cOCKPIT CLASSROOMBy Harold Holmes

HISTORY OFSPINS

I n reading about the history of aerobat-ics, and especially the history of spins,in Acrobats In The Sky by John W.Underwood (1972) it is apparent thatwhat was called the "spiral dive" in theearly 1900's was one of the dark mys-teries of aviation. In September 1911,Avro (British) test pilot Fred Raynhamattempted to fly through a patch of fogand got into what was then known as a"spiral dive". In 1911 the term "tailspin"had not yet appeared in the glossary ofaeronautics. According to early spin his-tory, others had the same horrifying ex-perience, invariably fatal, but Raynhamsomehow managed to recover control."What caused this strange mystery, noone knew; some supposed it was sim-ply an act of God," (Underwood 1972).

According to early historical accountsof spinning following Raynham's nearcrash, another Englishman found him-self in the same terrifying predicament."Lt. Wilfred Parke of the Royal Navy hadinitiated a power-off spiral descent for alanding in his biplane (Avro) which fellinto a spin to the left. Lt. Parke's firstimpulse was to get the nose up. Instinc-tively he added power, hauled back onthe wheel and applied full left rudder,the latter action being the acceptedmethod in dealing with the incipientside-slip. It was all to no avail; if any-thing the spinning accelerated. ButParke kept his head while centrifugalforce was pressing him toward the rightside of the cabin. Once he realized thatit was the spinning, not the diving, thathad to be checked, Parke applied rightrudder and the spinning stopped allow-ing Parke to recover just 50 feet fromthe ground," (Underwood 1972).

Since Parke's spin recovery, whichhad been witnessed by several obser-vers, it was important to record thisepisode for the benefit of fellow airmenwhile the details were still fresh. Accord-ing to Underwood, the report publishedby FLIGHT in August 1912 promulgatedthe first rule for spin recovery: APPLYRUDDER OPPOSITE TO THE DIREC-TION OF ROTATION. This soundsfamiliar, doesn't it? Entitled Parke'sDive, it evoked widespread interest andprompted the Royal Aero Club tosuggest further experimentation.

Another term which cropped up dur-ing the early days of flying was the term48 FEBRUARY 1985

"tailspin". Lincoln Beachey, who hadbuilt the famous Little Looper was sup-posed to have invented the term"tailspin" around the year 1915. Thereseems to be some confusion in the rec-ords whether Beachey actually per-formed the spin.

In the early days of flying, the tailspinwas a common and dangerous prob-lem. Then it was described as "an un-controlled, rotating dive earthward bythe airplane and the motion resemblesa corkscrew being drilled into a bottle.Now called simply a SPIN, it resultswhen the aircraft is severely and fullystalled but it actually begins when onewing stalls ahead of the other one withthe aircraft then falling off in the direc-tion of the first wing. (This could hap-pen, for instance, in a poorly coordi-nated steep turn.) The second wing,

DIAGRAM 1

having more lift, ends up chasing theother one. As the plane descends, fullystalled, it rotates around its center ofgravity, usually in a nose down attitude."This is an early description of a spin(Aerospace Encyclopedia).

Spin instruction and spin recoverytechniques were just beginning to be in-troduced in the United States in 1917.Some of the early pioneers (Under-wood) were Gilbert G. "Gil" Budwig, acivilian flight instructor at Chanute Field,Illinois, Harold T. "Slim" Lewis, EddieHubbard, Mike Brown, Eddie Stinson,Lloyd Bertaud and E. Hamilton Lee.Stunt flying was prohibited in the U.S.Air Service up to 1917, however, inSeptember 1917 Hubbard, Brown andBudwig were assigned to teach a newcourse called "Basic Battle Acrobacyand Trick Flying." Each American train-ing center class was given a week'straining in stalls, spins, loops, barrelrolls and chandelles (Underwood1972). The "acrobatics" were performedin WWI Jennies.

Shortly after the outbreak of WorldWar I, the subject of spinning began tocome up during hangar flying sessions.At this time in history, a spin was con-sidered an extremely dangerous ma-neuver, however, a spinning airplanemade a poor target in a dogfight. "Anewly graduated LT. E. V. Ricken-backer, who loathed the thought of spin-ning, decided that there would be anadvantage to be able to do it. He hadmuch influence in getting spins intro-duced into the military flight training pro-grams," (Underwood 1972).

It is interesting to note that WWIaerobatic terminology had a strongFrench accent; "the Vrille' was a spinand a Virage' was a tight turn. The 'rein-versement' came to be known as the'split-S'. The 'barrel roll' of 1918 was a'snap-roll'; today it is a form of aileronroll," (Underwood 1972).

During WWI, an alarming number offatalities were being caused by invertedspins in certain aircraft, notably the RAFCamel. Pilots who, according to earlyrecords, had survived the inverted spinexperience only through trial and errortechniques.

After the end of WWI came a newconcern for aviation safety. For in-stance, an investigation of 13 Camel ac-cidents revealed that 10 had involvedinverted spinning. Many different the-ories for the causes of these accidentswere presented by investigators. Onebelief was that once in an inverted spin,it could not be checked. A program oftesting was initiated late in an invertedspin, it could not be checked. A programof testing was initiated late in 1919 todetermine the truth about inverted flight.The puzzle was soon to be solved. Lt.Joyce, an American, and T.F.N. Ger-rard, a British Naval pilot with muchCamel time, had discovered, through

DIAGRAM 2

desperate manipulation of the controls,that pulling the stick back instead ofpushing it forward, as in a normal spinrecovery, was the only inverted spin re-covery technique. A report entitled TheManeuvers of Inverted Flight, pub-lished by the Aeronautical ResearchCommittee, disspelled many miscon-ceptions regarding inverted flight follow-ing the flight testing program.

Spin research has been conductedon a continuous basis since the early1900s and even today, the stall/spinhas been cited as a causal factor in 30%of all fatal general aviation accidentsaccording to NASA. A NASA report alsoindicates that the aircraft designer doesnot currently have a reliable means ofdetermining stall/spin characteristicsprior to prototype flight tests. This infor-mation, I would think, would be espe-cially important for the amateur builderof a sport airplane. In recognition of thisproblem, NASA is continuing its effortsin the conduct of an extensive stall/spinresearch program at Langley ResearchCenter.

Some of the conclusions of NASA re-searchers is vital safety information forall pilots. One important finding byNASA, important for pilot training pro-

grams is that for recoverable spins,normal recovery controls (rudderagainst the spin followed by downelevator) provided the fastest re-coveries (NASA Report, 79-1786). Outof a total of 529 spins performed usinga low-wing research airplane, theystudied spin characteristics rangingfrom slow and steep to fast and flat, andin 16 cases the spin recovery parachutewas required to recover the airplane.

Their findings in general indicatedthat deflecting ailerons with the spin(rolling into the spin) steepened the spin(reduced the angle of attack); deflectingailerons against the spin (rolling out ofthe spin) flattened the spin — increas-ing the angle of attack. Eric Muller, fol-lowing hours of spin tests, made somesimilar observations in his article TheSpin — Myth and Reality. He men-tions that using ailerons against the spinrotation makes the aircraft spin faster.Muller, in addition, points out that mov-ing the stick forward also results in anincrease in the rotation rate. Eric alsostates that the earliest method of gettingout of a spin when disoriented is toclose the throttle, remove the hands offthe stick and kick full opposite rudder(see Diagram 2).

SPORT AVIATION 49

DIAGRAM 3

Another interesting point concerningthe NASA spin tests were the spin entrycombinations of normal, acceleration,roll, pitch, yaw and power. The spin ineach case was identical after 1 or 2turns regardless of entry conditions.

Spin recoveries by NASA test pilotswere attempted by reversing rudder andthen elevator (normal recovery con-trols), by simultaneously reversing rud-der and elevator, by neutralizing con-trols, by reversing rudder alone and byreversing elevator alone. In all casesnormal recovery controls providedthe quickest recovery from moder-ately flat spins. Neutralizing controlsproduced the slowest recoveries. Re-versing elevator alone would not re-cover the airplane. For most of the air-craft tested when recovery was attempt-ed by reversing the rudder alone, the

airplane would recover from left spins,but not from right spins. To check forslipstream effects, a 6-turn spin wasperformed with the propeller stopped.No changes were noted in the left orright turn recovery characteristics(NASA 1979).

Spin Recovery Theories"In the majority of airplanes, the rud-

der is the principal control for spin re-covery. Powerful control of sideslip athigh angles of attack is required to ef-fect recovery during a spin. Since theeffectiveness of the vertical tail is re-duced at large angles of attack, the di-rectional control power necessary forspin recovery may produce a critical re-quirement of rudder power," (Aerody-namics For Naval Aviators 1965).

"Recovery can be achieved fairly eas-ily with application of full rudder oppo-

site the direction in which the plane isspinning. This slows rotation. Then, withrudder pedals neutralized, the stall itselfmust be broken by forward pressure onthe elevator controls. With the plane stillin a dive, final recovery to straight-and-level flight must be gradual until all ofthe controls become effective again.Power must be off during recovery,"(Bennet 1968).

Gene Beggs (EAA 80005) stated inhis article Aerobatics With BeggsSPORT AVIATION 1984, that "the mostimportant spin emergency spin recov-ery method is:

1. Cut the throttle2. Take your hand off the stick3. Kick full opposite rudder until the

spin stops4. Neutralize rudder and pull out of

the dive"The FAA Flight Training handbook,

AC 61 -21A (p. 157), states that any timea spin is encountered, regardless of theconditions, the normal spin recovery se-quence should be used (see Diagram1):

1. Retard power2. Apply opposite rudder to slow

rotation3. Apply positive forward-elevator

movement to break stall4. Neutralize rudder as spinning

stops and5. Return to level flight

In recent weeks I have had theunique opportunity to experience eachof these spin recovery techniques withWoody Woods. Up until recent months,I only knew of one spin recoverytechnique and that was the spin recov-ery sequence which I learned in theNavy flight training program. Obviously,there is still some disagreement overspin recovery techniques among highlyexperienced pilots and various aviationagencies. Continuing spin research isstill needed. Nevertheless, spin trainingis important and every pilot should beable to recognize when an incipient spincondition exists, and take prompt actionto prevent a fully developed spin and toknow the proper technique from a fullydeveloped spin either inverted or up-right. FAA says that performance on apilot flight test is considered unsatisfac-tory if more than one turn of a spin oc-curs or if it becomes necessary to lakecontrol of the airplane to avoid a fullydeveloped spin. In the few articles inSPORT AVIATION Woody Woods andI will present our thoughts and experi-ences in spinning Cessna 172s and152s as well as the aerodynamics ofspins.

If you wish to contact the author foradditional information, please writeHarold Holmes, 1038 Inverrary Lane,Deerfield, IL60015.

50 FEBRUARY 1985