PMDG 777 - FBW Speed Trim System

[@ABeech-zv5ri]

This is probably the perfect first video to look at as a new 777 pilot, thank you!

[@Blackbox711]

Thank you for watching

[@ThePilotovirtual]

Dear Professor BB, your delivery, knowledge and explanation quality is top notch. Thanks for taking time out of your busy schedule to educate us.

[@Blackbox711]

My pleasure and thank you for watching ✈️

[@evau.alfredhummer7305]

Vielen Dank für das informative Video um das Fbw und die damit verbundene Trimmung zu verstehen und richtig anzuwenden um das Flugzeug auch manuell korrekt zu fliegen

[@Blackbox711]

Vielen Dank für das nette Feedback ✈️🙏

[@adriannerobbennolt64]

Wish you luck in growing your channel. Good stuff.

[@evanhellman]

Super informative Capt. thanks so much for sharing your knowledge.

[@Blackbox711]

Thank you for watching and your kind comment

[@V1Sim]

Thanks for this very informative. Wrapping my head around boeing fly by wire is new for me. I’m trying to set up a force feedback profile, with that in mind would it be accurate to say that when the aircraft is AT trim ref speed the control forces are very minimal? If wanting to accelerate, pushing forward on the yoke will have more force until reaching the new desired speed while moving trim simultaneously. (Making it essentially feel like a conventional aircraft being “in trim”)

[@Blackbox711]

Hey. Thank you! With a force feedback yoke it should be as you wrote, there should be no control forces when the actual airspeed is at the indicated trim reference speed. The challenge comes with airspeed changes. An instructor will tell you to correct first with yoke input and then trim away the pressure. However here as you wrote you would do this in tandem just like in an conventional aircraft. The more you practice the more intuitive it becomes. Btw. I had to order the FF Brunner after watching you fly with it. Happy Landings ✈️

[@V1Sim]

@@Blackbox711 thank you that helps! Oh wow thats awesome I cant wait for you to get it so you can make even better profiles! lol the software takes a minute to get used too, and its not perfect, however once you go FFB there is simply no going back. Cant wait to hear what you think about it!

[@Blackbox711]

@@V1Simdefinitely will get in contact with you when I receive the yoke

[@malindley]

Thank you for the clear explaination Captain 👍

[@Blackbox711]

Thank you Mark 🧑‍✈️✈️

[@SimPicks_real]

Thank you! What a great presentation.

[@Blackbox711]

Thank you very much

[@mattzoom8656]

On the side note, if I recall correctly, the trim tab will not be moved by the FBW system unless the yoke is neutral in the pitch axis.

[@Blackbox711]

Could very well be. It is not described in much detail on how and when the FBW system uses elevators and stabilizer position. If you find a good reference I would love to hear where I can find that.

[@hkk5790]

There are quite a few checks to prevent the FBW from flying the airplane with the tail plane.Can’t remember how Boeing did it, but checking the column position OR checking the rate of elevator deflection can both rule out the transient motion.

[@tomrach8092]

Is it true that the B77W, with AP turned off and A/T turned on, when approaching at an altitude of 20-30ft above the runway, automatically reduces the throttle thrust to idle?

[@Blackbox711]

During flare: flight director roll and pitch bars retract from view between 25 and 50 feet radio altitude, the autothrottle begins retarding thrust levers to idle

[@kdfw3686]

how many springs do you have in your yoke and does that approximate the stiffness on the real 777? 4 springs make it quite stiff so making small pitch inputs is not really smooth, 2 feels rather too soft. so wondering how you set it up at your end. thanks for the videos.

[@Blackbox711]

I agree. I have 3 springs installed. Not exactly the same feeling as in the real 787 but as you mentioned best balance.

[@richardcarter5404]

@@Blackbox711 I never thought about trying three springs. I’m going to give that a go right now, what are your sensitivity settings in the SIM? I always seem to struggle to get a decent balance when using the boeing yoke

[@Captainriad]

HI BB . I wonder how does the Thrustmastrt yoke feel comparing to the real one ? Out of 10 ?

[@Blackbox711]

Hey. Compared to what aircraft? 777/787? Or 737?

[@speedbird8326]

Hi BB. As a 29 year 737 pilot and ex military pilot, can you confirm the same principles hold for manual flying in the 777 as they would in the 737. That is, one sets the attitude and then trims to remove all control column forces. Without the FBW indication on the speed tape in the real aircraft, how do you know what speed you are trimming for ? I understand that the FBW system works differently under the hood, but isn't it for all practical intents and purposes the same as the 737 for manual flight ?

[@Blackbox711]

Hi. Taking your example: lets say you are flying manual and trimmed nicely for 250 kts, flying at 3 degree pitch. Then you want to climb at a pitch of 6 degrees. You would pull on the yoke and put in a 6 degree pitch value and manually (or autothrust) add thrust to maintain the 250 kts. Then no pitch trim input would be needed as the FBW would do its thing to maintain the pitch. The principle of the FBW system is mainly to help stabilize the aircraft and to keep it within its flight envelope. Boeing has a slightly different design compared to Airbus where the automatic pitch trim does not include speed changes in manual flight. Airbus on the other hand does this too.

[@speedbird8326]

@@Blackbox711 Ok so you’re saying that if I did the same thing in the 737 I would have to re-trim as I changed from 3 to 6 degrees whereas in the 777 that’s not required.

[@Blackbox711]

@@speedbird8326 a pitch increase changes several aerodynamic factors. The 777 adusts those in manual flight apart from a speed change trim requirement. In a 737 there will be a trim requirement already for the thrust increase. So yes, in manual flight the 737 will need more trimming.

[@speedbird8326]

@@Blackbox711 Ok thanks for the explanation.

[@TrueBlade-1889]

So are we automating the trim to maintain pitch... or speed ? E.G. When you land, you extend flaps and reduce throttle deliberately to reduce speed, but you need the same pitch to maintain the fpm decent rate, to stay on the GS. I'm confused.

[@Blackbox711]

As you change flaps setting and reduce speed you are changing the relationship between Center of Gravity and Center of Lift. That causes the necessity to change the stabilizer position, hence the pilot needs to trim in manual flight. You trim the FBW speed reference to the new desired airspeed that you need. The FBW speed reference setting does not influence the autothrust! The position of that FBW trim reference speed is the airspeed the aircraft will stabilize at eventually if you let go of the yoke. So the FBW in the background will pitch the aircraft up and down (depending on the actual airspeed being fast or slow) until that trim reference speed is attained.

[@scottietoo4160]

How do the real pilots know what speed they are currently trimmed to? Is this with the Auto-Throttle off? I like to manual fly so AP & AT off and am struggling to trim the 777

[@Blackbox711]

In the real aircraft pilots get an instant feedback through the yoke. If the aircraft isn’t trimmed to the current speed the pilot has to continuously push or pull on the yoke to maintain the current flight path (i.e. level flight). This feedback isn’t available to flightsimmers unless they have a force feedback yoke.

[@xstrakus]

How can I turn off auto-trim to use it manually?

[@chrisblair1838]

In manual flight with autothrust on (is this allowed on the 777?) is the trim speed reference setting coupled with the speed setting for the autothrust?

[@Blackbox711]

Hi. No it isn’t. That is completely seperate and takes the target speed value (magenta pointer on the speed scale).

[@Blackbox711]

And yes, it is allowed to fly with autothrust off

[@ChMueller001]

What does one have to do when the actual speed deviates from the ref speed? Use the trim controls until they match again?

[@Blackbox711]

The FBW speed trim reference should be put to the speed you want to fly. So if the speed deviated from reference speed and you want to return to it then don’t change the trim.

[@killamikethegod7962]

Is there a way to completely disable the fbw trim system?

[@Blackbox711]

Yes, setting Primary Flight Control Switch on the Overhead panel to off.

[@Blackbox711]

But be aware that also kills the autopilot

[@killamikethegod7962]

@@Blackbox711 thank you sir! My next question for you is, does the Y/D work all the time as long as the fmc is powered or is there a switch I’m missing? (I’m used to the 737-800 overhead switch)

[@plummer43]

Wtf is that shaking while moving the trim on ground?

[@Blackbox711]

I saw that too and can only imagine low animation quality