In the PERF init. page the numbers /.3M/.5M/ are mach speeds. You should have 3 numbers in the following format Airspeed/mach/decent angle, I believe in that order.
These are the default airspeeds (I'll get to the decent angle later) that the FMS will use for planning i.e. before you take off and for speed restraints if using the 4 axis autopilot. I'll assume by your post that you know how these numbers effect the planning. As as helicopter pilot mach speed are rarely something that we have to worry about. Therefore to get rid of you should be able to delete it directly from the PERFinit page. It should then read 140/-./3.0. If you ever do want to impose a Mach speed comand you can do this by entering it into the flight plan adjacent to you waypoint. For example if you wanted to arrive at your waypoint at 500 feet decending at MACH0.5 you would enter 0.5/500 into the stratchpad and press the RIGHT line select key across from your waypoint, and the FMS would display the following 0.5M/500 any value over 1 but less than 6 will be displayed as degrees. If you enter 140 say, it will be displayed as an airspeed.
This takes us nicely onto VPATH and decent angles. This is something I use everday its fantastic and manages to keep me awake on the long legs lol.
If you look at your flight plan you will see your waypoints entered on the left hand side of the screen with distances, courses and ETE (ETA if you are in flight or have set a ETD while on the ground). On the right side of the screen you have the blue or "Cyan" if you like that word better figures ----/--- etc. Anytime you see blue figures they are displaying one of 3 things, Vertical Nav info, Performance info or Atmospheric data. In this case on your flight plan page these figures are VNAV information.
I'll run through an example of how we would use this and it may make more sense.
Say for instance we where on a flight from A to B. We are going to cruise at an altitude of say 5000 feet. Therefore we enter 5000 feet cruise alt when doing our PERF init. You then go through the rest of the PERF init and confirm the init when done, as normal. 3 things are required in order to recieve VNAV or VPATH data. The performance Init. confirmed is one (be aware that you have to re-init. every time you land or have WOW). The altitude select knob set to the appropriate value is the next thing required and finally a value must be set in the VNAV info portion of the flight plan (i.e. the "Cyan or Blue" ---/---) on the right side of the flight plan.
Therfore we now have 5000 feet in our PERF INIT and confirmed. Our altitude select should be set to 5000 (displayed in BLUE above altimeter) and now we are going to enter a value in the VNAV portion of the flightplan. In this case we are going to decend on a 2 degree angle from 5000 feet to arrive at our destination (point B) at 300 feet. We enter 2.0/300 into the stratchpad and then press the "RIGHT" line select key, probabaly "R2" adjacent to "point B" in our flight plan. The FMS will now display:
POINT B 2.0/500.(Cyan)
you may then see a rate of decent displayed above this. If you now look at your MAP page on your MFD at your flight plan you will see 2 small diamond shapes apear on your flight plan. One should be labeled "TOC" and the other "TOD", these are top of climb and top of decent respectivley.
Now you take off and start the flight, the top of climb should display where the FMS estimates you will reach your cruise altitude (or well you will reach it using the 4th axis climbing at 120 (or whatever value you set in the PERF INIT Page). When you have reached cruise flight and are nearing your "TOD" top of decent you will see a message displayed on the FMS, it should say "RESET ALTITUDE SELECT". This is prompting you to reset your altitude select knob to a lower value as the FMS will not decend below whatever this is set to. You should now reset this altitude select value to 300, or whatever altitude you plan to level out at. At around the same time you should see a VPATH profile bar appear where the glide slope would usually be. If you go to the PROGRESS page 2 you can get information like rate of decent required to maintain the glide slope, and lots of other great VNAV info.
Now I don't know if you know all this already, so my apologies for going over the basic stuff if you do.
Anyway, that was a very basic example of a flight from point A to B using VPATH profiles. However you can see the implications for other uses. For instance when shooting approaches. Now you can have a glide slpoe on your VOR/NDB/GPS approaches. Its also great for approaches where you have many step down fixes as it will give you glide slope that will take you through each one of these altitude restrictions. So its like shooting an ILS all the way down from cruise altiude through many altitude restrictions and turns all the way down to your landing area. This is something that I use a lot as we do a lot of point in space GPS approaches with step down fixes.
As for the groundspeed make sure you have GS/FF selected in the PERF INIT page.
Anyway mate hope this helps let me know if I can help with anything else.
Last edited by platinumpure; 20th Jun 2007 at 01:31.