Hello everybody.

Does anybody else has this strange behavior with the Maddog in FSX. This happens ONLY in FSX for me since 2008 edition.

Here's the scenario...
Right after TO, after selection of a lateral mode (NAV or HDG SEL), I engage IAS mode...
Then I want want to accelerate from initial CLB speeds (130-140kts) to 210-250 kts for instance and I dial the speed in the appropriate flight guidance window.

Here's what the FSX Maddog does :
- It lower its nose to accelerate to the commanded speed. No problem with lowering the nose to accelerate... BUT!! The problem is that attitude goes into negative (AND)
- Then of course, VSI goes into negative values too...
So I found myself with a Maddog DIVING to gain speed not long after TO in IAS climb.
- And only after it has reached the speed it climbs again...
- Of course, during the ALL scenario Autothrottle is steady at "CLB EPR".

Only one word can describe this behavior : UGLY as ######.

Anybody else with this behavior in IAS mode???
Davide, did you ever encounter this one in beta???

Fritz try this, this is how two airlines did/do it in the climb:

Airline 1. At 1,000 AGL roll the V/S wheel to 1200, select the top bug, clean maneuvering, or 250 knots on speed that means selecting the top bug value or 250, clean up on schedule and select Climb Power after you bring the flaps up, then at 250 or top bug select IAS at 10,000 select V/S again and roll to 1200 and select 290 allow the plane to accelerate then select VNAV or Perf. the alternate way is Climb Power at 1,000 AGL and half rate, 1200 fpm V/S and speed top bug or 250 at 3,000 AGL. Minimum alt for a roll mode selection is 400 AGL.

Airline 2. 1,000 AGL Climb power manually pitch down to 10 degrees ANU retract flaps at the FR bug then select VNAV/Perf and retract slats at the SR bug. Alt way is Climb Power at 1,500 AGL and the rest at 3,000 AGL.

Thanks for the climb profiles Jared. I will try and operate the Maddog with those ones...
As the IAS mode is broken for me anyway. I have NO choice.

Good Luck, just remember that the IAS mode holds the speed with pitch only so it will pitch up or down to maintain the selected speed.

Yeah, I perfectly know that... Don't worry. I know how it works I think...
But the behavior is just WRONG. It should behave like my FS9 version/like the real one :
With the dialed Altitude is higher than the present altitude, the autopilot "understand it's a climb.
So... instead of diving to gain speed it SHOULD LEVEL OFF... then slowly climb again...

It's a bug/a mistake... Call it what you want...

Fritz,

My FS9 does this as well, but using the profile mentioned above works great (and it's r/w procedure). I'm not necessarily sure the real thing is smart enough in this regard either, hence the above procedures rather than climbing in VNAV or IAS initially.

Anyone with r/w experience that can provide feedback?

The real airplane will not, under any circumstance, put the aircraft in a descent to accelerate if the selected altitude is higher than the aircraft's current altitude. Likewise, the airplane will never enter a climb to decelerate if the selected altitude is lower than the aircraft's current altitude. There are no fundamental differences to the logic or behavior of IAS/Mach hold between MD8X/9X and LVL CHG/FL CHG in any other aircraft - it works exactly the same as 737, 757, etc. Meaning, the logic aims for a specific rate of acceleration, and that's exactly why the rate of climb, during acceleration, will vary depending on the load; higher rates of climb when the aircraft is light, lower rates of climb when the aircraft is heavy. Exactly WHAT that rate of acceleration equates to is not something they teach you. But it will never be less than a level-off during climb and that's only in extreme situations (MTOW + very high ambient temperature at high altitude).

If there's enought thrust available, this is indeed a bug. Looks like the logic commands pitch down too quickly so that the plane has no time to accelerate using the available thrust and v/s goes to negative values before the required speed is reached. Better would be that the nose is lowered slowly and negative v/s values are avoided completely if the dialled altitude is higher than the current one.

Could any developer comment this please?

Andreas

Thanks for the confirmation Andrew.

Let's just hope this can/will be corrected one day.

In the meantime I'll be using the other rw procedure.

Fritz - yes, hopefully it will get worked out for you because the vertical speed "Half Rate" method used by AA, COA and MidWest is archaic and potentially unsafe. Another viable and acceptable option in use by Delta and most other carriers is to select VNAV or PERF at the acceleration point (3,000FT for VNAP A, 1,000FT for VNAP B) to execute the acceleration and initial climb. Both methods (IAS and VNAV) work for me, but I'm also using the FS9 version. Give VNAV a try and see if it yields the same results during acceleration as IAS mode. Now if only I didn't have to revert to IAS mode above 10,000FT to get around the VNAV climb speed bug! ;-)

Hi,
I have made some improvement in the IAS mode in FSX... will post new installer soon.
Davide

Thank you Davide.

I dont think this is a bug... rather incorrect procedure. Keep in mind... in R/W operation the autopilot is not in CMD immediatly after gear up. You really need to hand fly the airplane and let it stabilize before letting 'George' take over. I've never had any problems on takeoff with this bird. Im not sure why you wouldn't use VNAV on climbout anyway... its there to use and thus far has worked flawlessly for me. My T/O procedure is as follows... Set about 80% N2 and let stabilize, engage autothrottle and set power to t/o thrust. Rotate.. Gear up... pitch into the F/D to hold V2+10 and just maintain that pitch attitude until I reach acceleration height (usually about 1,000-1,500 ft)... at accel height I then select VNAV and either HDG TRK or NAV TRK, I pitch down into the flight director, select CLB thrust and finally engage the autopilot into command... it holds the nose over through flap retraction and accelerates to 250 for initial climbout. Using these procedures will give you a perfect departure everytime... the flight guidance on this bird is simulated perfectly if you use it properly.

Regards,

Tom

Tom,

Why are you using N2 as the primary indication? EPR should be used as the prime thrust indication for setting desired thrust, N2 should be looked at as secondary and as a note to the two airline profiles I posted earlier, is that if you chase the F/D on takeoff you run the risk of a tail strike, both airline manuals say to pitch up gently 2 to 3 degrees per sec to 8 then follow and rotation should take no longer then 6 seconds.

In terms of setting a mid-range thrust to bring the engines up to speed, it does not really matter which indication you use... this is not really the point here. The F/D shouldn't be used for rotation, this is merely a visual thing... until the gear is up and sufficient clearance from the ground is attained. There needs to be a good balance between utilizing the flight guidance and hand flying... you cant expect good results by horsing the airplane off the ground and just flipping the autopilot on... there needs to be a bit more intervention, in all stages of a flight.

I was asking because every airline training aid I've had or seen on any aircraft that has EPR as a part of the engine indications say to use it as prime thrust reference, I know it wasn't, again I was just curious on what advantage you have, didn't say you were wrong, sorry if it sounded like I was. Agreed that is one reason I like the MD-80 its not so automated that the computer does all the work, but its not all manual work, like older planes.

It's a bug Tom.

@ Jared - Nor was I trying to refute you. You make a good point, I just wasn't sure what it had to do with the problem of this thread..

@ Fritz - Well im not going to waste my breath (or finger stamina) trying to convince you otherwise... its your dilemma.

Tom

Me too in Maddog 2010 ... think that is a bug ... Maddog 2008 is OK

When ????

When it will be made ??

Soon could be another 6 months. Have patience.

Best regards,
Robin.

I think the same thing ... some day

greetings,
Alberto.-

Hello, again, Davide:

It is possible that the correction to this bug this already in the current installer ?????

Regard
Alberto.-

i've the same problem..exactly the same..
it's impossible to use IAS/MACH mode, unbelievable for "the best simulated aircraft"..
i suggest the staff to give a free copy of the maddog2008 (for 2010 edition owners) that has not this bug..

Dear Davide, Hello again, again, again ...................
First congratulation, again, for this extraordinary addon that I enjoy for several years and, without place to doubts, one of the best in this market.

The past 18/05/2010, Fritz Essono - begin a discussion in the forum section: Fly The Maddog technical support, called Maddog IAS UGLY behavior in FSX"….. in answer to him and some other ones that wrote, include myself, you responded the 21/05/2010, textually: " I have made some improvement in the IAS mode in FSX... will post new installer soon." …. The certain thing is that five months have passed, there is not answer, and I don't believe that we are the only ones.

In the same forum they are given some solutions that in fact they help but it is not the correct thing.. I like it works PA in flights to low speed but result inconvenience to make it as Mr. Fritz Essono describes it, I never saw such a situation in the previous versions (neither in the real life) of this I magnify addon (VSI goes into negative values, DIVING to gain speed!!!). negative climb.

That it has passed with the new installer with the engaged improvements? …… My solution has been to return to the previous version (2008) that works like it should be and to wait to see if some day the new installer arrives with the improvements.
Muchas gracias y hasta pronto

Alberto Angulo

PD: This is a mail that I sends to Davide (23 - 10 - 10), without answer... thank you !!!
Sorry, English is not my language

Hi, Thought i was a very bad pilot I have the same issues with Maddog 2008 Pro FSX during descent with Flightlevel change. All the suddenly the plain starts to rise to +4000 feet if i for instance choose IAS MACH 230 and the speed is about 250knots. Rollercoaster ride :-) Sometimes it does nothing. I dont understand why the speed in FMC is totally wrong .It gives me a cruize speed of 315 knots and 321 in the climb page. 315 or 321 on the descent page . OVERSPEED all the time. AIRAC is 1012.btw. why does the plain not hold the 250/10000feet restriction as well? I have to manually put it in the FMC but id does not work at all overspeeding all the time even on LEGS page were the the speed is right.

Regards Michael

Hello,

I'm not completly sure but I found that : h_tp://www.topflighthangar.com/manual.html#IASMACH (please replace the "_" by "t" because I can't post with a link !)

This doc making reference to MD-80 operation manuel on X-plane but I guess the sources are from the real Operation Manual (I hope ;-)).

May be I'm wrong... After read it, I understand that the IAS/MACH is NOT linked to Alt (logic system) but it is linked ON pitch only attitude at the moment you press the IAS/MACH mode then after you change with AND or ANU pitch.

In clear for me it seems not like FLCH mode on 747, 737 etc...

To be sure, I would like to find the real operation manual but it seems no so easy.

Regards

Richard Portier

HAPPY NEW YEAR 2011 DAVIDE !!!!!!!

PLEASE, DON'T FORGET US, ONLY FIVE MONTHS FOR THE FIRST ANNIVERSARY (21/05/2010) ............. MIRACLES HAPPEN, I BELIEVE !!!