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La flotta di Raptor è stata messa a terra per problemi all'impianto d'ossigeno del pilota.

 

http://defensetech.org/2011/05/06/f-22-fleet-grounded-indefinitely/

 

Il provvedimento è in atto da ieri a tempo indefinito.

 

Secondo me,quell'incidente avvenuto in Alaska rientra in questo tipo di guasto.

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Ecco la notizia in italiano

 

165 aerei F-22 Raptor Usaf messi a terra

 

Anchorage, Alaska - Per sospetto malfunzionamento del sistema generatore di ossigeno

 

 

(WAPA) - Secondo quanto riferito negli scorsi giorni da ufficiali dell'Usaf, Us Air Force, l'intera flotta degli aerei Lockheed Martin-Boeing F-22 Raptor delle forze aeree statunitensi, pari a 165 esemplari, è stata messa a terra a tempo indeterminato.

 

La disposizione è stata stabilita dall'Air Combat Command, Acc, a causa di un sospetto malfunzionamento al sistema generatore di ossigeno che potrebbe aver provocato l'incidente, occorso a novembre dello scorso anno, ad un aereo di questo tipo nel corso di una esercitazione notturna, proprio fuori dalla Joint Base Elmendorf-Richardson, Alaska, in cui perse la vita il capitano Jeffrey Haney.

 

Da quel momento e fino alla messa a terra della flotta, stabilita il 3 maggio, il sistema Obogs, On Board Oxygen Generating System, di cui gli F-22 sono equipaggiati, fu messo sotto inchiesta ed è stato disposto che le operazioni degli F-22 non superassero il limite di 25.000 piedi, un'altitudine dalla quale il pilota può facilmente scendere fino a quota 18.000 piedi, in cui l'atmosfera continene ossigeno sufficiente da consentire una sopravvivenza prolungata in casi di emergenza.

 

L'Acc ha comunque tenuto a specificare che non si tratta tecnicamente di una messa a terra, di cui si parla solo a seguito di eventi catastrofici, ma più propriamente di un "Ritiro", eseguito volontariamente e in via precauzionale. (Avionews)

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Sono a terra ..... ma in caso di necessità ....

 

DATE: 05/05/11

SOURCE: Flight International

 

Oxygen system concerns prompt F-22 stand-down

 

By Stephen Trimble

 

The US Air Force has stopped flying all Lockheed Martin F-22s for an indefinite period over concerns about a possible glitch in the onboard oxygen generation system.

 

The stand-down order issued on 3 May by Air Combat Command (ACC) chief Gen Will Fraser comes about six weeks after the F-22s were restricted to flying below 25,000ft due to the same problem.

 

The order is in effect until "further notice", the ACC says.

 

"The standown is a prudent measure following recent reports of oxygen system malfunction," Fraser said in a statement.

 

While the F-22s remain parked, investigation teams will continue to determine the cause of the malfunction, the statement added.

 

The ACC emphasized that the stand-down order is technically not considered a "grounding", which occurs only in response to a catastrophic technical issue. A stand-down is voluntary and precautionary.

 

Despite keeping the F-22s on the ground, ACC believes the stand-down order will not change the air force's ability to perform missions such as air superiority alert. The F-22 is still available for "national security directed missions", the ACC said. One-time flights can also be approve by the heads of major commands, including repositioning flights.

 

The air force has been flying the F-22s operationally for more than five years, with more than 150 already in service. All 186 F-22s on order are expected to be delivered by early next year.

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Ci sono piccole rivelazioni sull'evento che ha causato l'atterramento della flotta.

 

An Air Force Association report said ACC officials are attempting to determine the cause of pilot “physiological-hypoxia-like events reported through Air Force safety channels.” The report added that a second incident occurred in Alaska before the stand down when a pilot scraped an F-22 underside on trees while landing “but could not recall what happened.”

Read more: The Warner Robins Patriot - Some additional information available on F 22 stand down

 

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Ogni volta che una flotta viene messa a terra il motivo è davvero grave... Non ci può essere dell'altro?

 

Si, che tutti i dispositivi su tutti gli aerei americani potrebbero essere soggetti allo stesso tipo di malfunzionamento, sebbene sia quello del Raptor, che attraverso alcune modifiche alla ricerca di leggerezza e compattezza, che lo ha manifestato con picchi preoccupanti.

 

http://www.airforcetimes.com/news/2011/05/air-force-oxygen-generator-inquiry-all-fighter-jets-051611w/

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  • 3 weeks later...

Ancora non si sa nulla purtroppo... comunque è un mezzo che per gli alti costi di gestione sta subendo una politica di "cancellazione" e riduzione come è capitato anche per il B2

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Sono ancora a terra ....

 

Fonte: Aviation Week and Space Technology

 

F-22s Grounded Pending Oxygen System Probe

 

By Bill Sweetman

Washington (July 18, 2011)

 

The U.S. Air Forces F-22 fighter remains subject to the longest full-force grounding of any combat aircraft in recent history, with no cause firmly identified. Meanwhile, documents show that the focus of the investigationthe onboard oxygen-generation system (Obogs)has been a flight safety issue for many years on the F/A-18C/D Hornet, increasing the number of cases where aircrew were affected by hypoxia, or lack of oxygen, in flight.

 

An Obogs problem is considered the most likely cause for the Nov. 16, 2010, crash of a 525th Fighter Sqdn. F-22 operating from Joint Base Elmendorf-Richardson in Alaska. The aircraft crashed about 100 mi. north of Anchorage. The pilot did not eject and was killed, and the aircraft left a deep crater suggestive of a steep-angle, high-speed impact.

 

As the investigation continued, the F-22 fleet was restricted in January 2011 from flight above 25,000 ft., following reports of multiple incidents that pointed to occurrences of hypoxia. On May 3, a full safety stand-down order was issued. The only exceptions were a limited series of test flights, conducted with real-time monitoring, to verify software fixes.

 

The USAF is being tight-lipped about the investigation. The response to the question, Has a cause been positively identified? is, The investigation is still ongoing.

 

The Obogs on the F-22 is made by Honeywell in the U.K., and systems fitted to the F/A-18 are produced in the U.S. by Cobham. (Cobham acquired the unit in 2003 that was previously Bendix, then Litton and subsequently Northrop Grumman.) However, they work on the same principle, passing engine bleed air through a molecular-sieve oxygen generator that absorbs nitrogen and other gases and delivers near-pure oxygen to the pilot.

 

According to a source familiar with some aspects of the investigation, Honeywell participants in the investigation believe the problem does not lie with the Obogs alone. An alternative hypothesis points to a problem with the sealing of the oxygen mask or with the counter-pressure garment worn by the pilot. The latter allows for positive-pressure breathing under high g-loading or in the event of loss of cockpit pressure. To stop the pilots chest from expanding under pressure and impeding blood circulation, the garment is inflated by the oxygen system and compresses the pilots upper body.

 

A complicating factor, one observer suggests, could be the fact that the F-22 (and F-35) Obogs are relatively simple systems with two flow rates, with high-flow triggered by specific events such as high g-loadings. A problem such as a mask leak or a faulty valve in the counter-pressure garment could be slower to trigger a rate increase, a potential problem in critical situations such as maneuvering at high altitude, with low ambient pressure in the cockpit.

 

The U.S. Navy, meanwhile, has been dealing with a post-2000 spike in hypoxia-related Class A mishaps (causing the loss of the aircraft or pilot or more than $1 million in damage) in the Hornet fleet. A 2005 article in the Navy aviation-safety publication Approach noted that the rate of such incidents in 2001-04 was almost 10 times that in 1980-2000, and that Obogs-equipped aircraft were suffering from hypoxia events at four times the rate of liquid-oxygen-equipped types.

 

A further analysis of 2002-09 data showed 64 hypoxia events in F/A-18s, with Obogs failure being the largest single cause (29%). Two events resulted in fatal accidents.

 

One factor appears to be that Obogs can result in mask-on hypoxia due to contaminants or other partial Obogs failures. In August 2005, the Naval Safety Center released a message that warned of a remote possibility of contamination by gases such as acetylene, carbon monoxide and carbon dioxide.

 

All Obogs include an oxygen-monitoring system to warn the user if the system is not delivering the required concentration of oxygen. According to a patent filed in 1990 on behalf of Normalair-Garrett (now Honeywell), early monitoring systems were based on electro-chemical technology used in medical laboratories and suffered from drift over time and limited life. Alternative systems added complexity because they required a second reference source of air bled from the engine. (The F-22 has a solid-state controller.)

 

Improved systems have been developed since. The original GGU-12 oxygen concentrator used on the F/A-18 family is being upgraded with the addition of a catalyst that converts carbon monoxide to benign carbon dioxide, and the Navy has been working to install an updated solid-state oxygen-monitoring system on all in-service F/A-18s that tracks oxygen pressure and concentration. A cockpit pressure warning system has also been introduced.

 

A fiscal 2009 Small Business Innovation Research solicitation, meanwhile, called for ideas for a miniaturized, non-invasive sensor that would monitor the pilot for signs of hypoxia.

 

 

Al tempo stesso, Sweetman ha aperto, sul blog "Ares", una discussione che, a quanto sembra, è molto seguita ....

 

http://goo.gl/NSVcy

Edited by TT-1 Pinto
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Sembra che gli investigatori USAF abbiano individuato il problema che ha messo a terra i Raptor: l'Ipossia riscontrata sui piloti sarebbe causata dal monossido di carbonio generato dal motore che viene risucchiato dall'aereo dentro il cockpit.

 

Parte del problema possono essere le procedure utilizzate alla Elmendorf Air Force Base, in Alaska, dove la maggior parte degli incidenti si sono verificati. A causa del clima rigido, i piloti spesso avviano i loro motori all'interno di un capannone prima del decollo. Gli investigatori sospettano che i gas di scarico saturino l'edificio e, successivamente, vengano risucchiati nei motori e successivamente penetrino nel cockpit.

 

 

Notizia completa:

 

Mio Link

Edited by VittorioVeneto
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La ripresa delle operazioni di volo potrebbe essere imminente ....

 

http://www.dodbuzz.com/2011/08/31/af-raptors-could-resume-flying-soon/

 

 

Dal sito dell'Air Force Association ....

 

Daily Report

Wednesday August 31, 2011

Return of the Raptor: The F-22 fleet will probably be up and running again "soon," said Chief of Staff Gen. Norton Schwartz. In an interview Tuesday, Schwartz said he expects a report next week from the Air Force Scientific Advisory Board task force headed by retired Gen. Gregory Martin, which will offer a way forward regarding questions about the F-22's onboard oxygen generation system. Schwartz said last week's evacuation of F-22s from JB Langley-Eustis, Va., in anticipation of Hurricane Irene was a simple early implementation of the "return-to-flight" plan developed for when the F-22 grounding is lifted. Schwartz also said the OBOGS has been ruled out as a factor in last November's crash of an F-22 in Alaska, which took the life of the pilot. A more thorough investigation of the crash site was possible during the recent summer months and yielded recovered hardware and computer memory that made a more comprehensive analysis possible. Completion of an accident investigation board report, long delayed due to difficulties in assessing the wreckage, is expected soon, Schwartz said.

John A. Tirpak

 

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Verso la consegna dell'ultimo esemplare ....

.... e aggiornamenti circa la messa a terra ....

 

Lockheed halted deliveries to the USAF while the F-22 was ordered grounded by the Air Combat Command after 3 May.

 

That order continued to be in effect after this article went to press, although the fleet's status could change quickly.

 

Although the fleet is technically grounded, some F-22As have been allowed to fly for specific reasons. As Hurricane Irene approached the US east coast in late August, the USAF scrambled F-22As and other fighters away from Langley AFB, Virginia.

 

USAF officials have confirmed that hypoxia was ruled out as a potential cause of the fatal F-22 crash at Joint Base Elmendorf-Richardson, Alaska, last November. The actual cause of the incident has not been released.

 

That unexplained crash and a string of reports of hypoxia illness prompted the USAF to voluntarily stand down the F-22A fleet. The service is continuing to study aircraft onboard oxygen generating systems (OBOGS) for the F-22A and several other aircraft, including the Lockheed F-35A.

 

The OBOGS investigation is led by a scientific advisory committee chaired by Gregory Martin, a retired USAF general and fighter pilot.

 

Fonte .... http://www.flightglobal.com/articles/2011/09/07/361709/lockheed-starts-final-assembly-on-last-f-22a.html

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Ma come mai il problema si è riscontrato solo nell'f22a ?? avevo letto qualcosa al riguardo che diceva che anche aerei come f18, 15 , 35 , a-10 possiedono lo stesso tipo di impianto ma non sono stati riscontrati problemi..comunque è impressionante per un po anche i b-2 sono stati fermi a terra perchè anno avuto problemi alle vernici stealth.. il b-2 capisco ma e veramente strano che non possano essersi accordi di eventuali problemi di malfunzionamento dell'impianto oltre una certa quota.. l'f-22 e un caccia che definirlo avanzato è poco.. è strano che durante la progettazione e la fase di collaudo non si siano accorti del problema dato che le prime consegne sono avvenute nel 2005 (se non sbaglio)..

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A dire il vero possono esserci mille motivi per cui un errore di progettazione possa essere venuto fuori solo a operatività iniziata. Potrebbe darsi che sia un danno o un malfunzionamento dovuto a particolarissime condizioni mai previste, o magari errori costruttivi. Chi lo sa... Aspetteremo la fine delle indagini!

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  • 2 weeks later...

Ritorno imminente?

 

.... Dal sito dell'AFA (U.S. Air Force Association) ....

 

F-22 Coming Back

 

The F-22’s oxygen-generating problems continue to defy a massive scientific assault, but the Scientific Advisory Board, which is exploring the issue, is proposing a return-to-flight plan likely to be implemented in the coming week or two, sources told the Daily Report Monday at AFA's Air & Space Conference.

Flight restrictions will likely apply to training aircraft, and a series of rules are being developed for operational types.

The SAB has applied tremendous resources to investigating the issue, to include 16 flights with a heavily instrumented F-22.

The problem—contamination and reduced output of the onboard oxygen generating system—is not easy to reproduce.

Outgassing of vent materials and conditioning of the ram air itself seem not to be the culprits, although intake of air in confined spaces with the engines running may play a role.

There are also indications that heavy G-loading of the F-22 may hamper the OBOGS, but a root cause for all incidents remains elusive.

The SAB will continue to work and plans a report in October; a publicly releasable version will also be made available.

 

(John A. Tirpak)

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Sembra che gli F22 siano stati autorizzati a ritornare in volo :D

 

Fonte http://fromtheskies.wordpress.com/2011/09/20/gli-f-22-tornano-a-volare/ nell'attesa di trovare una fonte più attendibile...

Le fonti "più attendibili" confermano ....

 

Flightglobal.com .... http://www.flightglobal.com/articles/2011/09/20/362304/usaf-clears-f-22s-for-flight-after-inspections.html

 

Aviationweek.com .... http://goo.gl/dG0pk

 

 

@ eugy78

 

una cosa NON so... l'F-22 ha un sistema autonomo di produzione dell'ossigeno..come i nostri EFA??

La risposta la trovi nei links ....

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Sembra che gli F22 siano stati autorizzati a ritornare in volo :D

 

Fonte http://fromtheskies.wordpress.com/2011/09/20/gli-f-22-tornano-a-volare/ nell'attesa di trovare una fonte più attendibile...

 

la fonte dell'articolo pubblicato su http://fromtheskies.wordpress.com/2011/09/20/gli-f-22-tornano-a-volare/ è il sito ufficiale USAF: http://www.af.mil/news/story.asp?id=123272608

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