Really struggling with transition to landing config - Page 4 - ED Forums
 


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Old 12-11-2019, 08:44 AM   #31
Notso
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Quote:
Originally Posted by BuzzU View Post
Well no. Post #21 and #22.
Sorry, was just being a bit tongue in cheek.
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Old 12-11-2019, 08:49 AM   #32
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Originally Posted by earnil View Post
You need to understand 2 important things.



1) Your stick doesn't control you flight control surfaces. It doesn't do pitch up/pitch down. It tells the FCS what you want and the FCS moves the flight control surfaces accordingly.

2) Your FCS has 2 different ways how to interpret what you want

a) in clean config the stick forward/aft tells the FCS what amount of G you want (and so does trim)

b) in landing configuration, the stick tells the FCS what amount of AoA you want (and so does trim)



So stop thinking about this in terms of pitch / speed. It's AoA from now on.



Let's go over what happens during the transition into landing config.



You fly level, clean, at 250kts. Your AoA will be about 4 degs and with stick neutral your FCS is maintaining happily 1G. As soon as you lower the gear and flaps, your FCS switches the modes and starts to worry only about AoA. Now, remember, it's current settings is AoA 4 degs. It's trimmed to 4 degs. But since you lowered your flaps, your wing is now generating much more lift and therefore, if the FCS want's to maintain 4 degs AoA it needs to pitch up. That's where the ballooning comes from.

But, you can use your stick to tell the FCS what kind of AoA you want, so you need to put stick forward to tell the FCS - yeah, I know the trim is set to 4 degs, but I would very much prefer if you maintain about 0 degs AoA (that's level flight with flaps down at 250kts).



Therefore, you need to use stick forward inputs to tell the FCS to decrease the commanded AoA. You're basically overriding your trim settings.



Since you set your engines on idle, the plane starts to slow down. As it slows down, it needs more AoA to maintain the lift. As a result, as you slow down, you will need to ease off the stick forward inputs otherwise you'd start to descent. So just ease on the stick to let the jet slow down while maintaining level flight.



At some point, as you slow down further, you will come to stick neutral position. This is a point where your trim settings match your stick command in terms of AoA.



As you ease of to neutral position, you slowly start to throttle up to stop the deceleration. If you time it well (and you just need to do it for couple of times to get the right feeling) you will end up with stick neutral, throttle somewhere above idle, level flight, AoA about 4 degs. From now on the jet will maintain this flight. If you want to descent, you decrease the throttle, as a result, to maintain stable AoA the FCS will command pitch down movement and you will descent. If you increase your throttle, in order to maintain stable AoA the FCS will pitch up, arresting the descent.



Next step is to trim to on speed trim settings - 8.1 degs. So as you trim up, you will notice that the jet will slow down because FCS is pitching up in order to maintain commanded AoA. You need to throttle up to keep the plane flying level. Ultimately you end up on 8.1 degs, on speed, level flight.



Here's some exercise for you - forget about the boat start with

1) flying straight and level, at 250kts, just lower both flaps and gear and use your stick inputs and throttle to stabilize on level flight. Forget about trim.

2) once you master that, try the same, but using the trim to get on speed. You can start with #1 and then just trim after you stabilize, then try to make it more fluent so that you end up with being able to do in one fluent take.

3) Start to do it in a break

4) Once you master all of that and feel comfortable, you can add the boat and start to try the landings.
Excellent explanation! Thanks.

Out of curiosity, is this (FCS mode change from G to AOA priority) unique to the Hornet for getting on the boat? I've not seen such a drastic flight control change when changing to landing configuration on other jets.
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Old 12-11-2019, 08:55 AM   #33
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Quote:
Originally Posted by Gripes323 View Post
Hey SPS48A,
I'm sure you're already putting all this advice to use and doing the case 1 by the numbers... perhaps most numbers
Just wait till ED gets to finish the FM (weight/drag v. power... not spool up/spool down time - that part is not so bad - but how long it takes before you notice any change in glide path). I've seen number of reports on weight related issues with different loadouts. Also, the FCS will know what to do when you roll out on down wind at 800 feet and 190 knots or so with flap switch down to full, nudge the stick down to descend to 600 and trim for AOA... or when you bolter (at least 2 wheels hitting the deck) and you're climbing happily without going vertical (flaps switch full down of course). It'll be a lot easier then, after having mastered the current beast.
All this is just hearsay... from the horse's mouth I've never flown the real Hornet
I'm sure I'm in a small minority here but wish ED would prioritize fixing the flight model / negative ground effect first.
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Old 12-11-2019, 11:03 AM   #34
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Quote:
Originally Posted by Notso View Post
Excellent explanation! Thanks.

Out of curiosity, is this (FCS mode change from G to AOA priority) unique to the Hornet for getting on the boat? I've not seen such a drastic flight control change when changing to landing configuration on other jets.
To be absolutely clear, I have no idea whether this is how it even works in a real jet. This is what seems to me to be the best description of what the FCS is doing in DCS. It makes sense that it does, but the effects in actual jet may be completely different.

The problem is, that the simulation may be 100% accurate in terms of aerodynamic and technical factors but you have to consider there are vast differences between how the real plane interfaces with the pilot and how the DCS one does.
Things like speed of the trim, the movement of the stick, stick resistance, that's impossible to simulate correctly, just by the simple fact that there are hundreds of different sticks with different spring loading, different forces, how fast the computer repeat the trim commands,...

It's entirely possible that what results in a dramatic ballooning in DCS and what needs to be arrested with rather dramatic stick / trim input is IRL a gentle rise that can be easily delt with by couple taps on trim button (and actually if you watch some Hornet landing vidoes, right when they come out of break they tend to go gentle stick forward and trim a bit nose down and then right nose up again as they get on speed).

Also, Hornet is really unique in DCS since it's the only jet with advanced FCS and separate flaps controls. In F16, you just lower the gear and the flaps are managed by FCS based on AoA. So there's really no point where you'd have this abrupt change in lift factor. Other planes with flap controls like F14 or L39 definitely ballon too but probably since you have direct control of the flight surfaces and the response to corrections is more immediate it doesn't seem to be so 'un-natural' to people.
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Old 12-13-2019, 01:44 PM   #35
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Great post. I had to trial and error that over about 20-hours of flying to figure it out on my own Many thanks.
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