Pitch UP when Carrier Launch with Auto Flap

Ok , i think i understand the confusion re trim . As stated in the Natops , which also indicates that the Hornet does indeed fly differently than other aircraft , the FCS auto-trim , and the pitch trim bias , flies for g , not attitude . The FCS normally attempts to auto-trim for 1g . The bias introduced by the trim switch is for g as well . I flew an instant action free flight mission over the Caucasus , at altitudes between 5000 and 10000 ft , and entry speeds between 350-500 knots . On holding pitch down trim and neutral stick , the aircraft unloaded gs at a rate of about .1 per second , at lower altitudes and speeds ., and somewhat less at the higher altitudes and speeds . Being a g-trim and not an attitude trim , when i let go of the trim switch (10 sec) , the nose continued to drop , holding the same pitch rate , with the result being approximately a 20 degree dive on trim release , and 30 degrees a couple of seconds later . Very dramatic ! The same figures applied to nose up trim . Natops reference :

11.1.3 Auto Flap Configuration. The FCS control laws create slightly different handling qualities

than those of most aircraft. The most apparent characteristic is the excellent hands-off stability.

Damping about all axes is high. Static longitudinal stability is neutral since the FCS attempts to keep

the aircraft in 1 g, zero pitch rate flight. Longitudinal trim is used to bias (adjust) the reference load

factor or pitch rate as the pilot desires.

However , the aircraft CAN allow pitch trim for attitude , by use of the autopilot in attitude mode . Natops reference :

2.9.2.1 Autopilot. ATTH

At this time the aircraft maintains the existing pitch attitude.The pitch attitude hold reference can be changed with

pitch CSS to any value between ±45° pitch. The pitch attitude reference can also be changed with the

trim switch on the control stick at a rate of 0.5°/second.

(Edited for clarity)

Note the relatively slow speed of the attitude change:)

Just tested:

Pitch trim works fine. At 500kn I was able to trim the aircraft to fly both a 0G and 2G hands off. It is not as fast or responsive as other aircraft but it works.

I also did a few Flaps Auto takeoffs and had no problems. But during the cold startup I would exercise the flaps from full back to Auto as you should after the FCS reset.

I know to use half flap in carrier launch,

But using Auto Flap in Takeoff, The pitch go too much high and was not effected trim down.

It fly with pitch high trimmed state and can not be trim down.

 

Only have to do is, gear down and up and flap full and auto. it reset the trim. I think it must be a bug.

No it is not. "You shall not use AUTO flaps for Take-Off!" As when you put the gear in a car from 4th at 120 kph to the 1st gear it will blow your engine , which is not a bug. The manual and NATOPS checklist says precisely what to do. :book:

Edit: https://info.publicintelligence.net/F18-ABCD-000.pdf

Procedures:

(...)"10.2.1.3 Before Taxi (...)

11. (ABC) Flaps - FULL

While at full flaps, cycle stick in small circular motions (1 to 2 inches diameter) at a rate slower than

one cycle per second. Stick motion should be smooth and continuous. If stick provides uncommanded

movement, horizontal stabilator servocylinder and mechanical linkage troubleshooting is

required prior to flight.

12. (ABC) Flaps - HALF

13. (AC) Trim - CHECK" (...)

After that the flaps are touched again, when airborne.

(...)"11.1.3 Auto Flap Configuration. The FCS control laws create slightly different handling qualities than those of most aircraft."(...)

That may be so Shagrat but I've personally seen display F-18s do Flap Auto takeoffs for whatever reason so the aircraft can do it. At least in display config. Providing you cycle the flaps before takeoff Auto works ok on takeoff in DCS currently, not that I use it. I think the pitch up bug comes from not cycling the flap state after spawn or FCS reset.

For now players can fix this by either taking off in the correct configuration, or if they took off with flaps in auto, by flicking the flaps to half and back to auto.

The simple fact is you’re doing it wrong. Numerous people have posted quotes from the NATOPS flight manual describing the EXACT behavaior you are describing as the result of taking off with the aircraft improperly configured. You cant believe the FCS will try to kill you if you configure the aircraft wrong? Let me ask you this, what do you think Test Pilots do? Their job is to figure out all different ways the aircraft will try to kill you and how to prevent it. Once they figure out how to prevent it they put that information in a book so everyone else knows what to expect.

By your own admission you are improperly configuring the aircraft and calling the resulting flight control issues a “bug”. Perhaps instead of defending your improper takeoff procedures and complaining they kill new players you should practice ensuring your aircraft is properly configured for takeoff.

Cool video, i notice that shortly after autoflaps deployed, the pilot hoisted the ship into vertical. How much was stick and how much was trim is for the pilot to say. ;)

The simple fact is you’re doing it wrong. Numerous people have posted quotes from the NATOPS flight manual describing the EXACT behavaior you are describing as the result of taking off with the aircraft improperly configured. You cant believe the FCS will try to kill you if you configure the aircraft wrong? Let me ask you this, what do you think Test Pilots do? Their job is to figure out all different ways the aircraft will try to kill you and how to prevent it. Once they figure out how to prevent it they put that information in a book so everyone else knows what to expect.

 

By your own admission you are improperly configuring the aircraft and calling the resulting flight control issues a “bug”. Perhaps instead of defending your improper takeoff procedures and complaining they kill new players you should practice ensuring your aircraft is properly configured for takeoff.

This community is so unnecessarily aggressive at times - my first words clearly stated I know the correct procedure. The Hornet is in early access and bugs with the FCS are still being worked on - I found strange behaviour and reported it following EDs reporting guidelines. If you don't like reading bug reports, don't read the forums.

This community is so unnecessarily aggressive at times - my first words clearly stated I know the correct procedure. The Hornet is in early access and bugs with the FCS are still being worked on - I found strange behaviour and reported it following EDs reporting guidelines. If you don't like reading bug reports, don't read the forums.

Well it is a digital combat forum. ;)

The simple fact is you’re doing it wrong. Numerous people have posted quotes from the NATOPS flight manual describing the EXACT behavaior you are describing as the result of taking off with the aircraft improperly configured. You cant believe the FCS will try to kill you if you configure the aircraft wrong? Let me ask you this, what do you think Test Pilots do? Their job is to figure out all different ways the aircraft will try to kill you and how to prevent it. Once they figure out how to prevent it they put that information in a book so everyone else knows what to expect.

 

By your own admission you are improperly configuring the aircraft and calling the resulting flight control issues a “bug”. Perhaps instead of defending your improper takeoff procedures and complaining they kill new players you should practice ensuring your aircraft is properly configured for takeoff.

There is a difference between taking off incorrectly configured and a FCS bug. I have had the following things happen to me:

Took off in Auto (like in the IRL video I posted moments ago) and had minor pitch up which was quickly trimmed out by the aircraft, and was totally flyable.

I have also experianced takeoffs in Auto mode which resulted in a pitch up so violent that full forward barely arrested it. What we are trying to figure out here is why these two different results from essentially the same configuration takeoff.

Obviously both takeoffs in this situation are not configured correctly but one is clearly not the right behaviour for the aircraft or you'd never see IRL Hornets taking off with Auto flap... Like in that video i posted a little earlier.

This community is so unnecessarily aggressive at times - my first words clearly stated I know the correct procedure. The Hornet is in early access and bugs with the FCS are still being worked on - I found strange behaviour and reported it following EDs reporting guidelines. If you don't like reading bug reports, don't read the forums.

Nobody is being aggressive. Your first words indicated you know the correct procedure...you CHOOSE not to follow the correct procedure and configure the aircraft improperly...once airborne the aircraft exhibits undesired behavior...and you posted what you thought was a bug report.

In very short order several people provided NATOPS references indicating that it was not a bug. You are causing the behavior by configuring the aircraft improperly. What you were describing matches what the NATOPS manuals say will happen if the aircraft is improperly for takeoff...in other words it was not a bug.

What you interpret are aggressive is frustration. We COULD have read your post and simply thought "he's doing it wrong" and not replied. But that wouldn't have helped you or anyone else doing it wrong and crashing. We provided the correct information...and you argued it was wrong.

Some of us have operated real military aircraft. Some of us understand if it's written in the flight manual it's there for a reason. Doing it wrong on purpose and complaining about the result is counter productive.

 

Took off in Auto (like in the IRL video I posted moments ago) and had minor pitch up which was quickly trimmed out by the aircraft, and was totally flyable.

 

I have also experianced takeoffs in Auto mode which resulted in a pitch up so violent that full forward barely arrested it. What we are trying to figure out here is why these two different results from essentially the same configuration takeoff.

Which you appear to have established to your own satisfaction is due to exercising the flaps-or not- following an FCS reset . And thus , no EVIDENCE of a bug .

Why should ED spend resources chasing a may-or-may-not-be bug that only manifests itself when the simpilot

EGREGIOUSLY ignores MULTIPLE correct procedures ? (Use of checklist , cycling of flight controls , takeoff configuration)

As i said much earlier , perhaps too aggressively for some , this thread simply isn't rational .

Quote edited

Its not a bug

Bit confused why this has been moved out of the Bug section I originally made it in, rather than being marked [Not a Bug] or [Reported].

flaps should be set to half for take off.

That demo was indeed taken from flaps auto....

If you notice the stabilators were not set for 12 degrees up trim either...

The FCS is very specific. You have very little pitch trim authority when flaps are in auto for a reason. The FCS will attempt to fly at 1G no matter what the profile. Sometimes small

corrections are needed via the pitch trim but they are very subtle.

When you drop the flaps the FCS is then giving pitch trim, which it's not trimming at all it's setting an AOA, authority back to the pilot.

The difference between a pilot and an aeronautical engineer is that the pilot follows the rules in the book while the aeronautical engineer writes the rules in the book. The latter involves a much broader understanding of the design.

Simulation is the modeling of behavior in any condition, not just the narrow subset of situations which arise from prescribed procedures. All that is needed to evaluate this behavior from this condition is to follow the FCS logic from the given configuration. Documented procedure is irrelevant. There is no wrong condition in simulation, only wrong behavior.

The reported fact that behavior depends on the history of the flap switch and not only its current position is interesting. Why is this the case? What is different about the airplane that has the switch history A-B-A compared to just A?

How does the FCS operate with the gear down compared to the gear up? If the FCS in normal gains seeking G at all AOA or only low AOA If there is a high pitch transient under this condition, what is the G? What is the AOA?

I suppose the objective question here would be how does the real plane react if the pilot uses the incorrect takeoff configuration and does the sim behave the same way?

If the answer is yes, then it's not a bug.

I suppose the objective question here would be how does the real plane react if the pilot uses the incorrect takeoff configuration and does the sim behave the same way?

 

 

If the answer is yes, then it's not a bug.

Wouldn't volunteer to test THAT profile :)

Which you appear to have established to your own satisfaction is due to exercising the flaps-or not- following an FCS reset . And thus , no EVIDENCE of a bug.

Do me a favour. Spawn a hot jet on the end of the runway. Set flaps to Auto and then get airborne. You should end up with a jet that is hands off trimmed to between 2-3G. Now if we are to assume that a hot jet, has been started and taxied to the end of said runway by a competent pilot who has followed the multiple correct procedures you mention then It shouldn't need an FCS reset or flap sweep to be able to takeoff in Auto flap mode.

You seem to misunderstand the process of bug reporting.. If you spot a bug, you report it. Regardless of size. Its not for us to decide how important a bug is, thats EDs job, they decide the priority list of when stuff gets fixed.

Its extremely easy to correct the problem. Use flaps for takeoff ;). Or if you want to takeoff with flaps in auto then exercise the flaps from full and back to auto which you should be doing as part of your pre-flight checks anyway after resetting the FCS.

Deano , with respect , i was referring to your findings .

Deano , with respect , i was referring to your findings .

So? Thats the workaround, but unless you've seen this thread you wouldn't know about it. So other people would still be effected by the bug. Thats was also before I tested it and found that it mostly effects hot start jets which should be "ready to go" and as such shouldn't require a FCS reset to be flyable.

Have you tested it yet?

I have not ; the wife has kept me busy installing blinds . I have no reason to dispute your findings in any case . I have a better understanding of them with your last post mentioning "workaround" .

Ok , i think i understand the confusion re trim . As stated in the Natops , which also indicates that the Hornet does indeed fly differently than other aircraft , the FCS auto-trim , and the pitch trim bias , flies for g , not attitude . The FCS normally attempts to auto-trim for 1g . The bias introduced by the trim switch is for g as well . I flew an instant action free flight mission over the Caucasus , at altitudes between 5000 and 10000 ft , and entry speeds between 350-500 knots . On holding pitch down trim and neutral stick , the aircraft unloaded gs at a rate of about .1 per second , at lower altitudes and speeds ., and somewhat less at the higher altitudes and speeds . Being a g-trim and not an attitude trim , when i let go of the trim switch (5 sec) , the nose continued to drop , holding the same pitch rate , with the result being approximately a 20 degree dive on trim release , and 30 degrees a couple of seconds later . Very dramatic ! The same figures applied to nose up trim . Natops reference :

 

11.1.3 Auto Flap Configuration. The FCS control laws create slightly different handling qualities

than those of most aircraft. The most apparent characteristic is the excellent hands-off stability.

Damping about all axes is high. Static longitudinal stability is neutral since the FCS attempts to keep

the aircraft in 1 g, zero pitch rate flight. Longitudinal trim is used to bias (adjust) the reference load

factor or pitch rate as the pilot desires.

However , the aircraft CAN allow pitch trim for attitude , by use of the autopilot in attitude mode . Natops reference :

 

2.9.2.1 Autopilot. ATTH

 

At this time the aircraft maintains the existing pitch attitude.The pitch attitude hold reference can be changed with

pitch CSS to any value between ±45° pitch. The pitch attitude reference can also be changed with the

trim switch on the control stick at a rate of 0.5°/second.

 

(Edited for clarity)

 

Note the relatively slow speed of the attitude change:)

Just tested:

 

Pitch trim works fine. At 500kn I was able to trim the aircraft to fly both a 0G and 2G hands off. It is not as fast or responsive as other aircraft but it works.

 

I also did a few Flaps Auto takeoffs and had no problems. But during the cold startup I would exercise the flaps from full back to Auto as you should after the FCS reset.

Wow, what a many posts after....

I tested again last night about 40min just this trim bug or issue.

I think all of you include me, did not test it enough before.

I found that Elevator Trim in Auto Flap mode is work at the plane is fast or slow. my previous report about not work in high speed is wrong.

But, I found another bug instead that that elevator trim is not work sometimes whether plane is fast or even in slow. It means the trim SW is not work, when you push and hold(quite strange trim..), sometime the trim indicator and pitch is not move. You can find it easily when you test more than some minutes. About 30% or more in testing it happens.

So, my conclusion of Auto Flap trim is, it works and we should push and hold it because it's movement is so so so small. I think ED should check that small amount of movement is rational. And, it has a bug that sometimes the elevator trim is not work in Auto Flap mode. It is obvious. I tested enough time.

That may be so Shagrat but I've personally seen display F-18s do Flap Auto takeoffs for whatever reason so the aircraft can do it. At least in display config. Providing you cycle the flaps before takeoff Auto works ok on takeoff in DCS currently, not that I use it. I think the pitch up bug comes from not cycling the flap state after spawn or FCS reset.

 

What a great video.

The flap is 0 on the ground in takeoff. It means it is Auto Flap mode!

And it recover easily...

ED should see it and ask to that pilot about why he did not follow the correct procedure!

ED should see it and ask to that pilot about why he did not follow the correct procedure!

Because he's about to do exactly what the OP described:

takeoff with auto flaps then the Hornet pretty much tries to ... (do a) loop straight off the end of the carrier / field.

???

" I think all of you include me, did not test it enough before."

Because it is not how the Hornet is flown

"think ED should check that small amount of movement is rational"

trim switch on the control stick at a rate of 0.5°/second-from the Natops

"But, I found another bug instead that that elevator trim is not work sometimes whether plane is fast or even in slow. "

Or maybe your trim switch is intermittent ?