Step -2: There is nowhere in the world you need to be badly enough to go VFR into IMC. If you're under enough pressure to get somewhere on time that you'd even consider going VFR into IMC, don't fly GA to get there!
Step -1: Exercise good Aeronautical Decision-Making (ADM) and do thorough preflight planning. Short of an unforecast overcast cloud deck appearing out of nowhere beneath you, you shouldn't ever find yourself in this position.
Step 0: The moment you think you might be forced to go VFR into IMC, you are in an emergency situation. Don't delay- declare an emergency to ATC and ask for help finding your way to a break in the clouds.
But suppose you are out of options and you need to descend through clouds. There are some major risks here:
- Mid-air collision
- Controlled Flight Into Terrain (CFIT)
- Other Loss of Control In-flight (LOC-I)
Note: the next few steps are general advice. As usual, this may differ based on type, and you should follow your POH's instructions for an emergency descent through clouds if they differ.
Step 1: Plan your descent.
There's not much you can do about a midair collision. Declare an emergency to ATC (if you ignored the previous step and you haven't declared already) and have them clear the space for you. If you can't get a hold of ATC, do your best to avoid areas with heavy IFR traffic.
Avoiding CFIT mainly means picking a course through the clouds that has the most space between the cloud ceilings and the ground. ATC can help with this, and you may have some cockpit technology to help as well. If at all possible, you don't want to turn at all in the clouds, so try to find a straight course that will let you descend all the way through the cloud deck without turning.
If you will be relying on a compass to keep on course, an easterly or westerly heading is better to reduce compass errors. Of course, terrain considerations take precedence.
Step 2: set up the plane to fly itself as much as possible.
Point the plane on the course you want to descend through the clouds. Turn on full carb heat, if applicable. Set trim and power so the plane will fly at a moderate airspeed and descent rate with hands off the controls. Lock the throttle in place. The Cessna 152 POH recommends 70 knots and 500 to 800 fpm, but this will depend on the type. You don't want to be in slow flight, but any excess airspeed over that isn't doing you any good.
Once you have set up for this hands-off descent, put the ailerons in a neutral position and don't touch the stick again! If you don't touch the elevator, you can't stall or spin. It is much easier to avoid overcontrolling the plane if you avoid touching the ailerons. If you have an autopilot or wing leveler, use it!
In an ideal world, you would completely stop manipulating the controls entirely. Most planes will continue to fly themselves with no pilot input, and it is common for a disoriented pilot to fly themselves into a spiral dive. Unfortunately, most planes will eventually fly themselves into a spiral dive even with hands off. Which leads us to Step 3.
Step 3: Don't turn!
If you're not turning, you're not in a spiral dive. Watch the turn coordinator (if equipped) and the HI/HSI/compass. The most important thing in the world for you right now is that you are not turning. Make small, cautious adjustments to the rudder pedals as necessary to show wings level on the turn coordinator. Stop any trends that you see on the HI/HSI/compass. If you are using the compass, remember that there may be significant errors, especially on a northerly or southerly heading.
As long as you are not turning, you are not spiraling. As long as you don't touch the stick, you won't stall or spin. As long as you don't make abrupt or large inputs to the rudder, you hopefully should maintain control.
Coordination is not a concern. It's much better to be in a slight sideslip and not turning than it is to be perfectly coordinated and turning.
It's very important not to overcorrect. With incorrect or too aggressive inputs, you can induce a spiral dive within seconds. Most airplanes will take much longer to enter a spiral on their own accord.
You may enter a spiral dive despite your best efforts. Be ready to recover when you break out. Remember that pulling back is the one sure-fire way to die.
Step 4: When you break out, recover from the spiral dive if necessary. Don't pull the stick. Cut the throttle and level the wings. The nose will come up of its own accord as it seeks the trimmed airspeed. Don't pull. If the dive has developed and you are at high airspeeds, you may need to push to unload the wings.
Once you are in a usual attitude, resume normal VFR flight. Land as soon as possible. If the ceilings are low, you should seriously consider an off-airport landing rather than scud running in search of an airport.
Step 5: Learn from the experience.
If you've made it this far, congratulations! You've survived a VFR into IMC event and avoided becoming a statistic. Debrief. Figure out what went wrong and how to keep it from happening again. Fill out a NASA ASRS report, which will hopefully help other pilots from being in a similar situation and can protect you from certificate action if the FAA decides to go after you.