FLIGHT WITHOUT A FIN

for I am Lieutenant Colonel Schmidt from the bomber section of the directorate of Aerospace safety at Norton Air Force Base California you are about to see and hear a most unusual story about the aircraft you fly a story that has made aviation history we at the directorate of Aerospace safety believe the factors of this incident will increase your understanding of B52 flight characteristics and heighten your appreciation of its capabilities the aircraft involved was a b-52h on loan to the Boeing Company its flight crew members were Mr Charles fiser instructor pilot Mr Richard Curry pilot Mr Leo Kors co-pilot and Mr James Pitman Navigator here to tell you this remarkable story firsthand is one of the Boeing pilots who is at the controls Mr Richard Curry dick thank you Colonel Smith our mission was to conduct a flight load survey to obtain and record the structural loads encountered on a routine low-level sorty special instruments were installed in the cockpit to record the stresses exerted on various parts of the aircraft an 8-hour flight was scheduled along a route running from wiah Kansas Southwest to the Rocky Mountains the mission called for 10-minute runs at 280 350 and 400 knots calibrated air speed at 500 ft above the ground utilizing the lowlevel mode of the autopilot the initial portion of the flight progressed as planned with only light turbulence encountered at the end of the sixth leg however as the aircraft turned North in the vicinity of Wagon Mound New Mexico and began a course parallel to the mountains the instruments identified here in Orange began indicating increasing turbulence and heavy gust loads on the tail section we elected to discontinue the low-level portion of the flight and the aircraft was climbed to 14,300 Ft main sea level where the air was relatively smooth we then decided to continue the mission using the next speed schedule of 350 knots since the terrain elevation was steadily increasing the aircraft flight path was approximately 1,000 ft above above and slightly to the right of East Spanish peak near agular Colorado wind at this time indicated 62 knots West component but no turbulence was noted then at 345 knots while accelerating to 350 knots an area of extreme turbulence was encountered it lasted approximately 9 seconds with this model I will attempt to show you approximately what happened to the aircraft when it was struck by this turbulence the turbulence came in Rapid explosive like gusts the airplane was pitched up and yawed to the left followed immediately by a very rapid yaw to the right and a resultant right rolling moment this motion was opposed with Approximately 80% left wheel Authority a high frequency vibration was felt in the rudder pedals and Rudder pedals displacement gave no response the elevator response was also very poor the crew was alerted to prepare to abandon the aircraft however we soon realized that the aircraft still had marginal control at this time the air brakes were raised to position one to improve longitudinal stability and a fuel transfer was started to maintain a forward center of gravity lateral control was aided by very small asymmetric power settings which helped maintain the aircraft in a sid slipping flight attitude after the aircraft was brought under marginal control we call for assistance the first to arrive was at boing B F100 this is what the pilots saw approximately 83% of the vertical fin had been ripped away we immediately set a course for Witchita Kansas and developed our flight strategy boing flight test had already recommended that the F main gear be lowered as this would be a stabilizing Factor in the absence of the vertical fin any drag after the center of gravity would tend to stabilize the aircraft here the outboard air brakes are at position four which is also an area after the center of gravity here our air speed is about 210 knots indicated which is about 30 knots above the minimum recommended for this weight with flaps up small excursions up to 2 120 and down to 200 knots were made however 210 knots was found to be most satisfactory at this time the altitude was approximately 12,000 ft meain Sea Level the center of gravity was calculated to be about 19% with the vertical fin missing the weight of the vertical fin is estimated to be about 2,000 lb due to the reports of unfavorable weather at Witchita it was finally decided to divert us to bville Air Force Base Arkansas where surface winds were more favorable while in the bville area making preparations for landing we were advised to extend the tip protection gears first then the forward trucks were lowered a yawing oscillation occurred during forward gear extension however this ceased when the gear reached a down and loock indication we reduced air speed to 160 knots at 10,000 ft and prepared for a long flat Final Approach hoping to be able to flare and touch down at the same speed 160 knots flap approach speed was selected in order to obtain Optimum body angle we had computed a no drag shoot stopping distance of 5,000 ft here is the aircraft dong Final Approach 160 knots outboard Air bres at at position four all engines are near idle crossing the threshold still at 160 knots the aircraft started a slight left drift and we decided not to hold off any longer but put it on the runway at touchdown all air brakes were raised to position six we elected to use the drag shoot but decelerated to 130 knots before deploying it we considered the possibility of a goar around and had it been necessary we would have used out board air brakes at number six position this is the B-52 F bville Air Force Base shortly after landing this aircraft was flown 5 hours in this configuration from the scene of the incident over Colorado to witcha and then to bille Air Force Base Arkansas a portion of the aircraft's original Mission was to record the gust loads found in moderate turbulence however the loads we encountered were much greater than had been anticipated an analysis of the recorded information revealed gust loads of a greater magnitude than had ever previously been recorded on any large aircraft well Colonel I guess that about sums it up thank you dick we at the directorate of Aerospace safety are indeed grateful to you for bringing us this firsthand report a review of the data collected on this flight indicates that the airframe design criteria for future heavy air aircraft should be re-evaluated and possibly revised for future aircraft design an engineering change to incorporate additional strength in the B-52 EMP is well underway at Witchita in conclusion let us review the things which enabled this air crew to return this aircraft to a safe landing excellent crew coordination to regain positive control of the aircraft a call for Chase aircraft a call for expert technical assistance reduction of air speed to 30 knots above minimum recommended flaps up proper use of air brake settings with inboard air brake circuit breakers pulled transfer of fuel for better aircraft stability extension of the AP main gear only for directional stability and judicious use of throttles for desired power settings for Optimum controlability We Salute this Boeing flight test crew for a fine job of airmanship by bringing this aircraft back they have supplied the Air Force with invaluable data on the gust load velocities that are often imposed on large aircraft flying low-level missions salutes also to the other agencies and the Boeing Company for their excellent cooperation