Question for helicopter drivers!
Discussion
Is hovering at a set spot hard to do? I always wonder why police helicopters never hover over the target, but always fly in wide circles. It defeats to whole point of using the helicopter as a slow-ass BN-2T or P.68 Observer can fly slowly in tight circles too, have infinitely more endurance for staying on station if required, much quieter and cheaper to buy and operate than a heli.
Hovering takes more energy, so uses more fuel and is noisier.
Once a helicopter transitions into forward flight, the fin can take some of the torque reaction load off the tail rotor, so there is less energy being lost there as well. Typically the tail rotor takes about 3 to 6% of the power in the hover (quoted figures vary considerably).
In Chickenhawk, Robert Mason described rescuing a platoon of soldiers from a minefield in Vietnam in a very overloaded Huey. He let the torque start to spin the helicopter which in turn gave more power to the main rotor. As the helicopter corkscrewed into the air he transitioned into forward flight, thus needing less power for the main rotor. The fin started to provide some torque reaction and he had power available for the tail rotor to stop the fuselage rotation.
A fixed wing aircraft would need to either be offset much further from the quarry, or fly in a tightly banked turn to maintain position. The latter runs the risk of parts of aircraft getting in the way of the electro-optic/infrared ball camera, not to mention being pretty sick-making for the crew plus being hazardous, flying near the stall, as the Police found when they first used the Edgley Optica.
Once a helicopter transitions into forward flight, the fin can take some of the torque reaction load off the tail rotor, so there is less energy being lost there as well. Typically the tail rotor takes about 3 to 6% of the power in the hover (quoted figures vary considerably).
In Chickenhawk, Robert Mason described rescuing a platoon of soldiers from a minefield in Vietnam in a very overloaded Huey. He let the torque start to spin the helicopter which in turn gave more power to the main rotor. As the helicopter corkscrewed into the air he transitioned into forward flight, thus needing less power for the main rotor. The fin started to provide some torque reaction and he had power available for the tail rotor to stop the fuselage rotation.
A fixed wing aircraft would need to either be offset much further from the quarry, or fly in a tightly banked turn to maintain position. The latter runs the risk of parts of aircraft getting in the way of the electro-optic/infrared ball camera, not to mention being pretty sick-making for the crew plus being hazardous, flying near the stall, as the Police found when they first used the Edgley Optica.
Edited by GliderRider on Saturday 22 March 11:50
Edited by GliderRider on Saturday 22 March 11:51
GliderRider said:
Hovering takes more energy, so uses more fuel and is noisier.
Once a helicopter transitions into forward flight, the fin can take some of the torque reaction load off the tail rotor, so there is less energy being lost there as well. Typically the tail rotor takes about 3 to 6% of the power in the hover (quoted figures vary considerably).
In Chickenhawk, Robert Mason described rescuing a platoon of soldiers from a minefield in Vietnam in a very overloaded Huey. He let the torque start to spin the helicopter which in turn gave more power to the main rotor. As the helicopter corkscrewed into the air he transitioned into forward flight, thus needing less power for the main rotor. The fin started to provide some torque reaction and he had power available for the tail rotor to stop the fuselage rotation.
That’s a very good book. Well worth a read. Once a helicopter transitions into forward flight, the fin can take some of the torque reaction load off the tail rotor, so there is less energy being lost there as well. Typically the tail rotor takes about 3 to 6% of the power in the hover (quoted figures vary considerably).
In Chickenhawk, Robert Mason described rescuing a platoon of soldiers from a minefield in Vietnam in a very overloaded Huey. He let the torque start to spin the helicopter which in turn gave more power to the main rotor. As the helicopter corkscrewed into the air he transitioned into forward flight, thus needing less power for the main rotor. The fin started to provide some torque reaction and he had power available for the tail rotor to stop the fuselage rotation.
Never a qualified helicopter pilot, I had around 25hrs in an R22 20 years ago before I had to give it up due to money. I realised I would be highly unlikely to make a living from it in the uk as there isn’t much call and an abundance of ex military people.
Now to answer your question.
One of the reasons is something called the dead man’s curve (each helicopter will have a chart telling you speeds vs altitude vs weight vs temp vs air density), this chart basically tells you where it would be impossible to recover from if you had an engine failure.
Ultimately to auto rotate in a helicopter with engine failure you trade altitude and air speed for rotor rpm which you then use in the flare near the ground to land safely.
YouTube auto rotation. But basically, in the hover near the ground you have no altitude and no airspeed to trade for rotor rpm in the even of an engine failure.
This is one of the reasons you often see helicopters gain air speed close to the ground before climbing away (along either the benefits of Effective Transitional Lift (ETL), the point where the rotor disk is no longer operating in its own dirty disturbed air resulting in more lift for the same power setting.
Is it hard to do. Depends on the helicopter, the R22 is very small, very light weight with very sensible controls. My instructor basically said if you can fly the R22 you can fly any helicopter.
I had a go in a modern twin engined helicopter simulator for a birthday present. The autopilot was quite capable of doing auto hover very well. Oh and for reference it was a lot easier to hover an R22 all be it in a simulator.
Edited by MB140 on Saturday 22 March 12:05
Tisy said:
Is hovering at a set spot hard to do? I always wonder why police helicopters never hover over the target, but always fly in wide circles. It defeats to whole point of using the helicopter as a slow-ass BN-2T or P.68 Observer can fly slowly in tight circles too, have infinitely more endurance for staying on station if required, much quieter and cheaper to buy and operate than a heli.
Hovering in a set spot hard? Nope, although on a dark night when NVGs are working hard it gets a bit trickier.They will hover at times, never is not really accurate. Flying in a wide circle is easier, uses less power and fuel. If you are in a hover and the target gets a solid object between them and the helicopter you can lose sight of them, if you are circling or moving around its harder for the target to get behind something especially at night.
If you properly need to be sneaky you just hover really high so cant be heard or seen on the ground.
In Chickenhawk, Robert Mason
Edited by GliderRider on Saturday 22 March 11:50
Edited by GliderRider on Saturday 22 March 11:51
[/quote]
This is the one of my all time favourite books. I have read it maybe 5 times. It is truly excellent. As is the follow up book he wrote which details his life after service.
Tisy said:
Is hovering at a set spot hard to do? I always wonder why police helicopters never hover over the target, but always fly in wide circles. It defeats to whole point of using the helicopter .
There may be operational reasons why the helicopter is flying in a circle not just hovering.Gnits said:
All of the above and also hovering directly above something means you can't see it, it will be directly under your backside. To observe a ground target it is generally better to orbit it.
Not quite as critical when you’ve got a gyro stabilised camera, with 360° ptz and a few other tricks up it’s sleeve…jonathan_roberts said:
This is the one of my all time favourite books. I have read it maybe 5 times. It is truly excellent. As is the follow up book he wrote which details his life after service. jonathan_roberts said:
In Chickenhawk, Robert Mason
This is the one of my all time favourite books. I have read it maybe 5 times. It is truly excellent. As is the follow up book he wrote which details his life after service.
Agreed, great book on helicopter flying in Vietnamese.This is the one of my all time favourite books. I have read it maybe 5 times. It is truly excellent. As is the follow up book he wrote which details his life after service.
What is the second book he wrote?
Mercdriver said:
jonathan_roberts said:
In Chickenhawk, Robert Mason
This is the one of my all time favourite books. I have read it maybe 5 times. It is truly excellent. As is the follow up book he wrote which details his life after service.
Agreed, great book on helicopter flying in Vietnamese.This is the one of my all time favourite books. I have read it maybe 5 times. It is truly excellent. As is the follow up book he wrote which details his life after service.
What is the second book he wrote?
Wikipedia shows that Robert Mason has written two novels, 'Weapon' and 'Solo', however I'm sure the book to which Mercdriver is referring, is 'Chickenhawk: Back in the World: Life After Vietnam'.
Robert Mason also wrote the introduction for his wife Patience's book, 'Recovering from the War'.
GliderRider said:
Mercdriver said:
jonathan_roberts said:
In Chickenhawk, Robert Mason
This is the one of my all time favourite books. I have read it maybe 5 times. It is truly excellent. As is the follow up book he wrote which details his life after service.
Agreed, great book on helicopter flying in Vietnamese.This is the one of my all time favourite books. I have read it maybe 5 times. It is truly excellent. As is the follow up book he wrote which details his life after service.
What is the second book he wrote?
Wikipedia shows that Robert Mason has written two novels, 'Weapon' and 'Solo', however I'm sure the book to which Mercdriver is referring, is 'Chickenhawk: Back in the World: Life After Vietnam'.
Robert Mason also wrote the introduction for his wife Patience's book, 'Recovering from the War'.
Edited by jonathan_roberts on Sunday 23 March 13:36
Edited by jonathan_roberts on Sunday 23 March 13:37
Heli pilot here
Uses a lot of power to hover so burns more fuel, much easier to orbit and the camera operator will have eyes on the targets anyway!
Also no it’s not hard to hover in a set spot when into wind! Out of wind is quite challenging however and out of wind trying to hover and do a slope landing isn’t fun either
Uses a lot of power to hover so burns more fuel, much easier to orbit and the camera operator will have eyes on the targets anyway!
Also no it’s not hard to hover in a set spot when into wind! Out of wind is quite challenging however and out of wind trying to hover and do a slope landing isn’t fun either
TR4man said:
Helicopter Drivers?
Aren’t they known as “pilots”?
Lorryists, Golfists etc Aren’t they known as “pilots”?
When I learnt to fly, I likened hovering to trying to stand on top of a water fountain spout. It starts off a bit wobbly, but you sense the sweet spot, from there on it's quite easy. Of course, you can fall off the sweet spot quite easily.
I recall this question being addressed in a 'Police Stop' type program (yes it was a while ago), and the below extract is the closest to the answer they gave outside of the aircraft operation requirements:
But, and as stated above, the actual target area is constantly under direct surveillance allowing them to pick up the runner(s) to direct ground forces to intercept.
ETA
Just to show this in action, the following is currently not too far away from me. You can see the large orbits of the general area, they've then made the 'I running away now' move to the north, before returning and then going into a very tight orbit on a discrete area.
ghost83 said:
Heli pilot here
..... and the camera operator will have eyes on the targets anyway! ......
The explanation given, is that people tend to try and hide when the helicopter is in close proximity. By flying an orbit, or even occasionally actually flying away and returning fast, the theory is that those they are looking for will break cover thinking they are safe...... and the camera operator will have eyes on the targets anyway! ......
But, and as stated above, the actual target area is constantly under direct surveillance allowing them to pick up the runner(s) to direct ground forces to intercept.
ETA
Just to show this in action, the following is currently not too far away from me. You can see the large orbits of the general area, they've then made the 'I running away now' move to the north, before returning and then going into a very tight orbit on a discrete area.
Edited by Ledaig on Thursday 27th March 23:09
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