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Aviation History
1970
1970 - 1069.PDF
fLIGHT International, II Sum 1970 979 ounce) specimen was found to contain 20 times as much uranium, thorium, and potassium as any other lunar rock. A group of Nasa and university scientists in the US and UK has been selected to analyse it further and samples of this rare rock are now under investigation. The team is composed of principal investigators whose interests are in isotope analyses and age-determination of all lunar samples. The work of the group is being supported by mineralogy and trace- element studies. The preliminary examination at the LRL further revealed that the rock had a texture readily distinguishable from both the breccia and igneous rock samples. Colour variations on the surface of the rock suggested that the rock was macroscopically (visible to the eye) non-homogeneous. First results, determined by the international team, indicate that the rock has an apparent age of 4,600 million years, while other rocks from the Apollo 11 and 12 sites appear to have crystallised from an igneous liquid that was formed between 3,300 and 3,700 million years ago. Isotope studies on the lunar soil and breccia samples indicate that they may have been derived from rocks as old as 4,400 million years, but no specific age can be inferred from these results. The Apollo 12 specimen is essentially identical in age with the date of formation that has been observed for most meteorites. The time of formation of stone meteorites is widely accepted as a time of formation of the planets and even of the Sun. Nasa researchers state: "It now appears that we have recovered from the surface of the Moon a sample that dates back almost to the formation of the solar system. We conclude from this that some parts of the surface of the Moon must have remained essentially unchanged since that time. The exact origin of the sample cannot be established at present, but it seems likely that it may have come from a highland area or from the rocks that underlie the Mare region. In the latter case, it could have been transported to its present location by the impact that formed the crater Copernicus." Continued from pace 973 may be maintained that a large jet at 4,000ft makes relatively little noise but this is relative to the number of such overflights at a busy airport. The inbound noise problem is almost as acute as the departure one, especially as modern engines seem to generate more noise than one would expect during partial-power opera tion. Obviously, the best approach is to leave the power at idle thrust for as long as possible; depending on the type of aircraft this may be safely left until between 3,000ft, 914m and 2,000ft, 609m. Theoretically one could arrange things so that, with no ATC restrictions, and a clearance to land in advance, the IAS would be continually reducing to allow gear and flaps selection at the last safe time to stabilise the final approach in the "slot," and to trim the aircraft, spool up engines, and adopt the correct target approach IAS. The pilots who attempt this fall into two categories—successful, or dead. Some margin for error, windshear, engine spool-up time, and not least of all crew drills, must be allowed. Most pilots are used to running their final approach sequences at specific IAS, either as a general procedure, or on request by ATC, and can keep IAS well up to the outer marker. Thus it is often required by ATC that higher powers are needed than those necessary. It is also often the case that stepdown clearance is given by thousand-foot stages to an ILS glideslope joining.height of 2,000ft. Each time power is increased to stabilise at the cleared height, more noise is generated. It goes without saying that most pilots fly the intermediate approach with the minimum drag-producing excrescences dangling. The gear is left till the glideslope, and flaps left as long as possible, depending on IAS required. Use of full landing flap before crossing the outer marker is unnecessary, and thrust requirements can be minimised this way. Those types that need a long time to stabilise and set up autocoupling, and plug in auto-throttles may well prove more noisy as they often need a longer run in on the ILS to achieve a good result. Airspeed must be well controlled in the latter stages of the intermediate approach before glideslope inter section if a high/fast approach with decaying airspeed at low height is to be avoided. The essence of all this is that there must be some short period of flight where adjustments can be made. This will inevitably produce some more noise. The more ATC inter ference with the optimum idle-thrust descent path, the more noise there will be. The best arrangement of feeding from holding fixes will allow aircraft to be left at relatively high levels, with idle power, at speeds high enough to operate with clean configuration. 250kt, 461 k.p.h. seems ideal for the current generation. A vertical profile of 600ft per mile, or approxi mately at 6° descent angle, is practicable. Other higher rates call for steep nose-down body angles, and drag increments from spoiler, air brake, gear or flap, or even reverse thrust. We should leave these configurations for reserve use, especially as there are so many differing aircraft deceleration and drag performance characteristics. At London, for example, we could leave the Garston VOR happily at FL100 for the runways 10, and make less noise, but not for runways 28, though the mini mum flight level of 50 could well be increased to 80. Most inhibitions to less noise on the approach stem from the traffic separation and density problems. We need to increase the upper TMA at London to cope with this sooner or later, and to join the glideslope with enough distance to the runway to allow speed and thrust adjustments from a virtually idle- thrust intermediate approach. Pilots will continue to co-operate to avoid excessive noise generation, but will also expect procedures to be more care fully tried out before being adopted. The accuracy of some of the navigational aids refining minimum-noise departure rout ings is not perfect. VOR radials in particular seem to be prone to fluctuation. The UK would do well to adopt 250kt, 461 k.p.h. below FL100 as a maximum for both arrival and departure. Noise can shatter wine glasses, damage buildings, and even split ear drums. Not so well known is the fact that it can actually set things on fire. This glass-wool wedge was pari of the noise lining of a siren test tunnel used by a British aircraft company for acoustic fatigue- testing of airframe structures. The wedge was reduced to cinders after ten minutes of very high-frequency noise at !62dB. The glass was later replaced by steel wool
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