how to hand fly with C*U law aircraft

[cmbaviator 5]

Question #1: Did you change speed?

Yes?  Trim.

No?  The aircraft has trimmed for you.  Repeat Question #1.

 

Yes but when you're trimmed for X speed , how do you maintain the desired flight path at X speed ? What i mean is that imagine that you're trimmed for 160 kts and flying level, you disengage both AP and AT, and pudh the yoke until you get a -600 fts/min when you release the stick will the flight path ( ie -600 fts/min :constant speed) remain inchange ????

[Michael Moe 493]

Yes but when you're trimmed for X speed , how do you maintain the desired flight path at X speed ? What i mean is that imagine that you're trimmed for 160 kts and flying level, you disengage both AP and AT, and pudh the yoke until you get a -600 fts/min when you release the stick will the flight path ( ie -600 fts/min :constant speed) remain inchange ????

 

 

It does with AT on . Otherwise its just a cessna ?

 

Michael

[scandinavian13 5,192]

 

 

What i mean is that imagine that you're trimmed for 160 kts and flying level, you disengage both AP and AT, and pudh the yoke until you get a -600 fts/min when you release the stick will the flight path ( ie -600 fts/min :constant speed) remain inchange ????

 

No.  If you don't adjust your throttle, the plane will re-establish itself at the nose-level position it was at before.

 

Same thing is a Cessna (again):

Pitch + Power = Speed.

Being in or out of trim is dependent on speed for the level of trim (and config, but that's the part the 777 manages for you :wink: ).

 

You're trimmed for 100.  If you pitch down without changing your power, your speed will increase, and you will end up out of trim.  Same goes with the 777.  If you want to maintain 100 knots in the descent, decrease your power and the plane will naturally start descending at the 100 knot trimmed speed.

 

http://www.amazon.com/Stick-Rudder-Explanation-Art-Flying/dp/0070362408

 

The pitch, power and trim thing was a fundamental concept that could've kept AFR447 out of trouble (in theory).  For a given power setting and a given trim setting, the aircraft will eventually stabilize at X speed.

 

People are really over-analyzing this, in my opinion.

[cmbaviator 5]

I'm aware tthat if the aircraft is trimmed for  X speed if you accelerate or decelerate, the Aircraft will pitch up or down accordingly. the thing is how to keep the desired speed while maintainning the desired flight path.

 

I notice that even with AT on the aircraft is still pitching down most of the time, even if the AC is correctly trimmed at the desired speed ....................

[The Blue Max 0]

6 pages of discussion on trimming should tell you that something is wrong.

 

When I fly the Cessna, NGX, 747 or even the MD-11 with LSAS I do so intuitively.  When the stick gets too heavy I trim out the difference to maintain stability.  I don't even think about it.  I don't even really think about speed.  Just stability.

 

With the 777 am I trimming purely for speed or for stability?  It should be both of course, but I am plummeting up and down with no clear idea of what that action means in this plane.  It seems to be all about speed.  When I turn on the FBW Ref indicator I am often far away from where I thought I was in the envelope.

 

I've just watched a few cockpit videos of pilots manually flying the 777.  It looks effortless, almost thoughtless. 

 

We've gone from the ridiculous to the sublime.  Before we couldn't trim, now I'm trimming to ridiculous lengths to maintain what, speed?  stability? 

 

It's a doddle to fly with the fbw trim ref activated I must admit but I shouldn't need that.

 

SP1 is an embarrassment of riches.

 

Richard Wells

[whoispankaj 51]

If you are trimmed at 160 knots with A/T on, you push down and maintain the stabilized descent of 600ft/min..The aircraft will maintain that since A/T now reduces thrust automatically to maintain the desired speed.So when you slowly center the yoke the aircraft with maintain the descent rate(+/- here and there)..This is what was mentioned in the FBW video and this is how the aircraft reacts to in the sim.And it makes sense with the pitch power theory since A/T manages the thrust automatically..

You just have to allow the thrust to stabilize once you achieve your descent rate and maintain it..Then you can slowly release the yoke...

[scandinavian13 5,192]

 

 

SP1 is an embarrassment of riches.

 

Sorry, but your post points more toward your misunderstanding of the concept of trim than it does the issue at hand.  The only time I've heard anything about trimming for stability is in maritime references.

 

In an aircraft, trim is all about lessening control forces for the flight condition.  In other words.  Elevator trim is all about matching control surfaces to the forces necessary to maintain a constant pitch for a given speed.

 

In an entire decade of flying (+ now), I have never heard "trim for stability."

 

It's usually best to avoid casting aspersions on others until you're sure you're right.  Even then, it's best to do so with a little more tact...

[James Bennett 52]

Question #1: Did you change speed?

Yes?  Trim.

No?  The aircraft has trimmed for you.  Repeat Question #1.

 

I will give an example, in a turn in level flight, under the command of autothrottle but hand flying, i am set to maintain a given speed and when i begin the turn the aircraft will begin to nose dive or climb when it should not, the throttles should change to fit the speed commanded and they do, but for some reason i am left to trim the aircraft myself else it becomes "out of trim" and climbs or descends rather sharply.

[777simmer 117]

Awesome post Rob.

 

After reading, I wanna say A320-A380 FTW, as the C* autotrims for anything, so you don't need to get confuse with Trim reference speed, artificail feels....

 

 

@ Rob

 

How do you change the flight path while in trim :

 

For instance, lets say that you're in trim for 160 kts speed at a v/S of -500 feets/min, and you want to fly level at 160 kts, do you have to only to increase the thrust ?

 

 

You pitch up untill vs is zero.

AT will increase thrust for constant speed.

(trimming is not required)

try it with the FBW trim speed displayed so you can see you are in trim.

(that means, with AT engaged, magenta speed bug + current speed + FBW trim speed all have to be the same)

I find the PMDG777 very stable as long as you are in trim.

 

Because during an ILS approach, wy VS was -900 feets /min and was getting below, so I pitch up until I get -600 fts/min but after releasing the yoke ( AT on), the Ac will slowly pitch down, so I don't know how to maintain a steady flight path Imy vertical speed always go within -900 and - 550 and it's not very stable :(

 

Do you have an advice ?

 

Thnaks

 

CMB

 

 

It is just basic pitch and power flying.....the first thing you have to learn if you want an instrument rating!

Pitch for vertical speed.

Power for speed.

 

Real aircraft:

once in trim and getting below Glide Slope you just pull a little to reduce vs.

On a Cessna you add power, on the 777 the AT adds power for you to maintain speed.

No need to trim on the 777 because the speed is still the same.

 

Having said that, a 777 is not stable like an airbus.

So even once you feel like you are in trim, and established on the glide slope with final flaps and gear down.....you can not close your eyes and expect it to keep following the glide slope.

Constant corrections in pitch (between 0 and 2.5 degrees pitch) are required to maintain the proper vertical speed as wind and gusts try to alter your flight path.

Just like in a Cessna the 777 does not correct for being thrown of path or vs!

By the way, find myself re-adjusting that final trim setting several times even as low as 500ft with just a small nodge of the trim switches. (we don't have a FBW cheat mode ;-) )

 

PMDG777:

The thing with the PMDG777 is that I have a hard time feeling whether an instable pitch (it goes up or down changing vs to something I do not want) is due to being out of trim or just that natural variance of the flight path you have to correct for as a pilot.

So that is why I say.....disdplay the FBW trim speed.....this way you KNOW you are in trim.

From then on all you need to is keep pitch for the required vs.

AT will keep speed.

[777simmer 117]

Struggling to fly this thing. Kyle says to fly it like a cessna, I cannot fly it like this as it seems to wildy pitch up and down and doesn't apply trim until the control column is centered and by then it's maybe over compensated. I also can't tell when I'm meant to be trimming and when it is trimming itself.

Yep that is because you cant feel when you are in trim. That is why I advice to display the FBW trim ref speed.

Make sure magenta speed bug (Vref+5) + actual current speed + FBW trim ref speed are all the same.

You are now in trim.

Don't touch the trim switches again!

From here on you fly like a Cessna.

Pitch for the correct vs....AT will work on the speed.

 

But you got to work that pitch.....every time the speed is off by a few knots you are out of trim and the airplane reacts to this by pitching up/down, throwing you off your wanted vs.

This is normal!

People are really over-analyzing this, in my opinion.

Yes basic pitch power flying, that's all

 

BUT

 

Without the FBW trim ref speed displayed I have a real hard time stabilizing the approach!

6 pages of discussion on trimming should tell you that something is wrong.

 

When I fly the Cessna, NGX, 747 or even the MD-11 with LSAS I do so intuitively.  When the stick gets too heavy I trim out the difference to maintain stability.  I don't even think about it.  I don't even really think about speed.  Just stability.

 

With the 777 am I trimming purely for speed or for stability?  It should be both of course, but I am plummeting up and down with no clear idea of what that action means in this plane.  It seems to be all about speed.  When I turn on the FBW Ref indicator I am often far away from where I thought I was in the envelope.

 

 

Yep.....same here....without the FBW trim ref speed I can not feel where I am stability wise......so you gotta keep that speed displayed, and set it at your target speed.

 

Magenta bug (target speed) must be the same as FBWtrim ref speed.

 

This way the AT is adjusting for the same speed as where the FBW trim ref speed is set and so the AT works towards an IN TRIM situation.

[Swen 1]

You cant feel if the bird is in trim if you need force on yoke to hold on level? Is that not the same? In both situations; i mean its equal to get force from the bird or if i must take force to the yoke to hold level and speed. If i dont need force on yoke the plane is in this condition what i like, its trimmed. Right?

[777simmer 117]

In an aircraft, trim is all about lessening control forces for the flight condition.  In other words.  Elevator trim is all about matching control surfaces to the forces necessary to maintain a constant pitch for a given speed.

 

Yes, but since I can't FEEL when I am IN TRIM with the PMDG777 (on my system when I think I am in trim I am usually at least 20kt off!)......resulting in constant pitch up and down instability (well it actually is speed stability at its finest what is happening ofcourse, but the result is an instable flight path)..........I (and it seems some others as well) need something else to give us an IN TRIM indication.....and that is where the FBW trim ref speed comes in ;-)

[cmbaviator 5]

[777simmer 117]

You cant feel if the bird is in trim if you need force on yoke to hold on level? Is that not the same? In both situations; i mean its equal to get force from the bird or if i must take force to the yoke to hold level and speed. If i dont need force on yoke the plane is in this condition what i like, its trimmed. Right?

Sorry I do not know if you are asking me something, asking someone else something or if it was a retorical question.

 

Sorry.

[The Blue Max 0]

Yep.....same here....without the FBW trim ref speed I can not feel where I am stability wise......so you gotta keep that speed displayed, and set it at your target speed.

 

 

Whoa...what?  You mean you trim for stability?  That can't be!  Pilots never do that. Kyle just told me so.  But you're a real 777 pilot right?  I am now sooooo confused!

 

No such thing as trim speed either, in addition to trim stability in maritime circles:  https://www.google.co.uk/#q=trim+for+speed

 

Lordy mamma, whats next?  Does he pull all his knowledge out of his &@($*?

 

Richard Wells