1 hour ago, JRBarrett said:

Bypass reversers do not really “reverse” the thrust vector the way that older clamshell reversers that redirect the exhaust flow did. Those older style reversers could actually be used to back the airplane out of a gate.

With a bypass reverser, most of the air that comes out when in reverse comes out sideways, not forward.

The bypass reverser does two things: It stops the rearward movement of fan air through the bypass duct, which has the effect of cutting engine foward thrust by more than half, since the majority of thrust in high bypass engine comes from the fan. Some operators only use idle reverse on landing, but that is still effective at reducing the energy that must be dissipated by the brakes.

At higher ground speeds (right after touchdown) with “full” reverse, the blocked/redirected fan bypass air causes the fan itself to produce a tremendous amount of aerodynamic drag that acts like a speed brake of sorts. That drag is less effective as the aircraft slows down in the landing roll, but at initial landing speeds, the fan drag is significant.

Everything you say makes sense except for the fan drag at full reverse. If the engine is spooled up, the fan would not create drag. To create drag, the fan would have to be spinning slower than what it would free spin at, based on the speed of the aircraft. An example would be the tremendous drag created by a propeller when you decrease the power and prop RPM. I make these comments not authoritatively but as someone trying to figure out the physics. Thanks!!

I’m going to pass for a few reasons: the 300ER in MSFS2020 is very nice from a modeling point of view, but it hand-flies worse than their P3D version… and that’s saying something. There are many of us who complained about this for years regarding the “feel” of flight in their FBW implementation. I’m not getting burned $77.72 again for a remodeled 200ER (still waiting for that improved VC) with the same system logic than their P3D version. 
 

As problematic as their A350 was, the inibuilds in the latest version is really good and has nice immersion features, not to mention proper gsx integration, which PMDG continues to deny (yet you are unable to pushback in their own tablet?! Still!?!).

Sorry, but if I want a 200ER I’ll scratch my itch in FlightFactor’s 777v2 in XP12  which hand-flies great, has great system depth, sounds great and provides more immersion out of the box (I know their still at “beta” regarding VNAV).

PMDG has to improve their game if they want to keep charging those prices. Learnt my lesson with the 300ER which I shouldn’t have bought due to their 200ER money-grab from P3D.

 

 

7 minutes ago, Purr said:

It’s actually the opposite. Higher effect at higher speeds. Otherwise they would wait till aircraft slowed to 80 before pulling them on. It’s physics. 

There is also a greater risk of FOD ingestion at lower speeds.

31 minutes ago, LRBS said:

747 Throttletek. But it has nothing to do with backing up the airplane, activating the reversers in this case.

I was wondering if you only had one reverser configured. My posted video clearly shows that the plane didn't move backwards with full reverse and moved forward with idle reverse. I can get it to back up if only using one reverser. 

5 minutes ago, evaamo said:

.lAs problematic as their A350 was, the inibuilds in the latest version is really good and has nice immersion features, not to mention proper gsx integration,l

 

 

Not to get too far off topic but,  I am assuming you toggled on the GSX integration on the EFB for this? How do you feel it is working when compared to the Fenix GSX integration? I haven’t tried it yet.

23 minutes ago, Ron Lefebvre said:

Don't see the liveries included on their site.

Don't suppose they have a Delta liverie.

Liveries are listed in OC3. There are literally gigabytes of liveries, so you won't be disappointed. My sim computer is off right now. Will get you a screenshot next time it is on.

10 minutes ago, andym001 said:

There is also a greater risk of FOD ingestion at lower speeds

Yes indeed, and they ideally need to be at reverse idle by 60kts otherwise the airflow into the engines gets disturbed and they’ll start surging and banging….apparently.

21 minutes ago, Purr said:

It’s actually the opposite. Higher effect at higher speeds. Otherwise they would wait till aircraft slowed to 80 before pulling them on. It’s physics. 

I am thinking force vectors. Decreasing forward momentum vector vs static reverse force vector. Anyway, I will try to find a research paper on thrust reverser design and effectiveness.

I've seen several comments here and elsewhere talking about the improved flight model and handling in the 200ER in MSFS2024 compared to previous 777s. Can anyone talk about that more in depth? What is specifically better?

5 minutes ago, RNAVV19R said:

I've seen several comments here and elsewhere talking about the improved flight model and handling in the 200ER in MSFS2024 compared to previous 777s. Can anyone talk about that more in depth? What is specifically better?

I have flown real airline sumulators and the 777-200ER by PMDG reacts like the real full motion simulator would based on your control inputs. It is really, really good. 

47 minutes ago, Ron Lefebvre said:

Don't see the liveries included on their site.

Don't suppose they have a Delta liverie.

You have to download the liveries via the ops centre, none come with the aircraft by default. I believe I saw a Delta

40 minutes ago, alanw2005 said:

I was wondering if you only had one reverser configured. My posted video clearly shows that the plane didn't move backwards with full reverse and moved forward with idle reverse. I can get it to back up if only using one reverser. 

Well, there is an issue with how they adjusted the reverse thrust on this airplane. It does not exceed approximately 80%. In actual aircraft, it can go up to the maximum of the N1 modulated by the EEC, considering OAT, pressure, and elevation. For some reason, that's not the case here. Most of the time, we use idle or minimal reverse; very rarely do we engage full reverse, and only during certain situations when limited by runway requirements, use of maximum braking, and maximum reverse allowed by the EEC. 

Edited May 2, 20251 yr by LRBS

1 hour ago, JRBarrett said:

Bypass reversers do not really “reverse” the thrust vector the way that older clamshell reversers that redirect the exhaust flow did. Those older style reversers could actually be used to back the airplane out of a gate.

With a bypass reverser, most of the air that comes out when in reverse comes out sideways, not forward.

The bypass reverser does two things: It stops the rearward movement of fan air through the bypass duct, which has the effect of cutting engine foward thrust by more than half, since the majority of thrust in high bypass engine comes from the fan. Some operators only use idle reverse on landing, but that is still effective at reducing the energy that must be dissipated by the brakes.

At higher ground speeds (right after touchdown) with “full” reverse, the blocked/redirected fan bypass air causes the fan itself to produce a tremendous amount of aerodynamic drag that acts like a speed brake of sorts. That drag is less effective as the aircraft slows down in the landing roll, but at initial landing speeds, the fan drag is significant.

Here is a jet reversing with reverse thrust (with slit reversers as opposed to bucket type):

 

Edited May 2, 20251 yr by alanw2005

21 minutes ago, alanw2005 said:

Everything you say makes sense except for the fan drag at full reverse. If the engine is spooled up, the fan would not create drag. To create drag, the fan would have to be spinning slower than what it would free spin at, based on the speed of the aircraft. An example would be the tremendous drag created by a propeller when you decrease the power and prop RPM. I make these comments not authoritatively but as someone trying to figure out the physics. Thanks!!

It’s not exactly the same thing as reducing RPM at idle on a prop, because a propeller’s pitch is variable, while a fan’s blades are fixed in pitch. When the rearward flow of air through the fan is blocked and redirected sideways (and somewhat forward) the fan actively resists the inward flow of air into the inlet, and that resistance is greater the faster the fan is turning - (and the faster the aircraft is moving). It is a different kind of drag than that produced by a windmilling prop.

There is a law of diminishing returns however. At high power reverse, the thrust contribution from the exhaust gases increases, while the fan’s resistance to inlet airflow decreases as the aircraft slows down. 

Many large airports have restrictions on the use of any more than idle reverse unless absolutely necessary, due to noise and environmental impacts, but even idle  reverse is effective because it effectively “switches off” the flow of fan air rearwards through the bypass duct. 

The redirected fan air does have some “reverse” thrust effect but not as much as the old exhaust gas reversers where almost all of the engine thrust was redirected forward.

The explanation of how a cascade bypass reverser “does what it does” is specific to GE engines, and comes from GE engine maintenance classes (for CF6 and CF34) that I have taken at the GE facility in Cincinnati. I’m not personally an expert on the subject by any means.

There are other engine models that have a different method for redirecting fan air, using doors that open on the side of the nacelle that redirect a lot more of the fan air forwards. I think the Airbus A340 is one aircraft that uses this system, but even here, the reversed fan air will start to be neutralized by exhaust gas thrust at higher reverse power settings as the aircraft slows down.

Some may find this interesting: