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View Full Version : Take off - flaps or elevator trim ?



Wildnoob
12-08-2008, 01:50 PM
hello folks!

I like to do all fligth procedures like real pilot's, wich of course everyone here share with the same.

but I have a doubth about wat real pilots used to adjust the elevators to get of the ground.

so my question is : flaps or elevator trim ?

I use elevator trim. they look nearly the same, but if someone could tell me witch was used in real life I would be glad.

Wildnoob
12-08-2008, 01:50 PM
hello folks!

I like to do all fligth procedures like real pilot's, wich of course everyone here share with the same.

but I have a doubth about wat real pilots used to adjust the elevators to get of the ground.

so my question is : flaps or elevator trim ?

I use elevator trim. they look nearly the same, but if someone could tell me witch was used in real life I would be glad.

Wildnoob
12-08-2008, 01:53 PM
http://www.youtube.com/watch?v=5nj77mJlzrc

this footage of a BF-109 flying in the present looks to me that the flaps where down during the take off, but I can't confirm this.

stalkervision
12-08-2008, 02:15 PM
looks like he has the flaps down and a bit of elevator trim set into the elevator stab from the angle it appears to be at. http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

Bremspropeller
12-08-2008, 02:20 PM
Depends on the plane.

Generally speaking, there is a reason why there's a "take-off" flap-setting http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

bolox00
12-08-2008, 02:38 PM
well if you want to use real life procedures a read of pilots notes is a good start, for instance-

http://www.tailwheel.nl/s/supermarinespitfireix/index.html

several more there

1 div of nose down is a bit interesting ingame tho, generally ingame i use 1/2-1 div up and 50-60% rudder trim and accept it as a limitation of the sim

Outlaw---
12-08-2008, 03:12 PM
Flaps increase the amount of lift generated by the wing. Elevator trim does not. Deploying a bit of flap for take-off can shorten the take-off run, especially when heavily laden.

--Outlaw.

WTE_Galway
12-08-2008, 03:43 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:
Depends on the plane.

Generally speaking, there is a reason why there's a "take-off" flap-setting http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif </div></BLOCKQUOTE>

absolutely

Combat flaps give a lower rotation speed (Vr) but also increase drag.

Your average GA aircraft like a Cessna will generally tell you NOT to use flaps. Probably because a light aircraft has a fair bit of trouble getting up to Vr with flaps dialed in.

On the other hand the bf109 definitely did use flaps historically. Apparently Vr without flaps on a 109 is too high for your typical rough combat airstrips and you could damage the undercarriage.


Of course undercarriage damage from overspeed is not modeled in Il2 so the takeoff flaps are optional, but if you want to be historically correct always use them on a 109.

Wildnoob
12-08-2008, 03:49 PM
thanks everybody!

this topic may look very idiot, but I was in doubth and now my doubth was solved. http://forums.ubi.com/images/smilies/25.gif

one of the arguments that let me in doubth was a P-38 trainning film that I watched (sorry, loose the link) and it was told that "normally it use not flaps".

now I know it depends.

again really thanks for your attention with someone with a so stupid doubth guys! http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

Lotharr
12-08-2008, 04:51 PM
This wasn't a stupid question http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

I even think the most of them reading this didn't know either.

It's an interesting detail.

WTE_Galway
12-08-2008, 05:12 PM
One other thing that works in game (but is probably dangerous in real life .. do not try this at home kids) is to add flaps once you have speed up.

Example:- You need to do a "bush takeoff" from somewhere that is not a runway or road.

Begin the takeoff run with no flaps so the plane will not bounce too high prematurely and then once you have speed up add flaps so the next solid bounce will see you airborne. You then just need to stay low and keep level with just rudder until you get a more acceptable speed up and climb away.

RockyAlexander
12-08-2008, 05:34 PM
Ground crews normally "preset" elevator trim for level flight at altitude. Someone please correct me if I'm wrong.

Sturm_Williger
12-08-2008, 05:59 PM
It may not be realistic, but ingame, if you're struggling to take off from a carrier with a heavily laden plane, dialing in a whack of up-elevator trim just before you leave the deck can make the difference between flight and wet feet http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif

WTE_Galway
12-08-2008, 06:04 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by RockyAlexander:
Ground crews normally "preset" elevator trim for level flight at altitude. Someone please correct me if I'm wrong. </div></BLOCKQUOTE>

Only in planes like the 109 that have no pilot adjustable trim.

In aircraft with trim, setting the elevator trim and flaps to the recommended "by the book" position for takeoff is part of your preflight.

GH_Klingstroem
12-08-2008, 06:18 PM
hang on guys!!

For take off in a real plane, you use "take off" trim and take off flaps!!!

Trim the aircraft with a fair amount of nose up trim for take off and also use take off flap if you want.
IRL u also set the rudder trim for takeoff! This is a normal procedure! Take this advice from an airline pilot!

Bremspropeller
12-08-2008, 06:42 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">For take off in a real plane, you use "take off" trim and take off flaps!!! </div></BLOCKQUOTE>

Again, it depends on the plane.

SeaFireLIV
12-08-2008, 06:59 PM
Well, I am no aeronautical engineer, but it always semed obvious to me that Take Off flaps are for taking off. However, your question isn`t stupid. I suspect that in reality TRIM is as important in some planes as well.

I find in IL2 that if I have my trim in the wrong position on take off (all the way down), even with take off flaps I`ll just stay stuck on the ground until I hit a tree!

So I guess the real answer is `both!`

mortoma
12-08-2008, 08:10 PM
In real life takeoff trim setting can be critical. Just ask me!! I once was going through my checklist for taking off in a Cessna 172 that was my favorite plane to rent. Well I must have been in a hurry and fudged when I got to "Set trim for takeoff" part of the checklist. The person who had landed her last had apparently left the trim set very nose up. This is typical to do when landing the 172 since it's a bit nose heavy.

Well, I missed that and overlooked it completely. Started down the runway after announcing my takoff over the multicom frequency. When I got to 55 knots I lifted off but the plane suddenly nosed very high and I had to quickly push the nose down to get the speed back up. I had the stall horn blaring like crazy and everything but I saved what could have been a fatal situation. I learned about flying from that!!!

TX-EcoDragon
12-08-2008, 08:43 PM
It really depends on the aircraft, but in most cases, a "normal" takeoff in a piston engine aircraft does not use flaps. There are certain aircraft designs and/or certain conditions that do warrant the use flaps. Some examples are soft field takeoffs where minimal weight on the landing gear is needed, or short field takeoffs that might not be as efficient as a no flap takeoff, but will permit a lesser forward speed relative to the vertical speed (ie a higher angle of climb at a lower rate of climb). In large, jet transport aircraft that have wing designs that are not optimized for low speed, high angle of attack operations the use of flaps as well as leading edge devices on most takeoffs are very common(not really applicable to anything in the IL-2 series).

In IL-2, things are a bit different, the amount of drag that flaps add is not terribly high relative to the lift that is added. As such the consequences to efficiency are minimal. Because of this, using "Landing Flaps" on takeoff is possible without major consequence and can help when about to roll off the end of a carrier deck with a heavilly loaded Corsair etc. If carrying a ful load of fuel, and a bomb takeoff flaps can help get wheels up sooner as well. That said, it is still going to be less efficient as far as gaining the most altitude in the least amount of time. For this reason, most IL-2 takeoffs, like most real world takeoffs in WWII aircraft will be without flaps for a "normal" takeoff. This isn't a rule - and there were warbird designs that did specify a flap setting even for normal takeoffs. In Il-2, it's not critical other than in a loaded bomber, or perhaps when rolling off the end of a carrier. . .otherwise, I don't use any flaps.

Trim is a totally different question. . .there isn't really a such thing as "using" trim since the aircraft is always trimmed for some condition. . .what the pilot does is trim for the current condition of flight. If the pilot neglects to do this, the aircraft is still trimmed for some condition just the wrong one. When trimming is done correctly the aircraft is easier to fly, and will fly more efficiently, so a pilot will generally always be trimming any time the conditions of the flight change. If the airspeed changes, if the power setting changes, or if the type of flying being done changes, then the trim will be changed too. In a PC sim, there aren't any strong stick forces to contend with, so being out of trim isn't a very big deal compared with the real thing.

In a real world aircraft there will usually be a marking on the trim wheel/knob/lever that corresponds to the takeoff trim setting, this isn't exact, but it's close enough that nothing scary or unmanageable should happen as the aircraft begins to fly. . .usually one the pilot has broken free of the ground, they will need to make a small trim adjustment to get it just right.

For this reason, I leave trim alone before takeoff when flying in IL-2 since most of the aircraft I fly have no takeoff trim position indicators, and there isn't really any consequence to being out of trim for a few seconds after takeoff that it takes for me to pitch up to the climb attitude needed, and then to trim for that speed. Also, it seems that when you spawn in the aircraft, that elevator trim is pretty close to the takeoff position anyway. If you have trim on a lever or knob, simply centering the knob or lever should be reasonably close to the takeoff setting. . . it changes based on the aircraft but usually it will take a little nose up trim than that set by a centered trim wheel, but it's not a big deal to dial it in as you establish the climb.

mortoma
12-08-2008, 08:57 PM
Takeoff trim is kind of a different thing between tail draggers and tricycles too. A totally neutral elevator trim setting should work better for a tail dragger since a slightly up trim would slightly hinder getting the tail up on the take off run. It would have a slight tendency to hold the tail down a bit. But on a tricycler like a C172 it's good to have a slight up trim for take off since the tail is already up from the start. And indeed, the takeoff trim marker for a C172 is a slightly nose high from neutral.

TX-EcoDragon
12-08-2008, 09:36 PM
Most aircraft have takeof trim marks near the point at which you see flight at Vy (best rate of climb speed) if they are trike or tailwheel. . .this wil vary with weight and balance, and also with aircraft type, but in general, that's what you get. In real world tailwheel aircraft this may very well mean I have to hold the stick back with quite a bit of force as the takeoff roll starts, and perhaps then need quite a bit of muscle to push the stick forward to lift the tail, but once near rotation speed, the stick usually starts to soften up, and the trim position as set before takeoff starts to make more sense. If you had an automated trim system, it would be nice to have full nose up trim at the start of the takeoff roll, and then some nose down trim, and then finally it would then go to the position that corresponds to the "takeoff" setting. This would be great in some designs, like the Storch which has a terribly heavy elevator at low speeds. . .

Since a sim pilot only has to fly with a joystick, and has next to no muscle needed to do whatever they want, it's really just a theoretical point here.

RockyAlexander
12-08-2008, 10:29 PM
I was watching a squadron of AI Ki-84's take off a little while ago. All aircraft adjusted trim before rolling.

idonno
12-09-2008, 01:23 AM
One point that needs to be cleared up here; elevator trim has nothing to do with how soon the airplane will get of the ground. Its only purpose is to relieve the force on the stick necessary to maintain a desired state (climbing, level, or descending flight) at a given airspeed.

You can trim the nose fully down and get off the ground just as soon as if you trimmed it fully up, you would simply have to pull back harder on the stick.

To second what others have said, whether or not to use flaps is dependent upon the airplane and the situation, but generally, a fighter, not carrying bombs, will not require flaps for takeoff from a land base.

GH_Klingstroem
12-09-2008, 03:54 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">If the pilot neglects to do this, the aircraft is still trimmed for some condition just the wrong one. </div></BLOCKQUOTE>


Haha I love this quote!!! Its great! hahaha! Very very true tho! Cant say anything about it!

GH_Klingstroem
12-09-2008, 04:01 AM
Guys another note to be added is the treim gets rid of the wobbles alot of people have when fighting. A plane that totally trimmed in this game doesnt wobble when you fire! check out my tracks
http://352ndfg.com/smf/index.php?topic=1214.0Best
and watch how stable my P51 is! There is an AVI file there called something " take off and landing "
There you can see how I trim my AC for take off and landing and how smooth the flies! Makes life easier and make hitting ur target MUCH MUCH easier! Yesterday I sat with 17% hits after 3 hours of playing and 11 kills and no deaths while flying the p51 online on Warclouds.

Freiwillige
12-09-2008, 04:29 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by WTE_Galway:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by RockyAlexander:
Ground crews normally "preset" elevator trim for level flight at altitude. Someone please correct me if I'm wrong. </div></BLOCKQUOTE>

Only in planes like the 109 that have no pilot adjustable trim.



In aircraft with trim, setting the elevator trim and flaps to the recommended "by the book" position for takeoff is part of your preflight. </div></BLOCKQUOTE>

The Bf-109 has cocpit adjustable elevator trim just not rudder or ailerons.

Swivet
12-10-2008, 12:15 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">so my question is : flaps or elevator trim ? </div></BLOCKQUOTE>

Both

K_Freddie
12-10-2008, 02:11 PM
Elevator Trim tab:- A small extra adjustable elevator (on the elevator) which helps relieve the stick pressure on the pilot, so the plane can fly itself in a certain attitude (angle) with little pilot input.

Take off Trim = ?? Does it make sense now !! http://forums.ubi.com/groupee_common/emoticons/icon_cool.gif

lesterhawksby
12-10-2008, 03:20 PM
It seems to me that, since I bought a throttle quadrant, I've been using rather *less* flap than the game's "take off" flap position on most takeoffs. I can't say I've seen an enormous improvement in takeoff quality, but I'm more comfortable with it. (Landings, on the other hand, seem much easier and smoother)

Anyway, this makes me wonder if the keyboard's "one size fits all" takeoff flap setting might not be quite the same as historical ones. Of course, it's rather hard to tell.

Trim seems to belong about in the middle on in-game takeoffs, although I'm not really sure how to tell if this is right. I can only tell if I get it very wrong. In the air is another matter.

idonno
12-10-2008, 04:35 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by lesterhawksby:
Trim seems to belong about in the middle on in-game takeoffs, although I'm not really sure how to tell if this is right. </div></BLOCKQUOTE>

It's right when the airplane neither tries to fly off the runway before it has enough airspeed, nor requires an excessive amount of back pressure on the stick to get it off the ground at the correct airspeed.

M_Gunz
12-10-2008, 11:32 PM
In IL2 the stick interface magnifies the importance of trim in ways you don't get IRL.
But then IRL you don't fly with miniature sticks except for the FBW guys.
There really is a difference so "unreal" has to apply -- it is a control interface/handling thing and not Flight Model.

If your sliders are very low at center and very high at the outside then you will experience big difference in handling
from center to where the sliders go up. It is unavoidable. IRL the 'center' is where the stick would go if you were
not holding it somewhere else -- from there everything takes force.

Question is, IRL does moving the stick takes X-pounds force per inch -- 1 pound goes so far and 10 pounds goes 10x as much?

In game you can customize your input sliders... only one way will be even like the real at all.
IMO what is right in one IL2 plane doesn't suit the rest or even most others.

lesterhawksby
12-11-2008, 06:40 AM
M_Gunz - it seems to me that in real life, once you're airborne, trim is largely instinctive. In sim, it always seems like a conscious effort to me. For takeoff, in real life I can follow the instructions - in the sim I can't tell where the trim setting even *is* when I'm on the ground, unless I use an analogue axis, and there are never enough. It seems to me that a small box with just a few decent trimwheel axes would have a reasonable market, as specialist peripherals go.

Idonno - I agree entirely, it's right when I don't crash on takeoff! But that seems like quite a large range. I bet that, if I had to feel the control forces, some of those large deflections wouldn't be much fun. I also know I'll accept wobbly takeoffs in sim which would get me the bollocking of a lifetime from a real world instructor. I probably just need more practice.

M_Gunz
12-11-2008, 06:58 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">M_Gunz - it seems to me that in real life, once you're airborne, trim is largely instinctive. In sim, it always seems like a conscious effort to me. For takeoff, in real life I can follow the instructions - in the sim I can't tell where the trim setting even *is* when I'm on the ground, unless I use an analogue axis, and there are never enough. It seems to me that a small box with just a few decent trimwheel axes would have a reasonable market, as specialist peripherals go. </div></BLOCKQUOTE>

I had such a joystick back in the early 90's. It was a basic 2-axis 2-button CH stick with trim pots built in. This was looong
before games had trim at all. It had no rudder or throttle or return spring even, cost a whole $17.

IRL it is very instinctive and accurate. In game it's a mess.

I asked for one button trim back in 2002. Stick off center, hit the trim button and it would reel in exactly that amount while
the player should ease up on the stick. Not perfect, no, but closer to real in that when to stop is no longer GUESSWORK.
I even asked for a key to stop the delayed trim action for when you've held the key too long. No dice, no change, whatever.

IRL though you get the plane trimmed, it runs a little faster so you gotta trim again but not overmuch, even IRL is not perfectly
fast and easy.

lesterhawksby
12-11-2008, 07:25 AM
Now you mention it, my ancient microsoft joystick (not ff) had something like that. Pity I lent it to someone during my long stay away from flight sims and it came back mysteriously made by Logitech and broke fifteen minutes later :-(

Currently I use a cheap stick with a little throttle on the base, and I use that throttle as an analogue elevator trim axis, since I have a better engine control in my left hand. It works OK, but there's still the speed effect you mention, and I have to go to the keyboard to sort out my rudder trim - not good. Rudder trim seems much more important in sim than in real life, but then I've never flown anything with IL-2 levels of horsepower in real life...