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FOXFIRE TWOONE
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Does anyone else think the trim is too sensitive, or is it possible it's my joystick, x52. I have trimming on my ( hat 1 ) and I just tap it but I am constantly correcting after each tap to fine center. :joystick:

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  • 3 months later...

I was gonna post about this. I also have the X52 and trim mapped to the central hat on the stick. I keep trimming because I can't find the sweet spot, the trim is incredibly sensitive and moves maybe too fast.

 

Would be good to hear what other people think.

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Yes i agree. Trim on sabre is really super sensitive. Its almost impossible to find a good position for level flight. Im flying with Warthog.

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Two things:

 

1) Trim, in general, is really only supposed to relieve stick forces, not to let you fly hands off. As such, it's great for the FFB users, not so much for the rest of us.

 

2) Have you got any proof/documentation about the trim system you can supply to BST regarding button durations and trim amounts being excessive? Or even pilot accounts? It's something I've not read about so I'm curious. It may be that the F86 had a very sensitive trim response and the module is correct.

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Two things:

 

1) Trim, in general, is really only supposed to relieve stick forces, not to let you fly hands off. As such, it's great for the FFB users, not so much for the rest of us.

 

I beg to differ: elevator trim is a major component of any aircraft, and it's considered an emergency if it doesn't work. Try to fly for 2 hours without trimming and you'll probably have muscle cramps. There are cases in which aircraft crashed because of trim failure...

 

 

2) Have you got any proof/documentation about the trim system you can supply to BST regarding button durations and trim amounts being excessive? Or even pilot accounts? It's something I've not read about so I'm curious. It may be that the F86 had a very sensitive trim response and the module is correct.

 

Unfortunately I don't have any hard proof regarding this. Does BST have any? Can they expand on why the trim has such fast reaction time?

In general, I think logic and usability are what guided the choices of the engineers for the real aircraft.

 

The only pilot account I have is from my grandfather who flew the F-86E (Canadair Cl.13 Mk IV) among a few other types.

He says the aircraft itself was very responsive, but not uncomfortably sensitive. He said it was pretty hard to fly in close formation and for small adjustments they used mainly the trim switch. I specifically asked him if the aircraft was hard to trim, he said no, the trim was very precise (hence why they used it in close formation flying to do minute adjustment) but also the aircraft was more sensitive to smaller airspeed changes and required more trimming compared to the F-84 that was "like a truck".

He's 86 now, the memory about cockpit switches and so on is fading a bit but he recalls the flying characteristics quite well it seems. He flew T-6, T-28, P-51 (just a few hours) and the T-33 before moving onto the F-84G and then the Sabre.

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Can you say which version you are in.

I'm in v 1.5.3 and the trim is very fine and precise and just about as perfect as you could want. (X52).

 

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Can you say which version you are in.

I'm in v 1.5.3 and the trim is very fine and precise and just about as perfect as you could want. (X52).

 

..

 

I'm also in the latest 1.5.3 version

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I beg to differ: elevator trim is a major component of any aircraft, and it's considered an emergency if it doesn't work. Try to fly for 2 hours without trimming and you'll probably have muscle cramps. There are cases in which aircraft crashed because of trim failure...

 

Not sure what you are driving at here...?

 

Buzzies is correct. Trim removes stick forces. Not for allowing hand's off flight.

 

He's not saying that trim is unnecessary. Flying without trim will cause muscle cramp because of the required stick force to hold attitude. Which you would remove with trim... so...

 

[edit] Possibly you're confused by his FFB comment. In general a non-force feedback stick always feels like a correctly trimmed aircraft. So the simulated trimming doesn't give you a feel response. Is what he's driving at. Not that trim is unnecessary.


Edited by dotChuckles

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Yes i agree. Trim on sabre is really super sensitive. Its almost impossible to find a good position for level flight. Im flying with Warthog.

 

I get your point about trim sensitivity in the F-86, but with the Warthog HOTAS you can make all kinds of adjustments to the trim input by using script.

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Not sure what you are driving at here...?

 

Buzzies is correct. Trim removes stick forces. Not for allowing hand's off flight.

 

He's not saying that trim is unnecessary. Flying without trim will cause muscle cramp because of the required stick force to hold attitude. Which you would remove with trim... so...

 

[edit] Possibly you're confused by his FFB comment. In general a non-force feedback stick always feels like a correctly trimmed aircraft. So the simulated trimming doesn't give you a feel response. Is what he's driving at. Not that trim is unnecessary.

 

Exactly that. Upon re-reading the FFB bit does make it a bit of an obtuse statement.

 

But yes, it's to relieve stick forces, not to allow you to fly hands off, ergo, "perfect" trim isn't really possible if that's what people are expecting to be able to do.

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  • 2 weeks later...

Picking up on this 'Trim' thread for two reasons.

 

1. I agree about the overly sensitive trim. One (even fast) tap on the HAT and you go from a few degrees nose down and a healthy rate of descent to a few degrees nose up and a healthy ascent. It's not possible to trim it to within a reasonable point of level flight and it just doesn't seem right. You certainly can't use it for fairly fine formation flying and light stick work.

 

2. When I spawn the Sabre the tail is trimmed very nose-up (tailplane rear edge very high). On takeoff the a/c will lift off the ground with little effort at around 130kts but it immediately goes very nose high. If I trim the tail surface to be parallel to the curve of the rear fuselage (about 5 seconds of trim-press and it looks fairly neutral) it takes a good pull to get it off the ground but it doesn't then rear up. I can do this with full flap (around 130 kts) , no flap (around 150 kts) or about 2/5 flap (130kts). Another odd thing is that after takeoff with any amount of flap I raise the flaps and the nose rears up when it retracts through the last ~2/5 flaps then it settles down. I'm very familiar with the concept of change of attitude with flap but it all seems to happen with the last part of the flap travel, before which it is reasonably stable. Is this correct?


Edited by klem

klem

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Klem.

 

On the first point, on a level 400 kts, it takes me 10/15 clicks to enter a shallow dive to achieve 500 kts, then 15 to bring it back, then about 10 to level off. (X 52). Perfect for me.

The tail is supposed to be nose high trim, there is a black line on the fuselage for ground crew to check .

The last 2 secs. of flap rear up doesn't feel right, as it's supposed to sink, so I use 3 secs. up and stop, then the last 2 secs. and fwd trim at the same time. I don't feel that this is correct. Then accelerate to 450 kts for the climb. (Clean and wind removed, Saitek X 52).

 

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Not sure if this is simulated, but in the real-world, the aircraft was "trimmed" only at 0.6 mach. There's a graph of mach vs stick force (push/pull), that if I was smarter, I would know how to post.

 

Below 0.6 mach, you are suppose to have to pull on the stick to maintain level flight. Push, for speeds above 0.6 mach. When you approach 0.9, strange things happen. You'll go from needed 5lbs of push to 5lbs of pull at 0.9 mach. Then it change exponentially to an ever increasing push as you approach the speed of sound.

 

My source is the Haynes F-86 book, and they've copied the graph from what probably is a the pilot's flight manual.

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Not sure if this is simulated, but in the real-world, the aircraft was "trimmed" only at 0.6 mach. There's a graph of mach vs stick force (push/pull), that if I was smarter, I would know how to post.

 

Below 0.6 mach, you are suppose to have to pull on the stick to maintain level flight. Push, for speeds above 0.6 mach. When you approach 0.9, strange things happen. You'll go from needed 5lbs of push to 5lbs of pull at 0.9 mach. Then it change exponentially to an ever increasing push as you approach the speed of sound.

 

My source is the Haynes F-86 book, and they've copied the graph from what probably is a the pilot's flight manual.

 

Hit Quote or New Reply and scroll down to and click on Manage attachments. Browse your folders for where you saved the chart file and upload it. Alternatively copy the link to the website and paste it into yiur reply.

klem

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Not sure if this is simulated, but in the real-world, the aircraft was "trimmed" only at 0.6 mach. There's a graph of mach vs stick force (push/pull), that if I was smarter, I would know how to post.

 

Below 0.6 mach, you are suppose to have to pull on the stick to maintain level flight. Push, for speeds above 0.6 mach. When you approach 0.9, strange things happen. You'll go from needed 5lbs of push to 5lbs of pull at 0.9 mach. Then it change exponentially to an ever increasing push as you approach the speed of sound.

 

My source is the Haynes F-86 book, and they've copied the graph from what probably is a the pilot's flight manual.

 

No that graph is for aircraft trimmed FOR 0.6 mach. You could have the aircraft trimmed for 0.8 mach if you wanted

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Reading the accompanying book, I read that text to mean the aircraft is designed for level flight with neutral trim at 0.6 mach, and there are no other charts for different speeds. Feel free to ignore as desired.

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I've read a lot of threads discussing trim, and everyone seems to ignore using the throttle...

 

If you're between clicks on the trimmer, adjust the throttle a tad and you might be able to find that "sweet spot"..?

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Theres a big difference between trimming an airplane in real life and trimming one in the sim. In real life you fly the airplane to the attitude that will give you the climb descent or level flight that you want and then use the trim switch to take the pressure off the controls. Some airplanes trim very well and are stable, other require constant retrimming, if only in small amounts. In the sim you have to take a different approach which will be unrealistic by nature. My technique is to put the airplane in the nose attitude I want and then work one hat trim click at a time, slowly releasing my pressure on the controls as I do it. Click, release pressure, click, release pressure. It takes a while, but eventually the airplane will fly hands off until something changes. Note that any adjustment you make to the power, or any small bump in the air will probably cause the airplane to do something different and require it to be re-trimmed. In the sim I once I have the airplane close to trimmed out, I tend to fly using the trim, which according to someone above thats how real sabre pilots did it. I do however find the Sabre sensitive when it comes to control and trim adjustments, but with practice and focus on that aspect of airplane control you can get it figured out.

 

Sidenote: Its generally considered bad technique IRL to fly only with the trim in modern aircraft, but an allowance has to be made because of the way the trim works in the sim.

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I don't find the Sabre trim to be that sensitive. Click the hat button briefly to nudge the trim in the direction you need to. If the aircraft still won't fly level, change the power setting a tad as someone else mentioned.

 

I think the Sabre responds fairly realistically compared to a number of aircraft I have flown in the real world. Some aircraft are mushy, others are twitchy, the Sabre seems to be somewhere in between.

 

If you want to fly straight and level then trim slightly nose down and hold altitude by pulling the stick back - this is the easiest way to maintain exact altitude without having to touch the throttle.

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In view of this discussion of tailplane trim sensitivity in the sim, plus comments earlier regarding the changes in pitch trim due to flap and gear movement, I've done a bit of digging looking for RW descriptions relevant to these concerns.

 

 

The best source I've come up with to this point is RAF Pilot's Notes for the Canadair Sabre Mk 4 (F.4 in RAF terms), dated June 1953 and squirreled away on a website dedicated to RAF/GAF Station Jever, here: http://www.rafjever.org/sabrepictures.htm

 

 

Admittedly, this is not a perfect match for the F-86F-35 modeled in our sim. The Sabre Mk 4, roughly equivalent to the F-86E-10, had a less powerful version of the J47 engine and initially at least, a slatted wing. See pp. 21-22 of the DCS F-86F Flight Manual for a description of the differences between the slatted and “6-3” wing on our F-86F-35. For the most part, the Pilot's Notes on the Jever site deal with the slatted wing Sabre; Appendix I provides supplemental info for the Mk 4 updated with the slightly larger “6-3” wing.

 

 

For what it's worth, then, here are the key areas of the Mk 4 Pilot's Notes relative to tailplane trim and the response in pitch to flap and gear movement:

 

 

a. trim sensitivity – p. 46 para 58 (iv) notes all three trims are “powerful and quick in operation” and suggests tailplane trim be applied in blips to avoid over-controlling;

 

 

b. pitching moment due to flaps and gear – p.47 para 58 (vi) describes the reaction when undercarriage extends as “weak nose up initially and finally weak nose down.” Change in trim as gear retracts “slightly stronger nose up.” “Slight nose down” as flaps extend; “slight nose up” as flaps retract;

 

 

c. takeoff tailplane trim setting – p. 42 para 56 (viii) notes that the tendency to pitch nose up when flaps are raised will be reduced if the forward limit of the trim indicator light is used for the takeoff setting. For the Mk 4 with a “6-3” wing, Appendix I para II (ii) (a) goes further and suggests applying nose up trim until the indicator light just comes on, then reversing and trimming the stick one and a half to two inches forward.

 

 

Bottom line – if we're prepared to accept these comments and suggestions from the Pilot's Notes for an earlier Sabre variant as being generally applicable to the F-86F-35, tailplane trim sensitivity and strength seem to be well modeled in the sim. The response of the model to changes in flap and gear position may bear further consideration, as to strength and rate of onset. Presumably Belsimtek had something better to work with than what I've offered here – it would be good to hear from them in this regard.


Edited by blue_six
Wrong link, clarification
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In view of this discussion of tailplane trim sensitivity in the sim, plus comments earlier regarding the changes in pitch trim due to flap and gear movement, I've done a bit of digging looking for RW descriptions relevant to these concerns.

 

 

The best source I've come up with to this point is RAF Pilot's Notes for the Canadair Sabre Mk 4 (F.4 in RAF terms), dated June 1953 and squirreled away on a website dedicated to RAF/GAF Station Jever, here: http://www.rafjever.org/sabrepictures.htm

 

 

Admittedly, this is not a perfect match for the F-86F-35 modeled in our sim. The Sabre Mk 4, roughly equivalent to the F-86E-10, had a less powerful version of the J47 engine and initially at least, a slatted wing. See pp. 21-22 of the DCS F-86F Flight Manual for a description of the differences between the slatted and “6-3” wing on our F-86F-35. For the most part, the Pilot's Notes on the Jever site deal with the slatted wing Sabre; Appendix I provides supplemental info for the Mk 4 updated with the slightly larger “6-3” wing.

 

 

For what it's worth, then, here are the key areas of the Mk 4 Pilot's Notes relative to tailplane trim and the response in pitch to flap and gear movement:

 

 

a. trim sensitivity – p. 46 para 58 (iv) notes all three trims are “powerful and quick in operation” and suggests tailplane trim be applied in blips to avoid over-controlling;

 

 

b. pitching moment due to flaps and gear – p.47 para 58 (vi) describes the reaction when undercarriage extends as “weak nose up initially and finally weak nose down.” Change in trim as gear retracts “slightly stronger nose up.” “Slight nose down” as flaps extend; “slight nose up” as flaps retract;

 

 

c. takeoff tailplane trim setting – p. 42 para 56 (viii) notes that the tendency to pitch nose up when flaps are raised will be reduced if the forward limit of the trim indicator light is used for the takeoff setting. For the Mk 4 with a “6-3” wing, Appendix I para II (ii) (a) goes further and suggests applying nose up trim until the indicator light just comes on, then reversing and trimming the stick one and a half to two inches forward.

 

 

Bottom line – if we're prepared to accept these comments and suggestions from the Pilot's Notes for an earlier Sabre variant as being generally applicable to the F-86F-35, tailplane trim sensitivity and strength seem to be well modeled in the sim. The response of the model to changes in flap and gear position may bear further consideration, as to strength and rate of onset. Presumably Belsimtek had something better to work with than what I've offered here – it would be good to hear from them in this regard.

 

Thanks blue_six (and yes I owe you a PM but life.....)

 

It's hard to trim the stick 1.5" forward from the trim light when I 'hide' the stick but that's my fault. I will experiment with dabs of the trimmer - see below.

 

I have gone some way to improving the trim by programming my HOTAS to give 0.1sec blips when I operate the Hat with a 0.25 sec delay before the next blip occurs.

 

You may ask why 0.1sec? Why any specific time at all? Well, it's because we have no direct equivalent to the RL trim reaction or more to the point we have no way of equating the RL trim switch/elevator trim timing to the timing/effect of our HOTAS's. I think.

 

I will continue to tweak the timing but my gut feeling is that the vanilla trim sensitivity doesn't reflect RL because the actual 'HOTAS time operated' is not necessary the same as in RL.... Belsimtek chip in please.

klem

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