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Aviation History
1985
1985 - 1165.PDF
Israel plans Phantom update TEL AVIV Israel is to go ahead with the flight-test of a McDonnell Douglas F-4 Phantom with a Pratt & Whitney PW1120 engine. Initially the F-4 will fly with one PW1120 and one J79. Later it will flv with two PW1120s. If the PW1120 markedly improves the aircraft's performance, the Israeli Air Force's entire fleet of F-4s could be re-engined. The PW1120 is expected to give 6,0001b more thrust than the J79 and make the aircraft 2,0001b lighter—increasing acceleration and manoeuvra bility. A complete modernisation programme on the F-4s, including canards, headup displays, and smart weapon capability, plus new engines, could extend F-4 service life into the next century. The first flight-test, sched uled to take place later this year, will serve a double purpose because the IAI Lavi, Israel's new multi-role fighter, will also be fitted with the PW1120. • IAF Fouga CM. 170 Magis- ter trainers are also being modernised with strength ened airframes and refur bished cockpits. Higher harmonic control is tested STRATFORD Sikorsky is testing a higher harmonic control system (HHC) in an S-76 to try and reduce airframe vibration. The company says that it has reduced vibration by up to 90 per cent and claims that, theoretically at least, vibration can be reduced to an undetectable level. The harmonics being con trolled are the vibrations set up by the helicopter's main FLIGHT International, 20 April 1985 i ••'••' % USAF reviews flying kit A new Boeing " ,:-*i^B in ^•L • \ tactical life support system (TLSS) for pilots is being reviewed by the US Air Force. It elimi nates the need for liquid oxygen by providing air through an on board oxygen » *- generating 1 T^I •; 8>MiiflitiMgKtflfff¥ •••• .-mirfl •'',' 5^,. I ^iK system, and provides protection up to 9g, 60,000ft, and if 50°C. The suit 'jjj> • yf\ also protects W51; 'NW«W|SWj^i.*R^!jj!tf^jiajfelJ against chemical vW^F wT*fi«fi^»tffiliM'tfWnT'Pm*r 1M^>? iHttuBt'' r1 lilBiHM5?sHtL MHj i£l^^^^£ii •' Hi ' • • «ft»' ^Sflt! "'*iit H'!1'^ 11 i fit'tenf!'*'•''•»'?>i' -l!j'' r-'iiji'!,'! !]', iRwi^i^i':'i4Si<:-ii5^ 'i-1'^!1^-- and biological agents. The helmet, with special visors and goggles, protects against laser hazards, and nuclear flash. rotor. In a four-blade rotor the most important harmonics are the vibrations occurring at three, four, and five times each revolution of the rotor. These are partly caused by asymmetrical aerodynamic forces on the blades, particu larly at high airspeeds. The harmonics combine and are transmitted to the airframe through the rotor mast and transmission as a four-per- revolution vibration. For a main rotor speed of 300 r.p.m., this would have a vibrational frequency of 20 Hz. HHC gives a smoother ride, improve aircraft reliability, longer airframe life, and greater stability for weapons firing. It eliminates vibrations of the main rotor at source by slightly oscillating the pitch of the rotor blades, creating loads that are opposite and equal to the vibration-causing aerodynamic loads on the blades—so effectively cancel ling inherent vibratory loads. In the S-76 tests one rod in each of the three channels of the main rotor mechanical control system is replaced with an HHC actuator that drives the corresponding main hydraulic servo-mechanism to produce the vibration- cancelling motion of the rotor blades. The system has been tested at up to 150kt, and manoeuvres up to 2g. Sikorsky's Acap exceeds requirements WEST PALM BEACH The US Army/Sikorsky S-75 Advanced Composite Air frame Programme (Acap) helicopter, now halfway through its 37hr flight-test programme, is exceeding requirements. The tests are being carried out under contract to the US Army Applied Technology Laboratory, Fort Eustis, and it has been confirmed that the Acap helicopter is 23 per cent lighter than one made from metal. The Army requires a 22 per cent weight saving. There is also a 24 per cent airframe cost saving, based on 1,000 helicopters being produced at a rate of 14 per month, which compares favourably with the Army's requirement of 17 per cent. The Acap uses S-76 engines, transmission and rotors. During early flight tests it was flown at a gross weight of 8,4701b, at speeds up to 160kt, and manoeuvred at up to 2 • 5g. Ongoing tests include flight envelope expansion at high altitude, autorotations and DEFENCE single-engine flight, investi gation of handling qualities and performance, vibration surveys at various speeds and rotor torques, and electro magnetic compatibility of the composite structure with the aircraft's avionics. Flight-tests, which are on schedule, will end later in April, but follow-on pro grammes are being planned which will be relevant to all advanced technology air frames—in particular the US Army's LHX programme. wrangle resolved ST LOUIS McDonnell Douglas is paying Northrop $50 million as part of an agreement to end a six- year legal wrangle between the two companies. Northrop maintained that the companies had agreed that Northrop would handle sales of a land-based version of the F-18 while McDonnell Douglas would promote the naval version. Arguments began when the first export sale was of the naval version to the Canadian Armed Forces. All claims of both compa nies in the lawsuit have been dismissed. McDonnell Douglas has agreed to pay Northrop $50 million and MDC will be prime contractor for all customers for all present and future versions of the F-18— including any designed for land-based use only. McDon nell Douglas will also be licensor for any licensed prod uction. Northrop will be principal subcontractor to McDonnell Douglas for all F-18s and will participate in licensed prod uction and other programme commitments. McDonnell Douglas says that the payment to Northrop will be made promptly. The US Navy is seeking a $24 • 3 million repayment from F-18 payments to McDonnell Douglas because it claims the money was spent on legal costs over the F-18 dispute. McDonnell Douglas says it will pay back any money owed, but that the figure is $17 million.
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