THE WORD ON PITCH-UP

e [Music] since Century series Fighters have become operational the term pitch-up has become common and widely spread in the Air Force unfortunately the complete story of pitch up has not kept pace with wild rumors concerning the phenomenon the result some pretty weird interpretations of pitch up among Century series fighter pilots this film is intended to clarify the phenomenon as it applies to Flying the voodoo series aircraft let's begin by saying that pitch-up is definitely an undesirable trait it's easy to steer clear of or to recover from but anyone who shrugs it off unknowingly as no sweat is just plain [Music] crazy it's only fair to point out that the operational analyst is right in saying that pitch-up does not reduce the Tactical capability of the weapon system any more than does the stall [Music] boundary and the engineer is also right when he says that aerodynamically restriction due to pitch up is a small price to pay for advantages gained in weight savings performance trimfree flying qualities and maneuver ing [Music] capability in the final analysis however it's up to the pilot to get the job done getting the most from the aircraft without overextending yourself into problem areas is simple once you know and understand the full story on Pitch [Applause] up first let's look into why pitch up occurs on any swept wi aircraft approaching stall the center of lift moves forward as the wing tips stall out causing a nose-up pitching [Music] moment in bringing the aircraft closer to stall we are also increasing angle of attack which results in Greater downwash forces on the tail this also increases nose up tendencies [Music] these phenomena have been described in the past as tucking stick lightning dig in or stick reversal call it what you like but it still nose up pitching moment and it affects the f101 like any other swept-wing aircraft as the voodoo approaches stall the wing tip Vortex moves in board and increases in intensity as the angle of attack increases when this vortex action reaches that portion of the wing which influences the tail it imparts such a strong downwash component on the horizontal stabilator that it not only contributes to pitch up but also renders the stabilator ineffective as an immediate recovery device now that we know why the voodoo pitches up how do we know we're approaching critical regions the key lies in the term angle of attack from a practical standpoint everything your airplane does is based on angle of attack it takes off at a known angle of [Music] attack it fli Final Approach at another known angle of attack and it pitches up at a known angle of attack the angle of attack is that angle formed between the relative wind vector and the longitudinal Axis or you could say the Ang angle formed by the direction in which the airplane is moving and the direction in which the airplane is pointing angle of attack is affected by gross weight indicated air speed and g- loading the easiest way to visualize how we change angle of attack is to vary one item at a time leaving the other two constant first let's vary weight holding stabilized flight the airplane requires enough lift to offset its weight and since lift is a function of angle of attack it will take a certain angle of attack to produce 40,000 lb of lift for these flight conditions as weight decreases as would be the case when fuel is burned down the airplane requires less lift to maintain the same flight conditions therefore angle of attack will be reduced conversely as we add weight to our example aircraft we must increase angle of attack to give us the required additional lift this shows that the heavier the aircraft the closer it is flying to its stall angle of attack for any given flight condition we can theoretically continue to add weight until the wing has reached its limit capability at which time it will [Music] stall now let's very indicated air speed keeping all other conditions constant lift as we pointed out before four is also a function of indicated air speed as the airplane is slowed down lift will be decreased unless angle of attack is increased to maintain it this is obvious to the pilot during an acceleration from slow to high indicated air speeds at the start of the run the aircraft is in a fairly nose high high angle of attack attitude as speed increases the nose High attitude decreases which shows that less angle of attack is needed to produce the same lift at the higher indicated air speed now let's vary g-loading which actually means we're right back to varying weight a 40,000 lb airplane required 40,000 lb of lift to keep at Airborne at 1G flight if we go into a 3G turn the 40,000 lb airplane now weighs three times as much and requires 120,000 ,000 lb of lift with other conditions held constant increased angle of attack is required to produce this added lift this increase is shown by the back pressure required to hold constant altitude in the turn the pitch-up and spin programs consisted of over 200 fully instrumented intentional pitch ups in the f11a andv aircraft fulls scale pitch up and successful recoveries were demonstrated from low subsonic to Super Sonic speeds from combat ceiling down to 10,000 ft altitude early in the f11a program recovery techniques were developed which were proved 100% successful further verification of this technique was obtained in the f101b program and the many pitch ups resulting from flight test development programs which required flight near and through the pitch up boundary the actual pitch-up coverage shown in this film was photographed from a ground tracking camera therefore no Horizon reference is available these tests reveal that the voodoo demonstrates three basic modes of stall performance after the critical angle of attack is exceeded the voodoo must pitch up before it can enter any type of stall or spin gyration recovery from Pitch up is 100% effective with a shoot however without a shoot the aircraft will probably progress into the second phase prior to [Music] recovery this is the so-called incipient spin which can also be thought of as a poststall pre-spin gyration at this stage the airplane oscillates about all axes and while looking like a violent ride you don't feel high abnormal forces if handbook recommended action with drag shoot is used recovery is again 100% effective however if a shoot is not utilized time out of control will be lengthened considerably with resultant increase in altitude loss extended outof control time could possibly force you to leave the aircraft prior to recovery because of altitude [Music] consideration remember if you use the handbook recovery techniques at pitch up which in includes use of the drag shoot you'll never reach incipient spin if the shoot fails to deploy the aircraft control action is exactly the same chances of recovering without the shoot are best within the first few seconds following the peak of pitch-up therefore complete knowledge of pilot control action is imperative since improper use of controls without the shoot can prolong the out of control time or even prevent recovery the airplane can can only get into the steady state spin mode if it is put there through use of Rudder and aerons and it's got to go through pitch-up and poststall gyration stages both of which are fully recoverable before it can get into the third or steady state spin stage McDonald Pilots ran a program in which Voodoo in normal trim for various flight conditions were placed in full scale pitch-up after which all controls were returned to neutral in every case the aircraft recovered from the resulting incipient spin without a shoot which shows that the 101 does not inherently seek steady state spin after pitch-up but rather tends toward recovery the only recovery control to expedite the recovery cycle is full forward stick with neutral aerons and Rudder as soon as you feel the nose coming up on its own keeping Rudder and aerons neutral start that stick forward toward the instrument panel chances are that you might still have stabilator Effectiveness for immediate recovery and you'll never get into full scale pitch up if the aircraft continues into fullscale pitch-up the stick is now properly positioned for pitch-up Recovery if the nose continues up even with full forward stick deploy the drag shoot after reaching the peak of pitch up don't worry about air speed since it will be well below 200 knots at the peak of the pitch maneuver during the pitch up or subsequent recovery don't try to control yaw or roll remember neutral ailerons and ruers Recovery is almost immediate however it is possible that recovery will be affected in a slight yaw which will produce a roll since One Wing will recover slightly ahead of the other if this happens don't use counter roll control action as the forward stick starts producing slight negative G's control should be returned smoothly to neutral even though the aircraft might still be rolling any rolling action will stop on its own without pilot action smoothly maintain between zero and 1 g in a dive and slowly roll the wings to level it is recommended that the shoot be retained in the dive until it fails between 200 and 250 knots this is not detrimental to aircraft structure in any way also the aircraft should be held in its recovery dive until 350 knots before a pull out is attempted once you're in a full scale pitch up don't hesitate to use your shoot you can't tell from aircraft action how far you are from recovery so don't kid yourself into thinking it looks like it's about to recover so I'll just save my Shute besides the handbook States the Chute will be used so it's not really a matter of pilot [Music] option for the no shoot recovery condition the recommended control action Remains the Same as negative G is sensed during recovery the stick must be returned to neutral even though the aircraft might still be rolling after angle of attack has recovered yawing and rolling oscillation will damp out within a few seconds on their own the best chance of recovery without a shoot is shortly after the peak of pitch up but aircraft control action is of the utmost importance because if the full forward stick is not removed it will drive the aircraft through recovery and stall it under negative G if this occurs the aircraft will snap roll which will again cause angle of attack to increase out of control for this reason the stick must be brought to neutral as negative G is sensed if the choot isn't used after you reach the peak of pitch up the aircraft will probably yaw strongly in either direction as the nose falls through the Horizon followed by some rolling action if recovery is not affected at this time the yaw and rolls will change direction and rate and the nose will oscillate relative to the Horizon this is characteristic of poststall gyration and all you can do is to stay loose and concentrate on proper recovery controls [Music] sure it's a wild ride but even without the shoot you have an excellent chance of recovery if you play it cool and ride it out with proper control action applied however don't get so absorbed in the maneuver that you neglect to monitor the minimum safe recovery altitude there is no aircraft configuration which will speed up recovery from pitch-up or poststall gyration it is therefore advisable to affect recovery with gear flaps and speed brakes retracted external tanks will not affect recovery the engine will stall on initial pitch up and stay that way until recovery is affected don't try afterburners as a recovery device they won't deliver power and are likely to torch behind the airplane burning off the drag shoot if in use also don't throttles to idle since this action can place the engines in a stall condition which can persist even after aircraft recovery unless after burners were on at pitch-up the recommended throttle action is leave them alone altitude loss is a difficult matter to discuss since there are many varying situations such as altitude at pitch-up was shoot deployed altitude at recovery [Music] gross weight dive attitude at recovery altitude required for dive recovery however here are some fundamentals during poststall gyration the airplane drops about 18,000 ft a minute average outof control time with shoot is 4 seconds control will be gained in a dive so altitude for dive recovery must be considered dive recovery charts show that from the worst possible condition a 90° dive at 200 knots it takes 6,000 ft to achieve straight and level flight starting at 10,000 ft 9,000 ft to recover from 20,000 and 12,000 to recover starting at 30,000 ft average altitude loss for drag shoot recoveries to level flight was obtained from a study of all pitch ups recorded a pitch up from 40,000 ft requires 10,000 ft to regain level flight from lower altitude pitch ups the altitude required for Recovery to level flight becomes progressively less so much for Recovery techniques now how do we stay away from it all the rules boil down to our earlier discussion of angle of attack the heavier the gross weight the less G you can pull for a given indicated air speed and the slower the indicated air speed the less G you can pull for a given gross weight disregarding pitch Control Systems the airplane itself gives adequate Buffet warning below .9 indicated mock num warning of approach to critical angles of attack supersonically where no Buffet warning is available the knee pad cards show the number of G's you can pull for a given indicated air speed it's an easy rule of thumb to remember know it [Music] well of course you must consider pitch rate the voodoo represents a lot of mass and once that mass is in upward motion inertia gets into the act the faster you rotate the greater the inertial overshoot tendency will be in short smooth control action is mandatory Don't Force the voodoo around fly it smoothly finally there's airs speed bleed off to be familiar with when you look at your indicated air speed to determine how many G's you can pull in a turn remember that the added induced drag of the turn will start that air speed unwinding unless power is added or altitude lost to compensate for it as the indicated air speed bleeds off so does your G potential so don't back yourself into [Music] trouble well that's it in order to get the optimum operational capability from your aircraft you've got to know all its characteristics good and bad if you as a pilot know these characteristics you will know and respect pitch up as applied to the voodoo and it will never cause you trouble