Nose trim?

[Alan_A]

And since this seems to be my day for P-51 questions, another one...

What nose trim settings do you guys use on takeoff?

I ask because I just realized that there's some slightly conflicting information out there. The familiarization video recommends trim that starts at neutral (for no fuselage tank), then shifts to nose-down (down 2 degrees for an empty tank, down 4 degrees for a full tank.

The manual, on the other hand, recommends 1-3 degrees nose-up trim for an empty fuselage tank, and only slight (1-3 degree) nose-down trim for a full tank.

I realize these seem like subtle differences and maybe they are. But I've found that if I follow what the manual recommends, and trim slightly up (for fuselage tank at 25 gallons or less), she flies herself off much better than she does if I use the nose-down trim settings.

Am I on the right track? Or am I still being too ham-fisted on takeoff? Wouldn't surprise me... I love what the Mustang can do but there are times when she makes me homesick for my Spitfire...

Thanks in advance!

[Tug002]

Hey there Alan_A, I usually use about 2 or 3 degrees down trim with 25 to 40 gallons in rear tank and with full rear tank about 6 degrees down trim. I find with this trim the tail will lift first and the aircraft will not try to take off at too low of a speed. With an empty rear tank I use neutral trim. I don't know if this is the proper way of trimming the aircraft or not I just know that it works for me. I know of only one person that could give you actual numbers and that is DHenriquesA2A he is the go to man for the P-51.

Keep smiling
Tug

[DHenriques_]

And since this seems to be my day for P-51 questions, another one...

What nose trim settings do you guys use on takeoff?

I ask because I just realized that there's some slightly conflicting information out there. The familiarization video recommends trim that starts at neutral (for no fuselage tank), then shifts to nose-down (down 2 degrees for an empty tank, down 4 degrees for a full tank.

The manual, on the other hand, recommends 1-3 degrees nose-up trim for an empty fuselage tank, and only slight (1-3 degree) nose-down trim for a full tank.

I realize these seem like subtle differences and maybe they are. But I've found that if I follow what the manual recommends, and trim slightly up (for fuselage tank at 25 gallons or less), she flies herself off much better than she does if I use the nose-down trim settings.

Am I on the right track? Or am I still being too ham-fisted on takeoff? Wouldn't surprise me... I love what the Mustang can do but there are times when she makes me homesick for my Spitfire...

Thanks in advance!

Standard trim we use in the 51 community these days in the Civilian version anyway is 6-0-0. This of course reflects no fuselage tank installed and the normal modifications made within the cg envelope. With the fuselage tank installed you have an aft cg which requires a bit of nose down trim on takeoff then trimmed by feel afterward.
I've not flown a Mustang with a full fuselage tank but if I had I would carry about 5 degrees of nose down trim then edge it off after rotation as I felt what the airplane was asking me for trim wise.
DH

[Alan_A]

And it does in fact fly off better with about two degrees nose down trim with 25 gallons in the fuselage tank. But it needs to be retrimmed quickly after takeoff. I guess I'd been yanking it off the runway a bit without realizing it and then not retrimming, since it was already closer to climb trim. Always new things to learn and bad habits to break... Thanks for the guidance!

[DHenriques_]

And it does in fact fly off better with about two degrees nose down trim with 25 gallons in the fuselage tank. But it needs to be retrimmed quickly after takeoff. I guess I'd been yanking it off the runway a bit without realizing it and then not retrimming, since it was already closer to climb trim. Always new things to learn and bad habits to break... Thanks for the guidance!

The trick with trim is to use it intuitively as opposed to any preconceived notion of where it should be set.
The single caveat to this is the pre-takeoff trim settings where the trick there is to know the setting to use AS A STARTING PLACE for the trim. By starting place I mean a setting that is the recommended setting or in other words where to set trim where that setting will allow a "neutral area" for the aircraft configuration where even if the trim is off a bit it allows you over ride capability using manual controls until the airplane can be retrimmed in flight.
Considering this, you use the Dash 1, Natops, or in the Civilian case the POH recommended takeoff setting then EXPECT the aircraft to TELL YOU WHAT IT WANTS as you rotate and enter the climb.
The reason for this method and the reason I have always taught trim use this way is because the ACTUAL trim required vs the trim RECOMMENDED will always be a bit off due to variance in takeoff GW and exact cg location.
So you start with the recommended setting which is the SAFE setting in all circumstances, then adjust to what the airplane is telling you it wants once in flight. Doing that will immediately change the RECOMMENDED setting to the REQUIRED setting....and walla!........a perfectly trimmed airplane !
Dudley Henriques

[Alan_A]

Makes complete sense - had never heard it explained that way, or so clearly.

Extremely rewarding to learn all this on the P-51 since there's so much you need to feel out...

[DHenriques_]

Makes complete sense - had never heard it explained that way, or so clearly.

Extremely rewarding to learn all this on the P-51 since there's so much you need to feel out...

Sounds to me like you're doing quite well.
DH

[robert41]

I like to trim a bit nose down carrying any aft fuel. Otherwise I keep it neutral without the aft fuel.

[Alan_A]

Sounds to me like you're doing quite well.
DH

Thanks - feel like I'm getting there, slowly, with a lot of help from a certain P-51 driver and other forum friends...

Thing is, I bought all the A2A warbirds pretty much when they came out, and then avoided them for years because I was convinced I wasn't up to them. Which might have been true... but now I find myself not flying much of anything else. Nice to be challenged... nice to have a pure flight experience as opposed to a massive-checklist-management experience... and nice to have a set of fully realized, authentic airplanes that I can actually get off the ground quickly, without an hour's worth of powering up and programming FMCs...

Now, off to get that trim working right...

[Bomber_12th]

I usually don't mess with the elevator trim on takeoff - or if I do, I just usually add about 2-3 degrees nose-up trim, just to help the aircraft fly off the runway (though I never use the fuselage fuel tank). In the Kermit Weeks "Kermie Cam" video, flying his P-51C, he mentions adding just a few degrees nose-up trim for takeoff - his P-51C has all of the original military equipment/armor plate/guns/ammo in it, so it is essentially always at full combat weight - he of course never has fuel in the fuselage tank.

In this bit of original NAA video shot of a brand new P-51D-30-NA being flight tested in 1945, it actually shows the pilot dialing the elevator trim all the way up to around 10-11 degrees nose-up (obviously no fuel in the fuselage tank!).

http://www.boeingimages.com/archive/Nor ... FS546.html

[Alan_A]

Extremely interesting - I wonder if, to Dudley's point, we aren't beginning to talk about pilot preference within a safe operating range.

I just had very nice results using Dudley's recommended 6-0-0 with no fuselage tank.

On my previous few flights - when I dialed in slight nose-up trim (fuselage tank with 25 gallons), I needed to push and pull just a very little to get the tail up, then get the aircraft off the ground, but after that it sat very naturally in climb. In the same configuration with slight nose-down trim, the tail came up and the aircraft flew off with pretty much zero elevator input - but it then needed immediate attention to get the climb trim right.

Is some of this a matter of choice/style/decision about when and where to do the work of trimming? Or more generally, maybe (and I think Dudley said this in so many words) a lot comes down to feel and particular conditions once you're in the ballpark?

Related to this - are there established variations for flaps/no flaps takeoffs? My no-flaps takeoffs tend to be much smoother, as a rule.

[Alan_A]

Just had a look at the video - leaves me wondering if the nose-up trim on takeoff (radically nose up in the video) was an early practice that later was changed. Am I right that the checklists in the A2A manual (which suggest slight nose-up trim) come from WWII vintage manuals?

Related thought - and this came to mind when I was responding in the other thread and thinking about the cockpit layout... the other A2A core-Accu-Sim fighters, the Spit and the P-40, are early models that are probably pretty close to the designers' original intent. The P-51, on the other hand, is a later, much modified version, and I'm wondering if that partly explains why it's more unruly and tougher to handle. I realize that it has much more power, and that's a big part of the handling challenge. But it also had a variety of alterations - fuselage cut down, dorsal fin added, fuselage tank added - that taken together might possibly add to the difficulty. Makes me wonder what it must have been like to fly a P-51A or A-36 - whether it was a bit better harmonized than the D was. Just something else to think about while I continue to wrestle with trim and with handling in general...

[Tug002]

On long flights I use the biggest drop tanks and use them up first then I go to the aft tank then the wings. I find that the plane will almost fly itself once trimmed out with full wing and aft tanks but once you use up the drop tanks you have to make minor adjustments to trim as you use up the fuel in the aft tank as the cg moves forward. It keeps you busy switching tanks to keep level flight. I usually wait until I use up 20 or 30 gallons then switch to the other drop tank. Once they are about equal you will notice less stick pressure is needed to fly straight. This is a very interesting plane to fly on a long flight. Always something to do while flying this aircraft.

Keep smiling
Tug

[Lewis - A2A]

One way to look at it is in aerial terms the P-51, though contray, to its looks is a B'n'Z fighter. Its built to be quite unstable in order for it to get the best it can out of its limitations, that being a turn fighter. Its similar to the FW190, another famous B'n'Z fighter that was quite unstable in order to try to get the most out of its limitations so when it did get down slow it still stood a little bit of a chance against raw turn fighters. Role reversal is the classic Turn fighter such as a Spitfire during its development being powered up throughout trying to close the gap to the B'n'Z fighters of the era, such as the FW190.

Its interesting as I remember back in the EAW MSN Gaming Zone days when flying the 109e it was a nightmare trying to resist the urge to get in with the Spitfires, as B'n'Z fighting is a patient, hunters style of fighting, waiting for the time to strike with the Spitfires below trying to bait you into a slow turn fight you could rarely win.

During this time I understood Adolf Galland's tactics of baiting Spitfires and Hurricanes and getting them toward France in order to bloody new recruits to his Sqn.

thanks,
Lewis