Elevator Trim B737-700

[Delphi]

Hi Folks,
resently I integrated PM in my flightdeck. Almost everythink works fine (so far I have tested yet). One problem I found ist the elevator trim. I have to set the elevation trim to +13. Otherwise I do not get the nose up of the B737-700. My question ist wether this is normal with PM. By the way, I'am using the airfieles from PM and the default B737 from FS2004.

Best regards

Ruediger

[hercules]

You should set the trim with the CDU (Extras/trim), because the indicatator in FS aircraft shows a different value.

Thomas

[Delphi]

Hello Thomas,
thanks for your response.

Question 1:
How can I enter the desired trim at the CDU? The menue you mentioned shows 0.0 and does not excepts any data input

Question 2:
Is a elevation trim setting of 13 (indicated at the PM EICAS) the usual setting for a B737 with the PM airfile?

Best regards

Ruediger

[Jan Pemöller]

Trim on real 737-300/500 is arround 4.1 for a full cabin ...
But I think PM has not the same scale.

Best regards
Jan

[hercules]

Yes thats true. The PM Trim is not as real. You have to find the correct value for your aircraft. I hop, that Enrico will improve that in near future.

Thomas

[Peter Dowson]

Yes thats true. The PM Trim is not as real. You have to find the correct value for your aircraft. I hop, that Enrico will improve that in near future.

You can set the PM scale to whatever you like, suited to each aircraft. There are facilities to do this in the aircraft TXT files you supply the CDU. Check these parameters:

TrimMin=
TrimMax=
TrimScaleMax=
TrimScaleMin=

For a 737 the scale Min is 0 and Max is 17 or so. Typical takeoff trim is about 4 I think. I assume the other Min/Max values are to A/P limits.

Check your Aircraft definitions.

Regards

Pete

[Delphi]

Thanks....

Very helpful answers

Ruediger

[eudoniga]

Hi gents,

looks like one needs to do some tweaking here ...
Because (said of aircraft performance file parameters):
a) TrimMin and TrimMax relate to the green band of the EICAS trim gauge;
b) TrimScaleMin and TrimScaleMax relate to the same reality (which - I guess - is more visual than operational);
c) Then the value from the CDU appears to be the one to be trusted.

I fly a PMDG 737-700, and the perfomance file for the CDU (Steve Reyling's, made available for d/l from PM site) has these values:
TrimMin=2.1
TrimMax=8.75
TrimScaleMax=17
TrimScaleMin=0
which look quite correct ...

Last night, though, I had my EICAS elevator trim gauge showing 8.3, whilst the CDU trim showed -0.30.
Needless to say, it's the latter which must be trusted: I couldn't get the a/c rotate and lift up with a "nominal" 8.3 on the EICAS, since it actually was a -0.30 ... and until I brought the latter towards 4.00 (and that was more than 12 on the EICAS, which is hyperbolic) I couldn't take off.

Therefore the advice I have is to calibrate the values I described (TrimScaleMin / Max) to your needs. May be a higher value for max.
This settings depends on FS and the used A/C.

More fly-and-try will tell us more ...



Ciao a tutti,
Eu

[eudoniga]

... basically in terms of observation, and with little action on my part.

Here's what I found last night.

A/C model: PMDG 737-700; A/C perf. file: Steve Reyling's (d/l from PM website). FS: good ole FS9. All PM Boeing software modules up and running.

Keep in mind the original values for the TrimScale quoted in a previous post of mine, this same thread.

Last night, just for curiosity, I had the CDU Maint TRIM page displayed, and moved the elevator trim full scale up and down: 11.50 and -11.50 were the values.

Don't ask me how and where they have been related to the FS internal axis for the trim (+16 thousand something / - 16 thousand something) ...

Then I simply transferred these values to the a/c perf. file TrimScaleMax (11.5) and TrimScaleMin (-11.5) parameters.

Result: both the EICAS trim gauge and the trim value on the EICAS controls were aligned with the "true" trim values, and the green band, though graphically narrower on the larger scale (23 total units vs. 17 of the other setup), was reflecting true values, with just a minor flaw: the scale limits - I found - cannot express decimals, so the gauge rounded my input to the next integer values (+12 and - 12); the confrontation between the TRIM value on the CDU MAINT page and the trim value shown on the EICAS reflected this small gap, one total unit spanned over the total range ... being definitely acceptable !!!

Then I could properly set my trim for takeoff, without accessing the CDU page anymore, simply by trusting what was shown on the EICAS, and this was a great relief ...

No more strange behaviors, those coming from an improperly trimmed a/c, after takeoff and when the A/P pitch mode kicks in !!!

.... phew !!!



Happy takeoffs to y'all,

Eu

[NicD]

Digging up and old thread here.. just fixing trim on mine...

So based on the advice here I set:

TrimMin=2.1
TrimMax=8.75
TrimScaleMax=11.5
TrimScaleMin=-11.5

Trim setting now looks correct on the EICAS trim gauge, but there is no green zone on the scale. Is this correct? Any further advice to improve this?

thanks