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

[PPPAnimal]

If you take off with auto flaps in f18 the plane will pitch up constantly.

Even full trim will not keep the nose down.

F2 view shows flaps are up.

only way to stop pitch up is to slow to below 250, lower flaps then return them to auto.

all is fine after that.

 

If you take off with full flaps, this problem does not occur.

[BIGNEWY]

Hi

 

Please post a track replay showing the issue.

 

thanks

Edited August 13, 2019 by BIGNEWY
for more info

[Moafuleum]

Takeoff is usually carried out with half flaps and T/O trim. To set takeoff trim, there is a button on the left console. With flaps to auto and gear up, the plane automatically establishes a 1g flight, so no pitch up should occur. With landing gear down the FCS logic is different, however above 250 kts the landing gear must be up to prevent damage.

[discwalker]

I own the Hornet since the first day.

Twice I had a wrong pitch up trim situation with heavy payload takeoff with HALF flaps.

I saw the wrong trim in Rctrl+ENTER view!

I suspect bug.

I must done: decelerate and then lower flaps then MANUALLY trim plane to neutral, then flaps up.

[Eldur]

There's only one reason to take off with auto flaps - reduce drag on the takeoff roll. To do that, I went over to begin with auto flaps and stick full fwd (with TO trim set they're roughly neutral then), but then lower them to half and stick centered at about 100-120 knots, then I don't get a Flanker Emulator and my Hornet behaves as expected.

[PPPAnimal]

F18 only has

 

auto flaps, normal position

half flaps

full flaps

 

so when your in auto flaps 99% of time you may forget and leave it in auto

while taking off. If you do you can't fly right after take off till you slow to below 250,

put flaps full, then back to auto and all is fine.

 

Just was not sure if this was realistic feature or a bug.

[majapahit]

There is somewhat of a bug with auto/flaps and gear configuration and steep climbing, I've noticed a handful of times but ever more rarely with every update. If at all it happens it's when you're manhandling gear and flap position in a very awkward moment of the flight envelope, landing or taking off.

You buttons having a hiccup does not help either, I've noticed.

Just restart your flight if pushing a lot of buttons does not fix it. No doubt ED knows its there, and prob hidden very deep indeed, and there are far more urgent things planned. BTW this subject has been neaten to death already, today's FA/18C behaves quite nicely nearly all of the time I'd say, one day this whole matter will simply be forgotten.

Edited August 11, 2019 by majapahit

[Sierra99]

Just was not sure if this was realistic feature or a bug.

 

It's not a bug.

[BIGNEWY]

Hi PPPAnimal

 

Just be aware of the forum rules before posting

[PPPAnimal]

ah np, sorry bud.

[PPPAnimal]

Ok then... lets say it this way.

 

Every one is entitled to their opinion, however, before chiming in on a bug report, you should first do your homework.

 

If you do a simple search you can find the manual from the makers of the f18 that backs up the fact that all 3 modes of the flap system by design run the same Flight control Software and preform the same once over 250.

 

So even if you take off with auto flaps, once you get over 250, the pitch up effect should end.

If you take off with half flaps, or even full flaps, there is a pitch up effect also, but the flaps go into auto flap mode and retract at 250 and the pitch up effect ends.

 

read up on it from the people that made it.

[Break]

I can confirm this. If you forget to set your flaps and take off, the hornet will pull up violently and will require a good amount stick input to somewhat stabilize. Trimming it out is possible though.

 

My knowledge isn't enough to say whether this is a bug or a feature. Maybe it has something to do with T/O trim not being deactivated automatically after takeoff?

[noisy_lightning]

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).

[Deano87]

The Blues takeoff in Auto for various parts of their shows and I’ve also personally seen display jets takeoff in Auto over here in Europe. So it’s definitely a bug. Also I believe if you cycle the flaps down and then back to auto it will takeoff OK from when I last tried, but that was a while ago.

[noisy_lightning]

The Blues takeoff in Auto for various parts of their shows and I’ve also personally seen display jets takeoff in Auto over here in Europe. So it’s definitely a bug. Also I believe if you cycle the flaps down and then back to auto it will takeoff OK from when I last tried, but that was a while ago.

 

The Blues have custom software on their jets (listen to the Fighter Pilot Podcast Episode) so I wouldnt take into account what they can do compared to the front line jets as common.

[cofcorpse]

The Blues takeoff in Auto for various parts of their shows and I’ve also personally seen display jets takeoff in Auto over here in Europe. So it’s definitely a bug.

 

Why are you so sure? The Blue Angels have modified jets, with modified FCS, so you can't compare normal jet with theirs.

 

If you do a simple search you can find the manual from the makers of the f18 that backs up the fact that all 3 modes of the flap system by design run the same Flight control Software and preform the same once over 250.

 

You are not quite correct. You forget about transition between modes.

If you don't want nose up behaviour after takeoff, just put flaps to AUTO or decrease your trim to 0. T/O trim is designed for HALF flaps takeoff

Edited August 13, 2019 by cofcorpse

[Py]

It's not a bug.

 

Actually I think it IS a bug.

Sure takeoffs shouldn't be done in auto flaps, but something seems to be wrong with the flight model if you do.

 

I thought it might be the FCS doing something odd due to the incorrect procedure so I tried watching the stabilizers while "resetting" the violent pitch up with a quick auto-half-auto on the flaps switch (too fast for them to actually move).

If it was the FCS, I would expect a sudden change in the pitch of the stabilizers as it is "reset" and stops trying to pull up hard.

I saw no visible movement at all after the "reset", but the plane suddenly stopped pulling up, suggesting that it is not actually the control surfaces causing the odd behaviour.

That would definitely be a bug if the plane is being influenced strongly by something besides the control surfaces.

I'll watch the other surfaces when I have time, but such a strong pitching moment seems unlikely to be possible with the other control surfaces at low speed.

[Northwind]

AUTO flaps,decrease trim to 0(STAB 0 on FCS page),takeoff with AUTO flaps,still pitch up.

Half flaps, decrease trim to 0(STAB 0 on FCS page),takeoff with AUTO flaps,still pitch up.

[Kazius]

It is the fly by wire system causing the pitch up if you take off without takeoff flaps (half flaps).

[majapahit]

do a 360 roll and you're good

[Hog_No32]

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

[Deano87]

Why are you so sure? The Blue Angels have modified jets, with modified FCS, so you can't compare normal jet with theirs.

 

The blues have a custom avionics package as far as I know. With various warning deletes (like Auto flap on takeoff) and various other airshow related stuff like distance to show centre point and timing related things but I don’t believe the FCS is changed in any meaningful way, I’m happy to be proven wrong on that however.

 

I’m pretty sure all the European hornets I’ve seen doing auto flap takeoffs over here do not have modified FCSs as well, as they are not specifically display jets and also get used for normal operations.

 

There is no way the jet should pitch up uncontrollably from a flaps auto takeoff. There is no reason for it to be designed that way. And there is plenty of evidence of normal, unmodified F-18s doing flaps auto takeoffs without any pitch up issues. It’s a bug.

 

A bug that doesn’t really effect anybody who wants to fly the jet normally outside an airshow routine, but a bug none the less.

[cofcorpse]

And there is plenty of evidence of normal, unmodified F-18s doing flaps auto takeoffs without any pitch up issues.

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.

 

It’s a bug.

No, it's not, unless proven

[Deano87]

I don’t have any evidence of F/A-18Cs being flown by the US Navy doing flaps AUTO takeoffs and not having the pitch up problem, If that’s what you’re asking for.

 

All the jets I’ve seen do it are Blue Angel or Swiss F/A-18Cs, as well as some other ones as well over the years.

 

But it makes no sense from a safety standpoint to have an aircraft that will uncontrollably pitch up like that if taken off in the incorrect config, specially when you can program the FCS to just revert back to the 1G trim state once the WOW is released.

 

I’m not saying take my word for it. Talk to your SMEs, hit up Jello from the fighter pilot podcast. He’s bound to have either done AUTO flap takeoffs or know somebody who has.

[maxTRX]

You guys are still tackling auto flaps T/O, PA mode transition to > then T/O pitch up, reset to pitch trim when bolter/T&G with any 2 wheels hitting the deck and... other FCS features that I have no idea about...:lol:

I'm re-writing NATOPS here!:music_whistling: :

 

I'm not making any wake turbulence, hehe

Edited August 13, 2019 by Gripes323