's not really like what I'm used to,

and I can't give too much advise on how to use it, unless I messed with it more

myself. Is the one you are talking about a pay ware FMC? Must be, cuz I don't

really recollect that free one as duplicating any particular model. I think it was

like a generic FMC if I remember right.. ??

the one you are thinking of (I think) is the freeware Honeywell FMC avaliable here, yes?

honeywellfmc.zip?

I believe that one, while nice, is nothing but a glorified GPS. It has simple autopilot built in. I dont remember much about it, but there WAS a manual with it.

If I remember correctly, the free Honeywell FMC is intended for general aviation, doesn't allow input of mach speeds. Isn't that why it's named Bendix King General Aviation Flight Management Computer System? I've never quite understood why so many jetliner modelers include it in their panels. Better than nothing, I suppose.

I dont know for sure about which particular FMC you are referring to. I use the iSG FMC which has full VNAV control. But the your more than likely going to have a simple VNAV advisory and not full autopilot VNAV control.

the one you are thinking of (I think) is the freeware Honeywell FMC avaliable here, yes?

honeywellfmc.zip?

I believe that one, while nice, is nothing but a glorified GPS. It has simple autopilot built in. I dont remember much about it, but there WAS a manual with it.

 

It may be the same one. But the zip was fmc-1.zip.. But the cab file is

HoneywellFMC.CAB . So may well be the same one.

I didn't spend too much time messing with it. Also, I think I was wanting it more for

LNAV, rather than VNAV, but it claimed to do both.. Sorta.. I remember when I tried it

on the Lear 45, it was kind of clunky to use, and wasn't like the one on the Boeing's

too much. And it kept doing something that I didn't like, but I forgot what it was now,

it's been so long...

And it might not have been able to use mach speeds now that I remember. But I could

have lived with that most likely.

Also, the default FSX jets all have a IAS/Mach speed problem inherent in the autopilot,

which I believe was a bug carried over from FS9. So that bug might cause problems using

VNAV planned mach speeds. It might work, but you would have to keep resetting it as

you climbed.

Once level and reset, it would be OK, but then you have to go through the same back

and forth resetting until back to using IAS speeds for the rest of the descent.

ok, i kind of sorted out myself.

here is the thing:

generic fmc's don't need a VNAV button.

once you are airborne, you switch to your NAV/GPS button to GPS, and tell the autopilot to follow the NAV. in this case the FMC unit feeds the autopilot both with lateral and vertical info. not very realistic, isn't it?

if you have an autothrottle you turn it on and even the speed info comes from the FMC.

 

the only exception is ISG package, which asks you to insert a VNAV button somewhere, but i don't think i will buy this package because the only tutorial i found is how to install the gauges. there is none about a tutorial flight. maybe they give you one, once you purchase the product, but i dont think i like to risk. i will post to their forum anyway.

 

rwgards,

erol

The reason you need to install the VNAV button is because its the only way to get realistic true VNAV. Using the FMC is easy peasy and will teach you future more sophisticated addons.

My only problem with the Garrett Smith FMC is that when you go to calc VNAV it keeps putting Ground Speed along the entire route instead of IAS. So what happens when you activate it? It uses that number to auto adjust your AP when your AP is looking for IAS.

 

Example: I was flying my A380 at .85 Mach and was already at cruise alt FL390. I entered my cruise alt (39000) into VNAV and hit Calc. It showed 510/39000 at each Cruise Alt waypoint. So each time I passed the next waypoint it auto set my Mach setting to over 1.15! (which would be the correct Mach number if 510 was IAS). I would be overspeed before I even realized it and would have to quickly disengage the AT, reduce throttle, set it again, and re-engage it. It's definitely a PITA (Pain It The...)

 

So I had to manually edit each and every waypoint in the VNAV to read 270/39000 (which is .85 Mach at that Alt) in the VNAV and Activate and it worked fine after that. But why should you have to do that? I gave up and have come to the conclusion that I cannot use VNAV. :(

 

I already know that the FS flight planner has it's bugs. If you click on NavLog it shows ground speed settings along the route instead of IAS. Obviously that is the problem.

 

Does anyone know of a fix to this so that the Honeywell FMC imports the speeds properly?

I tried it, as I wanted to use it for the FSX Lear 45, but it wasn't quite what I

had in mind, being as I'm used to the PMDG 737 FMC, which is pretty realistic.

I had similar issues with the speeds, etc, and finally came to the conclusion it

wasn't gonna work out too well. Don't think it's really catered to jets too much.

So.. I mothballed the Lear, and stick to the 737. I can run the 600 into fairly small

runways if I want to get off the usual trail.

 

There is also a bug with the IAS/mach speed with all the FSX default jets as far as being

on autopilot and climbing or descending using mach speed. You have to constantly reset

them IAS/mach if you want it to read right and hold the right speed.

Thankfully, I don't see that with the 737NGX. :)

 

BTW... that bug was in FS9 too, and carried over to FSX. :confused:

Hi Warthog,

 

I sort of solved this problem by changing an Aircraft.cfg entry in the [Reference Speeds] section. I changed the "cruise speed" to 340.00. This fixes the FMC calculations for VNAV and stops the constant overspeed at each waypoint.

 

Remember to save the Aircraft.cfg file (by another name eg Aircraftold.cfg) before you change the entry.

 

Hope this helps.

 

Regards

 

Algenon