Flying - Page 18 Aviation Articles

Aircraft Spins 101


Photo: H. Rabb/Wikimedia
As mentioned in my previous article on stalls, accidents that occur due to stall/spin scenarios are more fatal than others. According to an AOPA study, stall/spin accidents have a fatality rate of about 28 percent, higher than the overall average fatality rate of 20 percent.

A spin occurs when an airplane stalls in an uncoordinated or aggravated state. If a recovery is not initiated after an uncoordinated stall occurs, the wing that is more stalled than the other will drop and the nose will follow into a spiraling descent. The aircraft will descend rapidly in a corkscrew motion.

According to the Jeppesen Private Pilot Manual, a small airplane will descend about 500 feet for each turn in a spin, so there's not much altitude or time available for a recovery in many cases. Considering stalls and spins often occur at low altitudes to begin with, it's clear why the fatality rate is higher for these accidents.

Stages of a Spin
The FAA has outlined three stages for spins in light aircraft: incipient, fully developed and recovery.

  • Incipient: The incipient phase of a spin is the stall and spin entry, up to about 2 turns in the spin.
  • Fully Developed: When the airspeed and rotation stabilize, the spin is considered fully developed.
  • Recovery: Recovery occurs when the pilot applies rudder and aileron inputs to counter the spin and the aircraft regains lift and control function. Once the inputs are initiated to stop the spin, the aircraft can usually recover in less than one spin.

Types of Spin

  • Erect Spin: Erect spins are the most common type of spin, occurring when the aircraft rolls and yaws in the same direction and the aircraft is upright and in a slightly nose-down attitude.
  • Inverted Spin: An inverted spin occurs when the aircraft spins upside down and yaw and roll occurs in opposite directions.
  • Flat Spin: Getting its name from the flat-like pitch attitude, the flat spin occurs when the aircraft spins at a level pitch attitude around the vertical axis as a result of a yawing motion alone. Flat spins are the most difficult to recover from (and just as difficult to enter in some aircraft!)

 

Spin Recovery
Spin recovery should be initiated at the first sign of a spin. Recovery procedures are specific to the aircraft flown and are found in the pilot operating handbook of each aircraft. In light aircraft, the spin recovery procedures follow a typical pattern and can be remembered by the common acronym PARE.

P - Power: The throttle should be moved to the idle position to reduce thrust.
A - Ailerons: Ailerons should be neutralized.
R - Rudder : Full opposite rudder input should be applied until the rotation is stopped. If the aircraft is rotating to the left, right rudder should be applied. Once the spinning stops, the rudder should be neutralized.
E - Elevator: Quick forward pressure should be applied to break the stall and gain airflow over the wings. Once the aircraft gains lift, back pressure should be applied gradually so as not to stall again.

Training aircraft are stable by design. They're meant to recover from unusual attitudes without much external control input from the pilot. A Cessna 172, for example, is actually somewhat difficult to perform an intentional spin in. But this doesn't mean that pilots of training aircraft are immune to spins.

While intentional spins are not always demonstrated during training, stall and spin awareness should always be emphasized with flight students. Many pilots tend to become confident in stall recovery, but all pilots would be wise to remain familiar with spin entry characteristics and recovery procedures for their specific aircraft.

How Well Do You Know Your Stalls & Spins?


Image: Theresa Knott/Wikimedia Commons

For new flight students and passengers, an aircraft stall can often be a source of fear. What is a stall? Will the airplane fall out of the sky? Does the engine quit?

And while stalls shouldn't be something that pilots fear, they should be taken seriously. Aircraft stalls and spins remain a leading cause of general aviation accidents - causing ten percent of general aviation accidents, according to one AOPA study. And stall/spin accidents result in more fatalities than other types of aircraft accidents. Private and commercial pilots are most likely to enter a stall, while student pilots and ATPs are less likely to stall, according to AOPA.

A 2012 advisory circular claims that loss of control accidents are a growing problem and that inappropriate reactions to stall indications are part of that problem.

What's a Stall?
Let's start with the basics. For those of you non-pilots, you need to know that an aircraft stall has absolutely nothing to do with the engine (unless we're talking about compressor stalls - an entirely different topic). Instead, an aircraft stalls when the airflow over the wing is disrupted enough to cause a loss of lift.

Stalls are dangerous because control surfaces become inadequate to control the flight, and if a recovery is not initiated, the aircraft will quickly lose altitude. And then there's that deadly spin: If uncoordinated, a stall can develop into a spin.

The FAA defines an aircraft stall as "an aerodynamic loss of lift caused by exceeding the airplane’s critical angle of attack."

The critical angle of attack is the key phrase here. The angle of attack is the angle between the chord line of the wing (an imaginary line running from the leading edge of the wing to the trailing edge) and the relative wind. The critical angle of attack is the angle at which maximum lift is produced. An increase in the angle of attack beyond the max coefficient of lift results in a loss of lift, airflow separation over the wing and a subsequent stall.

An aircraft can stall at various airspeeds, altitudes, pitch attitudes, configurations and weights. But the critical angle of attack must be exceeded for a stall to occur.

Types of Stalls

  • Power on stall: A power-on stall occurs during situations in which the aircraft power or thrust is increased quickly, such as during takeoff. Power on stalls usually occur (not always) with gear and flaps up.

  • Power off stall: Power off stalls occur when the aircraft power is decreased or at idle, such as during landing. Power-off stalls tend to occur with gear and flaps down.

  • Elevator trim stall: If the pilot disregards the elevator trim setting, any abrupt change in power or configuration can initiate a stall. This can happen easily during takeoff or go-arounds, when the aircraft trim tab is adjusted for the descent and a go-around is initiated. The aircraft can pitch up quickly and unexpectedly to a high angle of attack.

  • Cross controlled stall: A cross-controlled stall is one of the most dangerous types, as it's an uncoordinated stall and easily transitions to a spin. A cross-controlled stall occurs when the pilot inputs aileron control in one direction and rudder pressure in the opposite direction. Cross controlled stalls are known to occur during turns in the traffic pattern.

  • Accelerated stall: When excessive loads are placed on the airplane (such as during steep turns), an aircraft is capable of stalling at a higher airspeed and/or a lower pitch attitude than the pilot might be accustomed to.

  • Secondary stall: Secondary stalls occur if a pilot attempts to recover from a stall too quickly by pitching up to recover from the dive before obtaining an appropriate airspeed and generating enough lift.

  • Deep stall: Also called a super stall, the deep stall happens in T-tail aircraft, like this Piper Lance II or this King Air 350. It occurs when the airflow over the wing is disrupted and airflow over the tail of the aircraft is also disrupted, rendering both the ailerons and elevator/rudder ineffective at the same time. In a deep stall, recovery is difficult and sometimes, impossible.

Spins
An uncoordinated stall can result in a spin. According to the FAA Airplane Flying Handbook, a spin is an aggravated stall that results in autorotation - a downward corkscrew motion.

The spin is a result of one wing being at a higher angle of attack than the other, often descried as one wing being "more stalled than the other." The difference in angles of attack creates lift on the less stalled wing and drag on the more stalled wing.

Spins are more difficult to recover from, as altitude is lost very quickly and control surfaces may react different than the pilot expects, which is why it's important for pilots to continuously practice stall and spin recovery.

Mayday, Mayday, Mayday! - the Origin of a Distress Call

In honor of May Day (May 1st, a holiday associated with the beginning of spring and the labor movement in many counties), I thought I’d take a moment to explore how the same word came to mean HELP in aviation!

The term Mayday is used internationally as a distress signal in voice procedure radio communications. It derives from the French venez m'aider, meaning "come help me". It is used to signal a life-threatening emergency by many groups, such as police forces, pilots, firefighters, and transportation organizations. The call is always given three times in a row ("Mayday Mayday Mayday") to prevent mistaking it for some similar-sounding phrase under noisy conditions, and to distinguish an actual Mayday call from a message about a Mayday call.

The Mayday procedure word originated in 1923 by Frederick Stanley Mockford (1897–1962). A senior radio officer at Croydon Airport in London, Mockford was asked to think of a word that would indicate distress and would easily be understood by all pilots and ground staff in an emergency. Since much of the traffic at the time was between Croydon and Le Bourget Airport in Paris, he proposed the word "Mayday" from the French m’aider.

Before the voice call "Mayday", SOS was the Morse code equivalent of the Mayday call. In 1927, the International Radiotelegraph Convention of Washington adopted the voice call Mayday in place of the SOS Morse Code call.

Other emergency calls include "Pan-Pan" (from the French: panne – a breakdown), or simply "declaring an emergency" – although the International Civil Aviation Organization (ICAO) recommends using the two terms above to prevent confusion and errors in aircraft handling. The use of these terms without proper cause could render the user liable to civil and/or criminal charges.

Now to come full circle, I leave you with a related scene from one of your favorite aviation films.

Develop Your Next Aviation Manager with CAM

Professional development is a given expectation within management. Within aviation, this expectation clearly extends to aviation-specific training. Pilots get recurrent training in simulators, maintenance technicians get recurrent training on the airframe, engine or avionics. But we do these men and women a disservice when we promote them from a technical position into a managerial position without giving them the tools they need to be successful managers.

I have seen instances where a senior captain who has done an exemplary job in the cockpit is congratulated and promoted into the aviation department manager position. What seems like a logical move turns sour when the pilot-turned-Manager finds himself facing a budget cut, a problem employee, and OSHA regulatory issues in the hangar. None of these situations was addressed during engine-out training! They got frustrated and either seek a return to the cockpit or leave for another flying position with no management duties. Future aviation leaders need training and experience in the managerial arts.

Commanding a second person in the cockpit takes special skills. But those skills need additional development for leading a large team. Corporate aviation leaders need to understand the vision and mission of the corporation and how aviation is an essential business tool. They need to know how to  align their aviation department goals with the overall corporation's goals. They then need to develop a leadership and communication style appropriate to their personality that will inspire they aviation team.

Aviation department leaders need to develop skills in operations management. This extends well beyond aircraft operations to include business risk analysis, cost benefit analysis, record keeping and audit requirements, OSHA and hazardous materials regulations, and more. As part of their operations management the aviation leader is often a facilities manager. 

Lastly, the aviation manager needs skills in all the remaining business management skills. The aviation manager is running a small business. They need financial skills in budgeting, forecasting, cost management, and taxes. They need to know what the record keeping requirements are and to be able to understand asset management of the aircraft and facilities.  The aviation manager needs to understand the corporate HR domain, and be able to communicate those policies to all the employees. This training combines both regulatory requirements and personnel management skills, or soft skills.

Within business aviation, we are fortunate to have a customized program geared to develop aviation professionals into management professionals: The National Business Aviation Association (NBAA) Certified Aviation Manager (CAM).

The NBAA CAM certification and education program offers credit for professional experience, college courses, and professional development programs offered within the aviation community. The CAM program is a rigorous professional certification that is designed to maximize a busy aviation professional's time in developing the skills need to be managers in leaders.

Don't overlook maintenance technicians for this CAM training. I see the pilot career path progress from First Officer to Captain to Chief Pilot to Aviation Department Manager. But too often the maintenance technical career path ends at Chief of Maintenance. Even that position requires management and leadership skills. Maintenance Technicians are an overlooked source of future aviation department leaders. They often have a significant understanding of the aviation operation beyond the toolbox that the pilots have yet to learn. 

Promote personal development for your flight department personnel, just as a company does for middle managers seeking career advancement.


 

The Aerobatic Experience of a Lifetime

There is great excitement around Louisville right now. Last weekend Thunder Over Louisville came to our charming little city. Thousands of people gathered around the Ohio River to watch the Blue Angels, Lima Lima Flight team, Trojan Horsemen, Team AeroDynamix, and several other big names in airshow entertainment. It was a sunny day with a slight breeze, the perfect setting for the 25th anniversary of the airshow.

One of these Thunder performers was John Klatt. He is an Air National Guard pilot who proudly flies the F-16 "Fighting Falcon" and C-130 "Hercules" aircraft on combat, air support, and humanitarian missions. In addition to all of this, he is an airshow performer extraordinaire with over 10 years’ experience flying for millions of spectators. In his current routine he flies his MXS in a plethora of twists, turns, and flips at stunning speeds.

Last Thursday I had the opportunity to ride along with John and his flight crew for some practice before the big event. I strapped on my parachute and climbed into the front seat of their 300 horsepower Extra 300L. I had not experienced aerobatics previously, so as they secured me with the abundance of harnesses and safety straps I had a brief moment where I was questioning what I was getting myself into. Being born a thrill seeker, I gave a thumbs up to the crew and braced myself for the adventure that awaited us.

After an incredibly speedy liftoff, we flew in close proximity behind John in his single seat MXS. When we reached the practice area he headed north of the Ohio river and we headed south to do maneuvers. We started out simple, with just a dive from 5000’ to gain airspeed and roll into some steep turns. After this we did a hammerhead, loop, and barrel roll. I tried to play it cool but every moment I lost sight of the ground I couldn’t help but grin.

Flying aerobatics is what I believe to be one of the fundamentals of aviation. Humans have always been seeking out the biggest thrills. We question how fast something can go, how high we can fly. Part of human nature is pushing the limits and finding new ways of controlling our surroundings. For years we have been building faster and better aircraft in this pursuit of maximizing our abilities. Maybe I am getting too philosophical with this, but the entire concept of aerobatics beautifully demonstrates the human spirit. Airshows are built around this human adoration of pushing boundaries. The fact that we have created machines capable of such breathtaking feats is worth celebration enough. Add in the remarkable skill and talent of pilots like John Klatt, and you have a perfect display of human intellect and liveliness.

After I hopped out of the Extra 300L, I felt like my eyes had been opened to a whole new world of flying capabilities. The sheer power and agility of the plane shocked me. This truly was an unforgettable experience and I want to thank John Klatt and his team for this opportunity.

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