Anyone run the Flight 1 Piper Merdian?
I have it and want your impressions.

I'm surprised no one else has Meridian.
I bought it because AvSim review gave it 5 stars. The programming reminds me of LOMAC. This a/c will take some time.

Planned to fly from Vero Beach Fl to San Diego Ca.  Surprised when Flight Planner was not accepted into the Meridian.  Not a hint in the website or writeup.  Must flight plan in the Garmin 530.  Can save 13 flight plans.  Garmin messy with knobology.  Can use wheel for entry of route identifiers.  Helps some.  After much screwing around took off for Dallas International GPS.  5 hr flight so quit after half way.  Saved to start next day.  Next day found that the flight plan cannot be saved so programmed Direct present position with Proc for GPS IP to ILS.  No ATC capability or at least I haven't found it.  Not a problem for me as I don't use.   VNAV feature provides a warning for enroute descent to hit the IP waypoint at a specific altitude given constant speed.  Worked well vs way point but didn't compute correctly when MSL altitude was selected second leg.  Important as the range is 1019 nm at fuel sipping 189 lbs per hr turboprop at 30k.  Neat Meggit Magic engine display views.  Several views, one shows fuel at destination (FAD) based on fuel consumption and GS.  I tried power settings and cruise speeds above 145 IAS and under.  Adjusted power and cruise to best FAD.  FAD right on both legs on landing (200 lbs).
 
Other  stuff:  Cockpit switches are three position rocker by mouse.  I still get half of the Garmin mouse commands wrong.  Cockpit pressurization settings are unique.  Two settings on ground.  Field plus 500ft and intended cruise altitude.  Still caused alarm to go off passing 28k.  Finally found the mute switch.  EHSI doesn't display DME with VOR 1/2 needle.  DME in the Garmin map display only.

Meridian looks good and flys well.  Lots of power. Climb to 30k no problem starting 145/1,700 fpm finishing at 135/1,200 fpm. Cockpit is best yet.  But very complex.  Ok for VFR tooling around w/o using GARMIN for casual user.   However, Garmin is central to designed sim operation.  And thats a challange.

4th long range flight and got almost all of the bugs sorted out.
Took about 15 minutes ground idle practicing setting switches esp the Garmin.
Still had the VNAV MSL descent problem.  VNAV allowed setting of waypoint during climbout and everything looked ok.  Mid way in the flight I checked and MSL was back.  So backed out descend to altitude from default 4 nm to 20 nm.  Then descended at 60 miles out from waypoint.  Worked as advertised and I reset back to default 4 mi.  Believe the error is trapped in the Garmin saved flight catalog.  Should be ok subequent flights.
My error in setting ILS one digit off.  System placed a/c in 360 turn at final waypoint till I figured out the error.  Then executed the ILS.
Recommend the a/c for those willing to put up with some frustration learning the Garmin.  Really nice cockpit and nav presentation.

What does the forecast have to do with VNAV?

Are you refering to VSR in COF?
VSR in fps can be converted to fpm for descent.  Clumsy.
Problem with the jets is that the fps is predicated on GS at flight level.  GS changes significantly during descent so the fps and fpm are constantly changing.

I use 3 X altitude/1000.  So at 40k 120 nm descend at 1800 fpm and adjust descent per the VSR.
What do you use?

Meridian does well with VNAV because IAS is 145 and closer to GS of 208 (depends on wind) and max of 30k.  So 1000 fpm with small VS adjustmens to reflect VNAV recommended descent works well.  Works well provided the reference waypoint is displayed correctly.  VNAV display is also fpm which is a direct read to VS.

I'm impressed that anyone would know of the descent  calculations and adjustments in a sim.  I gather that you reference the 737 manual for descent.  Really precise.

Boeing has a manual and the equipment to calculate true density altitude.  Likely that the Captain does his descents by experience or operational requirement.

Altimiters are set 29.92 plus or minus the altimiter error at departure field elevation when ascending or descending FL 180.  So that every aircraft in the high altitude structure is at a consistent reference altitude and not primarily for descent optimization.

Interesting you reference ISA conditions because the Meridian Flt Planning Density Altitude page will accept various inputs including CAS and TAT to give Density Altitude.  Small problem in that there isn't CAS or TAT data.  I used IAS and OAC.  At FL 300 the indicated to adjusted altitude difference was 706 ft.   That would mean about 3 miles for the Meridian.

COF uses standard day temperatures and the adjustment for temp and density altitude is a moot point.  At least thats what I observe regarding temperature.

The VNAV in Meridian has a number of options.  One option is to specify descent to altitude above a waypoint  or select MSL at the waypoint (COF Planner).  Above the waypoint worked fine first leg.  MSL second leg was substantially in error on descend point.  Far too late.  And in the two following flights I was unable to get the system to retain the waypoint option.  It defaulted to MSL.  Don't know why but might be that the flight plan including the MSL option was stored in Garmin and used on the two following flights.

The layout of the Meridian with the Meggitt engine instruments is far superior to the stock COF jets.  It quickly has become very odd in COF to call up GARMIN.

VNAV is useful in Meridian because it is low fuel on long flights and it is difficult to estimate the descend mileage point with reference to the jets because of the speed difference.   From 30k to 8k took 60 nm at 145 plus or minus.  Power is difficult to adjust precisely at low settings and IAS is sensitive to small adjustments.

You certainly are motivated.  Given interest in details you should be successful.  I presume you are working on a license and instrument quals.  Any chance with the airforce?  Great training opportunity.

Meridian has the choice of airfield or waypoint for altitude.  I have been using the ILS IP waypoint for altitude descent reference.  Choice of MSL or above waypoint and can be before or after waypoint in NM.  The designation of IP waypoint is in the Meridian Garmin.  Different from COF Garmin and the destination waypoints are more numerous for a given approach in Meridian.   I'm thinking that the waypoint itself may be part of the problem.  The IP waypoint I used was a VOR station.  Since above the waypoint selection implies terrain height, it may be that the VOR station does not have height information and MSL is the default.  Just a guess.