Maneuvering Flight

Avoiding Maneuvering Flight Accidents

Background

maneuvering flight accident NH 2005
Maneuvering flight accident in New Hampshire 2005

It is hardly news that pilots and passengers are killed because of "stall/spin" accidents. Since I learned to fly in the 1960s instructors and aviation safety organizations including the FAA have been harping on the subject, apparently to many deaf ears. Another no-no of classic fame is "buzzing" or otherwise showing off in an airplane. Nobody will admit to thinking that such ostentatious displays are smart, but we still have a significant number of these accidents each year.

Any accident that results from maneuvering the airplane, whether part of the normal flight routine or not, is categorized as a "maneuvering flight" accident. This includes normal traffic pattern operations such as turning from base to final. It includes the various maneuvers we do while training for a certificate or rating. It also includes "buzzing" accidents.

The 2010 Nall Report (most recent data available as of August 2011, covers accidents occurring in 2009) states that more fatal accidents occur in maneuvering flight than any other pilot-related category. for the period studied, there were sixty-seven maneuvering flight accidents, thirty-nine of them were fatal. That provides a lethality index of 58%. That means that if a maneuvering flight accident occurs, there is a better than one in two chance that somebody will die.

Two Kinds of Maneuvering Flight Accidents

As one reads through the NTSB reports on the considerable number of maneuvering flight accidents, a clear divide emerges. Most of the crashes arise out of normal operations. Then there is the other side of the divide where the accidents are the result of buzzing or some other reckless act.

Our Purpose and Path

Our purpose here is to help the reader avoid the maneuvering flight accident. Since our purpose is not primary flight instruction, we will only briefly review some of the aerodynamics involved. Mainly, we will examine actual accidents, try to learn how the pilot got into the particular accident situation, and how that particular scenario might be avoided by other pilots.

Since pilots who are likely to buzz the neighbors' house or perform a roll on final approach are probably not spending their time reading safety articles such as this one, we will only look at one such crash and concentrate on several of the accidents that have occurred during normal operations.

Basics Review

Airplanes need more than just airspeed to fly. They need smooth airflow over the wing. The aerodynamic stall occurs when this smooth airflow is disrupted. The disruption always is the result of exceeding the critical angle of attack. Remember that the angle of attack is the angle between the relative wind and the chord line of the wing.




	The graphics above and to the left depict the concepts of chord line, relative wind, angle of attack, and critical angle of attack.

Remember that an airplane can be stalled at an airspeed well above the published stalling speed. If the airplane is being subjected to higher than normal 1g forces, the stalling speed is increased. Turning, pitching up, or pulling out of a descent are all things that will increase the stalling speed. Recall that at normal cruise, the airplane is subjected to 1g or a load factor equal to 1. Any maneuver, no matter how slight that forces the pilot down into the seat causes the load factor to increase. In a 60° bank, the load factor is 2. The stalling speed increases with the square root of the load factor. The square root of 2 is about 1.4 so in a 60° bank the stalling speed is 40% greater than in normal cruise flight. But even lesser bank angles will produce higher than normal stalling speeds. Couple that fact with reduced airspeed while in the traffic pattern and the possibility of a gust, and things can turn sour pretty fast.

Now remember that a stalled airplane, even a partially stalled one, is a candidate for a spin. A spin is an aggravated stall resulting in autorotation. another word for "aggravated" is "uncoordinated". If the airplane is stalled with the inclinometer ball out of the center, the stage is set for a spin. If anyone believes that their airplane is docile and that this is not likely to happen to them, they're literally dead wrong. Once it happens at low altitude such as in the traffic pattern it is almost certainly unrecoverable.

A final consideration of all this is the structural limits of the airplane. Without going into all the numbers associated with limit load factors and ultimate load factors, it is possible to overstress the airplane and disassemble it in flight. The theory holds that if the airplane is flying at a speed less than the published maneuvering speed (Va) it will stall before failing structurally. Of course, a stall is preferable to structural failure, but can have the same result at low altitude. And, the notion that structural failure won't occur at a speed below maneuvering speed is rather iffy. Maneuvering speed is affected by the airplane weight. The maneuvering speed actually decreases with decreased weight as counter-intuitive as that may seem. Also, is a thirty year old airplane or one that has been subjected to the rigors of flight training for many hours as strong as it was when it was built? What toll has that corrosion and its associated treatment taken on the structural integrity of the airframe?

Accident Analysis - Reckless Operation

Bellanca Cruisair (representative photo - not the actual accident airplane)

The following example shows how an attempt at an ostentatious display can end in disaster. It occurred in May 2001 at Scott City, Kansas.

A witness stated, "[Another witness] and I were at the airport. We helped [the pilot] get his airplane out of the west hanger. He said he was going to fly around the patch. He stated he would do a roll on final approach to runway 17. We watched him take off and flew around the pattern. On final approach he started to roll the plane. He rolled it about 3/4 the way around and then was diving toward the ground and never could pull it up. We saw a fire ball when it hit."

Official NTSB photo of the accident site. Note that only a burn mark remains on the ground.

The NTSB lists the probable cause of this accident is as follows:

The low level roll maneuver the pilot performed on final to runway 17 and his not maintaining clearance from terrain during the maneuver.

It almost seems silly to include the traditional thoughts on how an accident such as this could have been prevented. FARs clearly prohibit aerobatic maneuvers at such a low altitude. Common sense should do the same.

Accident Analysis - In flight Breakup

Piper Saratoga (not the actual accident aircraft)

This example shows how even a proficient pilot, or pair of them in this case, can lose control of a situation and induce catastrophic structural failure. The accident happened in Georgia on Sept. 21, 2004.

According to the official NTSB report, the purpose of the flight was for one flight instructor to check out another instructor in the Piper Saratoga, PA-32R-301. The flight departed at about 1915 local time and headed west into the setting sun to practice maneuvers. About 17 minutes later, the aircraft broke apart in flight.

Approximate sky condition while heading west as maneuvers were begun (as depicted by MS Flight Simulator™)

The NTSB accident report lists the probable cause as: "The pilot's failure to maintain adequate control of the airplane, which resulted in the pilot exceeding the design limits of the airplane and subsequent in-flight separation."

What happened and how could it have been avoided? The sun was very low as the airplane departed. Flying west toward their practice area would provide better illumination than if they had been heading east. The logical supposition is that as the two CFIs entered a steep turn or some other maneuver and the airplane turned away from the sun, outside visual reference was lost.

Approximate sky condition as airplane is turned toward the northeast (as depicted by MS Flight Simulator™)

Perhaps the nose dropped below the horizon and proper recovery technique (leveling the wings before applying up elevator) was not used. The Saratoga is a wonderfully stable airplane. It is also a clean, high performance machine that will accelerate rapidly with the nose down, especially if there is a relatively high power setting such as that required to perform 55° bank steep turns.

No one will ever know exactly what transpired in that cockpit. There may have been a failure to recognize

Possibly what the left pilot saw as the airplane departed controlled flight (as depicted by MS Flight Simulator™)

the unusual attitude in a timely manner or failure to transition to an instrument recovery even though both pilots were instrument rated.

Perhaps there was a failure to positively exchange flight controls. Accidents usually don't start in the cockpit, at least not immediately preceding the time of the accident.

Official NTSB photo of the accident site

More frequently accidents begin before the engine is ever started. It seems

likely that this accident began when the decision was made to embark on a training flight involving visual maneuvers just prior to sunset.

Accident Analysis - Stall/Spin

This accident occurred at Coney Island, New York in May of 2005. It involved a flight instructor conducting a "discovery flight" in a Cessna 172S. The flight departed Linden, New Jersey with full fuel and two rear seat passengers in addition to the instructor and prospective student.

View approaching Coney Island (as depicted by MS Flight Simulator™)

Rather than proceeding to a practice area, the instructor elected to conduct a sight-seeing flight around Coney Island. This made it necessary to remain at low altitude due to the New York Class B Airspace. Radar data indicated that the pilot initially climbed to about 500 feet of altitude and headed toward Coney Island. Numerous witnesses stated that the airplane was maneuvering at low altitude along the beachfront of Coney Island. The airplane disappeared from radar at an altitude of 300 feet and at a ground speed of 60 knots. Witnesses observed that the airplane banked to the left, descended in a nose down attitude, and impacted the ground. All four occupants were killed.

Maneuvering at low altitude around the beach at Coney Island (as depicted by MS Flight Simulator™)

Weather was most certainly not a factor. The sky condition was broken clouds at 5500 ft., visibility 10 miles, and the wind from 190 degrees at 12 knots.

Weight and balance analysis indicated that the airplane gross weight at takeoff was 139 pounds greater than the maximum allowable gross weight. The center of gravity was exactly on the aft limit. Since the accident occurred less than 10 minutes after departure, the weight and center of gravity had not changed significantly prior to the event.

The flaps were extended to the full 30 degree position. This was confirmed by the position of the flap actuator and the flap selector lever. This would seem to indicate that the pilot, a flight instructor with more than 1900 flight hours, was intentionally maneuvering at very low airspeed and very low altitude on an introductory flight.

Approaching the final turn prior to the accident (as depicted by MS Flight Simulator™)

The National Transportation Safety Board determines the probable cause(s) of this accident as follows: The pilot's failure to maintain adequate airspeed, which resulted in an inadvertent stall and subsequent impact with terrain.

How to avoid such an accident is difficult to address. This young, recently trained flight instructor, theoretically had received plenty of instruction in those areas. Was his training sorely deficient? Was the examination process for his Private, Commercial and CFI certification lacking? , or was this a case of poor judgment, "it can't happen to me" mentality, and a desire to show off? Perhaps it was some of each. We will never know for sure.

Official NTSB photo (with N number removed by the author)

So what lessons can be learned? Each pilot must make sure that he or she is very well versed in the causes of a stall/spin accident and what conditions are likely to lead up to such a tragedy. Recurrent training with a flight instructor who is not afraid to examine cross control stalls and other "uncomfortable" maneuvers is highly recommended.

Official NTSB photo

Realizing that the laws of aerodynamics are completely blind experience level, age, gender, race, and socioeconomic standing is also essential. It can happen to anyone who allows the airplane to get into the low altitude stall, regardless of the reason.

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