Mustang Jumps The Chocks On Restart

[MkIV Hvd]

I know this has been mentioned before but I think related to a different issue, so was never followed up on. If the airplane is left parked after a flight with the sim running, on restart it will jump the chocks and/or blow through the park brake, until stopped by pumping brakes to regain control. It also happens when the chocks and park brake are engaged, as well as when just holding the brakes manually. I used to think it only happened when I flooded it on restart after having left it parked with the sim running for a period of time, but have been doing some contiguous trips lately and it is a constant issue. I've left the airplane parked for hours at times and I've learned to park it not pointed at anything hard, because even on a normal (not flooded) start it *will* jump forward.

I initially wrote it off as a unique issue to my setup because I don't think it was ever pursued or mentioned by anyone else, but it has been a constant issue for me through the migration from FSX --> FSX:SE --> P3Dv4.5 --> P3Dv5.2 on three different computers, so I'm hoping the issue might be able to be duplicated and solved? I've never thought to make a video, but could certainly do that if the thing is unduplicatable for others...

Thanks in advance & Cheers,
Rob

[DHenriques_]

I know this has been mentioned before but I think related to a different issue, so was never followed up on. If the airplane is left parked after a flight with the sim running, on restart it will jump the chocks and/or blow through the park brake, until stopped by pumping brakes to regain control. It also happens when the chocks and park brake are engaged, as well as when just holding the brakes manually. I used to think it only happened when I flooded it on restart after having left it parked with the sim running for a period of time, but have been doing some contiguous trips lately and it is a constant issue. I've left the airplane parked for hours at times and I've learned to park it not pointed at anything hard, because even on a normal (not flooded) start it *will* jump forward.

I initially wrote it off as a unique issue to my setup because I don't think it was ever pursued or mentioned by anyone else, but it has been a constant issue for me through the migration from FSX --> FSX:SE --> P3Dv4.5 --> P3Dv5.2 on three different computers, so I'm hoping the issue might be able to be duplicated and solved? I've never thought to make a video, but could certainly do that if the thing is unduplicatable for others...

Thanks in advance & Cheers,
Rob

Interesting ! Did you happen to notice if there was a manifold pressure surge involved with the restart? I remember mentioning to Scott when we were doing the flight model that the 51 will jump the chocks at 40 inches but I don't think we ever coded that into the sim.
Dudley

[MkIV Hvd]

Interesting ! Did you happen to notice if there was a manifold pressure surge involved with the restart? I remember mentioning to Scott when we were doing the flight model that the 51 will jump the chocks at 40 inches but I don't think we ever coded that into the sim.
Dudley

Thanks Dudley, as I mentioned, when this initially happened to me it was on a flooded start so there was a surge to some extent...I don't think anywhere near 40" though...I've had to do it enough that I'm pretty quick at pulling the throttle back

The last time it happened, it was a normal start with the temperatures all cooled to ambient and instead of setting chocks and park brake I just held the brakes...it jumped ahead and I had to pump the brakes a couple of times to get it stopped.

Cheers,
Rob

[DHenriques_]

Interesting ! Did you happen to notice if there was a manifold pressure surge involved with the restart? I remember mentioning to Scott when we were doing the flight model that the 51 will jump the chocks at 40 inches but I don't think we ever coded that into the sim.
Dudley

Thanks Dudley, as I mentioned, when this initially happened to me it was on a flooded start so there was a surge to some extent...I don't think anywhere near 40" though...I've had to do it enough that I'm pretty quick at pulling the throttle back

The last time it happened, it was a normal start with the temperatures all cooled to ambient and instead of setting chocks and park brake I just held the brakes...it jumped ahead and I had to pump the brakes a couple of times to get it stopped.

Cheers,
Rob

Sounds like it could be something hanging up in the settings when you shut down that kicks in at a higher value on the restart.
I hate to say it but I'll bet the farm that a simple uninstall and reinstall will fix it along with a data file deletion.
That seems to fix a LOT of issues.
D

[MkIV Hvd]

Sounds like it could be something hanging up in the settings when you shut down that kicks in at a higher value on the restart.
I hate to say it but I'll bet the farm that a simple uninstall and reinstall will fix it along with a data file deletion.
That seems to fix a LOT of issues.
D

I suppose anything's possible, but I'd sure like confirmation from someone that this does or does not occur for them before I head down the uninstall/reinstall path...it's actually not a make it or break it, but it would be nice to be able to restart without this happening. I flew yesterday from Redding to Can Carlos, left the airplane parked on the ramp for 4½ hours and recorded the start. It turns out I actually did flood it initially (it didn't like the 4 shots of prime at 32°C apparently), but the surge when it started should not have overridden the chocks and park brake. Note that when it happens, the park brake is still showing set and standing on the brakes is ineffective...they have to be pumped to disengage the park brake, that is now having no effect whatsoever...thus the extended roll after the event and turn to the left to avoid the Cessna.



I have been factory programmed by A2A to *not* uninstall/reinstall as a first step and I don't have a farm to bet but given that this issue has existed across 3 different sim platforms and three different computers I'd certainly be willing to bet a case of beer that there's something else going on. If it's unique to me, then oh well...

Cheers,
Rob

[DHenriques_]

The only thing I see that could be an issue involves pushing the throttle forward before the start.
I can't remember if we programmed in the exact effect of a Simmons regulated throttle on our Merlin but if we did and you started a Mustang with the throttle forward of a few inches the start could result in an engine surge almost exactly like this.
My memory isn't that sharp on how we coded the Simmons. Perhaps Scott or Lewis could comment if you pinged them.
On the reinstall...........I've never noticed anything special about doing that. During testing we did it all the time. The whole process only took a few minutes. No big deal at all.
D

[MkIV Hvd]

The only thing I see that could be an issue involves pushing the throttle forward before the start.
I can't remember if we programmed in the exact effect of a Simmons regulated throttle on our Merlin but if we did and you started a Mustang with the throttle forward of a few inches the start could result in an engine surge almost exactly like this.
My memory isn't that sharp on how we coded the Simmons. Perhaps Scott or Lewis could comment if you pinged them.
On the reinstall...........I've never noticed anything special about doing that. During testing we did it all the time. The whole process only took a few minutes. No big deal at all.
D

Thanks Dudley, I start the Mustang the same way every time and because I flooded it, I started with the throttle full forward this time, but the engine surge is not the issue...it never does this unless it has been parked with the sim running for a while. The real issue here is, "Why would a minor surge like that cause it to jump forward, out of control, when the chocks were in place and the park brake was set?"...

[DHenriques_]

Sounds like something corrupted to me. Have you tried deleting any saved flights for the 51 and the data files? I understand doing that fixes a lot of issues.
D

[MkIV Hvd]

I have never saved a flight with the Mustang or any other A2A airplane across any of the three sim platforms on which I've noticed this issue. Again...three sim platforms, three different computers in the last two years and the issue has been consistent. Also as I said, it happens not only a flooded start where the engine surges a bit, but on a completely normal start after the airplane has been sitting for a while.

If there is installation corruption, then it has happened with every Mustang installation I've ever accomplished...likely 8 or so. That seems a bit far fetched to me, but I think the only practical path to a solution would be for someone to actually try it on another computer and see what happens, if someone is willing.

[DHenriques_]

I have never saved a flight with the Mustang or any other A2A airplane across any of the three sim platforms on which I've noticed this issue. Again...three sim platforms, three different computers in the last two years and the issue has been consistent. Also as I said, it happens not only a flooded start where the engine surges a bit, but on a completely normal start after the airplane has been sitting for a while.

If there is installation corruption, then it has happened with every Mustang installation I've ever accomplished...likely 8 or so. That seems a bit far fetched to me, but I think the only practical path to a solution would be for someone to actually try it on another computer and see what happens, if someone is willing.

Three different platforms and three different computers?
I'm assuming you have used the same installation executable all this time?
Just a wild ass guess here but if this has been the case I'm guessing that something has been carried forward as an issue with each installation.
I can't make a decision for you but if this was my issue I wouldn't hesitate at this point to get a fresh copy of the Mustang, uninstall the present installation and all the data files associated with it and install a NEW copy along with the updates if required.
It's just me I guess. Once I've decided that an issue is local (and 99% of them are), I would simply download a new copy of whatever plane is involved and get a fresh new start.
It seems obvious to me (I could be wrong. Been wrong before that whatever this issue is involves your saved and reused installation executable file. Lewis would be the go-to guy on that but this would be my opinion. I base this on the fact that the issue has carried forward so many times and on several computers as you have stated.
Other than that I'm at a loss to nail down what specifically might be the problem here.
As always, best of luck with this. Ping Lewis and see what he says.
D

[WB_FlashOver]

Been watching this but not much to offer. I have had the Mustang lurch forward on occasion as well but it was always pilot error. Maybe I had the throttle too high or maybe I had primed a tiny bit too long. Watching your video I can say that I have never started the engine with throttle at full. That would seem to be in direct correlation to what you are experiencing. I have found that after an update several years ago the suggested 4 seconds of priming is way too much now-a-days. With the OAT as shown in your video, and the fact that you had flown it recently without sim restart, I would be tempted to give 1-2 seconds primer and then "tickle" it as your cranking.

One other item that I have found to be important is to restart sim after each flight. I don't always do this but it is good to clear things out of memory when possible. Currently I'm landing on every airfield in the South Pacific in the B-17 and many fields are a mere 30 NM apart so I have not been restarting each time. Just taxi back, idle into the wind long enough for engines to cool, and take-off for next field. I do this for 3-4 legs then restart sim and even PC before the next legs.

On what Dudley has suggested I have one question. Have you been using the data file for your P51 throughout these PC and Sim upgrades? If so try removing the file < P51civLog.dat > from ~\Documents\A2A\FSX\P51Civ folder. Move it to desktop, let A2A build a new one during a flight, test. If the issue persists then put your original back in so you don't loose your hours.

Good luck Sir
Roger

[Paughco]

After reviewing the video, I believe that the chock jumping thing is due to starting at wide open throttle. No matter how quickly you retard the throttle, there's enough fuel/air already in the engine to let that Mustang want to boogie!

Watch this video between minutes 3 and 5 for the startup portion: https://www.youtube.com/watch?v=QtFeJ-y ... x=5&t=188s. I think the whole video is good.

Priming time is somewhat critical. I read this in a post by Dudley (https://www.a2asimulations.com/forum/vi ... 93&t=32607), with some additional notes on priming from Scott:
***************************************
COLD STARTING TIP

I want to add a tip for cold weather starting

The effect of cold weather for primer in our Accu-Sim birds may be too high (not sure as there really isn't a lot of data / experience since we all heat our engines up these days in cold weather and pilot's manuals have conflicting information). There is some data showing it becoming almost ineffective at only moderately sub freezing conditions, yet other data is simply too vague so we may be on the money here, just not sure still. So we are still researching this.

Looking at the actual code using the primer, I'm showing on the current P-51:
- Over 50 deg F (hold primer for 2-4 sec)
- 30 - 50 deg (hold primer for 4-8 sec)
- under 30 deg (hold primer for 12 sec)

Scott.
*****************************************

That time vs. ambient temp bit came in really handy when we were trying to start our Mustangs up at Barrow, AK last November. That was the start of our epic MP flight from Barrow, AK down to the southern tip of South America, all in P-51s.

Another thing I've seen work with a flooded engine is the "do-over." That's where you hit Shift+3 and select Cold & Dark. The airplane is instantly transformed into cold & dark, with no flooding, the fuel valve off, controls locked, etc.

Hope that helps.

Seeya
ATB

[Jacques]

Hi Rob, you’re not crazy…or alone! The P-51 will leap forward regardless of chocks or the parking brake when I re-start the aircraft in the same session. I don’t know if this can be seen on an immediate restart or if some small amount of time needs to pass. Regardless, the best way to avoid scooting halfway across the airport on your mid-session restart is to use minimal throttle and minimal or no priming (as Paughco points out above) …and be ready to get on the brakes.

[MkIV Hvd]

Gentlemen, thanks very much for the time and effort put into helping me address this!

The bottom line is: it’s not about start procedure, it’s about the fact that this never happens on the initial start of a sim session…normal start, cold start, flooded start…this does not happen…only on a restart within the same sim session. The issue is the fact that the park brake and/or chocks or manual brake application will not stop the surge forward and then the brakes act like they need a few seconds to get their act together before they’ll actually stop the airplane…hence the excessively long roll after the event!

This particular start I flooded it, but it will do the same thing on a normal start.

For clarification, the procedure of starting a flooded engine has not changed in a long time…for a car, it’s throttle wide open with the choke propped open…in an airplane, it’s throttle wide open, mixture to idle cutoff until the start, then quickly reverse the throttle/mixture levers. It’s an abnormal but common start procedure that works…it’s also not the issue here. Also please note that the RPM did not go above 1400 and was only there for a fraction of a second. You can do a runup in the Mustang on the park brake at 2300 rpm and it holds just fine (I don’t trust it, but have tried it to see how well the park brake works ), so there’s no reason at all that it should not hold during a start like this one. Note that when the airplane moves, the park brake is still showing that it’s SET until the brakes are pumped to kick it off and get control back…again, hence the long roll and need to turn to avoid a collision. It is NOT a start procedure issue…it is a “brakes will not hold on a restart” issue…

By the way, I’ve successfully used the same procedure on real world Harvards and Cherokees…all of which just started without all the drama…

Three different platforms and three different computers?
I'm assuming you have used the same installation executable all this time?
Just a wild ass guess here but if this has been the case I'm guessing that something has been carried forward as an issue with each installation.
I can't make a decision for you but if this was my issue I wouldn't hesitate at this point to get a fresh copy of the Mustang, uninstall the present installation and all the data files associated with it and install a NEW copy along with the updates if required.
It's just me I guess. Once I've decided that an issue is local (and 99% of them are), I would simply download a new copy of whatever plane is involved and get a fresh new start.
It seems obvious to me (I could be wrong. Been wrong before that whatever this issue is involves your saved and reused installation executable file. Lewis would be the go-to guy on that but this would be my opinion. I base this on the fact that the issue has carried forward so many times and on several computers as you have stated.
Other than that I'm at a loss to nail down what specifically might be the problem here.
As always, best of luck with this. Ping Lewis and see what he says.
D

Thanks Dudley,

Yes…per my OP…3 sims, 3 computers, consistent issue…

To summarize… I purchased and installed the Mustang in FSX Gold on computer #1 in spring of 2019. Moved to FSX:SE and reinstalled (likely same executable). Bought Computer #2 in August 2019, installed NEW executable from A2A account in FSX:SE. Bought P3Dv4 and installed NEW executable from A2A account on computer #2. Purchased computer #3 in September 2020 and installed into P3Dv4.5 and FSX:SE, both with NEW executables from A2A account. Bought P3Dv5 and installed the Mustang, again with a NEW executable from my A2A account. That’s a total of six installations on three different sim platforms and three different computers, ALL with NEW executables from my A2A account and the issue has been consistent in every installation.

I was actually hoping Lewis or Nick might chime in…

Been watching this but not much to offer. I have had the Mustang lurch forward on occasion as well but it was always pilot error. Maybe I had the throttle too high or maybe I had primed a tiny bit too long. Watching your video I can say that I have never started the engine with throttle at full. That would seem to be in direct correlation to what you are experiencing. I have found that after an update several years ago the suggested 4 seconds of priming is way too much now-a-days. With the OAT as shown in your video, and the fact that you had flown it recently without sim restart, I would be tempted to give 1-2 seconds primer and then "tickle" it as your cranking.

One other item that I have found to be important is to restart sim after each flight. I don't always do this but it is good to clear things out of memory when possible. Currently I'm landing on every airfield in the South Pacific in the B-17 and many fields are a mere 30 NM apart so I have not been restarting each time. Just taxi back, idle into the wind long enough for engines to cool, and take-off for next field. I do this for 3-4 legs then restart sim and even PC before the next legs.

On what Dudley has suggested I have one question. Have you been using the data file for your P51 throughout these PC and Sim upgrades? If so try removing the file < P51civLog.dat > from ~\Documents\A2A\FSX\P51Civ folder. Move it to desktop, let A2A build a new one during a flight, test. If the issue persists then put your original back in so you don't loose your hours.

Good luck Sir
Roger

Thanks Roger,

Yes, that start procedure is what I should have done…however the airplane would still have overpowered the brakes in my experience. I used to be anal about restarting sim and computer on a regular basis, but now feel that with the newer technology and sims in play, I should be able to do long sessions with multiple flights, with which there has never an issue, with the exception of this particular one.

It’s not enough of an issue to me to try uninstalling/reinstalling and moving folders to try to rectify at this point. All I was really trying to do is establish if this is a situation that’s unique to me or if it’s a global bug of some type. If it’s just me, so be it…if it’s not just me, I think it would be nice if someone would have a look at whether it can be fixed or not.

After reviewing the video, I believe that the chock jumping thing is due to starting at wide open throttle. No matter how quickly you retard the throttle, there's enough fuel/air already in the engine to let that Mustang want to boogie!

Watch this video between minutes 3 and 5 for the startup portion: https://www.youtube.com/watch?v=QtFeJ-y ... x=5&t=188s. I think the whole video is good.

Priming time is somewhat critical. I read this in a post by Dudley (https://www.a2asimulations.com/forum/vi ... 93&t=32607), with some additional notes on priming from Scott:
***************************************
COLD STARTING TIP

I want to add a tip for cold weather starting

The effect of cold weather for primer in our Accu-Sim birds may be too high (not sure as there really isn't a lot of data / experience since we all heat our engines up these days in cold weather and pilot's manuals have conflicting information). There is some data showing it becoming almost ineffective at only moderately sub freezing conditions, yet other data is simply too vague so we may be on the money here, just not sure still. So we are still researching this.

Looking at the actual code using the primer, I'm showing on the current P-51:
- Over 50 deg F (hold primer for 2-4 sec)
- 30 - 50 deg (hold primer for 4-8 sec)
- under 30 deg (hold primer for 12 sec)

Scott.
*****************************************

That time vs. ambient temp bit came in really handy when we were trying to start our Mustangs up at Barrow, AK last November. That was the start of our epic MP flight from Barrow, AK down to the southern tip of South America, all in P-51s.

Another thing I've seen work with a flooded engine is the "do-over." That's where you hit Shift+3 and select Cold & Dark. The airplane is instantly transformed into cold & dark, with no flooding, the fuel valve off, controls locked, etc.

Hope that helps.

Seeya
ATB

Thanks Paughco,

As I mentioned above, it’s not a normal “jump the chocks” situation. The park brake was also set and it’s inconceivable to me that the airplane still jumps forward because of a very brief ‘surge’ to 1400 rpm…

Lots of experience with cold starts here and no need to go anywhere near Barrow to practice! I think the coldest I’ve ever started it to date was -25°C in Airdire, Alberta last winter...ick

In the interests of “real as possible”, C&D only applies to the first start of a sim session, so not an option for me on subsequent starts

BTW, thanks for the reference to and shout out for *my* video... https://www.youtube.com/watch?v=QtFeJ-y ... x=5&t=188s Much appreciated and I’m glad you enjoyed it!!

Hi Rob, you’re not crazy…or alone! The P-51 will leap forward regardless of chocks or the parking brake when I re-start the aircraft in the same session. I don’t know if this can be seen on an immediate restart or if some small amount of time needs to pass. Regardless, the best way to avoid scooting halfway across the airport on your mid-session restart is to use minimal throttle and minimal or no priming (as Paughco points out above) …and be ready to get on the brakes.

Thanks Jacques,

Not much more to say other than, “Where have you been, and I LOVE YOU!!”

Thank you very much for the confirmation that this is not a unique, local issue! Now it would be very cool if someone from A2A could pop in to advise if they can duplicate and fix the thing…

Cheers, All,
Rob

[Lewis - A2A]

Hey Rob,

is this just on restarts with multiple loads, as that will be the cause. As P3D has developed it has grown more not less likely for this to be an initialisation issue. So restarts are still the order of the day. Ill raise it however and see if there is anything that can be done our end to try and mitigate the issue of initialisation issues on multiple reloads in the same session.

thanks,
Lewis