IFR Clearances

What You (Mostly Don't) Get with One

by Crista V. Worthy

After enjoying your hundred-dollar hamburger, it’s time to fly home, but the weather is tanking, so you’re sitting in your airplane, copying your IFR clearance. Aside from permission to fly through IMC in controlled airspace, does ATC give you further services along with that IFR clearance? How about weather avoidance? Terrain avoidance? Traffic separation from VFR aircraft? From others in the IFR system? Actually, once ATC issues you an IFR clearance, the only other service they are required to provide you is separation from other IFR aircraft.

Your first surprise may come even before you take off. Are there any man-made obstructions or terrain around your departure airport? If you’re cleared via a SID, you’ll have obstacle clearance so long as you fly it. If your departure airport doesn’t have a SID, it’s up to you to find and fly the proper ODP so you don’t hit anything. Make sure you can meet the required climb gradient. If there aren’t any ODPs, you can sometimes roll your own by climbing in circles over the airport until you’re clear of surrounding terrain. Two words: VFR charts. Don’t leave home without them; they show terrain that IFR charts don’t. Even though ATC may issue a heading to fly, you’re not assured of obstacle clearance until you’re on a published route or procedure, or are receiving guidance in the form of radar vectors. Check your clearance; if that initial heading sends you toward the rocks, ask for the ODP or an amended heading. Even the phrase “radar contact” doesn’t mean ATC is assuming responsibility for obstacle avoidance; they only do that when they give you a vector, so plan your departures as carefully as your approaches.

Think ATC is going to tell you not to fly into a building cumulus cloud? Think again. We launched into clouds with reported tops of 6,000 feet. At 10,000 feet, we still hadn’t punched out, it was bumpy, and my husband complained that ATC shouldn’t have let us fly into this. Actually, that’s not their job; it’s the pilot’s. After famed military pilot Scott Crossfield’s Cessna 210 broke up in a thunderstorm, however, the NTSB did accord a small portion of the blame with ATC. They cited pilot error for flying into a severe thunderstorm, but the tapes also revealed that the controller had plenty of time and could have issued a warning, which he didn’t. Still, it’s your life on the line, so don’t ever assume ATC is babysitting a weather scope to protect you. Warning you about weather is pretty far down the priority list.

Yes, traffic separation is ATC’s primary job, but that’s IFR traffic only. Anything else falls into the category of “additional services” provided on a workload-available basis. That includes telling you about any VFR traffic nearby, which, if you’re in IMC, you cannot see. Hence the cloud distance requirements for VFR aircraft. The assumption is that if you break out of a cloud, you’ll have 2,000 feet to see and avoid a VFR aircraft flying by the cloud. That’s about 10 seconds at 150 knots. The necessary IFR traffic separation can sometimes leave you on the ground when you’re trying to launch IFR. Los Angeles International (LAX) is less than 3 nm from Santa Monica Airport (SMO). When the weather tanks at SMO, it’s not unusual to wait a long time for a launch window, because ATC has to keep a 5 nm separation between IFR aircraft. The big jets departing LAX seem like they’re getting priority because the airlines’ dispatchers filed their IFR flight plans hours in advance; it’s first come, first served. If you are able to take off VFR, no separation services are needed, so off you go. One caveat though: if you can depart VFR but know you’re going to need an IFR clearance soon, don’t count on getting immediate attention for a pop-up. You may run out of clear sky before ATC gets you your clearance. This trap has led to plenty of fatalities as pilots scramble to deal with a situation they hadn’t anticipated.

So your IFR clearance doesn’t guarantee separation from VFR aircraft. Of course if you are in IMC, you’re probably not going to hit a VFR aircraft. You haven’t flown through IMC without a clearance, have you? Technically, you can fly in IMC without a clearance in Class G airspace, because it’s not controlled. Controlled airspace simply means you need a clearance to fly in the clouds. Class G airspace is uncontrolled, so it’s not illegal to fly in the clouds. Legal and wise aren’t always the same, of course.

There are many times when flying IFR will force you to fly higher than you might want because of the MEA. For example, the MEA along your proposed route may be above the freezing level, or above your aircraft’s safe performance ability. If you can make your flight VFR at a lower altitude, that might be safer than flirting with icing or a lack of power.

Ready to descend for landing? If IFR, you cannot initiate a descent without ATC permission, but they may hold you high for traffic separation and then give you a slam-dunk approach. If you know you can maintain VFR to the runway, you may be better off canceling. Other times, you may be flying an IFR approach in VMC and find that the approach takes you into some near-by clouds. If you had been VFR, you could have just steered around them.

Finally, if you do choose to go VFR, get flight following. It doesn’t guarantee obstruction, weather, or traffic separation either, but controllers will call out all of the above most of the time when they can. “Workload permitting” doesn’t mean they don’t want you talking to them; they prefer it, because they know who you are and that helps when they call you out to other traffic. Plus if you have a question or emergency, you’re already in radio contact.