Spitfire trim indicator incorrect?

[ATAG_Flare]

I am under the impression that neutral trim (0%) would have the needle pointing at the middle of the dial, however when at 0% (technochat) the needle is two notches up. The middle notch is at about -29%. However it reaches 100% at both ends of the dial so something seems a bit funky...

 

[-TBC-AeroAce]

Yeah, I have wondered exactly the same thing as it seems a bit strange.

 

Also, I have not worked out what is the best trim for combat? I find to climb at best speed, you need a lot of nose up (about 30% to 40 % on the Tech chat which is the second from top notch on the dial?) but this seems to make the plane stall quite a bit in combat so I have been experimenting with lower values, this kills the stalling ness but also make it feel quite heavy. 

What do you use for combat trim?

 

Just to add requiem uses -2 notches for take off which is in the manual but I find that quite strange.

 

After looking at requiems combat vids he uses half a notch up for combat! No wonder I was stalling out at 40%. I still think it feels heavy with that setting.

Edited May 25, 2018 by AeroAce

[unreasonable]

This may be the same effect as in 109s. The technochat 0% is located at the middle of the range of travel of the actual trim tab (stab in 109 case).  But the range marked on the cockpit dials may not be calibrated to that place. In the 109,  for instance, the range is -4 to +2 (depends on which 109), so 0% technochat will show as -1 on the dial, not zero, IIRC.

 

I use a little nose down trim for take off in most planes - you do not have to force the nose down so much when the tail lifts so you are not fighting the stick during the tricky take off period. It more or less takes off by itself.   Then trim tail heavy to climb once you are clean, then about neutral for level flight. It is going to depend a lot on the feel of your stick. With FFB I like to have a little positive forwards pressure to fly level - an ROF habit.

[Talon_]

If you check out pictures of late Spits flying level they almost always have the elevator horn up above the plane of the tailplane due to trim. I've not tested it but I'd guess that Technochat gives you this value at 0%. The Spit CoG moved *a lot* during WW2 but other than the horn balances the elevators were never significantly redesigned.

 

 

 

Edited May 25, 2018 by Talon_

[sdflyer]

I believe Spitfire has elevator trim tab horizontal stabilizer. There is way anyone can determine from any photo if airplane is flying straight and level unless you take synchronized shot of external airplane attitude and  internal instrumentation indication that can tell you that.

 

In most airplane I flown including T-6  a "neutral" trim position would be equivalent to modern" take off" position. Which mean elevator or rudder trim must be set to predetermined notches/degrees  prior the take off. That is the  only time where you care about your trim position indicator. Every other phase of flight trim position is irrelevant. Pilots trim by feel. 

 

From pilot stand point of view trim is way to reduce pressure from flight controls. Therefore, we often refer to elevator trim as "to trim for speed". We do automatically without any indicators purely relying on physical sensation. 

 

Also, I wonder in which universe pilot would trim during tight turn. It doesn't make any sense at all! When you pull stick to tighten your turn  load factor increases so is airplane angle of attack. Experienced pilots receive physical feed back from the stick pressure and audio/visual cues of impending stall. This how experts ride at the edge of particular flight envelope.  If in this glorious moment of finesse  airmanship  pilot add trim (to tighten the turn)  he opt to f--- it up very quickly, loose positive control aircraft, and find himself thumbing into embarrassing  incipient spin or stall. 

 

In simulation, trim function is very limited as player only perceive visual effect of pitching up or down. Unfortunately, this is not how trim works in real life. So simmer be aware!

[Art-J]

For what it's worth, DCS Spit IX manual specifically mentions that two notches up from level on the indicator is indeed neutral tab position. Since ED guys have access to Nick Grey and Duxford Spits, I hope they knew what they were doing when implementing it that way in their Spit and now the 777 does the same - I'd guess it's correct then.

Edited May 25, 2018 by Art-J

[Guest deleted@50488]

In the bellow footage we can see that the pilot of the IX leaves the trim at the mid, or even bellow, marks, thus trimmed nose heavy, for most of he's flight, and only when deploying flaps and gear does it trim the aircraft towards neutral...

 

 

Pretty much the same observable on this 360º video:

 

 

Also very interesting to watch the use of stick & rudder during takeoff and initial climb ...

Edited May 25, 2018 by jcomm-in-combat

[Sokol1]

Rely in this "%" in "HUD" it's creating a bad habit in virtual pilots.

 

 

[eRoN]

Slightly off topic but im having some trouble trying to make sense of the spits artificial horizon. It doesn't seem to be useful at all and never in a consistent place like with the 109. You can even see on that first video by jcomm the AH is diagonal on the runway. Is it just un-caged or something? or am i retarded?

[BOO]

8 minutes ago, eRoN said:

Slightly off topic but im having some trouble trying to make sense of the spits artificial horizon. It doesn't seem to be useful at all and never in a consistent place like with the 109. You can even see on that first video by jcomm the AH is diagonal on the runway. Is it just un-caged or something? or am i retarded?

The AH isn't caged. You throw the aircraft about it upsets it. Its very sensitive to such things. The ideal instrument for a fighter! ?

 

It settles after a while until the next time you pull a stunt. But its far from useless. You just gotta make good use of your SA beyond dodging Hartman sometimes. 

[Guest deleted@50488]

For me the Vb and IX models share a common problem - contrarily to what we can see on most footage and shots of flying Spitfires, we never see the elevator deflected down, like in the shots above, when flying level … This is typical of the Spitfire, and I was never able to reproduce it in the IL2 Spitfires, at any combination of fuel and ammunition.

 

Actually it tends to require a tail heavy trimming, or the stick to be pulled, causing the elevator to become deflected up instead...

 

 

Edited May 26, 2018 by jcomm-in-combat

[Talon_]

8 hours ago, jcomm-in-combat said:

For me the Vb and IX models share a common problem - contrarily to what we can see on most footage and shots of flying Spitfires, we never see the elevator deflected down, like in the shots above, when flying level … This is typical of the Spitfire, and I was never able to reproduce it in the IL2 Spitfires, at any combination of fuel and ammunition.

 

Actually it tends to require a tail heavy trimming, or the stick to be pulled, causing the elevator to become deflected up instead...

 

 

 

I've not tested it myself, but a note is to make sure you're flying pretty slow. Modern Spitfires can't really use more than +7lbs boost thanks to their rarity, value and just the expense of high-octane avgas so don't tend to be screaming around at 300mph often.

[Guest deleted@50488]

8 hours ago, Talon_ said:

 

I've not tested it myself, but a note is to make sure you're flying pretty slow. Modern Spitfires can't really use more than +7lbs boost thanks to their rarity, value and just the expense of high-octane avgas so don't tend to be screaming around at 300mph often.

 

It's  a good hint Talon ( The T-38 ? ) but I tested over a wide range of speeds and configurations too.... I never can see that effect of the elevator deflected down when looking over my shoulders towards the tail...

 

Here's one of my preferred Spitfire footages where interesting aspects of how takeoff and landing make the tail surfaces really come alive ?

Also some ( sparse ) inflight sights of the tail and elevator, although not the best to illustrate what I meant on my post above.

 

 

 

Or here where pretty much along the whole flight the elevator will be deflected down, while in IL-2 Vb and IX it's quite the opposite, or neutral...

 

 

Edited May 27, 2018 by jcomm-in-combat

[unreasonable]

13 minutes ago, jcomm-in-combat said:

 

It's  a good hint Talon ( The T-38 ? ) but I tested over a wide range of speeds and configurations too.... I never can see that effect, even looking over my shoulders towards the tail, of the elevator deflected down …

 

I agree: whatever my speed and trim, if the elevator is tucked down at all, my nose is going down. Used outside camera to look as well. Not sure if affects flying characteristics much, but this does suggest the balance might be a little off.