PMDG 737-700 Update to Build 3.00.0031

[jarmstro 2,402]

I'm still finding that I have to use the spoilers more often than not on descent? This may be true to life but I doubt it? Does the plane have enough drag?

Edited July 30, 2022 by jarmstro

[threexgreen 3,135]

47 minutes ago, roi1862 said:

Does taping the brakes do not disconnects the autobrake ? I really have to turn the autobrakes switch to ‘off’ ? 

You have to apply manual brakes enough to exceed the brake force applied by the autobrake. This is true to real life, whereas before in the PMDG it was enough to just tap the brakes slightly.

33 minutes ago, jarmstro said:

I'm still finding that I have to use the spoilers more often than not on descent? This may be true to life but I doubt it? Does the plane have enough drag?

The 737 in real life is a slippery airplane. The speedbrakes are used IRL more often than many simmers seem to think, and VNAV also doesn't always get the aircraft down on a perfect path but needs some help occasionally depending on the conditions. I've personally never had to use the speedbrakes excessively and on most descents it gets down on its own.

Edited July 30, 2022 by threegreen

[roi1862 600]

1 minute ago, threegreen said:

You have to apply manual brakes enough to exceed the brake force applied by the autobrake. This is true to real life, whereas before in the PMDG it was enough to just tap the brakes slightly.

Thank you !

[Gazzareth 808]

1 hour ago, jarmstro said:

I'm still finding that I have to use the spoilers more often than not on descent? This may be true to life but I doubt it? Does the plane have enough drag?

It is meant to be slippy in real life from what I have heard. 90% of flights I manage to avoid spoilers in flight, although tends to mean planning ahead....

 

G

[jarmstro 2,402]

Just now, Gazzareth said:

It is meant to be slippy in real life from what I have heard. 90% of flights I manage to avoid spoilers in flight, although tends to mean planning ahead....

 

G

What I meant is why the flight computer calculates a TOD point which always requires the spoilers to be deployed? You can't plan ahead if you rely on the TOD marker? Surely this is very inefficient fuel wise?

[roi1862 600]

55 minutes ago, threegreen said:

You have to apply manual brakes enough to exceed the brake force applied by the autobrake. This is true to real life, whereas before in the PMDG it was enough to just tap the brakes slightly.

 

BTW, on the real thing does the pedals moves physically when autobrakes is active ? 

[roi1862 600]

3 minutes ago, jarmstro said:

What I meant is why the flight computer calculates a TOD point which always requires the spoilers to be deployed? You can't plan ahead if you rely on the TOD marker? Surely this is very inefficient fuel wise?

I actually think its more fuel efficient than vice versa and use engines to catch up on selected speed.

[jarmstro 2,402]

5 minutes ago, roi1862 said:

I actually think its more fuel efficient than vice versa and use engines to catch up on selected speed.

But the engines are burning fuel  to maintain cruise altitude longer than necessary?

[roi1862 600]

2 minutes ago, jarmstro said:

But the engines are burning fuel  to maintain cruise altitude longer than necessary?

Cruise is the most efficient part of the flight other than the idle descent If you start descent sooner on a shallow path and will need to use engine power to maintain speed/path you burning much more 

[jarmstro 2,402]

5 minutes ago, roi1862 said:

Cruise is the most efficient part of the flight other than the idle descent If you start descent sooner on a shallow path and will need to use engine power to maintain speed/path you burning much more 

Yes but shouldn't TOD be at a point where the plane descends to the first constraint at throttle idle without the need for constant speed brakes or any thrust?

[roi1862 600]

14 minutes ago, jarmstro said:

Yes but shouldn't TOD be at a point where the plane descends to the first constraint at throttle idle without the need for constant speed brakes or any thrust?

This is in a perfect world scenario… the Fenix for example doing the other way around and descents on a very shallow path. They said it will be addressed next patch…

Edited July 30, 2022 by roi1862

[threexgreen 3,135]

1 hour ago, roi1862 said:

BTW, on the real thing does the pedals moves physically when autobrakes is active ? 

They don't. Otherwise tapping would be enough as the toe brakes would be depressed down to that point already, but you have to push the pedals down and past that point to apply more braking power than what the autobrake is applying.

1 hour ago, jarmstro said:

Yes but shouldn't TOD be at a point where the plane descends to the first constraint at throttle idle without the need for constant speed brakes or any thrust?

Correct. Descent occurs at idle thrust and normally with no speedbrake application needed, but sometimes, depending on conditions, you have to help with the speedbrake (or increase thrust manually as needed when the autothrottle is in armed mode to maintain speed). I don't have to use the speedbrake too often in PMDG 737, most of the time it manages without me needing to use the speedbrakes. There is also a margin for speed undershoot until the aircraft goes back into FMC SPD from ARM and applies thrust to get back to the target speed which is 10 or 15 knots below the target depending on the airline's preference, so it's not rare to see the speed drop within that margin and you have to either let it go ahead at that speed or manually increase thrust. This happens in the real thing too.

The bottom line is that VNAV isn't perfect and you have to help it from time to time in both the PMDG 737 and IRL. If you have to constantly use the speedbrakes though there may be something amiss in your setup. I'm just saying that I'm not seeing any abnormal need for speedbrake use (other than to make a speed constraint sometimes because the PMDG likes to bust these from time to time, no idea if this is improved with this update).

Edited July 30, 2022 by threegreen

[ha5mvo 241]

@threegreen is absolutely correct. Beside that you might hit snags like ATC clearing you late for a variety of reasons and so forth, so you need to manage your energy carefully.

If you're used to the fenix 320 then its a different ball game since the latter is grossly over dragged. On this 737 you will need to use the handle of shame on occasion which is perfectly normal, as the man said.

[spesimen 135]

i think a big part of the speedbrake usage is the transition to <250knots when you get below 10000 feet. it's less efficient to descend at 250 knots, you'll have a very shallow and long path down and since you are going much slower it also ends up taking a lot more time which is more fuel. econ descents usually are something more like 260 or 270 etc. a lot of STARs also have restrictions like they want you to be at a specific speed like 280knots for traffic purposes so eventually you'll need to burn off that speed also and just waiting around coasting at 10000 takes a lot more time than hitting the brakes.

think of it as like driving to the grocery store without using your brakes. sure it could be possible but the last street before you turn in you'll have to coast very slowly if you actually want to stop at the right place. better to just go the speed limit and use the brakes when you get there. just like the car, the spoilers are meant to be used when necessary it's not an indication of poor piloting or planning.

cheers,-andy crosby

Edited July 30, 2022 by spesimen

[Stearmandriver 2,244]

I've never understood the "handle of shame" mentality of not wanting to use the speed brakes. Boeing put that handle in the airplane for a reason ;).

Honestly, I've watched people over the years get themselves all twisted up with convoluted flight guidance tweaking (being oversped the whole time they're doing this) in an effort to avoid using the brakes (or throw out the gear when it's clearly necessary) in an effort to avoid the rumbling noise for passengers.

My two thoughts about this are:

1.  We always prioritize precise management the aircraft's flight path ahead of passenger comfort.

2.  The pax DO NOT CARE.  I commuted for almost 16 years which means I rode in the back twice a week (when I wasn't in the jumpseat), and I observed this over and over. The passengers do not care or even seem to notice things like speed brakes or a gear extension at 250, etc.  No one looks up.  No one pauses their conversation. The flying pilot might be up there twisting himself into knots of distraction, trying to find a way to magically add drag to the plane without actually adding drag to the plane... but NO ONE ELSE CARES lol.  (They also care nothing about standard PAs... they just want you to shut up so they can finish their phone call before the door closes, or finish their movies in flight before the stream gets shut down on landing.)