Peter's Flight Log

I was waiting for this lessons for since my instructor demonstrated a steep turn a couple of months ago. I remember the feeling of the 2Gs, and how moving hands was very laborious. I wasn't ready for that experience back then, and I even remember my vision becoming a little blurred.

But today, I was ready. In today's flight (first of two), my instructor would show me how to do steep turns, usually 45° or 60° angle of bank, in the sky over Cessnock. Towards the end of the flight, he would also show me how to deal with a steep turn gone wrong and evolved into a spiral dive. A spiral dive is a very dangerous situation which can be rectified if identified early.

Let's do the introductions: Steep turns, and Spiral Dive.

A steep turn is a maneuver where the aircraft is rolled into a bank angle greater than 30 degrees, typically around 45 to 60 degrees, while maintaining altitude and speed.

Here's how it's done:

1. Preparation: Before starting, we'll perform a clearing turn to ensure the area is free of traffic. This is essential for safety. We'll also make sure the aircraft is at a safe altitude, usually above 3,000 feet AGL, and check that our speed is at the maneuvering speed (Va), which for a Cessna 172 is around 97 KIAS (Knots Indicated Air Speed).
2. Entry: Begin the turn by smoothly applying aileron to roll into the desired bank angle. As we reach around 30 degrees of bank, we need to apply back pressure on the yoke to maintain altitude. The steeper the turn, the more back pressure we need to keep from descending.
3. Power Management: In a steep turn, because of the increased bank angle, we experience a higher load factor (G-force), which increases the stall speed. To counter this and maintain altitude, we'll need to add a bit of power. Usually, an increase of about 100-200 RPM is sufficient for a 45-degree bank turn.
4. Maintaining the Turn: As we hold the bank, keep an eye on the horizon, the attitude indicator, and the altimeter. Use small, smooth inputs to adjust the pitch and bank as needed. If the nose drops, increase back pressure slightly. If it rises, ease off a bit.
5. Exiting the Turn: To roll out, smoothly reduce the bank angle back to wings level by applying opposite aileron. Simultaneously, reduce the back pressure and power to return to cruise settings.

A few tips to keep in mind:

• Look outside: Use the horizon to help judge your bank angle and maintain your reference point.
• Scan your instruments: Balance your outside references with a good instrument scan to ensure you're holding altitude and airspeed.
• Stay coordinated: Use the rudder to keep the turn coordinated and prevent skidding or slipping.

Given that steep turns do stress pilot and plane, I was curious to know some cases where such turns can be used (other than impressing friends and feeling like a Top Gun pilot). Remember, steep turns have a significant inherent risk, as they can turn into a spiral dive is the execution is not correct.

Steep turns have several practical applications in general aviation and are an important skill for any pilot to master. Here are some of the typical uses and scenarios where steep turns are applied:

1. Avoiding Obstacles: In the event of encountering unexpected obstacles, such as terrain or other aircraft, a steep turn allows for a quick change in direction while maintaining altitude. This is crucial for collision avoidance.
2. Traffic Patterns: While not typically performed in traffic patterns due to their aggressive nature, understanding and practicing steep turns help pilots become more adept at making tighter, more controlled turns when necessary, such as during base to final turns in a busy traffic pattern.
3. Emergency Situations: In emergencies, such as engine failure after takeoff, a steep turn might be required to turn back to the runway if there's no suitable landing area ahead. This is often referred to as the "impossible turn," and while generally discouraged, understanding steep turn dynamics is critical for evaluating such situations.
4. Search and Rescue: When participating in search and rescue missions, pilots may need to make tight, controlled turns to maintain visual contact with the ground and cover a search area efficiently.
5. Navigational Adjustments: When navigating through complex airspace or around weather systems, a pilot might need to make sharp turns to stay clear of restricted areas or adverse weather conditions.
6. Pilot Training: Steep turns are a standard maneuver in pilot training and checkrides. They help pilots develop a better feel for aircraft control, understand the effects of load factor on the aircraft, and improve coordination between the controls.
7. Aerial Photography and Surveying: Pilots conducting aerial photography or surveying often perform steep turns to keep the camera focused on a particular point of interest on the ground.
8. And of course, combat and tactical maneuvering: In military aviation, steep turns are used extensively for tactical maneuvers to evade threats or position the aircraft advantageously in combat scenarios.

The physics of steep turns

When performing steep turns, especially at bank angles of 45° and 60°, the forces acting on the airplane and its occupants change significantly compared to level flight. These maneuvers subject the aircraft and its passengers to various forces, primarily centripetal force, gravitational force, and aerodynamic lift. Here’s a detailed analysis of these forces:

1. Centripetal Force: This force acts towards the center of the turn, causing the airplane to follow a curved path. It is a result of the lift component acting horizontally.
2. Gravitational Force (Weight): This force acts downward towards the center of the Earth. It remains constant in magnitude but can be perceived differently by passengers due to changes in the lift vector.
3. Aerodynamic Lift: In a steep turn, lift must be increased to maintain altitude. The total lift vector is tilted, resulting in a horizontal component (providing centripetal force) and a vertical component (counteracting weight).

Analysis at 45° Steep Turn

1. Bank Angle: 45°
2. Load Factor:
   • The load factor (nn) is the ratio of the total lift to the airplane's weight.
   • At 45°, n=1/cos⁡(45°)=1.414.
   • This means the aircraft and passengers experience 1.414 times the force of gravity (1.414 G).
3. Centripetal Force:
   • The centripetal force increases as the bank angle increases, necessitating an increase in the total lift produced by the wings.
4. Lift Vector:
   • The lift vector is tilted 45° from vertical.
   • The horizontal component provides the necessary centripetal force to turn, while the vertical component must equal the weight of the airplane to maintain altitude.

Analysis at 60° Steep Turn

1. Bank Angle: 60°
2. Load Factor:
   • At 60°, n=1/cos⁡(60°)=2
   • This results in the aircraft and passengers experiencing 2 times the force of gravity (2 G).
3. Centripetal Force:
   • The centripetal force is significantly higher due to the steep bank angle.
   • Increased lift is required to balance the increased load factor and maintain altitude.
4. Lift Vector:
   • The lift vector is tilted 60° from vertical.
   • The horizontal component of lift is much larger, providing the necessary centripetal force for a tighter turn.
   • The vertical component must still counteract the weight of the airplane, meaning the wings must produce much more lift overall.

Implications for Passengers

• Increased Load Factor: Passengers feel heavier during the turn due to the increased load factor. At 45°, they feel 1.414 times their normal weight, and at 60°, they feel twice their normal weight.
• Comfort and Safety: Prolonged exposure to high G-forces can cause discomfort or even physiological effects such as increased heart rate and blood pressure. Safety measures and training are essential for handling these conditions.

Summary

• 45° Turn: Requires 1.414 times the lift, resulting in a 1.414 G load factor. Suitable for moderate maneuvers.
• 60° Turn: Requires 2 times the lift, resulting in a 2 G load factor. Suitable for more aggressive maneuvers.

A spiral dive, also known as a spiral descent or graveyard spiral, is a dangerous flight condition where an aircraft enters a steep, descending turn with increasing airspeed and load factor. If not corrected, a spiral dive can lead to structural failure or a crash due to the excessive speed and G-forces.

We learn to recognise and address a spiral dive in the steep turn lesson, because often a spiral dive is the result of a poorly done steep turn.

These are the main causes of spiral dives:

• Loss of Situational Awareness: Pilots may inadvertently enter a spiral dive due to disorientation, especially in poor visibility conditions or when flying under instrument flight rules (IFR).
• Improper Bank Control: A small, uncorrected bank can gradually lead to a steepening turn. Without proper correction, the aircraft can enter a spiral dive.
• Failure to Maintain Attitude: Inattention to the aircraft's attitude can result in a gradual descent and increasing bank angle.
• Misuse of Controls: Incorrect use of the ailerons, rudder, or elevator can exacerbate the situation. For example, trying to correct the bank angle with ailerons alone without addressing the descent can worsen the spiral.
  

To address a spiral diver, the pilot must use this technique immediately. It is important to apply one control at a time. For example, first reduce power, then level the wings. Not at the same time!

Here's what to do, which is also what I practiced on this flight:

1. Recognize the Situation: Awareness is crucial. Pilots must recognize the increasing bank angle, descending turn, and rising airspeed. Indicators include an unusual attitude, rapid altitude loss, and increasing G-forces.
2. Power Reduction: Immediately reduce engine power to idle. This helps to decrease airspeed and reduce the load factor on the aircraft.
3. Level the Wings: Use coordinated aileron and rudder inputs to roll the wings level. Be careful to avoid overcorrecting or causing further instability.
4. Raise the Nose: Once the wings are level, gently pull back on the control column to raise the nose and stop the descent. Avoid abrupt movements to prevent overstressing the airframe.
5. Gradual Recovery: After stopping the descent and leveling the wings, gradually increase power to return to level flight. Monitor the airspeed and attitude throughout the recovery.
6. Check and Stabilize: Ensure the aircraft is stabilized in level flight, with appropriate airspeed and attitude. Verify the altitude and make any necessary adjustments to return to the desired flight path.

Out of everything that I have learned so far, the spiral dive has been, surely, the scariest. A spiral dive is a hazardous flight condition where an aircraft enters an uncontrolled descending turn. Causes include loss of situational awareness, improper bank control, and misuse of controls. To recover from a spiral dive, reduce power, level the wings, gently raise the nose, and stabilize the aircraft in level flight. Proper training and vigilance are essential to prevent and correct spiral dives effectively.

My flight

On this flight, we took off from runway 35 of Cessnock Airport (YCNK), and departed overhead the runway towards the east. I'm starting to get better with CTAF calls and develop an intuitive understanding of what to say and when. My instructor pointed out the various landmarks ahead of us, such as Newcastle, Lake Macquiarie, a power station, and several peaks that I'd be using to enter and exit turns.

Once we reached 3,000 ft, we did a clearing 30° full circle turn to check for traffic, and warm up. After that, Harry showed me a 45° turn, and asked me to do it. This was easy!

Then, it was time for the 60° turn. Harry showed me the first one. Check for traffic, start the bank, coordinate airerongs and rudder. When passed 30°, set throttle to full, and continue the bank until reaching 60°.

That angle of bank does feel very unatural and even scary at first. Thankfully, the pilot is busy working through the turn. Look out the window to ensure that the bank is maintained and the horizon cuts the dash where it should. Glance the instruments, one at a time, and then look out.

The workflow is: look out, check horizon, check if its time to exit the turn. Look in the instrument panel for one instrument only (for example, the altimeter), then look out again. Then, look at another instrument, like the artificial horizon, and then quickly look out. Dont stare at instruments because time is accelerated in a steep turn. It is easy to get fixated with the intruments and not realise the you missed the landmark to exit the turn, or become dissoriented when finally looking out again (a very dangerous situation).

I did several steep turns, and decided to switch to spiral dives.

I was definately not prepared for the sensation of a spiral dive. It's a shame I don't have video footage, but I promise to capture some soon. Harry demonstrated a spiral dive. Although I didn't freak out during the demonstration, my stomach felt sick a few seconds after getting back to straight and level. Harry reached out for a sick bag just in case. I was Ok to continue, and I then executed one myself.

Getting into a spiral dive is very easy. So easy, in fact, that I now understand why learning to recognise it and exit is important. Simple do a steep turn without rudder (to coordinate), and the plane will start to dive. Speed will increase, a lot, and the rate descent will quickly get to 1000 ft/m or even more. You don't even have to look at the instruments to know what is happening.

To exit a spiral dive is just as easy. Reduce power BEFORE levelling the wings with the ailerons. If you try to level the wings before reducing power, there is a good chance that you will stress the wings to breaking point. With the wings level, gradually raise the nose with the elevetors, and when safe, start to add power and climb.

We returned for a landing short after, and my vestibular system continued to feel the effects of the spiral dive for a couple of hours.

Never the less, I'm looking forward to the next opportunity to practice these manuveurs. In the mean time, I got ready for my next flight of the day in which I would practice crosswind circuits.