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F-35為調(diào)試初始作戰(zhàn)能力進(jìn)行冷處理

位于弗洛里達(dá)州埃格林空軍基地的第96試驗(yàn)飛行中隊(duì)的麥金利氣候?qū)嶒?yàn)室，從1947年開(kāi)始成為一個(gè)重要的低溫天氣測(cè)試機(jī)構(gòu)，至今已為各種飛機(jī)進(jìn)行過(guò)相關(guān)測(cè)試。從B-29超級(jí)空中堡壘與P-51野馬到洛克希德F-117、波音787以及空中客車A350 XWB，參與過(guò)測(cè)試的機(jī)型不勝枚舉。

最近，來(lái)自馬里蘭州巴塔神河綜合測(cè)試連隊(duì)的一架洛克希德馬丁F-35B在該實(shí)驗(yàn)室接受了嚴(yán)格的天氣測(cè)試，以在其進(jìn)行初始作戰(zhàn)能力調(diào)試（IOC）的過(guò)程中，確保在各種氣候條件下，性能水平得到萬(wàn)無(wú)一失的發(fā)揮。F-35B于2014年9月到達(dá)麥金利實(shí)驗(yàn)室，在接下來(lái)的6個(gè)月中，它將接受風(fēng)、太陽(yáng)輻射、霧、濕氣、雨水浸入/倒灌、雨夾冰、冰凍云、結(jié)冰、渦流結(jié)冰與降雪等多種天氣條件下的性能測(cè)試。

由于目前F-35項(xiàng)目涉及到13個(gè)國(guó)家，因此其將要飛行的所有國(guó)家的代表性天氣都必須經(jīng)過(guò)測(cè)試，其中包括澳大利亞南部的炎炎烈日，以及加拿大與挪威上空北極圈的刺骨嚴(yán)寒。

F-35將承受-40°到+120°F的測(cè)試溫度范圍，“以及該溫度中的任何可能出現(xiàn)的天氣情況，”在F-35上進(jìn)行極冷測(cè)試操作的測(cè)試飛行員Billie Flynn表示。“它已經(jīng)在100°F以上的高溫和零下低溫中飛行過(guò)了。在測(cè)試的最初幾天，它將飛越冰凍天氣和包括傾盆大雨和颶風(fēng)在內(nèi)的其他惡劣天氣。我們每天都會(huì)多了解一些飛機(jī)的情況。”（點(diǎn)擊此處觀看Flynn談?wù)揊-35天氣測(cè)試項(xiàng)目的完整視頻）

而實(shí)驗(yàn)艙可以進(jìn)行“幾乎所有天氣條件的模擬，無(wú)論在普通還是垂直起飛模式下，飛機(jī)馬力全開(kāi)時(shí)可能遇到的所有天氣條件，”麥金利天氣實(shí)驗(yàn)室的技術(shù)人員Dwayne Bell表示。

由于F-35今年就要在美國(guó)海軍陸戰(zhàn)隊(duì)開(kāi)始IOC服役了，因此STOVL（短距起飛/垂直降落）測(cè)試將比之前的飛機(jī)在程序上多一些變化。埃格林空軍基地報(bào)告稱，F(xiàn)-35B的升力風(fēng)扇系統(tǒng)需要設(shè)計(jì)一個(gè)用于“限制與支持”的結(jié)構(gòu)，高度為12英尺，并與通風(fēng)管系統(tǒng)結(jié)合在一起。這一裝置使飛機(jī)實(shí)驗(yàn)室建筑內(nèi)部也能用大馬力運(yùn)行，不論是使用普通模式還是STOVL模式。

為了給噴氣口通風(fēng)，以使艙內(nèi)溫度保持穩(wěn)定，必須不斷地泵送調(diào)節(jié)過(guò)的空氣，以確保飛機(jī)內(nèi)的壓力永遠(yuǎn)高于發(fā)動(dòng)機(jī)周圍管道內(nèi)的壓力，并高于飛機(jī)其他開(kāi)口處的壓力。這一壓差可確保噴射排氣會(huì)通過(guò)管道流出艙外，從而使整個(gè)飛機(jī)維持在恒定的溫度水平。

在數(shù)日的高溫天氣測(cè)試后，發(fā)動(dòng)機(jī)的測(cè)試溫度穩(wěn)步上升至最高測(cè)試溫度——120°F。實(shí)驗(yàn)艙內(nèi)溫度維持在預(yù)設(shè)溫度上，同時(shí)飛機(jī)上方的太陽(yáng)燈為飛機(jī)表面照上了強(qiáng)烈的日光。之所以這么做，是因?yàn)榭諝鉁囟仁遣粫?huì)在一天內(nèi)保持不動(dòng)的，它會(huì)隨著太陽(yáng)的升起溫度升高，并在下午晚些時(shí)候達(dá)到最高點(diǎn)。而在實(shí)驗(yàn)艙內(nèi)，工程師們創(chuàng)造了一天24小時(shí)的溫度波動(dòng)模擬條件。

在短短數(shù)日內(nèi)，實(shí)驗(yàn)艙的環(huán)境就從亞利桑那州的酷暑轉(zhuǎn)成了北極圈的嚴(yán)寒。麥金利實(shí)驗(yàn)室的制冷系統(tǒng)將室外空氣冷卻至極低溫度，并將其推入艙內(nèi)。當(dāng)飛機(jī)結(jié)束測(cè)試時(shí)艙內(nèi)溫度已累積降至-40°F。在如此低的溫度下，飛機(jī)系統(tǒng)中的液體開(kāi)始變稠，各種機(jī)械的運(yùn)行也開(kāi)始變緩，這些都是測(cè)試工程師密切監(jiān)控的重點(diǎn)。

在此之后，F(xiàn)-35需要迎戰(zhàn)冰雪的猛烈攻擊。在冰凍天氣中，當(dāng)一架飛機(jī)以高速穿越云層時(shí)，飛機(jī)外側(cè)將迅速聚集起大型冰塊。厚重冰塊可能發(fā)生斷裂并傷害飛機(jī)，進(jìn)入發(fā)動(dòng)機(jī)，或造成外物侵入的損害。因此，結(jié)冰是天氣測(cè)試中最危險(xiǎn)的元素之一。

一個(gè)由三個(gè)巨型圓柱體組成的大型裝置以金字塔形堆疊起來(lái)，并與地面呈平行放置于F-35測(cè)試機(jī)體的前方。圓柱體內(nèi)部安裝了9個(gè)導(dǎo)管風(fēng)扇，它們將一股巨大氣流，吹入前方的一個(gè)漏斗內(nèi)。漏斗前端安裝的一個(gè)噴桿，能夠產(chǎn)生由各種直徑的小水滴組成的“云”。

這些小水滴朝著飛機(jī)的方向噴去，并在接觸的同時(shí)凍結(jié)起來(lái)。盡管實(shí)驗(yàn)室不能產(chǎn)生飛機(jī)實(shí)際經(jīng)歷的精確風(fēng)速，但實(shí)驗(yàn)艙內(nèi)的這一獨(dú)特裝置卻能夠產(chǎn)生高達(dá)120 mph的恒定風(fēng)速，這是F-35墜落時(shí)承受的速度。

冰雪測(cè)試可衡量飛機(jī)冰凌防護(hù)系統(tǒng)的有效性，以及飛機(jī)在冬季天氣中的運(yùn)行能力。

F-35 gets cold treatment in step toward IOC remedy

Since it first became an active cold-weather testing facility in 1947, the 96th Test Wing's McKinley Climatic Laboratory at Eglin Air Force Base, FL, there have been a wide variety of aircraft to undergo testing at the facility, ranging from the B-29 Superfortress and P-51 Mustang through to the Lockheed F-117, Boeing 787, andAirbus A350 XWB.

Most recently, one of Lockheed Martin’s F-35Bs from the F-35 Patuxent River Integrated Test Force in Maryland underwent rigorous climatic testing at the laboratory to verify its all-weather capabilities on its way toward Initial Operating Capability (IOC). The F-35B arrived at McKinley in September 2014, to begin a six-month assessment of the aircraft's performance in wind, solar radiation, fog, humidity, rain intrusion/ingestion, freezing rain, icing cloud, icing build-up, vortex icing, and snow.

With 13 countries currently involved with the program, the F-35 must be tested in all the meteorological conditions representative of those locations from which it will operate, ranging from the heat of northern Australia to the bitter cold of the Arctic Circle above Canada and Norway.

Testing for the F-35 can be done from -40° to +120°F “and every possible weather condition in between," said Billie Flynn, an F-35 test pilot who performed extreme cold testing on the aircraft. "It has flown in more than 100°F heat while also flying in bitter subzero temperatures. In its final days of testing, it will fly through ice and other conditions such as driving rain with hurricane force winds. We are learning more and more about the aircraft every day.” (Click here to view Flynn discussing the F-35 climatic test program.)

The chamber allows for the simulation of “virtually any weather condition—all while flying the jet at full power in either conventional or vertical takeoff mode," said Dwayne Bell, the McKinley Climatic Laboratory technical chief.

As the F-35 approaches its IOC debut for the U.S. Marine Corps this year, testing for the STOVL (short takeoff/vertical landing) variant required a few more adaptations to procedures than aircraft before it. Eglin AFB reports that the lift-fan system of the F-35B required the design of a 12-ft high “restraint and support” structure interwoven with a system of ventilation ducts. This apparatus secures the aircraft and allows it to operate at high power in both conventional and STOVL mode while inside the building.

To ventilate the exhaust and thus maintain a stable temperature inside the chamber, conditioned air is constantly pumped in to ensure the pressure in the building is always higher than the pressure inside the ducts surrounding the engine and other openings on the aircraft. This difference in pressure is a safeguard that maintains the jet exhaust is flowing out of the chamber through the ducts, allowing the facility to sustain a constant temperature.

Over days of high-temperature climatic testing, the temperatures of the engine runs were steadily and incrementally increased until it reached the test maximum of 120°F. While the chamber itself was set to a pre-determined temperature, additional solar lamps above the aircraft recreated the intense heat of the sun on the surface of the jet. This is done for the obvious reason that air temperature does not remain constant throughout the day—it increases each hour the sun is up, reaching its apex in the late afternoon. In the chamber, engineers recreated the temperature fluctuation of a 24-h day.

In a matter of days, the chamber transitioned from a seemingly Arizona sauna to the Arctic Circle. Outside air was super-cooled using McKinley Lab’s refrigeration system and pushed into the chamber. In increments, the chamber temperature fell to -40°F while the jet completed test runs along the way. At such frigid temperatures, aircraft fluids start to thicken and mechanisms operate slower—all points upon which test engineers monitor closely.

The F-35 then faced a harsh barrage of snow and ice. When an aircraft flies through clouds at high speeds in freezing climates, large pieces of ice can form quickly on the exterior. Heavy chunks of ice could potentially break off and damage the aircraft, errantly fly into the engine or create a foreign-object-damage concern. For this reason, icing is one of the most dangerous elements in climatic testing.

A large apparatus composed of three massive cylinders stacked in a pyramid, parallel to the ground, was placed in front of the F-35 test aircraft. Inside the cylinders were nine ducted fans that blew a large amount of air through a single funnel in the front. Attached to the front of this funnel was a spray bar capable of producing “clouds” of various water droplet sizes.

Those droplets were blown toward the plane and froze upon contact. While the lab cannot generate the precise wind speeds experienced by airborne aircraft, the unique setup inside the chamber is capable of producing sustained wind speeds up to 120 mph—all while subjecting the F-35 to precipitation.

Snow and ice testing gauges the effectiveness of the aircraft’s Ice Protection System and the ability of the jet to perform in winter weather.