Prop twist is reversed?

Questions & Community Discussions Aircraft
1

Greets, I’ve noticed that the “prop_mod_aoa_twist_delta_deg” variable is
reversed. When increasing the twist, the tips provide more thrust. We all know
the twist that props require to provide good thrust and efficiency blah blah
blah. More twist would (should)
mean that the outer part should have less AOA and less thrust on the tips, as
that is how props are twisted. They don’t twist the other way I made some
tests here below. Here with the standard +6° of twist. Tip AoA
12.7°

1722×1085 822 KB
Here with +10° of twist.
14° of tip AoA
1728×1094 691 KB
And here with -6°
of twist. 7° AoA
1650×1087 758 KB
Im confused.
Are we supposed to use the positive (wrong) value, because when using the
negative all high speed performance goes down the drain. Looking for insight
and feedback. -Tommy

2

Following…

3

Hello @MrTommymxr and @Simbol The naming of the variable is confusing. Allow
me to explain a bit more. prop_mod_aoa_twist_delta_deg doesn’t allow you
to adjust the twist angle, it allows you to add a beta angle while keeping the
same twist. So, you will first use the prop_mod_aoa_lift_delta_deg to
define the angle at a specific position of the propeller (75% by default).
You’re defining the angle in green here:
The twist is automatically
computed from this to have the alignment shown in this drawing And then,
prop_mod_aoa_twist_delta_deg will add an additional angle, constant on the
whole length of the blade, without changing the twist. @Nocturne will have a
look at the parameter description so it’s a bit more clear. Regards, Sylvain

4

Thanks Sylvain, Yes it is hard to understand what we need to do without
becoming a full aeronautical engineer hahaha. Appreciate the effort to make
the documentation more user friendly for everyone. Best, Raul

5

Yeah, that’s kinda confusing. So the twist calculates itself automatically
depending on the radius, and prop_mod_aoa_twist_delta_deg is a linear
offset from that calculated twist. What’s the difference then from just
setting a different min and max beta? If have a min beta of 10 and
prop_mod_aoa_twist_delta_deg of 5. Do i then get 15° at the defined point
(default 0.75). If i set a min beta of 15 and twitch delta of 0?