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Aviation History
1975
1975 - 0796.PDF
714 F-15 EAGLE the remainder at much lower speed, giving a much more solid feel during the landing run. The modifications and changes of standard since first flight have put the structure weight up by about 4501b to 27,0001b. At nominal combat weight, with missiles spent but half fuel and full ammunition remaining, the wing- loading is about 541b/sq ft. The nominal maximum speed of Math 2-5 at altitude is set by engine limitations and at low altitude the q limit (the ability of the structure to with stand aerodynamic loads in "thick" air) is 800kt. With 30 F-15s built and ten delivered to the USAF's first operational squadron at Luke AFB, the company has begun to investigate growth versions. The initial emphasis is on providing more fuel and McDonnell has designed and flown on its own initiative special externally mounted bodies, known as a Fast (fuel and sensor, tactical) packs. These are really multi-purpose conformal containers, fitting snugly into the wing-fuselage junction. Two Fast packs, one each side, can add 10,0001b of fuel to the internal capacity of 11,3001b, and were used on the TF-15 which last September flew from Loring AFB, Maine, to Bent- waters in England for its demonstration at Farnborough and later at Ramstein in Germany. For the ferry flight the No 2 TF-15 weighed 66,0001b, exactly half this weight comprising fuel (normal gross weight is 54,0001b) and it took off in less than 3,500ft. In addition to the Fast pack three 600 gal tanks were carried for the 5-2hr flight. (On this exercise, incidentally, 92 flights in Europe were made for a total of 100 flight hours, the maintainability averaging 4-25 man-hr/flight-hr.) In addition to carrying fuel, Fast packs can be used for specialised missions calling for reconnaissance, ECM, thrust-augmentation and many other types of equipment. The extra drag is said to be only one-quarter that of con ventional external tanks of the same volume. McDonnell Douglas foresees a requirement for a FOI (follow-on intercepter) mission, studied over seven years ago by the USAF under the designation IMI (improved manned intercepter). This may be still some way away, and undoubtedly exports of the F-15 will hinge upon its future success as a multi-purpose fighter-bomber. It was of course a foregone conclusion that somebody would want to use the Eagle as a bomber, notwithstanding the vociferous anti- air-to-ground lobby. Over the years the importance of the ground-attack mission has become recognised and 571b has been given over in structure and equipment for this role. The large, lightly loaded wing is not directly compatible with long airframe life or pilot comfort at very low levels and McDonnell is therefore investigating modifications which will bring the F-15 into line with customer-built aeroplanes. Chief of these is the addition of a vertical accelerometer mounted at the centre of gravity and signal ling to the wing-flap actuators in such a way that when an upward gust is sensed, the flaps move upwards to decrease the lift coefficient of the wing. The existing hydraulic actuators would be replaced by standard aileron actuators which provide the rapid response necessary to prevent the aircraft from reacting to the disturbance. A couple of years ago, when financing difficulties were throwing doubts on the future of the F-14, Congress directed the US Navy to study a deck-landing version of the McDonnell fighter designated the F-15N. Agreement was eventually reached on the F-14, which removed the immediate pressure to investigate the F-15N in detail and there is now no direct outlet for this version. McDonnell has teamed with Northrop to propose the F-17 as the US FLIGHT International, I May 1975 F-15 TIME-TO-HEIGHT RECORDS During a number of flights from January 16 to February 1 this year an F-15 flying from Grand Forks AFB, North Dakota, set up eight official world time-to-height records in an exercise known as Project Streak. The details are as follows and are given inthe order: altitude in metres, time in seconds, previous record-breaking aircraft, its time in seconds, date of previous record: 3,000m 27-57sec, F-4, 34-5sec, February 21, 1962; 6,000m 39-33sec, F-4, 48-8sec, February 21, 1962; 9,000m 48-86sec, F-4, 61-7sec, March 3, 1962; 12,000m 59.38sec, F-4, 77-1sec, March 1, 1962; 15,000m 7704sec, F-4, 114-5sec, March 3, 1962; 20,000m 122-94sec, MiG-25, 169-8sec, June 4, 1973; 25,000m 161 02sec, MiG-25, 192-6sec, June 4,1973; 30,000m 207-80sec, MiG-25, 243-9sec, June 4,1973. Navy's Air Combat Fighter, and would be the prime con tractor in the event of that design being selected. The decision by the US Navy on its choice of fighter is expected in the autumn. Development cost of the USAF programme is expected to run out at $1-9 thousand million, of which the airframe and radar programmes between them account for $1-1 thousand million, the balance going to Government- furnished equipment such as the M61 gun, the engine and some of the avionics. The annual F-15 budget is about $1 thousand million a year, which provides for a production rate of nine aircraft a month at a fly-away cost of $7-5 million in January 1975 dollars (this includes about $2-9 million of GovernrnenMurnished equipment, most of it going on the engines at aibout $1-1 million apiece). Earlier this year the company proposed to the USAF the purchase of more F-15s as an alternative to the F-16, chosen last January by the Air Force as its Air Combat Fighter. It argued that further acquisitions of an aeroplane now way down the learning curve, and with training and support organisations already in existence, will be more economic than the acquisition of a new and less capable fighter. Under the most conservative proposal, delivery of an extra 200 aircraft over the original 729 (pushing the total up to 12 a month) could begin next year at an average fly-away cost of $6 -8 million. At the other extreme, an extra 600 aircraft could be built at an average fly-away cost of $6-2 million, beginning next year, with a monthly rate totalling 18 aircraft. At a rate of nine a month, the existing 729-aircraft programme will be completed in 1982. At present the most likely export customer is Israel, which has asked the US Government for F-15s. The State Department has not yet given its decision and will probably not do so unless the balance of power is considered to be seriously disturbed in favour of the Arab countries. It would be surprising if these new fighters were still absent from the Middle East and elsewhere in the next five years. F-15 LEADING DATA Span 42ft lOin Length 63ft 10in Height 18ft 7in Empty weight 27,000lb Normal max take-off weight (full internal fuel, four Sparrows,680 rounds of ammunition) 40,000lb Gross take-off weight (three 600gal external tanks, no other stores) 54,000lb Demonstrated take-off weight (three 600gal tanks, two Fast packs) 66,000!b Ferry range (three 600gal tanks) approx 2,500 n.m.
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