Civil Aviation Development & Discussion

The Technology & Economic Forum is a venue to discuss issues pertaining to Technological and Economic developments in India. We request members to kindly stay within the mandate of this forum and keep their exchanges of views, on a civilised level, however vehemently any disagreement may be felt. All feedback regarding forum usage may be sent to the moderators using the Feedback Form or by clicking the Report Post Icon in any objectionable post for proper action. Please note that the views expressed by the Members and Moderators on these discussion boards are that of the individuals only and do not reflect the official policy or view of the Bharat-Rakshak.com Website. Copyright Violation is strictly prohibited and may result in revocation of your posting rights - please read the FAQ for full details. Users must also abide by the Forum Guidelines at all times.
Austin
BRF Oldie
Posts: 22734
Joined: 23 Jul 2000 11:31

Re: Civil Aviation Development & Discussion

Postby Austin » 09 Feb 2019 16:10

The Jumbo Jet: 50 Years In the Sky


Singha
BRF Oldie
Posts: 64520
Joined: 13 Aug 2004 19:42
Location: the grasshopper lies heavy

Re: Civil Aviation Development & Discussion

Postby Singha » 09 Feb 2019 21:51

it seems DGCA has restricted the ETOPS to 60min not just for Indigo/Go A321neo but Jet airways 737MAX also.

so mainly they cannot be used to port blair and on routes to ASEAN/Gulf as there are some time in route where nearest diversionary airport is >60 mins out.

normally getting a 120min ETOPS was considered routine for this family of jet.

Austin
BRF Oldie
Posts: 22734
Joined: 23 Jul 2000 11:31

Re: Civil Aviation Development & Discussion

Postby Austin » 09 Feb 2019 22:25

Good , Better Safe than Sorry

Singha
BRF Oldie
Posts: 64520
Joined: 13 Aug 2004 19:42
Location: the grasshopper lies heavy

Re: Civil Aviation Development & Discussion

Postby Singha » 10 Feb 2019 00:04

Jet has some 200 MAX on order :)

Austin
BRF Oldie
Posts: 22734
Joined: 23 Jul 2000 11:31

Re: Civil Aviation Development & Discussion

Postby Austin » 10 Feb 2019 10:34

Singha wrote:Jet has some 200 MAX on order :)


Yes , Jet is total Boeing and 737 wheather NG or MAX is...not very comfortable to fly in A320 series

I believe the 737MAX is more due to Lion AirCrash and MCAS issue then any Engine problem which I am not aware of or may be DGCA is trying to do Equal Equal :rotfl:
Last edited by Austin on 10 Feb 2019 14:08, edited 1 time in total.

Austin
BRF Oldie
Posts: 22734
Joined: 23 Jul 2000 11:31

Re: Civil Aviation Development & Discussion

Postby Austin » 10 Feb 2019 10:34

Good View of Business End of MS-21-300 active sidestick controllers

https://twitter.com/UAC_Russia_eng/stat ... 7782713347

Austin
BRF Oldie
Posts: 22734
Joined: 23 Jul 2000 11:31

Re: Civil Aviation Development & Discussion

Postby Austin » 10 Feb 2019 21:16

:lol:
Image

Austin
BRF Oldie
Posts: 22734
Joined: 23 Jul 2000 11:31

Re: Civil Aviation Development & Discussion

Postby Austin » 10 Feb 2019 21:18

Austin wrote:Good View of Business End of MS-21-300 active sidestick controllers

https://twitter.com/UAC_Russia_eng/stat ... 7782713347


Came across this informative write up on development of FBW control system for MS-21 , Not in english but using translator should be a good read

Fly on the wire: innovative control system MS-21 increases safety


https://uacrussia.livejournal.com/84288.html

Austin
BRF Oldie
Posts: 22734
Joined: 23 Jul 2000 11:31

Re: Civil Aviation Development & Discussion

Postby Austin » 10 Feb 2019 22:26

How We Ferried a Daher TBM 910 from France to California




A single engine type but travels long distance in cold and nasty weather .....reliable bird

chola
BRF Oldie
Posts: 3091
Joined: 16 Dec 2002 12:31
Location: USA

Re: Civil Aviation Development & Discussion

Postby chola » 11 Feb 2019 01:16

Let this serve as a kick-in-our-pants:

https://mobile.twitter.com/HenriKenhmann/status/1094627571705073666

East Pendulum
@HenriKenhmann
Trois C919 - 102, 103, 104 - dans la FAL à Shanghai.

Image


Time to get at least a desi regional jet going.

Austin
BRF Oldie
Posts: 22734
Joined: 23 Jul 2000 11:31

Re: Civil Aviation Development & Discussion

Postby Austin » 11 Feb 2019 10:11

IndiGo, Jet hit by DGCA rule barring longer Neo, MAX Flights

https://economictimes.indiatimes.com/in ... 909814.cms

SriKumar
BRFite
Posts: 1652
Joined: 27 Feb 2006 07:22
Location: sarvatra

Re: Civil Aviation Development & Discussion

Postby SriKumar » 11 Feb 2019 10:50

Singha wrote:it seems DGCA has restricted the ETOPS to 60min not just for Indigo/Go A321neo but Jet airways 737MAX also.
Well...it is not acceptable that new control procedures that override pilot judgement was introduced and pilots were not educated about it in big red letters. It seems that pilot overrides were further overridden by the control law. And then they try to say that it was mentioned all along, when it actually wasn't. DGCA is well within its rights to put restrictions till all Jet pilots are fully trained in all the new 'features' known and as yet unknown. The Lion Air way of finding out about a new feature is unacceptable

Austin
BRF Oldie
Posts: 22734
Joined: 23 Jul 2000 11:31

Re: Civil Aviation Development & Discussion

Postby Austin » 11 Feb 2019 11:06

Agreed . Unless there is full clarity on Lion Air Crash and subsequent fix/training the restrictions should remain

JMT if there was to be a full computer control while stall instead of letting the pilot deal with it and in most accident cases either the pilot did not know what to do or simply erred on SOP making even least difficult situation irrecoverable.

Why cant they have a TVC on Turbofan engine to deal with Stall or Post Stall manouvers , Because in most cases the control surface becomes inaffective as in case of French A330 at high altitude ( coffin corner ) or even when the aircraft is at lower altitude.

Why cant they have a combination of TVC and Control law they uses Engine and what ever control surfaces works to deal with Stall situation ?

Dileep
BRF Oldie
Posts: 5491
Joined: 04 Apr 2005 08:17
Location: Dera Mahab Ali धरा महाबलिस्याः درا مهاب الي

Re: Civil Aviation Development & Discussion

Postby Dileep » 11 Feb 2019 13:04

It is way better to avoid a stall than find ways to recover, especially for commercial aircraft. Also, it is not the absence of maneuverability the problem during stall. It is the absence of 'lift'. A controlled dive is pretty much the only thing that can recover from a stall. Even our beloved Rambha with TVC takes a dive after the crazy 'free fall' to recover.

Rather than adding TVC with increased capital and operating cost and reducing reliability, the stall sensing and mitigation sensors and algorithms must be improved. There are a number of possible inputs to the decision loop, including engine power, AoA, Airspeed, Stall sensor, Altimeter, Terrain data (don't dive into the mountain) and whatnot.

chetak
BRF Oldie
Posts: 18165
Joined: 16 May 2008 12:00

Re: Civil Aviation Development & Discussion

Postby chetak » 11 Feb 2019 19:56

Behind the Lion Air Crash, a Trail of Decisions Kept Pilots in the Dark






Behind the Lion Air Crash, a Trail of Decisions Kept Pilots in the Dark


Boeing’s 737 Max is the latest version of a plane that first went into service half a century ago.



Image

Boeing’s 737 Max is the latest version of a plane that first went into service half a century ago.


By James Glanz, Julie Creswell, Thomas Kaplan and Zach Wichter
Feb. 3, 2019


In the brutally competitive jetliner business, the announcement in late 2010 that Airbus would introduce a more fuel-efficient version of its best-selling A320 amounted to a frontal assault on its archrival Boeing’s workhorse 737.

Boeing scrambled to counterpunch. Within months, it came up with a plan for an upgrade of its own, the 737 Max, featuring engines that would yield similar fuel savings. And in the years that followed, Boeing pushed not just to design and build the new plane, but to persuade its airline customers and, crucially, the Federal Aviation Administration, that the new model would fly safely and handle enough like the existing model that 737 pilots would not have to undergo costly retraining.

Boeing’s strategy set off a cascading series of engineering, business and regulatory decisions that years later would leave the company facing difficult questions about the crash in October of a Lion Air 737 Max off Indonesia.

The causes of the crash, which killed 189 people, are still under investigation. Indonesian authorities are studying the cockpit voice recorder for insights into how the pilots handled the emergency, and are examining Lion Air’s long history of maintenance problems.

But the tragedy has become a focus of intense interest and debate in aviation circles because of another factor: the determination by Boeing and the F.A.A. that pilots did not need to be informed about a change introduced to the 737’s flight control system for the Max, some software coding intended to automatically offset the risk that the size and location of the new engines could lead the aircraft to stall under certain conditions.

That judgment by Boeing and its regulator was at least in part a result of the company’s drive to minimize the costs of pilot retraining. And it appears to have left the Lion Air crew without a full understanding of how to address a malfunction that seems to have contributed to the crash: faulty data erroneously indicating that the plane was flying at a dangerous angle, leading the flight control system to repeatedly push the plane’s nose down.

Understanding how the pilots could have been left largely uninformed leads back to choices made by Boeing as it developed the 737 Max more than seven years ago, according to statements from Boeing and interviews with engineers, former Boeing employees, pilots, regulators and congressional aides.

Those decisions ultimately prompted the company, regulators and airlines to conclude that training or briefing pilots on the change to the flight control system was unnecessary for carrying out well-established emergency procedures.

The story of the change to that system, and how it came to play a central role in the Lion Air crash, shows how safety on modern jetliners is shaped by a complex combination of factors, including fierce industry competition, technological advances and pilot training. It illustrates how, in the rare instances when things go awry, the interplay of those factors can create unintended and potentially fatal consequences.

The crash has raised questions about whether Boeing played down or overlooked, largely for cost and competitive reasons, the potential dangers of keeping pilots uninformed about changes to a critical element of the plane’s software.

And it has put a new focus on whether the F.A.A. has been aggressive enough in monitoring Boeing in an era when technology has made airliners both remarkably reliable and increasingly complicated. European regulators initially disagreed with the F.A.A.’s judgment about the need for additional training but ultimately went along, a pilot familiar with the certification process said, while regulators in Brazil broke with the F.A.A. and required that pilots be made familiar with the change.

Boeing has taken the position that the pilots of the Lion Air flight should have known how to handle the emergency despite not knowing about the modification. The company has maintained that properly following established emergency procedures — essentially, a checklist — long familiar to pilots from its earlier 737s should have allowed the crew to handle a malfunction of the so-called maneuvering characteristics augmentation system, known as M.C.A.S., whether they knew it was on the plane or not.

Boeing said that various systems on both the Max and its previous generation 737 can push the nose down. “Regardless of cause,” the company said, the flight crew should go through the checklist, “which is contained in existing procedures.”

The company said that in developing training materials for the 737 Max, it followed long-established practices. “The process ensures flight crews have all the information to safely operate the airplane,” Boeing said, “and for maintenance and fleet chiefs to understand how to ensure the airplanes are serviceable.”

But in the aftermath of the crash, Boeing plans to release a software upgrade for the 737 Max, according to a person briefed on the matter, though it is not clear how the upgrade will affect M.C.A.S. Boeing said that it “continues to evaluate the need for software or other changes as we learn more from the ongoing investigation.”

The F.A.A. declined to comment about the crash but acknowledged that its own role was being examined.

“The F.A.A.’s review of the 737 Max’s certification is a part of an ongoing investigation with the N.T.S.B. and Indonesian civil aviation authorities,” the agency said in a statement, referring to the National Transportation Safety Board. “We cannot provide details of that review until the investigation is complete.”

Boeing’s position has left many pilots angry and concerned.

“Any time a new system is introduced into an airplane, we are the people responsible for that airplane,” said Jon Weaks, the president of the Southwest Airlines Pilots Association.

Referring to the addition of M.C.A.S., Mr. Weaks added, “We felt and we feel that we needed to know about that, and there’s just no other way to say it.”

John Barton, a 737 captain who spoke on the condition that the airline he flies for not be identified, said the blame started with Boeing and the F.A.A. but extended to airlines and pilot unions.

“Many pilots feel the training was inadequate, and therefore it appears to me that Boeing, the F.A.A., the airline training centers and possibly the unions themselves are culpable for the incident that happened,” he said.

Saving Airlines Time and Money

In designing the 737 Max, Boeing was selling airlines on the aircraft’s fuel savings, operating cost reductions and other improvements. But at the same time, it was trying to avoid wholesale aerodynamic and handling changes that would spur the F.A.A. to determine that existing 737 pilots would need substantial new and time-consuming training.

Internally, a primary requirement for the Max was that no design change could cause the F.A.A. to conclude that airline pilots must be trained on the system differences between the then-current version of the plane, the 737 NG, and the Max using simulators, said Rick Ludtke, a flight crew operations engineering analyst who was involved in devising some of the other new safety features on the 737 Max.

By limiting the differences between the models, Boeing would save airlines time and money by not putting their 737 pilots in simulators for hours to train on the new aircraft, making a switch to the Max more appealing.

“Part of what we wanted to accomplish was seamless training and introduction for our customers, so we purposely designed the airplane to behave in the same way,” Dennis A. Muilenburg, Boeing’s chief executive, said on CNBC in December in response to a question about whether the company wanted to hold down training costs. “So even though it’s a different airplane design, the control laws that fly the airplane are designed to make the airplane behave the same way in the hands of the pilot.”

But Boeing’s engineers had a problem. Because the new engines for the Max were larger than those on the older version, they needed to be mounted higher and farther forward on the wings to provide adequate ground clearance.

Early analysis revealed that the bigger engines, mounted differently than on the previous version of the 737, would have a destabilizing effect on the airplane, especially at lower speeds during high-banked, tight-turn maneuvers, Mr. Ludtke said.

The concern was that an increased risk of the nose being pushed up at low airspeeds could cause the plane to get closer to the angle at which it stalls, or loses lift, Mr. Ludtke said.

After weighing many possibilities, Mr. Ludtke said, Boeing decided to add a new program — what engineers described as essentially some lines of code — to the aircraft’s existing flight control system to counter the destabilizing pitching forces from the new engines.

That program was M.C.A.S.


M.C.A.S., according to an engineer familiar with the matter, was written into the so-called control law, the umbrella operating system that, among other things, keeps the plane in “trim,” or ensures that the nose is at the proper angle for the plane’s speed and trajectory. In effect, the system would automatically push the nose down if it sensed that the plane’s angle was creating the risk of a stall.

Both M.C.A.S. and the so-called speed trim system — the automatic stabilizer controls used on the 737 NG and earlier versions — operate primarily via the horizontal section of the 737’s tail fin, which consists of a relatively narrow “elevator” in the back and a larger surface called a stabilizer in the front. In manual flight, pilots move the nose up and down by pulling or pushing on a control column, also called a yoke, to pivot the elevator one way or the other.

Ordinarily, the stabilizers accomplish a more subtle task, making sure that the up or down forces on the tail keep the plane balanced around its center of gravity. Either pilot can control the stabilizers electrically using switches at the top of the yoke.

M.C.A.S. was written to use the stabilizers in a different way.

The modified system’s first task was to automatically offset the stall risk created by the change in the size and location of the engines.

“M.C.A.S. was necessary then for the airplane to be certified by the F.A.A. to have met all of the regulatory design requirements for stability and control,” Mr. Ludtke said.

In addition to addressing safety, M.C.A.S. also let the plane handle much like its predecessors from a pilot’s perspective. In assessing whether existing 737 pilots would need to spend hours training on simulators to fly the Max, the F.A.A. would take into account how similarly the two versions handled.


Boeing said that the modification “improves aircraft handling characteristics” and decreases “pitch-up tendency” only in unusual circumstances. “It does not control the airplane in normal flight,” the company said.

The F.A.A. would also determine what kind of training would be required for pilots on specific design changes to the Max compared with the previous version. Some changes would require training short of simulator time, such as computer-based instruction.

“I would think this is one of those systems that the pilots should know it’s onboard and when it’s activated,” said Chuck Horning, the department chairman for aviation maintenance science at Embry-Riddle Aeronautical University.

That was not the choice that Boeing — or regulators — would make.

The F.A.A. Sides With Boeing

Ultimately, the F.A.A. determined that there were not enough differences between the 737 Max and the prior iteration to require pilots to go through simulator training.

While the agency did require pilots to be given less onerous training or information on a variety of other changes between the two versions of the plane, M.C.A.S. was not among those items either.

The bottom line was that there was no regulatory requirement for Boeing or its airline customers to flag the changes in the flight control system for its pilots — and Boeing contended that there was no need, since, in the company’s view, the established emergency procedures would cover any problem regardless of whether it stemmed from the original system or the modification.

At least as far as pilots knew, M.C.A.S. did not exist, even though it would play a key role in controlling the plane under certain circumstances.

Boeing did not hide the modified system. It was documented in maintenance manuals for the plane, and airlines were informed about it during detailed briefings on differences between the Max and earlier versions of the 737.

But the F.A.A.’s determination that the system did not have to be flagged for pilots gave pause to some other regulators.


Across the Atlantic, the European Aviation Safety Agency, the European Union’s equivalent of the F.A.A., had qualms, according to a pilot familiar with the European regulator’s certification process.

At first, the agency was inclined to rule that M.C.A.S. needed to be included in the flight operations manual for the Max, which in turn would have required that pilots be made aware of the new system through a classroom or computer course, the pilot said. But ultimately, he said, the agency did not consider the issue important enough to hold its ground, and eventually it went along with Boeing and the F.A.A.

When Brazilian regulators published their required training for pilots, they singled out M.C.A.S. as one of the changes that needed to be flagged.

The F.A.A. said that “other countries base their standards on conditions specific and unique to each nation.”

Among the many unanswered questions raised by the crash is the degree to which Boeing and the F.A.A. considered what would happen in the event that M.C.A.S. — or the sensors that fed the system information about the plane — were to malfunction.

In the Lion Air crash, one of the primary theories is that the system was receiving faulty data about the angle of the plane from what is known as an angle of attack sensor, vanelike devices on either side of the fuselage that measure how much the plane’s nose is pointing up or down. Preliminary findings from the investigation suggested that the sensor on the pilot’s side of the plane was generating erroneous data.

In designing the 737 Max, Boeing decided to feed M.C.A.S. with data from only one of the two angle of attack sensors at a time, depending on which of two, redundant flight control computers — one on the captain’s side, one on the first officer’s side — happened to be active on that flight.

That decision kept the system simpler, but also left it vulnerable to a single malfunctioning sensor, or data improperly transferred from it — as appeared to occur on the day of the crash.

There is no evidence that Boeing did flight-testing of M.C.A.S. with erroneous sensor data, and it is not clear whether the F.A.A. did so. European regulators flight-tested the new version of the plane with normal sensor data feeding into M.C.A.S. but not with bad data, the pilot familiar with the European certification process said.

The stabilizers on older models could have moved in unpredictable and dangerous ways as well, because of factors like electrical shorts, bad sensor data or computer problems. Boeing reasoned, according to people the company has briefed, as well as a bulletin it sent airlines after the crash, that the emergency procedure for malfunctioning speed trim and other stabilizer problems on the earlier 737s would work on the Max for problems related to M.C.A.S., too.

The centerpiece of that procedure is to switch off two “stabilizer trim cutout” switches on the central console of the cockpit, and then flip open the handles on wheels near the knees of the captain and first officer. By cranking those wheels, the pilots can adjust the stabilizers manually in an effort to keep the plane from pitching up or down.

The Role of Pilots

At the heart of the debate is whether the pilots would have responded differently if they knew the plane’s nose was being forced down specifically by M.C.A.S.

Information from the flight data recorder shows that the plane’s nose was pitched down more than two dozen times during the brief flight, resisting efforts by the pilots to keep it flying level. If M.C.A.S. was receiving faulty data indicating that the plane was pitched upward at an angle that risked a stall — and the preliminary results of the investigation suggest that it was — the system would have automatically pushed the nose down to avert the stall.

The standard checklist for dealing with that sort of emergency on the previous version of the 737 focuses on flipping the stabilizer trim cutout switches and using the manual wheels to adjust the stabilizers.

Boeing has asserted the pilots on the next-to-last flight of the same Lion Air aircraft that crashed encountered a similar, if less severe, nose-down problem. They addressed it by flipping off the stabilizer cutout switches, in keeping with the emergency checklist. Still, Indonesian investigators found, the pilots broke from the checklist by flipping the switches back on again before turning them off for the rest of the flight. That flight, with different pilots from the flight that crashed, landed safely.

Older 737s had another way of addressing certain problems with the stabilizers: Pulling back on the yoke, or control column, one of which sits immediately in front of both the captain and the first officer, would cut off electronic control of the stabilizers, allowing the pilots to control them manually.

That feature was disabled on the Max when M.C.A.S. was activated — another change that pilots were unlikely to have been aware of. After the crash, Boeing told airlines that when M.C.A.S. is activated, as it appeared to have been on the Lion Air flight, pulling back on the control column will not stop so-called stabilizer runaway.

The preliminary results of the investigation, based on information from the flight data recorder, suggested that the pilots of the doomed flight tried a number of ways to pull the nose back up as it lurched down more than two dozen times. That included activating switches on the control yoke that control the angle of the stabilizers on the plane’s tail — and when that failed to stop the problem, pulling back on the yoke.

There is no indication that they tried to flip the stabilizer cutout switches, as the emergency checklist suggests they should have. Findings from the cockpit voice recorder could establish in more detail what culpability, if any, rests with the Lion Air pilots.

Boeing’s position that following the established emergency checklist should have been sufficient understates the complexity of responding to a crisis in real time, pilots said.

Referring to Boeing’s focus on the need for pilots to flip the stabilizer cutout switches, Dennis Tajer, the spokesman for the American Airlines pilots union and a 737 pilot, said, “They are absolutely correct: Turning those two switches off will stop that aggressive action against you.”

Still, Mr. Tajer added, a pilot needs to know what systems are aboard so that they become “a part of your fiber as you fly the aircraft.”

The pilot of the plane’s next-to-last flight, in his entry into an electronic log, noted a variety of problems he had encountered, and speculated that the plane’s speed trim system — the stabilizer functions used on the 737 NG and earlier versions — was not operating correctly. But no one involved in that next-to-last flight of the doomed plane flagged M.C.A.S. or seems to have recognized that it might have been the root of that flight’s problems.

“It really tells you what professional pilots, having flown this very aircraft for the past 10 years, are feeling,” said Bjorn Fehrm, an aeronautical engineer and former fighter pilot for the Swedish air force, referring to the previous generation 737. “They have no idea Boeing has introduced something new.”

Austin
BRF Oldie
Posts: 22734
Joined: 23 Jul 2000 11:31

Re: Civil Aviation Development & Discussion

Postby Austin » 11 Feb 2019 21:27

Chetakji , I had posted this article before the curx of the matter is

There is no indication that they tried to flip the stabilizer cutout switches, as the emergency checklist suggests they should have. Findings from the cockpit voice recorder could establish in more detail what culpability, if any, rests with the Lion Air pilots.

Boeing’s position that following the established emergency checklist should have been sufficient understates the complexity of responding to a crisis in real time, pilots said.


Boeing says the established emergency checklist should have been enough to deal with issue even though the pilot was not aware of this and the way to do is to flip the stabilizer cutout switches which is part of emergency check list.

From what I recollect reading the plane had not gained much altitude and the nose dive happened dozens of time so the pilot were too busy in trying to figure out what to do about this and since they were not aware of MCAS what ever they tried was from what they knew , No time to go though the emergency check list and perhaps those check list might have contained dozens of things to check.

Boeing is trying to get away from its liability of MCAS and tying to pin this on Pilot not following SOP .......I am thinking if this argument has any merits.

Austin
BRF Oldie
Posts: 22734
Joined: 23 Jul 2000 11:31

Re: Civil Aviation Development & Discussion

Postby Austin » 11 Feb 2019 21:34

Dileep wrote:It is way better to avoid a stall than find ways to recover, especially for commercial aircraft. Also, it is not the absence of maneuverability the problem during stall. It is the absence of 'lift'. A controlled dive is pretty much the only thing that can recover from a stall. Even our beloved Rambha with TVC takes a dive after the crazy 'free fall' to recover.


Yes no two way about it that it is better to avoid a stall then to recover from it and controlled dive is the only way out but what if they are short on altitude and besides stall they are facing other issue in the cockpit , If they go for a controlled dive then they might find they have recovered but now they are too low to gain height ........This is what happened in the infamous Afghanistan 747 cargo plane crash , The CG changed due to cargo getting unbolted and they went into a stall the pilot managed to recover by diving it down but then they were too low when they barely managed to recover.
Rather than adding TVC with increased capital and operating cost and reducing reliability, the stall sensing and mitigation sensors and algorithms must be improved. There are a number of possible inputs to the decision loop, including engine power, AoA, Airspeed, Stall sensor, Altimeter, Terrain data (don't dive into the mountain) and whatnot.


Yes those Sensors , AI and other things are fine and needs to be done but adding TVC might just help if you are low on altitude or even if you are in the zone of Coffin corner , Having TVC can aid in absence of lift and lack of response from control surface.

Besides I think having a TVC can reduce the trip needed in flight and can aid in reducing flaps/control surfaces movement reducing drag and helping in improving fuel effeciency.

JMT

chetak
BRF Oldie
Posts: 18165
Joined: 16 May 2008 12:00

Re: Civil Aviation Development & Discussion

Postby chetak » 12 Feb 2019 01:02

The aircraft had two AOA indicators.

These two together provided a much needed redundancy.

This redundancy was deliberately, pushed by some wrongly reasoned engineering choice, taken away and the previously available twin AOA failure/erroneous input/sensor conflict was converted to an extremely dangerous single point failure event.

( ultimately, it was this single point failure that precipitated the chain of events that eventually led to the fatal crash, the much dreaded lining up of the holes in the swiss cheese. )

They also fiddled with the control laws to accommodate the MCAS.

This failure, no doubt, cheered on by some idiot bean counters, was compounded by the choice and extreme emphasis of a wrong design objective viz:

In assessing whether existing 737 pilots would need to spend hours training on simulators to fly the Max, the F.A.A. would take into account how similarly the two versions handled.



Also

Internally, a primary requirement for the Max was that no design change could cause the F.A.A. to conclude that airline pilots must be trained on the system differences between the then-current version of the plane, the 737 NG, and the Max using simulators, said Rick Ludtke, a flight crew operations engineering analyst who was involved in devising some of the other new safety features on the 737 Max.

But Boeing’s engineers had a problem. Because the new engines for the Max were larger than those on the older version, they needed to be mounted higher and farther forward on the wings to provide adequate ground clearance.

Early analysis revealed that the bigger engines, mounted differently than on the previous version of the 737, would have a destabilizing effect on the airplane, especially at lower speeds during high-banked, tight-turn maneuvers, Mr. Ludtke said.

The concern was that an increased risk of the nose being pushed up at low airspeeds could cause the plane to get closer to the angle at which it stalls, or loses lift, Mr. Ludtke said.

After weighing many possibilities, Mr. Ludtke said, Boeing decided to add a new program — what engineers described as essentially some lines of code — to the aircraft’s existing flight control system to counter the destabilizing pitching forces from the new engines.

That program was M.C.A.S.

M.C.A.S., according to an engineer familiar with the matter, was written into the so-called control law, the umbrella operating system that, among other things, keeps the plane in “trim,” or ensures that the nose is at the proper angle for the plane’s speed and trajectory. In effect, the system would automatically push the nose down if it sensed that the plane’s angle was creating the risk of a stall.

Both M.C.A.S. and the so-called speed trim system — the automatic stabilizer controls used on the 737 NG and earlier versions — operate primarily via the horizontal section of the 737’s tail fin, which consists of a relatively narrow “elevator” in the back and a larger surface called a stabilizer in the front. In manual flight, pilots move the nose up and down by pulling or pushing on a control column, also called a yoke, to pivot the elevator one way or the other.

Ordinarily, the stabilizers accomplish a more subtle task, making sure that the up or down forces on the tail keep the plane balanced around its center of gravity. Either pilot can control the stabilizers electrically using switches at the top of the yoke.

M.C.A.S. was written to use the stabilizers in a different way.

The modified system’s first task was to automatically offset the stall risk created by the change in the size and location of the engines.

“M.C.A.S. was necessary then for the airplane to be certified by the F.A.A. to have met all of the regulatory design requirements for stability and control,” Mr. Ludtke said.


In addition to addressing safety, M.C.A.S. also let the plane handle much like its predecessors from a pilot’s perspective. In assessing whether existing 737 pilots would need to spend hours training on simulators to fly the Max, the F.A.A. would take into account how similarly the two versions handled.


It is a fact that relocation of the larger new engines caused handling changes as well as some unfamiliar stalling characteristics which were to be compensated by the MCAS. Stall became that much more critical and trim switches became life-and-death crucial without the pilots being aware of the flight critical changes that had been made to the system and the new interplay of these components or infact the introduction of the new MCAS itself. Matters were royally fcuked up by converting the originally redundant twin AOA indicators by making them each individual and single points of failure.

Furthermore, inadequate to no flight testing was done to factor in AOA failure/erroneous input and assess its effect on the various regimes of flight.

How would the poor guy in the cockpit figure out all these things by himself, and in real time too, if he wasn't told or informed in advance or trained to handle such situations as they precipitated that fateful morning??

Had the twin AOA redundancy been maintained, a simple comparison between the two AOAs could have generated some sort of advisory/warning/alert in the cockpit
of a sensor conflict giving the pilots a more than fighting chance of recovering from the situation by allowing them to isolate the reasons much faster


Boeing and the FAA have right royally fcuked up, they are both desperately casting about to pin the blame on the pilots when the fault lies squarely on a bean counting manufacturer and its co conspirator regulator.

There is a very good case for criminal liability here and a massive class action suit but unfortunately, the dead passengers and crew are not twice born amerikis but low born, brown skinned, insignificant darkies and asians.

The powers that be would have already cut deals and paid off all interested and affected parties by now. Its the way of the world, especially that part of the world where the crash took place.

This new product development was foolishly and very hastily rushed to market, without adequate risk analysis, inadequate flight testing and with the bean counters in charge.

They feared that the airbus neo would run away with the market segment and so boeing panicked and bean counters moved in, literally, for the kill.

The FAA is usually very circumspect and certainly capable of doing a far far better job but it did a very shameful and shoddy job on the 737 max.

Avtar Singh
BRFite -Trainee
Posts: 94
Joined: 22 Jan 2017 02:07

Re: Civil Aviation Development & Discussion

Postby Avtar Singh » 12 Feb 2019 05:09

I just had a quick look at report before writing/continuing...
yes the aircraft was in a stall initially but they were quickly into loss of control/unusual attitude territory but the pilots did not recognize it….

because of everything that was going on due to initial loss of pressure data
had they the requisite training for "loss of control"/"unreliable airspeed"
all of them would have recognized what was going on
from the instruments that do not need pressure data

also left seat pilot did not do the right thing, since there is override
for one stick to take over from other. He did not press the required button
neither pilots bothered communicating with the each other

finally when the captain came back, he did not recognize the situation

they had full power on, this is an action for stall recovery and the left pilot was doing the other action for stall recovery ie pitch down…

But they were way beyond stall recovery… very high nose attitude, max power
what they needed to do was cut the power to idle and push the nose hard down...once the aircraft nose is heading towards the ground they could then recover

https://www.skybrary.aero/index.php/Rec ... _Attitudes

Counter-intuitive responses - after much routine training emphasising the recovery from the approach to the stall, which usually requires an increase in thrust and a relatively small reduction in pitch attitude, it may well be counter intuitive to use full down elevator control or to reduce thrust when recovering from a high angle of attack (AoA), especially at low altitudes


Hope you are all enjoying the flying lesson….

Yes they are/were allowed wine, it is a french thing….
But with political correctness now rampant, even the french may have changed their ways.

nachiket
Forum Moderator
Posts: 6297
Joined: 02 Dec 2008 10:49

Re: Civil Aviation Development & Discussion

Postby nachiket » 12 Feb 2019 05:29

The problem in the 737 MAX case started with the FAA IMO. They are at fault for agreeing with Boeing that no retraining of pilots was necessary before moving them from NG to MAX version. Boeing insisted on this no doubt to get an advantage in the marketplace so they will be able to advertise this to their customers and push them to buy the MAX. But the FAA should have never accepted this.

This reminds us of another infamous incident from the past regarding the McDonnell Douglas DC-10. The DC-10 cargo doors had a serious design flaw which led to the door opening in flight and the near crash of American Airlines Flight 96. When the investigation revealed the cause, the FAA should have released an Air-worthiness directive forcing all airlines to get the doors fixed from McD. But the head of McD and the head of the FAA reached a "gentleman's agreement" instead where the McD head promised to fix the doors on all customer's DC-10's without an AW directive since it would damage the DC-10's reputation and hurt its sales. What was the result? The redesign and fixes were delayed and led to the crash of Turkish Airlines 981 a full 2 years later where 346 people died.

This MCAS situation is similar. FAA gets influenced by Boeing and agrees no retraining of Pilots is necessary. The civil aviation regulators of other countries foolishly take their cue from the FAA and fall into the same trap. And the Lion Air crash is the direct result. The DC-10 issue was in 1972-74. FAA has learned nothing in the 45 years since then it seems. It is supposed to be a regulator. Not a marketing department for US aircraft manufacturers. And the regulators in other countries need to do their own due-diligence instead of relying on the FAA.

Austin
BRF Oldie
Posts: 22734
Joined: 23 Jul 2000 11:31

Re: Civil Aviation Development & Discussion

Postby Austin » 12 Feb 2019 09:21

chetak , Rightly said the engine movement had made the CG change and 737 always had low mounted wings so ground clearance for a high bypass turbofan engine was always an issue , Now this is something they cannot change short of redesigning the aircraft from scratch.

They simply wrote few lines of code in form of MCAS to make it work and either FAA willingly obliged Boeing or they were kept in the dark because of Boeing reputation they didnt bother to do a through revew and bought into Boeing PR that MAX is just another 737NG with 15 % more fuel efficient engine

I wonder of the change in CG might lead to some other issue that we may not be aware of something beyond a few line of sw in FCS can fix it ?

This is criminal negligance on part of B and FAA but since these are not some Goras there would end up with another Gentleman Agreement to cover this up

chetak
BRF Oldie
Posts: 18165
Joined: 16 May 2008 12:00

Re: Civil Aviation Development & Discussion

Postby chetak » 12 Feb 2019 11:44

Note the new high bypass repositioned engines on the 737 Max


Image

Image

737 Max.


Image

Image

737 Classic

Austin
BRF Oldie
Posts: 22734
Joined: 23 Jul 2000 11:31

Re: Civil Aviation Development & Discussion

Postby Austin » 12 Feb 2019 12:58

737 was made to fly with Turbojet engine for its time but as soon as it started moving to high bypass turbofan engine with larger fan diameter they had issue with ground clearance and had to work with all sort of tricks to solve the issue.

Austin
BRF Oldie
Posts: 22734
Joined: 23 Jul 2000 11:31

Re: Civil Aviation Development & Discussion

Postby Austin » 12 Feb 2019 12:59

The 737 Classic looks more to me like NG model

Singha
BRF Oldie
Posts: 64520
Joined: 13 Aug 2004 19:42
Location: the grasshopper lies heavy

Re: Civil Aviation Development & Discussion

Postby Singha » 12 Feb 2019 13:04

i guess that explains why A320 which is taller has a round engine cowl and 737 have flattened bottom of circle.
I used to think it was some hifi american "stealth" thing going on.

some engines have sine wave type trailing edge rim at the backside ...apparently to reduce noise.

Austin
BRF Oldie
Posts: 22734
Joined: 23 Jul 2000 11:31

Re: Civil Aviation Development & Discussion

Postby Austin » 12 Feb 2019 15:30

Singha wrote:737 have flattened bottom of circle.


Watch this the reason for flattened bottom engine


Austin
BRF Oldie
Posts: 22734
Joined: 23 Jul 2000 11:31

Re: Civil Aviation Development & Discussion

Postby Austin » 12 Feb 2019 15:53

737 has two known issues

One is the engine ground clearance
the second is the lowest diameter of fuselage compared A320 and newer variant C919 and MS-21. The C919 and A320 as roughly the same diameter fuselage the MS-21 has the largest dia compared to the other 3.

Boeing has extended the length of fuselage but not possible to increase an inch of diameter without starting from scratch

Austin
BRF Oldie
Posts: 22734
Joined: 23 Jul 2000 11:31

Re: Civil Aviation Development & Discussion

Postby Austin » 12 Feb 2019 15:55

This is a good read on new entrant in narrow body C919 and MS-21 program quite detailed and updated write up

Comac C919

MS-21

nachiket
Forum Moderator
Posts: 6297
Joined: 02 Dec 2008 10:49

Re: Civil Aviation Development & Discussion

Postby nachiket » 13 Feb 2019 03:49

Austin wrote:737 was made to fly with Turbojet engine for its time but as soon as it started moving to high bypass turbofan engine with larger fan diameter they had issue with ground clearance and had to work with all sort of tricks to solve the issue.

Nitpick, but the PW JT8D-1 on the original 737 was technically a Low bypass Turbofan, not a Turbojet. But of course it had much narrower diameter than the high bypass engines that came later.

Every time there is an upgrade needed, Boeing briefly considers working on a clean sheet design before deciding to jump through hoops to somehow fit larger engines on the 737 itself. The reason the aircraft doesn't have longer landing gear is because even the original 737 wasn't a completely clean sheet design since they reused the fuselage cross section of the 727 which had rear-fuselage mounted engines and sat low to the ground. The MAX is the fourth iteration of the 737 now. I doubt there will be more.

Singha
BRF Oldie
Posts: 64520
Joined: 13 Aug 2004 19:42
Location: the grasshopper lies heavy

Re: Civil Aviation Development & Discussion

Postby Singha » 13 Feb 2019 08:00

the original 737-200 of my childhood in 80s . the back section of the engine used to fold down on landing as thrust reverser

Image

Austin
BRF Oldie
Posts: 22734
Joined: 23 Jul 2000 11:31

Re: Civil Aviation Development & Discussion

Postby Austin » 13 Feb 2019 08:30

nachi , you are right 737 is an evolution from 727 and MAX has a higher landing gear and reason why they can accomodate larger diameter engine although they move it ahead of the wing.

737 replacement has been on and off the cards many time , The latest news is they are working on 767 replacement which can compete with A321 plus variant , Boeing is worried that the NEO variant of A321 will take over the 767 customers ....... Looks again more like a panic reaction to Airbus success of NEO series.

I sincerly hope they have a 737 replacement done , This aircraft has become now a pig with a lipstick and both the Chinese and Russians have better model in every parameter compared to even MAX series , It is just the reputation and money power of Boeing that is letter the MAX sell with customer and waive FAA regulation

Singha I was recently watching a video where 737-200 was still being used think it is in Canada because it is capable to operating from unprepared airfields and its engine has a mechanism to keep foreign object out

chola
BRF Oldie
Posts: 3091
Joined: 16 Dec 2002 12:31
Location: USA

Re: Civil Aviation Development & Discussion

Postby chola » 13 Feb 2019 10:33

Not something you see everyday. Nose radar on a chini ARJ-21 regional jet. Should be a weather radar no?
Image
Image
Image

Singha
BRF Oldie
Posts: 64520
Joined: 13 Aug 2004 19:42
Location: the grasshopper lies heavy

Re: Civil Aviation Development & Discussion

Postby Singha » 13 Feb 2019 10:37

every commercial a/c has such a radar. Bendix & honeywell are important co in that space.

speed is set to lower when entering turbulent clouds with hail inside.

Austin
BRF Oldie
Posts: 22734
Joined: 23 Jul 2000 11:31

Re: Civil Aviation Development & Discussion

Postby Austin » 13 Feb 2019 11:06

The Rear Mounted Engine design seen on ARJ-21 seems to have issue with stall when flying at higher Angle , In past aircraft was lose due to same reason , Recollect reading a British Civil Aircraft under test with rear mouted engine crashed during test flight for stall.

The CG also is an issue because heavy engine is at the back then middle of the airframe. ...Now a Days only Busness Jet seems to have such an approach

chola
BRF Oldie
Posts: 3091
Joined: 16 Dec 2002 12:31
Location: USA

Re: Civil Aviation Development & Discussion

Postby chola » 13 Feb 2019 11:18

Singha wrote:every commercial a/c has such a radar. Bendix & honeywell are important co in that space.

speed is set to lower when entering turbulent clouds with hail inside.


Yah I had assume so GD, just rare to see one with the nose opened up. Too use to seeing it on fighters.


Austin wrote:The Rear Mounted Engine design seen on ARJ-21 seems to have issue with stall when flying at higher Angle , In past aircraft was lose due to same reason , Recollect reading a British Civil Aircraft under test with rear mouted engine crashed during test flight for stall.

The CG also is an issue because heavy engine is at the back then middle of the airframe. ...Now a Days only Busness Jet seems to have such an approach


It is a scaled-down copy-paste of the half-century old DC-9/MD-80 design that once was built at the McDonnell Douglas Shanghai plant during bonhomie in the 1980s. Despite the design disadvantages it is what they know, I presume.

Austin
BRF Oldie
Posts: 22734
Joined: 23 Jul 2000 11:31

Re: Civil Aviation Development & Discussion

Postby Austin » 13 Feb 2019 11:58

Yes so is C919 is a copy of A-320 having even similar dimension generally and in many cases identical

Innovation is not a Chinese forte but they copy paste it well even that is an art and science in itself

Only the Russians Innovated with Narrow body aircraft with Composite Wing a first for narrow body and largest diameter fuselage plus the PD-14 engine is comparable to PW and LEAP in virtually all aspect and active flight control

Austin
BRF Oldie
Posts: 22734
Joined: 23 Jul 2000 11:31

Re: Civil Aviation Development & Discussion

Postby Austin » 13 Feb 2019 11:58

Yes so is C919 is a copy of A-320 having even similar dimension generally and in many cases identical , they have been assembling A320 in china afterall :lol:

Innovation is not a Chinese forte in most cases but they steal and copy paste it well to the I's and T's even that is an art and science in itself , Other than CHinese and Iranians I havent seen any other nation mastering reverse engineering and C&P on large scale

Only the Russians Innovated with Narrow body aircraft with Composite Wing a first for narrow body and largest diameter fuselage plus the PD-14 engine is comparable to PW and LEAP in virtually all aspect and active flight control

chetak
BRF Oldie
Posts: 18165
Joined: 16 May 2008 12:00

Re: Civil Aviation Development & Discussion

Postby chetak » 13 Feb 2019 12:20

Austin wrote:The Rear Mounted Engine design seen on ARJ-21 seems to have issue with stall when flying at higher Angle , In past aircraft was lose due to same reason , Recollect reading a British Civil Aircraft under test with rear mouted engine crashed during test flight for stall.

The CG also is an issue because heavy engine is at the back then middle of the airframe. ...Now a Days only Busness Jet seems to have such an approach


similar problems with the french/italian ATR too, when the nose is pitched up.

chola
BRF Oldie
Posts: 3091
Joined: 16 Dec 2002 12:31
Location: USA

Re: Civil Aviation Development & Discussion

Postby chola » 13 Feb 2019 12:35

Austin wrote:Yes so is C919 is a copy of A-320 having even similar dimension generally and in many cases identical , they have been assembling A320 in china afterall :lol:

Innovation is not a Chinese forte in most cases but they steal and copy paste it well to the I's and T's even that is an art and science in itself , Other than CHinese and Iranians I havent seen any other nation mastering reverse engineering and C&P on large scale

Only the Russians Innovated with Narrow body aircraft with Composite Wing a first for narrow body and largest diameter fuselage plus the PD-14 engine is comparable to PW and LEAP in virtually all aspect and active flight control


Wrote at length about RE and ToT before. Historically given the choice to TOT or RE, chinis would rather do ToT. Look at their Flanker clones. Rapid development with the J-11B, first flight in 2002 and induction in 2007. And that was with a chini engine. Only tech transfer and OEM help could have allowed this to happen so quickly.

Same with their helo industry. Their base products there are all French ToT, especially the Dauphin (Z-9) and Super Frelin (Z-8.)

A true reverse-engineering project would be the Copyhawk Z-20 which took 30 odd years to develop and induct. But they had no choice here with the US never granting them ToT.

The ARJ-21 and C919 are a mix of cloning with a substantial degree of ToT I think. Otherwise, development would be far slower. ToT for the ARJ-21 came with the MD plant with all machinery exported from the US but that was 40 years ago. lol

But I suspect the C919 includes some modern ToT from France through the A320. French had never been shy with Cheen on tech transfer (look at above helo examples.)

Iran was able to clone a F-5 with its turbojet which is the same tech level as the J-7 which the last truly cloned chini jet. The Iranians were never able to clone the F-14 which I’m sure both Cheen and Russia had a look at too. But modern aircraft is probably impossible to clone. It would take less time to develop a new vehicle than RE something like a F-14.

Austin
BRF Oldie
Posts: 22734
Joined: 23 Jul 2000 11:31

Re: Civil Aviation Development & Discussion

Postby Austin » 13 Feb 2019 14:26

I dont blame China or Iran for cloning , You do what you can with the resources you have and in the environment you are in.

It is good to be a good cloner then be a bad or failed innovator , Chinese did what they could they copied SU/Russian , Western aircraft civil and military and improvised on it , in the sense C919 is a improvised A-320.

I dont think Airbus would give them TOT for A320 but since China assembled/build this bird over a decade they would have learnt a lot in the process perhaps even have assess to Design Data and Wind Tunnel test data and they would have validated both in their wind tunnel too .

Chinese have done transparent but deep penetration into Western society and have good relation with the MNC out there they known the people there in these companies and have big business relations , after all Chini money has been filling their bottom line and the way things operate in West the same guy who work for Airbus or Boeing then moves to Dassault or Lockheed in Defence or into Academic or Political or Babudom circle and since you know that person well since the MNC days 2 decade back and build a relationship with him you also learn from him as he moves around into these places because of your relationship and he carries your good will around.

In a way i am happy that Chini and Russia are providing a alternate to Narrow body and eventually wide body , Completion is good and the customer gains from this. Although it would take around 2 decades atleast even to capture 15 % of the market but a thousnd mile journey begins with a small step.

Boeing and Airbus Duopoly over many decades of wink wink eye eye between them and they have also co-opted their regulator to do their bidding or short change the customer or just speed through things overlooking critical aspects like case of MAX

Hopefully we start with our own 70 seater as fast as possible , Enough of PPT giri , The government should fund these program even if the result end up being less than optimum


Return to “Technology & Economic Forum”

Who is online

Users browsing this forum: No registered users and 9 guests