Question about helicopter airspeed/safety margins, windshear

[Ceph]

If you're flying at an altitude of for example 3000 ft and get delayed by ATC, what would you prefer: Keep the helicopter moving at a constant speed in a holding pattern/vectored or keep the helicopter stationary/hovering? What if you are over ocean with no chance of reaching the shoreline in case of an engine failure? Does that make a difference?

I'm trying to understand the relationship between helicopter airspeed and safety margins. My impression is that keeping the helicopter moving is the prefereed option and that this has to do with rate of descent and maneuverability in case of a autorotation. On the other hand, SAR and single engine helicopters operate at low speeds and low altitudes all the time, which seems to contradict this. Is this simply due to a difference in acceptance of risk?

Furthermore I wonder how helicopters are affected by windshear. Helicopters (as far as I know) don't stall due to lack of airspeed, but I assume the airspeed gets affected similar to fixed wing aircraft. Is information about windshear important to you? If so, how does it change the way you prepare and operate?

[Non-PC Plod]

A helicopter requires more power to hover or to fly at low speed than it does and a moderate speed. Minimum power (and therefore maximum endurance) speed is typically 60-80 knots, depending on the helicopter. If you are loitering over the ocean, away from the shore, its not a good plan in a single-engined helicopter, not really a problem with a twin.
SAR helicopters operate often at low speeds, but the crew should have carried out performance calculations, so they will know what power/airspeed they can achieve given the weight of the helicopter and the met conditions on the day, and can mitigate the risk.
Flying low and slow in a SE helicopter will reflect the operator's attitude to risk - there is little opportunity to mitigate the risks.
Windshear can be a problem, but in a different way from fixed wing. It comes down to the margin of power available to apply if the helicopter is caught in a downburst or suchlike. Generally, helicopter dont like to fly close to thunderstorms, which are the main source of windshear.
Hope this helps your understanding!

[Jhieminga]

Perhaps this helps: Consider that to stay in the air, a helicopter needs air to be moving (local air speed) over its lifting surfaces just like a fixed wing aircraft. When in a hover, all this local air speed is produced by putting power into the rotor disc from the engine. When in forward flight, only a part of this local air speed is produced by the engine, the rest is due to your forward movement relative to the air. (With apologies to the field of helicopter aerodynamics, as I'm sure it could have been explained a lot better than I have done. The complete picture is obviously a lot more complicated).

[Ascend Charlie]

Furthermore I wonder how helicopters are affected by windshear. Helicopters (as far as I know) don't stall due to lack of airspeed, but I assume the airspeed gets affected similar to fixed wing aircraft. Is information about windshear important to you? If so, how does it change the way you prepare and operate?

Windshear is most important in the landing phase - an aeroplane suffering a loss of 15 or 20 knots can be in a very uncomfortable situation on final.

A helicopter is not as badly off, but it is still a serious consideration. If power is a problem, and the pilot is sucking up a lot of power at 30 kt (say, 10 kt groundspeed and 20 kt headwind) and hoping to be in ground effect before running out of power, he can be very embarrassed if the airspeed suddenly drops to 10 kt. Big suck on the power, maybe a bleed, run out of tail power, little spin, bigger splat.

[r22butters]

If you're flying at an altitude of for example 3000 ft and get delayed by ATC, what would you prefer: Keep the helicopter moving at a constant speed in a holding pattern/vectored or keep the helicopter stationary/hovering? What if you are over ocean with no chance of reaching the shoreline in case of an engine failure? Does that make a difference?

I'm trying to understand the relationship between helicopter airspeed and safety margins. My impression is that keeping the helicopter moving is the prefereed option and that this has to do with rate of descent and maneuverability in case of a autorotation. On the other hand, SAR and single engine helicopters operate at low speeds and low altitudes all the time, which seems to contradict this. Is this simply due to a difference in acceptance of risk?

Furthermore I wonder how helicopters are affected by windshear. Helicopters (as far as I know) don't stall due to lack of airspeed, but I assume the airspeed gets affected similar to fixed wing aircraft. Is information about windshear important to you? If so, how does it change the way you prepare and operate?

Flying in rather busy airspace myself I have found that most times just slowing down has given me enough time to get permission from ATC, but I have pulled it into a hover a few times while waiting at an airspace border. Even at a thousand feet though (which is where I normaly am) there's plenty of room to recover airspeed in an auto, so as long as you put yourself over a favorable site, pulling into a hover is fine.

I fly over water all the time too, and would probably keep moving enough so I could reach the edge of the shoreline, however there are places where I would chose to ditch in the water, like when the land below me is full of people, traffic, or wires. Then again my greatest fear with regards to an engine failure is that I'll come out ok, but someone else will either die or be seriously injured due to where I chose to crash. As a result I fly along the shore/coast line quite often and would go for the water as my first choice in an engine failure.

As for windshear, there were a few times when SFO was reporting it so instead of flying straight up the peninsula (and thus right over SFO) I would go the long way around to the city, so as to not fly drectly through it.

,...still got my ass knocked around pretty good though!

[Ceph]

Thanks guys for your helpful answers! It makes more sense for me now.