When you look at helicopter accident statistics, they don’t compare well with fixed-wing – and HEMS figures do even worse. Jop Dingemans and Janine Lynthe of Pilots Who Ask Why take a look at the threats posed by HEMS operations.
This article was published in the December 2024 / January 2025 of RotorHub International. To read more articles like this, apply for your complimentary subscription to RotorHub International.
The high-risk nature of HEMS operations
Compared with our cousins in fixed-wing, helicopter flight crews have a lot of threats to manage on a daily basis, but the reality is that the risk from mechanical failure is actually quite small.
The nature of rotary operations elevates risk, and none more so than in HEMS (Helicopter Emergency Medical Services) operations. Consider this data from EASA’s 2022 annual safety review. Over half the Category A accidents and serious incidents were in HEMS operations.
The report notes: “With seven occurrences (four accidents and three serious incidents) in 2022, the figures involving HEMS operations are still above the average figures of the preceding decade for this type of operation.”
So then what are the prime threats that push up HEMS rates? At the top of the list, Controlled Flight into Terrain (CFIT) is the main reason for the relatively poor safety statistics of the rotary wing industry. CFIT happens when an aircraft inadvertently flies into terrain, obstacles or water, usually due to poor visibility conditions.
Drivers of CFIT accidents – Pilot decisions, weather, and operational challenges
Pilots electing to continue flying VFR when IMC conditions prevail has been a talking point for a very long time and a number of factors have been shown to be elements for consideration.
Among these are:
- A lack of viable IFR options or infrastructure.
- The inability to meet fuel reserve requirements (more on which later).
- A lack of confidence as a result of competency or recency.
The trouble is that while there has been recognition of the threat and a lot of talk about it, so far there has been no clear-cut proposal to rectify the problem.
Bad weather – Poor visibility impacts on helicopter hazards
Poor weather conditions can make it difficult for flight crew to safely operate. Even if the helicopter can take off and land, the crew may be forced to reduce altitude and airspeed, increasing the time it takes to reach the patient.
In addition, it is possible that the weather allows for a take-off, but a landing at the destination is not guaranteed. This makes the entire operation more complex, requiring more plan Bs and Cs, etc.
Allied to the CFIT question, and continuing VFR in marginal IMC, is the question of inadvertent entry into IMC (IIMC).
Paradoxically, while more flight under IFR would seem likely to reduce the risk, unplanned IMC entries have the reverse impact on safety.
It’s a familiar scenario – a crew is dispatched to a horrible accident. There are children involved. The emergency services are at the scene but injuries are severe and a helicopter is needed.
At base, the weather is okay, but there are no weather stations nearer to the scene. En route, things deteriorate – the cloud base lowers and RADALT bugs are set to the minimum.
The crew thinks to themselves, “We don’t really want to descend any more than this.” With two miles to go, the weather becomes below limits – so what happens next?
Of course, the safest thing would be to return to base. But the accident reports over the last 20 years or more paint a different and sadder picture.
“We got this far, we’ll just take a look a bit further.” The sunk cost fallacy, push on-itis, self-induced pressure, hero-ism, macho attitudes and ego all come into play.
Situations like this, not just in the air ambulance industry, have led to countless IIMC occurrences, and often they do not end well.
It’s these moments that define us as pilots. Do we listen to the emotional or to the rational side of our brain? Do we safely return to be able to dispatch to a different job? Or do we push on while taking on an unacceptable amount of risk?
Of course, there are always other solutions. Maybe rendezvous with an ambulance or crew collection vehicle at a location where the weather is suitable.
The industry push to get helicopter pilots IFR-rated, even the ones who primarily fly VFR, has been one of the attempts to address the issue. It will be interesting to see whether this change makes a substantial difference.
Having an instrument rating (IR) should make you more inclined to consider IFR as an option. But is it enough? Only time will tell as we get the data.
Does a pilot flying in poor conditions under high workload feel comfortable enough to rely on skills he only uses three times every 90 days?
Another issue is that going IFR usually means the mission can’t be completed due to distances to airfield and the time it takes to conduct a full IFR approach procedure.
The benefit of a helicopter, though, is that if at any point you’d rather be on the ground than in the air, you can select an ad hoc landing site anywhere on the ground that is suitable, and land! Plenty of fixed-wing pilots would love to have that luxury!
The strange thing is that in the case of many accidents, crews have not taken that option. Why this is so remains a mystery.
The question is, if you thought it likely that you might need such an alternative, should you have been flying in the first place?
An added weather factor is that is that air ambulances don’t usually fly to airports. This means that weather reporting facilities are generally not available. If you’re landing in the middle of nowhere, you might not even have an airport within the entire area.
Weather decisions are now based on forecasts, which can be very unreliable. Good decision-making relies on accurate data. This is especially true if you’re flying in an area where there are a lot of microclimates, such as near coastlines, ridge lines, mountains or forests.
No situation is black or white, and lots of pilots will have a different opinion on various situations.
Knowing where you are on the scale from very conservative to more risk-taking behaviour is helpful to debrief yourself after every flight, and to see where you can improve.
Drones and birds – Low-altitude collision risks
Helicopters fly low. Drones and birds fly low. A bunch of seagulls aren’t going to NOTAM their intentions. Neither is the kid that just got a new drone for his birthday. Awareness, planning, and vigilant behaviour are the only remedies for threats like these.
Working together as a crew and flying defensively to expect the unexpected can help mitigate some of these risks.
There is a risk that pilots can become complacent about things that have not happened in 35 years of flying in a low-level environment.
But unfortunately, just because you haven’t had a bird strike in 35 years doesn’t mean you won’t have one today or tomorrow.
And even if you have been flying without certain risks, things change.
We know from personal experience that drones appear almost every time you land on scene.
People are excited by the arrival and start filming with their drone. While drone strikes have not figured much in accident data, that status quo may not last.
Commercial and self-induced pressure – Pilot decision-making under pressure
The mud-flinging contest about whether it’s self-induced or commercial pressure that drives pilots to make ill-advised decisions is pointless. At the end of the day, pilots still make decisions that are affected by something that doesn’t prioritise flight safety.
Why do pilots fly into mountains, take off in fog, or push on below limits and hit a power line? Why did they refuse to go back to base and live another day?
On far too many occasions, the answer has been commercial or self-induced pressure.
Of course in HEMS operations, the nature of the job is often one with lives at stake. Most operations manuals mention the responsibility of the pilot to weigh the medical risk of the patient against the aviation risk.
But this shouldn’t mean that once someone is dying on the ground we can just ignore the rules and do whatever we want to get to the scene.
Interestingly, in some parts of the world, flight crew aren’t told about the type of patient, to protect them from emotional pressure.
You could argue that having all the data available helps HEMS crews make the most informed decisions, but you can also argue that it drives the wrong decision.
Training and awareness is the answer here. Being aware of the urge to push into conditions you’re otherwise not comfortable in, is crucial to addressing the issue.
Would I lift if the patient wasn’t in the circumstances that they are currently in?
But it’s not just HEMS. It happens all across aviation.
Companies have to juggle profit-making and flight safety. These are two factors that are often on opposite sides of an argument.
Businesses have as their priority profit. You can’t blame them for having this goal, they’re businesses for a reason. But flight safety has to be a priority too.
Regulators need to step in and make sure that this responsibility isn’t an “option” but a requirement.
Uncontrolled landing sites – Hidden dangers of emergency landings
The nature of HEMS operations means that most of the landing sites are uncontrolled. Uncontrolled landing sites pose a threat as there are a lot of unknowns at the site that can be hard to spot during the recce.
While tools are available to spot threats like power lines, elevation differences, or even covered reservoirs, there will always be a risk for things to be there that are hard to plan for or recce.
A farmer could have built a mast that takes a random power cable across a field, there could be a child at the site flying a drone or a kite, etc.
None of this could ever be planned for on a plate or pre-flight briefing, other than to expect the unexpected and be attentive throughout.
Another risk is brownout or foreign object debris (FOD). The risk of damaging public property or causing harm to people because of objects being blown around by rotor downwash is always a factor and needs to be mitigated even at known landing sites like hospital helipads.
Relatively low fuel capacity – Balancing helicopter payload, range, and safety
Useless things in aviation: altitude above you, runway behind you and fuel in the bowser. Fuel equals options.
Decision-making is always easier to manage when you have options. Unfortunately, and particularly when it comes to IFR flight operations, helicopters often don’t have great fuel capacities – especially when they’re also loaded with medical equipment, patients, and medical crew.
It’s a delicate balance between carrying enough equipment to be able to do the job, while also having enough fuel that “you might not use”. It’s a hard sell to someone who isn’t familiar with aviation or has a mission to accomplish using a helicopter.
Even something like an unplanned VFR to IFR conversion in flight comes with the question of “do we have enough alternate fuel?” and “are we legal to convert to IFR here in regard to our fuel capacity?”
Often, the answer is a pretty clear “no” due the nature of the job. These are important questions, but are often what stops pilots from safely converting to IFR.
Flight crew fatigue – Managing sleep deprivation and high-stress night missions
Fatigue is another significant threat to air ambulance helicopter crews. Pilots go from being asleep at 02:00, when the mission comes in, to flying in poor weather, low level, in a complex aircraft with lots of variables to consider, only half an hour later.
Indeed, for most, that is the nadir of their circadian low (WOCL). It is not a transition humans are designed for.
In addition to the unnatural transition from sleep to alert wakefulness, night shifts are often 12 hours long, with “back of the clock” WOCL periods.
This has been proven to have long-term health consequences, while the impact of chronic fatigue can also have detrimental impact on flying ability.
Luckily, HEMS is slowly moving towards a multi-pilot environment, where pilots can help each other and can cross-reference data and decisions.
That said, there are still lots of air ambulances across the globe that are flown single pilot.
Hostile terrain – Navigating high-risk environments
Then there’s terrain. Whether in congested areas or not, hostile terrain can be tricky to deal with.
Depending on the country you’re in, most hospital landing sites require performance class 1 to be adhered to, while HEMS operating sites can be flown to using performance class 2.
This means that when flying to a hospital, extra care must be taken to make sure you’re flying the correct profile, with appropriate reject or go-around options available.
Not to mention not overflying hospital buildings, following noise abatement procedures, and ensuring a safe approach path with a headwind component.
During the approach, things like trees, masts, car parks, people, wires, buildings and vehicles can all present a threat.
If you’re flying HEMS with only a single-engine aircraft, making sure you have a safe forced landing area available in case of an engine failure can be a challenge.
Human factors – Improving pilot error, stress, and fatigue
Human error is still one of the prime factors influencing aviation safety.
The only way we can improve this is by proper training, CRM awareness, flat cockpit hierarchies, and a just culture.
Proper decision-making, whether multi-pilot or single pilot, can be the difference between a serious accident and a safe flight.
Prioritising safer HEMS operations to reduce accidents
All the threats discussed can be mitigated with rational and thorough decision-making, preferably as a team.
We’ll cover this topic more extensively in future, but human factors can influence incidents or accidents in a raft of ways.
Fatigue, personalities, stressors, distractions, teamwork and many others are all hugely relevant and will stay that way, until we all get replaced by AI.
Threat management will continue to be hugely relevant for the air ambulance industry. The threats discussed here are not an exhaustive list but are factors that influence flight safety for HEMS crews.
We hope you enjoyed reading this feature. You may find these news stories interesting:
LCI to provide two AW139 aircraft for HEMS operations across Torres Strait
ADAC to explore HEMS support with two Volocopters
LCI places seven AW169s for HEMS operations in British Columbia
