Thrust to Weight Ratios

[Mace2004]

Let me rephrase the question then: will I zoom higher by pushing to Zero G or by leaving in on 1?

In a pure vertical climb your G-meter will read zero.  The G-meter reads loads normal to the aircraft centerline.  If you're reading 1G on your G-meter in a vertical climb you are actually doing a loop.

In a pure vertical zoom you need to push (and trim) to a slightly negative AoA to counteract lift generated by the typical wing's non-symmetrical airfoil shape.  In AH, you also have to deal with CT which is automatically set based only on speed with the assumption it's trimming for level flight.  In a vertical climb, CT will actually begin to trim your nose "up" as you decelerate causing you to tend to arc over on your back unless you push/trim nose down.

[Mace2004]

This is slowly coming to me but...does that mean that:

1. Hot Air Balloons and blimps are able to "fly" because their LIFT overcomes gravity, but has no self-thrust, relying on wind/currents? (Or using small propellers/engines)

2. Rockets/Missiles have no lift, but has enough THRUST to "fly".

3. Airplanes produce both LIFT AND THRUST. Being the heaviest of them all.

Hot air balloons and blimps (and dirigibles) rise because they are lighter than the surrounding air, hence the terms "lighter-than-air" and "airship" used to describe them.  The force that causes them to rise is more accurately described as buoyancy vice "lift" (think submarines here).  Just to be clear though, blimps and dirigibles can generate lift as they move forward through the air.  The shape of the envelope acts as a wing and can be used to climb, descend, and turn without changing the overall buoyancy of the craft just as submarines do.

A rocket or missile launched vertically from the ground must have thrust greater than its weight.  A horizonally flying missile/rocket (think air-to-air or air-to-ground) does generate lift otherwise they would act just like a bullet but just hit the ground at a higher speed.  These have small control surfaces (or thrust vectoring) to control AoA and they generate most of their lift by airflow over the body of the missile itself.  This lift allows the missile to fly giving it greater range and is used to guide the missile to its target.  Even the Saturn V generated lift this way as it arced over after launch.

[FLS]

Let me rephrase the question then: will I zoom higher by pushing to Zero G or by leaving in on 1?

In a less than vertical zoom climb you'll  go higher at 1G because you'll end up in a steady state climb and the lift will add more to your energy gain than the drag will subtract. It should be easy enough for you to test different angles and note the altitude gain vs a pure vertical 0G zoom climb. If you fly at 0G at less than vertical your nose will come down early in an outside half loop.

[titanic3]

Hot air balloons and blimps (and dirigibles) rise because they are lighter than the surrounding air, hence the terms "lighter-than-air" and "airship" used to describe them.  The force that causes them to rise is more accurately described as buoyancy vice "lift" (think submarines here).  Just to be clear though, blimps and dirigibles can generate lift as they move forward through the air.  The shape of the envelope acts as a wing and can be used to climb, descend, and turn without changing the overall buoyancy of the craft just as submarines do.

A rocket or missile launched vertically from the ground must have thrust greater than its weight.  A horizonally flying missile/rocket (think air-to-air or air-to-ground) does generate lift otherwise they would act just like a bullet but just hit the ground at a higher speed.  These have small control surfaces (or thrust vectoring) to control AoA and they generate most of their lift by airflow over the body of the missile itself.  This lift allows the missile to fly giving it greater range and is used to guide the missile to its target.  Even the Saturn V generated lift this way as it arced over after launch.

Ah, thanks for the info. But then how come aircraft designers won't just built a plane based on a rocket/missile? I know they tried that with the F-104(I think?) Starfighter, but that was back during the early Cold War, why not try it again but with much lighter materials, much stronger engines, and maybe even turn it into a drone?

I remember reading somewhere that the AIM-9 could pull more Gs than a pilot ever could, so why not make a drone based on the AIM9, just bigger and able to carry its own missile.

[Mace2004]

Ah, thanks for the info. But then how come aircraft designers won't just built a plane based on a rocket/missile? I know they tried that with the F-104(I think?) Starfighter, but that was back during the early Cold War, why not try it again but with much lighter materials, much stronger engines, and maybe even turn it into a drone?

I remember reading somewhere that the AIM-9 could pull more Gs than a pilot ever could, so why not make a drone based on the AIM9, just bigger and able to carry its own missile.

To be able to use the missile body for lift you need tremendous speed which means lots of thrust which means lots of fuel or very, very short duration.  For most missiles, more than half the weight is fuel and they only burn from a matter of seconds for the AIM-9 up to a couple of minutes for the AIM-54.  Yes, they can pull 20 or 30G's but it's impractical to cruise around at Mach 3 to M5.  Also, 20 or 30G's sounds impressive but you also have to remember that with the high speed comes a large turn radius and, obviously, a manned aircraft can't pull this many G's without crushing the pilot.  They have developed super maneuverable unmanned aircraft that get closer to this kind of maneuverability but then you've got the disadvantages of an unmanned aircraft to consider.  Personally, I'd concentrate on improving the maneuverability of the missiles.  Imagine not having to point at your target, just fire the missile and let it do the turning.

You're right about the F-104, it's basically an engine with a cockpit and wings bolted on.  It was a fast interceptor, capable of Mach 2, and was a beautiful plane but it turned like crap and needed external fuel tanks for decent range and endurance.  In the end it had little advantage over more conventional designs considering its limitations and even with a modern engine and materials it would still be a dog in the turn department.

[nrshida]

In a pure vertical climb your G-meter will read zero.  The G-meter reads loads normal to the aircraft centerline.  If you're reading 1G on your G-meter in a vertical climb you are actually doing a loop.

In a pure vertical zoom you need to push (and trim) to a slightly negative AoA to counteract lift generated by the typical wing's non-symmetrical airfoil shape.  In AH, you also have to deal with CT which is automatically set based only on speed with the assumption it's trimming for level flight.  In a vertical climb, CT will actually begin to trim your nose "up" as you decelerate causing you to tend to arc over on your back unless you push/trim nose down.

This is exactly what I thought the situation was, many thanks!

But now this:

In a less than vertical zoom climb you'll  go higher at 1G because you'll end up in a steady state climb and the lift will add more to your energy gain than the drag will subtract. It should be easy enough for you to test different angles and note the altitude gain vs a pure vertical 0G zoom climb. If you fly at 0G at less than vertical your nose will come down early in an outside half loop.

Confuses me. Are you saying that instead of zooming vertically upwards at zero G, I'd gain more height if I climbed on an incline (lift vector still pointing upwards not downwards) and utilised the lift from the wings? Even with a thrust ratio of less than 1.0?

I gathered that lift induced drag cost quite a penalty at lower speeds?

Sorry to bang on about this but one can usually learn a lot from an apparent contradiction.

Thank you both 

[hitech]

In a less than vertical zoom climb you'll  go higher at 1G because you'll end up in a steady state climb and the lift will add more to your energy gain than the drag will subtract. It should be easy enough for you to test different angles and note the altitude gain vs a pure vertical 0G zoom climb. If you fly at 0G at less than vertical your nose will come down early in an outside half loop.

This is not correct.

Lift does not add to your energy in any way.

Lift simply changes the direction of flight.

Lift by definition is a force perpendicular to an objects velocity vector. Gaining energy requires and increase in altitude or an increase in speed. Any excess lift (I.E. more then needed to oppose gravity approximated by the cosine of the climb angle) will cause the airplane to change the direction of it's velocity vector but not increase it.

HiTech

The most efficient energy gain will ALWAYS happen when excess power is the greatest.

[FLS]

This is exactly what I thought the situation was, many thanks!

But now this:

Confuses me. Are you saying that instead of zooming vertically upwards at zero G, I'd gain more height if I climbed on an incline (lift vector still pointing upwards not downwards) and utilised the lift from the wings? Even with a thrust ratio of less than 1.0?

I gathered that lift induced drag cost quite a penalty at lower speeds?

Sorry to bang on about this but one can usually learn a lot from an apparent contradiction.

Thank you both  

Sorry for the confusion. Mace is correct. I wasn't disagreeing with him. My point is that when you aren't vertical you don't want 0G. In other words, be sure to be vertical and don't just use 0G for every zoom climb. Most zoom climbs are at angles less than vertical where 0G will give you a curving flight path that will reduce your altitude gain.

This is not correct.

Lift does not add to your energy in any way.

Lift simply changes the direction of flight.

Lift by definition is a force perpendicular to an objects velocity vector. Gaining energy requires and increase in altitude or an increase in speed. Any excess lift (I.E. more then needed to oppose gravity approximated by the cosine of the climb angle) will cause the airplane to change the direction of it's velocity vector but not increase it.

HiTech

The most efficient energy gain will ALWAYS happen when excess power is the greatest.

My bad I should have said altitude gain not energy gain to distinguish it from total energy. The question was how to zoom higher. You're saying that in a 60 degree zoom climb with fighter A at 0G and fighter B at 1G then fighter A will have more energy even though he's lower.  I'm not disagreeing.  

[nrshida]

The most efficient energy gain will ALWAYS happen when excess power is the greatest.

Thus the optimal sustainable climb speed is actually the speed and attitude at which excess power is the greatest, because the propeller is producing maximum thrust at this speed as well as parasitic drag and lift induced drag being at their minimum?


Sorry FLS but you are confusing me further. You are saying that it is always better for your overall energy state to climb steadily on a gradient, even though the zero G vertical zoomer gains significantly more altitude? Because I intuitively felt the vertical zoomer would have the least drag and the most thrust especially towards the top? Plus he surely took the shorter route?

[FLS]

Thus the optimal sustainable climb speed is actually the speed and attitude at which excess power is the greatest, because the propeller is producing maximum thrust at this speed as well as parasitic drag and lift induced drag being at their minimum?


Sorry FLS but you are confusing me further. You are saying that it is always better for your overall energy state to climb steadily on a gradient, even though the zero G vertical zoomer gains significantly more altitude? Because I intuitively felt the vertical zoomer would have the least drag and the most thrust especially towards the top? Plus he surely took the shorter route?

Yes that's correct, to minimize drag climb at 0G. I never said it's always better to climb on a gradient.

[Puma44]

This is not correct.

Lift does not add to your energy in any way.

Lift simply changes the direction of flight.

Lift by definition is a force perpendicular to an objects velocity vector. Gaining energy requires and increase in altitude or an increase in speed. Any excess lift (I.E. more then needed to oppose gravity approximated by the cosine of the climb angle) will cause the airplane to change the direction of it's velocity vector but not increase it.

HiTech

The most efficient energy gain will ALWAYS happen when excess power is the greatest.

....and therein is the reason to have an understanding of how to apply use of the lift vector in air to air combat maneuvering. 

[prono]

Let me rephrase the question then: will I zoom higher by pushing to Zero G or by leaving in on 1?

I think zooming with G < 1 means you are falling.     

[FLS]

I think zooming with G < 1 means you are falling.     

That's the difference between a vertical zoom climb and any other zoom climb. 

[bozon]

Yes that's correct, to minimize drag climb at 0G. I never said it's always better to climb on a gradient.

Going into 0G minimizes drag by lowering the induced drag component to zero. The parasitic drag is still there and will change with speed and the zoom/dive develops. The general rule is that going 0G minimizes the instantaneous drag and for a few brief moments allow the best rate of building energy at the current speed. The thing is that the current speed will quickly change.

Since in a very steep climb (lets approximate to vertical) the speed is unsustainable and lowers, 0G is a good approximation to the most efficient zoom. In a shallow angle, 0G will send you on a ballistic-like course and at some point speed will not decrease and even start to increase (even before reaching max trajectory hight). From around this point, adding lift (1>G>0) will keep the total drag at a minimum which is sustainable for more than a moment - one essentially transits into a steady climb at the best climb speed. So typically the quickest way to gain energy is by zooming at a steep angle and 0G and then switching to a steady climb once the best climb speed is reached.

Going into a 0G dive momentarily reduces the drag and builds up speed. This is often used in a fight when you only have a short moment available for building energy and there is no time for zooming up and slowing down to a good climbing speed, then accelerating again to maneuvering speeds. This is also a good disengaging maneuver when one is not in immediate danger. You both accelerate, waste less alt per gain in speed and burn less E when leveling vs. pushing down into a vertical dive (in 0G the angle steepens with time so eventually it will reach a vertical dive).

[Stoney]

Going into 0G minimizes drag by lowering the induced drag component to zero.

Induced drag is a component of lift.  If lift is created at 0G, you have induced drag.  However, at zero G, wing loading is zero, so the load factor does not contribute to the amount of induced drag being created.  Only way to eliminate induced drag is to fly at an attitude that reduces the effective angle-of-attack to whatever is required to create a coefficient of lift = zero.

So really, flying at zero G really just removes weight and all of its influences...