Hello everyone,
This is a very interesting topic, is a pusher airplane better over a normal airplane with a front propeller?? please give your views, ideas & your experience. My personal experience says a normal conventional airplane is better over a pusher. I had few people debate on this subject so thought to discuss it here.
Thanks,
Sharlock
I find a pusher better... have been flying both ... pushers seem to be more stable...
What about responsiveness ?
The thrust from props in a push plane does not passes over most of the Control surfaces, esp Ailerons. As a result, the plane would not respond at slower ground speed. While in a typical Puller model (where the the motor is at the nose) all the control surfaces benefit from Prop wake which they can translate into Roll, Pitch and Yaw.
What benefit you have with a pusher ? belly landing friendly and also much forgiving in nose in landings.
For me pushers are better than tractors. Only thing i dont like abut pushers is they are loud, mostly because of a small prop running at high RPM.
Aerodynamically, pushers are more efficient than tractors!
Sharlock,
Did you know this topic is a very interesting topic ? pusher essentially came in because, during World War 1, interrupter gear (Later invented by Mr Fokker) wasn't invented and to shot in front you had to have the prop behind. (Mr Rolland Garos, man who scored the first aerial victory shot though the prop, sometimes the bullets shot the prop and you had to land wherever you shot your own prop). However, pusher has following disadvantages.
1. High drag
2. a lot of prop is masked due to fuse, so the engine had to swing a bigger prop
3. therefore speed penalty (limited by the tip speed of the prop)
4. pushers with the advent of interrupter gear eventually gave way to tractors
Dh2 Fe 2B are some of the well known pushers
mick mannock, billy barker red baron guynemer , all such aces went from pushers to tractors for obvious speed and maneuverability
Well, the only reason why i prefer pushers to tractors, mainly because of my flying skills, is that if it so happens(as it has, on numerous occasions) that i crash my plane nose-first into the ground, the prop and motor shaft are saved.
like i said a normal airplane is better than a pusher.. if pusher plane had any advantage you would have maximum pusher airplane today including big passenger planes... manufacturers who had come up with pusher design including Cessna have stopped the production except few homebuilt pusher plane kits that few companies sell.
It depends upon your skill. for a beginner, pusher is better. it saves ur prop and motor shaft, but the choices are different. Generally in puller aircraft, motor shaft and prop goes off due to several crashes in the beginning and the situation becomes so awkward. It takes too much time to make the shaft proper when the nose directly hit the ground.
But in pusher u'll get this opportunity to save ur motor and prop.
QuoteThe thrust from props in a push plane does not passes over most of the Control surfaces, esp Ailerons. As a result, the plane would not respond at slower ground speed. While in a typical Puller model (where the the motor is at the nose) all the control surfaces benefit from Prop wake which they can translate into Roll, Pitch and Yaw.
About responsiveness i think Ujjwaana sir has explained in better way.
Regards,
Avishek.
I was asking this question regarding the overall performance of the airplane at a expert level. I understand from a beginners point of view they can save motor & prop.. when it comes to high performance prop planes, a pusher fails in comparison to the normal conventional airplane. The answer is simple is pusher prop planes were that good you would have seen all pusher prop airplanes around.
I was debating with some of my senior people that pusher is no good... ;D
Quote from: sharlock on February 11, 2011, 06:22:07 PM
The answer is simple is pusher prop planes were that good you would have seen all pusher prop airplanes around.
Well all fighter planes are pushers ;D oh sorry you were talking about pusher prop airplanes :P
On a serious note, I've read somewhere that pushers are not preferred for manned crafts mainly because they pose serious dangers to the occupants in case of a crash; but they flourishing in the UAV's industry.
[Admin Note] Unwanted "Quote" removed... use "Reply" instead... See usage guidelines : http://www.rcindia.org/rc-india-forum/forum-usage-tips/
For UAV's a pusher configuration is preferred mostly because all engines seem to leak oil and make a mess.... and they shake a lot.. so you wanna have the engine away from the cameras and other sensors...
Look at the Predator Series of UAV's and you can see we typically have a long nose to get CG... often.. longer Landing Gear are also required....
Were it not for the sensor contamination and vibration issues.... a normal plane is almost always better from a system point of view.
All the Micro lite planes I had seen so far are all Pusher Prop ones.
yeah, mostly yester years ones, the latest are mostly tractors. Capt. Vibhooti Singh, Jaipur is marketing Microlights in India.(http://www.microlight.in/) Swift, Vampire to name a few. Pusher is Draggy, stable though. i wonder how funjet will perform if it was a tractor. Me flying a pusher (See Image)
Assuming that i have only Rx Tx setup, which of the following is best suited for learning...
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=16808
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=11439
both products including electronics cost almost equivalent..
Admin note: i had been searching for "pusher vs draggers" kind of thread, but could not find it.Please merge the topic if you find it.
Moderator note: Merged with existing thread.
Abhay,
Pusher and tractor behaves quite differently, aerodynamically and in the flying feel sense, to proceed further in life with better aeroplanes, it is always advisable to go in for a tractor config than a pusher, however a few nose overs, nose impact your motor/prop will get damaged in a tractor, however in a pusher, just glue the nose back and you are on your way again.
final verdict
Tractor
thanks gusty sir,..
A pusher configuration also has the advantage of a cleaner , neater nose , hence improving the aerodynamics , reducing drag .
As far as the size of the prop that can be swung , it depends from plane to plane . I think maximum efficiency is from a pusher rather than tractor . (about lower speeds , the control movements can be increased)
SARAS (The only indian civilian aircraft) is a pusher aircraft
few more things as of what i have understood over the years.. need opinion from experts
Tractor has a heavy propulsion system at the front, which moves the centre of gravity forward and allows smaller tail moment that provides greater stability,the propeller works in an unperturbed free stream mode and there is sufficient airflow over the engine cooling it but the slipstream disturbs the quality of air flowing over the fuselage and wing,this turbulence raises the skin friction.
Pushers facilitates high quality airflow, landing at large AoA will damage the propeller and engine may be ripped apart, it also restricts the propeller diameter like in easy star, floater and sky surfer due to the fuselage.
Pushers have another advantage especially for gliders and trainers in electrics apart from those that have already been charted earlier...
When the plane is gliding in the air with the motor off, the prop wash does not disturb the air flow over the wings rendering it highly stable. This is one of the principle reasons why they are preferred for UAVs.
In a tractor configuration, the props are generally larger and cover considerable area in front of the wing. When the motor is not operated, the free wheeling prop introduces disturbances in the air flow over the wing and the turbulence created by the prop free wheeling also resists the forward speed of the plane as a result gliding becomes difficult. Thus, the motor has to be running using up energy for gliding performance. This is not the intention in the case of UAVs.
Respected Modellers, was testing and expirimenting with both configurations, to make a slowest flying machine, for beginners.. and i found that the pusher done most.. and i found excellent rate of control even at low speeds as the prop blows air directly to the tail surface once.. with a 360 degree thrust vector assembly, the pusher behaves like a fluffy cloud in the air.. still making some pushers for slowest flights.. still loves tractor planes well.. was also experimenting with a configuration, as prop and motor suspended below the wing.. this gave me even more stabilized flights.. for a begginner i hope the pusher is the best bet.. :salute:
While i respect your views, some if you have expressed opinions not facts
(a) Pusher config has more drag (Sahevaan , you are wrong there)
(b) Wind milling Prop disturbs the air flow, beep , Saju, that is wrong too, wind milling prop produces drag, that is why a dead prop/turbo props engine is feathered (See image)
(c) ..that is why pusher on UAV , again wrong, it is for unrestricted view (So that Prop doesn't come in the view) for the payload (EO/IR/Optical)
(d) the reason for saras being a pusher (though the thrust drag couple is still conventional) is because structural, if it was a tractor, i would have been perilously close to the wing trailing edge, the newer version of saras has gone back to pusher config
Please read this thread, a pusher config has an unconventional thrust drag couple, making it not so easy to control especially with an over powered engine.
http://www.rcindia.org/rc-general-topics/basic-aerodynamics-for-rc-flying/msg58078/#msg58078
(http://www.wwiivehicles.com/usa/aircraft/fighter/lockheed-p-38-lightning-fighter/lockheed-p-38-lightning-fighter-feathered-prop-02.png)
valuable knowledge Sir.. this will help me lots future designing.. million thanks.. :salute: :salute: :salute:
rcpilotacro
Sir
Point b.
"(b) Wind milling Prop disturbs the air flow, beep , Saju, that is wrong too, wind milling prop produces drag, that is why a dead prop/turbo props engine is feathered "
We are talking about a model plane where we do not want to feather the prop using up energy. Hence it is more practical to have a smaller diameter prop creating a lesser drag not in the way of the wings. We are talking about gliders and UAVs and not WWII aircraft designed for dogfights.
Also
"Please read this thread, a pusher config has an unconventional thrust drag couple, making it not so easy to control especially with an over powered engine."
In the earlier cited topic, you are talking about the Easy Star and an unconventional thrust drag couple. If you look at the thrust line of the Easy Star, you will notice that the moment arm of the thrust line falls very close to the CG of the plane. The motor thrust line is not parallel to the axis of the fuselage, but tipping downwards such that the thrust line passes pretty close to the CG and slightly above it. This is so as to not have appreciable thrust moment tipping the plane too nose down.. i.e calculated to prevent the plane nosing up too much because of the increased lift created by the thrust of the motor when powered on full. When one switches of the throttle in flight, immediately one sees the plane lifting up considerably.
Saju
What configuration is this, this is not a pusher but has the propeller mounted on top of the fuselage - http://www.pipistrel.si/plane/apisbee/gallery
TG,
i thing these leisure flying machines are a kind of powered gliders, where prop assembly collapses into the fuselage when u attain the desired height for gliding, for the sake of hindrance free smooth surface. this is what i can get from images.i thing it is a pusher yaar :headscratch: i may be wrong