Lift due to Thrust

[Badboy]

Exactly.  My question is whether or not it the affects are large enough to consider, and if so, a method of testing them in-game.

Hi Stoney,

Just to give you an idea of the difference it makes in a maximum sustained turn, I have calculated the sustained turn rate and radius under two sets of conditions. Firstly, in order to ignore the contribution that thrust makes to lift I assume that the thrust vector points in the direction the aircraft is traveling, so that all of the thrust is available to pull the aircraft around the circle, and none of it contributes to lift. Then I calculate the sustained turn rate and radius again, only this time correctly allowing for the components of thrust. That means some of the thrust assists the turn, but that less is available to pull the aircraft around the circle. The two effects work to cancel each out. Let's run the numbers for the following fictitious aircraft.

Weight: 8000lbs
Wing Area: 200ft^2
Engine: 1600HP
Clmax: 1.4

That's not all the data needed, but it give you an idea of the aircraft configuration.

In the first case, the sustained turn rate = 20dps and the radius = 781ft

In the second case, at the maximum AoA of 15 degrees the contribution of thrust to lift is 623lbs.

In that case, the sustained turn rate = 19.9dps and the radius = 763ft

So, the sustained turn rate actually gets worse by about 0.6% and the radius improves by about 2%.

That makes sense because that 623lbs increases the G slightly which reduces the radius, but the fact that there is now less thrust pulling the aircraft around the circle reduces the sustained turn velocity, so the sustained turn rate drops slightly. But those differences are small, and I suggest not tactically significant.

Hope that helps...

Badboy

[FLS]

Thanks Badboy, good to know.   

[Stoney]

Hi Stoney,

Just to give you an idea of the difference it makes in a maximum sustained turn, I have calculated the sustained turn rate and radius under two sets of conditions. Firstly, in order to ignore the contribution that thrust makes to lift I assume that the thrust vector points in the direction the aircraft is traveling, so that all of the thrust is available to pull the aircraft around the circle, and none of it contributes to lift. Then I calculate the sustained turn rate and radius again, only this time correctly allowing for the components of thrust. That means some of the thrust assists the turn, but that less is available to pull the aircraft around the circle. The two effects work to cancel each out. Let's run the numbers for the following fictitious aircraft.

Weight: 8000lbs
Wing Area: 200ft^2
Engine: 1600HP
Clmax: 1.4

That's not all the data needed, but it give you an idea of the aircraft configuration.

In the first case, the sustained turn rate = 20dps and the radius = 781ft

In the second case, at the maximum AoA of 15 degrees the contribution of thrust to lift is 623lbs.

In that case, the sustained turn rate = 19.9dps and the radius = 763ft

So, the sustained turn rate actually gets worse by about 0.6% and the radius improves by about 2%.

That makes sense because that 623lbs increases the G slightly which reduces the radius, but the fact that there is now less thrust pulling the aircraft around the circle reduces the sustained turn velocity, so the sustained turn rate drops slightly. But those differences are small, and I suggest not tactically significant.

Hope that helps...

Badboy

Excellent, thanks BB.  I suppose its something that should be considered, but not significant for comparison, unless the rough comparison shows the two aircraft almost even.  I'll just make sure to caveat any comparison going forward with "ignoring lift due to thrust".  That'll have to accompany the "ignoring CG affects on lift" from Hitech's post in the other thread.

[cegull]

I would suggest googling 'propeller efficiency' for prop questions.  There is a lot of physics and some fluid dynamics going on at one time.

[Stoney]

I would suggest googling 'propeller efficiency' for prop questions.  There is a lot of physics and some fluid dynamics going on at one time.

Thanks, but we're discussing lift due to thrust, not thrust itself.  Propeller efficiency helps us know how much thrust is being generated.  My question is how to determine how much lift is due to thrust.

[hitech]

It is fun discussing this with you stone, it shows all effects involved when wanting precision, but for plane comparison, most can be ignored unless the planes both fall out very very close.

HiTech

[Badboy]

I'll just make sure to caveat any comparison going forward with "ignoring lift due to thrust".  That'll have to accompany the "ignoring CG affects on lift" from Hitech's post in the other thread.

Just curious, it sounds as though you are doing this research for a project of some kind?

Badboy

[Stoney]

Just curious, it sounds as though you are doing this research for a project of some kind?

Badboy

Well, my foray into serious aerodynamic studies began when I decided to start drawing up a concept Formula 1 racer for Reno.  As that progressed, it dovetailed nicely into some of the stuff I was reading on the forums.  The more I've learned about the game and aerodynamics, I find myself curious about an aspect of performance, and then start digging through my books and then testing stuff in-game to see how they compare or as a method to test certain theories I have.  Right now, I'm basically putting together a table of performance characteristics of the aircraft in-game.  For example, I'm assembling all of the aerodynamic properties of the planes--the wing spans, wing areas, aspect ratios, "e" approximations, K approximations, Clmaxs, Clis, etc.  One of the biggest reasons I got interested in the Ps, EM diagrams, and so forth was to be able, at least on paper, to do some modeling and trade studies on how to optimize my F1 design.  Luckily, I can use those same tables and formulas and apply them to the planes in the game as well.

[hitech]

Stoney wrote :Luckily, I can use those same tables and formulas and apply them to the planes in the game as well.

Wow , physics sometimes work with force and distance.

HiTech

[Kenne]

My question is how to determine how much lift is due to thrust.

isnt all lift due to thrust.
thrust producing wind, wind producing lift, lift producing flight?

[FLS]

Kenne do you read the posts or just the titles?

[Kenne]

Kenne do you read the posts or just the titles?

is that a yes or a no?

[Stoney]

No, unless you consider thrust vectoring aircraft such as the AV8 or some other jets, thrust typically makes up very little lift.  Almost all of the lift is created by the wing.