Spin Recovery and Instrumentation - Comprehensive Study Notes

Spin terminology and recovery basics

• Recovery framework discussed: PARE model (power to idle, ailerons neutral, rudder opposite, elevator forward) as a generic recovery technique when the specific recovery for a given airplane isn’t known from the AFM/POH.
• Airplane Flying Handbook notes: If you don’t know the airplane’s exact recovery technique, using PARE can save a life; however, each airplane may require a different technique.
• Aircraft-specific differences mentioned:
  • Piper Arrow example: recommends using rudder first.
  • DA-20/DA-40 (DA 20 20) example: may not mention anything about ailerons in the basic recovery description.
• Spin concepts:
  • Incipient spin: the beginning of a spin, typically from an uncoordinated aggravated stall where one wing stalls more than the other.
  • A fully developed spin: a stall coupled with yaw; the airplane descends in a corkscrew path.
• Coordination and ball indication:
  • Turn coordination is indicated by the turn coordinator with a ball; keeping the ball centered helps ensure the relative wind is perpendicular to the wings.
  • A slip or skid indicates an off-center ball; ball position affects stall onset due to relative wind changes.
• Angle of attack vs horizon (common misconception addressed):
  • Angle of attack is the angular difference between the wing’s cord line and the relative wind, not the horizon or earth reference.
  • In a skidding turn, excessive rudder can skew the relative wind and raise the angle of attack on one wing, causing that wing to stall first.
• Skidding turn dynamics:
  • Skidding right turn occurs when you bank right but push too much right rudder.
  • The outside ball position will reflect a skid; the wing with the higher angle of attack may stall first depending on the relative wind, not the earth’s horizon.
  • The instructor emphasizes that the center-ball indicates proper coordination and helps prevent entering a spin.
• Spin initiation scenario recap:
  • A right turn with excessive right rudder can initiate a spin if the right-wing stall leads to rotation; the first stall discussion is tied to which wing has the highest angle of attack under slipping/skidding conditions.
• Spin recovery sequence (spin conditions):
  • In a spinning airplane, recover by: throttle to idle, full opposite rudder, ailerons neutral.
  • Keep the ailerons neutral to avoid asymmetrical lift that could worsen the situation.
  • In a fully developed spin, it can take a long rotation to stop; leaving full opposite rudder in during the recovery is advised to eventually stop the rotation.
  • Do not instinctively switch rudder if you don’t see an automatic response; trust the recovery sequence.
• Stall recovery principle:
  • The ultimate recovery from any stall is to reduce the angle of attack (stick forward) and unload the wing.
  • “Unload the wing” means reducing load so the wing is not being excessively asked to produce lift; a zero-g condition reduces stall tendency.
• Practical notes from training:
  • Early stall training anecdotes: students may unintentionally move the other aileron during a wing drop; the recommended action is to lower the angle of attack and use rudder for directional control while keeping the wings almost neutral.
• General recovery emphasis:
  • The aim of stall/spin recovery is to return to straight and level flight by reducing angle of attack and regaining coordinated flight.

Instrument fundamentals: altimeter, altitude, and pressure concepts

• Indicated altitude: the altitude read directly from the altimeter, which is calibrated and corrected for instrument error.
• Pressure altitude: altitude corrected for nonstandard pressure; standard pressure is P_{ ext{std}} = 29.92 ext{ inHg}.
• Pressure altitude concept: when the altimeter is set to standard pressure (29.92 inHg), it reads pressure altitude; to determine current pressure altitude, compare the current barometric pressure from weather sources (AWOS/ASOS) with standard.
• Relationship between pressure and altitude:
  • For every inch of mercury change, altitude changes by approximately ext{altitude change} \approx 1000\ ext{ft}.
  • For a change of 0.01 inHg, altitude changes by approximately ext{altitude change} \approx 10\ ext{ft}. (1 inHg ≈ 1000 ft; 0.01 inHg ≈ 10 ft)
• Practical use:
  • Read current barometric pressure from weather reports and convert to pressure altitude using the rule above when standardization is needed.
  • If you set the altimeter to 29.92 inHg, you are effectively reading pressure altitude, which is useful for high-altitude aviation planning.
• Field elevation and altitude planning:
  • Altimeter setting should bring indicated altitude within 75 feet of field elevation for planning purposes.
  • The 75 ft guideline helps ensure altitude awareness during approach and landing planning.

Altimeter and static/ram air system issues (instrumentation hazards)

• Ram air system issues:
  • If ram air becomes clogged but the drain hole remains open, the instrument system pressure can go to zero, causing the airspeed indication to drop to zero inaccurately.
  • If both ram air and drain hole become clogged, pressure is trapped inside the system; this can cause level flight to show a fixed airspeed and will not reflect true changes in airspeed.
• Static port issues:
  • A clogged static port affects the reading of the airspeed indicator (through the pitot-static system) and can lead to incorrect airspeed indications, incorrect altimeter and VSI behavior.
  • Any static system fault requires consideration of an alternate static source.
• Alternate static source:
  • Some airplanes (e.g., certain DAs) have an alternate static source venting inside the cabin; enabling it changes the indicated readings to reflect cabin conditions rather than external ambient pressure.
  • If the external static system is compromised, the cockpit instruments (altimeter, VSI, airspeed) can behave differently when using the alternate static source.
• Instrument stack and information flow:
  • In conventional “six-pack” airplanes, the static/ram-air issues affect the airspeed indicator, altimeter, and vertical speed indicator (VSI).
  • In-equipped modern glass cockpits, the display includes MFD (multifunction display) and PFD (primary flight display) with GPS moving map and integrated systems; these present the instrumentation differently but can still be affected by static/ram-air faults.

Modern avionics: MFD, PFD, GPS, and autopilot integration

• Instrumentation suite described:
  • MFD: multifunction display; PFD: primary flight display; GPS with moving map; two-axis autopilot integration.
  • Integrated autopilot and flight management system (FMS) communication indicates “integration.”
  • Airlines and training fleets include aircraft where autopilot and FMS communicate, making them technically advanced aircraft (TAA/Glass).
• Aircraft models discussed as examples:
  • 465 and 461 are two aircraft with integrated autopilot and FMS mentioned; both are considered technically advanced aircraft (TAA).
  • For instrument training, you are considered eligible to operate in 465 (an integrated platform) similar to other airplanes.
• Practical exam and training implications:
  • You will encounter questions about MFD, PFD, GPS with moving map, and integrated autopilot in instrument-written exams.
  • The presence of integrated systems changes flight deck management and requires additional training hours for certain certifications.

Horizontal Situation Indicator (HSI) and navigation fundamentals

• HSI advantages:
  • An HSI is essentially a DG (directional gyro) integrated with a magnetometer to provide headings with VOR navigation overlaid; it eliminates reverse sensing and simplifies interpretation of navigation data.
  • The HSI uses magnetometer input to provide true magnetic directional information and reduces inertial precession effects seen in legacy DG-based indicators.
• Relationship to DG and VOR:
  • The HSI presents a VOR display concept over the heading indicator, including the VOR/ILS course pointers.
  • In operation, an HSI provides the navigation cues in a single instrument with the heading orientation, eliminating some of the older dual-sensing limitations.
• Limitations and inoperative conditions:
  • When an HSI is inoperative, you may revert to a standard heading indicator (with possible reverse sensing or other limitations) and rely on separate VOR indicators.
• Operational tips:
  • Expect to see references to an “X-out” symbol indicating an out-of-service instrument; this may appear on the heading indicator or the HSI when faulty.
  • Always cross-check heading information with other nav instruments and systems when an HSI is inoperative.

Certification, training hours, and complex aircraft concepts

• Complex airplane requirements (commercial/corporate):
  • Requires 10 hours of training in a complex airplane or in a technically advanced aircraft (TAA) such as a turboprop or turbojet; this requirement varies by certificate and program.
  • In some programs, a designated option (like “465” or similar an integrated glass platform) may fulfill the complexity/technique criteria within the school’s fleet.
• Instrument training and TAAs:
  • As an instrument student, you may be eligible to operate 465 as a technically advanced airplane (TAA) within the program’s structure, consistent with the school’s policy on instrument training in TAAs.
• Practical implications for flight hours:
  • For commercial or corporate pilots, you must complete ten hours of training in a complex airplane or a TAA; however, the details depend on the specific program and aircraft availability.
• Autopilot and FMS integration implications:
  • Some airplanes (465, 461) are described as having integrated autopilot and FMS; these characteristics classify them as technically advanced and require dedicated training on automation and flight management.
• Practical pilot preparation guidance:
  • Be prepared for instrument written exam questions that emphasize MFD/PFD, GPS with moving map, and integrated two-axis autopilot concepts.
  • Ensure altimeter calibrations and instrument tolerance checks (e.g., altitude within 75 feet of field elevation during planning) as part of preflight procedures.

Miscellaneous notes and practical reminders from the session

• Real-world reminders:
  • When performing stalls and spin training, keep a calm, methodical approach; avoid overcorrecting with ailerons during a wing drop; focus on reducing angle of attack and maintaining coordination.
  • During calm or VFR conditions, rely on the ball, heading indicator, and turn coordinator to monitor coordination and anticipate potential loss of control situations.
• Anecdotes and situational examples:
  • An anecdote about the static system during cold or humid conditions and a wash taught in the field; such experiences highlight the fragility of pitot-static systems and the need for understanding alternate static sources.
  • An instructor’s observation about experiences in training (e.g., stalls and spins) reflecting human factors in learning and response times.
• Practical study notes for exam prep:
  • Expect test questions on MFD, PFD, GPS moving map, and integrated autopilot concepts; be able to explain how an integrated system differs from non-integrated avionics.
  • Be prepared to explain how the vertical speed indicator, airspeed indicator, and altimeter respond to static system faults and the role of alternate static sources.
  • Remember the fundamental relationship between pressure, altitude, and the standard 29.92 inHg reference for pressure altitude calculations and flight planning.

Quick reference formulas and constants

• Standard pressure reference:
  • P_{ ext{std}} = 29.92\ ext{inHg}.
• Altitude change per pressure unit:
  • \Delta h \approx 1000 \times \Delta P_{\text{inHg}}\ \,\text{ft}.
• Pressure altitude formula (conceptual):
  • \mathrm{PA} = \text{Elevation} + (29.92 - P_{ ext{actual}}) \times 1000 \,\text{ft/inHg},
  • or equivalently set the altimeter to 29.92 inHg to read pressure altitude directly.
• Angle of attack definition:
  • \alpha = \angle(\text{chord line}, \text{relative wind})
  • Note: not related to the earth horizon; depends on relative wind geometry.
• Important planning guideline:
  • Altimeter accuracy and planning: ensure indicated altitude is within 75\ \text{ft} of field elevation when planning approaches and departures.
• Spin recovery sequence (summary):
  • Idle, full opposite rudder, neutral ailerons; then reduce angle of attack and recover to straight-and-level flight.

Guidance for study and exam readiness

• Review the generic PARE procedure and discuss airplane-specific variations found in AFM/POH for the aircraft you fly.
• Understand spin concepts: incipient spin vs fully developed spin, and how coordination (ball) prevents unwanted spins.
• Know the differences between ram air, static port issues, and alternate static sources; understand how these affect airspeed indicator, altimeter, and VSI readings.
• Be familiar with modern avionics terminology: MFD, PFD, GPS moving map, and integrated autopilot/FMS systems; recognize how they influence instrument interpretation and flight planning.
• Memorize the key relationships between pressure, altitude, and standard reference pressure (29.92 inHg) for calculations and instrument settings.
• Understand how to interpret HSIs and the role of magnetometers in navigation displays, including the concept of reverse sensing and DG precession.
• Remember the certification implications for complex aircraft and TAAs, including the 10-hour requirement and how schools may integrate 465/461 platforms into instrument training.