brakes?

[The Fugitive]

So knowing the deployment of dive recovery flaps moves the center of lift enabling control of the aircraft at higher speeds.....this is not the topic of discussion.

Knowing that it isn't a dive brake is not the topic of discussion.
(THIS IS A DIVE BRAKE)
(Image removed from quote.)

What is the topic of discussion is that deploying them (RL) causes drag and enables you to dive up to 45 degrees without slamming straight into compressability.  How much drag? .4 change in the Cd according to the diagram...what that means to the coder is up to them.  Presently I turn the dive recovery flap on when I take the runway....because it has ZERO effect on the Flight model other than allowing you to go a little faster. 

So yes we do understand they are not a brake, but trying to get them modeled where you can actually point your nose somewhat down hill without wearing out your trim button (and yes I fly manual trim as well).....

The other issue is compressability is modeled at .65 vs .67.....  .65 was the placard limit to keep you out of compressability effects. Dive recovery flaps enabled you to go all the way to .72 before entering compressability.

Good input Drano (from a fellow 38 driver), and I know there was a lot of posts to read through...above is a summation of the discussion (not trying to be dick, just keeping it brief).

No this is the topic of discussion..... the OP  My haven't we gone far afield.

 

when I use the toe brakes on my rudder pedals I stop quickly and see a nose dip. If I use the keyboard nothing happens. Does the rudder pedal function cancel out the keyboard function?

whoops wrong forum

[Dobs]

100% correct Fugitive....talk about a thread hi-jack!

[Drano]

No this is the topic of discussion..... the OP  My haven't we gone far afield.

 

Oh crap! Sorry! I just saw all the P-38 charts and figured it was the next incarnation of the dive brakes discussion. Which it sorta ended up being hehe! Always a good convo tho.

Dobs, thanks for posting the pic of the SBD. It's easy to see the huge difference between an actual drive brake (on the SBD) and the recovery flap on the 38. As to the drag thing. I'd never thought of deploying the recovery flap at takeoff but as you say the drag is almost non-existent at slow speeds. That would stop you from forgetting to pop em before a dive! It doesn't really affect anything until high speed flight which is why it's so small. It needs all that extra pressure on that smaller area to do its job. It's applying drag sure. But it's different in that it only functions in a way that's measurable at high speed. It needs that specific airflow across it to function. At that point the drag at that particular point provides the force to move the airflow as intended.

The brake on the SBD is so much larger because it's designed to work at much slower speeds and actually prevent acceleration. Greater surface area at a greater angle at slower speed would get you the force necessary to slow the dive. If you reversed the flaps and put that little one on the SBD it'd lawn dart every time not having enough surface area to work against the airflow. Put the big'uns on the 38 and at high speed I'd guess they'd just rip away! It wasn't until later jets that employed speed boards for that and by then they were going faster still.

I remember reading somewhere that even after the flaps were adopted there was still debate about what caused and helped the problem. Some still thought the counter weights on the elevator were actually the answer and that's why they were retained.

Sent from my XT1585 using Tapatalk

[Dobs]

Yeah some Lt Col thought Counter weights were the answer....when he was proved wrong he wouldn't admit it and thus they stayed...

Changing the Center of lift was the issue....resulting in compressability effects.  Dive recovery flaps were 8" frontal surface deployed at a 40degree angle 5" into the windstream and were 58" long. They effectively changed the center of lift back forward and enabled control until .72Mach. 

In RL they have some drag...thus the ability to dive up to 45 degrees angle if you deployed them first....they also had the effect of causing a 3.5-4 G pitchup when deployed at speed:)

Anyhow, good discussion! <S>!

[Dawger]

That's correct. My opinion is based on my experience with aerodynamics. I'm not an expert but I know that aerodynamics are affected by the rear of the design as well as the front.

I agree that strength could be a reason for the design but we're just guessing.

Your video of a flap does not show the airflow for a dive flap.

Where are you seeing lift, drag, and pitch values?

There are many sources for the change in performance with the dive recovery flap deployed. We know its exact location and size on the bottom of the wing. It would be modeled like any other secondary flight control is modeled in game. There are not specific references for lift, drag and pitch for ANY flap system in the game yet somehow they are modeled.

It is a fairly simple process to model the dive recovery flap in its correct position on the P-38 and adjust the lift,drag and pitch numbers to match what we know happened in real life. That is how EVERY FM is built. Your insistence that there be a specific number or it doesn't get modeled is an invalid stance and rather telling if you hold some sort of decision making authority on FM's. If that were the case we would have no FM's at all.

Also, general aerodynamic principles apply across aircraft. What is observed to be true on one is generally true for all. So if you observe lift and drag (and the resultant change in pitch moment) from sticking a 40 degree board in the wind on X aircraft, you will observe the same general characteristics on Y aircraft.

No, the wind tunnel test was not a "dive recovery flap" but it was a deflected surface in the relative wind so the general performance would be similar and certainly close enough for our purposes.

But here is the equivalent of the dive recovery flap available to us on modern aircraft. It is a spoiler, which are mounted on the top of wings to produce negative lift and drag.

"Oh baby, we gettin' some drag there" is a direct quote from our intrepid videographer when the spoiler is deployed.

https://www.youtube.com/watch?v=UHbxDix8BHQ

My personal experience with deploying a 8 inch wide panel into the slipstream at 400 knots is that it is a dramatic event producing easily identifiable results. The aircraft pitches hard, rumbles at a level felt in your gut and slows down. And those are spoilers designed to be on the neutral point on the wing to minimize pitch.

In summary, we know the size and shape of the "dive recovery flap". We know its exact position on the chord line. We know it produces lift and drag. We know that lift and drag increase critical Mach number to .72 AND enables a 30 degree increase in dive angle. We know the application of the DRF at speed causes a 4 G manuever. That is enough data for ANY flight modeler to properly model the DRF on the P-38.

At this point I think you are just desperately clinging to your position for your own ego and not in the interest of the proper modeling of the aircraft in question.

Of course, I don't expect the DRF to be properly modeled. I know I am smashing my head against this particular wall with no particular hope of a positive result.

[gflyer]

it does seem as if the acceptance/ arguments for maintaining status  quo is the quickest response from many,   I know from what I have read , Hitec is proud of his and the teams work towards realism (rightly so),  if the provided data is insufficient to improve on current models so be it.  If it's just not worth the hassle so be it.  Realistic?  Doesn't seem to be hitting the numbers provided.  I'll fly it anyway.  I just shrug when the occasional person goes by and tells me I have my dive flap  deployed in climb/cruise etc.  in its current iteration it's just a light on the dashboard until I need those few extra knots downhill. 

The P47 has the same issue  - no effect on anything but an extension of max speed before compression.  I have no data to say what it should do in that plane.  Just an observation. Maybe a passionate Jug flyer will have it. 

[FLS]

There are many sources for the change in performance with the dive recovery flap deployed. We know its exact location and size on the bottom of the wing. It would be modeled like any other secondary flight control is modeled in game. There are not specific references for lift, drag and pitch for ANY flap system in the game yet somehow they are modeled.

It is a fairly simple process to model the dive recovery flap in its correct position on the P-38 and adjust the lift,drag and pitch numbers to match what we know happened in real life. That is how EVERY FM is built. Your insistence that there be a specific number or it doesn't get modeled is an invalid stance and rather telling if you hold some sort of decision making authority on FM's. If that were the case we would have no FM's at all.

Also, general aerodynamic principles apply across aircraft. What is observed to be true on one is generally true for all. So if you observe lift and drag (and the resultant change in pitch moment) from sticking a 40 degree board in the wind on X aircraft, you will observe the same general characteristics on Y aircraft.

No, the wind tunnel test was not a "dive recovery flap" but it was a deflected surface in the relative wind so the general performance would be similar and certainly close enough for our purposes.

But here is the equivalent of the dive recovery flap available to us on modern aircraft. It is a spoiler, which are mounted on the top of wings to produce negative lift and drag.

"Oh baby, we gettin' some drag there" is a direct quote from our intrepid videographer when the spoiler is deployed.

https://www.youtube.com/watch?v=UHbxDix8BHQ

My personal experience with deploying a 8 inch wide panel into the slipstream at 400 knots is that it is a dramatic event producing easily identifiable results. The aircraft pitches hard, rumbles at a level felt in your gut and slows down. And those are spoilers designed to be on the neutral point on the wing to minimize pitch.

In summary, we know the size and shape of the "dive recovery flap". We know its exact position on the chord line. We know it produces lift and drag. We know that lift and drag increase critical Mach number to .72 AND enables a 30 degree increase in dive angle. We know the application of the DRF at speed causes a 4 G manuever. That is enough data for ANY flight modeler to properly model the DRF on the P-38.

At this point I think you are just desperately clinging to your position for your own ego and not in the interest of the proper modeling of the aircraft in question.

Of course, I don't expect the DRF to be properly modeled. I know I am smashing my head against this particular wall with no particular hope of a positive result.

You imagine many things.   

If you think a spoiler tells you how to model a dive flap we'll have to agree to disagree.