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Old 06-06-2018, 11:33 AM   #1
etienne1968
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Default Trim erratic behavior

Hi everyone,

I just share my personal opinion about that recurring topic : Trim. Yesterday I performed numerous flight tests to explore the trim behavior, especially during approach phase with landing configuration. Infact I was amazed by the encountered struggle to stabilize that aircraft once gear extended and flaps full at approache speed. I know many simmers already reported that issue, some replied it's normal stuff and the only way to handle this is practice and practise…

I'm curious to have the official return from ED about that, is Trim and auto-trim functions still worked out for a next release or is it final in the early access ?

My pleasure to fly the Hornet, amazing product by the way, is killed by the final phase of the flight. Just for information towards those talking about the auto-trim function, for sure it's working permantly in this FBW aircraft, either flying manually or autopilot engaged. Just display the FCS page on any DDI and check out visually auto-trim interaction flying manually the bird in landing configuration.


I was fortunate to experience the actual simulator long time ago, being a french contributor for a magazine dedicated to flight simulation, and it was perfectly stable in downwing when extending gear and flaps. I mean the pitch down couple was perfectly manageable unlike the flight model in DCS. And you will notice, extension of the flaps full before the gear will change the aerodynamical behavior and make things easier for those struggling to to stay level.
For information the VRS F18 behavior in landing configuration is way better. That software editor is licensed to deliver the professionnal flight model for a PC based "study level" training solution.

I've been flying for 30 years, currently Airbus 320 Captain, a Fly By Wire aircraft fully auto-trimmed from the F18 generation. By definition, the FBW, especially for a fighter, makes an "unstable aircraft" stable for the pilot.
By the way to close any debate about trim usage, the aircraft must trimmed everytime the speed is changing. So for a given speed and configuration, there is one trim position. Then after do not touch it again otherwise you'll have to fight permanently against the odds to stabilise the bird on its trajectory.
As a rule of thumb, in my opinion and from what I observed : in downwind, extend the flaps first and maintain the Velocity vector on the horizon, adjusting thrust accordingly. Then lower the gear, adjusting again the thrust. Observe the auto-trim interaction. keep in mind the parameters for the next time you fly :
Thrust N1 : roughly 94%

Elevator Trim : around 9
That's all folks
Happy flights
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Old 06-06-2018, 11:46 AM   #2
David OC
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This is a known issue with the FBW / flaps

It needs tweaking for sure, you can even talk to an engineer here about it if you like. Just early access, she will be in the oven for a little, there are plenty of things missing off those other sims, as Curly can point them all out for you to.

You should also read up on his post trying to explain to a pilot with 30 years about the backside technique, as most pilots outside the USN have no experience flying this way.

Also this one here.

His hook to eye post is really good to if your up for a read.

They have F/A-18 pilots working with the Flight model coders.

She still fly's nice, here is a nice stable trimmed onspeed landing in calm weather with very little if any pitch.


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Old 06-06-2018, 11:55 AM   #3
Nate--IRL--
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Would I be right in saying that Trim only operates in the "Not Auto Flaps Up" flight mode?

Nate
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Old 06-06-2018, 12:10 PM   #4
=4c=Nikola
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No, it works in "Auto Flaps Up" flight mode as well, but it's (in plain words) "slow". I was able to trim it for inverted flight (-1g) by holding trim button for 1 minute.
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Old 06-06-2018, 12:10 PM   #5
Elysian Angel
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Quote:
Originally Posted by Nate--IRL-- View Post
Would I be right in saying that Trim only operates in the "Not Auto Flaps Up" flight mode?
Yes and no: when you are not in "dirty" configuration (undercarriage down and flaps down), there is no need for pitch trim. However, you'll still need roll trim to compensate for asymmetric loadouts, for example right after firing a Sparrow.
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Old 06-06-2018, 12:21 PM   #6
etienne1968
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Quote:
Originally Posted by Nate--IRL-- View Post
Would I be right in saying that Trim only operates in the "Not Auto Flaps Up" flight mode?

Nate
Sorry buddy, I can’t give more details about the way the aircraft is designed. Some flight controls engineers might be elaborating the topic. From my perpective, as an Airbus pilot, military aviation enthusiast, I can only say once the relationship between auto trim function and aircraft configuration is fixed in a later release, it’s gonna be heaven. Writing many articles related to military flight simulation in the 90’s, I was invited to fly the actual simulator for : Mirage 2000, F18, Dassault Rafale. I’m very close to active French fighters, some returning from the US flying F16 for 3 years. What I can say is, flying manually any modern fighter fitted with FBW flight controls is a peace of cake. When you’re given the option to trim manually the aircraft, it’s a manufacturer design option in order to make the pilot feeling the bird like a conventional aircraft. By nature, the trim is basically a secondary flight control, relieving the pilot input on the stick to maintain a given attitude (roll, pitch). Unfortunately, flying a PC software with no physical feedback from your input on the stick, it’s pretty complicated to understand and handle the trim effect when you never flew an actual aircraft. That’s why you must be knowledgeable about the theory : select the speed you want to fly at a given configuration and then trim the bird in such a way when you release the stick the velocity vector is stable. Then do not touch again the trim control, it would be detrimental to your primary goal : flying easily the trajectory in order to focus on your soldier task : operating a warfare complex system...
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Old 06-06-2018, 12:27 PM   #7
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Quote:
Originally Posted by Elysian Angel View Post
Yes and no: when you are not in "dirty" configuration (undercarriage down and flaps down), there is no need for pitch trim. However, you'll still need roll trim to compensate for asymmetric loadouts, for example right after firing a Sparrow.
OK - that makes sense to me - slowly beginning to get a feel for the Hornet. Too used to the Sukhois and trimming constantly.

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