11 hours ago, Mike_CFII_MEL said:

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.

Wow, I would have thought that FDS quadrant would have a true axis for the reversers, or at least several microswitches in the rev range to correspond to the actual 737 reverse detents, rather than an all-or-nothing single button input.

You might want to look close and check to see if the N1 is advancing prior to the green REV light when sending a rapidly repeating sequence of throttle cut keystrokes...if so, having the button trigger a Lua script that presses once, then delays for a couple seconds while the reversers deploy, then presses a few more times to get to full reverse will prevent getting increased forward thrust before the reversers are fully deployed.

The PMDG 737 has an option in the FMC "approach idle" (higher idle n1 once the gear is down for landing, for go-around performance purposes, this is realistic). If this is enabled, the 737 will take longer after touchdown before the reversers engage/spool up because it has to go down to "normal idle" after touchdown before the reversers can be spooled up. This is a sim/PMDG-limitation and not realistic, but it is the cause for anything delayed with reversers.

EDIT: In real life the reversers can be deployed from approach idle without any problems.

Edited September 15, 20232 yr by Fiorentoni

17 minutes ago, Fiorentoni said:

The PMDG 737 has an option in the FMC "approach idle" (higher idle n1 once the gear is down for landing, for go-around performance purposes, this is realistic). If this is enabled, the 737 will take longer after touchdown before the reversers engage/spool up because it has to go down to "normal idle" after touchdown before the reversers can be spooled up. This is a sim/PMDG-limitation and not realistic, but it is the cause for anything delayed with reversers.

EDIT: In real life the reversers can be deployed from approach idle without any problems.

And IRL there's a significant difference between spooling up the reversers from full idle as opposed to from approach idle--11 seconds from full idle vs 6 seconds from approach idle, which is why there's a delay programmed in before the engine will spool down from approach idle to full idle after touchdown, and why you shouldn't come out of reverse until reaching safe taxi speed, just in case you need to use them again.

15 hours 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.

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.

Keep in mind that most modern aircraft to include the 737 have high and low idle settings mostly driven my configuration. Once configured and on approach, the FADEC will drive a higher idle to assist with faster spool up for go around and reversers. The high idle will be held for about 4 seconds or so after touch down before going back to low ground idle. I think the 737s high idle is at 32%. Either way, the high idle allows a fast spool up verses all the seconds it will take going from low idle.

15 hours ago, LRBS said:

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.

I'm just going with what the 737 site told me, guv'nor

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

 

  

1 hour ago, G550flyer said:

Keep in mind that most modern aircraft to include the 737 have high and low idle settings mostly driven my configuration. Once configured and on approach, the FADEC will drive a higher idle to assist with faster spool up for go around and reversers. The high idle will be held for about 4 seconds or so after touch down before going back to low ground idle. I think the 737s high idle is at 32%. Either way, the high idle allows a fast spool up verses all the seconds it will take going from low idle.

Ah, I had thought fast idle was cancelled when the MLG touches down and the interlocks released.
Turns out not only does high idle remain active for 4 seconds, but the reversers are unlocked at < 10 feet rad alt.

Everyday is a school day!
 

Edited September 15, 20232 yr by F737MAX

2 hours ago, Bob Scott said:

Wow, I would have thought that FDS quadrant would have a true axis for the reversers, or at least several microswitches in the rev range to correspond to the actual 737 reverse detents, rather than an all-or-nothing single button input.

Hi Bob,

The throttle quad was made by Jetmax 8+ years ago, not FDS, even though Jetmax was an offshoot FDS company, with that said the quality of material wasn't as nice (as reflected in the  lower price range) as FDS products. They later sold that part of the business.

As for the engine spooling down as being the issue... I think LRBS hit the nail on the head when he noticed that the reversers take an extended period of time to spool up even when at the gate backing out where there is no spool down to idle one has to wait to complete.

I'll take a look at the FMC for the fast idle option.

Thanks everyone! 

6 hours ago, F737MAX said:

I'm just going with what the 737 site told me, guv'nor

Everyday is a school day!
 

I understand; I was highlighting that for the RTO  to be armed, the airplane needs to be at or above 90 KTS GS to be active, while that web page doesn't mention anything about it. I really don't know where that 80 KTS is coming from, nor to be found in FCTM or FCOM. Sometimes, manufacturer books can be confusing or lack proper explanation, leading to individual interpretations.

Every flight is an opportunity to learn and improve in this business. I am still learning even though I am only 20 months away from retirement.