On Christmas Eve, five people were killed when a pilot attempted taking off in foggy conditions. While the takeoff was legal under Part 91, had this been an airline flight, the plane probably never would have left the ground. Here's why.

The Accident Made National News

On Christmas Eve morning, a pilot attempted takeoff from the Bartow Municipal Airport, just east of Tampa in a twin-engine Cessna 340. He and his passengers were headed on a holiday day trip to the Florida Keys, and planned to return later in the day.

According to an airport employee working that morning, dense fog limited visibility at the field. The METAR observation at the approximate time of the accident confirms it:

METAR KBOW 241215Z AUTO 00000KT M1/4SM FG OVC003 12/ A3018 RMK AO2

As the airport employee recorded fog rolling over the airport, their cell phone captured noise from both the takeoff roll and crash. The fog was so dense that the airplane was never in sight of the camera.

So what went wrong here? Why did this pilot choose to takeoff in such poor conditions?

It will be awhile before the NTSB releases a preliminary report on the accident, but it's very likely that the fog played a significant role in the accident.

Under Part 91, pilot's typically don't have takeoff minimums. So, does that mean you can legally takeoff with zero visibility? Legally-speaking, some say yes and some say no. Let's dig a little deeper...

Standard Takeoff Minimums

Unless otherwise authorized by the FAA, for Part 121/135 operators and sometimes Part 91 operators, standard takeoff minimums under IFR are the following:

• 1 And 2 Engines: 1 Statute Mile Visibility
• 3 Or More Engines: 1/2 Statute Mile Visibility
• Helicopters: 1/2 Statute Mile Visibility

Unless carrier-specific, FAA approved Operating Specifications (Op Specs) allow for otherwise, Part 121 and Part 135 operators must comply with these standard takeoff minimums. Air Carrier Op Specs will likely state that the visibility must be a station-reported value or measured in terms of runway-visual-range (RVR).

But in most cases, these IFR takeoff minimums do not apply to pilots flying under Part 91, EXCEPT if the pilot is assigned and accepts a published departure procedure that includes takeoff minimums.

For example, if ATC issues you a Standard Instrument Departure (SID) procedure and you accept it, you must comply with the charted takeoff minimums. If the SID requires "standard" minimums, reference FAR 91.175. For anything else, you're obligated to follow what's published on the procedure.

This holds true for ODPs too. If you accept any instrument departure procedure, you must follow the required minimums for the procedure, even under Part 91.

Remember, if you can't meet the takeoff minimums or climb requirements, you have the option to decline the clearance and see what other options ATC has for you.

At large airports, you might be put on a "hold for release" for quite awhile, because you'll interfere with standard traffic flow. In reality, there are only a few instances when you'd choose to decline a departure procedure clearance.

Non-Standard Takeoff Minimums

Many airports have runway-specific, non-standard takeoff minimums published. They usually correspond with obstacle departure procedures. If you see a "T" within a black, upside down triangle on an FAA approach plate, the airport has non-standard takeoff minimums. You can also find a list of these airports at the beginning of the FAA's chart packet. If you use ForeFlight, look under the "Procedures - Departure" tab on the airport description page and click on "Takeoff Minimums."

Non-standard minimums are published when there are obstacle departure procedures to ensure you maintain safe clearance. For example, at the Mercer County Regional Airport (KHZE) in Hazen, ND, you have two options when departing Runway 32:

• 1) Depart from Runway 32 using standard minimums and a mandatory 215 foot per nautical mile climb to 2,700 feet.
• 2) Depart from Runway 32 when there are 900 foot ceilings and 3 statute miles of visibility for a climb in visual conditions.

While there's no obstacle note to explain the reason for this ODP, a quick look at a sectional map reveals that terrain rises more than 600 feet above airport elevation, beginning just two miles from the departure end of Runway 32. This is why the departure procedure has a climb gradient requirement or a minimum ceiling height to ensure you'll safely avoid terrain.

Do You Need A Takeoff Alternate?

IFR takeoff alternates are required when weather conditions are above takeoff minimums, but below landing minimums for the departure runway or airport. Takeoff alternates aren't required under Part 91, and usually only apply to Part 135 or Part 121 Air Carriers.

But while they aren't required for you under Part 91, creating your own takeoff alternate is always a good idea. If you decided to go, and if the ceiling and visibility on departure are lower than the instrument approach minimums, have an alternate airport nearby in mind.

If The Weather Is That Bad, Do You Really Need To Go?

Taking off in extremely low visibility increases your risk of a loss of directional control.

The pilot in this accident had little to no visibility during takeoff and immediately after rotation. While we don't know yet if fog was the only factor, or if there was a malfunction that triggered the event, poor visibility compounded the situation.

While takeoff minimums aren't prescribed for most flights under Part 91, it's always a good idea to set some personal standards. A good rule-of-thumb is to use the instrument approach minimums for the runway in use as your takeoff minimums. That way, you'll have plenty of lateral visibility down the runway, as well as ceilings high enough to return to the field if something goes wrong.