Hi Everybody,

Are there any other PMDG 737-800 users that are having an issue with the reverse thrust taking an extended period of time to accelerate to 80%N1? You can see in the video (jump to 59:25), the throttles are being reduced to idle at 20', the upper mfd gauges show the engines to be at idle upon touchdown, I extend the speed brake and pull up the engine reversers, it then takes several seconds for the engines to spool up to 80% N1.

I posted in the PMDG forum, only response so far was how the autobrake works and that AB2 wasn't aggressive enough, yet Topcat shows AB2 as fine. As well as the possibility of my landing technique as the possible cause.

Is it me? Am I wrong here? Are these engine reversers working correctly?

Jump to 59:25

Thanks Everyone

 

Edited September 14, 20232 yr by Mike_CFII_MEL

First, I want your sim. I know I saw it a couple weeks ago in another thread but... Man, every time it just blows me away.

 

The video resolution is way too low to really see what your engines are doing or your speeds, and the camera position makes everything look weird so I'm probably way off base here, but it looked like you were coming in pretty fast, but also low, so it's possible you were throttled up enough that you weren't truly at idle when you touched down. At least in MSFS, reversers will not engage at all until the engine spools all the way to idle (at least, that I've experienced). 

That aside, it did look/sound like the reversers sat around for awhile before deciding to obey your input. What are you using as a control interface to the sim, and how do you have the reversers behaving? I've seen some schemes where reverse is engaged when a "button press" is held, but then the hold time is defined as a second or two, which causes significant delays. 

Is your throttle reverse like most of them, just really a button, or is it an actual separate axis? If your control interpreter is the one inside the sim, I'd recommend moving over to something like SPAD.NeXt. It gives you a lot more flexibility for how control inputs behave and you should be able to get around whatever is causing the delay.

I've definitely never noticed a delay in the PMDG 737 like that, and that's with much lower-grade hardware than you have.

One workaround you could do in the meanwhile is to hit the reverse levers before you hit the spoiler lever. By the time the spoiler is out, the reversers should be at least starting to engage.

 

 

Oh this is interesting, I looked at the beginning of the video where you used reversers to exit the gate (lol) and the delay was there as well. So definitely doesn't have anything to do with engines spooling down. I'm guessing the delay is somewhere in your control interface setup.

32 minutes ago, Mike_CFII_MEL said:

it then takes several seconds for the engines to spool up to 80% N1.

Yup, that's to be expected.
It takes around 6 seconds to spool from idle to max on the CFM56-3s, per here.

I think you are being influenced by the short runway length you were faced with in your linked video.

If you're unsure, just test your throttle quadrant's reverser levers in the MSFS Controller settings page and/or your TQ's controller own settings app. Also, you can perform an 'engine run-up test' with the reversers while parked.

Just for some extra info, read here.

Finally, the comment from the PMDG forum is correct. The 737 autobrake is a little anaemic compared to the A320.
Deceleration rate on AB1 is only 4 ft/sec², AB2 is only 5 ft/sec², AB3 is only 7.2 ft/sec², MAX is 14 ft/sec² above 80 kts.
The A320 manages 5.5 ft/sec² on LO and 9.8 ft/sec² on MED.

That's not to forget that it takes 3 seconds for the 737's autobrakes to apply full pressure for the selected autobrake setting.

Source: http://www.b737.org.uk/landinggear.htm

1 hour ago, Mike_CFII_MEL said:

Is it me? Am I wrong here? Are these engine reversers working correctly?

Jump to 59:25

Thanks Everyone

 

Something is wrong, on the 737 you can deploy reversers at or below 10 FT RA. If you have FSUIPC you need to change this entry:

 

[Axes]

PollInterval=10

RangeRepeatRate=10

 

[Buttons]

PollInterval=25

ButtonRepeat=20,0

 

This "ButtonRepeat=20,0  " should kill that delay for reversers and also the delay on the electrical trim.

Edited September 14, 20232 yr by LRBS

17 minutes ago, eslader said:

What are you using as a control interface to the sim, and how do you have the reversers behaving? I've seen some schemes where reverse is engaged when a "button press" is held, but then the hold time is defined as a second or two, which causes significant delays. 

Is your throttle reverse like most of them, just really a button, or is it an actual separate axis?

Hi,

They are push button reversers, they don't have an axis. I'm using FSUIPC7 to control the reversers push buttons as MS2020 don't seem to work correctly at all.

19 minutes ago, eslader said:

Oh this is interesting, I looked at the beginning of the video where you used reversers to exit the gate (lol) and the delay was there as well. So definitely doesn't have anything to do with engines spooling down. I'm guessing the delay is somewhere in your control interface setup.

Hi,

You know I never thought of looking at that! That was a great idea.

20 minutes ago, F737MAX said:

Yup, that's to be expected.
It takes around 6 seconds to spool from idle to max on the CFM56-3s, per here.

Hi,

This I get, but it seems as though forfour of the six seconds they are completely dead and then it jump to 80% in a second or two.

Edited September 14, 20232 yr by Mike_CFII_MEL

9 minutes ago, LRBS said:

Something is wrong, on the 737 you can deploy reversers at or below 10 FT RA. If you have FSUIPC you need to change this entry:

 

[Axes]

PollInterval=10

RangeRepeatRate=10

 

[Buttons]

PollInterval=25

ButtonRepeat=20,0

 

This "ButtonRepeat=20,0  " should kill that delay for reversers and also the delay on the electrical trim.

Hi,

I'm using FSUIPC7, I'll take a look at this.

Thanks everyone!

34 minutes ago, F737MAX said:

Yup, that's to be expected.
It takes around 6 seconds to spool from idle to max on the CFM56-3s, per here.

 

It looked like about a 2-4 second delay before the reversers even started to spool to me. 

16 minutes ago, Mike_CFII_MEL said:

Hi,

They are push button reversers, they don't have an axis. I'm using FSUIPC7 to control the reversers push buttons as MS2020 don't seem to work correctly at all.

OK, yeah. I'd check out SPAD then - there's a free trial you can do for 2 weeks to test it. Reversers/beta in MSFS is one of the best things SPAD does for me, because seemingly every plane wants a different input for them, and some even have bizarre bugs that cause physics-defying behavior which you have to edit out in the control input handling. 

Hi LRBS,

That's the fix! I had the following in FSUIPC7 ButtonRepeat=20,10, after changing it to ButtonRepeat=20,0 the problem is gone.

Thanks
 

2 minutes ago, Mike_CFII_MEL said:

Hi LRBS,

That's the fix! I had the following in FSUIPC7 ButtonRepeat=20,10, after changing it to ButtonRepeat=20,0 the problem is gone.

Thanks
 

Any time Mike. Happy to help. Also, you will notice no delay on electrical trim, like in the real airplane.

Edited September 14, 20232 yr by LRBS

2 hours ago, F737MAX said:

Deceleration rate on AB1 is only 4 ft/sec², AB2 is only 5 ft/sec², AB3 is only 7.2 ft/sec², MAX is 14 ft/sec² above 80 kts.

Source: http://www.b737.org.uk/landinggear.htm

Just for clarification, the 80 KTS, actually 90,  you mentioned, is only for RTO when it becomes active and is max pressure and deceleration rate. Nothing to do with AB1, AB2, AB3, or MAX used for landing.

 

 

 

Edited September 15, 20232 yr by LRBS

It's probably also worth mentioning that IRL, there's a ~2 sec delay after pulling the reverser levers up to the interlock stop while the sleeves and blocker doors open, and then the interlock releases and only then can you select reverse thrust above idle reverse.  While the amber "REV" is indicated above the N1 gauges, the interlock will be engaged...you wouldn't be able to get the levers past reverse idle until the indications turn green, indicating the doors are open.  So ripping them all the way back as seen in the video can't happen.  I physically pull them up to reverse idle...wait a couple potatoes for the green "REV"  lights, then add reverse as needed. 

In some scenarios (unsure about how it's done in the PMDG 737 in MSFS), you get forward thrust applied by the flight model before the engines are toggled to reverse mode, which can make those rollouts verrrry long.

55 minutes ago, Bob Scott said:

It's probably also worth mentioning that IRL, there's a ~2 sec delay after pulling the reverser levers up to the interlock stop while the sleeves and blocker doors open, and then the interlock releases and only then can you select reverse thrust above idle reverse.  While the amber "REV" is indicated above the N1 gauges, the interlock will be engaged...you wouldn't be able to get the levers past reverse idle until the indications turn green, indicating the doors are open.  So ripping them all the way back as seen in the video can't happen.  I physically pull them up to reverse idle...wait a couple potatoes for the green "REV"  lights, then add reverse as needed. 

In some scenarios (unsure about how it's done in the PMDG 737 in MSFS), you get forward thrust applied by the flight model before the engines are toggled to reverse mode, which can make those rollouts verrrry long.

Hi,

 

My reversers are pushbutton, so if I only go part way, nothing will happen. Some day I'll have a motorized throttle quad from FDS.