Jun 052019

“An Airbus A321 carrying Russian tourists back from Egypt in 2015 suddenly disappears from radar minutes after takeoff. Air Force jets locate the charred wreckage in the Sinai Desert. There are no survivors. How did this modern airplane just fall from the sky? Follow Egyptian investigators and their Russian counterparts as they work through political tensions and wild rumors to discover the truth behind the crash of Metrojet Flight 9268. With 224 passengers and crew on board killed, the Russian Metrojet crash is the worst air accident in the history of Russian aviation.”

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“Did an old accident cause the October 31, 2015 crash of Russian Metrojet Flight 9268 Airbus A321, or were more nefarious forces to blame for killing 224 passengers and crew on board? 

Watch below “Terror Over Egypt,” the Season Premier of  Smithsonian Channel.” 

“On October 31, 2015, Metrojet Flight 9268 disintegrates in mid-air and crashes into the Sinai Peninsula during a routine chartered flight from Sharm El Sheikh International Airport to Pulkovo Airport, killing all 224 people on board.”

“Did a serious 2001 accident to Metrojet 9268 cause it to fatally crash on October 31, 2015? Investigators look closely at the affected part of the plane – the rear fuselage – hoping for a breakthrough.”

From the Series: Air Disasters: Terror Over Egypt http://bit.ly/2rItW85 

FBI agents in the United States have agreed to help with forensic analysis after last week’s crash of a Russian airliner in Egypt.
The British government suspects a bomb exploded on board, plunging all 224 passengers and crew to their deaths. Egyptian crash investigators are complaining about the lack of intelligence sharing – and insist it’s too early to say what caused the disaster.
Amid the confusion and uncertainty, thousands of tourists are still stranded in Sharm El Sheikh trying to fly home. So, who can we trust to tell the truth? And how much politics is involved?
Jane Dutton
Martin Reardon, Senior Vice President of the Soufan Group.
Igor Sutyagin, Senior Research Fellow at the Royal United Services Institute.
Oliver McGee, Former U.S. Deputy Assistant Secretary for Transportation and aviation specialist.
Published on Nov 8, 2015SUBSCRIBED 2.8M

Metrojet Airbus A321 Reg #EI-ETJ -- 7

Russian Metrojet Airbus A321-231 crashed minutes after takeoff, fatally resulting in the death of 224 people, in mountainous Sinai Peninsula (Egypt) on Saturday, October 31, 2015 at 04:12 Zulu (Greenwich Mean Time, GMT) or 12:12 am ET.

Photo Credit: 1993 REUTERS/Kim Philipp Piskol. Metrojet’s Airbus A321-231, Registration number EI-ETJ, performing as flight 7K-9268taxis at Antalya, Turkey before the tragic crash.

Operated by Russian air carrier, formerly known as Kogalymavia, Kolavia (Moscow-Domodedovo), and branded as MetroJet, according to the Egyptian aviation ministry, Metrojet’s Airbus A321-231, Registration number EI-ETJ, was performing flight 7K-9268 en route from Sharm el Sheikh (Egypt) to St. Petersburg (Russia) with 217 passengers and 7 Metrojet crew on board, Russia’s Rosaviatsia (Civil Aviation Authority) confirms.

Speculatively and preliminarily speaking, ahead of detailed analysis of the flight deck recorders or “black-boxes” recovered today from the extensive crash site wreckage at Al Arish (Sinai, Egypt) on the coast of the Mediterranean Sea, a technical malfunction in the airliner’s International Aero Engines AG V2533-A5 turbofan engines is only at first-glance attributed to the aerodynamic stalling of the Airbus A321-231 (losing altitude from 31,000 feet at nearly 6,000 feet per minute) about 23 minutes after takeoff from a Red Sea resort popular with Russian tourists, Egypt’s Ministry of Civil Aviation has said.

IAE International Aero Engines AG “manages engineering, sales, production, customer support and aftermarket services for the V2500® series engine – one of the most successful commercial jet-engine programs in production today.”

“Approximately 190 airlines and lessors from about 70 countries operate the V2500 series engine. To date, the V2500 series engine has accumulated over 125 million flight hours,” according to the IAE website.

Meanwhile, Foreign Secretary Philip Hammond on Wednesday, November 4 spoke of a “significant possibility” that Metrojet flight 7K-9268 was “caused by a bomb and Britain immediately suspended all flights to and from Sharm el-Sheikh, the Red Sea resort where the flight originated,” Daily Mirror (U.K.) reports in an extensive rolling timeline of developments in this ongoing crash investigation by the French BEA, Egyptian government officials, Russian Metrojet airline officials, and British and U.S. intelligence.

“Egyptian officials have condemned Britain’s travel ban as an overreaction. Egyptian president Abdel-Fattah al-Sisi is in London on a state visit, facing what is likely to be a tense meeting with Prime Minister David Cameron,” says the Daily Mirror (U.K.).

However, until the Airbus A321-231 cockpit voice recorders (CVRs) and the flight data recorders (FDRs), known as “the black boxes” are fully analyzed by the French BEA investigators, nobody really knows what happen during the final moments of Metrojet flight 7K-9268 on Saturday, October 31.

The Telegraph (U.K.) and French television channel France 2 is reporting on Friday, November 6 that the black boxes “distinctly show the sound of an explosion during the flight”, according to an investigator who had access to them.

They said: “the explosion would not be secondary from engine failure.”

In other words, “there is no sign of mechanical malfunction during the initial part of the flight,” France 2 reported. “Everything is fine during the first 24 minutes, then in a fraction of a second there is a blackout and no more cockpit conversation, convincing investigators there was a bomb on board,” according to France 2.

On Saturday, November 7, 2015, Egypt’s Air Accident Investigation Commission (EAAIC) in a news conference stated, according to the Aviation Herald:

  • “The wreckage is distributed over a length of more than 13 kilometers consistent with in-flight breakup with several parts of the wreckage missing.
  • Initial observation of the wreckage does not yet allow for a definitive determine of the exact cause of the in-flight break up.
  • The flight data recorder (FDR) was successfully downloaded and preliminary review of the data suggests the recording stopped 23 minutes and 14 seconds after Metrojet flight 7K-9268 Airbus A321-231 was airborne. The last FDR recorded altitude was 30,888 feet MSL, last FDR recorded airspeed was 281 knots, the autopilot 1 was engaged, the aircraft was still climbing.
  • The cockpit voice recorder (CVR) was successfully downloaded and a first listening by French BEA investigators has been completed. The CVR transcript is currently being compiled, a noise has been heard in the last second of the CVR recording. A spectral analysis (or spectrum analysis – a statistical and signal processing mathematical algorithm that estimates the strength of varying frequency components of a time-domain noise signal) – is being performed to determine the frequency nature and location of this noise (now widely reported as an alleged explosion). 
  • Parties reporting facts outside of the investigation should provide their evidence to the accident investigation commission (Editorial note: this appears to be a reference to British and US Intelligence suggesting the aircraft was brought down by a bomb).”

The head of the Egyptian technical committee investigating the crash has confirmed that the recording from the plane’s black box reveals a sound in the last second of the recording, The Telegraph (U.K.) adds and CNN confirms further.

Ayman el-Mokkadem said: “Initial observations… do not allow for identifying the origin of the in-flight break-up” of the Airbus A-321 last Saturday 23 minutes and 14 seconds after it took off from the Red Sea resort of Sharm el-Sheikh.

He said: “A noise was heard in the last second of the recording by the cockpit voice recorder” and “a spectral analysis will be done to determine the origin of this noise”.

When answering a question about what the sound represented he said: “The sound is not the only evidence – we need to have a lot of evidence to indicate that something specific happened.”

“All the scenarios are open, it could be a fatigue at the plane body, or an explosion of something…,” said Ayman el-Mokkadem. 

Current expert theories speculating about how the Airbus A321-231 airliner broke apart at 31,000 feet in clear weather cruise flying align along two fronts proposing either engine malfunction and failure or alleged bomb on-board perhaps inside the luggage compartment, originating from a significant security breach at the originating airport in Sharm el Sheikh (Egypt). 

On Thursday, November 5, it appears the U.K. Prime Minister David Kameron alongside U.S. Intelligence officials are going forward on the probable cause of the crash as a “most likely bomb on board theory,” pushing swiftly on their aviation security investigations, ahead of the aviation safety investigation, comprising the French BEA analysis of the Airbus A321-231 black boxes, which could reveal a probable cause of significant engine malfunctioning failure, The Telegraph (U.K.) reports in its extensive rolling timeline of current developments in the crash investigation by the French BEA, Egyptian government officials, Russian Metrojet airline officials, and British and U.S. intelligence.

France’s air accident investigation agency, BEA, told CNN on Friday, November 6 that “Egyptian officials will make an announcement about the crash investigation within the next 24 hours.”

An Egyptian Ministry of Foreign Affairs spokesman said on Twitter that “the Egyptian Ministry of Civil Aviation will hold a new conference at 5 p.m. local time (10 a.m. ET) Saturday.”

On Friday, November 6, “Russian President Vladimir Putin agreed to suspend Russian air traffic with Egypt until the cause of the crash can be determined,” the Kremlin said.

“Putin has accepted the recommendations of the National Anti-Terrorist Committee to suspend flights with Egypt. … The President has also instructed to provide assistance to Russian citizens to return from Egypt. In addition, the President has instructed to engage with the Egyptian side to ensure the safety of air traffic,” the Kremlin said.

A separate source, also not authorized to speak on the record, said on Thursday, November 12, that “based on the facts so far, one of the working theories is that a bomb was planted at or near the fuel line or where it attaches to the engine, with the fuel burning off the explosive. This theory would explain the apparent lack of residue immediately found,” the source says, according to Fox News.

Fox News was told both scenarios point to an “airport insider.”

Adel Mahgoub, chairman of the state company that operates Egypt’s civilian airports, said “except for three Ukrainian passengers all on board were Russian citizens.”

An Egyptian cabinet statement said the 217 passengers included 138 women, 62 men and 17 children.

Russian television showed scenes of relatives and friends gathering at St. Petersburg’s Pulkovo airport, awaiting word on the fate of their loved ones. 

Our collective thoughts, prayers, and sympathies remain with the families, friends, and loved ones of those 224 persons lost, as they try to endure in deep anguish for their terribly devastating losses, surrounding today’s Metrojet flight 7K-9268 crash.

Russian President Vladimir Putin declared November 1, 2015, a national day of mourning, according to a statement posted on the Kremlin’s website.

Relatives_of_passengers (Telegraph UK)

Photo Credit: The Telegraph (U.K.). In St. Petersburg (Russia) Pulkovo Airport, grieving relatives of victims on board learn of the fate of Metrojet’s Airbus A321-231, Registration number EI-ETJ, performing as flight 7K-9268.

Two of the passengers on the Metrojet flight, Elena Rodina and Alexqander Krotov, were newlyweds, a friend of the couple told the Associated Press at a hotel near the airport. They were both 33.

Yulia Zaitseva said Rodina “really wanted to go to Egypt, though I told her ‘why the hell do you want to go to Egypt?’”

“We were friends for 20 years,” she said. “She was a very good friend who was ready to give everything to other people. To lose such a friend is like having your hand cut off.”

She said Rodina’s parents feel “like their lives are over.”

Roughly three million Russian tourists, or nearly a third of all visitors in 2014, come to Egypt every year, mostly to Red Sea resorts in Sinai or in mainland Egypt.

“It is too premature to detect the impact this will have on tourism. We need to know what happened first,” Tourism Ministry spokeswoman Rasha Azazi told the Associated Press.

Immediate question among the flying tourists is whether it is indeed safe to fly given today’s rare aviation safety circumstances, surrounding the crash of Russian Metrojet flight 7K-9268 in Sinai (Egypt). 

The answer is yes, of course, supported by a poignant U.S. federal government statistics. 

For air and space transport (including air taxis and private flights), the National Safety Council (NSC) says the relative risks of flying are extremely favorable odds of 1 in 7,178 for a lifetime against one receiving death or injury as a result of flying in a commercial passenger airliner. These relative risks of flying are compared by the NSC to the odds of dying in a motor vehicle accident at 1 in 98 for a lifetimeUSA Today reports.

Google Map of Crash Event

The Airbus A321-231 vanished from radar as the airliner was flying to 30,700 feet out of Sharm el Sheikh over the Sinai Peninsula of Egypt on Saturday, October 31, 2015 at 04:12 Zulu (Greenwich Mean Time, GMT) or 12:12 am ET. 

The crew told air traffic control in the region they had technical problems.

The flight was reported to be at 31,000 feet, when it disappeared from the radar screens after 23 minutes of flight. Flight-tracking service FlightRadar24 said the plane was losing altitude at about 6,000 feet per minute before the signal was lost, Reuters reported.

Specifically, “FlightRadar24 acquired a signal from the aircraft shortly after takeoff and tracked it until 04:13:22 Zulu (12:13 am ET). At the time of last contact, FlightRadar24 were receiving a signal from the aircraft to three of its receivers, all of which stopped receiving data from the aircraft at the same time. The chart below represents the final data FlightRadar24 received from the aircraft. At no time did we receive a 7700 squawk from Metrojet flight 7K-9268.” 

Flightradar24 Tracking of Metrojet 7K-9268

The Russian air carrier, Metrojet, whose Airbus A321-231 crashed in the Sinai region on Saturday, says the aircraft was in good shape and the pilot was experienced.

In a statement on its website, Moscow-based Metrojet says the Airbus A321-231 received required factory maintenance in 2014.

The statement also identified the captain of Metrojet flight 7K-9268 was Valery Nemov, who reported technical problems from the flight deck and requested to return to Sharm el Sheikh over the Sinai Peninsula of Egypt. 

Egyptian media reports, referring to an Egyptian government meeting, that the flight crew reported trouble with the IAE A.G. V2533-A5 turbofan engines, then subsequently lost control of the aircraft, and flight deck communication ceased.

This is confirmed by Egypt’s Civil Aviation Authority’s, Mohamed Hossam Kemal, who told media at a news conference today that there was no Mayday Call from the flight deck, and communication with the Airbus A321-231 was normal until the airliner disappeared from radar.

“The plane did not request a change of route,” Kemal said (via Reuters).

It is being preliminarily surmised in media reports that a probable cause of the crash is the Airbus A321-231 slowed significantly at 31,000 feet and may have gone into an aerodynamic stall, as a result of “technically malfunctioning” turbofan engine stall and surge.

Such a clear-weather, high-altitude cruise flight occurrence of “literally falling out of the sky” is most extremely rare.

Officials say they recovered the aircraft’s flight’s recorders, or “black box,” Fox News reports, which will confirm exactly what occurred during the communication-silence “hot cockpit” final moments of Metrojet flight 7K-9268.

Egypt’s Accident Investigation Commission has initiated an official crash investigation into Metrojet flight 7K-9268. The chairman of the commission stated “preliminary facts point towards a technical failure.”

Turbofan engines could in very rare instances perhaps encountered deeper combustion instability, and even more critical, axial-flow compressor instability, resulting in “engine surge” – an engine air flow reversal pre-induced by “rotating stall” – an engine thrust reducer. Such engine dynamic instabilities are altogether rare catastrophic turbofan engine events during airborne takeoff, and again most extremely rare during high-altitude cruise at 31,000 feet, which typically induces aerodynamic stall of an airliner (see a brief detailed explanation for laypersons of these rare catastrophic turbofan engine instabilities in the Appendix section).
During such circumstances of engine surge instability, the pilots would then immediately have to shut off the turbofan engine, and immediately attempt to land the airliner with a single turbofan engine, provided it is in functioning operation. This is how these massive jumbo commercial passenger airliners are designed, manufactured, and tested to do.
Lufthansa and Air France announced they are going to “avoid over-flying the Sinai until the cause of the crash has been determined.” In addition, warnings have been issued until further notice by the United States Federal Aviation Administration to U.S. air carriers, as well as, by Germany to German air carriers to operate all flights above 26,000 feet, while air traveling over the Sinai.

Metrojet’s Airbus A321-231, powered by IAE A.G. V2533-A5 turbofan engines, was originally built and delivered/leased to Middle East Airlines (MEA), Registration number F-OHMP, on May 27, 1997, later it was leased to Onur Air, Registration number TC-OAE, and finally, the Russian Metrojet air carrier under its last Registration number EI-ETJ on May 27, 1997. The airliner had been also briefly in service with Saudi Arabian Airlines and Kolavia, and had accumulated approximately 55,772 flight hours in 21,175 flight cycles.

Metrojet flight 7K-9268 Captain Valery Nemov had 12,000 air hours of flying experience, including 3,860 hours flying Airbus A321 airliners.

Airbus said the aircraft was 18 years old and had been operated by Metrojet since 2012, Reuters reported. The plane had accumulated around 56,000 flight hours in nearly 21,000 flights.

Russian media said the airliner was a charter flight under contract with the Brisco tour company in St. Petersburg.

Ayman al-Muqadem, an Egyptian official with the government’s Aviation Incidents Committee, said the plane’s pilot, before losing contact, had radioed that the aircraft was experiencing technical problems and that he intended to attempt a landing at the nearest airport.

It was not immediately possible to independently confirm that technical problems caused the plane to crash.

The wife of the co-pilot of Metrojet flight 7K-9268 said her husband had complained about the plane’s condition,” according to a Russian TV channel (via Associated Press).

State-controlled NTV ran an interview Saturday with Natalya Trukhacheva, identified as the wife of Metrojet flight 7K-9268 co-pilot, Sergei Trukachev. She said that a daughter “called him up before he flew out. He complained before the flight that the technical condition of the aircraft left much to be desired.”

Earlier, Egyptian Aviation Incidents Committee, Ayman al-Muqadem told local media that the plane had briefly lost contact but was safely in Turkish airspace. The aircraft crashed at a site near the al-Arish airport, Ayman al-Muqadem said.

Egyptian authorities have said the aircraft had successfully undergone technical checks while at Sharm el-Sheikh’s airport. A technical committee from the company was headed to Sharm el-Sheikh to collect security camera footage of the Airbus A321-231, while it sat at the airport, including operations to supply the airliner with fuel and passenger meals, as well as security checks, he said.

The scattered wreckage of the Airbus A321-231 airliner was later located by military forces in the mountains of the Sinai about 20 nautical miles south of el-Arish (Sinai, Egypt, shown on the map above) on the coast of the Mediterranean Sea. Read more also on CNN.

A security officer at the crash site who spoke to Reuters on condition of anonymity described it as “tragic.”

“A lot of dead on the ground and many who died (were) strapped to their seats,” the officer said. “The plane split into two, a small part on the tail end that burned and a larger part that crashed into a rock. We have extracted at least 100 bodies and the rest are still inside.”

Egyptian Prime Minister Sherif Ismail (below) visited the crash site today with several cabinet ministers on a private jet, Egypt’s tourism ministry said, according to Reuters. He told a news conference today, “there did not appear to be any unusual activity behind the crash, but the facts would not be clear until further investigations had been carried out.”

metrojet_a321_crashsite 5

metrojet_a321_crashsite 3

Metrojet Airbus A321 Reg #EI-ETJ -- 3

Photo Credit: Alamy Live News. Metrojet’s Airbus A321-231, Registration number EI-ETJ, performing as flight 7K-9268, flying out of Moscow earlier this month.

The Russian Embassy in Cairo along with Egyptian security and military officials told the Associated Press there were no survivors and that all on board have died in the tragic crash.

Reuters quoting an Egyptian Official, who requested anonymity, involved in the ongoing rescue operation, says “the aircraft has broken up in two major parts, a small part being the tail plane caught fire, the other larger part impacted a rock.”

There are now reports of bodies being recovered. “The bodies of 150 victims, some still strapped to their seats, had been pulled from the wreckage,” Sky News reported, as 50 ambulances have been dispatched to the crash site.

Egypt’s Prime Minister Sherif Ismail reported that 129 bodies have been recovered and flown by helicopters to Cairo.

Metrojet Airbus A321 Reg #EI-ETJ -- 6

Photo Credit: Planespotters.net. Metrojet’s Airbus A321-231, Registration number EI-ETJ, performing as flight 7K-9268.

There is no evidence of hostile or missile activity around the flight path of the Airbus A321-231. Russia’s Transport Ministry called a video surfacing in the Internet claiming to show the shoot down of Metrojet flight 7K-9263 by Islamic State as “not credible and fabricated.”

An Egyptian aviation ministry statement said, “Egyptian military search and rescue teams found the wreckage of the passenger jet in the remote mountainous Hassana area 44 miles south of the city of el-Arish, an area in northern Sinai where Egyptian security forces are fighting a burgeoning Islamic militant insurgency led by a local affiliate of the extremist Islamic State group.”

The group claimed responsibility for downing the jet, Sky News reported.

The Wilayat Sinai group claimed on Twitter Saturday that “the fighters of the Islamic State were able to down a Russian plane over Sinai province that was carrying over 220 Russian crusaders. They were all killed, thanks be to God.” The statement was also posted on a website that serves as an unofficial news agency for the terror group, Sky News reported, adding that the claim has not been verified and it is unclear whether Sinai militants have the capability to attack a plane flying at a high altitude. 

Separately, Russia’s top investigative body opened its own investigation into the crash. 

Militants in northern Sinai have not to date shot down commercial airliners or fighter-jets. There have been persistent media reports that they have acquired Russian shoulder-fired, anti-aircraft missiles. But these types of missiles can only be effective against low-flying aircraft or helicopters. In January 2014, Sinai-based militants claimed to have shot down a military helicopter; Egyptian officials at the time acknowledged the helicopter had crashed, but gave no reason.

Click here for more on Sky News.

The Associated Press is credited to this report.


Photo Credit: 2014 International Aero Engines (IAE) A.G. V2533-A5 series turbofan engine (cutaway)


How do aircraft engines achieve catastrophic mechanical failure and how can this be mitigated?

Air enters the IAE A.G. V2533-A5 turbofan engine (cutaway shown above) through the front fan section (indicated in the photo below on a Pratt and Whitney JT9D-7R4D) at a mass flow rate of about a ton of air per second.

Five parts of this massive volume of air passes bypasses over the engine core into an exit nozzle past the turbine section, producing a substantially large amount of exit thrust. Whereas, one part of the inlet fan volume of air passes into the engine core begin at the compressor section.

From here air then continues to flow into the combustion chamber (where it is mixed with fuel for combustion).

Subsequently, those combusted, hot gases pass into the turbine section (which not only produces additional exit thrust force of the engine, but also the turbine section serves to turn the engine core shaft, which turns the compressor blades inside the compression section and also the fans blades inside the fan section, and thus, start all over again the dynamic loop of how an aircraft engine properly operates).

The rotor blades in the turbine get very hot at about 1,800 degrees Kelvin or even more, so it is necessary to cool the turbine blades based on limiting thermal restrictions on material science. The tangential on-board injector’s job is to channel cool air from the compressor section into passages between the turbine blades in the turbine section.

Here is a cut-away of an actual IAE A.G. V2533-A5 turbofan engine in a museum, marked it up to help us see where the main engine components of the fan, compressor (including the air-fuel combustion chamber), and turbine sections are (including the identified portion of a Pratt and Whitney JT9D-7R4D engine that landing on Church and Murray Street, below the World Trade Center fire on 9-11):

PW_jt9d_cutaway_high 2

The operating range of aircraft turbofan engine compression systems is limited by two classes of aerodynamic instabilities (Fig. 1) known as rotating stall and surge [1].

Rotating stall is a multidimensional instability in which regions of low or reversed mass flow (i.e., stall cells) propagate around the compressor annulus due to incidence variations on adjacent airfoils [2–5].

Surge is primarily a one-dimensional instability of the entire pumping system (compressor, ducts, combustion chamber, and turbine). It is characterized by axial pulsations in annulus-averaged mass flow, including periods of flow reversal through the machine.

In high-speed compressor hydrodynamics across compressible flow regimes [6], rotating stall is generally encountered first, which then (loosely) “triggers” surge (often after a few rotor revolutions [2]).

This work [13] proposes schemes to passively control compressible rotating stall of high-speed compressors.

Nonetheless, with either instability, the compression system experiences a substantial loss in performance and operability, which sometimes result in catastrophic mechanical failure.

An experience-based approach for avoiding such performance loss is to operate the compressor at a safe range from the point of instability onset (i.e., imposing a stall margin). The stall margin ensures that the engine can endure momentary off-design operation. The margin also reduces the available pressure rise and efficiency of the machine.

It is proposed here [13] that incorporating tailored structures and aeromechanical feedback controllers, locally-sensed by unstable compressible perturbations in annulus pressure, and actuated by non-uniformities in the high-speed flow distribution around the annulus, can be shown to inhibit the inception of a certain class of modal (long wave) stall of high-speed compressor devices. As a result, the stable operating range will be effectively extended allowing higher compressible performance and operability.

The fundamental proposition here [13] is high-speed stall onset just does not happen—it is triggered by an interdependent compressibility chain of critical Reynolds (boundary layer) and Mach (kinetic-thermal energy transfer) events. The commencement of these interdependent Reynolds and Mach events can be passively controlled, once their proportional sensitivity are monitored, sensed, and mechanically mitigated adequately in balance of performance, operability, weight, and reliability integrated with more conventional schedule-type control to justify the risk of such passive approaches offered herein.

In theory, fundamentals of a number of sensor-actuator schemes for rotating stall control were originally proposed early-on in Hendricks and Gysling [7]. In practice, a passive stall control program [13] could potentially be integrated with conventional control schedules of adequate change of fuel valve position, bleed valves, and re-staggered stator programs developed appropriately for profitable usage on compression systems operating in a highly-sensed compressible flow environment.


Photo Credit: Pratt & Whitney V2533-A5 series turbofan engine

Fundamental References for Additional Readings in the Field of Aircraft Engine Propulsion Stability

  1. Emmons, H. W., Pearson, C. E., and Grant, H. P., 1955, ‘‘Compressor Surge and Stall Propagation,’’ Trans. ASME, 77, pp. 455–469.

  2. Greitzer, E. M., 1976, ‘‘Surge and Rotating Stall in Axial Flow Compressors, Part I & II,’’ ASME J. Eng. Power, 99, pp. 190–217.

  3. Greitzer, E. M., 1980, ‘‘Review: Axial Compressor Stall Phenomenon,’’ ASME J. Fluids Eng., 102, pp. 134–151.

  4. Greitzer, E. M., 1981, ‘‘The Stability of Pumping Systems, The 1980 Freeman Scholar Lecture,’’ ASME J. Fluids Eng., 103, pp. 193–242.

  1. Day, I. J., 1993, ‘‘Stall Inception in Axial Flow Compressors,’’ ASME J. Turbomach., 115, pp. 1–9.

  2. Gysling, D. L. et al., 1991, ‘‘Dynamic Control of Centrifugal Compressor Surge Using Tailored Structures,’’ ASME J. Turbomach., 113, pp. 710–722.

  1. Gysling, D. L., and Greitzer, E. M., 1995, ‘‘Dynamic Control of Rotating Stall in Axial Flow Compressors Using Aeromechanical Feedback,’’ ASME J. Turbomach., 117, pp. 307–319.

  2. Moore, F. K., 1984, ‘‘A Theory of Rotating Stall of Multistage Compressors—Parts I – II – III,’’ ASME J. Eng. Gas Turbines Power, 106, pp. 313–336.

  1. Moore, F. K., and Greitzer, E. M., 1986, ‘‘A Theory of Post Stall Transients in Axial Compression Systems: Part I—Development of Equations,’’ ASME J. Eng. Gas Turbines Power, 108, pp. 68–76.

  2. Greitzer, E. M., and Moore, F. K., 1986, ‘‘A Theory of Post-Stall Transients in Axial Compression Systems: Part II—Application,’’ ASME J. Eng. Gas Tur- bines Power, 108, pp. 231–239.

  3. Haynes, J. M., Hendricks, G. J., and Epstein, A. H., 1994, ‘‘Active Stabilization of Rotating Stall in a Three-Stage Axial Compressor,’’ ASME J. Turbomach., 116, pp. 226–239.

  1. Longley, J. P., 1994, ‘‘A Review of Non-Steady Flow Models for Compressor Stability,’’ ASME J. Turbomach., 116, pp. 202–215.

  2. McGee, O. G., and Coleman, K. L., 2013, “Aeromechanical Control of High-Speed Axial Compressor Stall and Engine Performance—Part I: Control-Theoretic Models,” ASME J. Fluids Eng., 135, March 2013. Coleman, K.L., and McGee, O.G., 2013, “Aeromechanical Control of High-Speed Axial Compressor Stall and Engine Performance—Part II: Assessments of Methodologies,” ASME J. Fluids Eng., 135, May 2013.

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