Autothrottle Hold Mode

[scandinavian13 5,192]

 

 

My question is : Does PMDG service pack will fix the way how it is presently modeled ?

 

Not quite sure what you're assuming is broken that needs to be "fixed"...

 

What am I missing?

 

 

By the way I'd like to congratulate to Kyle Rodgers...He has been doing a nice job !
 
Thanks for sharing with us ....kyle Rodgers.

 

Thanks!

 

...and you're welcome!  :wink:

[hopskip 253]

 

 

My question is : Does PMDG service pack will fix the way how it is presently modeled ?

 

 

 

Considering the release product we currently have models the FLCH correctly.

 

Then yes! it will be fixed in the service pack because it is fixed already in the release version. The changes should be as follows:

1: none

 

yay!

[vpiragibe 1]

Dear Marco.

 

Be careful with what some people here in this Forum say and write.  Specially what happened to Asiana. There is a significant difference between having an idea about, and really knowing what happened...

 

Simply, try this in your PMDG 777: 

At any configuration ,with A/P, F/D and A/T engaged,  at 10000 feet, set 0 ( zero ) on the altitude window.  Now press FLCH.  The plane will start to descend, at the commanded speed ( bug speed ). The FMA initially will be  THR I xxx I FLCH . Soon after the throttles reach idle, the HOLD mode will replace the THR mode . So far, so good...

 

While descending, disconnect the A/P and disconnect ONLY your side F/D ( leave the other F/D ON ).  Now, start pulling the yoke for a level flight ( or a shallow descend ), and allow the speed to reduce into the yellow band.  Half way into the yellow band, you get EICAS " AIRSPEED LOW" , however, you do not get the A/T " wake up" protection !

 

At this point, if the fellow Korean pilot ( or yourself ) had disconnect the other F/D , the FMA HOLD mode will turn to SPEED mode,  the A/T will "wake up" and the throttles advance to maintain the bug speed. A Beautiful Stall speed protection...

I dont want to extend this talking, but for your info, the correct F/D config for a visual approach, is to have the Pilot Flying and Pilot Monitoring OFF ( in this sequence ), then Pilot Monitoring ( only ) selected to ON. This is to avoid losing the stall protection in case of a Go Around. FCTM 5.45 , 5.54

 

Conclusion: should the pilots had follow the Boeing FCTM , the outcome certainly was a normal landing.

 

Vpira

[MAXM958 2]

Dear Marco.

 

Be careful with what some people here in this Forum say and write.  Specially what happened to Asiana. There is a significant difference between having an idea about, and really knowing what happened...

 

Simply, try this in your PMDG 777: 

At any configuration ,with A/P, F/D and A/T engaged,  at 10000 feet, set 0 ( zero ) on the altitude window.  Now press FLCH.  The plane will start to descend, at the commanded speed ( bug speed ). The FMA initially will be  THR I xxx I FLCH . Soon after the throttles reach idle, the HOLD mode will replace the THR mode . So far, so good...

 

While descending, disconnect the A/P and disconnect ONLY your side F/D ( leave the other F/D ON ).  Now, start pulling the yoke for a level flight ( or a shallow descend ), and allow the speed to reduce into the yellow band.  Half way into the yellow band, you get EICAS " AIRSPEED LOW" , however, you do not get the A/T " wake up" protection !

 

At this point, if the fellow Korean pilot ( or yourself ) had disconnect the other F/D , the FMA HOLD mode will turn to SPEED mode,  the A/T will "wake up" and the throttles advance to maintain the bug speed. A Beautiful Stall speed protection...

I dont want to extend this talking, but for your info, the correct F/D config for a visual approach, is to have the Pilot Flying and Pilot Monitoring OFF ( in this sequence ), then Pilot Monitoring ( only ) selected to ON. This is to avoid losing the stall protection in case of a Go Around. FCTM 5.45 , 5.54

 

Conclusion: should the pilots had follow the Boeing FCTM , the outcome certainly was a normal landing.

 

Vpira

 Ok ..fellow !

 

Seems that I haven't explained clearly.

 

I was thinking and talking only at take-off...try to examine with more attention and may be you can see what I've been tried to explain. To simplify : the Hold mode in takeoff changes.at 400 ft AGL to Thrust Reference Mode without any change to Vnav or other vertical mode... please read FCTM last paragraph on page 99. 

 

Thanks so much for your attention.

 

Best of all.

 

Marco Aurélio.

Not quite sure what you're assuming is broken that needs to be "fixed"...

 

What am I missing?

 

 

 

Thanks!

 

...and you're welcome!  :wink:

Hi Kyle

 

See the post above !

 

 

Thanks,

 

 

Marco Aurélio

Considering the release product we currently have models the FLCH correctly.

 

Then yes! it will be fixed in the service pack because it is fixed already in the release version. The changes should be as follows:

1: none

 

yay!

 

 

  Thanks hopskip ! Ah...Ah....

 

 

Marco Aurélio

[scandinavian13 5,192]

 

 

I was thinking and talking only at take-off...try to examine with more attention and may be you can see what I've been tried to explain. To simplify : the Hold mode in takeoff changes.at 400 ft AGL to Thrust Reference Mode without any change to Vnav or other vertical mode... please read FCTM last paragraph on page 99.

 

While I applaud you for looking into the manuals, you always have to remember that the FCTM is somewhat summarized when compared to the FCOMs.  The FCOMs go into greater detail, and as such, are the true reference material for where you'd want to go to confirm or question the correct operation of the aircraft.

 

FCOMv2 4.20.10 goes into more detail, but the basic explanation of what you're seeing is:

Hitting TO/GA selects THR REF as the thrust mode.  That is overridden by HOLD at 80 knots.  VNAV automatically kicks in at 400', unless you hit TO/GA again after 50 knots.  Since VNAV automatically kicks in at 400', THR REF resumes as the active thrust mode.

 

What you're seeing is the proper behavior.

[Mike777 163]

 

 

I was thinking and talking only at take-off...try to examine with more attention and may be you can see what I've been tried to explain. To simplify : the Hold mode in takeoff changes.at 400 ft AGL to Thrust Reference Mode without any change to Vnav or other vertical mode... please read FCTM last paragraph on page 99.

 

Hi, Marco,

 

I think you  may be misreading "VNAV engagement" to mean "pilot engages VNAV."  VNAV is normally armed on the ground and "engages" automatically at 400 ft.  At that time thrust mode switches out of HOLD to another mode - normally to THRUST REF.  Take a look at FCTM "Pitch Modes," FCTM p. 322.

 

Mike

[MAXM958 2]

Hi Kyle,

 

No !

 

I'm not using VNAV at takeoff.. I'm just using TO/GA and LNAV ....nor Auto Pilot.

 

Your last paragraph is correct and I understand what you are saying !

 

Thanks.

[scandinavian13 5,192]

 

 

No !
 
I'm not using VNAV at takeoff..

 

I never said you have to.  Read 4.20.10.

 

It never mentions a single thing about pre-arming VNAV at all.  It is automatic unless cancelled by hitting TO/GA after 50 knots.  Autopilot is also irrelevant to the discussion, because ON or OFF, you're going to get the same behavior.

[Mike777 163]

Hi, Marco,

 

Since you cited a paragraph in the FCTM on p. 99 that is discussing VNAV and Autothrottle transition out of HOLD, I thought you were using VNAV.  However the wording of the FCTM is a bit misleading.  It says that HOLD mode "remains engaged until VNAV engagement or another thrust mode is selected."  This implies that, if VNAV is not selected, the pilot must intervene to "select" another thrust mode when in fact THR REF is automatically selected in most circumstances.

 

Mike

[MAXM958 2]

Hi, Marco,

 

Since you cited a paragraph in the FCTM on p. 99 that is discussing VNAV and Autothrottle transition out of HOLD, I thought you were using VNAV.  However the wording of the FCTM is a bit misleading.  It says that HOLD mode "remains engaged until VNAV engagement or another thrust mode is selected."  This implies that, if VNAV is not selected, the pilot must intervene to "select" another thrust mode when in fact THR REF is automatically selected in most circumstances.

 

Mike

Thanks Mike777 .....

 

 

I'm editing a video to show one take-off from LPPT to LPMA... and a Landing as well showing some characteristics of this outstanding PMDG Product. Please i'd like to hear your comments after you have the patience to watching it.

 

Again...my intention is only share some pleasure moments with other simmers.

 

Best of all,

 

Marco Aurélio

I never said you have to.  Read 4.20.10.

 

It never mentions a single thing about pre-arming VNAV at all.  It is automatic unless cancelled by hitting TO/GA after 50 knots.  Autopilot is also irrelevant to the discussion, because ON or OFF, you're going to get the same behavior.

You're 100 % right Kyle !

 

Please don't get me wrong...But at the end of this discussiion all of us will learn more about this outstanding Arliner.

 

And I have some new question about it like Ground Effect...and others. Of course not here but at another thread.

 

Kyle...my intention is collaborate only.

 

Best of all,

 

Marco Aurélio

 

 

 

Thanks.

[Mike777 163]

 

 

I'm editing a video to show one take-off from LPPT to LPMA... and a Landing as well showing some characteristics of this outstanding PMDG Product. Please i'd like to hear your comments after you have the patience to watching it.

 

Looking forward to your video!

 

Mike

[MAXM958 2]

Hi Guys !

 

A Break...tomorow will be a 2014 world cup soccer match BRASIL x CHILE at 13:00 Local Time or 16:00 UTC....it will be a outstanding game ! The game will happen in my city Belo Horizonte...Minas Gerais...Brasil.

 

Sorry it just a break !

 

Marco Aurélio

Looking forward to your video!

 

Mike

Ok Mike...may be today yet !

 

Congratulations to your support ( Donor ...if I've understood well ) ! 

[Mike777 163]

 

 

A Break...tomorow will be a 2014 world cup soccer match BRASIL x CHILE at 13:00 Local Time or 16:00 UTC....it will be a outstanding game ! The game will happen in my city Belo Horizonte...Minas Gerais...Brasil.

Sorry it jus a break !

 

Hi, Marco,

 

Since you are named for the Roman Stoic philosopher (and emperor) Marcus Aurelius, you should not indulge in such frivolous activities.  Instead you should be a good Stoic and get down to the serious business of ... making videos for flight simulator!

 

Sorry, couldn't resist.

 

Mike

[MAXM958 2]

Confusion of what the term "HOLD" means didn't play any role in this though according to the report. I don't think they even noticed the mode change honestly. The captain never should have hit FLCH in the first place and he never should have done it without calling out the mode change he was making verbally so that the other pilot was aware and could potentially correct it. The instructor pilot stated he never even noticed it (he was busy extending flaps or something at the time it was pressed). The captain very clearly didn't understand what he was commanding the AFDS to do in a much wider sense given that he commanded a climb at 1500 feet on an approach.

 

Regarding low speed protection, the issue as Boeing's chief test pilot and engineer described it at the hearing made a ton of sense to me - namely that doing so would violate two of their core principles.

 

1. The AFDS system can't have two controllers/inputs to the same primary flight parameter. FLCH is a pitch for speed or "speed on elevator" mode - if the AT kicked in while in this mode, you'd have both thrust and pitch controlling the airspeed parameter. That creates problems algorithm wise (PID instability, instability in a single engine thrust asymmetry situation etc) and it violates the design principle.

 

2. To mitigate #1 above, it would need to trigger a pitch mode change to a speed on throttle mode such as V/S, ALT, VNAV PTH etc as well. One of Boeing's other core design philosophies is that the pilot has control and AFDS modes should not change without the pilot commanding them to. When the captain held the thrust back against the motion of the AT servos as it tried to climb, this is effectively the same thing as moving the yoke while AP CMD is active. It tells the system "I want manual control." That's what HOLD is - it disconnects the AT servo and gives the pilot manual control. You'd have both the pitch and thrust modes changing on their own without pilot command and that's just not what Boeing does. If a pilot is just pressing buttons and moving controls without any regard for what those commands do *and* is incapable of properly handflying the aircraft after disconnecting the automatics, then that pilot shouldn't be in the cockpit, period. Blaming Boeing is totally obfuscating the true cause - lack of understanding of the airplane's systems and really, lack of basic piloting skills.

Hi Ryan.....good to see you here !

 

I think that 3 or 4 years ago you have been answered some techinical instalation issues about PMDG MD 11. Another awesome airliner and PMDG Product of course.

 

Best of all,

 

Marco Aurélio

[indyrocks 2]

I haven't been back since I posted my question yesterday. First, thanks to everyone who contributed. I have learned quite a bit from your comments. Second, thanks for not letting the discussion degenerate into a Boeing vs. Airbus argument. Some experts have pointed out elsewhere that the PF's experience — he was an experienced A320 pilot who was transitioning to the B777 — probably influenced what he believed was happening.

 

 

One other question. One of the board's findings (#14) mentions an irony...

If Asiana Airlines had not allowed an informal practice of keeping the pilot monitoring’s (PM) flight director (F/D) on during a visual approach, the PM would likely have switched off both F/Ds, which would have corrected the unintended deactivation of automatic airspeed control.

 

I've always thought that the flight director's purpose is to help the pilot keep the aircraft on the correct 3D path through the sky. Why would the flight management software be designed so that simply switching the FD off has such a dramatic effect on airspeed control?