The Syrian airfield prepare for reception of military aircraft of China
The latest news about fast emergence in borders of Syria of navy of China encouraged Syrians and res[...]
Other Systems
In early 1958, at the very height of the furor over the problems with the XLR99, a note of warning sounded for the General Electric auxiliary power unit (APU). On 26 March 1958 and again on 11 April 1958, General Electric notified North American of its inability to meet the original specifications in the time available, and requested approval
of new specifications. North American, with the concurrence of the Air Force, agreed to modify the requirements. The major changes involved an increase in weight from 40 to 48 pounds, an increase in start time from five to seven seconds, and a revision of the specific fuel consumption curves.50
By the end of the summer 1958, the APU seemed to have reached a more satisfactory state of development, and production units were ready for shipment.51 The early captive flights beginning in 1959 would reveal some additional problems, but investigation showed that the in-flight failures had occurred partially because captive testing subjected the units to an abnormal operational sequence that would not be encountered during glide and powered flight. Some components were redesigned, but the APU would continue to be relatively troublesome in actual service.
During the course of the X-l 5 program, many concerns were voiced over the development of a pressure suit and an escape system. Although full-pressure suits had been studied during World War II, attempts to fabricate a practical garment had met with failure. The
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Air Force took renewed interest in pressure suits in 1954 when it had become obvious that the increasing performance of aircraft was going to necessitate such a garment. The first result of the renewed interest was the creation of a suit that was heavy, bulky, and unwieldy; the garment had only limited mobility and various joints created painful pressure points. However, in 1955 the David Clark Company succeeded in producing a garment using a distorted-angle fabric that held some promise of ultimate success.51
Despite the early state-of-development of full-pressure suits, Scott Crossfield was convinced they were the way to go for X-l5. North American’s detail specifications of 2 March 1956 called for just such a garment— to be furnished by North American through a subcontract with the David Clark Company.55 A positive step toward Air Force acceptance of the idea occurred during a conference held at the North American plant on 20-22 June 1956. A full-pressure suit developed by the Navy was demonstrated during an inspection of the preliminary cockpit mockup, and although the suit still had a number of deficiencies, it was concluded that “… the state – of-the-art on full pressure suits should permit the development of such a suit satisfactory for use in the X-15.”54
After an extremely difficult and prolonged development process, Scott Crossfield received the first new MC-2 full-pressure suit on 17 December 1958 and, two days later, the suit successfully passed nitrogen contamination tests at the Air Force Aero Medical Laboratory. The X-15 project officer attributed much of the credit for the successful and timely qualification of the full-pressure suit to the intensive efforts of Crossfield.55
Fortunately, development did not stop there. On 27 July 1959, the Aero Medical Laboratory brought the first of the new A/P22S-2 pressure suits to Edwards. The consensus amongst the pilots was that it represented a large improvement over the earlier MC-2. It was more comfortable and provided greater mobility; and it took only 5 minutes to put on, compared to 30 minutes for the MC-2. However, it would take another year before fully-qualified versions of the suit were delivered to the X-15 program.56
While not directly related to the pressure suit difficulties, the type of escape system to be used in the X-15 had been the subject of debate at an early stage of the program; the decision to use the stable-seat, full-pressure – suit combination had been a compromise based largely on the fact that the ejection seat was lighter and offered fewer complications than the other alternatives.
As early as 8 February 1955, the Aero Medical Laboratory had recommended a capsular escape system, but the laboratory had also admitted that such a system would probably require extensive development. The second choice was a stable seat that incorporated limb retention features and one that would produce a minimum of deceleration.51 During meetings held in October and November 1955, it was agreed that North American would design an ejection seat for the X-15 and would also prepare a report justifying the use of such a system in preference to a capsule. North American was to incorporate head and limb restraints in the proposed seat.58
Despite the report, the Air Force was not completely convinced. At a meeting held at Wright Field on 2-3 May 1956, the Air Force again pointed out the limitations of ejection seats. In the opinion of one NACA engineer who attended the meeting, the Air Force was still strongly in favor of a capsule—partly because of the additional safety a capsule system would offer, and partly because the use of such a system in the X-15 would provide an opportunity for further developmental research. Primarily due to the efforts of Scott Crossfield, the participants finally agreed that because of the “time factor, weight, ignorance about proper capsule design, and the safety features being built into the airplane structure itself, the X-15 was probably its own best capsule.” About
the only result of the reluctance of the Air Force to endorse an ejection seat was a request that North American yet again document the arguments for the seat.59
The death of Captain Milbum G. Apt in the crash of the Bell X-2, which had been equipped with an escape capsule, in September 1956 renewed apprehension as to the adequacy of the X-15’s escape system.® By this time, however, it was acknowledged that no substantive changes could be made to the X-15 design. Fortunately, North American’s seat development efforts were generally proceeding well.’’1
Sled tests of the ejection seat began early in 1958 at Edwards with the preliminary tests concluded on 22 April. Because of the high cost of sled runs, the X-15 project office advised North American to eliminate the planned incremental testing and to conduct the tests at just two pressure levels—125 pounds per square foot and 1,500 pounds per square foot. The X-15 office felt that successful tests at these two levels would furnish adequate proof of seat reliability at intermediate pressures.62
Between 4 June 1958 and 3 March 1959, the X-15 seat completed its series of sled tests. Various problems, with both the seat and the sled, had been encountered, but all had been worked through to the satisfaction of North American and the Air Force. The X-15 seat was cleared for flight use.62
Another item for which the Air Force retained direct responsibility was the all-attitude inertial flight data system. It was realized from the beginning of the X-15 program that the airplane’s performance would necessitate a new means of determining altitude, speed, and aircraft attitude. This was because the traditional use of static pressure as a reference would be largely impossible at the speeds and altitudes the X-15 would achieve; moreover, the temperatures encountered would rule out the use of tradition pitot tube sensing devices. The NACA had proposed a “stable-platform inertial-integrating and attitude sensing unit” as the means of meeting these needs.64 A series of miscommunications resulted in the NACA assuming the Air Force had already developed a satisfactory unit and would provide it to the X-15 program.65 After it was discovered that a suitable unit did not exist, emergency efforts were undertaken to develop one without impacting the X-15 program. After a considerable amount of controversy, a sole-source contract was awarded to the Sperry Gyroscope Company on 5 June 1957 for the development and manufacture of the stable – platform.66 The cost-plus-fixed-fee contract, signed on 5 June 1957, was for $1,213,518.06 with a fixed fee of $85,000.67
In April 1958, the Air Force concluded that the scheduled delivery of the initial Sperry unit in December would not permit adequate testing to be performed prior to the first flights of the X-15. Consequently a less capable interim gyroscopic system was installed in the first two aircraft and the final Sperry system was installed in the last X-15.68
By the end of 1958, the two major system components (the stabilizer and the computer) were completed and ready to be tested as a complete unit. The systems were shipped to Edwards in late January 1959, and during the spring of 1959 plans were made to use the NB-52 carrier aircraft as a test vehicle.69 In addition, arrangements were made to test the stable-platform in a KC-97 that was already in use as a test aircraft in connection with the B-58 program.™ The first test flights in the KC-97 were carried out in late April.71 By June, North American had successfully installed the Sperry system in the third X-15 22 In January 1961, wiring was installed in the NB-52B to allow the stable-platform to be installed in a pod carried on the pylon under the wing. The first complete stable – platform system installed in the B-52 pod was flown on 1 March 1961, Since the B-52 was capable of greater speeds and higher altitudes than the KC-97, it provided additional data to assist Sperry in resolving problems being encountered with the unit.7’