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How High Can You Go In a Helicopter? Can You Land On Mount Everest?


Flying high in a helicopter takes some remarkable feats of design and engineering. Although helicopters cannot fly as high as their fixed-winged counterparts they can do remarkable things like rescue people off some of the world’s highest mountains!

The official altitude record for a helicopter flight is 12,954 m (42,500 ft) set by Fred North in 2002 however, most helicopter manufacturers limit their aircraft to around 20,000 – 25,000 ft for normal operation. The highest landing was on Mount Everest at 8,848 m (29,030 ft) in 2005.

So why cant a helicopter fly as high as a plane? As with everything in aviation, being able to fly high requires performance that is always a trade-off between engineering, aerodynamics, and commercial pressures.

Read on to find out some interesting stuff about what limits how high a helicopter can fly.

Helicopter Altitude Records

Highest Altitude Flight:

Fred North – March 23, 2002, in a Eurocopter AS350 B2 flew to 12,954 m (42,500FT) – Source: Fred-North.com

Highest Landing:

Didier Delsalle – May 14, 2005, in a Eurocopter AS350 B3 landed on top of Mount Everest at 8,848 m (29,030 ft) – Source: Eurocopter

Highest Worldwide Rescue:

Maurizio Folini – May 19, 2013, in a Eurocopter AS350 B3 rescued double-amputee Sudarshan Gautam on Mount Everest at 7,800 m (25,590 ft) – Source: Men’s Journal

Highest US Rescue:

Adam Hermanski – May 12, 2011, in a Eurocopter AS350 B3 rescued Jerry O’Sullivan on Alaska’s Denali (Mount McKinley) at 6,045 m (19,833 ft) – Source: Wired Magazine

As you can see the Eurocopter AS350 series helicopter is a formidable altitude smashing machine!

Didier Delsalle with his Record-Breaking Eurocopter AS350 B3 – Source: Wikipedia

Being able to break records and fly high in a helicopter requires the following barriers to be overcome:

Environmental Factors
Aerodynamic Factors

I’ll try and keep these as simple to follow so I will leave out all the complex stuff that I can!

Environmental Factors

These factors are what the aircraft uses to work with or off. Depending on the environment conditions at the time of the flight they can seriously impede how high a helicopter can fly.

The four arch enemies to helicopter performance are:

  1. Hot Air
  2. High Altitude
  3. Humid Air
  4. Heavy Aircraft – Covered Later

Lets look at these in layman’s terms:

Temperature

As the temperature of an air molecule increases, it vibrates more. Think of an elevator full of people. If everyone is standing still you can fit more people. If everyone is dancing, you can’t fit as many people.

Swap these people for molecules of air in a given space, let’s say a 1-foot cube. The hotter the temperature, the more the air molecules vibrate, thus the fewer molecules will be able to fit in that 1-foot cube.

A helicopter engine needs air (oxygen) molecules for combustion.
Fewer Air Molecules = Less Combustion = Less Power

A helicopter’s rotor blades need air molecules to work off to create lift.
Fewer Air Molecules = Less To Work Off = Less Lift

Therefore, the cooler the air, the higher a helicopter can go. A helicopter flying in Alaska at 10,000 ft will have more air molecules to work on/with than a helicopter in the tropics at 10,000 ft.

Altitude

As you go higher in the atmosphere the air pressure reduces. Less air pressure means fewer air molecules in any given space. Take the 1-foot cube again. The cube at sea level will have every air molecule above it being pulled to the surface by gravity, so the cube will be tightly packed with molecules.

That same cube at 10,000 ft will have less air molecules above it being pulled down, so fewer air molecules will be packed into the cube.

A helicopter engine needs air (oxygen) molecules for combustion.
Fewer Air Molecules = Less Combustion = Less Power.

A helicopter’s rotor blades need air molecules to work off to create lift.
Fewer Air Molecules = Less To Work Off = Less Lift.

Therefore, the higher a helicopter flies, the less air pressure, thus the fewer air molecules the engine and rotor blades have to work with/on.

Humidity

The amount of moisture contained in the air is its humidity. At 100% humidity that 1-foot cube is completely saturated with moisture and the air parcel cannot hold any more. Moisture takes up space that air molecules could occupy and it doesn’t burn in a helicopter engine!

The More Moisture In a Given Parcel of Air = The Less Combustion the Engine Will Have = The Less Power It will Produce

Therefore, the less humid the air, the higher the helicopter can go because the engine performance is better. A helicopter flying in dry Alaska at 10,000 ft will have less moisture impeding it than a helicopter in the humid tropics at 10,000 ft.

Mechanical Factors

Weight

The more the helicopter weighs, the more lift it has to generate to overcome that weight and get it airborne.

When you factor in Heat, Air Pressure and Humidity, the worse those are the harder the engine and rotor blades have to work to lift that weight.

For Example:

An AS350 B2 is at a maximum gross weight of 4961 lbs and it can only climb up to 15,000 ft.

Land and remove 2 passengers and it now weighs 4561lbs and now it can climb to 17,000 ft.

The more weight you remove, the less the engine and rotor have to work, and the higher you can go before one of them reaches its limit.

Most high-altitude rescue helicopters are stripped of every non-essential item – Passenger Seats, Avionics, Accessories, you name it – If it’s not needed: It’s Removed!

Engine Performance

The engine needs fuel and oxygen to work. Generally, fuel is never a problem – Unless it runs out, so that leaves oxygen. As mentioned above, the fewer oxygen molecules to work with the less power it produces.

A helicopter engine, like any engine, can only produce a maximum amount of power, once that limit is reached it cannot produce any more.

Arriel 1D1 Engine Off An AS350 B2 Astar – Same Engine That Fred North Flew To Over 42,000 ft

Helicopter engines are designed to produce power to turn the transmissions which turn the main/tail rotors at a fixed RPM. As blade pitch increases, the drag each blade creates increases, and more engine power is required to push that blade through the air to maintain the required RPM.

Think of it like pushing a kids’ stroller at 5mph along a path – easy right! Now try keeping 5mph through a muddy field!
More drag on the wheels = You have to work harder!

The less the engine has to work, the higher it can go before it gets to its maximum power limit.

Cold, dry air will allow a helicopter to go higher that hot, humid air.

Controllability

Being able to control a helicopter at all points of the flight is pretty important! To control a helicopter the pilot needs to be able to control the Main Rotor, Tail Rotor, and Engine/s to keep the aircraft doing what it is supposed to: Fly Upright – Unless you are Chuck Aaron flying in the Redbull Chopper!

Chuck Aaron – Doing What He Does Best!

For all the blades to work they need sufficient air molecules to work on and the engine needs enough air molecules to create enough power. As air molecules in a given area become reduced, the efficiency of which all the blades and engine/s work will reduce.

If there are endless amounts of power ( there isn’t 😉 ), the pilot will find the air becomes too thin for the rotor/tail blades to work off and either the aircraft will stop climbing or the helicopter can begin to rotate because the effectiveness of the tail rotor is not sufficient to counteract the torque being produced from the main rotor. (For another article!)

Either way, the engine will run out of power or the blades will run out of lift. This will be the limiting factor to how high the helicopter can fly for the given environmental conditions.

Regulations

For everyday helicopter operations each helicopter comes with a Rotorcraft Flight Manual or RFM for short. This manual tells the pilot all the things they should and should not do with the helicopter.
The manual also comes with a plethora of performance charts that the pilot needs to ensure the helicopter will perform as expected in any given environmental condition.

The data in these charts are flown and extrapolated during the certification process of each helicopter type by the company’s test pilots. For most helicopters, if the chart says it can do it, then it can do it.
Some manufacturers data is better than others 😉

RFM Limitations & Performance

Maximum Altitude Limitation

To keep pilots safe one of the limitations in each manual is the Maximum Flight Altitude. This is for use in any operation whether it be in forward flight or hovering. This figure has been calculated to ensure full controllability of the aircraft to keep the occupants safe.

Helicopter Altitude Limit Examples
Helicopter TypeAltitude: MetersAltitude: Feet
Schweizer 300CB3,050 m10,000 ft
Robinson R224,250 m14,000ft DA
Bell 206 Jet Ranger4,100 m13,500 ft DA
Eurocopter AS 350 Astar6,100 m20,000 ft
Eurocopter SA 315B Lama7,000 m23,000 ft
Agusta A1396,100 m20,000 ft DA
Mil Mi-264,600 m15,100 ft
Boeing Chinook CH-47F6,100 m20,000 ft
DA = Density Altitude

For helicopter operators to operate at altitudes higher than this limitation they can apply for ‘Limitation Waivers’ from their local aviation governing authority ie: FAA.

These waivers will grant the operator permission to operate within a specific set of limitations, policies, and procedures applicable to high-altitudes to ensure rescue work can take place safely and without breaking any regulations or voiding their insurance.

Hover In Ground Effect (HIGE) Performance

Hovering requires the most power from an aircraft engine. Hovering In Ground Effect is when the helicopter hovers no more than roughly 1.0-1.5x its rotor diameter above the surface.

Eg: Robinson R22 Rotor Diameter = 25 ft
HIGE = Main Rotor remains below 37 ft above the ground/surface

Hovering In Ground Effect – Source: Ronnie Macdonald

This ‘Ground Effect’ helps to improve aerodynamic performance and requires less power to hover the helicopter than if the helicopter was trying to hover 200ft above the ground.

HIGE performance charts show the pilot the maximum altitude they can safely hover for a given temperature, air pressure, weight and wind.

For Example:
Eurocopter AS350 B2:

  • Aircraft Total Weight (Fuel, Pilot, Passengers, Gear) = 4800 lbs
  • Proposed Landing Spot Elevation = 7000 ft
  • Wind at Landing Spot = Calm
  • Temperature at Landing Spot = +10°C

WITH NO External Load: Aircraft Max Gross Weight = 4961 lbs

Checking the HIGE performance chart for that data shows the aircraft can safely operate at that altitude at maximum gross weight. Because the current helicopter is 161 lbs under its maximum gross weight there will be surplus performance available.

Next, the passengers need lots of construction equipment long-lining to the same spot. Now the pilot has to look at HOGE performance.

Hovering Out Of Ground Effect (HOGE) Performance

Hovering Out Of Ground Effect is when the helicopter’s main rotor is hovering higher than 1.0-1.5 its rotor diameter. This usually occurs when helicopters are winching, putting out fires with a water bucket or slinging loads using a Long-Line which are too big/heavy to fit in the aircraft.

Source: Rick James

Hovering Out Of Ground Effect requires the most performance from the engine and the rotor system. The rotors do not benefit from the aerodynamic assistance they get when hovering close to the ground and the altitude the helicopter can hover at is far lower.

Using the some of the same data as before:

For Example:
Eurocopter AS350 B2:

  • Aircraft Total Weight (Fuel, Pilot, No Passengers, External Load) = 4900 lbs
  • Proposed Landing Spot Elevation = 7000 ft
  • Wind at Landing Spot = Calm
  • Temperature at Landing Spot = +10°C

WITH External Loads Aircraft Max Gross Weight Upgraded = 5512 lbs

Checking the HOGE performance chart for that data shows the aircraft can safely operate at that altitude at no more than 4900 lbs.
Because the calculated total helicopter weight is 4900 lbs that does not leave enough safety margin.

To safely complete this flight the pilot needs to reduce weight: Either the aircraft needs to take less fuel or take the load in two runs.

To Finish

As you can see there are many factors that will influence how high a helicopter can go. The same helicopter with the same load, fuel, load etc will be able to go higher in the morning when the air is cool vs the same exact flight in the afternoon when the air is hot.

Flying over Mount Everest is one thing, but being able to land and pick up someone is just not available at this point in time. As engines become more powerful and helicopter design & performance improves there may be a time where anyone can be rescued from the world’s tallest peaks – Weather permitting.

When operating in Hot, High or Humid conditions every pilot needs to reference their helicopters RFM to ensure their helicopter will do what they expect it to do and not run out of performance just at the wrong time!

Further Reading

If you found this article interesting and would like to keep reading, I highly recommend the following articles from my blog:

Rick James

I am an aviation nut! I'm an ATP-rated helicopter pilot & former flight instructor with over 3500 hours spanning 3 countries and many different flying jobs. I love aviation and everything about it. I use these articles to pass on cool facts and information to you whether you are a pilot or just love aviation too! If you want to know more about me, just click on my picture!

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