Sir,We are a group of students from IIT Madras we are working on a UAV project for which we feel to have your opinion regarding certain aerodynamics of the aircraft to be used:The UAV is guided a base after take off and its position is given by GPS it is suppose to take pics of places and move to predefined coordinates and has to land manual controlled.We are planing to design a highly stable model with a max. payload of 2kg ,we need certain clarifications from you regarding this issue can you please answer these questions regarding stable flight and high efficiency please also if possible please suggest your own suggestions.1.what difference does it make between a push and pull propellers?2.what difference does it make between a propeller with two blades and three blades?3.please tell about the shape of the fuselage to be used and its aerodynamic stability especially between box type and cylindrical.4.suggest the aerodynamic favours between conical and parabolic nose of aircraft.5.the types of engines that may favour the need we are looking onto whether electric or ic and their powers both for pull and push prop. and the number of engines to be used ?6.can a push prop. be mounted onto the wings has it ever happened?7.whether with the engine will the aircraft be able to take-off on a run way or shall it take off only by a catapult mechanism?8.for the wings we are using (suppose to be high winged for high stability) what are the dihedral angles we are supposed to use?9.should the elevators be front or back mounted (if so it requires a elevator)?10.what about using a biplane structure?11.should we need the flaps ?12.what about the dimensions of the ailerons we may require for high stable flight dynamics?13.what about the wing span should it be lengthy or should it have lesser span with large area like the shape of a triangle?14.what about mounting the stabilator should it be along with the fuselage or should it be attached to the wings by the studs?15.should the slabilator be placed along the plane of the wings or is there any deviations?16.should it be flat or should it have some angle?17.should the elevators be mounted along with the stabilator ?18.do we require a rudder?19.if the rudder is required what should be its position?20.please tell us about the placement of the wheels and what should be their dimensions and how does it affect the aerodynamics and its influence on the stability of flight.21.if we prefer to take off in a run way is there anything we need to take special care at?22.In the UAV systems used by army and researches(like predator and shadow) we saw that they were all using catapults to take off is there any relation between their aerodynamics and the take-off mechanisms?23.Is there any care we should take care regarding the material to be used?24.can you suggest any models that may suit our requirements?Thanking You!
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12.what about the dimensions of the ailerons we may require for high stable flight dynamics?
ailerons are usually designed to be 20% of the chord length. again, there's equations for calculating the total surface area needed, but i don't think you're looking for that type of answer. i guess someone with experience is gonna have to answer that for you :/
13.what about the wing span should it be lengthy or should it have lesser span with large area like the shape of a triangle?
larger span gives you better performance in glide and endurance. i have a feeling that this is what you are looking for. a lot of times, airplanes are limited by the runway so they cannot have a span beyond a certain size. also, structural performance has a say in this. delta wings are a whole different situation. i don't think you need one of those. if speed is an issue then you want to limit the span also. i guess it depends on your design requirements.
14.what about mounting the stabilator should it be along with the fuselage or should it be attached to the wings by the studs?
15.should the slabilator be placed along the plane of the wings or is there any deviations?
16.should it be flat or should it have some angle?
17.should the elevators be mounted along with the stabilator ?
i don't know wha that is. sorry.
18.do we require a rudder?
only if you want to yaw or fly striaght :o) yes. i believe you will always require a rudder unless you are using a split flap design or something else unconventional.
19.if the rudder is required what should be its position?
the design used by airplanes like the 747 is one of the most efficient designs so far. try to use a similar design. it's been proven to work for years.
20.please tell us about the placement of the wheels and what should be their dimensions and how does it affect the aerodynamics and its influence on the stability of flight.
21.if we prefer to take off in a run way is there anything we need to take special care at?
22.In the UAV systems used by army and researches(like predator and shadow) we saw that they were all using catapults to take off is there any relation between their aerodynamics and the take-off mechanisms?
23.Is there any care we should take care regarding the material to be used?
24.can you suggest any models that may suit our requirements?
can't answer. sorry.
hopefully i've said SOMETHING usefull. best of luck to ya!
~ nolin
p.s. if anyone sees anything i've said that's incorrect please let me know. i'm just a student, i won't actually start working on airplanes (or maybe engines) for another two months or so.
i realize this question wasn't addressed to me but i may be able to help with some things...
_
1.what difference does it make between a push and pull propellers?
pull propellers are mounted either in front of the wing or at the nose
pros: the aircraft usually takes off and lands at a positive angle of attack therefore the propeller won't hit the run way
since the motor is in the front, it moves the aircrafts CG forward (helps with stability)
cons: adds swirl to the air moving over the wings due to the fact that the propeller is rotating
push prolleres are mounted either at the back of the wing or somewhere else behind it
pros: does not influence the air moving over the wings other than to increase it's velocity
cons: may hit the runway during takeoff if there is not enough ground clearance
moves aircraft CG backwards (decreases static stability)
_
____
2.what difference does it make between a propeller with two blades and three blades?
2 Blades: needs to rotate faster to achieve same thrust
less drag
3 Blades: more thrust for a given rpm
more drag
cancels some vibration modes (i don't think this part matters at this scale though)
heavier
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___
3.please tell about the shape of the fuselage to be used and its aerodynamic stability especially between box type and cylindrical.
the fuselage shape mostly affects drag. it has some influence on the pitching and yawing characteristics but very very very little.
cylindrical is better because it reduces the drag. you want to prevent the air from separating so streamlined bodies are more beneficial
a box type fuselage is way easier to fabricate. there are ways to design the fuselage as a "lifting body" like the f-15 but i don't know how.
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___
4.suggest the aerodynamic favours between conical and parabolic nose of aircraft.
i believe conical noses are really only for supersonic flight. if you can make your project break the sound barrier make sure you get a video of it flying :o)
parabolic is better because it remains streamlined at a greater range of angles of attack. explanation: imagine a pointed nose. eventually, as the angle of attack increases (whether due to control or wind gusts) the tip is going to eventually cause separation. this is similar to why airfoils are more "parabolic".
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___
5.the types of engines that may favour the need we are looking onto whether electric or ic and their powers both for pull and push prop. and the number of engines to be used ?
really depends on weight requirements. is "ic" internal combustion? electric engines are safer. the downside is that the weight of the battery doesn't decrease as it's charge decreases whereas with a gas engine, the weight decreases since the fuel is gone.
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___
6.can a push prop. be mounted onto the wings has it ever happened?
sure why not. just make sure it'll clear the ground during takeoff and landing!!!
___
___
7.whether with the engine will the aircraft be able to take-off on a run way or shall it take off only by a catapult mechanism?
depends on the design. i don't know how to answer this question.
___
___
8.for the wings we are using (suppose to be high winged for high stability) what are the dihedral angles we are supposed to use?
there's equations to help you calculate that, but i'm not sure if you're looking for that type of answer. it's also dependent on the rest of the aircraft.
___
___
9.should the elevators be front or back mounted (if so it requires a elevator)?
if i understand your question correctly...back.
___
___
10.what about using a biplane structure?
biplanes were used due to a lack of engine power back in the day. now they're used for looks. they look sweet. you can't deny that. single wings are much more efficient.
___
___
11.should we need the flaps ?
you mean like, for takeoff? probably not. if you're runway is more or less unlimitied then you'll be ok without them. they just add to
Replies
12.what about the dimensions of the ailerons we may require for high stable flight dynamics?
ailerons are usually designed to be 20% of the chord length. again, there's equations for calculating the total surface area needed, but i don't think you're looking for that type of answer. i guess someone with experience is gonna have to answer that for you :/
13.what about the wing span should it be lengthy or should it have lesser span with large area like the shape of a triangle?
larger span gives you better performance in glide and endurance. i have a feeling that this is what you are looking for. a lot of times, airplanes are limited by the runway so they cannot have a span beyond a certain size. also, structural performance has a say in this. delta wings are a whole different situation. i don't think you need one of those. if speed is an issue then you want to limit the span also. i guess it depends on your design requirements.
14.what about mounting the stabilator should it be along with the fuselage or should it be attached to the wings by the studs?
15.should the slabilator be placed along the plane of the wings or is there any deviations?
16.should it be flat or should it have some angle?
17.should the elevators be mounted along with the stabilator ?
i don't know wha that is. sorry.
18.do we require a rudder?
only if you want to yaw or fly striaght :o) yes. i believe you will always require a rudder unless you are using a split flap design or something else unconventional.
19.if the rudder is required what should be its position?
the design used by airplanes like the 747 is one of the most efficient designs so far. try to use a similar design. it's been proven to work for years.
20.please tell us about the placement of the wheels and what should be their dimensions and how does it affect the aerodynamics and its influence on the stability of flight.
21.if we prefer to take off in a run way is there anything we need to take special care at?
22.In the UAV systems used by army and researches(like predator and shadow) we saw that they were all using catapults to take off is there any relation between their aerodynamics and the take-off mechanisms?
23.Is there any care we should take care regarding the material to be used?
24.can you suggest any models that may suit our requirements?
can't answer. sorry.
hopefully i've said SOMETHING usefull. best of luck to ya!
~ nolin
p.s. if anyone sees anything i've said that's incorrect please let me know. i'm just a student, i won't actually start working on airplanes (or maybe engines) for another two months or so.
_
1.what difference does it make between a push and pull propellers?
pull propellers are mounted either in front of the wing or at the nose
pros: the aircraft usually takes off and lands at a positive angle of attack therefore the propeller won't hit the run way
since the motor is in the front, it moves the aircrafts CG forward (helps with stability)
cons: adds swirl to the air moving over the wings due to the fact that the propeller is rotating
push prolleres are mounted either at the back of the wing or somewhere else behind it
pros: does not influence the air moving over the wings other than to increase it's velocity
cons: may hit the runway during takeoff if there is not enough ground clearance
moves aircraft CG backwards (decreases static stability)
_
____
2.what difference does it make between a propeller with two blades and three blades?
2 Blades: needs to rotate faster to achieve same thrust
less drag
3 Blades: more thrust for a given rpm
more drag
cancels some vibration modes (i don't think this part matters at this scale though)
heavier
___
___
3.please tell about the shape of the fuselage to be used and its aerodynamic stability especially between box type and cylindrical.
the fuselage shape mostly affects drag. it has some influence on the pitching and yawing characteristics but very very very little.
cylindrical is better because it reduces the drag. you want to prevent the air from separating so streamlined bodies are more beneficial
a box type fuselage is way easier to fabricate. there are ways to design the fuselage as a "lifting body" like the f-15 but i don't know how.
___
___
4.suggest the aerodynamic favours between conical and parabolic nose of aircraft.
i believe conical noses are really only for supersonic flight. if you can make your project break the sound barrier make sure you get a video of it flying :o)
parabolic is better because it remains streamlined at a greater range of angles of attack. explanation: imagine a pointed nose. eventually, as the angle of attack increases (whether due to control or wind gusts) the tip is going to eventually cause separation. this is similar to why airfoils are more "parabolic".
___
___
5.the types of engines that may favour the need we are looking onto whether electric or ic and their powers both for pull and push prop. and the number of engines to be used ?
really depends on weight requirements. is "ic" internal combustion? electric engines are safer. the downside is that the weight of the battery doesn't decrease as it's charge decreases whereas with a gas engine, the weight decreases since the fuel is gone.
___
___
6.can a push prop. be mounted onto the wings has it ever happened?
sure why not. just make sure it'll clear the ground during takeoff and landing!!!
___
___
7.whether with the engine will the aircraft be able to take-off on a run way or shall it take off only by a catapult mechanism?
depends on the design. i don't know how to answer this question.
___
___
8.for the wings we are using (suppose to be high winged for high stability) what are the dihedral angles we are supposed to use?
there's equations to help you calculate that, but i'm not sure if you're looking for that type of answer. it's also dependent on the rest of the aircraft.
___
___
9.should the elevators be front or back mounted (if so it requires a elevator)?
if i understand your question correctly...back.
___
___
10.what about using a biplane structure?
biplanes were used due to a lack of engine power back in the day. now they're used for looks. they look sweet. you can't deny that. single wings are much more efficient.
___
___
11.should we need the flaps ?
you mean like, for takeoff? probably not. if you're runway is more or less unlimitied then you'll be ok without them. they just add to