Most encounters with Inadvertent flight into Instrument Meteorological Conditions (IIMC) are unnecessary and avoidable with proper planning. It is no secret that IIMC has claimed the lives of many pilots and passengers throughout the years. As a simulator instructor and check airman for a Part 135 Helicopter Air Ambulance (HAA) company, I spend a good portion of my time training pilots for the possibility of an encounter IIMC. Better training, and increased emphasis on more conservative weather decisions are helping keep those numbers down for now, but I see some recurring patterns that could cause a resurgence of IIMC accidents if left unchecked. One of these trends is lack of proper preflight planning. This post is HAA-centric but the concepts here can apply to many areas of the aviation industry.
“You can’t encounter IIMC while sitting on the couch!” -anonymous
Perhaps the best way to prevent IIMC accidents is to decide not to go when the weather is not good enough. Simple enough, right? It is easy to turn a flight down when a thunderstorm sits over the base, or when fog restricts your ability to see the aircraft on the ramp 100 yards away. But what about those marginal days? Do the minimum ceiling and visibility set forth in 135.609 go far enough to protect us?
Let me make a statement here and see how many feathers I can ruffle. Here goes: 135.609 minimums (800-2, 800-3, etc.) DO NOT provide legal weather to accept most HAA Flights. 135.615 anyone? Isn’t there something in there about the highest obstacle along the proposed route of flight, and having sufficient weather to safely clear that obstacle by 300 feet in the daytime or 500 feet at night? I can already hear someone exclaiming that we don’t have to fly OVER the obstacle. We can fly AROUND it. Absolutely correct! But, there is more to it than simply deciding to go around. Close your eyes and picture a route you frequently fly, making a mental note of terrain and obstacles along the route. What ceiling would you need in order to clear the highest obstacle by 300’ day/500’ night? If you decide to go around, what obstacles will you NOW be flying over, what ceiling do you need to clear THEM by 300’ day/500’ night? Think that through. Go ahead. I’ll wait.
Odds are that the ceiling required is above 800 feet, unless the route you are thinking of is across the Bonneville Salt Flats in uncontrolled (or Class B) airspace. At night, if I have to maintain 500’ clearance from terrain and obstacles, plus 500’ above me for cloud clearance (depending on the airspace), then with NO obstacles I would need at least 1000’ ceiling to be legal. Am I overthinking this? I think it is more likely that most pilots are underthinking when the weather is marginal.
“By the time I’m finished planning this flight, the patient is going to be dead…” -Someone reading this post right now
I am not suggesting that we print pretty blue cards for pilots to hold up to the sky in order to turn down flights when the sky doesn’t match the card. I still believe that HAA pilots help provide an important service to the community, but the weather and flight planning requirements of 135.609 and 135.615 can be an important “speed bump” for pilots when conditions start getting marginal. With a little extra planning, flights can be conducted safely in less than ideal weather.
As Helicopter Air Ambulance pilots, it is our job to provide safe and expedient transport of the sick and injured in the best way possible. When the weather permits us to clear even the highest obstacle along our route of flight by 300’ day/500’ night, then let’s go! When the weather is marginal, let’s slow down a moment and find a better route. When even that doesn’t work, or you find yourself thinking, “This is stupid…I am trying WAY too hard to make this work”, then a helicopter is not the best way to provide transport for that patient.
You can’t encounter IIMC when you are sitting on the couch.