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Old 12-30-2017, 10:19 PM   #659
gospadin
ED Testers Team
 
Join Date: Feb 2015
Location: 'Murica
Posts: 1,947
Default Community A-4E: December 2017 Update

Community A-4E: December 2017 Update

Hi everyone!

This month we're sharing (1 day early!) a bit of in-progress work to create a set of sight tables for the A-4E.

As most of you know, Vietnam-era A-4s did not have "modern" ranging gunsights with computer calculated impact projections. Merely a collimated reflector site, that the pilot was responsible for manually setting to the proper amount of sight depression. Since that'll be about the only way to get accurate weapons-on-target, we realized that we needed to create a set of our own tables to match in-game armaments.

We do have a copy of the official pocket guide, and were able to test the published values for a variety of armaments. However, due to slight variations in the flight model, ejection force, or other details, we found the published values are off by 10-20% for slick munitions, and 5-7% for high drag munitions. Adding to that, it's very difficult to manually hold a perfect 10 degree dive to a target point with an exact release height of 3000' and a velocity of 450 knots true!

To first do the calibration to generate our own tables, we needed a way to exactly maintain radar altitude. To do this, we added a debug mode of the altitude hold AFCS that used the radar altimeter instead of the barometric altimeter. (I also cheated and added tuning functions to climb or descent to even multiples of 10').

From there, we set airspeed to published values (350, 400, 450, 500 KTAS) and dropped weapons manually based on targeting with the gunsight in level flight. (You will also see our debug console in use here, to confirm TAS, radar altitude and gunsight calibration while flying.)

This first video is of an early test I did with a full compliment (1 of Mk-81 iron bombs. Gunsight is set for 175 mils. In this run, the altitude gets away from me (the AFCS altitude hold disengages if the instantaneous pitch correction becomes too great). Additionally, I am low and a bit fast, but with a bit of climb present, so the bombs ultimately get lobbed and land a few hundred feet long. This is mostly an example of how not to test. =P



In this 2nd video, this time I have the radar altitude hold working at 1500'. Speed is almost exactly set properly at 450 KTAS, and there's an additional 2 mils to account for the increased AoA with this payload. I'm dropping a string of 5 Mk-82 bombs with quarter-second intervals, started a few hundred feet in front of the target trucks. As you can see, in this case the bombs land a tiny bit short of the intended target. (2nd bomb in the ripple was dropped "on target" but landed about 250' short.) The 4th bomb in the string was within 50' of the center of the target.



Ultimately, we'll try to build a set of useful tables for common configurations (Mk-81, Mk-82, Mk-81 Snakeye and Mk-82 Snakeye) plus a few others, so that folks will be able to have a shot at delivering weapons accurately in controlled conditions.

In other news, a number of other little changes ongoing...
  • First, we're still in the midst of the conversion to the 2.2/2.5 engine and PBR, which has us altering almost all our existing textures from the ground up to use RoughMets instead of the old spec maps.
  • More unwrap and texture work continues, and as we texture the new parts, it often exposes little errors that require correction. (Did anyone notice the gunsight knob textures being slightly mis-calibrated? These are the little things we need to nail down!)
  • We still have some modeling changes in-flight, though I don't think any of them are obvious in the above videos.
  • We've made some payload fixes, to work with ED's recently published high resolution LAU-10 rockets and BRU-42/43 weapon racks. We had originally created our own models, but there's little reason to ship our own versions anymore now that the ED models have been updated.

Thanks again for everyone's support, and hope everyone had a great 2017!
--gos

Last edited by gospadin; 12-30-2017 at 10:24 PM.
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