The Importance Of IMC In Modern Aviation

‍IMC Aviation and VMC Aviation refer to meteorological flight conditions. IFR and VFR, conversely, refer to the rules to follow in those respective conditions.

Flying in Instrument Meteorological Conditions where pilots have inadequate separation from clouds and poor visibility is considered IMC Aviation. Federal regs require these flights to operate under instrument flight rules (IFR,) requiring the plane and pilot to be certified accordingly.

As a CFII and a corporate pilot, I have been a part of the flying community for more than a dozen years. Having logged significant actual and simulated instrument time, I know how important it is to have an IFR rating and to keep it current and remain proficient.

‍Proficiency In IFR Environment

Currency and proficiency are two different things when it comes to a pilot’s IFR rating. Being current means that you satisfy at least the minimum requirements set by Section 57 of Part 61 of the CFR.

It states, among other requirements, that once you get your IFR rating, you need to conduct six approaches (either in actual IMC or under the hood), a hold, intercept and track an en route course in the preceding six months before your intended flight.

If your currency lapses, however, you will have to undergo an IPC, or Instrument Proficiency Check, to become current once more and legal to fly as Pilot in Command in IMC.

Being IFR proficient is about being able to handle the workload of the Pilot in Command during instrument meteorological conditions. With the increased workload in the terminal area during approaches, and departures, added to the increased complexity of en route procedures, and the possible lack of visual references outside, the increased workload can and does overwhelm a pilot who is not proficient.

The bare minimums required for currency do not make a proficient pilot. This becomes evident when a current but not proficient pilot inadvertently experiences the rigors of unintended IMC in aviation.

What is IMC?

Remember, there are three conditions of flight. VMC, Marginal VMC, and IMC. They are defined by the Code of Federal Regulations. To be in VMC, or Visual Meteorological Conditions, an aircraft has to be able to stay clear of clouds and maintain visuals with the terrain and other aircraft.

Anything other than this and the pilot is in IMC. Marginal VMC means that the clearance and distances are approaching that of IMC and should be treated as such.

IMC technically differs in specifications in different airspace except for Class A airspace where there is no need for distinction since all flights are conducted under IFR.

In Class B airspace anything less than the visibility of three statute miles and the inability to keep clear of clouds is considered IMC aviation.

In Class C, D, and E airspace, IMC below ten thousand feet above mean sea level is defined as anything less than 5-kilometer visibility, unable to keep below the ceiling by at least a thousand feet, or unable to stay horizontally clear of clouds by 1500 meters (approximately 5000 ft).

This increases above ten thousand feet AMSL to 8-kilometer visibility.

In Class G airspace, IMC happens at any point when daytime visibility drops below one mile and night visibility drops below 3 miles. As for cloud avoidance, in the day anytime you are unable to keep clear of clouds it is considered IMC.

At night, that standard increases a little and you would need to maintain 1000 feet above the cloud, five hundred below, and two thousand feet horizontally. If you can't, that’s IMC.

What are the Requirements to Fly in IMC?

IMC requires that an IFR flight plan has been filed for that flight. To file a flight plan the Pilot in Command must be rated and current. The PIC has to also determine that the aircraft has the minimum equipment list (MEL) as listed in 14 CFR 125.205 to deem the aircraft fit for IFR flight. The MEL is as follows:

• At least one VSI - vertical speed indicator
• A temperature indicator
• A heated pitot tube
• A vacuum indicator
• An alternate static port
• Generators to supply all required instruments and equipment
• A sensitive altimeter
• Cockpit lights to make required instruments and switches readable

What is Inadvertent IMC?

Inadvertent IFR, IIFR, or Inadvertent IMC is when an aircraft operating under VFR faces deteriorating weather conditions and enters lower than VFR conditions or marginal VFR conditions.

This entry into IMC is dangerous for pilots who are not instrument rated, current, or proficient. It can be disorienting, especially when one is not prepared for it.

Inadvertent IMC can also be when the pilot loses the horizon and/or loses sight of the ground. Inadvertent IMC is a major cause of pilot disorientation during flight and controlled flight into terrain.

The best way to avoid Inadvertent IMC is to get thorough weather briefings before every flight, and once more during the en route phase of the flight if more than two or three hours have elapsed since the last briefing.

But mistakes can still occur. Briefers have been known to get it wrong, and if you flout the regs by entering into IMC conditions, blaming the briefer, even if there is a recording, is not a valid defense when charged with pilot deviation.

The better way to prepare for IIFR is to get instrument rated, and remain current and proficient, allowing you to fly within the IFR ecosystem and reducing the disorienting series of events that transpire when caught in MVMC or IMC.

The Consequence of Inadvertent IMC

Inadvertent IMC can result in catastrophe. It is, primarily, a General Aviation phenomenon as most commercial flights are conducted under the protection of an IFR flight plan and require pilots to be IFR proficient.

In 2012 there were 50 accidents related to adverse weather. 46% of those accidents involved flights that proceeded into IMC during a VFR flight. 95% of those, resulted in fatalities.

As a proficient instrument-rated commercial pilot, I can personally attest to one added dimension to inadvertent IMC. The sudden increase in workload and the time constraints to perform it can cause significant distraction. Not to mention that it can get turbulent in IMC.

Do not be confused, this is an emergency and warrants a Mayday declaration. The disorientation pilots may feel in IMC is not the only issue to be concerned with. There is the increased workload, and then there is the fear that telling a controller that you have just entered IMC could lead to an investigation and the eventual loss of your ticket.

How to Survive Inadvertent IMC?

Your first task is to make sure that your wings are level. If you no longer have any visual reference and you only have the wherewithal to do only one thing, just keep the little plane in the attitude indicator straight and level.

Now, catch your breath and do nothing else. Once you have that, alternate your focus between the AI and the outside. You’re now keeping an eye for any semblance of clear skies. Still keep that scan going between the AI.

Now add one more task. If you stumbled into IMC, there is a good chance that there is still VMC behind you. Raise the power a little and trim the aircraft for a slight ascent. 200-300 feet per minute would be fine. You want to gain some altitude to avoid terrain.

Now shift your gaze to the turn and bank coordinator and place your aircraft in a standard rate turn. Your target heading is 180 degrees from where you were originally headed.

Once you have reached your target heading. It's time to radio for help. Dial in 121.5 and declare an emergency.

But to avoid all this, get an IFR rating and keep current and proficient. Get an instructor on cloudy days and get as much actual IMC flight time as you can get.

In addition to the IFR rating, practice recovery from unusual attitudes with your instructor. Learn how to trust your instruments and not the seat of your pants.

How to Obtain an IFR Rating?

You must hold at least a valid Private Pilot License before you can take the instrument rating checkride. With a PPL, there are two paths toward obtaining your rating. One is a more relaxed route and the other is a little more rigorous.

The first is listed under Part 61 of the CFR. And the other is listed in Part 141. Both result in an instrument rating but the latter is conducted under more stringent and disciplined conditions while the former is relaxed and designed for those taking the rating on a part-time basis.

Candidates are required to get ground training as well as flight experience before being signed off to take the checkride.