[NO BUG]take off auto flaps - f18 - pitch up?

If you allow me to express my opinion on this: I‘d rather prefer the ED team to work on systems and features for those that want to fly the Hornet realistically and follow the correct procedures instead of modelling the behavior of the jet when not following the procedures. Unless time and resources permit...

 

Really no offense here, just my personal opinion

That’s my feeling too.

Could you share some of them, please? Not Blue Angels, F/A-18A/B, Canadians and others. Only USMC/NAVY F/A-18C/D, please.

 

 

No, it's not, unless proven

Read the flight manual. I had posted links to it here but they were deleted due to rules. The manual states the fact that all 3 modes work the same once 250 speed is reached.

Even the f18 modeled by ED works this way for every other condition.

take off with full flaps or half flaps, don't switch to auto, you can fly around all day and they will do what they would on auto, you have a amber light telling you your in full flaps, but still it runs in auto mode till you get below 250 again.

This is what the manual states also.

Here is a message exchange I had with the Swiss Hornet display pilot.

In my opinion whilst this may not technically be a bug I find it hard to believe from a purely Human Factors & Flight Safety point of view that the real F18 would ever act like this on a take off with auto set (yes I know it shouldn't happen, but mistakes do happen periodically).

What’s so hard to believe. From a flight safety point of view there are a thousand things that can kill you every time you leave the ground. Failing to perform any of a hundred procedures correctly each flight can lead to death dismemberment and destruction.

In the case of the F-18C it is the tendency to pitch up violently during takeoff if you do not set the flaps properly. So it is practiced and stressed that not setting the flaps correctly will kill you.

This isn’t a case of it shouldn't happen. This is a case of it being drilled into a persons head “If you dont do this correctly you will die.”

It’s not a bug. It’s a simulation of a combat aircraft flown by professionals.

Sierra, I can’t find anything in the -000 about this violent pitch up. Can you direct me to the appropriate chapter/page where It explains that if you attempt a takeoff in AUTO the aircraft will uncontrollably pitch up and require a cycle of the flaps to reset the FCS. Such a serious handling fault would no doubt be documented in the Natops manual, where all other handling oddities (including unusual configuration operations) are listed.

How do you know the real jet doesn’t violently pitch up on TO with AUTO? How do you know demo teams don’t have too apply forward stick and or neutralize trim as a result of that condition? Or that the pitch up is a desired behavior for their purposes? It sounded like that pilot used that setting specifically for a vertical zoom right after TO.

It’s part of the procedure for a reason, it throws a caution when the switch is in the wrong position for a reason. It’s not a mechanical flap switch, it’s an FCS mode switch, being in the wrong FCS mode at the wrong time is going to have consequences, that’s why we have procedures. So again how do you know it won’t pitch up in that condition?

Because I literally just asked the guy who flies the Swiss display jet and he said he pulls +2G after takeoff to the vertical. I’ll ask him some questions tomorrow and clarify what the DCS Hornet does and ask if that’s anything like what the real jet does.

I’m also trying to get in contact with a Blue Angel who can tell me exactly how the Blue Angel FCS is different from the stock jet, and how the stock jet would behave in the auto takeoff situation.

Now don’t misunderstand me. I don’t think this is an important bug, it’s not something that needs to be fixed with any priority, because it effects a relatively small amount of players. But if we are trying to make the most realistic commercial simulation of an F-18 possible then it should behave realistically even when people do unusual things. And to say “it’s not a bug until proven” is just the kind of poke I need to set me on the route to proving it, if only to cure my own curiosity.

I cannot find any evidence to support the assertion that the real jet does this, this includes talking to real Hornet pilots and combing through the Natops manual. IF the real jet does this then fine, but I don’t believe that it does. I will get to the bottom of it one way or another.

Also guys. Ever heard of Occam’s razor? What is more likely, a jet that cost billions and has an FCS system specifically designed to reduce pilot workload has this one critical failure mode... which isn’t noted anywhere in the manual for said aircraft.

Or

A flight sim doesn’t model an unusual configuration quite right...

I know but he also was only at +3 for trim not +12 and 2gs is awful low for a straight to vertical climb immediately after TO, unless the FCS was “helping” him, and he’s super light. Also I know for a fact hornet demo teams use bob weights for tight formation flying, which literally makes the stick harder to pull.

And I wouldn’t call it critical, it would only kill you if you didn’t take any positive action to correct it. I’m not saying it’s incorrect, just that if your outside guidelines, you can and should expect abnormal behavior. People other then you have posted about this before, and we found out they had configured the jet way outside of proper guidelines, and were blaming ED for their woes

We can’t call it a bug unless we know it should behave differently then what we’re seeing, that being said it’s gonna be hard to find real evidence of that because no professional would use those settings in actual operation, unless he/she had a specific reason such as the one you posted. Otherwise if they did have an accident they’d be at fault for not following guidelines. But yeah ask around someone’s gotta know.

I know but he also was only at +3 for trim not +12 and 2gs is awful low for a straight to vertical climb immediately after TO, unless the FCS was “helping” him, and he’s super light. Also I know for a fact hornet demo teams use bob weights for tight formation flying, which literally makes the stick harder to pull.

 

And I wouldn’t call it critical, it would only kill you if you didn’t take any positive action to correct it. I’m not saying it’s incorrect, just that if your outside guidelines, you can and should expect abnormal behavior. People other then you have posted about this before, and we found out they had configured the jet way outside of proper guidelines, and were blaming ED for their woes

 

We can’t call it a bug unless we know it should behave differently then what we’re seeing, that being said it’s gonna be hard to find real evidence of that because no professional would use those settings in actual operation, unless he/she had a specific reason such as the one you posted. Otherwise if they did have an accident they’d be at fault for not following guidelines. But yeah ask around someone’s gotta know.

The only Hornet team that uses “bob weights” is the Blue Angels and that’s actually a literal spring on the the stick which forces the stick forward. The other solo Hornet displays don’t use such a system.

He’s doing a 2G pull because of the gear retraction G limit and yes he is very light because he’s just got airborne for a solo display.

Sierra, I can’t find anything in the -000 about this violent pitch up. Can you direct me to the appropriate chapter/page where It explains that if you attempt a takeoff in AUTO the aircraft will uncontrollably pitch up and require a cycle of the flaps to reset the FCS. Such a serious handling fault would no doubt be documented in the Natops manual, where all other handling oddities (including unusual configuration operations) are listed.

You’re absolutely correct. I can’t direct me to the appropriate chapter/page where It explains that if you attempt a takeoff in AUTO the aircraft will uncontrollably pitch up and require a cycle of the flaps to reset the FCS. I ALSO can’t direct you to the chapter/page where it says landing with the gear handle UP...Alters the landing distance and requires more power to taxi to parking. Does that mean the ability to land with the dear UP is a bug?

Now that being said...I can direct you to step 13.b of the before Taxi checklist that directs

“FLAP switch - HALF”

Not “FLAP switch - As Desired”

Not “FLAP switch - AUTO”

Not “FLAP switch - FULL”

“FLAP switch -HALF”

This is the proper procedure. End of discussion. Everyone “yeah but-ing” is doing it wrong.

That is the procedural end to the argument. That being said as far as the uncontrolale pitch up is concerned...

It can be surmised that since FLAPS significantly increase available lift...Not setting the correct flaps would result in insufficient lift. It can be assumed Insufficient lift at the end of the cat shot would cause the flight control computer ito compensate for the missing lift By increasing the AOA...I.E.A violent pitchup.

But that’s probably not in the book either.

This is the proper procedure. End of discussion. Everyone “yeah but-ing” is doing it wrong.

Including the people that do it in the real jet? I’ll be sure to let them know you don’t approve.:megalol:

It can be surmised that since FLAPS significantly increase available lift...Not setting the correct flaps would result in insufficient lift. It can be assumed Insufficient lift at the end of the cat shot would cause the flight control computer ito compensate for the missing lift By increasing the AOA...I.E.A violent pitchup.

 

But that’s probably not in the book either.

Nice idea, Except that’s not the way the F-18 FCS works. With the flaps in AUTO the FCS tries to attain 1G of load on the jet. So yes it would pitch up to account for the less lift, but then once it reached 1G it would stop pitching up, instead of doing what it does in the sim which is continue pitching up. It’ll happily fly around pulling 5G when you let go of the stick if you don’t slow down and cycle the flaps at which point it goes back to flying normally. Also it does it even when taking off from a normal runway.

but he also was only at +3 for trim not +12

You know what Wizard, I’ll give you that, that’s a good point. That is a big difference in trim. I wonder if the initial trim setting on the ground influences the G figure that the FCS in AUTO is trying to attain, I’m not sure it should work like that but maybe it does in the sim. Maybe +3 is correct for 1G after the gear is up? I’ll experiment with this tomorrow.

Did a few tests (clean, 50% fuel) and while there is a very noticable pitch up, it's easy to counteract/control.

Since you are not a passenger and hence you should always actively control your aircraft, this would not be a real problem.

The main problem comes from an apparently wrong trim simulation if you take off with the flaps in auto!

Resetting the trim before take off is somewhat sursprising.

1. flaps half > decrease trim from +12° to 0° = 6sec

2. flaps auto > decrease trim from +12° to 0° = 120sec, that's 0.1°/sec!

3. Half flaps (+12°), mil thrust, full aft stick at 110 (to confirm 24° stab deflection), neutral stick at 20° pitch attitude and the stab deflection will be around +3°

The pitch attitude will continue to increase, the climb speed will initially increase to ~190kts but will decrease to 110kts with the highest pitch attitude being a tad over 50°. So you have the dreaded 'pitch up' with half flaps as well.

4. auto flaps (+12°), mil thrust, full aft stick at 110 (to confirm 24° stab deflection), neutral stick at 20° pitch attitude and the stab deflection will be around 9° with a much higher pitch up which will quite a bit of forward stick to counteract.

4a. with auto flaps and the trim reset to 0°, the stabs will 'reset' to ~5° after take off rotation with a less aggressive pitch up.

The main problem is that the stab trim still runs at 0.1°/sec which means it's completely ineffective since the FCS is much faster, hence the impression that trim doesn't have any effect.

But the trim is actually not moving at all.

4a. with auto flaps and the trim reset to 0°, the stabs will 'reset' to ~5° after take off rotation with a less aggressive pitch up.

Really interesting stuff bbrz! Thanks for that. With the above point, what G would the jet try and attain once you let it accelerate? And could you trim from the ~5° stab position back to 1G normal? Or wasn’t that possible?

Once you have established the +20deg pitch attitude the plane will initially continue to pitch up with approx 1.6-1.7G.

If you take off with auto flaps and +12deg stab trim, the stabilators will very quickly reset to the same +5deg after reaching the+ 20deg pitch attitude, like in the 0deg trim case and the result will be the same 1.6-1.7G pitch up.

You can trim to 0deg, but this will take around 1min!

It maintains that g-loading up to 500 knots? Or does it scale with speed?

No. The 1.6G occur between 20-30deg pitch. With increasing pitch attitude the G-load decreases, to less than 1 as she reaches the top of the (unintenional) loop.

Interestingly with decreasing G-load the FCS increases the stab deflection to around +18deg at 80kts.

do a 360 roll and you're good

Tested, Not True. Do your homework.

I must thank all those who are researching this and testing stuff out and reading the manufactures flight manual. You words weight a lot more than those spoken from flamers.

It is true that if such a violent pitch up did exist in the real jet that this would in fact be noted in the manual, yet it is not.

It is true that if this did have a negative effect that required a cycling of flaps to correct that no pilot would take off in auto flaps on purpose just to slow to below 250 and cycle flaps afterward.

Yet real pilots have and do take off with auto flaps. Some on purpose, some not.

If this was not documented how would a pilot know that he needed to cycle flaps to correct it?

Its not documented, because he doesn't need to know, because it doesn't happen.

If it did, and even if you could trim to get the aircraft to fly level again, this is not correct fix either, since the flight control system is still inputting some flap, which was causing the extra lift, and pitch up. trimming the jet does not change the flap input, it changes elevator input, thus you would have extra drag etc from flaps.

You’re absolutely correct. I can’t direct me to the appropriate chapter/page where It explains that if you attempt a takeoff in AUTO the aircraft will uncontrollably pitch up and require a cycle of the flaps to reset the FCS. I ALSO can’t direct you to the chapter/page where it says landing with the gear handle UP...Alters the landing distance and requires more power to taxi to parking. Does that mean the ability to land with the dear UP is a bug?

 

Now that being said...I can direct you to step 13.b of the before Taxi checklist that directs

 

“FLAP switch - HALF”

 

Not “FLAP switch - As Desired”

Not “FLAP switch - AUTO”

Not “FLAP switch - FULL”

 

“FLAP switch -HALF”

 

This is the proper procedure. End of discussion. Everyone “yeah but-ing” is doing it wrong.

 

That is the procedural end to the argument. That being said as far as the uncontrolale pitch up is concerned...

 

It can be surmised that since FLAPS significantly increase available lift...Not setting the correct flaps would result in insufficient lift. It can be assumed Insufficient lift at the end of the cat shot would cause the flight control computer ito compensate for the missing lift By increasing the AOA...I.E.A violent pitchup.

 

But that’s probably not in the book either.

In fact landing with gear up without the realistic effects you mentioned would be a bug. Who wants to watch someone land wheels up, taxi to parking, rearm and then take off? Kind of a immersion breaker you think?

This program is said to be a Sim, not a game. Thus its goal is to simulate a machine with a similar set of controls designed to provide a realistic imitation of the operation of an aircraft.

Simulation can be used to show the eventual real effects of ALTERNATIVE CONDITIONS AND COURSES OF ACTION while being used for training purposes.

When you buy a new plane, it is called a study module. If you wanted a game you could spend a whole lot less and go play War Thunder.

It should be in your interest and everyone else to get it right. Not convince others that the only way to take off is with half flaps, because that's just not true.

If your interested in some more interesting reading on the topic with flight

videos showing the f18 taking off in auto flap mode there is a topic here

Flaps UP for take off in real life

https://forums.eagle.ru/showthread.php?t=215043

In fact landing with gear up without the realistic effects you mentioned would be a bug. Who wants to watch someone land wheels up, taxi to parking, rearm and then take off? Kind of a immersion breaker you think?

I guess you're to focused on the perceived issue to detect a joke...

This program is said to be a Sim, not a game. Thus its goal is to simulate a machine with a similar set of controls designed to provide a realistic imitation of the operation of an aircraft. Simulation can be used to show the eventual real effects of ALTERNATIVE CONDITIONS AND COURSES OF ACTION while being used for training purposes.

What you call "ALTERNATIVE CONDITIONS AND COURSES OF ACTION" is failing to follow NATOPS procedures and Tech Data. Apparently there are demonstrations teams that takeoff with Flaps in Auto. The Blues don't. This video clearly shows they have flaps set as they taxi and takeoff.

However, I will concede that to my untrained eye it doesn't look like traditional "HALF" Flaps. It may be they get a different "Half" setting with their OFP. But the important thing is you have zero relevant information and command guidance regarding how they perform these maneuvers. Air speeds limitations? Fuel loads? Trim Settings? Takeoff CG? There is way more to it than just flipping the Flap switch and zooming off for the crowd no matter WHAT country you're flying for.

When you buy a new plane, it is called a study module. If you wanted a game you could spend a whole lot less and go play War Thunder.

Operating the aircraft IAW Tech data makes it a study module, Doing things that violate tech data is playing War Thunder.

It should be in your interest and everyone else to get it right. Not convince others that the only way to take off is with half flaps, because that's just not true.

The -000 Disagrees. Find a copy of the NATOPS and Check page V-12-13. In the explanation for DDI Cautions and Caution Lights it states:

Indicator: CK FLAPS

CAUSE/REMARKS: FLAP switch in AUTO position at takeoff.

CORRECTIVE ACTION: 1. Place FLAP switch in correct position for takeoff.

I'm not trying to convince you of anything. I am simply telling you AUTO...is not the correct position according to the NATOPS manual. If you operate the sim IAW the NATOPs guidelines and restrictions...It works fine.

Did a few tests (clean, 50% fuel) and while there is a very noticable pitch up, it's easy to counteract/control.

Since you are not a passenger and hence you should always actively control your aircraft, this would not be a real problem.

 

The main problem comes from an apparently wrong trim simulation if you take off with the flaps in auto!

 

Resetting the trim before take off is somewhat sursprising.

 

1. flaps half > decrease trim from +12° to 0° = 6sec

2. flaps auto > decrease trim from +12° to 0° = 120sec, that's 0.1°/sec!

 

3. Half flaps (+12°), mil thrust, full aft stick at 110 (to confirm 24° stab deflection), neutral stick at 20° pitch attitude and the stab deflection will be around +3°

The pitch attitude will continue to increase, the climb speed will initially increase to ~190kts but will decrease to 110kts with the highest pitch attitude being a tad over 50°. So you have the dreaded 'pitch up' with half flaps as well.

 

4. auto flaps (+12°), mil thrust, full aft stick at 110 (to confirm 24° stab deflection), neutral stick at 20° pitch attitude and the stab deflection will be around 9° with a much higher pitch up which will quite a bit of forward stick to counteract.

 

4a. with auto flaps and the trim reset to 0°, the stabs will 'reset' to ~5° after take off rotation with a less aggressive pitch up.

 

The main problem is that the stab trim still runs at 0.1°/sec which means it's completely ineffective since the FCS is much faster, hence the impression that trim doesn't have any effect.

 

But the trim is actually not moving at all.

As I understand it pitch trimming while in AUTO doesn’t directly change stab position, rather it sets the bias to higher or lower then 1G flight. While trimming in HALF/FULL actually sets the stab position.

If this would be the case, auto flap takeoffs would be almost impossible IRL since you would need way too much time to re-trim after takeoff.

And why would the stab trim move at all when trimming on ground?

Looks like either the trim rate in auto is way too low or the pitch up in auto way too high ;)

edit: know issue, confirmed by ED

1 AUTO setting is meant for flight, the aircraft trims itself for you. So once airborne in AUTO flaps there should be no need for trimming in pitch at all.

2 No Idea, when I try to trim the aircraft in pitch on the ground with flaps at AUTO the stabs don't move.

3 Could be, glad they're on it. But I never use pitch trim in normal flight with flaps at AUTO because I always want the aircraft trimmed for 1G flight, the only time I could see changing that would be for battle damage/emergencies and even then its hard to imagine a situation that would require less or more the 1G constant in normal flight.

Edit*Maybe that's the real issue we're seeing; IRL the aircraft dose pitch up like in DCS but it's also easier to compensate with trim IRL.

I guess you're to focused on the perceived issue to detect a joke...

 

 

What you call "ALTERNATIVE CONDITIONS AND COURSES OF ACTION" is failing to follow NATOPS procedures and Tech Data. Apparently there are demonstrations teams that takeoff with Flaps in Auto. The Blues don't. This video clearly shows they have flaps set as they taxi and takeoff.

 

 

However, I will concede that to my untrained eye it doesn't look like traditional "HALF" Flaps. It may be they get a different "Half" setting with their OFP. But the important thing is you have zero relevant information and command guidance regarding how they perform these maneuvers. Air speeds limitations? Fuel loads? Trim Settings? Takeoff CG? There is way more to it than just flipping the Flap switch and zooming off for the crowd no matter WHAT country you're flying for.

 

 

 

Operating the aircraft IAW Tech data makes it a study module, Doing things that violate tech data is playing War Thunder.

 

 

 

The -000 Disagrees. Find a copy of the NATOPS and Check page V-12-13. In the explanation for DDI Cautions and Caution Lights it states:

 

Indicator: CK FLAPS

CAUSE/REMARKS: FLAP switch in AUTO position at takeoff.

CORRECTIVE ACTION: 1. Place FLAP switch in correct position for takeoff.

 

I'm not trying to convince you of anything. I am simply telling you AUTO...is not the correct position according to the NATOPS manual. If you operate the sim IAW the NATOPs guidelines and restrictions...It works fine.

Very nice of you to provide a video that helps prove my point. Fast forward to 14 mins, and watch the last two jets take off. Surely you will agree they are in auto flaps mode.