Why HEMS pilots take off backwards
To an ordinary member of the public, or even members of the emergency services that aren’t versed in helicopter practices, the way that pilots take off and land can seem peculiar. Ian Lewis reveals why HEMS pilots do it backwards
They say a good pilot is one who has the same number of take-offs as landings, and HEMS flying is considerably more challenging than, say, driving a helicopter air taxi. HEMS operations are about safety above everything. And, generally speaking, it’s for safety reasons that pilots do some things that can be difficult to understand if you’re not an aviator. Here’s a look at some pilots’ procedures and requests that might seem mystifying to a non-flyer.
The layman would naturally expect a helicopter to arrive at a landing spot, hover, and land vertically. Similarly, you might expect a take-off to be a simple matter of lifting off the ground vertically and then flying away. While that can sometimes happen, there are lots of reasons why it’s rare to arrive and depart quite like that.
Although it seems counter-intuitive, helicopters are able to glide. But autorotation, as it’s called, just like gliding a fixed-wing aircraft, requires a minimum forward airspeed to create the necessary lift. True, you can only go downward, but you can do it under control to a more or less normal landing. In a vertical take-off or landing, of course, there is no forward motion, but if you are high enough above the ground, you can convert the downward (falling) energy to forward flight and land gently. However, if you lose power at too low an altitude through total or partial engine failure, the helicopter takes on the flying characteristics of an unusually large house-brick. The idea is to reduce time spent in this danger zone.
Whether or not the pilot uses Category ‘A’ procedures depends on the requirements of the operating company and also, of course, the kind of flying they do. Since the profiles are designed for minimising risk in confined areas, if you have plenty of space, you won’t need them. Some pilots we spoke to have never flown a Category ‘A’ take-off or landing. As far as Lorena Knapp is concerned: “These are most often used in the oil and gas industry when departing from a platform.”
On the other hand, Mark Dennis, HEMS pilot with the Midlands Air Ambulance in the UK, uses Category ‘A’ profiles most of the time: “When people see us depart … which nine times out of 10 is from a restricted site, about the size of a tennis court – the question people ask is ‘why do you take off backwards’. It’s the safest way of getting in and out.”
Taking off from an ad-hoc landing site in a confined space, he will typically lift to a hover, perform a clearing turn to ensure that there’s nothing behind and then climb to about 120 ft backwards, because should he have an engine failure, he has already cleared the area he is going to land into and he knows it’s safe. Once he’s reached the safe height, he then commits to forward flight. At that point he knows he has enough height to increase speed and climb away safely on a single engine should one engine fail.
“That’s why it’s important that nobody goes into the departure area until they see the aircraft fly away,” he adds, “because there’s a chance that we may come back down and land. And that might not be an engine failure. It may be some other malfunction or something that means you want to land to check it out.”
Lorena Knapp, HEMS pilot with LifeMed, Alaska, explains: “A prudent pilot is always assessing and mitigating risk. One risk would be the amount of time spent in the height velocity curve (H/V curve). This is a chart created by the helicopter manufacturer to illustrate where a safe landing (autorotation) could theoretically be made if there was an engine failure. There are areas of the curve – often referred to as the shaded area of the H/V curve – where a safe landing may not be possible (low altitude and low airspeed). For many helicopters, the shaded area is somewhere around less than 400 ft and less than 40 kt. To minimise risk, one would attempt to minimise the amount of time spent inside of this curve. This is why helicopters don’t often take off vertically and land vertically as it would maximise the amount of time in the H/V curve.”
The procedure was originally developed for use in restricted area
So-called Category ‘A’ take-offs and landings are one solution to minimising the time spent inside the danger area of this curve for twin-engine helicopters, and involves taking off by flying backwards, which looks extremely odd to an untrained observer.
The procedure was originally developed for use in restricted areas – on oil platforms, rooftop helipads, or simply confined spaces – where the small landing area might be the safest (or only) available place to go in the event of an emergency during take-off; so the pilot needs to keep it in sight as they depart. As an aside, there’s an urban legend that the procedure was developed in the 1970s for landings on top of the International Press Centre building in London, but in fact America’s Federal Aviation Authority had published the profile 10 years before.
In the US, ex-military HEMS pilot and aviation consultant Ed MacDonald says: “In Category A take-off procedures, a twin engine helicopter takes off in such a manner that if one engine fails at any time during this procedure, the helicopter can safely land in the previous take-off area or, at a certain point during the take-off, fly away from the point of engine failure and continue in stabilised single-engine forward flight. Similarly, the landing profile is such that a pilot can determine the decision points on landing. Generally, the take-off is steep and backward, always keeping the take-off point in sight, then a normal take-off profile from that point.”
The Category ‘A’ procedure for landing is more straightforward – and doesn’t involve flying backwards. The Landing Decision Point is likely to be slightly lower than the Take-off Decision Point, and the approach steeper than for a normal landing, and slow. If engine failure should occur above the Landing Decision Point, there’ll be enough height for the pilot to gain speed and climb on one engine. Below the Decision Point, you’re committed to landing.
No room for the elephant
Whether or not Category ‘A’ landing and take-off profiles are being used, there’s a great deal that pilots have to think about when arriving at a new site, and medical and ground crew should be aware of what’s involved.
Lorena Knapp says: “In my job flying medevac, we are often flying into scenes. Although these are often secured, sometimes they aren’t. In a typical scene on the highway, in addition to the performance considerations, I’m also considering the bystanders, vehicles, first responders, wires, and debris on the road. I often think about the downwash of the helicopter as well as how to protect my tail rotor. I try to position the helicopter relative to the ambulance or patient. All of these factors would mitigate risks to ground personnel as well as enhance my visibility on scene and lessen the risk of someone inadvertently walking into the tail rotor. It might also create an approach path that doesn’t look like a typical vertical take-off and landing that many people have in their minds when they think of a helicopter.”
One of the most important things on first arriving at a scene is to pause and take a good look before committing to a landing.
“When we arrive on a HEMS scene, we arrive overhead and orbit,” says Mark Dennis. “Obviously we don’t arrive straight in and land because we need to make sure it’s safe to land.” So those on the ground might wonder why the helicopter is staying aloft, instead of coming down to land
Ed MacDonald teaches: “[A pilot should always] conduct a high reconnaissance (usually at 500 ft AGL) in a pattern that allows good visualisation of the landing area, approach and departure paths, landing zone surface, obstacles, LZ size, winds, slope, and other potential issues (such as vehicles, animals, personnel, security, approaching weather, etc.).”
However well-meaning people on the ground can be, they often miss things that can make a crucial difference to a safe arrival. “There are always wires,” Ed MacDonald adds.
Just recently, Lorena Knapp says, she aborted a landing due to a four-legged friend: “Because the homeowner’s dog (we were landing in their yard) was coming up the driveway towards the house. Had I landed, the dog would have been behind the helicopter and separated from the homeowner. Although the dog probably wouldn’t have gone into the tail rotor, I was concerned about the homeowners attempting to catch the dog and running around the spinning helicopter. The noise of the helicopter tends to make everyone a bit frantic and it is extremely difficult to get someone’s attention if needed. It was easy enough to do a go around and wait until the dog was reunited with [its] owner and restrained prior to landing.”
Animals of all kinds can be a hazard under-appreciated by people on the ground. Several pilots mentioned the need to secure horses or cattle near the scene of an accident before a helicopter can land. Dennis even talked of problems with elephants in a safari park where he was expected to land. Differing expectations and communication problems can also mean trouble. He tells of an occasion when he flew to an accident during a motocross competition: “Obviously, motocrosses are very busy and often they don’t stop the race, and obviously I can’t land until it’s stopped, because the patient is on the track and they seem to think they can just carry on racing around the aircraft. So then we’re going round and round and round trying to get communication with them to tell them to stop the race, and they’re thinking, well why isn’t he landing?”
So, even though helicopter pilots sometimes appear to be performing strange manoeuvres, or not to be doing what’s expected of them, there is (normally) a good reason for their behaviour. Julian Spiers, aircrew supervisor and critical care paramedic at Midlands Air Ambulance, UK, observes that in their area, the rural (ground) ambulance crews are used to dealing with helicopters and understand what’s needed, whereas city ambulance crews who rarely see an air ambulance are not so aware of the safety requirements of helicopter operations. Perhaps one answer is more training for everyone.
A final word from Ed MacDonald: “EMS operations tend to be more hazardous because one never exactly knows how well trained and competent the person(s) setting up the landing zones may be and whether or not it is truly safe. We train and incorporate the team concept on every flight to empower medical crews to speak up when any hazard or hazardous behaviour is observed. Training and incorporating all aspects of air medical resource management is critical to safe air ambulance operations. Initial and continuing training of flight and ground crews must be done to help reduce risks of all phases of flight.”