Preparatory Ground Briefings Series: Spins
In preparing this PGI, it is important to note that this is the first in a series of three in stall sequence taught to the student, as published in the Flight Instructor Guide. The first appears in Lesson Plan #5, where the focus is on basic stalls that use power-off entry and power-off recovery. It is worthy to note that this first appearance of stalls is in fact the second flight under Lesson Plan #5—the first flight in this lesson presents Slow Flight. The second appearance of Stalls in the FIG is in the subsequent Lesson Plan #6, where stalls are presented using power-off entry and power-on recovery—these can be conceived as intermediate stalls, and the third appearance of Stalls in the FIG Lesson Plan #22, where “stalls from critical flight situation” appear—we refer to these as advanced stall. It is good preparation for you to now study how stalls in these three lessons plans.
Keep in mind that the expressions basic, intermediate, and advance, are used somewhat arbitrarily here, simply for the purpose of delineating the stall lesson-plan structure as it appears in FIG. As experienced flight instructors know, there are actually a tremendous variety of both basic intermediate and advanced stalls.
What is important is the developmental nature that stalls are taught and learned. This PGI is in fact the first in a series—the first time the student is introduced to stalls—and your presentation must therefore cover the basics of stall symptoms, pilot management of the stall, and factors that affect stall recovery. Future PGI’s on the intermediate and advanced stalls need not repeat this fundamental, generic information (although don’t hesitate to quickly review). For the subsequent intermediate and advanced stalls, your PGI format—How, Aim, Why, Background Knowledge, How, etc.—need only focus on the critical elements that are unique to the intermediate and advanced stalls variations. So the background section should address, for example, how power or flaps or a banked attitude affects the stall, and the related details should be carried through the how section especially. The discussions below, then, focus only on the student’s introduction to stalls, by way of a stall derived from a power-off entry and a power-off recovery.
The definition should be derived from the Flight Training Manual. Remember to use the student’s involvement in coming up with a definition of the stall as a means of assessing the level of understanding. Reference here should of course be to the critical angle of attack, and you should also provide some background information related to how the stall type examined today fits into the array of stall training the student will be introduced to during pilot training, progressing from basic stalls to more advanced stalls.
You should present the aim of this exercise in relation to effective recognition and recovery, with reference to minimum altitude loss. You could include learning the proper management of a stall conditions so as to avoid transition to a more complex upset condition, such as spin onset.
There are many ways to motivate a student for stall training. Perhaps the most effective and accurate line, however, is to point out that stalls, in and of themselves, are not difficult to recovery from—you simply decrease the angle of attack, and the wing is flying again. What is critical about learning about stalls is the fact that mismanagement of stall, or the failure to recognize the condition and apply proper management inputs, will allow the stall to develop into autorotation—a spin—and even the best of pilots require 700’ of altitude to recover from a full-rotation spin.
Three items are recommended here, the first related to the aerodynamics of stall onset and the the related symptoms apparent to the pilot, and the second related to the critical importance of keeping ailerons neutral in managing stall recovery. A final section should be a listing out of the factors that affect stall recovery.
For the aerodynamics of stall onset, layout on the whiteboard the diagram that appears in the Flight Training Manual should a cross-section of the wing through ever increasing angles of attack. As you work through the ever increasing angles of attack, point out the progressive movement of the separation or transition point separating laminar and turbulent flow, and point out the progressive movement of the Centre of Pressure. As relate to stall symptoms, the stall warning device of the aircraft will typically be triggered prior to buffeting. Have the student review with you the information in the Pilot Operating Handbook provided by the manufacturer related to the stall warning system. Buffeting is the second symptom, and this originates with turbulent flown striking the empennage, etc. The final symptom is the nose drop, and this is associated with the transition of the centre of pressure forward of the centre of gravity.
Critical information is provide next—the aircraft will stall in any attitude and at any airspeed, and all of these symptoms can be blurred to one sudden transition to the stall. The only time an aircraft will stall at the airspeed indicated on the airspeed indicator is when an aircraft’s speed is reduced in level flight—a slow and controlled event. Hazardous stalls occur unexpectedly, surprising the pilot.
Move onto the importance of keeping the ailerons neutral when a stalled condition is encountered. Draw two wing cross-sections on the board, the first representing the left wing, and the second being the right wing. The cross-section should be at the aileron area of the wing. Give both wings a 17° angle of attack (on the verge of the critical angle of attack), and show the ailerons in the neutral position. Now should the effects of roll inputs, whereby one aileron is defected upward, and the other deflected downward. Explain how one wing becomes more stalled, while the other is unstalled, and how this can lead to an autorotation condition. Include the fact that the downward wing will continue to move downward further as it becomes more progressively stalled with the progressive changes in the relative wind flow during its descent, and explain how the upward moving wing does the reverse. Explain that aileron discipline is critical in stall management and that they must be maintained in the neutral position from the point of recognition, to the point of recovery.
The final phase in the background knowledge section is a listing of the factors that affect stall recovery. These can be derived from the Flight Training Manual. Be sure you understand and can explain how each factor works. Each item should be paired with an explanation as to how stall speed is affected—i.e., how indicated stall speed is increased or decreased by the factor. This will be one of your early ventures into relatively complex aerodynamic theory of teaching, and it is important that you properly understand in detail the various factors that affect stalls and stall recovery. While you want to avoid going into these details during your actual PGI with the student, you must be prepared to answer questions that the student may present you. On your flight test, this part of your presentation provides an excellent opportunity for inspectors to probe your level of understanding.
The how section should begin, as always, with a review of any information and direction provided by the manufacturer for the exercise planned in the Pilot Operating Handbook. Once this is accomplished, you can begin with your standard flow for the power-off entry and the power-off recovery sequence.
The items in the sequence should be numbered and clearly labeled, and as the items are placed on the whiteboard, you should dialogue on any background information related to the item or task which you feel is important for the student to be aware of.
You may want to divide sure how sequence into three sections, the first being the setup, which includes the HASEL check, the second being the entry, and the third being the recovery.
Note that the stall recovery requires the aircraft being established in the power-off, maximum distance glide configuration—it would been a good practice to assign this as preparatory reading the flight before, asking the student to read up on this in the POH.
It is worthwhile noting that it is really important for the instructor to emphasize how quickly and how far the nose of the aircraft should be pitch forward during the stall recovery. It goes without saying that the inputs must be smooth, and the goal is to produce a recovery with a minimum loss of altitude. The hands must be move slowly, the students elbow must be planted on the armrest so as to prevent aileron input, and the nose should be pushed forward only as is necessary to extinguish the stall symptoms. If the input is sudden, there is no time to reckon the stall symptoms, so this must be done slowly and thoughtfully.
There should be a reiteration here regarding the altitude requirements for entry, emphasizing that the height above ground must take into consideration the elevation of training.
Security in the cockpit should also be reemphasized, especially as it relates to fire extinguisher security, seatbelt security, and rear seat security via the seatbelts being attached.
The importance of keeping the ailerons neutral should also be reiterated, and you should emphasize that a wing-drop typically invites an untrained pilot into using ailerons to maintain the wings level, and of course this simply aggravates the situation.
Explain the effective use of rudder's in keeping the wings level in a stalled condition.
Explain the actions that will be taken in the event of an inadvertent spin entry, and your communication here should relate to you taking control the aircraft to remedy the situation. I think it would be a good idea for you to review the actions you will take and tell the student will learn how to do this at a later point in the training
Piper Aircraft Corporation Service Bulletin No. 753
Subject: Expanded Spin Recovery Procedures.
Compliance Time: Upon receipt.
To provide expanded spin recovery procedures to assure that proper safety practises and procedures relative to utility category flight operations are in effect. Spin training is permitted only in the utility category.
Accompanying this Service Bulletin is an expanded information placard to be installed in the cockpit in full view of the pilot. This Service Bulletin is to be retained at all times in the aeroplane with the aircraft paperwork.
Weight and Balance
It is the responsibility of the pilot and aircraft owner to determine that the aircraft remains within the allowable weight versus centre of gravity envelope while in flight.
The PA-28-140 is certified for operations in both normal and utility categories. Spins and certain other aerobatic manoeuvres are permitted only when the aircraft is configured in the utility category, which requires that the gross weight and centre of gravity not exceed 1,950 pounds and 86.5 inches aft of datum, respectively. Fuel loading is the primary factor controlled by the pilot that affects the weight and centre of gravity.
The pilot and co-pilot seat location of 85.5” as specified in the A.F.M.2 is the centre position of the seat track. This may vary from a full forward position arm of 80.5” to 90.5” at the most rearward position. Each hole from the centre position of 85.5” changes the arm of the seat location 1.25”.
The seat position to be used for spins should be determined and the correct arm should be used in calculating the aircraft weight and centre of gravity prior to beginning the flight.
To determine the weight and balance limitations refer to the Weight and Balance Section in the appropriate Aeroplane Flight Manual.
The PA-28-140 is approved for certain aerobatic manoeuvres, provided it is loaded within the approved weight and centre of gravity limits (refer to Limitation Section in the appropriate Aeroplane Flight Manual.) The approved manoeuvres are spins, steep turns,3 lazy eights, and chandelles.
Carrying baggage during the spin is prohibited and the pilot should make sure that all loose items in the cockpit are removed or securely stowed, including the second pilot’s seat belts if the aircraft is flown solo.4 Seat belts and shoulder harnesses should be fastened securely and the seat belts adjusted first to hold the occupants firmly into the seats before the shoulder harness is tightened. With the seat belts and shoulder harness tight, check that the position of the pilots’ seats allows fell rudder travels to be obtained in both the full back and full forward control wheel movements. Finally, check that the seats are securely locked in position. The PA-28-140 is approved for intentional spinning only when the flaps are fully retracted. Spins should be started only at altitudes high enough to recover fully by at least 3,000 feet AGL, so as to provide adequate margin of safety. A one-turn spin, properly executed, will require approximately 1,000 feet to complete; and a six-turn spin will require approximately 3,000 feet to complete. The aeroplane should be trimmed in a power-off glide at approximately 96 MPH before entering the stall prior to spinning. This trim airspeed assists in achieving a good balance between airspeed and “g” loads in the recovery dive. Spin recovery has been demonstrated up through six turns.
The spin should be entered from a power-off glide by reducing speed at about 1 kt/sec. until the aeroplane stalls.5 Apply full aft control wheel and full rudder in the desired spin direction. This control configuration with the throttle closed should be held throughout the spin. The ailerons must remain neutral throughout the spin and recovery, since aileron application may alter the spin characteristics to the degree that the spin is broken prematurely and that recovery is delayed.
Apply and maintain full rudder opposite to the direction of rotation.
As the rudder hits the stop, rapidly move the control wheel full forward and be ready to relax the forward pressure when the spin rotation has stopped.
As rotation stops, neutralize the rudder and smoothly recover from the dive. Normal recoveries may take up to 1½ turns when proper technique is used; improper technique can increase the turns to recover and the resulting altitude loss.
Further Advice on Spinning
Application of full aft control wheel and full rudder before the aeroplane stalls is not recommended as it results in large changes in pitch attitude during entry and the first turn of the spin.6
The recommended procedure has been designed to minimise turns and altitude loss during recovery.
In all spin recoveries the control column should be moved full forward briskly.7 This is vitally important because the steep spin attitude may inhibit pilots from moving the column forward positively.
The immediate effect of applying normal recovery controls may be an appreciable steepening of the nose down attitude and an increase in rate of spin rotation. It is essential to maintain full anti-spin rudder to continue to hold the control wheel full forward until the spin stops. The aeroplane will recover from any point in a spin in not more than one and one half additional turns after application of controls as recommended.
Improper application or delay in application of recovery controls can increase the number of turns to recover and the resulting altitude loss.
Delay in moving the control wheel forward may result in the aircraft suddenly entering a very fast, steep spin mode which could disorient a pilot. Recovery will be achieved by briskly moving the control wheel fully forward and holding it there while maintaining full recovery rudder.8
In certain cases the steep, fast rotation has developed into a spiral dive in which the rapid rotation continues, but indicated airspeed increases rapidly. It is important to recognize this condition. The aircraft is no longer auto-rotating in a spin and the pilot must be ready to neutralize the rudder so as to ensure that the airspeed does not exceed 129 MPH (Va) with full rudder applied.
Recovery to Level Flight
In most cases spin recovery will occur as the control wheel reaches the fully forward position. The aircraft pitches nose down quickly when the elevator takes effect and, depending on the control column position, it may be necessary to move the column partially back almost immediately to avoid an unnecessarily steep nose down attitude, possible negative “g” forces and excessive loss of altitude.
Because the aircraft recovers from a spin in a steep nose down attitude, speed builds up quickly in the recovery. The rudder should be neutralized as soon as the spin stops. Delay in neutralizing the rudder may result in yaw and “fish-tailing.” If the rudder is not neutralized it would be possible to exceed the maximum manoeuvre speed (Va) of 129 MPH with the surface fully deflected.
Normally the engine will continue to run during a spin, sometimes very slowly. If the engine stops, take normal spin recovery action, during which the propeller will probably windmill and restart the engine. If it does not, set-up a glide of 83 MPH and restart using the starter motor.
This Service Bulletin is to be kept with the aircraft paperwork at all times.
Install the placard provided with this Service Bulletin on instrument panel in full view of the pilot. Note: Peel protective cover from face of Placard.
Make appropriate log book entry of compliance with this Service Bulletin.
One (1) each Placard, Piper Part Number 87369-44.
Availability of Parts:
Placard enclosed. Additional copies of Service Bulletin 753, if required, are available from Customer Services, Piper Aircraft Corporation, Lock Haven, PA.
This Service Bulletin is effective upon receipt.
This information is submitted to owner/operators of the above referenced aircraft to assist in insuring proper operation of the aircraft.
Each pilot should be made aware of the importance of absolutely observing these procedures.
1 This document is reproduced in its original format dated December 15, 1982. All footnotes are inserted by Langley Flying School.
2 AFM meaning Aircraft (or Aeroplane) Flight Manual, or what is commonly referred to as the Pilot Operating Handbook.
3 Steep turns here being defined as turns in excess of 45° bank.
4 Note that solo spin training at Langley Flying School is prohibited.
5 Langley Flying School instructors typically enter normal spins from a level stalled condition.
6 Langley Flying School procedures are for the rudder to be first fully deflected prior to the stall, and for the stall to be effectively induced with aggressive but smooth full nose-up deflection on the control column—the sequence being “kick . . . pull.”
7 Langley Flying School procedures prescribe “smooth but aggressive” full-forward” movement of the control column—typically, the spin recovery becomes effective before full forward deflection is required. Note that in the event of an inadvertent spin with normal non-utility category loading, full and immediate forward movement of the control column will be required.
8 Again, forward movement should be smooth but aggressive, and the pilot must be prepared to input full deflection should recovery not be immediate—typically, however, recovery during spin training is soon as the control column begins the forward travel.