fixed [REPORTED-MINOR] Aileron travel with flap sdown

Hi,

with flaps down the ailerons should still travel their full range, while now they are limited to only a few degrees up. This was reported by a couple of RL Hornet pilots (not sure if that's been reported here too).

Anyway, you can also see the video here, it's bad quality but clearly shows it.

EDIT: found a much better video, watch 00:27

old video

Can devs aknowledge this? It's a pretty obvious discrepancy with RL...

F/A-18C Hydraulic System not modeled correctly.

Okay, let's try this again. I am going to try to describe (without showing any documentation) how the hydraulic system works in the F/A-18. I have found that it is the same for all variants spanning from Lot 1 of the F/A-18A/B to the Lot 20 of the F/A-18C/D. If you wish to follow along with what I am talking about, you can search in google "f/a-18 natops flight manual" and click on the first link (Hopefully that doesn't get this post taken down). Then you can navigate to page 1-2-44 and look at the schematic of the hydraulic system. Okay, now that you are there (If you wish to do so) let's talk about how the hornet hydraulic system works. Assuming you already have the APU on as soon as you crank the right engine, the hydraulics with start to come alive. Now as you can see on the diagram, only part of the flight controls come online. These include, Left Aileron, some power to the Left/Right TE flaps, some power to the Left/Right Stabs and the left rudder. This leaves the Right Aileron, the Left/Right LEF, and Right Rudder still drooping. Here is a video showing how the process works. https://youtu.be/kYY0EIbwrHI?t=73. Take note on how slow the LEF's and Stabs move because they are only getting half of the power. As you can see also, once the left motor starts cranking, it supplies the rest of the hydraulic power to the flight controls. Also take note on how slow the ailerons move compared to the LEF's. Now, moving onto how it is done in the sim. Watch this video I took and see if you can see what is wrong with it.

Very good analysis, thanks for taking the time. Please keep in mind that I'm not very knowledgeable on this particular topic, so excuse any small or enormous mistakes.

Firstly, this is in line with and a good addition to comments made by a real Hornet pilot, regarding the movement speed discrepancies of different control surfaces.

Secondly, there also has been discussions around the hydraulics system regarding the TEFs deploying fully upon engine shut down (either due to fuel depletion or damage), with some people claiming that the TEFs should instead use the reduced generator power to slowly assist pilot inputs, rather than remain fully down at all times. The engines are still windmilling in the air and that should provide some hydraulics power, after all. Please someone correct me if I'm wrong on this.

All in all, it appears that the hydraulics system should be re-examined.

@ PanicMan15, like previously, I agree in all points. Expecially the wrong/restricted aileron travel, which would get th aiplane grounded before even moving out of its parking spot IRL, is rather annoying.

Now let's see how long this hydraulic thread survives :(

Thanks for the kind words. This should really be addressed especially at this level of aircraft. I know it doesn't really "Affect" anything, but it's what gives this sim an edge over other sims. It's realistic properties.

Assuming you already have the APU on as soon as you crank the right engine, the hydraulics with start to come alive. Now as you can see on the diagram, only part of the flight controls come online. These include, Left Aileron, some power to the Left/Right TE flaps, some power to the Left/Right Stabs and the left rudder. This leaves the Right Aileron, the Left/Right LEF, and Right Rudder still drooping.

Not true. All of the flight control surfaces are powerd by both left and right hydraulic systems via switching valves. What happens at start up (at least to my understanding) is that when right engine is started up and hydraulic pump starts to provide pressure and those surfaces that are not behind switching valve (left aileron for example) are powered pretty fast, but those surfaces that are behind switching valve are powered only after hydraulic pressure is high enough to beat the spring loaded switching valve. On the blue angels start up video left engine isn't running in my opinion when right aileron starts to move. Correct me if i'm wrong ofc.

You would be somewhat correct about that. There are valves that hold back some hydraulic power. I believe as soon as the engine begins to crank, that's when the hydraulic pump starts engaging for Engine 1 (at least from what I can tell from NATOPS and Videos). Regardless of the specifics on how it works (I can't really find and crazy in depth stuff and post it here), it is modeled incorrectly. If anyone has any more info on how the system works, I would love to hear it.

PanicMan,

I think you're missing the function of the Switching valves.

Now as you can see on the diagram, only part of the flight controls come online.

These include, Left Aileron, some power to the Left/Right TE flaps, some power to the Left/Right Stabs and the left rudder. This leaves the Right Aileron, the Left/Right LEF, and Right Rudder still drooping.

I think you've misinterpreted the first video you posted. It shows all flight controls being powered and moving after the #2 engine is started. Start begins a ~1:20 and by 1:55 all controls are actuating. There's only 1 "start howl" and 35 seconds is not enough time to start both engines. Also look at the heat blur coming from only the (pilots) right side of the jet. You can hear #1 spooling up at ~2:05.

Our Hornet might not model the pressurization of the system during the start, as it looks like maybe some actuators are getting pressure before others during the 1st engine spool up. It looks like in DCS that all are pressurized at the same time. Also it's difficult to easily make statements about the behavior of the controls, as they are commanded by the FCS and not purely the stick. It does seem there's some variation in flap scheduling between the Angels and your video. That might be down to FCS programming or be an actual bug.

Hydraulic Pumps are part of the AMAD and mechanically turned by the engine. If the engine turns so do the pumps.

Also it's difficult to easily make statements about the behavior of the controls, as they are commanded by the FCS and not purely the stick.

If the flight controls wouldn't move across their whole operating range during this check, this check would be rather useless and I doubt that the FCS limits the surface deflection with the airplane sitting static on ground.

I think you've misinterpreted the first video you posted. It shows all flight controls being powered and moving after the #2 engine is started. Start begins a ~1:20 and by 1:55 all controls are actuating. There's only 1 "start howl" and 35 seconds is not enough time to start both engines. Also look at the heat blur coming from only the (pilots) right side of the jet. You can hear #1 spooling up at ~2:05.

 

 

Hydraulic Pumps are part of the AMAD and mechanically turned by the engine. If the engine turns so do the pumps.

You don't need enough time to start both engines, you only need enough time to start 1 engine and then get the other engine spinning. Hydraulic pressure builds quickly even at the beginning of the start process. The start howl happens long after the rotation of the engine by the starter has built sufficient pressure to move the surfaces.

Starting of the right engine begins at 1:13, controls start moving 7 seconds later at 1:20. But only the controls fed by the right engine as explained by OP. Right engine start complete at 1:46, notice the thumbs up from the pilot. Left engine is then spooled probably a second later, and the right rudder comes alive at 1:53, roughly 7 seconds after beginning to spool the left engine.

This seems fit very well with how PanicMan described that the system should work.

But only the controls fed by the right engine as explained by OP.

This seems fit very well with how PanicMan described that the system should work.

That's not how the flight manual describes the system.

I appreciate everyone's words on this matter. I will take a better look at the systems but regardless of how it functions. The DCS Hornet is not accurate. I am here to show what parts are not accurate and try to give the best information possible on it. Thanks!

Not true. All of the flight control surfaces are powerd by both left and right hydraulic systems via switching valves. What happens at start up (at least to my understanding) is that when right engine is started up and hydraulic pump starts to provide pressure and those surfaces that are not behind switching valve (left aileron for example) are powered pretty fast, but those surfaces that are behind switching valve are powered only after hydraulic pressure is high enough to beat the spring loaded switching valve. On the blue angels start up video left engine isn't running in my opinion when right aileron starts to move. Correct me if i'm wrong ofc.

Exactly what happens , the switching valves have 9 seconds to switch if they don't they will trip a blin code I believe 66/67 for left and rh ailerons don't quote me though going off memory, then they are replaced. The hornet can run the FCS on 1 hyd system regardless of which one it is all be it with slightly sluggish controls compared to both systems but not enough for you to visually see. I'm a airframe tech on the hornet so this is my job.

As I'm completely out of my depth here, allow me to start by commend everyone here on your expertise on the subject.

My only contribution would be that this module is still in early access, so your wishes may still come to fruition.

Continue the good work.

Exactly what happens , the switching valves have 9 seconds to switch if they don't they will trip a blin code I believe 66/67 for left and rh ailerons don't quote me though going off memory, then they are replaced. The hornet can run the FCS on 1 hyd system regardless of which one it is all be it with slightly sluggish controls compared to both systems but not enough for you to visually see. I'm a airframe tech on the hornet so this is my job.

Thank you ace. This makes much more sense on how the system works. Now that we have the debate over about how the system works, we need to establish that EDs hornet is not accurate when it comes to the hydraulic system. I am not convinced that the hornets hydraulic system is not accurately modeled. If you play look at the flaps vs aileron speed in my DCS video vs the blue angels video, the dcs hornets moves too fast it seems.

More evidence of this.

I honestly don't know why this is not being acknowledged. It's been reported by a number of people including real F-18 pilots. There is clear video evidence of it. I even PMd Wags about it. Total silence.

There are other discrepancies with the HYD system reported here (https://forums.eagle.ru/showthread.php?t=244490&highlight=aileron+travel), again no acknowledgment.

ED asks for community support in spotting bugs, I think this is a pretty big one as it involves one or more major systems of the aircraft (hydraulics, FBW and control surfaces).

It's also probably just visuals, why it's probably low on the to-do list

It's also probably just visuals, why it's probably low on the to-do list

The flight controls check done from the outside IRL is also 'just visuals', but if they would move the way they do on the DCS Hornet, the plane would be grounded immediately. ;)

The flight controls check done from the outside IRL is also 'just visuals', but if they would move the way they do on the DCS Hornet, the plane would be grounded immediately. ;)

It *is* still probably "only" visuals in a very complex module, and I am guessing they will continue working on other stuff, first, is all I'm saying.

Hello Nineline, Thank you for taking the time to look into it. Now I still don't believe that is true. After watching multiple F-18 demos and talking with some Blue Angels personnel about this. The Blue Angels do not perform a bit test when starting a demo. It is all done earlier in the day during morning turns. When the Blue Angels do their FCS wipe they do it in AUTO, HALF and FULL flap configs. They swipe the controls 2-3 times full deflection which you can see in the video I posted. I will post another video confirming this.

After talking with Wags, this is correct as is, the range you are seeing with the flaps down is from an FCS test, otherwise, it is moving as expected.

First off, thanks for re-opening the thread :thumbup:

The videos I posted are not showing the FCS BIT test, the pilot is cycling the control surfaces through their full range as part of before take-off checks.

You can see at the beginning of this video the aircraft is already taxiing and coming to a stop at a hold-short spot before takeoff, presumably all BIT checks have already been performed by then (they are part of the before taxi checklist).

Two more reasons why this is not a BIT check:

1. The sequence is clearly not that of a FCS bit check, which takes quite a bit longer and moves surfaces in a different sequence.

2. Notice also how T/O trim is already set, something that would only be done after the FCS BIT, according to the checklists and confirmed by videos available on youtube (so no reason to think they would have followed an abnormal procedure in this particular video)

In this other video (the quality isn't great but watch carefully), the aircraft is about to be launched, again, not a place/moment for an FCS BIT check, the pilot is doing the controls wipeout and the aileron is moving upwards to the full extent.

While the current behavior may indeed be correct, it is undeniable that we are seeing something different in these videos, something that DCS doesn't replicate for whatever reason. On top of that, it was first reported by someone who claims to be a RL F-18 pilot, so IMO this is something to look into a bit deeper / question for your SMEs.

Idk how else to express I have talked to Blue Angel personnel about this issue. What else do you need from me to prove it is legit? Even in this video you can see them do the BIT test beforehand and then do the flight control wipe. Full deflection, flaps down.