Correlation of this failure with the data obtained from the flight recorder indicates that one elevator separated completely from the aircraft either just prior to the final dive or during the dive, presumably from excessive stresses as the pilot attempted to regain control and halt the rapid loss of altitude. The second elevator, while it did not separate from the aircraft, was found in a badly damaged condition due also to loads exceeding design capability. Examination by structural experts from the Amalgamated Aircraft Corporation, the Air Force and the Bureau of Safety disclosed that this elevator also failed to function due to stress failure of its hinge bolts only a few seconds after the other elevator departed entirely from the tail section.
All flight control systems have been carefully studied for indications of possible control malfunctions. Absolute continuity of control linkages and cables could not be established because of the extensive damage. However, there was no evidence of any control system failure or malfunction except those associated with elevator stress failure.
There was no evidence of arcing, burning or electrical overload on any of the generators. All available wiring bundles were examined for evidence of electrical arcing or beading but none was found. There was no evidence of a lightning strike on any of the wreckage. The venting in both wings was unobstructed and showed no fire damage. There was no evidence of internal wing tank fires prior to ground impact. As far as could be determined, there was no evidence of hail damage found on the nose section or the leading edges of the wing, tail or engine cowlings.
Selected but numerous samples of the aircraft wreckage were flown to the Federal Bureal of Investigation laboratory. These included the tail section and both elevators. No explosive residues were found and there is no reason to believe the aircraft was sabotaged. Further tests relative to this aspect, however, are continuing.
Examination of the engines disclosed that all four power plants were developing full thrust just before impact. There was no indication of engine malfunction. There also was no indication of a collision with another aircraft or birds. As far as could be determined, all fire damage resulted from impact with no evidence of an in-flight fire which might have contributed to or caused the accident.
It is evident from the flight recorder traces that in the final stages of flight the aircraft climbed steeply, reaching a climb rate about three and a half times its normal rate, pitched nose down and then dove toward the ground at high air speed. The Board of Inquiry, therefore, has concentrated its investigation on the possible cause or causes of this final maneuver and whether the structural failure of empennage components was due in part or totally to (1) the actions of the crew, (2) in part or totally to the severe turbulence, or (3) to a combination of the pilot-weather factors.
The Board considers it significant that the flight recorder readout was remarkably similar to those obtained after several previous accidents involving loss of control of large turbine-powered transports that encountered abnormally severe turbulence. In the majority of these incidents, the aircraft was caught in powerful updrafts and forced into an excessive rate of climb, accompanied by a sharp nose-up attitude. Coincident with crew attempts to maintain control was the encountering of sudden and equally powerful downdrafts. The latter occurred just at the moment when the control input was directed to bringing the aircraft’s nose down to a more level attitude in an effort to prevent a stall due to the excessive nose-up attitude and the subsequent loss of lift.
The introduction of a strong downdraft into a situation when the aircraft already was being trimmed to reduce altitude and to reverse nose-up attitude could have only one result—a sharp pitchdown and a subsequent dive challenging the skill and experience of any pilot in a recovery attempt.
The Board of Inquiry is convinced that this was the situation facing the crew of Air Force One, and such conviction is based not only on previous accidents occurring under similar circumstances, but on data furnished by the United States Weather Bureau which demonstrated beyond question that the turbulence encountered by the presidential aircraft was generated by a wind shear preceding a vicious line squall. Such wind shears usually involve violent, sharp gusts that can either be downdrafts, updrafts or a succession of both and with no warning when one might change to the other in a split second.
However, the Board has been unable to ascertain definitely whether elevator failure was due to turbulence alone. The flight recorder readout shows inconclusive but logical evidence that an unsuccessful attempt to recover control at least contributed to the structural disintegration and may have been the sole source of this failure. The violent pitchdown may have been the result of elevator separation following excessive gust stresses, but it is equally plausible to deduce that it also could have stemmed from the combination of updraft-downdraft conditions and the actions of the crew in combating this unexpected development.
In fact, the Board of Inquiry believes that the latter possibility is the more likely and logical probable cause of this accident. This belief should not be interpreted as criticism of the crew or the techniques followed. The Board, indeed, believes that the pilots were faced with hazardous circumstances which they were unprepared to meet.
he commander of Air Force One, Colonel Marcus Henderson, and the copilot, Major Samuel Foster, were veteran and able airmen who had demonstrated through numerous tests and check rides their unquestioned qualifications for the safe operation of an aircraft. Furthermore, both had extensive experience in flight operations involving severe turbulence.
In attempting an admittedly theoretical reconstruction of what events must have transpired in the cockpit of Air Force One, however, the Board investigated the background of these two fine officers. It was impressed by the fact that neither pilot had, as far as could be determined, any experience in operating a Condor under the severe turbulent conditions undoubtedly encountered by the presidential aircraft.
Because of the previous turbulence incidents involving swept-wing turbine equipment, there has been considerable emphasis placed by both the Air Force and the civil carriers on training crews to combat successfully even the most drastic conditions affecting aircraft control. The result has been a virtual cessation of loss of control incidents in recent years. Certainly, Colonel Henderson and Major Foster were exposed to this extensive training and the Board of Inquiry has been greatly concerned as to why such training apparently failed to prevent this accident.
In the course of this thus far brief but extensive investigation, the Board noted that Colonel Henderson and Major Foster were assigned to the presidential air fleet seven years ago when primary aircraft of that fleet was the Boeing 707-320, the long-range intercontinental model of the Boeing 707. Part of their qualifications for flying Air Force One was a six-week training curriculum at a major airline’s Flight Training Center, under a contract the carrier held for instructing all Air Force One pilots in the operation of Boeing transport aircraft.
The curriculum included intensive sessions in a 707320 simulator and the course placed particular emphasis on aircraft control techniques in severe turbulence. The utilization of a simulator enabled the instructors to re-create, almost as realistically as actual flight maneuvers, conditions identical to those encountered by Air Force One over Arizona. The Board of Inquiry further noted that, according to airline and Air Force records, Colonel Henderson and Major Foster had no difficulty in passing this or any other phase of the training program.
However, and the Board holds this to be of utmost importance, when the Air Force acquired the Amalgamated Condor for use in the presidential air fleet, no Condor simulator was available. All pilot qualification checks were conducted in the actual aircraft during actual flight. Only recently has a digital flight simulator been obtained for Condor crews, and there was no opportunity for either Colonel Henderson or Major Foster to receive simulator training before they were assigned to the flighty which ended in disaster.
Subsequent to the accident, special tests were run in the new Cond
or simulator which approximated, as nearly as could be determined, the weather and turbulence conditions encountered by Air Force One. These disclosed a previously unsuspected instability which the pilots undergoing the tests described as an oversensitivity of controls and a tendency to permit hazardous overcontrol. Fifteen pilots were tested as to their handling of a Condor affected by first a severe updraft, then an equally severe downdraft, followed by a violent pitchdown and a high-speed dive. Of the fifteen pilots, eleven imposed such large control displacements as to theoretically cause failure of the elevators along with possible failure of other empennage structure when they attempted to recover from the dive.
Under these conditions, with heavy control column forces presenting a difficult recovery problem, a pilot used to the normal sensitivity of the Condor’s control system would have a natural tendency to attempt to override the elevator control column load and such overriding, at a critical stage of the recovery, could well lead to structural failure. Loss of elevator effectiveness during a high-speed dive is particularly characteristic of T-tail aircraft.
It seems evident that in the case of Air Force One the rapidly decreasing air speed even as the rate of climb increased sharply, combined with a high nose attitude, prompted the crew to take drastic action to prevent what would appear to be an impending stall. Acting on this concern, and quite probably while being subjected to severe vibrating accelerations from the turbulence, the pilots used full down elevator and aircraft nosedown stabilizer trim to change the aircraft’s flight path.
Although these large control displacements would have the effects of arresting the speed decrease and high climb rate and, would return the aircraft attitude to near level, they also would develop extremely high negative G forces approximating the weightlessness of a space flight. Such forces would result in a chaotic situation in the cockpit of any aircraft exposed to forces of this type and magnitude.
Besides the distraction of warning lights and ringing bells which were probably activated under the negative G conditions, loose items such as briefcases, charts, logbooks, etc., would be tossed around. The crew members would be forced upward against their belts and the average pilot unquestionably would have difficulty keeping his feet on the rudder pedals and his hands on the control yoke.
It was at this moment that Air Force One probably was exposed to a sudden and violent downdraft—at a time when control forces were reduced to zero or even reversed and the pilot’s hands were off the yoke as a result of the high negative G effects. Under these circumstances, with the control column remaining in full forward or nosedown position, a steep dive was inevitable.
The Board of Inquiry feels justified to theorize that, when the pilot managed to place his hands on the control yoke some eight seconds later, the aircraft was in a vertical dive and air speed was building up rapidly with an accompanying loss of elevator effectiveness.
The Board is convinced that a final recovery attempt was made at this precise moment, resulting in excessive loads on the elevator structure and failure due to inadvertent overapplication of the controls. Such overapplication, as the special simulator tests demonstrated, was most possible and even likely in an aircraft whose normal control forces were the most sensitive of any large transport aircraft built.
The Board of Inquiry at this stage of the investigation can find no reason to apply the verdict of pilot error to this tragedy or to attach any blame whatsoever to the crew. Rather, the Board believes that both crew and aircraft were exposed to a set of extremely hazardous circumstances which neither were equipped to handle, the pilots in terms of experience and the aircraft in terms of structural strength.
The Board also emphasizes, however, the tentative and preliminary nature of these findings. The investigation is continuing and a full report will be issued at a later date when evaluation and analysis of all available evidence is concluded.
General Coston held a news conference immediately after distribution of the Board of Inquiry report, and the wisdom of this decision was confirmed by the first question from a worried-looking Washington Post reporter.
“General Coston,” he asked, “would you care to put the Board’s verdict into language the layman can understand?”
“Just what don’t you understand?” Coston said pleasantly. “I refer, sir, to the second paragraph listing the probable cause of the accident. I quote: ‘the unfavorable interaction of severe vertical air drafts and large longitudinal control displacements resulting in a longitudinal upset’ and so forth. I wonder, General, if you could put this into plain English. Because frankly, sir, I don’t know what the hell the Board’s talking about.”
“Well, it means that Air Force One went out of control in severe turbulence,” Coston answered with a kind of resigned patience. “It went into a dive and, in attempting to recover from the dive, too much force was applied to the controls and the elevators failed.”
“General, that seems to imply pilot error, doesn’t it?” the Chicago Sun-Times man asked.
“No, it does not. The Board of Inquiry report makes it clear that the crew was blameless. Henderson was faced with a problem he couldn’t solve. The problem was not of his making.”
“Of whose making was the problem?” the AP pressed. “The problem was a combination of many factors. I don’t think you can boil them down and pinpoint the blame on any single factor.”
“I’m not talking about blaming a factor, General,” said the AP. “If you won’t tag the crew with pilot error, what individuals would you blame? The people who built the Condor? Air Traffic Control? The Weather Bureau? The Air Force for accepting a plane with, let’s see, the report referred to it as a ‘previously unsuspected instability’?” Coston took a firm grip on his self-control. “In an accident of this sort, there’s really no single cause and therefore no single area of blame. It was the result of a chain of unfortunate circumstances. For example, I personally believe that if Colonel Henderson had had the advantage of simulator training in the Condor he would have been able to cope with the situation. The lack of simulator training was a matter of not being able to obtain the necessary hardware soon enough. The White House was anxious to utilize the Condor as a presidential aircraft and it was put into presidential service before a Condor simulator was built.”
“Did Colonel Henderson or the other pilot ever express any concern about the Condor’s handling characteristics in turbulence?” That one was fired by Pitcher.
“Colonel Henderson, I understand, preferred the old Air Force One. The Boeing 707. But it’s natural for most pilots to prefer one aircraft over another. Most of his flight experience had been on Boeings and he liked the plane.” Coston peered suspiciously at the questioner. He remembered Pitcher’s probing from the first news conference.
“Well then, let me rephrase my question. What was the source of Colonel Henderson’s preference for the 707., as opposed to the Condor?”
“Source? He just liked the Boeing better. You might like a Lincoln better than a Cadillac, or a Chewy more than a Plymouth. It’s pretty difficult to spell out a pilot’s likes and dislikes, just as it’s hard for a driver to explain exactly why he prefers one car over another.”
“General, you’re evading—”
“I’m not evading anything, sir,” the general snapped.
“—you’re evading the question. I’ll rephrase it again, General. Was Colonel Henderson’s dislike for the Condor—”
“Just a minute. I never said he disliked the Condor. I said he would rather have flown the Boeing.”
“I’ll rephrase it for the third time,” Pitcher persisted. “Was Colonel Henderson’s preference for the 707 ever reflected in any official report to the Air Force? Did he ever complain to his superiors about the Condor?”
“Colonel Henderson made no official representations to the Air Force concerning the safety of the Condor.”
“Did he ever make any unofficial representations?”
“In private conversations with other of
ficers, I’m told, he expressed his preference for the Boeing.”
“In those conversations, did he say why he’d rather fly the President around in a 707 instead of a Condor?”
“You’re asking me to give hearsay evidence,” Coston protested. “To quote Colonel Henderson secondhand. It seems more pertinent to me, as chief of the Air Force, that Henderson never submitted official complaints about the Condor. I think, sir, you might let others ask some questions.”
“He’s doing fine,” someone in the back of the room said loud enough to paint a flush of anger on Coston’s face. There was an embarrassed, uneasy pause before the New York Times put the next question.
“Is the Air Force going to obtain another Condor as a replacement?”
“I don’t know. We’d have to ask Congress for the money. That decision hasn’t been reached yet. I don’t think it’s even been discussed. Right now, we’re going to use the Condor’s predecessor as the primary presidential aircraft. Temporarily, of course.”
“As chief of staff, would you recommend purchase of another Condor?” Pitcher would not let go.
“My feelings on this matter were expressed before we bought the Condor. I thought Air Force One should be a supersonic transport. Congress thought otherwise. I still believe the President’s long-range aircraft should be an SST.”
“That belief is based on your desire for a faster plane? Or is it based on how you feel about the Condor’s safety?” The Star had taken up Pitcher’s cudgels.
“It’s ‘based on the speed factor, not on safety,” Coston replied testily.
“General, are there any plans to ground the Condor?” the UPI wanted to know.
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