A2A Development Update 11/25/11

[Scott - A2A]

Here are some answers to the questions posted in this topic:

Q: “Quick question: I notice in the video you make a point of showing the Spitfire Mk Ia landing gear being raised one at a time with the new hydraulic system... will this be incorporated with the next Accu-sim core update?”

A: Yes this is the new system in the Spitfire. This is a result of modeling the gear locks. In the hydraulic system, it is always seeking equal pressure, so if one down lock takes a bit more pressure to open, it may not reach that pressure until the other gear is up and in it's bay. You will also notice this in flight. One gear leg may start to come up, then when it is 1/2 way up or so, the other legs down lock pops open and starts moving. This leg will tend to rise until it reaches the same point as the other leg, then they will slowly rise together. It's neat to watch this in game for sure.



Q: Do you model Flap Droop and Flap Creep on the P-40

A: Yes, but keep in mind the flap system traps the pressure so the flaps hold in place even when the main hydraulic system is completely depressurized. Even on the P-51, if you pull the hydraulic release handle and don’t lower the flaps handle, the flaps will hang there for a while (as seen in the video). Over time they will slowly come down by their own weight.



Q: There's a video to audio de-synch with the cowl flaps

A: Very good observation and good hearing . This is because the external and internal video for that scene was recorded separately.


Scott.

[bullfox]

Still would like to know why you start the engines on prime rather than advancing the mixture to start.

[whiic]

Still would like to know why you start the engines on prime rather than advancing the mixture to start.

I don't know the real reason but I could imagine it would give an extra layer of security both for pilot error and mechanical failure.

Say, you have accidentally put throttle way too high. You start with auto-rich: damage ensues as engine to race to high rpm while oil pressures will take time to rise. Also, this will cause risk of colliding, etc. if brakes/chocks aren't applied.

If you start with primer with too open throttle, the engine won't run any faster than with low throttle on primer. It might actually run better with lower throttle. If you open the throttle too much when running on primer, you actually lean the fuel mixture causing loss of engine power.

The risk of overflooding the engine might or might not be an issue. I don't know since I don't operate real warbirds. These are all based on my hunch, which on the other hand is based on my experience with carbureted car engines. (And I ain't even a car-mechanic.)

Q: There's a video to audio de-synch with the cowl flaps

A: Very good observation and good hearing . This is because the external and internal video for that scene was recorded separately.

The audio is desynched from both videos. The "bang" sounds when flaps are clearly open in external view. The "bang" sound when flap control lever is clearly not in the closer position yet. The two videos (while not perfectly synched to each other) are closer to each other than to how the sound should be. Obviously that doesn't mean there's a real desynch in the actual game as the audio track can be considered a separate, third track, and can be (in most video editing tools) be moved freely from both video clips. Considering sound is advanced from video, how would Accusim have a talent of premonition, i.e reading the mind of the pilot of whether the flaps are to be completely closed in the future.

"Bang" effect is most likely properly timed already even if not in the development update video. I just hope the sound of moving flaps between intermediate states will be equally synched. Now it seemed to be synched to whether mouse button is pressed or not - not to whether the lever is moved. "Bang" sound was advanced, but the subtler clicks were delayed from level movements.

Anyway, when the public release comes, I trust that it'll be timed to both internal and external views. You've perfected it before so it'll be perfected again. (Though, personally I only care about internal. External is for movie makers and 13yo doom players...)

Considering that each update has exceeded my expectations, I'm wondering when there's going to be some actual limits to what you're willing and able to model from grass-roots up. Splendid work, again.

[CAPFlyer]

Still would like to know why you start the engines on prime rather than advancing the mixture to start.

Mainly to minimize the risk of flooding the engine during start and causing an engine fire. Once the engine is started, if there is a problem with the fuel metering valve, you will vaporize the fuel into an air charge much too dense to support a stack fire and you'll just get a mostly harmless white mist out the stack for a few seconds before you shutoff the fuel and allow the engine to stop on its own. However, on the converse, if you try to start the engine and there's raw fuel just pouring into the stack, you have plenty of fuel and the right charge ratio to allow a fire to start and then bad things happen.

[pjc747]

Still would like to know why you start the engines on prime rather than advancing the mixture to start.

Mainly to minimize the risk of flooding the engine during start and causing an engine fire. Once the engine is started, if there is a problem with the fuel metering valve, you will vaporize the fuel into an air charge much too dense to support a stack fire and you'll just get a mostly harmless white mist out the stack for a few seconds before you shutoff the fuel and allow the engine to stop on its own. However, on the converse, if you try to start the engine and there's raw fuel just pouring into the stack, you have plenty of fuel and the right charge ratio to allow a fire to start and then bad things happen.

In many planes, you start with misture at full rich, why are these planes any different?

[Scott - A2A]

BTW, it's a small world we live in. When I was down South several years ago, Chris (CAPFlyer) ended up driving me back to the hotel from the airport. We were on a research trip. I really enjoyed the conversations with Chris. He is a wealth of knowledge.

Scott.

[CAPFlyer]

Still would like to know why you start the engines on prime rather than advancing the mixture to start.

Mainly to minimize the risk of flooding the engine during start and causing an engine fire. Once the engine is started, if there is a problem with the fuel metering valve, you will vaporize the fuel into an air charge much too dense to support a stack fire and you'll just get a mostly harmless white mist out the stack for a few seconds before you shutoff the fuel and allow the engine to stop on its own. However, on the converse, if you try to start the engine and there's raw fuel just pouring into the stack, you have plenty of fuel and the right charge ratio to allow a fire to start and then bad things happen.

In many planes, you start with misture at full rich, why are these planes any different?

Well, first, you can run the plane on primer no matter what and that's the thrust of what Scott was showing anyway, that a real engine will run on just the primer. FS by default won't let you do that. A2A through Accusim is allowing you to do it.

However, on the procedure front, it depends on the airplane more than anything, but I know a lot of older guys (and a lot of older airplanes) that starting with the mixture at idle cut-off is the way it's done. I have a 1972 Cessna 172 POH where the start procedure says to have the mixture out and then to feed it in smoothly as the engine catches on the primer fuel. I have a 1985-ish 172 POH that says to start with it full rich already. Both are carb models. I have an early fuel injected (172SP) POH that says to start with the mixture off, and a brand new fuel injected checklist (172S/G1000 NAV III) that says mixture rich for start.

On the Convairs at Air Tahoma, we started the engines and then fed in the mixture. At the CAF's DFW Wing they do the same with the R4D-6. However, with the T-6's that are also based there (member owned), both start with the mixture at rich. I know AgCat guys with the same R1820 that start with the mixture at cutoff.

I think in the end, there's no "right or wrong" answer to the problem, just whatever works for you.

[CAPFlyer]

BTW, it's a small world we live in. When I was down South several years ago, Chris (CAPFlyer) ended up driving me back to the hotel from the airport. We were on a research trip. I really enjoyed the conversations with Chris. He is a wealth of knowledge.

Scott.

Scott, I enjoyed that trip with you. I'm still hoping that the work we did shows up in the not to far future too. If you're down this way, let me know and I'd be glad to help out however I can within my schedule (i.e. if I'm not at work or sleeping, I'm all yours... )

[whiic]

In many planes, you start with misture at full rich, why are these planes any different?

Because they're not the next generation of Accusim. And because in 99% of times, starting auto-rich doesn't cause trouble even for engines which are safer to be started with cut-off mixture.

Here's a video about B-17 "Liberty Belle"
http://www.youtube.com/watch?v=eQGhflYqD8Y
It includes tutorial on how they used to start the engines with primer only (around 5 minute mark). ("Used to" because Liberty Belle burned to ground. But it wasn't related to engine fire due to improper start-up procedure. I don't even know what it was but it caught fire only after take-off.)

Note: it has... or had, a modernized(?) electronic primer instead of a manual muscle-powered one. Also appears it had starter and mesh coupled to one switch.

But, if A2A B-17 was equally advanced as Spitfire and other "2nd gen" Accusim planes, it would too start on primer only, if preferred. I however still has part of it's engine modeling within FSX and those parts are subject to FSX limitations such as mixture cut-off being absolute kill switch.

[Erlk0enig]

I saw in the startup-manual that the P-40 had a carb heat, and it also had a CAT gauge. Will carb icing also be modelled in this aircraft? I learned that the Spit had some kind of automatic carb heat by integrated coolant fluid channels in the carb.

[Boon1986]

Great Info, Thanks for this great Vid boys.
Best Regards from Germany
Daniel

[pjc747]

In many planes, you start with misture at full rich, why are these planes any different?

Because they're not the next generation of Accusim. And because in 99% of times, starting auto-rich doesn't cause trouble even for engines which are safer to be started with cut-off mixture.

This was a reference to real-life, because nobody needs Accusim on the real thing!

[pilottj]

Thanks for the great video. Really looking foward to these birds.

While you guys were playing the the BF-109 flap wheel, don't suppose you guys had your recording equipment with you....

[r4y30n]

Still would like to know why you start the engines on prime rather than advancing the mixture to start.

Mainly to minimize the risk of flooding the engine during start and causing an engine fire. Once the engine is started, if there is a problem with the fuel metering valve, you will vaporize the fuel into an air charge much too dense to support a stack fire and you'll just get a mostly harmless white mist out the stack for a few seconds before you shutoff the fuel and allow the engine to stop on its own. However, on the converse, if you try to start the engine and there's raw fuel just pouring into the stack, you have plenty of fuel and the right charge ratio to allow a fire to start and then bad things happen.

You know, this reminds me... Will "wet starts" ever be simulated on the Spitfire?

http://www.youtube.com/watch?v=BzVBlMXJDms

And was this behavior typically only on the port-side bank? On a related note, will we soon see flames like this out the pipes at night? (I noticed the flames that used to be on the Mk I and II while running at night disapeared with the last update)

http://www.youtube.com/watch?v=QhFAwSk9 ... re=related

On a separate note, will the Spit be getting jacks as well?

[pjc747]

I'd also like to know, will it be simulated, say if you're doing a run-up, and you accidentally shut both magnetos off, that the engine will flood if you don't catch it immediately?