Thumpalumpacus
Major
There's your answer then: the Vamp was a pusher.
Any worth in 'pusher' aircraft?
- Thread starter tomo pauk
- Start date
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There's your answer then: the Vamp was a pusher.
Well, strictly speaking in piston-engined prop-driven aircraft the engine is producing torque, which is translated into rotational movement of a propeller, which is producing thrust, but, yeah... Turbo props as well, for that matter. In most the hot stuff out the back is just hot stuff, no thrust value.
Generally speaking if the device that provides the thrust is behind the pilot it's a pusher. For instance a P 39 is a tractor rather than pusher since the thrust comes from the Propellor in front of the cockpit even though the engine is behind the pilot. With an engine in front of the pilot driving a Propellor behind him the airplane would be a pusher. Where powerplants are in the wings if the thrust device is in front of the engine it's a tractor while behind makes it a pusher.
A.G. Williams
Airman 1st Class
- 182
- Oct 10, 2020
As I recall, some combat aircraft with pusher engines got over the safety problem by arranging for a small explosive charge to blow the prop off.
One specific armament issue is that the layout facilitates the installation of one, really big and powerful, gun. Very good for anti-tank work.
One specific armament issue is that the layout facilitates the installation of one, really big and powerful, gun. Very good for anti-tank work.
Taking the propellor off with an explosive charge was one of the many solutions tried. The Horten brothers used a pusher configuration on some of their flying wings. At least one of them had a band brake installed on the shaft just behind and between the propellor and engine like the band brake similar to the safety brake that was used on automobiles and trucks for many years. I think it was the Hughes Aircraft company (it might have been someone else) that designed a twin boom pusher aircraft that had a hinged section of fuselage below the pilot that would open allowing the pilot to drop out the bottom while protecting him from the propellor arc during escape. The Airco DH-2 was specifically designed as a pusher to allow a forward firing machine gun to make up for the lack of a gun interrupter system but, given the power/weight ratio of those days, could not mount a more substantial armament..
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
The Do335 was equipped to jettison the rear prop in the event of a bale-out.
Yes, I read that blowing off the rear propellor was part of the sequence when the jettison seat was activated.
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Dorsal fin as well, as I remember.
A couple of other issues:
- reduced ground clearance from the propeller (or a taller undercarriage) in comparison with tractor aircraft.
- for a low drag installation, some kind of extension shaft is usually required.
wuzak
Captain
It was Vultee with the XP-54.
The solution was partly for safe egress, but also was to enable the use of a fixed canopy for the pressurised cockpit, and for cockpit entry, considering the cockpit was way off the ground.
The XP-54, as proposed, was something around the size of a Typhoon. The XP-54 as it flew was bigger and heavier than the P-38, but with less power.
wuzak
Captain
It depends on the layout. With a twin boom layout the propeller could be close to the main gear, and an extension would not be required.
For conventional designs, with a single fuselage and conventional style tail plane the extension shaft is required as much for weigh balance as for aerodynamics.
Landing gear clearance not a problem as US designing successful Tricycle landing gears. CG, most pushers up to that time designed with cockpit and nose both too close to Center of Lift (CL). I've seen actual corrections of this in aircraft where moving cockpit forward and engine rearward dramatically improved CG control and handling. Fuselage fuel Tank could be safely carried over wing as well as tanks in wing at that time. Extension shaft if needed would most likely be shorter than P39 shaft.
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Aircraft with pusher props are more stable. The P effect is almost absent, and the air flows are more stable over the aerodynamic surfaces. There are allegations that a pusher prop can vastly reduce the aerodynamic drag of the fuselage if the fuselage has a dirigible like shape with the prop at the stern end.
Pusher props need longer gear or tricycle gear. They do not tolerate debris on the landing field. Dirt fields don't work.
The prop must be at least a chord distance behind the wing to reduce propellor inefficiency and noise.
Pusher props need longer gear or tricycle gear. They do not tolerate debris on the landing field. Dirt fields don't work.
The prop must be at least a chord distance behind the wing to reduce propellor inefficiency and noise.
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thunderbird
Airman
- 74
- Jul 8, 2009
biggest problem with pushers is the rotation for takeoff and landing. Prop diameter needs to be as large as possible for prop efficiency, prop needs to avoid the ground when nose is up for takeoff and landing. Prop at the front moves away from the ground during rotation, prop at back rotates towards ground. Oleos absorbing descent and weight on landing reduces ground clearance for pusher props. Means taller, heavier landing gear, or odd fuselage geometry to raise prop position.
Second problem with pusher props is the messy air flowing into pusher props. Props work more effectively when the air hitting the prop is smooth and at a predictable angle. Pusher props have to contend with boundary layers around the body and wings, areas of reduced airflow velocity due to skin friction, and downwash and spanwise flow. The complex flowfields pusher props see reduces efficiency and introduces vibration into the engine. This wa a big problem on the starship. i know of one case though, where the pusher prop design took advantge of the boundary layer around a somewhat bluff shape, to increase the prop efficiency to close to 100%. It was not the Prescott Pusher, by the way.
These two negatives for the most part keep pusher designs as a minority of aircraft designs, though there are still new aircraft developed or in development with pusher props.
Second problem with pusher props is the messy air flowing into pusher props. Props work more effectively when the air hitting the prop is smooth and at a predictable angle. Pusher props have to contend with boundary layers around the body and wings, areas of reduced airflow velocity due to skin friction, and downwash and spanwise flow. The complex flowfields pusher props see reduces efficiency and introduces vibration into the engine. This wa a big problem on the starship. i know of one case though, where the pusher prop design took advantge of the boundary layer around a somewhat bluff shape, to increase the prop efficiency to close to 100%. It was not the Prescott Pusher, by the way.
These two negatives for the most part keep pusher designs as a minority of aircraft designs, though there are still new aircraft developed or in development with pusher props.
special ed
2nd Lieutenant
- 5,731
- May 13, 2018
Another problem occurs when ice comes off the leading edge and goes through the prop. The pilot says, "What was that?"
Good point about the airflow's effect on pushers. I remember seeing a World War I photograph, apparently from a German airfield, where a captured Airco DH-2 had the fuselage substantially modified to improve airflow to the rotary engine and propeller. I mentioned in a previous post of a modern version of the DH-2 where the engine was moved further back. This was done using a custom engine mounting framework and would have contributed to improving handling and airflow as well.
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
On Bell's YFM-1, the nacelles had a long taper with the prop's center being elevated slightly above the wing's surface.
The Airacuda is a overly complex answer to a simple question.
swampyankee
Chief Master Sergeant
- 4,031
- Jun 25, 2013
An overly complex wrong answer
Thumpalumpacus
Major
Bomber interception in the late 30s was hardly a simple problem. Bombers were relatively fast in comparison to the fighters of the day, with some clearly faster. An incoming high- or medium-altitude attack meant that they would be relatively faster still as the interceptors would be slowed by the climb.
