Pyro, about the directional stability of the Brewster in AH.

[Karnak]

Yes, they are finally going to model the blender in the P-38s.  About time.


ack-ack

Is that where the props run away and shed the blades, thus blending the pilot?  

(I should probably think about stones and glass houses on this one though.)

[Guppy35]

Sorry, existing plane remodel.   I'm all for a Beaufighter though. 

That leaves some hope for the Beau diehards at least

[kingcobradude]

Yes, they are finally going to model the blender in the P-38s.  About time.


ack-ack

whats that?

[Wmaker]

Back on topic...

Brewster's 9' Hamilton Standard prop and the spinner weighs 262lbs together. The blade type used is 6101A-12 and the hub is 3D40-235.

Is there anyone who knows some source which lists the weight of an individual blade?

I have no idea how AH's flight model handles the prop weight and its distribution but knowing the weight of an individual blade might help in getting the distribution just right. I wasn't able to find anything regarding the weight of one blade. That blade is still rather common. It is used in T-6 Texans and DHC-2 Beavers for example.


Sources:

1.) Brewster Aeronautical Corporation Report 350:
Detail Specification for Model 239 Airplane Class VF (Pyro: brewster-350.pdf)

2.) Brewster Aeronautical Corporation Report 353:
Pilot's Handbook for Model 239 Airplane

[Pyro]

Prop unit is a moment of inertia in slugs-ft^2.  I glanced at it and it is high but I don't think that's the only thing that's going on there.

[Wmaker]

I don't think that's the only thing that's going on there.

That is my hunch aswell.

I still think there might be something going on with the vertical stab/rudder even though I do acknowledge the fact that, like you said in a pm, the moment arm between the CoG and the vertical tail area is shorter than in most AH fighters. However the total vertical tail area is quite large in relation to the plane (19.2sqft: report 350). The vert stab was enlargened quite substantially since the first prototype. Also like you said before, an uncalibrated slip indicator might be contributing to the sensation of directional unstability aswell. So overall it's most probably a combination of factors.

One thing that comes to mind is the quite high profile of the Brewster's rear fuselage. I have no certain idea about how much exactly that contributes to the directional stability or how you guys model the effects of the fuselage in terms of stability.

All in all, thank you in advance Pyro for looking into it! I hope you aren't thinking that I'm looking gift horse in the mouth as I really am grateful for the Brewster!

Anyways, take your time with your current project, this is worth the wait!

[Wmaker]

Hi Pyro,

Are there any changes to be expected on this front in the upcoming version?

[Wmaker]

Thank you so much for fixing the directional stability of the Brewster, Pyro/HTC!!

It flies a lot nicer now and is a lot better gun platform.

I noticed that the roll rate got slower at speeds below 250mph. Just a perception so far though, I haven't tested it as I didn't test it in the last version either. Probably a side product of the added stability?

Overall, it's great now! The only flight model related "issue" that I see is that the combat trim leaves it slighty tail heavy. This has nowhere as severe effect as the bug you squashed with the Me262 a while ago but is still noticeable.

Anyway, it's a lot more fun to fly now!

Thank you!

[Lusche]

Thank you so much for fixing the directional stability of the Brewster, Pyro/HTC!!

It flies a lot nicer now and is a lot better gun platform.

That's almost an understatement. Flew it first time tonight after the update and was highly impressed. While all the talk was about the new Mossie, the Brewster really made a leap forward... and a big one!  

[maddafinga]

Yeah I sure hate fighting those things.  I did before too, but they seem just a bit nastier now. 

[Pyro]

Roll shouldn't be substantially different.  The things I changed were that I found that it didn't have enough dihedral, too much prop mass, and I increased the effect of the rear fuselage on directional stability.  Had to relearn combat trim of course.

[Stoney]

Roll shouldn't be substantially different.  The things I changed were that I found that it didn't have enough dihedral, too much prop mass, and I increased the effect of the rear fuselage on directional stability.  Had to relearn combat trim of course.

Increase in dihedral should = reduction in roll rate.  How conspicuous that difference is can be debated.

[Pyro]

The structure of the sim should self correct for that.

[Wmaker]

Roll shouldn't be substantially different.  The things I changed were that I found that it didn't have enough dihedral, too much prop mass, and I increased the effect of the rear fuselage on directional stability. 

Thanks for the details Pyro, they are always interesting to hear! The dihedral didn't come to my mind but the other issues were something I was suspecting.

Had to relearn combat trim of course.

I'm not sure if I understood this correctly or not. Do you mean that you had to "teach" the combat trim function to account for the changes you made to the model? Anyways, very interesting.

Regarding the rollrate,

Considering the limited data out there when it comes to the Brewster's roll rate, I don't really have any "issues" with the roll rate. I might cross test it with the previous version just to see if I'm imagining the change. Other than that the roll rate is fine, it could well be that it was "too good" previously and that it is now more realistic, who knows...or it might not be changed at all and that it's all in my head.

Stoney,

Just for interest, Brewster's dihedral is 5,5 degrees. No idea how much Pyro had to change it.

[hitech]

I'm not sure if I understood this correctly or not. Do you mean that you had to "teach" the combat trim function to account for the changes you made to the model? Anyways, very interesting. Smiley

The combat trim table is simply filled by using the auto pilot to fly the plane at different speeds and storing the control settings at speed each increment.

HiTech