Creaking DoorDuring the Falklands war, both sides had Hercules…
Also during the war both sides operated Chinooks, Puma (RAF not in theatre), Lynx and Sea King…not to mention Type-42 Destroyers!
After the war the British had quite a few UH-1H, MB-339A and T-34…plus some Chinook and Puma ‘under-new-management’…
…and for a brief period, post-war, both sides ‘operated’ the Pucara!
There is of course one ex-Argentine UH-1H flying in the United Kingdom.
Creaking DoorDoes the Royal Navy not plant mines?
Of course, but in peacetime?
Has the British secret service never killed anyone?
Probably, but there is a big difference between an assassination and attempting to destroy a major warship of an enemy power during a diplomatic mission.
A timed explosive that detonates a day or two later near an ammo storage area on the vessel so that the resulting explosion is enormous and might sink the ship.
I suppose a timed device is possible but even in the unlikely event of a hand-held device sinking the warship what would have been achieved? Suspicion would surely fall on the United Kingdom, worse, the ship could only have been damaged giving the USSR evidence of an unprovoked act of war (which is exactly what it would be).
I’m sure Crabb was engaged in some clandestine operation, I believe the Government has admitted as much, but where is ‘the line draw’ with the ship in Portsmouth harbour?
This seems to have been troubling the Russian diver who claims he killed Crabb and his ‘confession’ was made during a TV documentary. Isn’t it possible that the ‘planting a mine’ story was (official) propaganda invented to ‘excuse’ this killing or to salve his conscience?
If there was a mine, where is it?
Surely physical evidence of such a hostile act would have been used by the USSR to best advantage.
Creaking DoorDoes the Royal Navy not plant mines?
Of course, but in peacetime?
Has the British secret service never killed anyone?
Probably, but there is a big difference between an assassination and attempting to destroy a major warship of an enemy power during a diplomatic mission.
A timed explosive that detonates a day or two later near an ammo storage area on the vessel so that the resulting explosion is enormous and might sink the ship.
I suppose a timed device is possible but even in the unlikely event of a hand-held device sinking the warship what would have been achieved? Suspicion would surely fall on the United Kingdom, worse, the ship could only have been damaged giving the USSR evidence of an unprovoked act of war (which is exactly what it would be).
I’m sure Crabb was engaged in some clandestine operation, I believe the Government has admitted as much, but where is ‘the line draw’ with the ship in Portsmouth harbour?
This seems to have been troubling the Russian diver who claims he killed Crabb and his ‘confession’ was made during a TV documentary. Isn’t it possible that the ‘planting a mine’ story was (official) propaganda invented to ‘excuse’ this killing or to salve his conscience?
If there was a mine, where is it?
Surely physical evidence of such a hostile act would have been used by the USSR to best advantage.
Creaking DoorNone of the issues involved addressed directly except to whine that “. . . it could happen.”
I did smirk a bit when Kate Hudson, the chairwoman of CND, suggested that hijacking a Trident submarine was a possibility. :rolleyes:
Creaking DoorWhatever happened to…..victor 45?
Creaking DoorI think the problem here is the (lack of) definition of how the conveyor belt behaves.
As I see it there are two possible scenarios:
Scenario A:
“…conveyor belt that rotates in the opposite direction to the wheels, at the exact same speed as the wheels…”
The aircraft wheels cannot move unless the aircraft moves (relative to a fixed datum)…however to start with the aircraft wheels will be turning slowly.
The conveyor will be moving in the opposite direction at the same speed as the aircraft wheels are turning but the aircraft will still move forward (relative to a fixed datum) since at low speeds the various resistances (wheel-bearing friction, rolling resistance, inertia of the wheels and air-resistance against the rotating wheels) will be insufficient to balance the thrust of the propeller pulling the aircraft forward.
The aircraft will continue to accelerate, the aircraft wheels will rotate faster, the conveyor will move faster, and eventually the aircraft will reach take-off speed (relative to the stationary air) and fly.
Even at take-off speed the conveyor will only be turning the aircraft wheels twice as fast as normal which will not be fast enough for the various resistances to prevent take-off. 😀
Scenario B:
This is closer I think to the ‘spirit’ of the question.
“…conveyor belt that moves in the opposite direction but at an identical speed to the direction and speed that the aircraft (airframe) moves from a fixed datum.”
Again in this case all the various resistances (wheel-bearing friction, rolling resistance, inertia of the wheels and air-resistance against the rotating wheels) will be kept within reasonable limits (twice the normal take-off speed for the aircraft) and so will be insufficient to balance the thrust of the propeller pulling the aircraft forward.
As a result the aircraft will continue to accelerate and eventually reach take-off speed (relative to the stationary air) and fly. 😀
So which scenario is correct? Personally, I don’t think it matters.
As far as I am concerned, either way, the aircraft will take-off pretty much as normal…and I think I can prove it. 😉
Creaking DoorI think the problem here is the (lack of) definition of how the conveyor belt behaves.
As I see it there are two possible scenarios:
Scenario A:
“…conveyor belt that rotates in the opposite direction to the wheels, at the exact same speed as the wheels…”
The aircraft wheels cannot move unless the aircraft moves (relative to a fixed datum)…however to start with the aircraft wheels will be turning slowly.
The conveyor will be moving in the opposite direction at the same speed as the aircraft wheels are turning but the aircraft will still move forward (relative to a fixed datum) since at low speeds the various resistances (wheel-bearing friction, rolling resistance, inertia of the wheels and air-resistance against the rotating wheels) will be insufficient to balance the thrust of the propeller pulling the aircraft forward.
The aircraft will continue to accelerate, the aircraft wheels will rotate faster, the conveyor will move faster, and eventually the aircraft will reach take-off speed (relative to the stationary air) and fly.
Even at take-off speed the conveyor will only be turning the aircraft wheels twice as fast as normal which will not be fast enough for the various resistances to prevent take-off. 😀
Scenario B:
This is closer I think to the ‘spirit’ of the question.
“…conveyor belt that moves in the opposite direction but at an identical speed to the direction and speed that the aircraft (airframe) moves from a fixed datum.”
Again in this case all the various resistances (wheel-bearing friction, rolling resistance, inertia of the wheels and air-resistance against the rotating wheels) will be kept within reasonable limits (twice the normal take-off speed for the aircraft) and so will be insufficient to balance the thrust of the propeller pulling the aircraft forward.
As a result the aircraft will continue to accelerate and eventually reach take-off speed (relative to the stationary air) and fly. 😀
So which scenario is correct? Personally, I don’t think it matters.
As far as I am concerned, either way, the aircraft will take-off pretty much as normal…and I think I can prove it. 😉
Creaking DoorHang on, the wheels are free to turn yes, but they are attached to the aircraft, therefore the motion (motion is an applied force) of the belt is being applied to the not just the free spinning wheels but the aircraft that they are attached to.
Motion isn’t an applied force…I’d agree that motion can apply a force…but there has to be another ‘mechanism’ to cause the force to be applied.
In this example the ‘mechanisms’ that will apply a force to the airframe as the wheels rotate will be friction in the wheel-bearings, rolling resistance of the wheels, inertia of the wheels (which I don’t think anybody has mentioned yet) and air-resistance against the (top of the) rotating wheels.
And if that sounds like a contradiction, then yes, it is… :confused:
…but I think it is important that people can’t just state that the belt ‘pulls the aircraft backwards’…the belt exerts a force on the aircraft…the question is how…and is that force strong enough to prevent the aircraft from taking-off? 🙂
…like a person standing at the back of a treadmill holding the handles of a wheelbarrow.
Yep, that’s a pretty good analogy.
Creaking DoorHang on, the wheels are free to turn yes, but they are attached to the aircraft, therefore the motion (motion is an applied force) of the belt is being applied to the not just the free spinning wheels but the aircraft that they are attached to.
Motion isn’t an applied force…I’d agree that motion can apply a force…but there has to be another ‘mechanism’ to cause the force to be applied.
In this example the ‘mechanisms’ that will apply a force to the airframe as the wheels rotate will be friction in the wheel-bearings, rolling resistance of the wheels, inertia of the wheels (which I don’t think anybody has mentioned yet) and air-resistance against the (top of the) rotating wheels.
And if that sounds like a contradiction, then yes, it is… :confused:
…but I think it is important that people can’t just state that the belt ‘pulls the aircraft backwards’…the belt exerts a force on the aircraft…the question is how…and is that force strong enough to prevent the aircraft from taking-off? 🙂
…like a person standing at the back of a treadmill holding the handles of a wheelbarrow.
Yep, that’s a pretty good analogy.
Creaking DoorThese are the ones that I can recall from memory…
…from memory!
I don’t mind being corrected…but that’s just taking the P1$$! 😀
Creaking DoorTo elaborate on the previous answer a little I believe BAE Systems (British Aerospace) intended to present the BBMF with Mosquito RR299 that was destroyed in the tragic crash at Barton on 21st July 1996.
Creaking DoorOn a different note anyone know anything about the Harrier parked up there?
Harrier GR3 serial XV752 ‘belongs’ to 2366 Squadron Air Cadets.
Creaking DoorWhy are we talking about friction?
Why am I talking about friction? See my previous post. 🙂
I think we should be talking about positive feedback loops.
Yes, that aspect of the ‘mythical’ belt bothered me too.
It would have been better if the question had said that the belt…
“moves in the opposite direction but at an identical speed to the direction and speed that the aircraft (airframe) moves from a fixed datum.”
Still, that would have made it a bit easy! 😀
Creaking DoorWhy are we talking about friction?
Why am I talking about friction? See my previous post. 🙂
I think we should be talking about positive feedback loops.
Yes, that aspect of the ‘mythical’ belt bothered me too.
It would have been better if the question had said that the belt…
“moves in the opposite direction but at an identical speed to the direction and speed that the aircraft (airframe) moves from a fixed datum.”
Still, that would have made it a bit easy! 😀
Creaking DoorThat funny I always thought that the Atmosphere was a Gas in it’s free state.
Yes, it is a gas…but when dealing with moving air (or things moving through it) it is referred to as a fluid…sorry, poor attempt at a joke…hence the smiley face. 😮
If it were true what you are saying about bearings then they would last forever, which is just laughable, i’ll say it again the more friction on a bearing [speed] the hotter it gets…
The point I was making (or trying to make) about friction is that when most people talk about ‘friction’ they are actually talking about two distinct, related but separate effects.
Friction that resists relative movement of objects in contact with each other; this is a force (a vector) and does not increase as the relative speed of the objects increase.
Heat that is generated as a result of relative movement of objects in contact with each other; this heat (a scalar) does increase as the relative speed of the objects increase.
When I said…
The fact that the conveyor will be spinning the wheels faster than during a normal take-off will not affect these forces…as they are forces of friction and these forces do not increase as the speed of the wheel increases.
…I was only referring to the friction force not increasing with speed.
Since this force, derived from the friction in the bearings, is the only force that could possibly prevent the aircraft from moving it is important to show that it will be less than the thrust produced by the propeller irrespective of how fast the belt goes.
Yes, the faster the belt goes the more heat will be generated in the wheel-bearings…
…but the force will remain constant and will be identical to the force, derived from the friction in the wheel-bearings, if the belt was stationary.
So if the plane can take-off from a stationary belt it can take-off from a moving belt…the only difference being the temperature of the wheel-bearings. 🙂
Sign In
