The F-35 thread, Mk II
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The F-35 thread, Mk II
Saw this demonstrated for the first time on a documentary
Very impressive, the demonstrated level of stability and almost rock steady flight path precision on a very slow landing and extremely short roll out to a braked stop
The approach speed is so slow it brings up the obvious question though, I think it’s about a 30 knot overtake, assuming 20 knots wind over the deck that’s around 50 knots IAS
At such a low speed I don’t see how you’re generating any worthwhile, additional wing lift so what’s the point if the idea is to allow higher landing weights ?
At the moment it looks like an interesting demonstration of slow flight enabled by the aircraft’s vertical lift system
Unless they’re planning higher speed RVL’ s ?
Very impressive, the demonstrated level of stability and almost rock steady flight path precision on a very slow landing and extremely short roll out to a braked stop
The approach speed is so slow it brings up the obvious question though, I think it’s about a 30 knot overtake, assuming 20 knots wind over the deck that’s around 50 knots IAS
At such a low speed I don’t see how you’re generating any worthwhile, additional wing lift so what’s the point if the idea is to allow higher landing weights ?
At the moment it looks like an interesting demonstration of slow flight enabled by the aircraft’s vertical lift system
Unless they’re planning higher speed RVL’ s ?
If they are moving forward, does that not make it a short landing, rather than a vertical one?
If they are moving forward, does that not make it a short landing, rather than a vertical one?
Avoid imitations
I don’t know about allowing a significantly higher landing weight but the main advantages of an “RVL” on any aircraft designed for vertical landings are that the pilot has a far better view of the touchdown point and as the OP noted, the aircraft is easier to fly in the lateral sense because there are more visual cues. It may also retain some natural aerodynamic stability until touchdown.
Interesting to consider the balance of thrust vectors vertical and horizontal vs weight, lift and drag. Could you end up using higher power settings if the wing is not producing sufficient lift?
Avoid imitations
Another factor is that in a fully vertical descent, the engine may ingest hot air from its own exhaust and possibly dirt. Neither are good.
No, because the aircraft is in a constant descent. However, as the IAS decreases and aerodynamic lift reduces, power will be increased to compensate.
Another factor is that in a fully vertical descent, the engine may ingest hot air from its own exhaust and possibly dirt. Neither are good.
Another factor is that in a fully vertical descent, the engine may ingest hot air from its own exhaust and possibly dirt. Neither are good.
Constant descent is a red herring, if it is constant there is no acceleration so vertical lift vector = weight. Vertical lift vector is the sum of vertical thrust vector and vertical lift vector. As you say as speed decreases lift from wing decreases and engine thrust must compensate although the airframe drag will decrease which will require less engines thrust to overcome and may compensate. Unless the Rod in the approach is sufficient for landing then that too must be slowed by a further increase in thrust.
It is all speculation on my part, the truth is out there!
RVLs on land were done on the Harrier, they let you use shorter strips amongst other things. What the F35B brings to the game is the ability to do them on a ship reliably. An example of use is bringing back weapons in hot conditions when you don't have enough thrust for the vertical landing (It's expensive jettisoning £100K wepaons so you can land)
Whilst Dave Morgan probably did the first SBRVL in 1982, the Indians have done them in SHARs too.
Whilst Dave Morgan probably did the first SBRVL in 1982, the Indians have done them in SHARs too.
Last edited by Davef68; 6th Mar 2020 at 11:20.
An aircraft does not stand still when thrust =drag, now rotate that concept through 90°
Last edited by beardy; 6th Mar 2020 at 11:39.
So lowering the nose at a given level of thrust does not cause the IAS to increase or that to maintain a given speed whilst lowering the nose I don't need to reduce thrust?
Last time I rotated your concept and pointed the nose at the nadir my G meter seemed pegged at zero. Maybe it was broken.
Last time I rotated your concept and pointed the nose at the nadir my G meter seemed pegged at zero. Maybe it was broken.
So lowering the nose at a given level of thrust does not cause the IAS to increase or that to maintain a given speed whilst lowering the nose I don't need to reduce thrust?
Last time I rotated your concept and pointed the nose at the nadir my G meter seemed pegged at zero. Maybe it was broken.
Last time I rotated your concept and pointed the nose at the nadir my G meter seemed pegged at zero. Maybe it was broken.
When thrust =drag vectors in the horizontal plane one can have a constant speed in the horizontal plane, if you want you can express it in feet per minute.
Rotate the concept through 90°
When weight=lift vectors in the vertical plane one can have a constant speed in the vertical plane, if you want you can express it in feet per minute (rate of descent)
If you have access to O level physics notes or AP 3456 it may be worth having a look at them.
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Same as if you stand on a bathroom scale in an elevator (or, lift) travelling up or down at a constant rate, it will show the same as when you're standing on it in the bathroom.
You say (correctly) that "gravity is an acceleration," which generates a force, and if we were subject to only that force and no other, then we would therefore be accelerating. But the part you're missing is that we are also subject to other forces at the same time, such as the floor of the bathroom (or the lift of an aircraft in steady flight) pushing up on us. Because that force balances the gravitational force, the sum is zero and we do not accelerate.
My big skool stuff is in there somewhere but still need your teaching on why a constant rate of descent requires the same thrust as for level flight of how a g-meter can be used in establishing a rate of descent before you expand your teachings further. Heck, until you offered to help I thought I could set and maintain a constant RoD and speed with no thrust at all.
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My big skool stuff is in there somewhere but still need your teaching on why a constant rate of descent requires the same thrust as for level flight of how a g-meter can be used in establishing a rate of descent before you expand your teachings further. Heck, until you offered to help I thought I could set and maintain a constant RoD and speed with no thrust at all.
Avoid imitations
Beardy, So from a constant IAS in straight and level flight, please explain how you begin a descent while maintaining that same IAS?
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shy torque Take this example.
Take off and go to cruise altitude.
Trim the aircraft to cruise speed, and let go of the yoke. (Keep heading with rudder only).
Reduce power. What happens? Speed stays at the trimmed speed but you descent.
Increase power. What happens? Speed stays at trimmed speed but the aircraft climbs.
Trim sets the speed.
Power controls climb or descent.
Take off and go to cruise altitude.
Trim the aircraft to cruise speed, and let go of the yoke. (Keep heading with rudder only).
Reduce power. What happens? Speed stays at the trimmed speed but you descent.
Increase power. What happens? Speed stays at trimmed speed but the aircraft climbs.
Trim sets the speed.
Power controls climb or descent.
