The Big Ground Theory And The ACA Defense

A Bonanza’s forward cabin door pops open as it takes off into blue skies, and in his rush to return the aircraft to the ground and secure the door, the pilot forgets to extend the gear. A three-man airline crew flies an airliner into terrain while troubleshooting a burned-out light bulb in clear weather. The pilot of a light twin detects an instrument failure during descent and slips below glideslope on approach.

Many aircraft accidents — from “minor” incidents to tragic fatal crashes — happen when the pilot is distracted when flying close to the ground. Most of the time the airplane is perfectly flyable, and taking just a little more time to think before acting may well have turned a horrible mishap into simply one of those “there I was…” stories for the next hangar flying session. Unfortunately, most of the time, the mindset fostered during cruise does not translate well to close-proximity operations.

Very few aircraft abnormalities are true emergencies. An engine failure or a fire in flight certainly warrants immediate attention. Anything less than a catastrophe, however, gives you time to act. The World War II instructors had a saying for how you should respond to an aircraft emergency — the first thing you should do, they said, is to wind the clock.

Inside Information

    • : Airplanes of the period usually had an “

eight day mechanical clock

    ” on the instrument panel. When wound, (as the name suggests) it would run for about eight days.

What It Means: It’s important to take a moment to evaluate the nature of the emergency, and to choose the correct response. It’s vital you don’t let the surprise of an unusual event distract you from your primary mission of flying the airplane. Have an engine problem? What’s your airspeed attitude and altitude? Annunciator light flashing in your face? AIRSPEED, ATTITUDE AND ALTITUDE. Unusual noise got your attention? AIRSPEED, ATTITUDE AND ALTITUDE. Passenger sick in the back seat? AIRSPEED, ATTITUDE AND ALTITUDE. Don’t interpret this as meaning you shouldn’t act promptly to the specific unusual situation during an aircraft emergency, but there are priorities.

Insider’s Tip

    • : The first step in any emergency action is to assure your airspeed, attitude and altitude to the best of your ability — noting the aircraft’s inability to maintain each or any one of those things and your need to recheck them soon and frequently. The next step should be to assess the actual problem. It’s more important to be


    • than to be



Some people think the “big sky theory” explains why there are so many airplanes but so few midair collisions — there’s just so much sky to fly around in that the odds of two airplanes being in the same place at the same time are remote. Whether or not that’s true, there’s no debating what I call the big ground theory — if you’re not watching what you’re doing, eventually, you WILL run into the ground. Most aircraft accidents happen either on takeoff or on landing, because there’s something there to crash into. Any airborne situation (that doesn’t result in total loss of control) will eventually move into the landing phase.

To avoid running into the ground, especially if abnormal indications or an emergency distracts you, observe what I call “Altitude Critical Areas.” An ALTITUDE CRITICAL AREA (ACA) is a pilot-defined block of airspace where the airplane is close to the ground, or close to leveling off from a climb or a descent. For most privately flown airplanes, an ACA should be defined as airspace:

  • Always: from the surface to 1000 feet above ground level (AGL);
  • Climb: from 1000 feet below level-off cruise altitude and until trimmed at that altitude — whether it’s an intermediate level-off or the final cruising altitude;
  • Descent: from 1000 feet above level-off altitude until trimmed level at that altitude, again whether it’s an intermediate level-off or some new, “final” cruising altitude;
  • IFR: from 1000 feet above “final approach course inbound” of an instrument approach and until the approach is complete; and
  • VFR: from 1000 feet above pattern altitude and until the landing is complete.


    1. Limit your activities to immediate flight-critical tasks. Do nothing but fly the plane — defer nonessential duties until you’re no longer in an ACA.Do not
        listen to ATIS, do not brief for an approach, do not re-tune the Nav radios, or hand that bag of cookies to the kids in the back seat.
    2. Evoke the “sterile cockpit rule.” Airlines have a “sterile cockpit rule,” which among other things limits nonessential conversations when in what we’re calling an ACA. We can learn from the pros. Ask your passengers to limit conversation when you line up for takeoff until you tell them you’re passing through 1000 AGL. Use the pilot isolation switch on the intercom if you have to. REMEMBER that pointing out other air traffic or abnormal aircraft indications is always appropriate, even in an ACA.Do not
        talk about your latest fishing trip while turning short final. Don’t be calling UNICOM to arrange a car rental as you’re lining up on the instrument approach.
    3. Moderate your vertical speed. Except on takeoff, landing or in unusual situations, adjust your rate of climb or descent to 500 feet per minute (if the airplane can sustain that rate) when in an ACA — the better to make the transition to level flight, and to avoid “altitude busts.”Do not
        execute maneuvers that exceed 30 degrees of bank or ten degrees of pitch.


    1. Get out of the ACA. Problem on takeoff? Climb to greater than 1000 feet AGL before you troubleshoot. Faced with a distraction? Delay dealing with it if you’re close to the ground or nearing a level-off altitude. System failure during a visual or instrument approach? Break off the landing; go around, climb out of the ACA, then tackle the challenge.
    2. Always use your best judgment. There may be rare situations when it’s safer to continue the approach or make an immediate return to the airport, but if you can safely get out of the ACA, do it.


    1. Do NOT enter an Altitude Critical Area until you’ve addressed the problem.
    2. Enter the area only when you can concentrate fully on flying the airplane. Landing gear won’t go down? Use the emergency extension procedure before entering the ACA. Instrument problem? Identify the failure and transition to back-ups or partial-panel flight before tackling an altitude change. Radios not set up or airplane not fully configured for takeoff or checklist incomplete? Decline the “immediate departure” clearance or resist the urge to make it out ahead of the slow trainer on long final, and get set up properly.

BOTTOM LINE: Very few events are so critical that you don’t have time to deal with them properly. Yet, many accidents result when the pilot doesn’t take the time to evaluate abnormal indications. “Wind the clock,” and establish “Altitude Critical Area” habits as part of your preflight planning. That will prepare you to deal with those “little things” that can get you killed.

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