Landing a helicopter off-airfield
One aspect that makes helicopters unique is their ability to land ‘anywhere’, so in this article we will explore the factors that go into deciding where, and how to safely land, away from the airfield!
In this article, we will have a look at firstly the rules behind where you can land, the differences between single and multi engine helicopters, the preparation you can perform on the ground when selecting and assessing the landing sight, the pre landing reconnaissance, and different approach techniques, and finally, some suggestions for once you are back safely on the ground.
Regulations and Legality
So firstly – where and when can you land at a ‘private site’? This is a question that is dependent on the type of helicopter and where in the world you are flying, but generally, aviation regulations are in place to ensure the safety of the occupants of the helicopter, and those on the ground, so providing pre notification and approval from the your landing site’s operator, often known as ‘land owner’s permission’ is a must, however, additional paperwork may be required before you set off.
Many a pilot has learnt this lesson the hard way after receiving a hefty fine from authorities !
Below are some examples of additional requirements required by the aviation authorities, and ‘The Helipaddy blog is a great resource for checking against specific information required for flight for many countries:
- Non-Swiss (HB) registered helicopters need a permission from the FOCA for off airport landings. It costs Sfr. 500 per year.
- If landing at a restaurant, you need to ensure a minimum 100 meters distance from landing spot to the restaurant due to security and noise.
- The general rule says that, below 1100 meters AMSL, landings are permitted with some exceptions. Above 1100 AMSL it is prohibited with some exceptions.
- Private helicopters are generally permitted to land at hotels in Germany, subject to certain conditions and regulations.
- Firstly, the hotel must have a designated landing area that meets safety standards set by the German aviation authorities. The landing area must be cleared of any obstacles, have appropriate markings, and meet the minimum size and weight requirements for the type of helicopter being operated.
- Secondly, the pilot must obtain the necessary permits and clearances from the relevant authorities before landing at the hotel. This includes obtaining a permit from the German Federal Aviation Office (LBA) and clearance from the local air traffic control (ATC) authority, if applicable.
- Thirdly, the pilot must comply with all applicable aviation regulations and safety requirements when operating the helicopter. This includes ensuring that the helicopter is airworthy, that weather conditions are suitable for the flight, and that all necessary safety equipment is on board.
- United Kingdom
- Helicopters landing or taking off are exempt from the requirement to maintain 500ft away from any vehicle, vessel or structure, however, in a single engine helicopter, there are restrictions on landing in ‘hazardous terrain’ – congested, urban areas, where an engine malfunction at the latter stage of the approach or takeoff may not result in a safe autorotation or forced landing- this is due to the helicopter operating under ‘performance class 3’.
Researching the landing zone
The site guides held on the Helipaddy database are a fantastic source of information, firstly to obtain contact details of the landing site operator, but then to establish where exactly on the site you should land, what sort of obstructions exist, and if any noise sensitive areas exist in the vicinity. This final point is especially important but sometimes overlooked!
Unfortunately, not everyone is a fan of helicopter traffic, and whilst we of course advocate always trying to ‘fly neighboughly’ , checking for any noise avoid areas before you fly can save yourself from an expensive mistake . An example is the Four Seasons Hotel in Hampshire, U.K., where you have to pay a £1000 landing fee deposit that is only refunded if you correctly follow their arrival/ departure routing.
Some helicopter emergency services, whom don’t have the ability to pre assess the landing areas, use a technique of a ‘dynamic risk assessment’ to evaluate the landing site.
This comprises of a scored checklist of items including terrain, time of day, qualification and recency and fatigue level of the crew, weather, proximity to obstacles and the serviceability of any onboard aircraft equipment (such as a night search light) that can be used to check the landing area. The scores are then summed up to determine the total risk and the required mitigation that need to be carried out.
Choosing the correct approach technique
Using the right approach for the confined area is a key decision ensuring a safe landing.
We will start with a quick revision on approach profiles for single engine helicopters. Obviously the flight manual of each type of helicopter provides guidance on the specific ‘numbers’ for normal approach profiles, but the general technique is similar. It is important to point out that the height velocity diagram – dead man’s curve- which is used to illustrate where a safe auto-rotation may be achieved, does not apply to the initial stages of the approach and landing, as the helicopter is already descending with a low blade pitch angle.
A helicopter can make shallow, constant angle or steep approaches to a landing spot depending on the type of obstacles on the approach path and the size of the landing area. The final section of the landing may involve touching down to the ground using a hover landing, a no hover landing, if there is blowing sand or snow (which we will cover later under the reconnaissance stage), or even a running landing, and it’s down to the pilot to select the relevant technique for every landing site, depending and the conditions at the time, for example, the wind, altitude, temperature, weight and performance of the helicopter.
A. Constant Angle Approach
For a large area, clear of obstructions, a normal single engine approach can be used.
The helicopter turns onto a final approach track, aligned with the landing area , at around 500/600ft above the ground, and be established at around 60-70kts.
From this point, the approach angle and the closure rate is judged by eye, as you adjust your ground speed, compensating for any wind that exists. The rate of descent should be around 500ft per minute, and as long as the airspeed is maintained greater than around 30 – 40kts, there is no risk of entering the vortex ring state phenomenon. This is where the helicopter can enter an uncontrolled descent, which cannot be immediately corrected with raising the collective (see below for more details).
The basic technique requires selecting the correct sight picture of the designated landing spot on the windshield, and adjusting the collective to keep this descent angle constant. The risk of being too low on approach is that you may potentially be closer to any obstacles under the approach path, whilst the risk of being too high means that an excessively steep approach comes with the tendency to then slow the helicopter airspeed, whilst then increasing the rate of descent, which could put you in the conditions for vortex ring – and you wouldn’t have enough height above the ground to correct this in time!
Throughout the approach, the cyclic is used to control the apparent ground sleep, maintaining a slow walking pace, and by the time you pass through 30kts indicated air speed, the rate of descent should be less than around 300 ft per minute.
As with all approaches, if the approach has been misjudged and you are too high, too low or the landing area is no longer safe, e.g. people have walked onto the landing pad, then a go around should be flown, where max power is applied with the collective and you climb away at the best rate of climb speed.
For landings into smaller, confined areas, different techniques must be used, such as the can use a double angle, or vertical descent.
B. Double Angle/ Steep Approach
Using the double angle method, you perform an approach to just above the height of the obstacle that obscures your landing area. Once you have safely cleared this you adjust your descent angle, to perform the final section of the landing at a steeper angle. This requires adjusting the collective lever to control the rate of descent whilst reducing the ground speed with aft cyclic input.
C. Vertical Descent
The final method we will look at is the vertical descent, used for very tight pads with obstructions both ahead and behind the landing site.
This technique requires enough power in reserve for an out of ground effect hover.
A constant angle approach is performed to a height about 10ft above the top of the highest obstacle in the vicinity of the landing pad. From here, a forward and side marker is selected so that you can correct for any movement whilst descending vertically.
These markers can be a distinctive tree, a fence post or building- as long as it is suitably far away so that it is visible throughout the manoeuvre; it can be used to prevent you from drifting away from the clear spot of the landing pad.
Once in the stable hover above the pad, slowly reduce the collective for a gentle descent down. If you have experienced passengers onboard, make use of them to look behind, to the side, and below the helicopter to check for any previously unseen dangers!
As with all these manoeuvres, the tail rotor forms the most venerable part of the helicopter, and great care should be taken to protect it from any obstacles.
It is also worth reminding that when looking forward, the distance from the pilot’s seat to the tip of the rotor blade is less than the distance from the pilot seat to the lateral extremity of the rotor disk – it can be all too easy to misjudge distance and inadvertently clip a tree!
Differences with Multi engine helicopters
A quick look at multi engine, ‘CAT A’ Performance Class 1 helicopter operations (which is the basis for most multi engine ‘charter’ flying in the U.K.) – for a full description of CAT A vs CAT B operation see below
In short however, when performing a CAT A approach, a set landing decision point ( or LDP) is defined in terms of speed and height from the landing point.
If correct profile is flown within the weight, altitude and temperature limits set by the manufacturer (known as operating in performance class 1) , if there is an engine malfunction before this landing point, the pilot can either safely abort the landing, known as a balked landing, or can continue on the remaining engine to land at the designated area. If there is an engine failure after this LDP, the pilot is committed to landing safely, using the power from the remaining engine.
Basically, if you are operating performance class 1, there is no dead man’s curve / height velocity diagram to worry about. This means that landing sites that are within congested areas, or elevated on top of a building are approved for used.
As with single engine helicopters, there are different landing profiles for multi engine helicopters, depending on the size of the area the helicopter is going to, usually split into a clear area profile and various vertical profiles (known as VTOL’s- ‘vertical take off and landing’).
As an example – for a ‘clear area arrival’ for the Eurocopter EC135, this area has to be at least 220m long and 15m wide, so that there is enough space if the helicopter needs to abort the approach whilst flying on only one engine. The LDP is defined as 80ft above the ground and airspeed of 30kts. Once through this gate, you are committed to landing. The ‘VTOL 1’ profile is used for tighter confined areas, and for the EC145 helicopter, the LDP is defined as 30kts, and 100ft above the landing area. If there is an engine malfunction before this point, the remaining engine has sufficient power to permit the helicopter to safely go around (known as a balked landing) or commit to landing.
An important consideration to check before landing is the helicopter performance, and is it suitable for the type of approach and size of the pad that you are landing at. Whilst you will have a good idea of what power you are using when you take off, and on arrival at destination, will be lighter due to fuel burn, check against the flight manual for the stated performance for an out of ground effect hover – if you need to do a vertical descent into a tight landing spot.
Additionally, factor in any change of conditions, for example, you might be flying up to a mountain helipad, where the density altitude is significantly different from where you took off – closer to sea level. Even if the flight manual states you have sufficient power available, it is always worth a check in flight before committing to the landing.
Applications such as the Gyronimo ‘Tim Tuckers’ R44 and R66 App for Apple iOS are handy for experimenting with various atmospheric conditions (temperature, pressure, attitude) and helicopter weight to check expected performance.
The application also alows you to to see what impact ancillaries (anti ice/ heating etc) have on the rate of climb and hover ceiling .
Below are some ‘rule of thumb’ examples for in flight, however, an alternative method is to assume an additional 10% extra power from ‘Hover Takeoff power’ is required for an ‘out of ground effect hover’.
- fly straight and level at the minimum power speed- 53 kts – (R22) or 55 kts (R44) – take note of the power required on the manifold pressure gauge and then compare the maximum power used chart (if flying a R22 or Raven 1 with a carburetted engine, ensure the carb heat is set to off during this check).
- If the difference is <3 inches – expect power for a running landing only . Not suitable for a confined areaIf the difference is <4 inches – expect power for a Zero / Zero – no hover landing . Not suitable for a confined areaIf the difference is 5 inches – expect power for a normal – constant angle approach and in ground effect hover only . Not suitable for a confined area unless large forward area, and clear of obstructions on the undershoot
- If the difference is >6 inches – sufficient power exists for a out of ground effect hover. suitable for tight a confined area requiring a double angle or vertical descent
- >10% N1 margin OGE hover / vertical descent available.
- Fly straight and level at the minimum power speed- 60kts – take note of the N1 speed required and then compare it to the maximum N1 permitted. Compare the difference below
- 0-3 % N1 margin – run on landing required
- 3-5% N1 margin – Zero/Zero ‘no hover’ landing required
- 6-10% N1 margin – Normal constant angle / Steep approach landing Available
- >10% N1 margin OGE hover / vertical descent available
- Alternatively if you have 25% torque spare (ie using 75% torque or less) – you can perform an OGE hover.
Gumbal G2 Cabri
Fly straight and level at Vy- 50kts, note power % required. Power available = max power – actual power required for 50kts.
- Power available < 20% – Running landing
- Power available > 20% – Zero / zero landing
- Power available > 25% – normal single angle approach
- Power available > 30% – Steep- double angle approach
- Power available > 35% – Vertical descent with OGE hover
Vortex Ring State
Vortex ring state exists when the helicopter is descending inside its own turbulent downwash, and the rate of descent cannot be stopped by raising the collective alone. There are 3 conditions required to enter vortex ring:
Greater than 300 ft / min
Rotor not in auto-rotation
Less than 30 kts airspeed
The threat of entering vortex ring during a confined area landing exists for a number of reasons.
Firstly, you may not have the luxury of a wind sock or accurate wind recording facilities at the landing site. Either through a change of the wind, local conditions, limited approach options or simply pilot error, it is easy to commence an approach downwind.
During a downwind approach (or very steep approach with a low wind speed) , the airspeed can easily drop below 30kts whilst still maintaining a slow walking pace. As the airspeed reduces, the rate of decent will increase if no other corrections are made.
If this is not detected and corrected early enough, of you are already operating at max power, then the rate of decent can quickly build and enter the danger area of vortex ring operation. Unfortunately, recovery at this stage can be difficult as you may lack the height and clear area ahead of the helicopter to perform the nose down, speed increase recovery. (Have a look at the Vuchard manoeuvre / recovery during your next flight with an instructor and ‘keep this one in your back pocket’.
If you do need to perform a downwind approach, it is very important to keep a watchful eye on the vertical speed indicator (VSI) and use more power on the approach to ensure it doesn’t increase above 300ft/min
Even if you have comprehensive site details from HeliPaddy or aerial imagery, a site reconnaissance is important to check that the site is suitable.
A good way to break this up is the high and low level reconnaissance, and using the 5’s and 4W ‘s as a memory aid.
Once you arrive at the landing site, a high reconnaissance orbit around the site, flown at around 60kts at 1000ft above the site is a good way to build situational awareness of the general surrounds, size and shape of the site, and quickly identify any hazards that might exist.
Once you have assessed the site as suitable, and come up with a plan for the direction and type of approach, flying a low resonances, as a low approach and go around at 500ft above the pad is a chance to reveal more detail about the surface conditions, whilst being on the lookout for any wires or obstructions.
5 S Site Checklist
In certain seasons or landing conditions, the checklist can be extended to 8S’s, as listed below
Is it large enough for your helicopter
Which direction gives you the longest landing run
What happens if the engine fails- what is the safest route in and out?
Is it too steep, which skid is best ‘upslope’?
Can you expect any Ground Effect benefit, can you see any loose objects(FOD)?
Especially in winter or when flying just before sunset or after sunrise when the sun is low in sky
- Snow & Sand
Consider the implications of loose blown snow or sand on visibility (whiteout or brown out conditions) if landing on a beach or after fresh snow in winter
Be aware of the presence of livestock – a farmer wont be too impressed if you cause a stampede due to a landing helicopter.
The minimum size site that you are comfortable landing at depends on your experience, training, helicopter type and conditions of the day, however it is vital to Know your maximum length / width dimension (D), and to check this against the clear area space around the landing site. During your flight training, you might have found the sensation of landing in a ‘confined area’ the size of a football field felt tight, compared with the relative luxury of an entire airfield.
Bear in mind that even the HEMS professionals that land everyday away from base to save lives have a limit of 2D during the day and 4D during the night.
Ideally, an approach should be made to the longest length of the landing site. As with all off airfield landings, you must weigh up a range of factors and make a ‘captaincy’ judgement on what is the beneficial consideration- for example, making an approach into wind, or away from a build up area, but accepting a sub optimal landing direction.
Alternatively, consider if can you make a slight turn at the final stage of approach to make full use of the landing area available?
What are the surroundings to the landing site? Is it located in an open area or bounded by any water features? Is there a natural clear approach direction that keeps you from overflying houses, trees or obstructions at low level? Is this route aligned into the wind direction that will help directional stability and power requirements? Do you have sufficient power reserve to accept an out of wind approach? If the landing site is bounded by trees or other high obstacles, consider the impact of any recirculation of the downwash or turbulence that might occur- in winds >15 kts, if there are trees upwind of the landing site, you can expect wind shear and a loss of indicated airspeed as you descend through the height of the tree line.
Is there a ‘clear escape route’ that you can perform a go around if you are unhappy at any stage during the landing- this is especially relevant if landing on the side of a hill or valley, where you should avoid pointing directly into a hill face during approach.
Perception of a slope angle and direction is tricky from the high reconnaissance, and sometimes the full extent of the slope can only be perceived once in the hover.
Before you set off, remind yourself of any slope limits in the flight manual and what is the ‘best slope’ direction for your helicopter.
The Robinson series helicopters naturally flies left skid low when loaded with passengers due to the placement of the tail rotor. Therefore, these helicopters should be landed on a slope in the following order of preference wherever possible:
- Right Skid Upslope
- Nose Upslope
- Left Skid Upslope
- Tail Upslope (dangerous due to the proximity of the tail to the ground)
WARNING: Always have the passengers along the slope-else they can walk up into the blades (head strikes will be fatal). It’s worth reminding them just before they get out the helicopter, or even better, shut down the helicopter first if possible!
If you are not happy with the slope- lift off and find somewhere else!
The surface has an impact not only on the hover power, but also introduces considerate when landing.
A hard surface such as concrete provides more ground cushion, reducing the power in the hover, whilst long grass, uncut agricultural fields and water all dissipate the positive effect of the ground cushion, sucking you into using more power for hover. (The more you can see the effect of the downwash, the less the effective of the high pressure cushion!)
When setting the helicopter down- be wary of soft surfaces that a skids or wheels can sink into. It can be very unsettling to have a helicopter suddenly lurch after landing into snow, after it suddenly compacts – especially if the tail rotor is close to the ground! If you are regularly landing in slow, think about investing in a set of ‘bear paws’ – metal plates bolted to the rear of the skids to increase the surface area, reducing the surface pressure from the weight of the helicopter.
Wheeled helicopters, such as the AW109, need to very cautious during the winter months that they don’t sink into soft ground. The Essex & Herts HEMS AW169 helicopter has bear paws fitted in the winter, disabling the retractable undercarriage, to counter this issue.
Long grass can also hide an uneven, rocky surface, or even stakes and electric fence posts. Before lowering the collective all the way down, proceed slowly to ensure the helicopter is secure. Electric fences can cause issues not only if they are switched on, but can easily get tangled around the skids, tail rotor or even fly up in the downwash into the main rotor!
In a helicopter with a low hung exhaust, such as the R22, R44 and MD500, the hot engine outlet can also pose a fire risk to the ground foliage. A huge bush fire was caused in Jan 2020, central Australia, which was attributed to army helicopter landing, and more recently a geological survey R44 in June 2022 was destroyed in a similar fashion when landing around some dry spinifex grass! The Austrian authorities noted 5 occasions within 10 years where Robinson helicopters specifically had been destroyed by self ignited ground fires.
During the winter, when the sun is lower in the sky, can lead to poor visibility and haze, especially when conducting an approach towards the west, with the loss of visual references hiding obstacles in the shadows.
Whilst evaluating the approach path, if the surrounds and wind direct permit, consider conducting an approach that doesn’t require you to look directly into the sun.
Snow & Sand
Landing on a beach or after fresh snow brings the additional risk of loss of visibility during the final, critical stage of landing – officially known as a ‘degraded visual environment’, if the particles are thrown up into the air by the downwash.
Specialist techniques and equipment are used by operators whom commonly perform this work, such as the military or mountain heli skiing pilots, and can involve using a ‘no hover’ approach to keep the brownout/ white out behind the cockpit until touchdown.
If you haven’t had experience or training in this, 6 ft above the ground in a tight landing spot isn’t the place to become a test pilot. Before you commence your landing, if there is a risk of loose particles on the ground, be prepared to pull pitch and go around if you see a dust/snow cloud forming , and get away from the ground safely, well before you are enveloped in it!
As obvious as it seems, the presence of livestock can make a big impact on your decision on where you land. Helicopters are often used for herding cattle, but the local farmer is probably not going to be impressed with any impromptu airborne sheep rustling. Be aware of the noise impact on any horse riders, as helicopters have been known to spook horses, flipping their riders off, potentially leading to serious injury. If you are not happy with the proximity, go around and wait until they have cleared the area.
If you do land in a field with livestock, be aware that whilst they may stay well away during landing, cows are curious creatures, and it has been known for helicopters to be seriously damaged by animals rubbing up alongside warm engine compartments long after the helicopter occupants have left! You will also need to move them well away before you start up the helicopter for departure later!
Always expect wires at an unprepared landing site. This reinforces the need for prior preparation- check the information provided on the HeliPaddy site guide, or even a check on Google/Bing maps – but, the information could be out of date, new poles could have been erected since any satellite mapping updated , or the pad owner has been refreshed the data.
Unfortunately, behind loss of control when inadvertently going IMC, flight into wires is the biggest cause of helicopter accidents. Regrettably these accidents often occur when the pilot is even aware of the nearby wires. Remember, that actually seeing the wire is incredibly hard, so look for the poles instead. If the approach path permits, fly over the poles that support the wires, rather than between the pole- this provides confidence that you are clear of the wires.
Finally, be careful if your approach or departure takes you down a valley- as wires are often strung out across a valley from peaks on either side. If possible, use every pair of eyes on board to keep a look out for wires on the final approach!
his is a chance to establish what your approach path is going to be, and to visually set ‘turning points’ for the base leg and final approach turns.
Does your route take you over any items that could be picked up by your downwash and turn into dangerous flying objects, such as unsecure outdoor tables, chairs and parasols?
Recently, the downwash from a departing air ambulance helicopter in Surrey, UK turned an umbrella into a missile that caused a significant head injury to a person in their garden, and in Gwent, UK, in Sept 2022, somewhat ironically, a helicopter safety sign injured a person on the ground when it became blown over by a landing Jet Ranger.
Unless you have a radar altimeter, or know the elevation of the landing spot, setting up your approach is largely a visually estimated method, as the height of the helicopter above the ground is unknown. Fortunately you can obtain a rough elevation from ‘SkyDemon’ and ‘Runway HD’ to help set up an approach, and the Helipaddy Pad data provides the spot height, so you can set up an approach by deducting your altitude from the elevation of the pad.
Consider any local terrain features that may impact the wind direction or cause turbulance and wind shear during the approach, for example, if there is a large obstruction upwind or if the pad is located on top of a hill
Before you commit to landing, consider how you are going to be leaving the landing site. Bear in mind that you may not have the same performance if you are leaving the aircraft overnight, uplifting fuel, or taking additional passengers when you plan to depart. Take note of any obvious features that can be used for navigation.
Unfortunately, not every landing site is blessed with a windsock. If you cannot get an accurate reading of the wind on the ground, try contacting the nearest airfield on the radio (or by phone before you set off) to get a general idea of conditions, though bear in mind that local variations may impact this. look out for tells on the ground, such as the direction that crops are being bent, or for flat, shielded regions on inland lakes that indicate where the wind is coming from.
Once on the ground
Once you are safely on the ground, watch out for bystanders who become interested in the helicopter. If possible, before hand, try and organise a person to meet you on the ground whom can hold back onlookers from approaching before the helicopter has shut down. If the ground surface permits, consider parking the helicopter so the tail boom is facing away from the main entry point to the pad, so you can see if any members of public are approaching.
If you are leaving the helicopter overnight, consider hiding any loose articles under the seats, and perform a thorough pre flight inspection before the next flight, especially if the helicopter is accessible to members of the public. Consider hiding the aircraft keys on a transmission/engine access panel than only a pilot would be aware of.
Landing off airfield is an exclusive ability of a helicopter, and one of key attractions that inspires pilots to fly. To ensure a safe arrival, there are a number of factors that need to be considered, and ultimately the pilot has to weight up various, sometimes conflicting, considerations to decide how and where to land, but key to a successful outcome is the time spent prior to takeoff, reviewing the available information on the landing pad , checking the helicopter performance, and planning your flight path accordingly.
In the next article, we will have a look at the different ways of safely getting out of a confined area!