it's altitude should be whatever is economical for that flight
It differs with every machine. Large military helicopters generally have longest range and near highest speeds.
Helicopters are not very well suited to high altitude flight. By their very nature helicopters less suited for high altitudes than airplanes or balloons. Additionally, since the most common usages of helicopters deals in short hops or other low-altitude duties, modern helicopters aren't designed with high altitude flight in mind. The stratosphere is generally agreed to start at about 30,000 feet altitude. While this is pretty near to the helicopter altitude record (in 2005 an Ecureuil/AStar AS 350 B3 helicopter landed on Mount Everest (29,035 feet)) This is far higher than the ceiling of the average helicopter (10 to 12,000 feet).
An inverse relationship.
Helicopters fly somewhat close to the ground. They fly near the troposphere. They fly at a lower altitude than planes.
The air gets thinner as altitude increases, which in turn decreases the amount of lift an aircraft can get. The air in the stratosphere is far too thing for helicopters and most planes.
I believe the FAI world altitude record for a helicopter is 40820', and helicopters can now land on the top of Mount Everest, just over 29,000'. But practically speaking, helicopters rarely go over 10,000 feet as that's the altitude above which pressurized cabins and supplemental oxygen are required.
Helicopters are typically designed to fly in the troposphere, which is closer to the Earth's surface. The stratosphere begins at around 10 kilometers above sea level, and helicopters lack the necessary design and power to operate efficiently at that altitude.
Most helicopters out there do not have pressurized cabins so the general service ceiling for helicopters today is 10,000 ft. So to answer your question anywhere from 0-10,000 ft. depending on airspace regulations.
Helicopters fly at low altitude.Passenger planes climb to high altitude.Birds use low altitude height to fly from tree to housetop.Military cargo planes pass over my house at low altitude.
by altitude...you should know this
The higher you are from the Earth's surface - the lower the air pressure is. Helicopters are heavy machines - requiring a huge amount of effort from the rotor blades to keep it airborn. The lower the air-pressure, the harder the rotors have to work to keep the craft flying.
Helicopters typically fly at altitudes ranging from 1,000 to 3,000 feet for general operations, though this can vary based on the mission and location. For emergency medical services or law enforcement, they may fly lower for better visibility and access. In some cases, helicopters can reach altitudes of up to 10,000 feet, but this is less common due to reduced air density and potential altitude-related issues. Overall, operational altitude is influenced by factors like terrain, weather, and air traffic regulations.