Thirty-odd years later, the A380 – the widest commercial airliner available today with seating for 525 passengers – will be entering into service. It is another testament to Airbus’ commitment to innovation and intelligent design. Therefore, Airbus came to Brüel & Kjær for the development of a transducer they could invariably use to measure sound pressure in limited spaces during flight-testing and where flush mounting of conventional microphone/preamplifier combinations would be impossible or cause undesired side effects.
After multiple prototypes, all of which were rigorously tested by Airbus, the Surface Microphone Type 4948 was born – a flat, small, robust, accurate and stable microphone designed especially for aerospace applications and usable up to 165 dB. Verification trials proved that the microphone could withstand all the requirements demanded of transducers mounted outside an aircraft during flight, including but not limited to de-icing detergent, turbulence, hailstorms, rain, high g levels, a temperature range from –50˚C to 100˚C, cruising altitudes of 30 000 feet, and mach 0.8.
True to their commitment, Airbus continues to utilise the surface microphone in their flight-testing programme – years after its development.
Flying the Design
Flight-testing takes place at Airbus’ Toulouse testing site. It is here the company’s various research and design labs submit prototypes to validate aircraft design and performance characteristics. The individual design teams decide the test criteria, including where to place test sensors. The test engineers at Toulouse then determine the test methods and parameters as well as the types of sensors to be used.Above and below: Surface microphones mounted on an Airbus wing for flight testing
To monitor thousands of design parameters Airbus has over 15 000 transducers of different types: acoustic, vibration etc. Their acoustic transducers are used for various applications, including interior noise and exterior noise. For the approximately 200 surface microphones on hand, their robustness, dynamic range and mounting flexibility make them especially suited for acoustic fatigue analysis.
Acoustic fatigue analysis investigates a component’s material properties for weaknesses under acoustic stress. Results help designers choose suitable materials and help determine the lifecycle of individual components to ensure aircraft safety. There is always one model per aircraft family at the Toulouse site to perform regular acoustic fatigue tests.
To test for acoustic fatigue, surface microphones are mounted on the surface of the structure, including locations that were previously considered impossible due to shape, accessibility or safety issues. Even fuel tanks and other sensitive component surfaces can be measured without endangering personnel or risking the loss of the component, as microphone mounting requires no drilling. For curved surfaces like a leading edge, engineers insert the microphone into a customised ‘glove’ that conforms to the curved shape, and then mount the ‘glove’ using an industrial adhesive. With the A380 model, at least 60 surface microphones are mounted on its exterior during acoustic fatigue tests. The ultra-flat design of the microphone and aerodynamic mounting minimises the influence on airflow and thus the measurement.
Cables are held in place with metallic tape and connected to a data recorder or other data acquisition device, The plane is then flown, at times to its maximum altitude (40 000 ft.) where air temperatures can be down to –55˚C. During a flight, noise level measurements are taken based on the sound pressure on the structure’s surface. When relevant, reference measurements are also taken in the interior for comparison. Data is either recorded for later examination or processed in real-time using telemetry. The typical noise frequency is around 6 kHz.
If measurements are required within the aircraft, for example, within the cockpit, test configurations can easily be altered in-flight and new measurements made without landing, thus saving time – for some tests, up to several weeks’ work. A team outside of the test lab handles the actual data analysis, investigating, for the most part, peaks in the measurement.
Accuracy and Quality
To ensure the accuracy of measurements, all surface microphones are calibrated for sensitivity and frequency response in the lab prior to mounting, and then checked with a pistonphone once mounted. After flight-testing, the microphones are returned to the lab for an additional calibration check. This routine provides the test engineers with a verification of the measurements’ accuracy and minimises the cost of errors due to faulty or inaccurate measurements.
From the start, Airbus’ decisions in design, testing and sound and vibration solutions are always taken in consideration of customer satisfaction, as well as market and company expectations.
A380 - ndege kubwa zaidi ya kibiashara inayopatikana leo na viti vya abiria 525 - itaanza kutumika miaka 30 baadaye. Ni ushahidi mwingine wa Airbus'kujitolea kwa uvumbuzi na kubuni akili. Kwa hiyo, Airbus alikuja kwa Brüel & Kjaer kwa ajili ya maendeleo ya transducer wao inaweza daima kutumia kupima sauti shinikizo katika nafasi ndogo wakati wa ndege ya majaribio na ambapo flush upandaji wa kawaida kipaza sauti na preamplifier mchanganyiko itakuwa haiwezekani au kusababisha madhara yasiyotakiwa. Baada ya prototypes nyingi, ambayo yote walikuwa rigorously majaribio na Airbus, Surface Microphone Type 4948 alizaliwa - gorofa, ndogo, imara, sahihi na imara kipaza sauti iliyoundwa hasa kwa ajili ya maombi ya anga na inaweza kutumika hadi 165 dB. Majaribio ya uthibitisho yalionyesha kwamba kipaza sauti inaweza kuvumilia mahitaji yote ya transducers imewekwa nje ya ndege wakati wa ndege, ikiwa ni pamoja na lakini si mdogo kwa de-icing detergent, turbulence, mvua, mvua, g ngazi ya juu, joto mbalimbali kutoka <50 ° C hadi 100 ° C, cruising urefu wa 30 000 futi, na Mach 0.8. Kwa kweli kwa ahadi yao, Airbus inaendelea kutumia kipaza sauti uso katika mpango wao wa majaribio ya ndege <unk> miaka baada ya maendeleo yake. Ndege ya Design Flight-mtihani hufanyika katika Airbus <unk> Toulouse majaribio ya tovuti. Ni hapa kampuni ya utafiti mbalimbali na maabara ya kubuni kuwasilisha prototypes kuthibitisha ndege kubuni na utendaji sifa. Timu za ubunifu za mtu binafsi huamua vigezo vya mtihani, ikiwa ni pamoja na mahali pa kuweka sensorer za mtihani. "Mafunzo ya ""Testa"" ya Toulouse ni pamoja na vifaa vya kupima, vipimo, na vipimo vya sauti, na vifaa vya kupima sauti, na vifaa vya kupima sauti, na vifaa vya kupima sauti, na vifaa vya kupima sauti, na vifaa vya kupima sauti, na vifaa vya kupima sauti, na vifaa vya kupima sauti." Transducers yao ya sauti hutumiwa kwa matumizi mbalimbali, ikiwa ni pamoja na kelele ya ndani na kelele ya nje. Kwa karibu 200 mic ya uso, nguvu yao, wigo wa nguvu na kubadilika kwa kuunganisha hufanya iwe sahihi sana kwa uchambuzi wa uchovu wa sauti. Acoustic uchovu uchambuzi inachunguza sehemu ya mali ya nyenzo kwa udhaifu chini ya mkazo acoustic. Matokeo husaidia wabunifu kuchagua vifaa vinavyofaa na kusaidia kuamua mzunguko wa maisha ya sehemu za mtu binafsi ili kuhakikisha usalama wa ndege. Kuna daima mfano mmoja kwa kila familia ya ndege katika tovuti Toulouse kufanya vipimo vya kawaida ya uchovu wa sauti. Kwa ajili ya majaribio ya uchovu wa sauti, maikrofoni ya uso huwekwa kwenye uso wa muundo, ikiwa ni pamoja na maeneo ambayo hapo awali yalionwa kuwa haiwezekani kwa sababu ya muundo, upatikanaji au masuala ya usalama. Hata tanki za mafuta na sehemu nyingine nyeti inaweza kupimwa bila kuhatarisha wafanyakazi au hatari ya kupoteza sehemu, kama microphone kufunga inahitaji hakuna drilling. Kwa nyuso curved kama makali ya mbele, wahandisi kuingiza kipaza sauti katika customized <unk> glove <unk> kwamba inalingana na umbo curved, na kisha kufunga <unk> glove <unk> kutumia adhesive viwanda. A380 ina vifaa vya sauti zaidi ya 60 na ina mikrofoni ya juu ya nje ya ndege wakati wa majaribio ya uchovu wa sauti. ultra-flat kubuni ya kipaza sauti na aerodynamic kufunga hupunguza ushawishi juu ya mtiririko wa hewa na hivyo kipimo. Kabli hizo huunganishwa na mkanda wa chuma na kuunganishwa na rekodi ya data au kifaa kingine cha kupata data, kisha ndege hiyo hupaa, wakati mwingine hadi urefu wake wa juu zaidi (mita 40,000) ambapo joto la hewa linaweza kushuka hadi <55 ° C. Wakati wa ndege, vipimo vya kiwango cha kelele huchukuliwa kulingana na shinikizo la sauti kwenye uso wa muundo. Wakati muhimu, vipimo vya kumbukumbu pia huchukuliwa ndani kwa ajili ya kulinganisha. Takwimu ama ni kumbukumbu kwa ajili ya uchunguzi baadaye au kusindika katika muda halisi kwa kutumia telemetry. Kwa kawaida, mzunguko wa kelele ni karibu 6 kHz. Kama vipimo zinahitajika ndani ya ndege, kwa mfano, ndani ya cockpit, vipimo vya mtihani inaweza kwa urahisi kubadilishwa katika ndege na vipimo vipya kufanywa bila kutua, hivyo kuokoa muda - kwa baadhi ya vipimo, hadi wiki kadhaa - kazi. Timu nje ya maabara ya majaribio hushughulikia uchambuzi halisi wa data, ikichunguza, kwa sehemu kubwa, kilele katika kipimo. Ili kuhakikisha usahihi wa vipimo, mikrofoni zote za uso zinapimwa kwa unyeti na majibu ya mzunguko katika maabara kabla ya kuunganishwa, na kisha kukaguliwa na pistonphone mara moja imewekwa. Baada ya majaribio ya ndege, maikrofoni hurudishwa kwenye maabara kwa ajili ya ukaguzi wa ziada wa ukadiriaji. Hii kawaida hutoa wahandisi mtihani na uthibitisho wa vipimo <unk> usahihi na hupunguza gharama ya makosa kutokana na vipimo makosa au usahihi. Tangu mwanzo, maamuzi ya Airbus katika kubuni, kupima na sauti na vibrasia ufumbuzi ni daima kuchukuliwa katika kuzingatia kuridhika kwa wateja, kama vile soko na matarajio ya kampuni.