- #1
Jarfi
- 384
- 12
Simple question, Given a constant speed, is the thrust of a propeller linearly related to it's pitch?
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Discussion Overview
The discussion centers on the relationship between thrust and propeller pitch at constant speed, exploring whether this relationship is linear. Participants examine the implications of varying pitch on thrust and speed, and the analogy between propeller blades and wings.
Discussion Character
- Debate/contested
- Technical explanation
Main Points Raised
- Some participants assert that thrust is not linearly related to pitch, referencing extreme angles such as 0 and 90 degrees.
- One participant questions the definition of "constant speed," suggesting that in a flying plane, thrust and drag are equal and constant, implying that changing pitch affects thrust and consequently speed.
- Another participant draws a comparison between thrust from a propeller and lift from a wing, indicating that the relationship may be roughly linear over a limited range of angles.
- It is noted that many static thrust calculators do not include pitch as a variable, suggesting that pitch has limited impact in static conditions but becomes significant when the propeller is in motion.
- One participant mentions that adjustable pitch allows for greater pitch utilization as airspeed increases.
Areas of Agreement / Disagreement
Participants generally disagree on the nature of the relationship between thrust and pitch, with multiple competing views presented regarding the conditions under which this relationship may hold true.
Contextual Notes
Participants highlight the importance of defining "constant speed" and the potential limitations of static thrust calculations, indicating that the discussion may depend on specific conditions and assumptions regarding propeller operation.
- #2
rbelli1
Gold Member
- 1,092
- 446
No.
Think about the thrust at 0 and 90 degrees.
BoB
Think about the thrust at 0 and 90 degrees.
BoB
- #3
Jarfi
- 384
- 12
rbelli1 said:
What exactly is the relationship then?
- #4
CWatters
Science Advisor
Homework Helper
Gold Member
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First of all what do you mean by "constant speed"? On a plane flying at a constant speed drag and thrust are usually constant and equal to each other. If you vary the pitch and as a result you change thrust then speed will usually change.
A prop blade is essentially a wing. Thrust from a prop is roughly equivalent to lift from a wing. Perhaps take a look at graphs of lift vs angle of attack. The shape of the curve depends on the wing section. It might be reasonably linear over a narrow range of angles...
Just the first one I could google. I think it's a model aircraft wing section...
A prop blade is essentially a wing. Thrust from a prop is roughly equivalent to lift from a wing. Perhaps take a look at graphs of lift vs angle of attack. The shape of the curve depends on the wing section. It might be reasonably linear over a narrow range of angles...
Just the first one I could google. I think it's a model aircraft wing section...
- #5
rcgldr
Homework Helper
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If you search online for "static thrust calculator", most of them don't have an input parameter for pitch, stating that pitch (within reason) doesn't make much difference in a static situation, due to limitations of the induced flow in a static situation.
The pitch comes into play when the prop is moving forwards. As air speed increase, a greater amount of pitch can be used on aircraft with adjustable pitch.
The pitch comes into play when the prop is moving forwards. As air speed increase, a greater amount of pitch can be used on aircraft with adjustable pitch.
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