PMDG 737-700 Update to Build 3.00.0031

[Fiorentoni 4,479]

3 minutes ago, Cpt_Piett said:

I'm used to this on the Airbus, being in managed speed mode and at the "green dot" speed before going flaps 1. But what about on the -700? If you're in VNAV SPD mode below 10,000, I guess the usual speed is 250 or 240. But you can't go flaps one from that speed? Or, how do you do this in practice?

I think you're mixing together several things. Green dot speed is basically the clean speed (mininum speed without flaps) for the A320. There's a clean speed for the 737 too, mostly around 200 kts.
For the 737 you can go flaps 1 to 5 from 250 kts downwards without damaging the flaps, but why would you in a normal approach? You do the same as in the Airbus: You go down to clean speed 10 miles out, go flaps 1 (or 5), VNAV will command a lower speed (minimum speed for flaps 1 [or 5]).
Only difference is that once you intercepted the glideslope your speed is manually set (speed window open), while the Airbus in managed mode lowers speed itself to the F speed and Vapp thereafter.

[threexgreen 3,160]

5 minutes ago, Cpt_Piett said:

I'm used to this on the Airbus, being in managed speed mode and at the "green dot" speed before going flaps 1. But what about on the -700? If you're in VNAV SPD mode below 10,000, I guess the usual speed is 250 or 240. But you can't go flaps one from that speed? Or, how do you do this in practice?

Suppose you're on approach in VNAV with FMC SPD annunciated on the FMA. If you extent the flaps now, VNAV will automatically command the respective flap maneuvering speed for that flap setting. All you need to do is move the flap handle; you don't need to adjust speed yourself. This works pretty much like in the Airbus.

You can extend flaps on the NG below 250 kts as that's the limit speed for 1, 2 and 5, although most if not all operators limit that further to 10 kts below limit speed to allow some margin to flap overspeed. So in this case, if you go to flaps 1 at 240 kts, the airplane automatically drops the target speed to flap 1 maneuvering speed. Many times you'll be slower at that point but it's fine to extend flaps below 240 kts if you need the drag.

[Fiorentoni 4,479]

33 minutes ago, MySound said:

It seems to me that speedbrake usage is also an airline specific thing. 
I fly Lufthansa and TAROM quite often and they rarely use the speedbrake. 
Could be related to CI also.

But every single Emirates flight I had until now - they dive down like crazy and apply speedbrake almost all the time. Had 6 flights until now with them, A380 and 777-300ER. And it’s always the same. 🙂

While good pre-planning can mostly avoid speedbrake usage, this is not always possible and depends a lot on the airport and the ATC and - important - your knowledge of both. Long haul pilots don't fly nearly as often as their A320/737 colleagues, so they often lack the knowledge about what to expect from certain locations. On the other hand flying twice to Mallorca week in week out... you won't be suprised by ATC.
CI can be a part of it, because a high CI means you're descending late and fast, so if ATC gives you an unexpected shortcut, you might need the speedbrakes.

[Cpt_Piett 4,921]

19 minutes ago, Fiorentoni said:

I think you're mixing together several things. 

What I meant is that in the Airbus, after activating the approach phase, the plane will slow to green dot speed, then I start extending the flaps. And the flap speeds will be automatically set. 

In the 737, I've always set the speed manually, to say 200-210 kts, then after lowering flaps I lower the speed manually. 

19 minutes ago, threegreen said:

Suppose you're on approach in VNAV with FMC SPD annunciated on the FMA. If you extent the flaps now, VNAV will automatically command the respective flap maneuvering speed for that flap setting. All you need to do is move the flap handle; you don't need to adjust speed yourself. This works pretty much like in the Airbus.

Thanks, I think I get it. I'll try this on my next -700 flight. Thanks both of you for the detailed explanations. 

[Stearmandriver 2,335]

1 hour ago, jarmstro said:

What's the point of VNAV then? From what you say it's of no practical use? Do RW pilots actually bother with it?

VNAV is the most often used flight guidance mode in a descent (though certainly not the only one, and it is at the discretion of the PF to choose what they feel is appropriate to the circumstance.)

VNAV provides speed and altitude protections that other modes do not, though, and so staying in VNAV to the extent practical is a good idea. 

The most frequent initial descent clearance given in U.S. airspace is "pilot's discretion", meaning that the pilot flying can choose when to start down.  This is why VNAV is used: it will start down at its computed TOD.  Further on, the descent will likely be converted to a "descend via" (as most airline airports in the US use those now).  So if you've got the arrival with all restrictions loaded in the box appropriately and are already descending in VNAV, you're already on the path and just need to set the bottom altitude in the MCP.

ATC will sometimes (or often) modify your descent at some point, and/or the actual wind will be a little different than forecast, requiring the use of speed brakes or a thrust addition... but in a perfect world with good data and no modification, the idea is to stay high as long as possible, and then fly an idle-path descent.  This is what VNAV tries to accomplish, and that's how the TOD is used.

Edited July 31, 2022 by Stearmandriver

[MySound 410]

14 hours ago, Fiorentoni said:

While good pre-planning can mostly avoid speedbrake usage, this is not always possible and depends a lot on the airport and the ATC and - important - your knowledge of both. Long haul pilots don't fly nearly as often as their A320/737 colleagues, so they often lack the knowledge about what to expect from certain locations. On the other hand flying twice to Mallorca week in week out... you won't be suprised by ATC.
CI can be a part of it, because a high CI means you're descending late and fast, so if ATC gives you an unexpected shortcut, you might need the speedbrakes.

Well,

the A350 colleagues at Lufthansa also didnt use the speed brakes (Munich - Dubai - Munich). I mean, I understand how ATC and preplanning work - but still I have the feeling that some airlines fly more "aggressive" than others.

Edited August 1, 2022 by MySound

[Fiorentoni 4,479]

49 minutes ago, MySound said:

Well,

the A350 colleagues at Lufthansa also didnt use the speed brakes (Munich - Dubai - Munich). I mean, I understand how ATC and preplanning work - but still I have the feeling that some airlines fly more "aggressive" than others.

Why would they do that? There's nothing to gain from descending late and putting out the speedbrake. You'll use MUCH more fuel if you descent too late and you won't be any faster either. It's pointless. If anything it would be a sign of incompetence, but I doubt that Emirates has only incompetent people flying their big aircraft

[MarkW 1,502]

On 7/30/2022 at 8:46 AM, MDFlier said:

I've been flying Baltimore to Myrtle Beach quite a bit lately. It's short enough to complete in about an hour and a half. I've always been assigned an ILS 18 approach via CRE. It requires a hold with a teardrop entry at UXDEP. Prior to this update, the 700 could not fly it without help. Left on it's own, it would turn right prior to UXDEP and circle around but never enter the hold. It was a mess. To make the plane fly it correctly, I had to engage heading mode and fly heading 288 until it passed UXDEP and then re-engage LNAV so that it would enter the hold. The Fenix would do a proper teardrop entry, and now the 700 flies it perfectly as well.

If you're not sure why they had to fix it, try this flight before you update, and then fly it again after updating.

KBWI CONLE4 SCOOB..ILM..WYLMS..KMYR

It’s cool that it does this however checking real world SWA flights on this route they never fly it and seem to get vectors for straight in. 

[chapstick 2,767]

4 minutes ago, MarkW said:

It’s cool that it does this however checking real world SWA flights on this route they never fly it and seem to get vectors for straight in. 

...and that matters why? The guy wants to fly the full instrument procedure. That's kind of the point of using flight simulators. 

[MDFlier 2,031]

I don't always fly the full approach with the hold. I only did it the 1st time because ATC assigned me the CRE transition and I hit the wrong key. I accidentally accepted the approach when my intention was to request the "vectors to" approach for an ILS 18 landing, so I just flew what I had accepted. This was in the 737 and it totally screwed the pooch on the entry to the hold. I repeated the flight in the Fenix, and it properly flew it. After the PMDG update, I flew it the 3rd time to see if it was fixed, and it is. I'm pretty sure I'll fly it the same as SWA does from now on.

[bobcat999 8,542]

On 7/30/2022 at 9:53 PM, Stearmandriver said:

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.)

Makes perfect sense.  I am glad you are around to tell it how it is!

[threexgreen 3,160]

4 hours ago, Fiorentoni said:

If anything it would be a sign of incompetence, but I doubt that Emirates has only incompetent people flying their big aircraft

Hence the assumption there may be some airline policy involved. I can't comment on whatever Emirates is doing, but the usage of speedbrake will increase the descent rate enabling you to stay higher a bit longer where you burn less fuel. I think the instances that the poster witnessed were possibly just coincidence regarding speedbrake usage, but as discussed the goal is to stay higher longer so speedbrake usage would benefit that. I don't think I've ever seen a policy like that though.

One example is the fuel efficiency policy of a big US carrier not to use any climb derates, even when the FMC auto-selects a derated climb depending on takeoff thrust used, but utilize the full climb thrust available to maximize the rate of climb to the higher levels where fuel burn goes down. Descending with the speedbrake out would at least theoretically fit the same principle, though the question is how many times you can actually freely descent without any restrictions or ATC intervention possibly offsetting the benefit gained.

[Fiorentoni 4,479]

3 minutes ago, threegreen said:

Hence the assumption there may be some airline policy involved. I can't comment on whatever Emirates is doing, but the usage of speedbrake will increase the descent rate enabling you to stay higher a bit longer where you burn less fuel. I think the instances that the poster witnessed were possibly just coincidence regarding speedbrake usage, but as discussed the goal is to stay higher longer so speedbrake usage would benefit that. I don't think I've ever seen a policy like that though.

One example is the fuel efficiency policy of a big US carrier not to use any climb derates, even when the FMC auto-selects a derated climb depending on takeoff thrust used, but utilize the full climb thrust available to maximize the rate of climb to the higher levels where fuel burn goes down. Descending with the speedbrake out would at least theoretically fit the same principle, though the question is how many times you can actually freely descent without any restrictions or ATC intervention possibly offsetting the benefit gained.

No that would be absurd. To save fuel you descend early, not late (that's why a low cost index leads to early and slow descents). No matter how high you fly, your fuel usage will always be much higher on cruise than on idle descent, obviously, so if you want to save fuel, you maximize the idle descent phase.
Using the speedbrake you bleed off energy which you have just gained by burning fuel (to stay longer on cruise level) - that means literally burning fuel for nothing. There's no way using the speedbrake could be part of any company policy.

The climb thing you talk about is something entirely different, because you are obviously not idle climbing, so the quicker you climb to higher flight levels the less fuel you use (which is why a low CI leads to lower climb speeds on a higher climb rate). But that's an entirely different principle.
Also climb derates are supposed to save on engine wear and tear (and noise abatement sometimes), but of course it's part of the company's calculation how much more fuel a climb derate costs you in comparison to the lower engine replacement costs. On the 737 the airlines I know either don't use derated climbs or delete the derated climb at 10000 feet (I suppose that the positive effects on engine life disappear in thinner air).

[threexgreen 3,160]

21 minutes ago, Fiorentoni said:

To save fuel you descend early, not late (that's why a low cost index leads to early and slow descents).

Yes, you're right. Not my brightest moment.

[Sylle 49]

On 7/31/2022 at 11:05 PM, Cpt_Piett said:

What I meant is that in the Airbus, after activating the approach phase, the plane will slow to green dot speed, then I start extending the flaps. And the flap speeds will be automatically set. 

In the 737, I've always set the speed manually, to say 200-210 kts, then after lowering flaps I lower the speed manually. 

Thanks, I think I get it. I'll try this on my next -700 flight. Thanks both of you for the detailed explanations. 

Hi Piett,

the 737 VNAV automatically transitions to ‘on approach logic’ when you get close to your final approach fix.
No need to activate anything like on the Bus. 
 

Also no need to extend the flaps at speeds of 240kts or to go out of VNAV to manually lower the MCP speed either…

A/ At around 30-40 track miles remaining you will see 2 green dots on the ND. Those indicate the position where VNAV will decelerate from your ECON descent speed to the speed restriction below 10000ft defined in the DES page (240kts by default). 

B/ Around 15 track miles remaining you will see a green DECEL point on the ND. 
That’s the point where VNAV will start decelerating from 240kts (to try) to hit the speed + altitude restriction at the final approach fix or outer marker or equivalent position.
(Every approach should contain at least 1 point with a hard constraint for speed and altitude defined in the database - the FMC needs it to calculate its descent profile because it calculates from the approach backwards to ToD)

Watch the speed decrease after DECEL and start extending flaps when you are 10-20kts above the green UP on the speedtape. 
If you fail to extend flaps VNAV will not decelerate below UP speed. 
 

If you need to decelerate faster, use the speedbrakes or drop the gear like Stearmandriver said. 
Extending the flaps at 240kts to decelerate is rather useless as the first stages of flaps create more lift than drag…

Hope this helps,
Sylvain