CG and spins
Avoid imitations
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Most real world stall spin accidents occur at such low altitudes that if the airplane IS ALLOWED to enter far enough into a spin that spin recovery techniques must be used as opposed to a stall recovery, then they would not have enough altitude to recover.
If the pilot is not good enough to recognize when the airplane is departing controlled flight I highly doubt that he/she will be actually be able to use training on recovery from a spin.
Personally I think most spin training outside of aerobatic training is negative training because pilots have to hold into spin control inputs through at least 1 turn before classic spin recovery control inputs should be used. Instead training should emphasize control of yaw in the event of a unintended stall. No airplane will spin if yaw is controlled at the point the wing stalls
If the pilot is not good enough to recognize when the airplane is departing controlled flight I highly doubt that he/she will be actually be able to use training on recovery from a spin.
Personally I think most spin training outside of aerobatic training is negative training because pilots have to hold into spin control inputs through at least 1 turn before classic spin recovery control inputs should be used. Instead training should emphasize control of yaw in the event of a unintended stall. No airplane will spin if yaw is controlled at the point the wing stalls
I had intentionally spun gliders several times before I started my SEL training. Shortly after solo I asked my instructor if we could do some spins. He said no, went and got some spin training, then said yes.
My ASW-19b took full rudder and full opposite aileron to provoke a spin entry. Never could keep it rotating. I never could get the ASW-28 to even start to spin. Neither allowed spins with ballast so could not explore what either did where it really mattered (trying to scratch away without dumping). Both were really well behaved and I never came close to an inadvertent spin entry in either. A fellow club member had a scare when his LS-4 snapped into spin entry during a low altitude save. Another club member died recently after stalling his Standard Cirrus in a low altitude save.
I was against the elimination of spin training. I don't think anyone who has not experienced that first half turn really understands how quickly it can happen.
Avoid imitations
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It’s been many years since I instructed on RAF fixed wing SEP aircraft but my recollection is that RAF CFS teaching was that anything beyond 360 degrees of undemanded roll or 180 degrees of undemanded yaw was no longer considered “incipient” and required full spin recovery actions. But maybe that was just the Bulldog.
Awareness, understanding and recognition of the conditions under which a spin will occur
will make spin training obsolete.
Similar to driving a car, literally millions of people have never gotten into a skid without having done any slip/skid pad training.
Understand that an airplane will NEVER spin unless stalled first.
Avoid the stall, avoid the spin.
I used to ask my students what the way was to avoid a bar fight……don’t enter a bar.
will make spin training obsolete.
Similar to driving a car, literally millions of people have never gotten into a skid without having done any slip/skid pad training.
Understand that an airplane will NEVER spin unless stalled first.
Avoid the stall, avoid the spin.
I used to ask my students what the way was to avoid a bar fight……don’t enter a bar.
I've been told that spin characteristics are defined not just by CofG location, but by weight distribution, such as a lump of lead added in the tail. Is there any validity in this comment, or is weight distribution totally taken into account by knowing CofG location
Correct. C of G is a very important factor, and spin recovery characteristics will drive C of G limits. But the moment of inertia can have an effect too. If you put a small mass wayyyy back, yet remain within C of G limits overall, the spin recovery could be affected, as there was more inertia to overcome for recovery.
Last edited by David J Pilkington; 11th Mar 2022 at 08:05. Reason: Fix quotes
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Another club member died recently after stalling his Standard Cirrus in a low altitude save.
We are evolving into a stage in GA where modifications are more common, and multiple modifications a factor too. It is a sad oversight that mod upon mod(s) are stacked up on airplanes, perhaps in the effort to modernize legacy types, and the inter relationship is overlooked, or poorly considered. Sure, the gross weight increase is STC'd, but was it considered for compliance (spin characteristics) when combined with other mods - like tip fuel tanks (Flint) or extra wing tanks (Monarch)? The now longer range plane, with the gross weight increase, will probably say that the weight above a certain weight must be carried as fuel (for landing weight considerations), but has anyone properly evaluated the changed handling characteristics (spin recovery) at a higher weight, and with fuel weight further away from the C of G (by span, rather than fuselage station)? Might you be flying a multi mod plane, and not be entirely aware of the compliance of the combined mods? The first clue would be: If there is not a flight manual supplement which relates all of the aerodynamic/weight/power mods to the airplane in ONE flight manual supplement, it's likely that you're flying a plane which has not had the combination correctly reviewed together. Each STC tells the installer to consider the relation of each mod to the others, but it is often not done, and if done, not completely done. Your Cessna 210 gets several mods installed together, does the installation shop require that the plane be test spun for confirmation of compliance following multi mods? Rarely, though I have done it for shops following major mods.
When you get in an unmodified certified single engine plane, you know that it has compliant spin recovery characteristics, whether spin approved or not. Once you install more than one mod on it, that assurity of handling characteristic compliance goes way down. The flight manual supplement will be your clue - if it does not describe the compliance of the modified configuration you're flying, beware!
So, though BPF and I do not entirely agree about spin training, I will certainly agree that it should be taught by an aerobatic or spin competent instructor, and treated as a practiced emergency procedure, not something which is "fun", unless aerobatics is your fun, in which case, get trained properly, and go for it. But I do feel that every pilot should be exposed to an incipient spin entry and recovery, just to bring understanding. After that, yes, train avoidance, as long as that training promotes stall recovery by application of nose down elevator (as opposed to adding power) and highlights the need to keep the ball in the middle all the time.
No airplane will spin if yaw is controlled at the point the wing stalls
I've flown a few homebuilt types which had a pretty unforgiving stall, I've flown a couple of horribly rigged planes, that would rather spin than stall, no matter how centered the ball is maintained, and I've flown a few antique types with no washout in the wing (DC-3) who have an unforgiving stall. But, yes, generally, keeping the ball in the middle is the best step toward preventing a spin entry. Thereafter, don't accidentally stall it! And, be aware, is the type of flying you're about to do a higher risk? Turns during aerial photography or ground observation at slower speeds, tightening a turn to base or final, or low speed parachute jump runs, where jumpers are going to gang up on the outside of the plane before departing...
Avoid imitations
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Strange how the brain can begin to dust off some of its old pages. I recall that the old Jet Provost 3 wasn’t allowed to be aerobatted or spun if there was any fuel in the tip tanks and if that was part of the sortie profile it was normal to take off with “half tips” so they would be empty by the time you climbed to minimum entry altitude. One of the pre spinning checks was to confirm that the main gauge reading had begun to decrease. At least I think that’s correct…..it’s 44 years since I last flew one and a year longer since I nearly killed myself by inadvertently flick rolling then spinning one inverted from a badly botched aerobatic manoeuvre (had I not previously recovered from one in a C150 as mentioned earlier I might not be here writing about it).
A similar cockup in a JP (Strikemaster in fact) may well have been a factor in the sad demise of an ex Harrier display pilot of my acquaintance, quite some years later.
A similar cockup in a JP (Strikemaster in fact) may well have been a factor in the sad demise of an ex Harrier display pilot of my acquaintance, quite some years later.
The moment of inertia was demonstrated by famed test pilot Janusz Żurakowski in the Meteor, vertical climb to zero airspeed, close one throttle, allow the aircraft to rotate in yaw through 540° back into a vertical dive and recover, the maneuver required a load of under wing rockets to give it the necessary angular momentum to get through the 540°. Earned the name "Zurabatic Cartwheel".
A not very good video starting at 2:20
A not very good video starting at 2:20
Last edited by megan; 11th Mar 2022 at 13:06.
I'm going to guess that the "save" was not entirely successful, if the outcome was fatal...
We are evolving into a stage in GA where modifications are more common, and multiple modifications a factor too. It is a sad oversight that mod upon mod(s) are stacked up on airplanes, perhaps in the effort to modernize legacy types, and the inter relationship is overlooked, or poorly considered. Sure, the gross weight increase is STC'd, but was it considered for compliance (spin characteristics) when combined with other mods - like tip fuel tanks (Flint) or extra wing tanks (Monarch)? The now longer range plane, with the gross weight increase, will probably say that the weight above a certain weight must be carried as fuel (for landing weight considerations), but has anyone properly evaluated the changed handling characteristics (spin recovery) at a higher weight, and with fuel weight further away from the C of G (by span, rather than fuselage station)? Might you be flying a multi mod plane, and not be entirely aware of the compliance of the combined mods? The first clue would be: If there is not a flight manual supplement which relates all of the aerodynamic/weight/power mods to the airplane in ONE flight manual supplement, it's likely that you're flying a plane which has not had the combination correctly reviewed together. Each STC tells the installer to consider the relation of each mod to the others, but it is often not done, and if done, not completely done. Your Cessna 210 gets several mods installed together, does the installation shop require that the plane be test spun for confirmation of compliance following multi mods? Rarely, though I have done it for shops following major mods.
When you get in an unmodified certified single engine plane, you know that it has compliant spin recovery characteristics, whether spin approved or not. Once you install more than one mod on it, that assurity of handling characteristic compliance goes way down. The flight manual supplement will be your clue - if it does not describe the compliance of the modified configuration you're flying, beware!
So, though BPF and I do not entirely agree about spin training, I will certainly agree that it should be taught by an aerobatic or spin competent instructor, and treated as a practiced emergency procedure, not something which is "fun", unless aerobatics is your fun, in which case, get trained properly, and go for it. But I do feel that every pilot should be exposed to an incipient spin entry and recovery, just to bring understanding. After that, yes, train avoidance, as long as that training promotes stall recovery by application of nose down elevator (as opposed to adding power) and highlights the need to keep the ball in the middle all the time.
No modern certified and properly rigged airplane will spin if yaw is controlled......
I've flown a few homebuilt types which had a pretty unforgiving stall, I've flown a couple of horribly rigged planes, that would rather spin than stall, no matter how centered the ball is maintained, and I've flown a few antique types with no washout in the wing (DC-3) who have an unforgiving stall. But, yes, generally, keeping the ball in the middle is the best step toward preventing a spin entry. Thereafter, don't accidentally stall it! And, be aware, is the type of flying you're about to do a higher risk? Turns during aerial photography or ground observation at slower speeds, tightening a turn to base or final, or low speed parachute jump runs, where jumpers are going to gang up on the outside of the plane before departing...
We are evolving into a stage in GA where modifications are more common, and multiple modifications a factor too. It is a sad oversight that mod upon mod(s) are stacked up on airplanes, perhaps in the effort to modernize legacy types, and the inter relationship is overlooked, or poorly considered. Sure, the gross weight increase is STC'd, but was it considered for compliance (spin characteristics) when combined with other mods - like tip fuel tanks (Flint) or extra wing tanks (Monarch)? The now longer range plane, with the gross weight increase, will probably say that the weight above a certain weight must be carried as fuel (for landing weight considerations), but has anyone properly evaluated the changed handling characteristics (spin recovery) at a higher weight, and with fuel weight further away from the C of G (by span, rather than fuselage station)? Might you be flying a multi mod plane, and not be entirely aware of the compliance of the combined mods? The first clue would be: If there is not a flight manual supplement which relates all of the aerodynamic/weight/power mods to the airplane in ONE flight manual supplement, it's likely that you're flying a plane which has not had the combination correctly reviewed together. Each STC tells the installer to consider the relation of each mod to the others, but it is often not done, and if done, not completely done. Your Cessna 210 gets several mods installed together, does the installation shop require that the plane be test spun for confirmation of compliance following multi mods? Rarely, though I have done it for shops following major mods.
When you get in an unmodified certified single engine plane, you know that it has compliant spin recovery characteristics, whether spin approved or not. Once you install more than one mod on it, that assurity of handling characteristic compliance goes way down. The flight manual supplement will be your clue - if it does not describe the compliance of the modified configuration you're flying, beware!
So, though BPF and I do not entirely agree about spin training, I will certainly agree that it should be taught by an aerobatic or spin competent instructor, and treated as a practiced emergency procedure, not something which is "fun", unless aerobatics is your fun, in which case, get trained properly, and go for it. But I do feel that every pilot should be exposed to an incipient spin entry and recovery, just to bring understanding. After that, yes, train avoidance, as long as that training promotes stall recovery by application of nose down elevator (as opposed to adding power) and highlights the need to keep the ball in the middle all the time.
No modern certified and properly rigged airplane will spin if yaw is controlled......
I've flown a few homebuilt types which had a pretty unforgiving stall, I've flown a couple of horribly rigged planes, that would rather spin than stall, no matter how centered the ball is maintained, and I've flown a few antique types with no washout in the wing (DC-3) who have an unforgiving stall. But, yes, generally, keeping the ball in the middle is the best step toward preventing a spin entry. Thereafter, don't accidentally stall it! And, be aware, is the type of flying you're about to do a higher risk? Turns during aerial photography or ground observation at slower speeds, tightening a turn to base or final, or low speed parachute jump runs, where jumpers are going to gang up on the outside of the plane before departing...
What training has to emphasize is developing the muscle memory so that if the airplane starts to depart controlled flight there is the instinctive push forward on the stick and application of rudder opposing the yaw. I stand by my contention that there are no airplanes that a reader of this forum is likely to fly where this technique will not always avoid a spin entry. However some unforgiving airplanes will give you very little time to intervene so the stall recognition and recovery is especially important.
Finally I would suggest a practical definition of a “spin” is where classic stall recovery control inputs will not recover the airplane and indeed will exacerbate the situation. Only spin recovery inputs will recover the airplane. However I have never seen an airplane that will not recover with a conventional stall recovery technique if the stall recovery inputs are correctly and forcefully applied before the airplane has completed more than 180 degrees of yaw after departing controlled flight.
Avoid imitations
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But some aircraft may initially produce undemanded roll, rather than yaw at the incipient stage. Hence the RAF teaching, which was that if there was any autorotation with buffet, immediately centralise the controls, which should stop it developing. If the yaw subsequently continued beyond 180 degrees, or the aircraft continued to roll in excess of 360 degrees, the full spin recovery technique should be used.
Having said that, during formation “tailchasing”, we found that it was easy to manoeuvre the Bulldog very rapidly by briefly inducing autorotation…but of course that wasn’t officially taught because we weren’t supposed to flick roll that aircraft.
I did once experience an inadvertent high rotational spin when my student messed up a roll off the top manoeuvre. He was slow to sort it out and so I took control and applied full pro spin control followed by the normal spin recovery technique and it recovered very rapidly (to the extent that the rugby playing student was so alarmed that he squeaked)!
Having said that, during formation “tailchasing”, we found that it was easy to manoeuvre the Bulldog very rapidly by briefly inducing autorotation…but of course that wasn’t officially taught because we weren’t supposed to flick roll that aircraft.
I did once experience an inadvertent high rotational spin when my student messed up a roll off the top manoeuvre. He was slow to sort it out and so I took control and applied full pro spin control followed by the normal spin recovery technique and it recovered very rapidly (to the extent that the rugby playing student was so alarmed that he squeaked)!
I would suggest a practical definition of a “spin” is where classic stall recovery control inputs will not recover the airplane and indeed will exacerbate the situation.
However I have never seen an airplane that will not recover with a conventional stall recovery technique if the stall recovery inputs are correctly and forcefully applied before the airplane has completed more than 180 degrees of yaw after departing controlled flight.
I think it is important to note this thread started with “ in the Private Pilot Course” . My comments are in relation to that. When I teach aerobatics the instruction is much more nuanced as there are many ways to depart controlled flight that would not apply to PPL training. Aerobatic airplanes also have high control authorities that add extra complexity ( eg into vs out of spin aileron inputs).
I believe that “spin training” in the PPL is negative training as pro spin controls have to held in for at least a full turn before the spin recovery is initiated. There are no times in non aerobatic flight that pilots should deliberately apply and hold pro spin control inputs.
In addition a lot of stall and spin training is very artificial. In the real world you don’t get into a stall by first doing a HASEL check and then slowly pitching up until the airplane stalls. Personally I like to present stall spin avoidance with scenario’s that emulate real world accidents, like the base to final skidded turn or the panic turning pitch up when you think you are not going to clear the trees on a short field takeoff.
I believe that “spin training” in the PPL is negative training as pro spin controls have to held in for at least a full turn before the spin recovery is initiated. There are no times in non aerobatic flight that pilots should deliberately apply and hold pro spin control inputs.
In addition a lot of stall and spin training is very artificial. In the real world you don’t get into a stall by first doing a HASEL check and then slowly pitching up until the airplane stalls. Personally I like to present stall spin avoidance with scenario’s that emulate real world accidents, like the base to final skidded turn or the panic turning pitch up when you think you are not going to clear the trees on a short field takeoff.
a lot of stall and spin training is very artificial. In the real world you don’t get into a stall by first doing a HASEL check and then slowly pitching up until the airplane stalls. Personally I like to present stall spin avoidance with scenario’s that emulate real world accidents, like the base to final skidded turn or the panic turning pitch up when you think you are not going to clear the trees on a short field takeoff.
Scenario teaching is the way we should be going in my view, in all things. However I encounter a very strong, even a dismissive attitude to it in working groups.
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What training has to emphasize is developing the muscle memory so that if the airplane starts to depart controlled flight there is the instinctive push forward on the stick and application of rudder opposing the yaw. I stand by my contention that there are no airplanes that a reader of this forum is likely to fly where this technique will not always avoid a spin entry. However some unforgiving airplanes will give you very little time to intervene so the stall recognition and recovery is especially important.
I have never seen or witnessed any evidence supporting 'muscle memory' in response to an unexpected stall or spin. There are a number of signs for the pilot to learn that indicate that the conditions for a stall are imminent and require avoidance action. Ex 10a in the UK and EASA syllabus is meant to deal with this but unfortunately has never been standardised and is poorly understood.
Somatosensory information and instinct should be treated with care. In regard to the stall and spinning Beggs and Mueller are a valuable read.
Somatosensory information and instinct should be treated with care. In regard to the stall and spinning Beggs and Mueller are a valuable read.
Last edited by Fl1ingfrog; 12th Mar 2022 at 21:36.
FLingfrog
I have certainly used muscle memory in gliders. Last year I was flying the club PW5 and trying to core a very narrow thermal. To do that I was flying at minimum speed and high bank angle to minimize my turning circle. I was momentarily distracted by a radio call and inadvertently let the airspeed drop a few knots which caused the glider to stall. The stick went forward without conscious thought and then stepping on the rudder stopped the yaw. I flew out of the thermal under control after losing less than 100 feet.
I do believe that the instinctive pitch down if the airplane surprised you with an inadvertent stall can be taught. Finally most airplanes will talk to you when they are getting slow and at high AOA. I make a point of demonstrating the so called “soft stick” and get pilots to maneuver in slow flight so that they recognize the change in control forces.
I guess I have hijacked the thread so back to the OP’s question. As a previous poster noted the effect of aft C of G can be significant in gliders but less so in your typical powered trainer. However most trainers that are cleared for spinning have a more restrictive C of G envelope for spins. This will result in the aft C of G limit being moved farther forward in order to eliminate undesirable or even dangerous spin characteristics.
I have certainly used muscle memory in gliders. Last year I was flying the club PW5 and trying to core a very narrow thermal. To do that I was flying at minimum speed and high bank angle to minimize my turning circle. I was momentarily distracted by a radio call and inadvertently let the airspeed drop a few knots which caused the glider to stall. The stick went forward without conscious thought and then stepping on the rudder stopped the yaw. I flew out of the thermal under control after losing less than 100 feet.
I do believe that the instinctive pitch down if the airplane surprised you with an inadvertent stall can be taught. Finally most airplanes will talk to you when they are getting slow and at high AOA. I make a point of demonstrating the so called “soft stick” and get pilots to maneuver in slow flight so that they recognize the change in control forces.
I guess I have hijacked the thread so back to the OP’s question. As a previous poster noted the effect of aft C of G can be significant in gliders but less so in your typical powered trainer. However most trainers that are cleared for spinning have a more restrictive C of G envelope for spins. This will result in the aft C of G limit being moved farther forward in order to eliminate undesirable or even dangerous spin characteristics.
