July 1, 2002
By Barry Schiff
It can be one of a single-engine pilot's worst nightmares: total engine failure shortly after takeoff.
According to the National Transportation Safety Board, there were 4,187 accidents attributable to engine failure during a recent five-year period. That's an average of 837 per year or more than two per day. Of these, a significant number were likely the result of a powerplant failure in a single-engine airplane shortly after takeoff.
The truth is that many more engine failures occurred during this period but were not reported because they did not result in damage or injury.
The advice generally available to a pilot who suddenly finds himself powerless can be summarized in one sentence: "If the engine fails after takeoff, land straight ahead; do not turn back to the airport."
This usually is good advice. But there are times when a pilot should return to the airport and not land straight ahead.
NTSB accident records describe in graphic detail the often-fatal stall/spin results of those who have attempted a 180-degree return to the airport from too low an altitude. Many pilots, however, have returned successfully but gone unnoticed because the engine failures did not result in accidents.
Altitude is one of two primary factors that make the difference between success and failure. With sufficient altitude, a turnaround to the airport might be the safest recourse under some conditions, such as when the terrain ahead offers little hope of a survivable forced landing.
If you do not have sufficient altitude, a turnaround should not be attempted. It is wiser to accept a controlled crash into the wind than to risk spinning uncontrollably into oblivion.
But how high is high enough? What is the minimum altitude above which a return to the airport can be executed safely?
This depends on aircraft glide characteristics and the turnaround technique used. For example, should the bank angle be shallow, medium, or steep? To answer these and other questions regarding the controversial turnaround, I enlisted the aid of several flight instructors to obtain flight data for a variety of general aviation singles.
To simulate an engine failure after takeoff, we flew each aircraft in takeoff configuration and at its best-angle-of-climb speed. At a safe altitude, the throttle was retarded, and the pilot did nothing for four seconds, the time it typically takes to recognize an engine failure and initiate action. After this delay, the aircraft was established in a 30-degree banked, gliding turn. At the completion of a 180-degree turn, the sink rate was arrested to simulate a landing flare. Subsequent tests were conducted using 45-, 60-, and 75-degree banked turns, and the net altitude losses were recorded.
According to these findings, the minimum altitude loss (in most cases) results from a steeply banked turn. The altitude loss in a Cessna 172, for example, is 380 feet when a shallow bank is used but only 210 feet when the bank angle is steepened to 75 degrees.
It might seem incongruous that a shallow bank results in more altitude loss than a steep bank. After all, sink rate during a gliding turn increases with bank angle. The explanation involves the element of time. When a Cessna 172 is banked 30 degrees while gliding at 70 knots, the rate of turn is only 9 degrees per second and the time required to execute a 180-degree turn is 20 seconds, which is enough time to lose substantial altitude even though descent rate is nominal.
Conversely, turn rate increases to an astonishing 58 degrees per second during a 75-degree bank, and a one-eighty requires only three seconds, insufficient time to lose substantial altitude even at a high descent rate.
The results seem to favor using a steep bank angle. The problem is that progressively steepened bank angles result in rising stall speeds. During a 30-degree banked turn, stall speed increases only fractionally, from 50 to 53 knots in a Cessna 172L. In a 75-degree banked turn, stall speed increases by a dramatic 97 percent (in all airplanes). It is obvious that steep bank angles must be avoided during low-altitude maneuvering.
Another argument against the steep turn is the difficulty of attempting to arrest a high sink rate near the ground. With the aircraft perilously close to stall, added elevator pressure is required to overcome the airplane's substantial vertical momentum. This aggravates the problem by increasing the probability of an accelerated stall near the ground.
The optimum bank angle, therefore, appears to be a compromise between the altitude-losing effects of a shallow bank and the rising stall speeds associated with steep bank angles. A 45-degree banked turn seems to provide the best results, a moderate turn rate and altitude loss, and only a 19-percent increase in stall speed.
During this investigation, we explored other turn methods: half-spins, wingovers, and skidding turns. In most cases, such maneuvering proved unacceptable and resulted in greater altitude losses and hazards than did coordinated gliding turns.
After completing a 180-degree turn, however, an aircraft is laterally offset from the runway centerline and, therefore, must turn at least 30 degrees more to return to the centerline and another 30 degrees to line up with the runway.
We initially thought that an extra 25 percent of altitude, beyond that lost during the 180-degree turnaround, would be required to return to the runway. But further testing revealed that 50 percent more is required. For example, a Cessna 172L loses 300 feet during a 45-degree banked 180-degree turnaround (including a four-second delay and transitioning from climb to glide), but 450 feet are required to return to the runway under ideal conditions.
Once you determine how much altitude your particular aircraft loses during a 180-degree turn, increase this figure by at least 50 percent to determine the minimum turnaround altitude. By adding this result to airport elevation, you have a target altitude that must be attained before you contemplate a return to the runway.
The second primary factor (altitude being the first) that can determine success or failure is runway length. If the runway is short, an attempt to return from the minimum turnaround altitude is likely to fail because the aircraft will be too far from the runway when it finally reaches its turnaround altitude. It also leaves little room for error (especially because the landing will be downwind). On the other hand, turning around from an appropriate altitude to a 12,000-foot-long runway is a no-brainer. A rule of thumb suggests not even thinking about a turnaround unless two-thirds of the turnaround altitude is achieved before crossing the departure end of the runway.
Although initial climb at the best-angle-of-climb airspeed (V X) results in more altitude over the departure end of the runway than when using the best-rate-of-climb airspeed (V Y), pilots should recognize that an engine failure and delayed action at V X result in a more rapid speed bleed that places the aircraft in greater danger of stalling. Furthermore, the transition from such a nose-high attitude to a gliding attitude requires lowering the nose aggressively, an action that seems to initially fill the windshield with rapidly rising terrain. This can startle even those prepared for such a low-altitude phenomenon. Although a climb at V Y can reduce the likelihood of a return to the runway, the additional airspeed it provides might be more desirable.
A turnaround is risky when departing into strong headwinds because of the possibility of overshoot and the considerable runway length required to dissipate high groundspeeds. Under these conditions, it is more advisable to lower the nose following an engine failure and accept what lies ahead.
Speaking of wind, turn direction should be into the wind to decrease lateral displacement from the runway centerline, which makes it easier to line up for landing. A downwind turn would cause the aircraft to drift farther from the centerline, decreasing the likelihood of a return to the airport.
If the wind is blowing down the runway, turn in whichever direction is most comfortable (left for most pilots).
If you depart from a parallel runway, you probably should turn toward the other parallel and land on it or any other runway that is more convenient. Don't become fixated about landing on the departure runway. If a taxiway or other clear area seems a better choice, use it. Put the airplane on any surface that appears survivable.
If a turnaround results in excessive altitude on final approach, it can be dissipated by S-turning, flap deployment, and slipping. On the other hand, if you're ever so slightly low and are not sure whether the landing gear will clear a fence or destroy it, you can wait until the last second to extend flaps to the takeoff position. This last-ditch effort usually causes a slight ballooning and might be what's needed in a pinch. But since you don't get something for nothing, watch out for an increased sink rate after the fence has been left behind (hopefully intact).
As you begin the landing, do not allow a prolonged flare to eat up valuable real estate. Put the airplane down — firmly if necessary — and stomp on the binders. If obstacles loom ahead, raise the flaps to kill lift, and consider ground looping. Do whatever is necessary to prevent the nose from burrowing into an immovable object.
Tradition claims that landing is more hazardous than takeoff. Landing, we are taught, requires more finesse and expertise and has been compared to threading a needle. A takeoff, on the other hand, frequently is compared in simplicity to withdrawing the thread. But with respect to engine reliability, the takeoff is riskier. This is when the powerplant is first put to the test and when we learn if everything is going to hold together. There's less reason to be concerned about powerplant integrity during an approach because you have been assured of its reliability while en route.
Once you acknowledge the risk of an engine failure during takeoff and initial climb, the least you can do is prepare for the possibility by knowing the minimum safe turnaround altitude for your aircraft. Having a target altitude provides a psychological advantage at a time when you are burdened with an assortment of departure chores and are least prepared for engine failure. With a target altitude in mind, you are not forced to make an immediate turn/no-turn decision. That determination was made earlier. If you are below target altitude, you know not to turn. Above this altitude, you can turn with more assurance of success and, as a result, perform more calmly and efficiently than turning without knowing anything about the probability of your survival. An engine failure after takeoff is extremely frightening and can reduce mental sharpness to pudding with the snap of a connecting rod. Armed with a target altitude, you're ahead of the game.
When conditions suggest using the turnaround maneuver, you can ill afford the luxury of guesswork. You must know that you can make it safely or not attempt the turn. Once committed to a course reversal, you must perform with cool, calculated precision, turning at the desired bank angle while closely maintaining the best-glide speed. Large variations in pilot performance can drastically erode valuable altitude.
Keep your head in the cockpit and stay on instruments while establishing the gliding turn. This helps to ensure proper entry. Neck-craning to locate the runway doesn't do any good until some of the turn has been completed.
On the other hand, be sure to look at the runway before half of the turn is complete to determine if a return to the airport appears likely. If not, reverse the turn and land into the wind.
Resist the temptation to steepen the bank and/or reduce airspeed during the turn. (Reducing speed to within 5 percent of stall actually reduces altitude lost per degree of turn but cannot be recommended in good conscience.)
When a pilot follows a calculated course of action, his mind is less encumbered with fear, possibly offering him time to attempt a restart. Perhaps the problem can be resolved by switching fuel tanks or turning on a fuel pump. But trying to analyze an engine failure while maneuvering requires a clear head. Preparation helps to make this possible.
As you read this, you no doubt will consider the numerous and generally valid arguments against a turnaround after takeoff. Consider also, however, the arguments favoring a return. There are many, including the most obvious: the availability of a long, smooth landing surface. Also, crash-and-rescue efforts generally are timelier on an airport than off.
Far superior to the turnaround maneuver is avoiding engine failure in the first place. Since fuel starvation or exhaustion is more common than structural or mechanical failure, a pilot should modify his preflight preparations to include selecting the fullest fuel tank prior to engine start. The fuel valve should not be moved again until the aircraft is in cruise flight. Repositioning the selector valve during runup might not allow sufficient time to determine that the engine is operating on an unrestricted flow of fuel. There might be only enough fuel in the lines for the airplane to become airborne before sudden silence stuns the pilot into quiet, unnerving reality.
By selecting the desired fuel tank before engine start, you can test fuel-flow integrity during engine start, normal taxi, and runup. This better ensures that fuel is indeed flowing freely from tank to engine.
As the throttle is advanced at the beginning of the takeoff roll, listen carefully for unusual roughness, scan the gauges judiciously, and be prepared for the possibility of an abort.
Initial climb should be made as steeply as is practical and safe. Relatively flat climbs reduce the likelihood of a return to the airport should an engine failure occur even when above the turnaround altitude.
Many pilots habitually retard the throttle almost immediately after liftoff. Avoid this unless required by local noise-abatement procedures. If the engine is operating normally at maximum power, leave it that way and use it to maintain maximum climb performance. Do not reduce power until safely above the minimum turnaround altitude or until a relatively safe off-airport landing could be made.
Once airborne, begin looking for a place to land. It might be difficult to shift mental gears so abruptly and think about a forced landing during the early moments of flight, but this simple procedure can pay handsome dividends. If a landing area has been selected, the shock of an engine failure at low altitude won't be quite so traumatic. Suitable landing sites aren't always ahead or behind; a better choice might be off to the side.
No one can advise a pilot exactly what to do when his only engine fails after takeoff. Each of us must determine his own course of action. This controversial discussion is not intended to encourage a return to the airport. Rather, its purpose is only to provide additional and enlightening information resulting from an exhaustive investigation of the options. Hopefully this will be of value to those who acknowledge the risk assumed during every takeoff.
Visit the author's Web site ( www.barryschiff.com).
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