Mario's freeware Dassault Mercure is finally out!

**Bjoern** · December 17th, 2017, 09:14

What Oliver said.

A stuck autothrottle is a favorite cause for not wanting to slow down enough.
Can't imagine that Mario screwed up the FDE in that regard, seeing that there even are non-standard engine tables.

**Stefano Zibell** · December 17th, 2017, 11:21

Originally Posted by Bjoern

Fourth, I don't think that the autopilot performs as it's supposed to. Airspeed hold hardly works (if at all), NAV/LOC mode more often than not deviates from the set course and snakes around the signal and altitude select mode just nails the vertical speed at +/- 1000 fpm instead of leaving the vertical speed to the pitch or IAS hold modes. Fortunately...

That's a relief, I thought I was just a little too dumb to operate it without reading the manual.

***blanston12*** · December 17th, 2017, 11:53

Originally Posted by Bjoern

What Oliver said.

A stuck autothrottle is a favorite cause for not wanting to slow down enough.
Can't imagine that Mario screwed up the FDE in that regard, seeing that there even are non-standard engine tables.

OK I retract my previous statements. I found the 'Ready to Go' button, and after doing a test flight with zero payload out of PHNL where I went out 20 nm and came back lined up on the ILS beam of 8R but not using auto pilot or auto throttle I made a perfectly normal landing, it must have been a stuck auto-throttle.

**Bjoern** · December 17th, 2017, 13:12

Originally Posted by blanston12

OK I retract my previous statements. I found the 'Ready to Go' button, and after doing a test flight with zero payload out of PHNL where I went out 20 nm and came back lined up on the ILS beam of 8R but not using auto pilot or auto throttle I made a perfectly normal landing, it must have been a stuck auto-throttle.

When landing with autothrottle, you need to make sure that the commanded speed is set to the correct Vref value for your current weight and the desired flap setting. AT and AP are disconnected at minimums (200 ft radar altitude) and you'll land the aircraft manually.
Autoland is available on this aircraft, but again, you'll need to come in at the correct Vref for the aircraft weight and flaps.

Originally Posted by Stefano Zibell

That's a relief, I thought I was just a little too dumb to operate it without reading the manual.

I didn't read it either, but the XML code for the AP clearly shows what is and isn't done.

**Bjoern** · December 20th, 2017, 17:46

Spent a bit of time with the Mercure and managed to cure the abyssimal heading hold.
VOR/LOC hold is quite iffy though and won't manage to stay on a given radial.
Implemented my PID airspeed controller which improves things.
The other vertical modes are still untouched though.

The flight dynamics might cause many of the autopilot issues. No way is a commercial airliner that unstable in even a slight breeze.

**Bjoern** · December 21st, 2017, 03:09

Calmed the aircraft down by brute force ( roll_stability = 2.0 ) and with a dead centered CDI needle, the aircaft will now fly to/from a VOR without going left and right of the signal.

Next stop: Adding a mach hold mode to the ALT SEL mode since pure IAS hold wouldn't make sense in the higher flight levels. And fixing ALT SEL mode.

I also did a bit of rough number juggling again regarding available range. A Mercure goes as far as a DC-9-50, but not as far as a standard 737-200 (the Advanced model goes much farther).

**mgchrist5** · December 22nd, 2017, 05:51

Calmed the aircraft down by brute force ( roll_stability = 2.0 ) and with a dead centered CDI needle, the aircaft will now fly to/from a VOR without going left and right of the signal.

That calmed down the NAV hunting on mine. Thanks for the tip.

**Bjoern** · December 22nd, 2017, 09:12

Can you also test the auto approach/autoland behavior with that fix? I'm a bit too holed up in other things to do this.

**mgchrist5** · December 22nd, 2017, 10:55

Can you also test the auto approach/autoland behavior with that fix?

It appears to work pretty well. Apologies beforehand if the following is too verbose. Just trying to give as much detail as possible in case someone else has different results:

I flew four ILS approaches to autoland using the stock FSX Philadelphia KPHL 27R - winds 0. Two of them at 109,000lb (just below max landing weight) and two at 97,000lb. Two were straight-in intercepts from about 15nm out & 3,000ft, the other two were 30 degree intercepts also at 15nm & 3,000ft.

In all scenarios the plane was stabilized with flaps 7 - autothrottle 180 KIAS and autopilot ALT hold prior to attempting to intercept the localizer. Playing it safe with plenty of room. Once the localizer came alive, I armed ILS approach mode. Regardless of whether it was straight-in or 30 degree intercept, the plane still hunted a bit as it tried to capture the localizer (maybe +/- 7 degrees), but it wasn't as aggressive as previously, and it stabilized completely by around 6-8nm from touchdown. Glideslope capture was fine. Flaps/gear were deployed on schedule - flaps 25 max for autoland according to Mario's notes - and autoland armed. In each scenario it performed an embarrassingly nice autolanding.

Other people's mileage may vary depending on weather, etc but using the general scenarios above the approach/autoland is much less mercurial (!) than before. The other AP vertical modes (IAS & VS) are still wonky, but that's for another day. Still a fantastic plane with plenty of potential. Thanks.

**Mariopilot** · December 22nd, 2017, 14:04

Just look who pops in here!
Thanks all for the kind comments! Very much appreciated!

I'll try and clarify some of the autopilot woes here:

IAS Hold: this is NOT auto-throttle! it will hold on speed by altering throttle. may oscillate around if given an untrimmed aircraft. generally dampens out. Does NOT enjoy gusty winds or sudden changes of throttle.
NAV VOR mode: tends to oscillate around a bit as the PIDs were tuned fro auto-land precision...
A/THR is up to 250 KIAS and meant for auto-approach use only. You will have to manage thrust manually!
ALT SEL mode does not do anything for pitch. you can add to it any other vertical mode until it "engages" 300 ft prior to target altitude. Generally you will:
-set climb power according to tables
-climb slowly on basic mode until desired speed (250KIAS below 10K ft, then accelerate to 300 KIAS). "basic mode", eg AP engaged but no MCP vertical mode added, equals "ATT hold".
-engage IAS, without altering throttle.
-engage AT SEL (could have been done before)
-within 300 ft of target altitude, any vertical mode will disengage (IAS mainly) and shortly after ALT SEL will switch to ALT HLD.

in basic pitch mode, the aircraft is in attitude hold to alter pitch, use pitch wheel in AP panel OR FS trim controls (yes, joystick buttons will do).

Not able to slow down? it is a somewhat low-drag aircraft. you may need to level off with idle thrust. once flaps or gear is out, no big issue!

The "less stable" behavior is the result of "realistic" aero derivatives in the flight model. The aircraft feels a lot more "mushy" than standard FS stuff because of this. Indeed the Fs AP struggles a bit with this.... all aero parameters were computed with standard aero engineering methods...

Any other questions feel fre to ask. Keep in mind that "official support" for this aircraft is over at HJG forums, where I will respond your queries as weel, an likely more quickly

Cheers,

Mario

**BendyFlyer** · December 22nd, 2017, 22:16

One quick comment for those who like the detail on some things, on any high performance jet or turboprop or piston - WITH NO SPEEDBRAKES OR SPOILERS, the standard technique was to plan for a short level segment on descent at about every 10,000 ft to let the aircraft slow down to the next speed step. This can take up to 30 secs or more dependant on the drag/airfoil configuration. Hope this helps.

**Bjoern** · December 23rd, 2017, 10:12

Originally Posted by mgchrist5

...

Thanks for the report! Saved me a bit of testing.

Originally Posted by Mariopilot

Any other questions feel fre to ask. Keep in mind that "official support" for this aircraft is over at HJG forums, where I will respond your queries as weel, an likely more quickly

That's good to know. Wanted to post there anyway once I got something drawn up for the AP.

**Bjoern** · December 24th, 2017, 07:27

Poured more work and test flying into the bird. ALT Select and ALT Hold are now working as they're supposed to.
Had to upgauge the pitch_stability to 2.0 for ALT Hold though since the aircraft started to oscillate at low weights.

Reversion to ATT/HDG hold also works much better. Without any specific AP mode set, it will fall back to these (HDG Hold only conmtrollable from turn knob, otherwise HDG Preselect is required).
ATT Hold, in conjunction with the speed brakes, is useful for slowing down during descents.
And speed brakes may now be controlled with the keyboard (in 5% increments).

The "F/S" indicator on the ADI will now display deviation from target speed/mach or acceleration. The latter is useful for trimming the throttle for a certain speed when in ALT Hold mode.

Still need to fix the altitude selector display. No matter what I do and how often I check the underlying code, it is always off by 100 feet.

The fuel logic also needs a minor improvement. So far, all tanks will be used when all pumps are running. For drawing from center only, the wing tank pumps need to be switched off.
But at least in all aircraft of similar tank configuration (737, A320, DC-9, etc.), the center tank pumps deliver more pressure than the wing tank pumps and combined with check valves, this ensures that center tank fuel is consumed first when the tank is full and the pumps are running. The status of the wing tank pumps doesn't matter for that to happen.
I'd be very, very surprised if the designers of the Mercure did it any differently.

P.S:
I've also tried the autoland functionality. Worked like a charm and the test sequence after switching it on looks pretty damn cool!

**Josh Patterson** · December 24th, 2017, 08:34

Been having a bit of fun hand flying this around. The only problem I've had with the systems I've used is getting the engines to start. When I mouse over the starter switches on the overhead, they are acknowledged as my pointer goes from arrow to the hand, but I can't do anything with them. I have to start the engines with a keyboard command. Is this a bug, or did I just miss something?

**Josh Patterson** · December 24th, 2017, 09:13

Originally Posted by Josh Patterson

Been having a bit of fun hand flying this around. The only problem I've had with the systems I've used is getting the engines to start. When I mouse over the starter switches on the overhead, they are acknowledged as my pointer goes from arrow to the hand, but I can't do anything with them. I have to start the engines with a keyboard command. Is this a bug, or did I just miss something?

Nevermind, I got it. Just had to get the bird to a cold and dark state. Everything works great when starting fresh! Would love to see a Caravelle this good!

**Bjoern** · December 26th, 2017, 15:34

The dynamic checklists also help.

**vonstroheim** · December 28th, 2017, 19:12

This is really a lovely aircraft. It deserves more screenshots.... Here's one:

***Jafo*** · December 29th, 2017, 04:13

Is there a paint kit? ...

**Bjoern** · December 29th, 2017, 07:12

Finished the fuel system. It's more in line with the behaviour exhibited on similar aircraft now.
Also revised the starter logic since in-flight starts didn't really work for me.
As a gag, the APU now requires and consumes fuel.

And thinking about implementing an aircraft manager for fuel, payload and panel load/save.

I've also talked to Mario about the mods. He's going to look at them and maybe implement them into a possible update. Good riddance!

Originally Posted by Jafo

Is there a paint kit? ...

Funny you mention that, as I've just asked Mario about one today.
According to him, there's a paintkit, but he's is on holidays for now and can't dig it out. He's going to send it over or upload it once he gets back.

A prime candidate for a what-if livery is Eastern, since they were interested but were committed to the DC-9-50 instead.
Or how about all the regional carriers from back when. PSA, Hughes, Southwest, maybe even Frontier. Or virtually any west-central european carrier for the other side of the pond. Lufthansa, SAS, Swissair, Austrian. Japan might also work.

**Stefano Zibell** · July 21st, 2019, 17:43

Sorry to bring this back but since last December there has been an update that addresses many things discussed here. It's surely a permanent dweller of my hangar now.