How to avoid IIMC, not what to do if it happens


I’ve been a helicopter pilot for over 50 years and I find it interesting that during this time the helicopter community has never settled on a consensus for what a pilot should do when they suddenly punch into the clouds. Hell, we haven’t even settled on what to call it, let alone what to do about it. Early in my career it was called “Inadvertent IFR” which is obviously technically incorrect so it became “Inadvertent IMC”, technically correct but shortened to “IIMC” or “double IMC”. Then the Commercial Aviation Safety Team came along and changed the term to “Unintended IMC (UIMC)”, which I think is where we’re at now. I’ll use both, IIMC and UIMC.


But what to do, the thinking has been and still is, all over the map.


However, before I go any further, I want everyone to clearly understand we are still killing people left and right by pilots pushing on in weather that makes the investigators just shake their heads after the crash. The US Helicopter Safety Team analyzed 10 years of U.S. helicopter fatal accident data and UIMC accounted for 15% of all accidents, one of the three highest aviation occurrence categories. Since 2018 (3 years), the NTSB Preliminary investigations support 15 fatal UIMC crashes with 40 fatalities. Think about that–40 fatalities in three years, many of them passengers who had no say in their fate. Think of the families that have been devastated by the loss of a parent or child, all because a pilot pushed it too far. We’re obviously not learning from our mistakes.



In an inadvertent IMC situation, the airplane community has always relied on variations of the “4 Cs” – Control, Climb, Course & Communicate and many helicopter instructors teach this. In fact, a few years ago the US Helicopter Safety Team published a “Training Fact Sheet” recommending the “Four Cs” in certain situations.


However, when adapted to the world of helicopters, the inherent instability of the helicopter makes getting past the first “C” - Control extremely difficult.


Some instructors recommend a 180˚ turn to exit the clouds. But think about this: a standard rate turn (3°/sec) will take 60 sec, a full minute to turn 180˚. That’s a long time and maintaining control, airspeed and altitude during the turn is going to be very difficult. Increasing the bank angle will lessen the time but control becomes more difficult in a steep turn.


Other instructors teach to immediately initiate a climb – Great, but you still have to get past that first “C” and then what are you supposed to do.


Last, a technique that has gathered more supporters the last few years is to enter an autorotation – the thinking being it’s a very stable form of helicopter flight and the fastest way to exit the clouds.


However, the wide variation in helicopter types, instruments available and, most importantly, the disparity in pilot training, and proficiency make each of these choices debatable, hence the lack of a consensus.


I frequently hear during a private or commercial pilot practical test when posed with an unintended IMC scenario, the applicant declares they’re going to “trust the instruments”. Sounds so simple, so non-threatening, just “trust the instruments” they’ll get you home.

Nothing could be further from the truth. As the HAI video, “56 Seconds to Live”, so clearly shows, in most cases, you’re dead.


FINALLY, the helicopter community is focusing on the most important aspect of unintended flight into instrument conditions – AVOIDANCE! Don’t fly into the damn clouds in the first place!! In the past we’ve just paid lip service to the idea of avoidance. Every article, presentation or instructor lecture I hear begins with the caution “Do your best to avoid punching into the clouds, but if you do…” then they start down the rabbit hole of whatever IMC procedure or technique their pushing. Now we have a specific process for how to avoid unintended IMC. I wish I could take credit for this process but I can’t. It’s developed from the recent work of the US Helicopter Safety Team, HAI’s “56 Seconds to Live” video along with the companion online course, the FAA and input from both Airbus Helicopters and the Robinson Helicopter Company. This “Avoidance Process” needs to be taught at every level of pilot training from private through commercial to recurrent and commercial operator training. Scenario training, simulators and FTDs are perfect tools to teach the process.


There are three stages to the “Avoidance Process”


First The Decision to Take Off:


So many of the IIMC fatal accidents begin with a flawed decision to take off in the first place. “I’ll just take a look”, “I’m familiar with the route”, or “I’ve handled this before” are just a few of the rationalizations pilots use to then take the first step down the path which leads to disaster.

I think the most effective technique to help pilots make good takeoff decisions is to develop a clear, concise set of personal weather minimums for day and, if necessary, night flight. Pilots in the personal/private sector should get with an instructor and based on experience, local weather patterns, etc. determine the minimum weather you are going to fly in – ceiling, visibility and wind. Forget about the cloud clearance and visibility requirements for VFR flight in Part 91 (14 CFR § 91.155) they are only meant for aircraft separation and have nothing to do with keeping you out of the clouds. The thinking is if you’re trying to get home on a Sunday afternoon, the weather’s deteriorating and that get-home-its pull is getting stronger, you’ve already decided your minimum weather, now you need the discipline (a 2 1/2 mile visibility is not 3 or a 500 ft ceiling is not 800 ft) to implement your minimums. Without them many pilots will find some justification to “give it a try”.


Second Enroute Decision Triggers


I used to call these “enroute decision points” but the US Helicopter Safety Team’s Safety Enhancement #127 uses the term “trigger”, which I like much better because it connotates ACTION. The Safety Enhancement defines these as “ A predetermine set of conditions that “trigger” a decision during flight”. Think of them as a CAUTION or WARNING light on the instrument panel.


The three most useful triggers are location, airspeed and altitude.


Location – During the preflight planning process identify a location to use as a decision trigger. It could be a point where the weather is forecasted to deteriorate, a point where a diversion to a nearby airport is easy or, perhaps where terrain becomes more challenging such as mountains, desert or overwater.


Airspeed – A reduction of 30 kts from cruise speed is a good rule of thumb. Whether in your car or in a helicopter what do you instinctively do when the visibility is getting worse and worse? – you slow down. So, in flight, if the visibility decreases to where you have to slow more than 30 kts from cruise – that’s the trigger. Turn around, divert or land!


However, slow no less than Vy – best rate of climb speed. Vy is the bottom of the power required curve, so if the helicopter slows below Vy it moves up the backside of the power required curve, requiring more power not less.


Altitude – I think a minimum altitude of 300 ‘ AGL during the day and 500’ AGL at night works well. However, increasing these numbers is fine. Again, the thinking is if the inflight ceiling is getting lower and lower and you have to descend below 300’ AGL to remain clear – that’s the trigger.



Third “Land the Damn Helicopter”


Kurt Robinson begins every Robinson Safety Course with a discussion about a magazine article written several years ago by Matt Zacaro, former president of HAI, titled “Land the Damn Helicopter”. In the article Matt stated he couldn’t understand why helicopter pilots, flying a machine that can land almost anywhere, don’t take advantage of this unique ability but instead press on in poor weather and it ends up costing them and their passenger’s lives. This article evolved into HAI’s “Land and Live” program which I’d like to add four words to: “or Continue and Die”


I’ve had many occasions in my career where I’ve “landed the damn helicopter”. Once in a field, once in a parking lot and once on the median between the north/south lanes of Interstate 15. I just waited till the weather improved, which one time was a couple of hours - but I “landed and lived”. In fact, just like pilots who use the “I’ve handled this before” thinking to drive on, I’ve “landed and lived” enough times that I don’t think twice about putting the ship down to wait out the weather.


Sure, there are certainly complications to deal with when you “land the damn helicopter”: the police wanting an explanation, upset passengers, perhaps the press asking questions to name a few but look at the alternative – So, “Land and Live”!!...don’t worry about a possible FAA enforcement action – it will not happen.


Rarely do the above mentioned conditions that should trigger a decision instantly appear during a flight. It’s normally a noticeable deterioration. So, as the conditions worsen, look for potential precautionary landing areas, note obstructions or hazards along the route and mentally prepare yourself to “land the damn helicopter”.


Of course there will always be instances where pilots press on and eventually punch into the weather. My advice at this point is to take your hands off the controls, place your palms together underneath your chin, fingers pointed upward because you now have “56 seconds to live”. Better to spend these last precious seconds saying good-by to loved ones or greeting your Maker.


Seriously, what should one do if they inadvertently find themselves IMC? I will not go down that rabbit hole other than to quote Bruce Webb from Airbus Helicopters “We all have a limited mental capacity and this situation will require all of it.”


Tim Tucker

January 2022






Recent Posts

See All

If you could give one piece of advice to a new helicopter pilot, what would it be? I think it’s most important to maintain a very healthy respect, tinged with a bit of fear, for this tremendously vari

When it comes to mentoring and the incredible impact it has on safety in our industry, I feel fortunate to have benefitted, early on in my career, from a structure that heavily relied on a mentoring s